The Proceedings of the 5th Asia-Pacific Drying Conference

Preface.

Contents.

International Advisory Panel.

Thermal dehydration processes are highly energy-intensive and are found in almost all industrial sectors, accounting for 10 to 20 per cent on national industrial energy consumption in developed countries. With escalating energy costs and need to mitigate environmental pollution due to emissions due to combustion of fossil fuels, it is increasingly important to develop innovative drying technologies. Furthermore, drying is also affects quality of the dried product due to physical and/or chemical transformations that may occur during the heat and mass transfer operation. With tens of thousands of products that are dried in hundreds of dryer types, it is a formidable task indeed to develop design and scale-up procedures of wide applicability. Attempts have been made over the past three decades to make fundamental and applied contributions to transport phenomena and material science aspects in drying of various forms of wet solids, pastes and liquids. This presentation will attempt to summarize the state-of-the-art as far as theoretical understanding of drying processes and provide examples of some new technologies being developed. Opportunities for challenging fundamental and modeling studies to enhance drying technologies will be identified. Illustrative results will be presented to show how mathematical modeling of spray, pulse combustion, spouted bed and heat pump dryers can be utilized to develop new innovative conceptual designs.

In this paper, three major aspects of food powders in context to spray drying are discussed. Practical problems involved during spray drying which may greatly influence the product quality are the first issue. The second issue is to identify how the accurate drying kinetics model can form a useful tool in order to predict changes in physical and biological quality aspects and the microstructure during processing. Dryer-wide simulations with accurate drying kinetics plus quality kinetics can significantly reduce a number of experimental trials for optimizing the process. So far, such a success has still been restricted to production runs with much less throughputs as in commercial operations. Finally, the superior functionality of the spray-dried food product needs to be established more scientifically which can help commercial operations to achieve high quality reconstitution.

Spray drying is commonly used as a dehydration technique in pharmaceutical industry for making powdery products directly from liquid. It is also an attractive alternative for obtaining solid pharmaceutical molecules that are traditionally produced by freeze drying. Spray drying is often regarded as a 'harsh' drying method, due to the high temperature of the drying gas. Therefore, some adjuvants were added to improve the stability in manufacturing process and storage. Emphasis was placed on the encapsulation of proteins by spray drying and crystal transformation method.

A fractal pore network model for unsteady drying process of a natural porous body is developed by applying knowledge on fractal geometry, physics of flow through porous media, and transportprocess principle, which takes various factors, such as liquid-phase flow, vapor-phase diffusion, temperature gradient, and pore microstructure characteristic, into consideration. The drying dynamics character of potato slices, as an example of a real porous body, is obtained by the simulations of both a fractal pore network model and a regular one. The simulation results indicate that the drying kinetics, as well as the distributions of moisture and temperature inside the porous body, from the fractal pore network model are more consistent with that from the drying experiment than that from the regular one. The wet patch appears during the simulation process and this similar contour is also observed on the potato slices in the experiments. The throat size distribution in pore network of the porous media affects the drying process dramatically during the simulations.

This article focuses on atmospheric freeze drying (AFD) with heat pumps for drying of biological materials; a methodical approach for technological design and new possibilities in applications for drying of food products and biological materials to be stored in biobanks.

A new design of a combined continuous fluid bed with heat pump has been industrialized for the first time in Hungary for atmospheric freeze drying of corn and peas. The heat and mass transfer in a fluid bed dryer is very good because the drying agent is in contact with each unit of the product. The plant is using a stepwise drying with initial drying below the freezing point of the product and a final drying at temperatures above the freezing point of the product. In this way the product quality can be controlled to fit market demands. This paper present a methodical approach for the design of such a drying process developing phase diagrams for the products to be dried; essential for the choice of drying temperatures in such a stepwise drying. The paper also presents result on quality and physical parameters of different food products dried at different atmospheric freeze drying conditions.

The use of biobanks for storage of blood and samples from fresh and sick tissue for medical purposes is accelerating in the world. Atmospheric freeze drying with heat pumps has been used for drying of materials to be stored in biobanks. Drying tests has been executed to study the possibilities of atmospheric freeze drying as an alternative technology to storage in liquid nitrogen which is a very expensive technology used today for this purpose. Drying tests have been executed on rat liver to study the degradation of DNA and RNA. DNA was not degraded during drying. RNA, a more sensible component, also showed very little degradation during drying.

This study analyzed convective drying of wastewater sludge cakes with three-dimensional cake structures probed using an X-ray micro-computerized tomography scanner (micro-CT), considering the development of cracks and cake morphology. The presence of artificial cracks on cake surface assist drying, but those occurred naturally cannot. The cake surface is noted far from saturation over drying. Moreover, the cracks transport easily moisture to cake surface, hence yielding high surface humidity (and rates) for drying. Comprehensive drying model has to incorporate real boundary conditions for success modeling.

Osmotic drying describes the simultaneous transient moisture loss and solids gain in foods when immersed in a well mixed osmotic solution and results only in partial drying. Osmotic drying has been generally credited with considerable energy savings since the moisture is removed by a liquid diffusion process unlike the conventional drying which is controlled by the vapor diffusion process. More importantly, osmotic treatment offers quality advantages to the final product providing a more desired blend of sugars and acids thereby reducing the tartness resulting from concentration of acids in many conventionally dried fruits. The finished product would also be more bulky and less brittle/hard than their conventional counterparts. Modeling of the mass transfer phenomenon helps to optimize osmotic dehydration processes to have high product quality. Because of the simultaneous moisture loss and solids gain in test samples, gathering and treatment of data during osmotic drying is more complex than in conventional drying. Osmotic drying in batch mode has been well studied with limited industrial applications in the continuous flow systems to take advantage of process automation. Several techniques such as the use of microwave (MW) heating, vacuum, high pressure, pulsed electric field, sonication, etc. have been employed before, during as well as after osmotic treatment to enhance the performance of osmotic dehydration and to improve the quality of the resulting product. This presentation will give an overview of osmotic drying concepts that are employed to improve the drying rate and product quality.

Drying is perhaps the oldest, the most common and diverse of chemical engineering unit operations. Drying is becoming of more concern in almost all industrial sectors including Fine Chemicals, Bulk chemicals, Pharmaceutical, Food and Biotechnology. Most of the biomolecules and food products are stable in a dried form. In most of the chemical industries, hot air tray dryers are traditionally used for drying of cake like materials, which most of the times results in uneven drying (because of improper distributions of air), high drying times, large amount of energy loss giving unsatisfactory output. Most of the Food dehydration industries also rely on convective drying resulting in poor product quality. To overcome such problems, there should be process improvements in the field of drying. This paper deals with different case studies, involving development of new processes as well as improvement of few existing industrial processes.

In pharmaceutical freeze-drying processes, the freezing step is a key-step because it fixes the morphology of the frozen material and, by the way, the final morphology of the freeze-dried material. It is the most difficult step to control due to the stochastic nature of nucleation processus and, besides, it could be a damaging step with respect to the biological activity loss of pharmaceutical proteins. In this review, we have analyzed published experimental data on ice morphology and sublimation rates obtained with some standard formulations used to stabilize pharmaceutical proteins during freeze-drying.

Firstly, we analyzed data on ice crystals size morphology obtained by direct optical microscopy in cold chamber for different vial configurations and freezing parameters, namely: type of vials (moulded or tubing), height of filling, vial size, shelf loading temperature. It proved that the ice crystals sizes distributions depended not only on the freezing rates (well known result) but also on the vial size and type and also on the filling height. This behaviour was explained by the decrease of the super cooling effects which generally led to large and non homogenous ice crystals sizes distributions. Moreover, it was confirmed that adequate annealing treatments could homogenize and increase notably the mean ice crystals sizes.

Secondly, an ultrasound system has been designed and investigated to control the ice nucleation in vial configurations for standard formulations (mannitol, BSA, sucrose). It proved that during super cooling, the nucleation temperatures of the sample could be controlled at selected and predetermined values. It was experimentally confirmed that the primary drying rates during freeze-drying were accelerated due to significant homogenization of the ice morphology by the ultrasound controlled nucleation.

The increased importance of freeze drying witnesses a worldwide interest of research. A growing body of literature has demonstrated that the scientific approach can result in improved product quality with minimum trial and errors. Formulation and process development need a systematic understanding of the physical chemistry of freezing and freeze drying, the material science and the mechanisms of heat and mass transfers. This paper presents a brief review on freeze drying of aqueous solutions based on publications in the past few decades, and discusses the issues of the process towards readers in need of future research and application.

The classification of materials with nanostructure and the methods of nanoparticles synthesis are presented. There is considered the scientific foundations of creation of nanoporous solid materials, nanoparticles and nanofilms by liquid-phase condensation using sol-gel technology or by fluid atomization. The main theoretical and experimental research concerns supercritical, conventional, super high frequency, spray and freeze-spray types of drying. The approaches based on nonequilibrium thermodynamics and the heterogeneous media mechanics have been used for the mathematical description of structure formation process of nanoporous materials. The proposed approach allows to combine physical-chemical phenomena and structure formation for production of aerogels and xerogels (nanostructured films and nanoparticles). The recommendations have been done to reduce drying stress in nanomaterials. The innovative equipment for production of ultradispersed and nanodispersed powders such as super high frequency dryer, spray dryer with ultrasonic nozzle or electric atomization and freeze dryer with active hydrodynamics is presented.

The thermal evaporation of moisture is an essential part of many industrial processes. Drying innovation has until the later stages of the 20^th century tended to fall short of the efficiency gains which were credited to other process functions. Nowadays however, the decision on which drying technology is best suited to a particular application will be a consideration of a more diverse range of factors compared to 20 years ago. Dryer owners and operators are under increasing pressure to ensure that they aspire to higher standards of environmental compliance, energy efficiency, operational safety and product quality. It is difficult to dispute that any of these, singularly or collectively, provide more than substantial motivation to engage in meaningful Research & Development – the success ultimately being measured by the attainment of regulatory compliance and operational efficiencies. However, meaningful Research & Development is unlikely to occur in isolation and if it did the chances of success would be minimal. The innovation model which encapsulates the need, vision, financial and intellectual input, as well as the practical Research & Development, academic and commercialisation resource's, is a demanding and dynamic partnership. We share a clear responsibility in ensuring that we resource our teams and individuals to openly embrace and contribute in the development of multi-disciplined partnerships and collaborations needed to support continued innovations in Drying. In support of this presentation I will draw from refer to our recent experiences in drying development, in particular the global commercialisation of Super Heated Steam Drying.

This paper presents an experimental study on preparation of gram-negative bacteria microcapsules by spray drying. Effects of operating conditions on the bacteria survival rate were examined by single factor analysis. Through orthogonal experiment, appropriate conditions were determined as 160°C of the inlet air temperature, 12.5 ml/min of the feed flow rate, 1:9 of the ratio of gum arabic to maltodextrin and 50 ml for fluid nutrient medium with the bacteria. The bacteria survival rate reaches 84.57 %. Examination of storage performance shows that quantity of the viable gram-negative bacteria was increased by 148 % after preserving in plastic film bag for 6 months under ambient temperature from 18°C to 30°C, viability of the bacteria were improved compared to those inoculated from laboratory.

In this paper, the effect of different factors on Torbed puffing chestnut were researched. Results showed that cassava starch had the largest effect on chestnut puffing property. The results of single factor showed that the optimum aging time was among 20 to 24h, the feasible moisture content of the rough slice was 10%-12%.The optimum processing parameters were: chestnut powder: cassava starch=1:2, thickness 0.60mm, puffing temperature 280°C, aging time 20h~24h, and moisture 10%~12%.

Experimental investigations on the heat transfer characteristics of oscillating-flow heat pipe with acoustic cavitation in comparison with the ordinary oscillating-flow heat pipe were given in this paper. The experimental results show that the heat transfer rate of oscillating-flowed heat pipe with an acoustic cavitation field imposed on the evaporator section is higher than that without cavitation field by 8%~25%. It has been proved that acoustic cavitation can enhance the heat transfer performance of oscillating-flow heat pipe. However, for the case of acoustic cavitation applied on the condenser section, it is not always effective for heat transfer enhancement, the heat transfer rate increased from -39% to 77%.

Experiments were performed on a closed loop self-exciting mode oscillating flow heat pipe (SEMOS HP) with uniform and non-uniform structures under the same test conditions using an electric heating plate as heat source. The heat transfer characteristics are analyzed by comparing the temperature of wall of the heat pipe and output power when the heat input of the electric heating board and heating position changed. The result shows that the heat transfer rate could be improved by using a non-SEMOS HP with uniform structure under low or middle heat input, and it gives the highest heat transfer performance when the non-uniform diameter section is at the bottom of the heat pipe and the heating source located below the non-uniform section.

In this paper, different types of fractal structures are generated to model the structures of nature porous media, an appropriate mathematical model is established for the heat conduction in fractal porous media, and the influence of various factors on the effective thermal conductivity of solid and fluid are analysed in detail, the relation between the characteristic size of the artificial fractal structures and the natural porous media is analysed. A lattice Boltzman model is developed to simulate fluid flow in fractal porous media. The results indicate that the flow field structures in fractal porous media exhibit fractal characteristics, the volume flow rate is proportional to the pressure drop, the relation of volume flow rate with porosity conforms to an exponential function.

Electro-dewatering (EDW), enhancing conventional pressure filtration by applying an electric field, is an emerging technology potential to improve dewatering efficiency especially for sludge, whereas the power consumption limits its application in industries. In a traditional electro-dewatering process, the water removed by electro-osmosis is separated from the cathode or filter cloth by gravity, which needs higher voltage to collect more water and consumes more power. In addition, the remaining water in sludge or filter cloth can't be removed easily and thus reduces the water removal efficiency. In this paper, a method is proposed to use porous material to adsorb the moisture near the cathode instead of gravity separation. The adsorptive material is soft and bibulous, and easy to regenerate by pressure. Due to adsorptive material applied in EDW process, much more water from the sludge can be easily separated and removed; meanwhile, the current through sludge is depressed and makes the power consumption decreased too. The experiments show that, when voltages of 10V, 20V and 30V were applied to decrease the water content of sludge from 77% to 70% w/w in EDW using adsorptive material, the power consumption was respectively 25kWH/t, 41kWH/t and 53kWH/t, and the processing times were 4.5min, 1.5min and 0.8min respectively.

Kenaf fibers are produced from the kenaf plant at a fiber yield of up to 25% by weight of the plant. Kenaf fibers have been used as industrial fibers in various industries such as in the fiber board, paper, mattress and cushion, thermoplastic composites and animal feed meal industries. Rotary drum and belt dryers with diesel fired flue gas drying medium have been conventionally used to dry kenaf fibers. However this drying medium tends to produce discolored fiber. In addition the high cost of diesel may render the cost of kenaf processing uneconomic. To overcome the discoloration problem, the present work uses superheated steam to dry kenaf fiber. If excess steam is readily available in the kenaf factory than its use in the kenaf dryer reduces the drying cost further. The initial fiber moisture content is in the range of 2.0 to 3.0 dry basis. The drying experiments were carried out at atmospheric pressure, temperatures in the range of 110 to 170°C and steam superficial velocity of 0.50 m s^-1. The change in mass of kenaf fiber during the drying process was periodically measured using an analytical balance connected directly to the wire mesh plate when the steam was diverted momentarily. The drying rate is faster at higher steam temperature. The drying rate initially increases to a maximum and then falls off exponentially thereafter. The drying kinetic data were fitted to Tan and Cenkowski's and Hasibuan and Daud's models for steam drying. Tan and Cenkowski's model fits the experimental data better with a lower mean residual squares than the Hasibuan and Daud's model. The superheated steam through drying system can successfully reduce the moisture content by almost 100 % in 15 minutes without steam condensation during the drying process.

The present work proposed the two-stage drying technique concerning on the drying of shrimp using superheated steam dryer followed by heat pump dryer (SSD/HPD) at different drying conditions. The effects of drying temperatures and intermediate moisture contents (IMC) on drying characteristics and dried product quality were investigated. Shrinkage, color and texture of dried shrimp were determined. The experiments were carried out in the two stages of SSD/HPD. The first-stage superheated steam drying was performed at the drying temperatures of 160°C and 180°C while the second-stage heat pump drying was operated at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage (IMC) was varied between 30% and 40% (w.b.). For the comparison, purely SSD (superheated steam drying for the whole drying process) was also performed at the same drying steam temperature as used in the first-stage SSD. As for the effects of drying conditions, the results showed that higher drying steam temperature and higher IMC yielded better product quality only in terms of color. In addition, it was found that SSD/HPD dried shrimp had much lower degree of shrinkage, better color, softer and less tough than purely SSD dried shrimp.

Deformation is a phenomenon that is common during drying of foods and other bio-products. Recently, attempts have been made to describe deformation of a food product using an indicator calculated either from the external changes of the sample or from the microstructural changes of the sample. In the former case, a shape factor is calculated from the surface area (external changes) of the drying product while in the latter case, the fractal dimension is calculated from the images of the microstructure of the product. Since external changes are much easier to evaluate, it is interesting to determine how the indicator calculated from the external changes compares with that calculated from the microstructural changes. In this work, a comparison was made between the two methods of describing product deformation during drying. Carrot was used as a model material undergoing a representative drying method viz. low-pressure superheated steam drying (LPSSD).

The aims of this study were to investigate a novel strategy for drying longan without stone viz. the two-stage drying using a superheated steam dryer followed by a hot air dryer (SSD/HAD), both from heat/mass transfer and product quality points of view. The experiments were performed in the two different stages of SSD/HAD using the superheated steam temperatures of 120-180°C in the first-stage and then the drying air temperatures of 60-70°C in the second-stage. The moisture content of longan at the end of the superheated steam drying stage was 200% dry basis. The effects of drying medium temperatures and the intermediate moisture content of dried longan after SSD/HAD on the drying kinetics and quality of dried longan were investigated. The quality of longan was evaluated in terms of its color characteristics and shrinkage.

The diffusion model including shrinkage has been developed for predicting the change of moisture content in banana foam mats during drying. The moving boundary using variable grid and the immobilizing boundary using an alternative frame of reference were used in exploring their capabilities to predict the moisture change. The moisture content of banana foam mats at three foam densities of 0.3, 0.5 and 0.7 g/ml dried at three temperatures of 60, 70 and 80°C and at a superficial air velocity of 0.5 m/s were monitored and validated with the proposed model. The qualities of the final product i.e. texture and microstructure were also investigated. The moving boundary method can predict the average moisture content more accurate than the immobilizing boundary method especially in the case of low density banana foam. The quality determinations have shown that the foam density significantly affected hardness, crispness and morphology of dried banana foam whilst the drying temperature did not influence on those qualities.

Vast reserves of brown coal exist in Australia. However, the high moisture contents of these brown coals pose challenges for existing and potential users. An obvious solution is to remove the moisture by drying. A drying technique that is currently receiving increased focus is superheated steam drying which, relative to conventional air drying techniques, provides a number of significant advantages including increased efficiency, reduced fire or explosion risks, faster drying rates and no particulate or odorous emissions. In the current paper, the drying of brown coal in a pilot scale superheated steam rotary dryer developed by Keith Engineering is investigated. It is illustrated that the dryer is able to significantly reduce the moisture content of Australian brown coals, with moisture reductions of up to ninety per cent achievable. Through a statistically designed series of tests, the parameters affecting the drying performance are investigated. It is demonstrated that the final moisture content is particularly dependent on the steam temperature and coal feed rate while the drum rotational rate has a less significant effect.

A four-section pulsed-fluid bed (PFB) apparatus with a 0.18 m² cross section area was used to investigate the influence of pulsed-fluidization variables on the drying process of molecular sieves, a test material that was chosen for it presents an initial constant drying rate period. A two-level factorial design was developed to evaluate the influences of the inlet gas temperature (40 °C and 70 °C), the frequency of pulsation (250 rpm and 900 rpm) and the airflow rate (500 Nm³/h and 600 Nm³/h) on the drying rate. Results showed that all the investigated variables affect the drying rate somehow.

The hygroscopic porous particle was used as the fluidizing particle for the superheated steam fluidized bed drying under reduced pressure. A relatively large material was immersed in the fluidized bed as the drying sample. The drying characteristics of the sample were examined experimentally and the results were compared with those in the case of inert particle fluidized bed.

The drying finished much earlier in cases with fluidizing particles than in the case without them. The water transfer from the sample to the fluidizing particle bed in the case of hygroscopic porous particle facilitated the drying regardless of pressure and temperature in the drying chamber.

X-ray microtomography coupled with image analysis was used to characterize the 3D microstructure of dried banana slices. This non destructive imaging technique allowed determination of the total porosity and the pore size distribution of entire sample slices dried with different drying techniques and drying conditions. The influences of the drying methods (low-pressure superheated steam drying, vacuum drying, combination of far-infrared radiation with these two techniques) and of the drying temperature were assessed. The results showed that the total porosity and the pore size distribution depend on both the drying technique and the drying temperature. Far-infrared radiation was found to modify the texture of the dried bananas by increasing their final porosity.

A conceptual 'food-kansei' model (Ikeda et al., 2004) has been applied to optimize operating conditions of a superheated steam oven prototyped for final food products. Fifteen raw beef samples were heated at the oven temperature of 200-300°C and at the steam injection rate of 3-9kg/h to measure the viscoelastic properties of the roasted samples. Sensory evaluation was also carried out to acquire hedonic scores and several factors influencing total palatability. Taste, texture and flavor were statistically significant for average hedonic scores of the samples at one percent level, and juiciness for average texture scores. The optimum operating condition of the oven to maximize juiciness of the samples was found to be 245°C in the oven temperature and 3.5kg/h in the steam injection rate under our experimental conditions.

Characteristic roasting and thawing-roasting curves have been presented for raw and frozen beef samples during superheated steam heating. A prototype superheated steam oven was manufactured to measure the changes in sample weight, temperature distribution within a sample under the regulated operating conditions of oven temperature, flow rate of the steam injection, and the ratio of the residual weight of the samples to the initial, respectively. The quality of a final product was evaluated by its moisture content, surface color, viscoelasticity and hedonic ratings by a sensory evaluation. The constant rate period was not appeared in the characteristic drying curves, and the drying rate was found to be controllable by oven temperature and steam injection rate. The thawing-roasting time was half shortened comparing with that by conventional radiant heating.

In this study, Computational Fluid Dynamic simulations were carried out to analyze the cold airflow, hot liquid droplet dynamics, their interaction and heat transfer in a spray chamber to enhance production capacity, eliminate chamber choking near exit and obtain desired particle size. The spray chamber has a 70°C hot fatty acid liquid (made of 80% palmitic acid and 20% stearic acid) sprayed by a centrifugal atomizer and cold air stream of 3.8°C delivered into the chamber via a spiral converging duct and a set of conical dispersers. Both the atomizer and the disperser are located on the roof of the chamber and thus form a co-current flow system. A total of 9 cases, divided into 3 groups, were simulated. Group 1 (cases 1-2) focused on the current capacity (1,150 kg/hr hot liquid spray) aimed to study the airflow and droplet dynamics and to verify the CFD simulations. The results were compared with analytical data and operational plant data. Group 2 (case 3-6) focused on the proposed high capacity (2,300 kg/hr hot liquid spray) with some minor modifications to the conical disperser. The aim is to seek airflow characteristics for optimization of the flow and particle residence time. Group 3 (case 7-9) focused on radical modifications of the chamber by attaching additional tangential entry ducts to the spray chamber to solve operational problems. Although this work does not involve mass transfer, the overall aerodynamics and heat transfer characteristics as well as particle trajectory calculations are relevant to industrial spray dryer modeling as well.

One of the major problems in spray drying is the control of the product particle size distribution since it is very important in many industries. The objective of this work is to study the effects of atomizer rotational speed on the product size distribution. In order to obtain the particle size distribution of the required product, a special design of the atomizer disk is used in this study. The particle size distribution under different atomizer rotating speeds are measured and presented in this paper.

The movement-states of particles and the dynamic properties of the flowing gas field in spray dryer were discussed and their mathematical model was established. The mass and heat transfer process between particles and drying medium based on the transfer theory were calculated with Marshall-Equation. By solving the dynamic equation of the moving particles, the design of the spray dryer and the development of computer program for design were achieved. The reliability of the program was verified with experimental results.

In this experimental study, the effect of wall surface properties on the deposition problem was investigated. Properties considered in classifying different wall materials are surface energy, roughness and dielectric property (Teflon and Stainless Steel). The model solution used contains sucrose representing low molecular weight sugar commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produces higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) exhibits disadvantage on the deposition of dry particles.

Konjac powder, or glucomannan, is widely used in the food industries as a food ingredient, binding, gelling or thickening agent. Glucomannan is dietary fiber which contains low calories and is often incorporated in health food. Therefore there is an increase in popularity of glucomannan food ingredient for people concerned with weight problems. However the method of extracting glucomannan from konjac is still costly, time consuming and it involves chemical processing. This study is aimed at developing a fast process of extraction with the combination of wet extraction process and spray drying to produce high quality glucomannan. The effect of inlet air temperature (140 °-200 °C) on overall qualities of glucomannan is investigated. The results show that the yield of glucomannan, viscosity and particle size are increased when the inlet air temperature is decreased. The whiteness of the powder is decreased when increasing the inlet air temperature. The information obtained here will be of benefit in further optimization of the extraction process of glucomannan.

The effect of temperatures, feed flow, additive concentrations were studied on the residual enzyme activity, water activity and drying time of α-amylase. This was followed by Response surface methodology to understand the effect of interactions among the significant variables. Response Surface Method (RSM) Design Expert 7.0.2 software was used to analyze the data. The effect of salts on residual enzyme activity was also studied. The optimum salt concentration with respect to enzyme activity and flowability was determined. The X-ray diffraction analysis of the spray-dried enzyme was done to ascertain the nature of amorphous powder.

Atomization is carried out for range of applications such as spray drying, absorption, spray coatings, crop spraying and formation of mist for certain chemical reactions and applications. The liquid in the form of thin film when allowed to flow on a vibrating surface (frequency> 20 kHz) breaks up into fine droplets. This phenomenon is known as ultrasonic atomization. The droplet size, in the case of ultrasonic atomization, depends upon the ultrasonic parameters such as frequency and intensity, operating parameters such as liquid flow rate and physiochemical properties such as density, viscosity, surface tension and vapour pressure of the liquid.

To study the spray drying operation to obtain desired particle size distribution assisted by ultrasonic atomization, a laboratory level experimental setup has been used which gives good performance and allows us to evaluate the effect of operating parameters.

The basic advantages of ultrasonic atomization over the conventional two fluid (air pressure) or spinning disc atomization used in the conventional spray dryer is the reduced (by an order of magnitude) drying chamber size due to the relatively uniform and low momentum drops produced by ultrasonic atomization. This results into more uniform drying characteristics and relatively narrower particle size distribution. The system is developed to obtain tailor made particle size.

The solute material was dissolved in the solvent to a known concentration. The concentration of the solute in the solvent decides the particle size and can be estimated by doing material balance on a single drop produced by ultrasonic atomization.

The particles obtained after drying were characterized in terms of particle size distribution and morphology.

During spray drying, agglomerates of powder particles are formed, which determine the instant properties of the powder. Between 2001 and 2004 a large international research and technological development project was carried out with the aim of developing an industrially validated (computer) model, using CFD technology, to predict agglomeration processes in spray drying machines. Stickiness of the powder particles is an essential input parameter for the model. In this paper we, therefore, pay special attention to stickiness measurements. A recently developed new method to measure dynamic sticky-points is introduced. Experimental results are shown and compared to the results of static and dynamic stickiness tests using conventional approaches.

Simulations of crystallisation behaviour in a spray dryer have been performed using a model developed by previous workers applied to a Buchi-290 laboratory scale drier. This simulation provided information on the material properties, such as glass transition changes during the drying process. The potential crystallisation behaviour has been modeled using Williams-Landel-Ferry kinetics. Explorations the model have suggested that the air inlet temperature is an important variable affecting crystallisation in the dryer. The explorations provided drying conditions that permitted reasonable drying while controlling the degree of crystallisation. These conditions were examined and tested experimentally, also showing that the apparent degree of crystallinity was affected by the inlet air temperature.

Whey proteins concentrate (WPC) powder, which is an important protein source for human, is commonly produced from whey using a spray drying technique. It is important to predict several drying parameters and also parameters which govern the quality of the product before conducting real operations. Drying kinetics is an essential tool for predicting the drying rate and various parameters which are rate-dependent. There have been only little studies published previously on both modelling WPC drying and dryer wide simulations using different computational tools. In this paper, the application of a reaction engineering approach (REA) to modelling a droplet drying process is reviewed. Results based on dryer wide simulations using a reaction engineering approach are presented. Most importantly, a sensitivity analysis of the reaction engineering approach using drying of WPC and skim milk droplets is reported. This analysis will be helpful to select an appropriate drying kinetics model and to have a benchmark for the future WPC drying modelling work.

Recent advances in spraying and atomization technologies exercised in various fields have shown that a spray with narrower drop-size distribution, or even a monodisperse spray, may be advantageous in many ways. Monodisperse droplets with controlled trajectory, highly spherical shape and micron sizes were reported to be generated by several droplet generators. Majority of the existing droplet generators, however, deal with very low feed flow-rates. In this work, a few commonly used monodisperse droplet generators are presented in order to assess a possibility of producing monodisperse sprays of high volumes and using them in commercial spray drying operations. This review paper is also aiming to discuss working principles, advantages and limitations of commonly used droplet generators in other fields.

The technique of in-chamber blending in practice has been investigated, by altering the configuration of a Buchi B290 small-scale spray dryer having a two-fluid nozzle, through adding extra pipes (long and short) into the chamber to feed dry particles in order to increase the particle numbers per unit volume. Experiments were performed whereby long or short pipes were used to estimate the shift in the particle size distribution due to differing amounts of agglomeration. Maltodextrin (DE18) particles were fed into the chamber with 20% salt solution sprayed through the atomizer. The longer pipe allowed higher particle concentrations near the atomizer, and therefore more agglomeration than the short pipe configuration, which gave lower number concentrations. On average, one salt droplet collided with an average of 5.5 maltodextrin particles for the short-pipe configuration and 4.1 maltodextrin particles for the long-pipe configuration. There was also a significantly greater shift in cumulative particle sizes for the long pipe configuration (2.7% in mean size) compared with the short pipe case (2.1%).

This work has determined the magnitude of re-entrainment and established the operational parameters that may be manipulated to influence re-entrainment of salt particles for a small-scale spray dryer (Buchi B-290). The wetness of the spray dryer wall deposits was found to significantly influence the magnitude of re-entrainment. It was shown both experimentally and numerically that wet deposits form at low nozzle air-to-liquid ratios (<2000), which form large droplets that dry slowly, while the initial droplet velocity did not have a large influence on wet deposition. Wet deposits form strong liquid and solid bridges, and thus deposits formed from wet particles were difficult to re-entrain. Less than 2% of deposits formed at nozzle air-to-liquid ratios less than 2000 were re-entrained, while 15.4% to 21.2% of dry deposited particles (formed at nozzle air-to-liquid ratios ranging from 2308 to 3409) were re-entrained.

The effects of temperature, relative humidity and molecular structure on the crystallization process within amorphous solids have been explored. Lactose and sucrose were spray dried, and the products were exposed to different and relative humidities. To investigate the effect of temperature, experiments were conducted at both room temperature and 40°C. The rate of the crystallization was more than doubled for every increase of temperature by 10°C, up to three times for the case of lactose. These results are consistent with the picture of the process as an activated rate one. The effect of increasing relative humidity (RH) was observed to increase the rate of crystallization up to a threshold value, after which the rate was no longer affected by relative humidity. This threshold was found to be 51% for sucrose, at room temperature, which was lowered to 32% at 40°C. Lactose and sucrose, which have the same molecular weight of 342 g/mol but different molecular structures and thus glass transition temperatures, were exposed to similar conditions. The difference in molecular structures had little effect on the overall rate of the crystallization process for the same material temperatures, in contrast with the predictions of the Williams Landel Ferry equation, which suggests that the rate of crystallization is a function of the difference between the material temperature and the glass transition temperature.

A pilot spray dryer with rotary atomizer is used to study the drying process of lime juice in experiment. A CFD simulation of drying is also presented. The thermophysical properties of lime juice are measured experimentally. The measurement includes assessment of heat conduction by Coaxial cylinder heat conductivity estimation device, specific heat by DSC calorimeter and density by volumetric pycnometer. In these measurements variation of properties with temperature and solid content was considered. These properties are needed to spray dryer modeling and define droplet properties. Spray drying analysis was done in axisymmetric conditions. The CFD simulation was done by commercial CFD software FLUENT 6.1 with discrete phase method in modeling two phase flow. By modeling droplets in spray dryer, the droplets distribution and their deposition on the chamber wall can be recognized. The most percent of evaporation occur at the constant rate period and there is not detectable change in diameter in falling rate period. Based on the results, increasing of the air inlet temperature causes an increase in drying rate therefore reducing of droplets diameter is occurred at lower time.

The release of d-limonene from a single spray-dried particle could be measured with CLSM through the change in fluorescence intensity of Nile red. Fluorescence change of Nile red indicated that d-limonene release from the spray-dried particle containing emulsified d-limonene occurred from the inner part of the spray-dried particle. The change in fluorescence intensity was similar to the d-limonene content in the spray-dried powder measured by gas chromatography. These results suggest that CLSM could possibly serve as a useful means for observation of flavor release behavior in spray-dried particles.

The influence of outlet air temperature on physicochemical properties of a cactus hydrosoluble extract was evaluated in a spray dryer. The juice was pressed out of fresh cladodes pieces of Opuntia ficus-indica, cut in squares of 4±0.5 cm², it was blended with water to 50% in weight in a pothole with agitation of 500 rpm and 80 °C for 20 minutes. The press was carried out in a screw without end with sieve of 2 mm. The recovered mucilage of the cladodes was centrifuged at speed 10200 rpm. The physicochemical properties of the cladodes hydrosoluble extract were: soluble solids 4.27±0.156 g, pH 4.53±0.015, density 1.02 g cm^-3 and viscosity of 650.12±5.149 cP. The analysis microbiology was negative for E. coli, coliforms and Salmonella. The juice was spray dried with a rotational disk (GEA NIRO model A/S Production minor) atomizer. The speed of disk was 30139 rpm. 175 °C of inlet air and outlet air respectively at three temperatures (80, 85 and 90 °C) were employed. For mixing encapsulation, (Glas-Col®) PRECISION STIRRER was used at 2000 rpm for 20 minutes. The mixtures are of: GA-MD: gum arabic with maltodextrin (1:1), GA-PSL: gum arabic with whey protein (1:1), PSL-MD: whey protein with maltodextrin (1:1), to two concentrations of 0.5% and 1.0% regarding the weight of the extract. The extract without encapsulates was used as the control. The moisture content in the powder was from 6.19 to 8.42%, density of 0.31 to 0.44 g/cm³, hygroscopicity of 0.06 to 0.18 g of water per g of powder in 85% of relative humidity for 90 minutes, pH of 5.09 in contrast to the value of 5.23 in the extract, particle size of the powder ranged from 4.76 to 8.46 μm, bigger than that obtained in the extract, 1.86±0.8818 μm. The triplicate measures were made in stable atmosphere at 23 °C ±3 and relative humidity of 40% ±5. The reconstituted product showed a slight change in pH, particle size and viscosity with regard to the natural extract. A significant effect of the increase in the outlet temperature on moisture content and particle size was observed.

Air-blast atomizers in which a thin liquid sheet is shredded to droplets under the action of a high-speed airflow are extensively used in industry production. Primary atomization in these devices is a consequence of air-drag-force and liquid surface tenson. To better understand this process, an integrated atomization model of a annular liquid sheet is proposed. The atomization mechanism of the model is based on the equilibrium of force experienced by the sheet, rather than surface wave stability analysis. Assisted by a flow simulation program the model is allowing to describe the formation of the sheet, the alteration of the sheet thickness in the direction of its spreading as well as to determine the mean diameter after the break-up of the sheet. Model predictions compare favorably with experimental data and with calculations by the general LISA model.

The paper describes a method for the determination of drying kinetics in a small-scale tunnel which could be confidently applied in CFD models for scalling-up of spray drying process. Critical moisture contents as a function of evaporation rate were determined in small scale tunnel. Results of CFD modelling shown that drying kinetics obtained from small-scale tunnel could be properly applied to scale-up spray drying process.

Extensive tests were carried out on the quality related properties, such as, flavor, appearance, texture and nutritional values of mango and rockmelon samples dried under normal air heat pump dryer (HPD), modified atmosphere heat pump dryer (MAHPD) using N₂ and CO₂, and also vacuum and freeze dryers. For mangoes and rockmelons, the MAHPD dried samples show better flavor than HPD dried samples. The freeze and vacuum dried samples are considered even better than MAHPD dried samples, although at a much higher costs. For MAHPD, N₂ drying leads to a better color retention than CO₂ drying. The HPD dried samples show a higher value of textural hardness than MAHPD samples, whereas the freeze dried samples show the lowest textural hardness. Freeze drying leads to the best vitamin C retention, followed by vacuum, MAHPD and HPD drying. In the case of MAHPD, the CO₂ drying shows slightly higher retention of vitamin C than N₂.

A new hollow blade dryer for municipal sludge thermal drying is introduced with focuses on the principle of operation, the technological process and the design calculation of lectotype. Taking the original sludge with water ratio 74% from some sewage plant in Shijiazhuang to do experiment, the heat utilization efficiency of the hollow blade dryer with drying area 2.4 m² reaches 85%~95%. A practical example is used to demonstrate the lectotype calculation and the applicability of the hollow blade dryer.

Microwave-vacuum (MV) drying characteristic of plantation Masson Pine were studied experimentally for various levels of microwave radiation time, initial moisture content (MC) and wood thickness. The results show that the process of MV drying for wood can be significantly divided into a short accelerating rate drying period, a long constant rate drying period and falling rate drying period, and the second drying period can extend to levels of mean moisture content below the fiber saturation point; With the increase of initial MC and microwave radiation time, the drying rate of wood increases significantly; Within the range of 2cm to 6cm, the effects of sample thickness on the drying rate can be negligible.

Based on the mechanism of moisture and heat transfer in wood during microwave-vacuum drying (MVD), a one-dimensional mathematical model to describe the process of wood MVD was established and verified by experiments in this research. The results showed that the process of MVD of wood experienced three distinct periods: (1) accelerating rate with rapid warming-up drying period, (2) a constant temperature and constant rate drying period, and (3) a heating-up with falling rate drying period; The predicted temperature and moisture content in wood match well with the experimental data, the square of the relevant coefficient of the values of simulation and test is above 0.9, and the simulation precision of the change rule of the moisture is higher than that of the temperature.

Drying kinetics of China maize dried in a laboratory scale vacuum dryer was studied. The effect of drying temperature, vacuum degree, bed height and initial moisture on maize cracking and germination rate was presented. Characteristic drying rate curves exhibited mainly falling rate period, with an induction periodic, but without the constant rate period. A custom-made light box was built to visually analyze the cracking on the surface of maize. Maize cracking was lower than 10% just after drying at 50°C-90°C. But the cracking at all temperature was higher after drying for 24h. The germination rate reduced with drying temperature increasing. The initial drying rate (induction period drying rate) at higher vacuum degree was higher, but the vacuum degree did not significantly affect the falling rate period. The total drying time and total drying rate almost was the same at different vacuum degree of the same temperature. Vacuum degree also did not significantly affect the cracking percent and germination rate. The cracking and germination rate of initial moisture 25% were better than the initial moisture 37% after vacuum drying. The bed height has little effect on cracking.

This article will give a brief introduction on the structure of a new type solar drying device. We can calculate the radiation intensity which is on the heat-collecting device according to the principle of using the heat of solar energy. We can also learn the effective acreage of the heat-collecting device from the experienced formula. And it'll be easy to know the most proper acreage which will be assigned to every kilogram of medlar by surveying.

The sludge drying with heat pump test dryer was experimental studied in this paper. Through the tendency of Moisture Content (MC), air temperature and relative humidity changing, the drying rate, dewatering efficiency of heat-pump, and energy recycling rate were analyzed for the minitype heat-pump dryer system. The results showed that it was evident of the energy saving in heat pump sludge drying. The average energy recycling rate was 36.3% with MC from 46.8 % to 5.4 %. The energy recycling rate is 45.3%, 28.8% and 14.75% in initial stage (MC 46.8%~19%), medium stage (MC 19%~11%) and later stage (MC 11%~5.4%) correspondingly. The fastest drying stage is in constant drying period with MC between 30.4% to 18.7%, It is 56.5%, 12.8% and 23.4% faster than the preheating period (MC 46.8%~42.8%), accelerating period (MC 42.8%~30.4%) and decelerating period, respectively. Average drying rate rises with the temperature increasing and Relative Humidity decreasing in drying chamber.

In this study, super-conducting heat pump (SCHP) dryer and low-temperature drying of fuel were employed to dry the paddy with high moisture content, respectively. The paddy (w.b.) was about 30% initial moisture content and 1200kg each batch. After drying process, the final moisture content was 14%, and the average energy consumption of SCHP was 10.5kw·h/100kg (Based on the weight of final paddy). The total drying time, drying cost and energy consumption were 88%, 64% and 58% of those using low-temperature drying of fuel.

Heat pump with the natural refrigerant CO₂ is receiving more attention due to its good properties for environment and CFC substitution problem. In this study, the two-stage drying of CO₂ transctitical cycle heat pump is discussed. The drying system is designed based on the thermophysical properties and characteristics of CO₂. The single compression cycle single stage drying CO₂ heat pump dryer, the two-stage drying CO₂ heat pump dryers and electric drying system are compared. The analysis indicates that the efficiency of the two-stage drying CO₂ system can be higher than that of the single drying CO₂ system. The energy utilization rate of CO₂ heat pump dryer was higher than an electric dryer.

For the investigation of the internal moisture transfer mechanism of seed granule during the drying process of thin layer material, by numerical calculating with the method of finite difference, the internal moisture diffusion model was used to modeling the drying process of thin layer kidney bean seed. Result shows that the drying curves of modeling fit well with that of experiments; seed coat is the main mass transfer resistance in the drying process; the moisture diffusivity of the cotyledon layer is 3.2 times of that of the seed coat layer. If matching some internal temperature field distribution profiles with some internal moisture content field distribution profiles within seed granule, local moisture diffusivity could reach the maximum, accordingly the fastest drying process could be occurred, which might be considered as "limiting drying process".

Microwave radiation has the ability to induce the drying process from within a material. The microwave radiation can be used to generate the maximum volume of the heat in the materials. However, it is not always possible to achieve maximum drying rate when compared to conventional drying. Subsequently, the expected reduction in drying time is not always achievable. In the drying of biological products, drying temperature is normally limited to 60 °C, as product quality may suffers due to high temperatures and cracking. Past review shows that microwave drying suffer from low energy efficiency. This is because in most cases, the energy of microwave is constantly applied on the material. In cases where conventional drying process is applied with microwave drying, the stage at which microwave should be operated or switched off is not well understood. The intermittent drying process of microwave is found out to be an effective way of improving energy efficiency. Concurrently, this method does not suffer from the limitation of high drying temperature. This study investigated the effect of microwave power on the microwave drying of Red Color Pittaya. Investigation was undertaken using a small modified commercial microwave. Microwave power was varied in the range of 83.0 to 295.0 W. Moisture changes along with the drying efficiency were examined at different drying conditions. The dried product was analyzed to examine the quality such as color, structure and texture. The results showed that there is no significant effect from the changing of power and voltage to the final product color, shrinkage and hardness of red color pittaya.

Low temperature heated air drying (LTHAD) was investigated as a potential means for drying durian slices for improved longevity. Experimental investigations were conducted at 35°C, 40°C and 45°C and 80°C and 90°C for LTHAD and hot air drying respectively over a period of 24 hours. The drying kinetics and quality characteristics, including appearance of dried durian slices, of the dried samples have been evaluated. LTHAD samples are superior with respect to appearance than those obtained by hot air drying. Higher LTHAD temperatures reduce the time required to achieve the lowest percentage moisture composition.

Artocarpus heterophyllus is a Malaysian fruit, more commonly known as "jackfruit", which once picked has a relatively short storage life. This study investigates the feasibility of using low temperature heated air drying (LTHAD) at 35°C, 40°C and 45°C, relative to freeze drying at -30°C and -40°C and hot air drying at 100°C, for preserving fresh fruit and increasing jackfruit longevity. The drying kinetics and aesthetic quality of dried jackfruit is evaluated in relation to the fresh fruit. Freeze drying produces the highest aesthetic quality dried fruit, but LTHAD produces good aesthetic quality dried fruit in a more economical manner, better suited for economically less developed nations.

Dewatered cake was supplied into the air drying equipment which operated by air velocity of 80 m/sec, air rate 30m³/min and air temperature of 40Δ, and dried to produce the dried powder. The air drying equipment was composed of the air ejector which made high-speed fluid field, and cyclone which made circling fluid field. Dewatered cake was crushed at the high-speed zone as first step, and formed into dried powder of sphere shape by the collision between particles at the circling fluid zone. Wastewater sludge with water content of 82.5wt% was supplied 1.0kg/min into air drying equipment and produced the dried powder which had the water content of 62.3 wt% and mass median diameter of 2.4mm after process. At that time, it was analyzed that water removal rate was 0.1 H₂OΔkg/min. DS kg and air consumption was 170m³/DS kg. Under same experimental conditions, when waterworks sludge was dried, water content of dried powder decrease to 47.5wt% and mass median diameter decrease 2.1mm and water removal rate increase 0.13 H₂OΔkg/minDS kg. Air consumption increases 180m³/DS kg with comparison to the results of wastewater sludge. Therefore, this technology was evaluated that drying the dewatered cake of waterworks sludge was more efficient than wastewater sludge and also economical sludge handling technology due to drying the cake by only air.

The box-type heat pump dryer has been Investigated to figure out the amount of energy saving. The refrigerant used was R134a which is usually used in the common heat pump system. The drying material used in the study was shredded radish with uniform width and depth. The constant drying period could not be observed with shredded radish as expected in the typical farm products. The heat pump drying took 1.2 ~ 1.5 times longer than the hot-air drying. However, the heat pump dryer showed considerable improvement in energy saving. The SMER (Specific Moisture Extraction Rate) of the heat pump dryer was about three times higher than that of the hot-air dryer. The energy efficiency of the heat pump dryer was greater than 90% but that of the hot-air dryer was only in the range of 37 ~ 40%.

About 45% of the Canadian territory is woodland, and the wood industry accounts for 3% of the country's Gross Domestic Product, 10% of total foreign exchange, and 57% of the annual trade surplus. Canadian sawmills usually deliver 72 million m³ of softwood. About 85% of this production (white and black spruce, jack pine and balsam fir) is dried with bark boilers, 10% with fossil fuels (natural gas, propane or oil), and only 3% with low temperature heat pumps. Despite numerous attempts, the low temperature heat pump technology has not succeeded in securing a significant market share, the maximum operating temperature (50 – 55°C) being one of the reasons. However, in order to provide shorter drying times, softwood producers opt for drying at high temperatures (80 – 120°C). Advanced hybrid (electricity and fossil fuel) wood drying systems with high temperature heat pumps have been developed and field tested in the United States and Canada over the last six years. Several developments were achieved at the refrigerant flow control, dehumidifying rate and optimum drying schedule levels. This paper briefly presents energy calculations and overall operating parameters and performance, as well as the ecological aspects of high-temperature drying heat pumps. The study demonstrates that the thermodynamic efficiency and energetic performance of improved drying heat pumps reached designed targets, and that ecological impacts have to be carefully considered in the future.

Drying is a time-consuming, energy intensive and expensive process required in the most textile industries. The present study is part of a more general attempt to analyze convective drying of wool in order that a mathematical description of the overall process can be established. The main focus of this investigation is the development of a simplified mathematical model in a convective drying process of wool which can be used for prediction of drying characteristics.

An experimental dryer was developed for determining the moisture content of slab woods in variable drying times. Moisture contents were examined using different models. The drying data were fitted to the different semi-theoretical models such a Lewis, Page, new modified page, and Henderson and Pabis. Among the results obtained, the high level of correlation between the measured and calculated data justifies the new modified Page model.

Chemical heat pump (CHP) attracts attention as a high efficiency heat source having a heat storage function and a heat pump function. Chemical heat pump dryer (CHPD) using CaO/H₂O/Ca(OH)₂ reaction etc. is proposed by the authors as a novel green drying technology for the practical use. However, we still have some problems such as control of output temperature level in CHP to use a chemical reaction. A drying material changes the dry state by the temperature, the humidity and the velocity of drying air. Therefore a change of the output temperature level in CHP has to consider influence to give to drying material in CHPD. In this study, we performed simulations on the heat and mass transfer in CHPD corresponding to the drying experiments to analyze it theoretically. As a result, we clarified CHP drying by experiments and simulations on CHPD, and showed energy effective characteristics of CHPD.

The manchego and mallorquim cheeses are produced under controlled conditions and long time is needed to develop unique texture and flavor. This traditional manufacturing method has challenges to be addressed by new technologies. Tests were performed to verify feasibility of application of heat pump technology for cheese drying and ripening. The measured kinetic data was fitted by three models to quantify moisture removal rates. Analysis revealed that this modern technology fits well this application and that it promoted similar or higher removal rates than traditional methods. Moreover, the highly efficient heat pump thermodynamic cycle leads to added benefits related to energy, costs and environment.

Mathematical modeling and computer simulation of grain drying are the major emphasis of grain drying research in China Agricultural University. In this paper research on simulation of mixed flow grain dryers had been accomplished. Mathematical model of MFGD had been established. The developed software had been used in analysis, design and optimization of mixed flow grain dryers. Effect of air temperature, air flow rate, size and location of air duct on the drying rate and energy consumption was discussed and analyzed. Experimental research was carried out to validate the simulation results. Emphasis was put on the Influence of air duct size distribution and number of rows on the performance of mixed flow grain dryer.

A cooling process for fermentation liquor was modeled and simulated using the Computational Fluid Dynamics (CFD) method. The transient temperature distribution and steam function distribution of fermentation liquid in the tower were obtained from the CFD simulation. The calculated results for temperature field of the fermentation liquor were compared with those from the measuring values during a practical production process. The numerical investigation results revealed the hydrodynamic and energy conditions inside a fermentation jar, which provided a theoretical basis for temperature controlling of beer cooling fermentation process in beer brewery.

Vacuum microwave (VMW) drying of edamame in deep-bed was investigated to determine the effect of bed depth on drying parameters. Results show that there is a moisture gradient from the top to the bottom of the bed during vacuum microwave drying processing. Also, greater the depth of the bed, the greater is the moisture gradient over the depth of the bed, which affects moisture uniformity of the dried product.

In paddy drying process, the quick and accurate on-line moisture content measurement is necessary to promote the quality. A kind of on-line moisture metering technology and device for grain drying process was developed in this paper. The device design process, the dynamic signal acquiring and outputting and the calculation method of grain property moisture content were introduced. That was very helpful to promote detection accuracy. The reliability and practicality of the detecting technology and devices had been validated in different working conditions: the state of high temperature and high humidity in summer and the state of low temperature, high dust and wide moisture distribution range in winter.

A kind of self-adaptive control system for grain dryer was developed based on grain deep-bed drying process analytical theory and precise detection technology of high-moisture-content grain. It can change the system automatically to ensure the optimization of working condition according to real-time input-moisture-content and output status. The control system was reliable, stable, accurate and practical in production application.

In many drying processes of a multi-layer conveyor dryer, uneven air distribution in the drying chamber often results in the inefficient drying and irregular moisture content of the products. Thus, the condition of air distribution in the drying chamber of a multi-layer conveyor dryer is studied through both experimental and computational fluid dynamics (CFD) methods. The measurement of air velocity in the drying chamber of a six-layer conveyor dryer is conducted, and a three-dimensional CFD model for the dryer is established. The drying process for the air velocity measurement is numerically simulated, and the results are compared with those from the practical drying and measuring process.

In this paper, a method is proposed to preparation of redispersable emulsion powder used for building material. They include two main steps dealt with a core-shell emulsion polymerization and a spray drying. In the first step, AVE and MMA were used as seed emulsion and shell monomer in the core-shell emulsion polymerization. The effects of various factors on particle configuration of core-shell structure polymeric emulsion were investigated, such as a monomer ratio, emulsifier and initiator and the feed method. The suitable conditions to prepare the emulsion powder were experimentally found as follows: the emulsifier was SDS, the initiator was KPS, the temperature of the reaction was 40 °C, the ratio of the core to shell was 2:1 and the feed method was semi-continuous process. And also presence of the core-shell bedded structure was verified with electron microscope. In the consequent spray-drying step, the optimized operation parameters were obtained as follows: the inlet air temperature was 150 °C, outlet temperature was 75°C, and feed speed was 10.5 ml/min. Through experiments, the good coated milk white emulsion powder with good fluidity, evenly-distributed average diameter of 100μm, and good membrane performance was achieved. The experiments show that proportion of seed emulsion and shell monomer, feed method and inlet air temperature were the main effects on the performance of emulsion powder.

This paper reviews the current status of grain drying and storage in the three provinces of Northeast China. It presents an analysis of the postharvest grain losses, especially during drying and storage. Statistics show that the various losses add up to be 8-10%. China State Grain Administration, the Ministry of Science and Technology and the Ministry of Finance have joined efforts under "National Science and Technology Development Program" in carrying out the project "Grain Preservation". The project focuses on development and integration of grain storage and loss reducing technology as well as demonstration of this technology during the tenth and eleventh five years plans. Heilongjiang Zhongliang Storing Technology & Engineering Co. Ltd is actively involved in implementing this project. The company developed five new types of grain storages according to the climatic characteristics and handling practices. They include the steel-meshwork ambient air ventilated silos (which reduce grain moisture by aeration) and small-scale mobile grain dryers (which are servicing groups of farmers with sufficient grain supply.) All these innovations aim at decreasing grain postharvest losses and maintaining the grain quality as well as generating profits to farmers and thus providing incentives for them to remain in the rural areas.

In the present study, salt granules were dried in fluidized bed dryer and suitable technologic parameters of drying operation were obtained. The results could direct design of industrial dryer. Besides, the air distributing structure of fluidized bed dryer was studied and its pressure drop curve was measured. The result indicated that one layer intertexture net below the air distributing board could obtain good effect of air distributing without increase of pressure drop. This kind of structure could also prevent the material from leaking availably.

The present study was aimed to determine the equilibrium moisture contents (M_E) isotherms of okara powders that produced by means of three different drying methods: hot-air, spouted-bed, and freeze dryers. Observations showed that for the temperatures of 30, 40 and 50°C, the ME values of okara powders ranged from 1.5 to 24.5% d.b. depending upon the a_w values of okara samples. An increase in a_w values of okara increased the M_E isotherms of okara powders, while the temperature change appeared no to affect the M_E of okara powders. Freeze-dried okara powder was more sensitive to the changes of a_w values than hot-air-dried and spouted-bed-dried okara powders. Fitting of five sorption models to the experimental data revealed that the Halsey equation was the most excellent predictor to the M_E values of freeze-dried and spouted-bed-dried okara powders. The experimental M_E of hot-air-dried okara powders was best represented by the GAB model as indicated by the highest goodness of fit.

The objective of this study was to observe the effects of drying condition on milling quality and germination of BRRI 29. Experiment was conducted at Bangladesh Agricultural University (BAU) with both raw and parboiled paddy and raw paddy was procured from BAU farm in three batches. Initial moisture content of the raw paddy was 20.19%, 19.73% and 18.73% and that of parboiled paddy 36.46%, 33.65% and 32.71% of corresponding batches. For drying raw and parboiled paddy both sun and mechanical drying method were applied. Conventional sun drying method common to our country was applied for sun drying and for mechanical drying cabinet dryer was used. The study showed that for a specific moisture ratio raw paddy requires more time to dry under similar drying condition than parboiled paddy. For removal of 90% moisture parboiled paddy took 5 hours and raw paddy required 10 hours. Tests on milling quality showed that sun dried (45°C) paddy in double layer (5.32 kg/m²) gave the highest head rice yield (67%) and the lowest head rice yield (36%) was given by sun dried paddy at 53°C in single layer (2.66 kg/m²) indicating the adverse effect of drying temperature on milling quality of paddy. For germination rate sun dried paddy and mechanically dried paddy at 45°C gave the best result while paddy dried at 40°C, 49°C and 50°C gave poor result in this regard.

Studies were conducted to compare the quality characteristics of cocoa beans dried using solar dryer (direct type) and sun dryer with perforated and non-perforated platforms. A two-way analyses of variance was carried out to see the effects of these factors. No significant difference (p < 0.05) in drying time was found when drying was compared on the effect of perforation and type of dryer. However, slower rate of moisture reduction, in the early stage of drying, was observed in the solar dryer using non-perforated platform. Surface mould assessment showed that the perforated dryers produced beans with extremely light mould as compared to the non-perforated dryers. No significant difference was found (p < 0.05) in terms of pH, titratable acidity, fermentation index and in sensory evaluations when drying was compared on the effect of perforation and type of dryer. No interaction was also observed in these effects (p < 0.05). Results showed that solar drying can be used as an alternative to sun drying which has been known to produce good quality cocoa beans desirable for chocolate manufacturing.

Advanced drying technology enables drying of rough rice and dedusting of rice husks to be carried out simultaneously in the same unit processor. This paper reports the efficiency of dedusting of rice husks in a two-stage inclined cross flow fluidized bed dryer and the drying kinetics of rough rice in batch fluidized bed dryer as well as the conceptual design of a hybrid drying – dedusting unit processor. Experimental works had been carried out using rough rice (a Group D particle according to Geldart classification of powders) in a 2.5 m height two-stage inclined fluidized bed column of cross sectional area of 0.61m × 0.15m and a 3 m high batch fluidized bed dryer. The objectives of the study was to investigate the separation efficiency of dedusting of rice husk in the two-stage cross flow fluidized bed dryer and to study the drying kinetics of the drying kinetics of rough rice drying in the batch fluidized bed dryer. The experimental results showed that the dedusting separation efficiency at low superficial gas velocity gave unsatisfactory separation of merely 40% of rice husk. At higher superficial gas velocity, separation efficiency of rice husk as high as 93% was achieved. In addition, higher distributor inclination angle gave slightly improved separation efficiency. The drying kinetics showed that the residence time that is required to reduce the moisture content of rough rice to 18% (intermediate storage moisture content for second stage drying) is 3 minutes whereas the residence time that is required to reduce the moisture content to 13% (desirable final moisture content) is approximately 10 minutes regardless of the effect of kernel cracking. It was also found that higher drying temperatures gave higher drying rate. A conceptual design has been developed based on the results obtained in the studies. In order to maximize the heat utilization and to carry out two processes viz. dedusting and drying in one unit processor, it is suggested that drying – dedusting can be carried out in multistage mode where drying is taken place at each stage while dedusting is taking place at the upper stage. This concept can be applied to a packed bed or a fluidized bed unit processor.

The objective of the present study was to investigate the effects of various parameters, i.e., concentration of salt solution (2, 3, 4% (w/v)), boiling time (3, 5, 7 minutes) and drying air temperature (80, 100, 120°C) on the kinetics of drying and various quality attributes of shrimp, namely, color, texture, shrinkage and rehydration ability, during drying in a jet-spouted bed dryer. Small shrimp (350-360 shrimp/kg) was boiled and then dried until its moisture content was around 25% (d.b.). It was found that the color changes, toughness and shrinkage of shrimp increased while the rehydration ability decreased with an increase in the concentration of salt solution and boiling time.

The main objective of this study is to produce the aged Jasmine brown rice with low rancidity using fluidization in the first stage, followed by tempering and ventilation in the last stage. Khao Dok Mali 105 paddy variety was dried from the initial moisture contents of 28.2 and 33.3% dry basis to 22.5 ± 1.2% dry basis using inlet drying air temperatures of 130 and 150°C. After fluidized bed drying, paddy was tempered for 30, 60 and 120 minutes and followed by ambient air aeration until its final moisture content reduced to 16.3 ± 0.5% dry basis. Dried paddy, then, was stored for 7 months at the ambient temperature to determine the free fatty acid level. Shade dried samples, used as a reference, were also stored for 7 months. Jasmine brown rice qualities after processes such as head rice yield, cooking and glycemic index were determined. The experimental results showed that the combined technique could produce the aged Jasmine brown rice, with maintaining head rice yield. Regarding to cooking qualities, the percentages of water uptake, elongation ratio were higher for the treated samples and percentage of solid loss was lower. These tendencies were similar to the cooking qualities of reference samples. However, the FFA level after drying was significantly lower than control samples and slightly increased during storage for 7 months whereas it rapidly increased in the reference samples level. As observed from the result, the natural aging process had no effect on the glycemic index which still remained in high level, whereas the rice obtained from heating process showed the low glycemic index.

In this work, the rice parboiling using fluidized bed dryer with humidified hot air was studied. Suphanburi 1 paddy was soaked in the hot water and the obtained moisture content. It was then exposed to humidified. After that, the paddy was dried with normal hot air at the same temperature as that of humidified air. From the experiments, it was found that the higher head rice yield and the smaller amount of white belly were obtained when the paddy was exposed to humidified air for 60 seconds. The mentioned qualities were better than those obtained from the hot air drying alone. However, the color of white rice became darker than that obtained from hot air. For pasting properties of rice flour, the lower values of peak viscosity, breakdown viscosity and setback viscosity were found at longer exposure time.

The graft copolymerization of Styrene (ST), Methylmethacrylate (MMA)/Butylacrylate (BA) onto starch was carried chemically using ferrous ion-peroxide redox system. The combination of Starch with ST/MMA and ST/BA was used. The reaction condition was maintained at 60 °C and the monomer ratios were varied from 80/20, 50/50 and 20/80 for both the systems. The granular product of starch graft copolymer was made by spraying different concentrations of grafted starch emulsion on the native starch in the rapid mixer granulator. The resulted granules were dried in the Fluidized bed dryer. The resulted granular product was further analyzed for its physico-mechanical properties such as tensile strength, film strength and elongation at break and so on. The rheological properties of the resulting granular product as well as the starch graft copolymer emulsion were also studied. The viscosity of the granules measured at 28 °C which shows increase in the power law index with an increase in the grafting efficiency. The product finds huge potential as a sizing agent in the textile industry.

This work presents the evaluation of multi-stage adsorption dryers with air dehumidification by zeolite and alumina pillared clay. In a multi-stage dryer product is dried in a number of succeeding stages and for each stage the air is dehumidified by the adsorbent. The exhaust air from each stage is reused for product drying in a following stage after passing a bed with adsorbent. The heat efficiency of the drying system is evaluated and compared with a conventional drying system using air dehumidified by condensation. The evaluation concerns the effect of stage number, inlet dryer temperatures 10-50°C and inlet ambient air 10-25°C. Results showed that the performance of the multi-stage adsorption dryers increases with the number of stages where a three stage system is economically most promising. For varying ambient air conditions, zeolite as adsorbent is the most favourable.

Drying behaviour of cylindrical fresh green beans was investigated in a fluidized bed dryer with energy carriers. A pilot-scale fluidized bed dryer with inert particles was set up for performing the drying experiments. Glass beads particles were used as inert materials. The drying experiments were done with fresh green beans of several lengths using hot air with the temperature range of 30-70 °C. The experimental drying curves were adjusted to the diffusional model of Fick's law for infinite and finite cylinder with and without consideration of shrinkage to measure axial and radial effective moisture diffusivities. Radial and axial diffusivities (D_ref & D_zef) of cylindrical green beans were estimated in temperatures between 30 to 50 °C. An Arrhenius type dependence was observed between effective moisture diffusivities and drying temperature.

This paper presents an experimental study on the properties of the SEMOS heat pipe heat exchanger, which is to be applied into a fluidized bed drying system to recover the heat in the exhaust gas. The SEMOS heat pipe was made from copper with an inner diameter of 3 mm. Distillated water was used as the working liquid. The influences of gas flow type, position of heat source and gas flow rates on the property of the SEMOS heat pipe heat exchanger were investigated. The experimental results showed that the heat exchange capacity of a SEMOS heat pipe heat exchanger is about 4 times of a common tube heat exchanger; count-current gas flow, bottom heat source position and high gas flow rate give high heat flux. It was also found that, in the case of top placed heat source, the SEMOS heat pipe heat exchanger still well works.

Soybean seeds were contacted with silica gel in a fluidized bed, where mass transfer is driven by moisture concentration gradient. It has the advantage of well-mixing the solid adsorbent (silica gel) with the material being dried (soybean seeds) in fluidization state, and thus the dried seeds quality could be improved since they are in a uniform environment of low humidity. Separation of these two solids once desired moisture content is reached can be realized due to the size difference as well as the operation conditions of fluidization. The drying kinetics was compared under different mass ratios and fluidization conditions. The dispersion rate of soybean seeds was increased with addition of either silica gel particles, whereas the drying rate was improved with the gas velocity and mass ratio of silica gel. A scheme of sorption drying in a hybrid process of fluidized/fixed bed is proposed in the viewpoint of energy efficiency and product quality.

Wet granulation is traditionally considered an empirical art. The chemical and allied industry faces range of problems, including large recycle ratios, poor quality control, surging and even the total failure of scale up from laboratory to full scale production. However, in recent years there has been a rapid advancement in understanding of the fundamental processes that control granulation behavior and product properties. This paper presents the current understanding of the key area of wet granulation process: nucleation.

In the past, engineering design of dryers have always been a tedious affair involving rules of thumbs derived from experience and pilot scale experimental data with few available dryer simulator software to speed up the scaling up of the dryer to industrial scale. A few simulators have appeared in the market but they are not readily accessible to most dryer-design practitioners especially in the developing world. To solve the accessibility problem, the paper proposes to use a web-base design tool for simulating an industrial dryer. The plug flow fluidized bed dryer with cross flow drying medium (hot air or flue gas) for drying paddy was simulated using a new cross flow model that was developed by the drying technology research group at Universiti Kebangsaan Malaysia. A website program which is accessible over the internet and user-friendly has been developed using LAMP combination that allows preliminary parametric studies to be undertaken for this type of dryer. The model was solved using Runge-Kutta 4th order method. Various operating parameters of the dryer such as the air consumption (G/F), initial hot air temperature (T_i), initial solid temperature (T_si) initial hot air humidity (Y_i), initial solid moisture (X_i), length of dryer (L), step size length (Δz) and width of dryer (w) can be manipulated to explore the performance of the dryer. The web-based simulator calculates the conditions of the outlet streams of the dryer which are the solids temperature (T_s), exhaust air temperature (T), solids moisture content (X) and exhaust air humidity (Y) as a function of fluidized bed length which are shown on the web page. The model was verified by comparing experimental data on paddy using a pilot scale fluidized bed cross-flow dryer.

The appropriateness of the use Fick's diffusion equation to represent the falling rate drying kinetics forms subject of the present paper. Several authors have used Fick's diffusion equation to evaluate the effective diffusivity coefficient for different materials in fluidized beds. Marginal dependence of the evaluated diffusivity coefficient with the solids holdup has been reported without valid justification. Towards verifying the above, experiments are conducted in the present study by varying the solids holdup on a larger scale, by varying the fluidization column diameter. The estimated diffusion coefficient is found to vary from 2.4×10^-11 to 8.2×10^-11 for the variation solids holdup from 0.3 to 2.6kg. The inadequacy of the Fick's diffusion equation for modeling the kinetics of drying in fluidized bed is highlighted, cautioning the comparison of the kinetics often made based on the diffusion coefficients.

In this research, fluidized and fixed beds conditions were used for canola drying at eight temperatures of 30, 40, 50, 60, 70, 80, 90 and 100 °C using Lab. scale fluidized bed dryer. Effects of temperature and bed condition changes were investigated on drying time and drying rate parameters. Completely Randomized Design (CRD) as the experimental design was used with three replications. Results of experiments indicated that using fluidized bed technique increased drying rate and decreased the time of canola drying process. This effect is more notable in temperatures of less than 50 °C. For instance, fluidizing of canola grains in drying process caused energy saving and decreased drying time approximately 32% at temperature of 30°C compared with fixed bed drying. This effect was least for high temperatures and calculated approximately 27.8 % at 70-100°C. Besides by increasing the temperature, percentage of oil extraction of dried grains significantly increased and peroxide values of extracted oil remained unchanged. Fluidizing had good influence on quality factors such as free fatty acid and color.

Some physical parameters in terms of apparent density, specific heat capacity, void fraction, redness value (Hunter a-value), equilibrium moisture content (EMC), effective diffusion coefficient and thin-layer drying model for boiled Penaeus spp. shrimp were investigated. Due to determine physical parameters, the fresh shrimp was prepared by boiling with saline water at concentration of 3% (weight per volume) and initial moisture content of sample was provided between 300 and 400% dry-basis. For determining the EMC value, the samples was placed in each vessel which contained five saturated salt solutions providing relative humidity of 10-90% (KNO₃, NaCl, Mg(NO₃)₂•6H₂O, MgCl₂•6H₂O and LiCl) and surrounding temperature of 30-65°C. The results were curve fitted using five desorption isotherm models. The results showed that the predicted EMC data of Halsey model has the best fitting to experimental data To study the thin-layer drying kinetic, boiled shrimps were thin-layer dried by hot air temperatures of 50 to 70°C with an increment of 10°C/step and inlet air aeration was fixed at 0.5 m/s. The results showed that apparent density, specific heat capacity and void fraction was dependent to moisture content while EMC value decreased with temperature and increased with relative humidity. The evolution of moisture profile can be well-described by empirical drying equation of two term model. Additionally, an effective diffusion coefficient can be described by the Arrhenius type. An effective diffusivity ranging of 1.056×10^-7-1.7989×10^-7 m²/s was mainly affected by drying air temperatures of 49.1-68.5°C.

The deep-bed drying is an integrated process affected by many different factors. In this regard, the nature of deep-bed drying phenomenon was discussed, and the models and mass equilibrium equations for deep-bed hot-air drying process were constructed for the study. The material dehydration process, medium humidification process and system equilibrium were analyzed. The dimensionless numbers were introduced to simplify and solve the differential equations of deep-layer drying. Furthermore, the analytical formula and solution of the deep layer hot-air drying process were given. The results provided a kind of simple and practical analytical formula and calculation method, which are the base to hold the characteristics of deep-layer drying system well, and realize the accurate control of process.

In the traditional control system of dryers, it's considered that the drying process is inertial, that means the parameters are thought as stationary but in fact they are realtime variable. It results that the control accuracy can't match the real dynamic process. In this paper, the time sequence method was adopted to analyze the input construction of control system and the parameter transfer process and set up a model with real-time dynamic data.

The chemical and physical properties of coal are strongly affected by the upgrading process employed. This paper evaluates the feasibility of upgrading a low rank/grade coal using an oven drying method. The objective of this research work is to study the drying characteristics of low rank coals and to understand the factors affecting the quality of dried low rank coals. The results on drying kinetics, re-absorption of coal samples and proximate analysis of coal sample before and after drying are discussed. It was found that the upgrading process produced coal with better heating value and combustion characteristics than those of the raw coal samples.

In terms of dehydrating test on alfalfa, 5HC-1 type of conservation herbage dryer by advanced technology such as steel wire-bed conveyer, waste hest retrieving, turning over in airflow and mixed drying was designed, manufactured and tested. This paper describes the design and test of concurrent-flow dryer for conservation of quality on the basis of the experiment. The drying process-flow, construction and drying parameters of the dryer are presented. This designed dryer is suitable for farm, pasture and livestock-raising. Quality of dried alfalfa is good. This dryer is more efficient and adaptable. The cost of dryer is lowered. So the extension and application of the 5HC-1 type of conservation herbage are helpful to accelerate development of intensive breeding.

Two kinds of Mg(OH)₂ nanosheets were prepared by precipitation conversion method, and Mg(OH)₂ microparticles were synthesized by direct precipitation method. Drying kinetics experiments for three morphological micro-nanostructures of Mg(OH)₂ were performed and drying rate curves were obtained at 80°C-140°C. Results indicate that their initial moisture contents are different, and their drying rate curves which exhibit three stages: a set-up period, a constant rate drying period and a decelerating rate drying period are similar.

The influence of drying parameters including temperature, vacuum degree and thickness of material etc. on vacuum drying catalyst of zinc acetate/activated carbon were studied. The results showed that vacuum drying was fit for the catalyst of zinc acetate/activated carbon drying. The vacuum drying of catalyst only had falling drying rate period. the induction and constant drying rate period did not exist. Vacuum degree and temperature both affected the drying kinetics, but the effect of vacuum degree was in terms with drying temperature. The higher temperature, higher was the drying rate and the vacuum degree had obviously effect on initial drying rate. The higher thickness, higher was the drying time, but drying intensity was slightly increased. The drying temperature of catalyst should at 60°C-80°C for vacuum drying in order to avoid surface pulverization and get higher drying rate. Through the orthogonal experiment of temperature, vacuum degree and bed height, it was concluded that the temperature had the most important effect for the drying intensity. Comprehensive analysis that including drying quality and drying economy showed the drying process of at 40mm bed height, 9000Pa and 80°C was very meaningful for designing the tower continuous dryer of catalyst.

Special testing system is used to study drying characteristics and the characteristics of temperature change of Chrysanthemum Nakingemse Hand-Mazt (CNH.M) in a infrared radiation field under vacuum conditions, discussing the effects of their lives and activities on the drying process. The practicality of vacuum combined infrared radiation drying is assessed to provide some basic data for high-efficiency and low energy consumption drying equipment.

To develop the new drying technology for the condensing or dehydration of solvent extract of Chinese Herb Medicine (CHM), drying experiments of water extract of Astragalus were carried out, and 4 different techniques of microwave drying, hot-air drying, vacuum drying and freeze-drying were discussed in this paper. The micro-structure characteristics of samples were characterized by micrograph technique in the dimension of micron and nanometer, and the content of Astragalus polysaccharide (APS) of the samples were tested by ultraviolet spectrophotometer. The result shows that the dehydrated water content from the extract at 1h by microwave drying is almost the same as that at 4h by other 3 drying techniques. The microstructure characteristics of the dried sample by different drying techniques are related to the dehydration mechanism and its quality. The APS content of sample by microwave drying is little more than that by other 3 drying techniques. Therefore, the microwave drying technology is advantageous to the dehydration of water extract of CHM for its shorter drying time and better preservation of active ingredients.

For the investigation of the effect of Chinese herb medicine (CHM) pieces by different drying conditions, a representative medicinal material of rootstalk kinds, Radix Astragali was chosen and dried by microwave drying , hot-air drying , vacuum drying and frozen vacuum drying after re-hydration. The influence of medicinal material quality by different drying methods, through the character of molecular weight of extraction solution by the technique of ultra filtration and measurements of micron and nanometer size to microstructure of pieces with the environment scan electron microscope, under the Chinese curatorial theory of "whole idea" and the thinking of "crude compound". The results show that the external appearances of astragalus chips are all irregular porous shapes under the four drying methods; The speed of microwave drying method is 10 times as swift as three others; microstructure of microwave drying and initial pieces are approximate with massive cytoplasm; cytoplasm like granules by frozen vacuum drying and hot-air drying sticks to cell walls and is filled in cells very loose by vacuum drying. The content of small molecular of CHM by microwave drying technique is 82%, obviously higher than that by other techniques; experiments show that the quality of CHM depends on the microstructure. The lower the destruction extent of microstructure is, the better the quality of CHM is. Therefore, the microwave drying technology was advantageous not only to the extraction of effective components of CHM, but also to the subsequent operation such as purification and refinement etc.

A prototype of an indirect forced convection solar drier was designed for drying of tomato. The drier consists of a flat-plate concentrating collector, a heat storage cum auxiliary heating unit and a drying unit. The drier is a multi stack type with five trays having a loading capacity of 18 kg of fresh half cut tomato. The drier was tested in different weather and operating conditions such as day time drying using solar radiation and night time drying with ambient air (without external heating), night time heating with hot water flow from the storage tank without water heater, night time heating with hot water flow using water heater and in adverse weather (cloudy, foggy or rainy) day-night heating using water heater. Day time average temperature at the outlet of the collector was about 30°C over ambient air temperature and collector efficiency varied from 25 to 60%. Colour, ascorbic acid, lycopene and total flavonoids of fresh and dried tomato at different final moisture contents were determined. Tomato halves were pre-treated with UV radiation, acetic acid, citric acid, ascorbic acid, sodium metabisulphite and sodium chloride at different doses. Among them, 8 gl^-1 sodium metabisulphite was found effective to prevent the microbial growth at lower temperature (<45°C).

Dehydration of fruits with heat air is commonly used to preserve the products and extend shelf-life. However, long drying times and poor quality of dried products are frequent problems. The present work expected that the combination of osmotic dehydration and microwave drying as a pretreatment process could be shortly hot-air drying time and improve the quality of dried products. The yellow-green and 5-mm-thick slices were treated with combined osmotic-microwave process before dried consecutively with hot-air oven at 60°C. It resulted in a significant reduction in the drying time of hot air process. When samples were soaked with 50% (w/v) sugar and 5% (w/v) salt for 2 h and then followed with microwave (540 W) for 12 min, a significant reduction in the drying time of hot air process was observed from 420 min to 120 min, as compared to non-pretreated control. It was also found that the fruits obtained discontinuous microwave energy gave the dried products, which had better appearance than those obtained continuous microwave energy. Thus, it is possible to obtain dried and intermediate moisture sapodilla products that have better quality than hot-air dried products with saving energy.

The adoption of drying technologies is greatly favored by measures taken to adapt the technology to local needs. Drying technologies can offer opportunities for new product development, value added features for enhanced nutrition and shelf stability for food supply. Drying technologies must be adapted to meet the different properties of traditional Indian commodities and offer potential benefits for entrepreneurial developments. Much of the production and post-harvest handling of products in India are done by low income farmers in rural settings, hence technological improvements must be based on low cost available materials and renewable sources of energy. This paper presents some of the drying developments we have accomplished in South India.

Osmotically dehydrated tomato was dried to low water contents using one of the following methods: hot air drying, microwave-assisted convective drying and solar-drying. The influence of osmotic pre-treatments on the lycopene content of tomato samples and their physical characteristics during drying was investigated. Tomato quarters were immersed in sucrose and salt solutions for different times. Solute gain (SG) and water loss (WL) were calculated and an immersion time of 3h was selected. Samples were further dried using different methods such as air drying, vacuum and microwave assisted air drying. Tomato quarters of uniform sizes were used in the drying experiments, carried out at air temperatures of 70°C, air velocities of 1 m/s, microwave power levels of 900W and application time of 5s, 10s or 15s. Quality evaluation was performed for all samples, including surface color (using a Hunter calorimetric system), and lycopene and total carotenoids content (using a Helios UV–Visible spectrophotometer). Results showed that osmatically pretreated samples conserved their surface color. However, methods using the high level of temperature, e.g. Microwave and hot-air drying, lead to a higher loss of lycopene and carotenoids content.

In a rotary tube dryer, heat transfer between the surface of the tubes and material is indirect and complicated. Despite the early appearance, at present, there is no appropriate theoretical model to describe such a process. Moreover, the research achievement on the heat transfer mechanism is still lack.

This paper presents an experimental method to determine the heat transfer coefficient between the tubes' surface and material in a rotary tube dryer. A unique experimental set-up was designed and built. The experiments were performed to analyze the influence of parameters such as rotary-speed, material filling ratio on the tubes' heat transfer coefficient. The experimental results also showed that the heat transfer coefficient varies with both radial and circumferential position.

This paper presents a unique experimental set-up for researching drying mechanism in the rotary tube dryer. Applying this set-up, the influence of moisture carrying gas flow-rate on drying process was investigated. It was found that the gas significantly affects the drying rate. There also exits a gas flow-rate resulting in a pick value of drying rate. Based on the investigation, the proper moisture carrying gas flow-rate was determined. This optimized gas flow-rate ensures the rotary tube dryer with high drying capacity and less heat consumption.

In this paper, a mathematical model of synthetic leather drying for removing the organic solvent is proposed. The model proposed adequately describes the real processes. To improve the accuracy of calculated moisture distributions a velocity correction factor (VCF) introduced into the calculations. The VCF reflects the fact that some of the air flowing through the bed does not participate very effectively in drying, since it is channelled into low-density areas of the inhomogeneous bed. The present paper discusses the results of experiments to test the deductions that increased rates of drying and better agreement between predicted and experimental moisture distributions in the drying bed can be obtained by using higher air velocities.

The computational simulation findings from improvement performed on an industrial-sized roller-kiln are presented in this paper. The improvement was emphasized on the temperature distribution during the drying process of ceramic-tiles. A computational fluid-dynamics (CFD) solver was used in the modelling and simulation of the temperature circulation. Tetrahedral meshes were generated with boundary-conditions according to the actual roller-kiln. The CFD results were shown in contour-plots, demonstrating homogeneous heat transfer and circulation of air-flow throughout the roller-kiln. An experimental prototype was constructed to validate the CFD findings. The results showed comparable range in temperature, validating the findings obtained from the CFD simulation. A secondary CFD simulation was also performed, using altered burner-temperature configurations for the modelling and meshing. The results also demonstrated consistent and uniform temperature distribution within the roller-kiln when compared to the initial CFD results. This consistency in heat transfer has proven that a similar drying profile can be achieved, despite the change in burner-temperature configuration.

Osmotic dehydration is a gentle and useful process with a promising future for perishable foods with removal of water achieved by immersion of food in a solution of high chemical potential. However, due to its low mass transfer rate, its application is limited. Microwave assisted osmotic dehydration was developed and demonstrated to improve osmotic mass transfer. The objective of this study was to evaluate microwave assisted osmotic drying pretreatment effects on dehydration rate and color change of apple cylinders during second stage air drying process. A central composite rotatable design (CCRD) was used with five levels of sucrose concentrations (34-63°Brix), five temperatures (34-66°C) and five treatment times (10-110 min). Transient moisture loss, color parameters L, a, b and total difference of color were analyzed. Statistical analysis showed that temperature and concentration were significant factors (P < 0.01). A first order kinetic model was fitted to the experimental data for color parameter. MWOD prevented color damages during air drying process compared with conventional air drying without MWOD pretreatment. The product color profile with MWOD pretreatment was close to or better than the color profile of freeze dried products.

The proposed solar thermodynamic drying system reduces the traditional dehydration process of Roselle used in the western region of Mexico, from approximately four days to four hours. In addition to the 95% reduction in process time, this system also maintains the roselle's nutritional content, especially that of ascorbic acid (vitamin C). The proposed drying system is based on current operating conditions in Colima, Mexico as well as on three quantifiable control variables of roselle: product weight, product humidity, and product drying temperature. The product control variables were quantified and defined during the project as: Initial weight (1.0 kg of fresh product), final weight (0.152 kg of dry solid), initial humidity (84.8%), final humidity (14.3%) and dry temperature (48° C to 68° C). Based on these control variables, the proposed system operates a continuously moving band at a constant speed. As the roselle moves along the band through the system's drying chamber, it is dehydrated by heated air. Initially, the system uses solar energy to heat fluid (i.e. water or thermal oil). The heat generated is transferred from fluid to surrounding air via a forced convection process. By greatly diminishing drying time and controlling humidity, the system affords considerable control over optimal end-product quality (i.e. protection from pollutants and destructive microbial activity). The proposed system's settings can be easily adjusted to accommodate other products as well, making it even more commercially viable for agro-industrial producers. The drying process eliminates the water or humidity content of the calyxes yet maintains the nutritional properties specifically, the ascorbic acid content. A low cost and durability of the system is considered in the design.

The influence of drying parameters of freeze-drying on quality of Pteridium Aquilinum drying was investigate, and the impact of drying board temperature, drying chamber pressure and material thickness on vitamin C content was studied by nonlinear regressional orthogonal design. Using single and double factor analysis method, the relation between experimental criteria and drying parameters was established, and the influence order of the parameters was determined. Experimental results showed that drying chamber pressure had the greatest influence than drying board temperature and material thickness. The optimal combination of the preserved quality parameters for the freeze-drying technology of Peridium aquilium was obtained through optimized theory in nonlinear method. They are as follows: the pressure of drying chamber is 55Pa, the temperature of the board is 42.5°C, and material thickness is 16.3mm.

A freeze-drying procedure is developed for manufacturing silver nanopowder with regular shape and uniform diameter. The procedure includes four steps: preparing precursor solution, freezing the solution, drying the congelation and calcining the drying product. The starting substances are silver nitrate and caustic soda and the precursor is diamminesilver solution. Three freezing styles including the direct freezing, the vacuum evaporation freezing and the spray freezing are adopted to freeze the precursor solution. In the drying stage, two heating styles for frozen solution are compared. The XRD and EDS spectrograms show that the products of freeze-drying are pure amorphous silver nanopowder without hard agglomeration. Silver cubic nanocrystal is subsequently obtained by the calcinations. The chemical fundamentals and the drying curves of freeze-drying are given. The processes of preparing silver nanopowder are described in detail. The affection of freezing and heating manners on characteristics of the powder are discussed. The mechanism of grain forming and growing up is analyzed according to the observation results. The characteristics of powder freeze-drying and its feasibility of volume-production are presented.

This study presents a mathematical model for the biological material's freeze-drying process. Significantly, we consider the fractal feature of the dried layer, the continuity equations for the water vapor and the inert gas in the dried layer are denoted by the diffusivity equation of the fractal porous medium, the Knudsen diffusivity is decreasing exponentially with the dried layer thickness. The theoretical model is solved numerically with a moving-grid finite-element method. The theoretical model is capable of predicting the motion of the sublimation interface, the temperature profile, the drying time and the concentration of the sorbed water. The model also can give a theoretical prediction of the influence of the fractal feature of the dried layer on freeze-drying process. An Example is presented, witch validate the model and demonstrate representative applications of such calculation.

Blueberries (Vaccinium corymbosum L) were dried combining microwave-vacuum, hot-air drying and freeze drying technologies to retain their nutritional value. Polyphenol retention, total polyphenols, anthocyanins, and antioxidant activity were evaluated in dried blueberries. Glycoside compounds for ellagic acid, quercetin, and kaempferol exhibited a higher retention than phloridzin, and R- and S-naringin in dried blueberries following dehydration. Freeze and HA-MIVAC^® dried blueberries had a higher retention of total polyphenols and anthocyanins. Freeze dried blueberries had higher antioxidant activity, followed by the combination of HA-MIVAC^®, MIVAC^® and HA drying methods. FD, HA-MIVAC^® and MIVAC^® treated blueberries had a higher retention of individual polyphenols than HA treated blueberries indicating that the nutritional properties of berries may be retained to a greater extent when these processes are employed.

An internet controlled atmospheric freeze drying system was designed, built and tested in the Department of Heat and Mass Transfer, Technical University of Łódź. Extensive experimental investigation of wound dressing chitosan membrane was carried out. A fundamental film sublimation based CFD diffusion model was developed and verified using Fluent 6.1 commercial CFD software. The model enables the simulation of phase change and water vapor diffusion process of the surface sublimation. Transport of non-condensable species can be calculated with species transport inbuilt model of Fluent 6.1 and used to predict surface sublimation rate under given conditions. Results were compared with AFD experimental data of ice plate and chitosan membrane. The viability of applying the CFD diffusion model to chitosan membrane surface sublimation dominated atmospheric freeze-drying process was demonstrated. Higher mass flux was found on the leading edge.

Atmospheric freeze-drying (AFD) could combine the advantages of both freeze drying (high product quality) and convective heat pump drying (lower process costs). A black box modelling approach, the diffusion model was adopted and verified. Effective diffusivity coefficient and activation energy were used to cover the AFD multi-component diffusion mechanism. Coupled with shrinkage factor diffusion model showed good prediction of the drying kinetics of 10 mm Idared apple cubes in the AFD process. Based on the estimation of presented prediction results, the diffusion model is capable of being applied to simulate AFD process for selected food products at constant and ascending process temperature (CT and AT) modes.

This study was carried out to determine the effect of cryoprotectants on the survival rate of yeast. The yeast entrapped in gelatin matrix which is mixed with saccharose, hydroxyethylstarch, trehalose, lactose, caboxymethyl cellulose, κ-carrageenan as cryoprotectants was frozen at -40 °C, -30 °C, and -18°C in one-dimensional heat transfer system (Neumann's Model), respectively. After freeze drying gelatin matrix was cut horizontally into every 5 mm thickness from the bottom and measured their pore sizes. The freezing temperature (-40°C, -30°C, and -18°C) during freezing process affected the freezing rate. At freezing temperature, the partial freezing rate in the matrix was depending on this distance. The higher the sample distances from the bottom, the lower the partial freezing rate. It was found that the concentration of cryoprotectants influenced on the freezing rate. Besides, the different survival rate of yeast was depending on the cryoprotectants and freezing rate. The highest survival rate was obtained from the matrix with saccharose and trehalose. The ice dendrite size formed in matrix during freezing process at -18°C, -30 °C and -40 °C showed a direct relationship with freezing rate and concentration. In the matrix, the maximum primary ice dendrite size was 215.88 μm at 1% and minimum primary ice dendrite size was 145.6 μm at 5% from the experiment at -18°C.

The objective of this work was to study and to optimize the conditions of freezing and freeze-drying process on liposomes. Liposomes coated with polymer have several advantages which allow enhancing liposome stability in order to decrease the leakage of entrapped solute and to improve the cellular uptake of liposomes; natural polysaccharides were used to coat the outermost surface of liposomal vesicle. To coat the liposomes by polymers, the methods of nanoprecipiation and emulsion-diffusion were prepared with the polymer which is not soluble in the aqueous phase (Polycaprolactone). From these results, the size of liposomes was not changed after the incorporation with the water insoluble polymer (PCL). So, it is possible that the liposome dissolves in the organic phase. Consequently, Eudragit^® E100 was selected as a polymer which is soluble in the aqueous phase for stabilizing the liposomes. From these results, the size distribution was larger than liposomes and nanoparticles of polymer alone. Finally, we performed the freezing/thawing and freeze-drying the liposome for studying of the stability of freeze-dried liposomes. The liposome coated by Eudragit^® E100 and liposome alone were not stable after freezing/thawing and after freeze-drying without cryoprotectant. Whereas, the liposomes with saccharose or κ-carrageenan were more stables after freeze-drying. The size of liposome incorporated by Eudragit^® E100 with cryoprotectant was smaller than without cryoprotectant.

Tissue valves have been used since the early 1960s when aortic valves obtained from human cadavers were transplanted to others individuals (homograft). This paper describes the initial step in the development of a bovine pericardium tissue freeze-drying. Freeze-drying is a process where water is removed from a frozen material by sublimation followed by desorption of the unfrozen water, under reduced pressure. The freezing process influences ice crystal size and, consequently, the primary and secondary drying stages. The objective of this paper was to investigate the influence of freezing rates on bovine pericardium tissue freeze-drying parameters. It was determined the glass transition temperature and structural information. It was determined primary and secondary drying time of lyophilized pericardium tissue. The assessed freezing was slow, fast and both following by a thermal treatment (annealing). The slow freezing with annealing protocol presented greater results than the others freeze-drying protocols. It maintained the Amide bands on collagen secondary structure, presented the shortest freeze-drying cycle and the lowest water content in the tissue when compared to the others freezing protocols.

The economy has became competitive, with impact on the industries of fruit juices which must advance in the sense of minimizing production costs and, at the same time, generating products that obey each time more rigorous patterns of quality. In this work liquid chromatography was realized to determine some quality characteristics in the final product, in this case lemon juice. Natural lemon juice and freeze drying lemon juice were analyzed to evaluate the influence of this drying process in vitamin C concentration. Endogenous dehydroascorbic acid was converted to ascorbic acid by precolumn reduction with dithiothreitol at neutral pH. Total vitamin C was determined by C₁₈ reversed-phase column with the phosphate buffer mobile phase (pH 2.5), incorporating dithiothreitol to main vitamin C in reduced form, and UV detection at 254 nm.

Unidirectional freezing and freeze drying were applied to a wide variety of silica gel precursors: from hydrosols to thoroughly aged hydrogels. Porous silica gels with 3 kinds of morphologies (lamella, flat fiber and microhoneycomb) were prepared from unidirectional freezing of hydrosols. On the other hand, porous silica gels prepared by unidirectional freezing of hydrogels had 3 kinds of morphologies (microhoneycomb, fiber with polygonal cross-section and powder). The morphologies of silica gels prepared were mapped for the gelation time, the aging time and the delay time determined from dynamic light scattering (DLS) measurements of silica hydrosols. The morphology of silica gel can be controlled by using the proposed map.

Experimental studies were carried out to validate the effects of dielectric cores in microwave assisted freeze drying. Silica gel was prepared as a porous material using the hydrolysis process, and quartz glass and sintered silicon carbide (SiC) were selected as the dielectric materials, respectively. The microwave input power varied from 91.4 to 96.5 Watts at a frequency of 2,450 MHz. Results show that using the dielectric material with a large loss factor can significantly enhance ordinary microwave freeze drying. At the input power of 91.4 Watts, the drying time with the sintered silicon carbide core was 160.8 min, 43.6% shorter than 285.1 min obtained with the quartz glass core. When the input power was 96.5 Watts, the drying time was reduced from 266.2 to 115.6 min with the enhancement being 56.6%. Analysis of energy utilization shows that the dielectric material with a larger loss factor can result in the higher energy efficiency.

A mathematical model that simulates temperature profiles during freezing process of standard pharmaceutical formulations was set up, and the ice crystal mean sizes were semi empirically estimated from the resulting temperature profiles. Water vapour mass transfer permeability values during sublimation step were also estimated from ice phase morphological parameters. All these numerical data were compared with experimental data, and a quite good agreement was observed which confirmed the adequacy of the present model calculations. It was confirmed that, for a given formulation, the mass transfer parameters during freeze-drying were strongly dependent on morphological textural parameters, and consequently, on the nucleation temperatures that fix the ice phase morphology. The influence of freezing rate was also predicted from the simulations, proving that an increase of cooling rates led to slower primary drying rates.

Monolithic PVA-doped silica gels were prepared by the sol-gel process and dehydrated by conventional freeze-drying. Tetraethoxysilane (TEOS), tert-butanol (TBA) and distilled-deionized (DDI) water were used as major materials in hydrolysis of the silica gels under acid-catalyzed conditions. Characteristics of PVA-doped silica gels were evaluated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analysis (BET) methods, respectively. The FT-IR patterns show that a typical feature of Si-O-Si linkages is formed. Morphological analysis by SEM indicates that a typical porous gel structure is achieved through freeze drying, and the PVA-doped silica gel has an interconnected porous structure with a pore size of 1-10 μm at macropore scale. Characterization by BET shows that the PVA-doped silica gels are mesoporous materials with a specific surface area of 1167 m²/g, a pore specific volume of 1.548 cm³/g, and an average pore size of 2.653 nm.

This paper presents results of an experimental study of atmospheric freeze drying (AFD) using a vortex tube, to produce low temperature air, an alternative for producing dried food products of high quality, which is comparable with vacuum freeze drying but at considerably lower cost. An experimental setup was designed and built to permit simultaneous application of convection, conduction and radiation heat input to the drying material without heating above its freezing point. Potato slices were used as model heat sensitive products. Four heat input schemes were compared: pure convection, two-stage convection, radiation-coupled convection and radiation-conduction-coupled convection. A series of experiments were conducted to investigate the feasibility of the said AFD system. Drying kinetics, quality evaluation and functional properties of the model products were investigated. Results indicate that proposed AFD system is a gentle drying process with potential to be used as an alternative to vacuum freeze-drying.

This paper deals with the first principle model based predictive control of the primary drying stage of a freeze drying of solutions in vials. In the proposed control approach, any online control problem concerned with a constrained optimization during the primary drying stage may be stated. It is solved using a special model predictive control framework where the model is used in the controller formulation. Our first simulation results show here the efficiency of the control software developed (MPC@CB) under Matlab. MPC@CB may be easily used for any other process and any constrained control problem.

The drying characteristics of impregnated plantation Poplar lumber were studied in this work. Drying experiments with three drying temperatures for the strengthening-solution impregnated and water-impregnated lumber (control samples) were conducted. The results showed that the end-checking occurred in solution-impregnated lumber is less than that in control samples. If the temperature in initial drying phase is high, the solution could be driven out through the end of lumber. The shrinkage in tangential direction and deformation in cross-section of impregnated lumber are evidently less than that of control samples. The lumber became darker in high temperature drying. To improve the lumber recovery and drying quality, the high temperature should not be used in drying impregnated lumber, especially in the initial drying phase.

Based on wood cell structure, this study derived a theoretical equation for calculating cross-grain coefficient of thermal conductivity for wood particle using analogism approach. By applying the derived theoretical equation, the coefficients of thermal conductivity for 20 wood species were calculated. Compared to the empirical data from the literature, the maximum error in the calculated coefficients was 8.25%, while the average error was not more than 4.7%.

Conventional drying of oil palm empty fruit bunches (EFB) fibers using flue gas from diesel burners frequently cause browning and dust explosion. Replacing the drying medium with superheated steam is expected to improve the quality of EFB fibers as well as improve the safety of the dryer. In this study, the effects of steam temperature and steam velocity on the quality of dried EFB fiber are investigated. The initial fiber moisture content is in the range of 0.96 to 1.0 g g^-1 dry basis. The drying experiment was carried out at atmospheric pressure, steam superficial velocity in the range of 0.3 to 0.49 m s^-1, and temperature in the range of 135 to 200°C. Three quality parameters of the EFB fibers, the color, strength and microstructure of the fibers were used to assess the changes in fiber quality as a result of superheated steam drying. The color is measured using a Minolta Chromameter. The fiber strength is measured using a testometric tensile machine. The microstructure of the fibers was viewed using a scanning electron microscopy (SEM). The color of the fiber was either improved or not significantly degraded. The strength of the fiber was also not significantly affected by the superheated steam drying. The microstructure was not significantly damaged by the temperature of superheated steam drying but was damaged by high steam velocity above 0.49 m^-1. Superheated steam drying is therefore found to improve the overall quality of EFB fibers compared to flue gas drying.

Surface quality is an important factor in many areas of the woodworking industry. When wood is used as an interior material for houses or for manufacture of furniture, the surface view of wood is very important. A study was performed to investigate the effect of drying methods on surface roughness and hardness of wood.

In this paper, experiments were conducted and mathematical models were developed to evaluate the impact of heat and mass transfer mode on infrared-microwave drying characteristics of tufted textile materials. The evolution of temperature, moisture content as well as the overall drying kinetics are obtained and discussed with various internal and external physical parameters.

Fine grinding of woody biomass by vibration mill was proposed and drying characteristic of woody biomass and effect of the moisture content on fine grinding by vibration mill were discussed. The samples were sawdust of diameter over 500 μm and woody powder less than 250 μm which were pulverized from wood chips by the vibration mill. Drying rate of the woody powder in the constant drying rate period was a little greater than that of the sawdust. The critical moisture content, where the constant rate period changes to the falling rate period, was independent of the sample size with the value of about 1 kg-water/kg-solid. When wood chips (<11.2 mm of diameter) were grinded by using batch-wise vibration mill for 30 minutes, moisture content affects the grinding properties of wood chips. The particle size distributions shifted to larger side as the moisture contents increased. In particular, moisture content higher than 0.2 kg-water/kg-solid made it hard for pulverizing the wood chips.

Rotary drying is an effective method to dry small sized solid materials, because of the enhanced contact between the solids and hot air by the lifting actions of the dryer flights. Rotary drying is also a complicated process as the operation involves physical motions of the solid materials in the dryer as well as the heat and mass transfer. Woody biomass in the form of forestry industry residues has been recognized as a promising resource for renewable energy and liquid fuels. Drying of the woody biomass is one of the key operations in development of the energy conversion technologies. This project has developed a mathematical model to simulate the woody biomass drying in a rotary dryer, based on energy and mass balance and transfer, correlation of residence time, and drying kinetics of the thin wood sheets. The model was applied both for co-current and counter-current rotary dryers, and the simulation results are consistent with the observed trend. However the accuracy of the model needs to be further investigated through experimental drying tests.

In this research the measured point in the dried wood is connected with temperature senor and pressure senor by taking advantage of a polyfluortetraethylene T-bridge piece so that the measurement of both temperature and pressure can be available simultaneously during microwave drying. The experiment was mainly conducted to investigate the variations of the inner temperature and steam pressure. Results obtained are summarized as follows: The drying process can be approximately divided into three stages on the basis of the variations of temperature called the rapid temperature-increasing stage, the proximate constant-temperature stage and the final temperature-increasing stage; increasing the microwave power will increase the temperature faster, and the proximate constant-temperature stage will be shortened with a higher value. Inner cracking usually appears in the initial stage of the drying on account of the excessive steam pressure in high moisture wood; charring usually appears in the final stage of the drying on account of the dielectric characteristics of high temperature point in low moisture wood.

Experimental investigations of plant sprouts drying in the fluidized bed and in the spouted bed have been carried out and these drying methods are compared to the careful but expensive freeze drying. The experimental set up and conditions are described. The influence of the drying temperature and the inert fluidizing gas is presented for drying of broccoli-sprouts. The content of vitamin C and carotin has been used among others for the assessment of the products.

A new advanced microwave drying technology has been developed using a continuous dryer combined with an air cooler and simultaneous disinfection process. The principle of the new technology consist of using microwave absorption filters made from special porous ceramics which act as both absorbent and transparent material for microwaves. Ceramic slabs reduce intensity of the microwave radiation to such an extent where overheating and hot-spots formation is prevented as well as other kinds of damages, including red-heating of metallic objects. All books and documents are recovered in high quality without any damage of the gold printing, colored reproductions, metallic objects and other components sensitive to microwaves. Moreover, the technology also killed moulds and their spores and, therefore, an additional disinfection is not necessary.

Different types of laboratory scale experimental drying equipment were analyzed using microwave heating and it was turned out that the relationships between the setup construction parameters and the properties of treated materials have dominant influence on the authenticity of measuring results. In cavities, of multimode the performance components cannot be measured precisely. A visualization model and a dynamic type drying apparatus have been developed in this work. The homogeneity of the high frequency field and the precise measurability of the desired parameters resulted an easy process control and raised the thought of non-thermal effect of microwave energy.

Accurate simulation of the drying in paper making process depends on accurate determination of different process parameters that influence drying. The most important parameter in this respect is a contact heat transfer coefficient. The objective of this work is evaluation of the contact heat transfer coefficient under dynamic pilot conditions applying the same cylinder surface temperatures and fabric tensions as in operating full-scale paper machines. A special attention is given to accurate measurement of paper temperature in short contact drying time. The contact heat transfer coefficients are calculated from the experimentally determined energy flux to paper and measured cylinder and paper temperatures under dynamic conditions. Existing drying model and simulation program has been adjusted to experimental results and used in simulations of the multicylinder dryer section with single-tier configuration.

Drying is one of the main processes in the course of the washing laundry. During the washing and drying processes in an electric or gas dryer, wrinkles could be formed on garments. To minimize the generation of winkles on the clothes after the processes, establishing an objective and reliable method of the wrinkle evaluation is required. Wrinkle has been assessed with the sensory test by the human observers, which were defined by AHAM and AATCC. This method cannot provide objective data for the wrinkle because people judge the same things differently according to their own subjective criteria. Thus the research described in this paper is focused on the development of an objective and quantitative instrument for fabric wrinkle grading based on the use of 2D-FFT. This technique has been proved to be objective and quantitative in comparison with the existing test method.

Experimental studies were carried out on the effects of blanching and drying on active components such as chlorogenic acid, flavonoids and amino acid in Folium Cortex Eucommiae Tea in the present paper. The results show that the target active components in the tea after blanching followed by drying were retained, and fresh leaves should be directly plunged into re-drying machine for blanching. The low temperature and short time of blanching are beneficial to reservation of the active components, especially at 100°C for 3min. The appropriate operating conditions were determined to be 170°C under a quantity of 150g for full-sauting drying, and 80°C for 2-3h for second-drying.

A tunnel-type dryer for Chinese medicine material is designed to satisfy the drying of different forms of Chinese medicine material in this paper. For assuring the quality of Chinese medicine material and meeting the needs of environmental protection, the heating source adopted electric heater. Hot-air temperature could be regulated automatically according to the forms of Chinese medicine material. Airflow velocity could be regulated by the air volume adjuster in air inlet of the fan. The tunnel length could be regulated according to the saturated degree of the exhaust air to reduce the waste of thermal energy. The drying tests indicated that the tunnel-type dryer could satisfy the drying of different forms of Chinese medicine material.

Toona sinensis leaves were pretreated by osmotic dehydration. The effects of temperature, immersion time, sucrose and salt concentration on water loss and solid gain during osmotic dehydration were investigated by response surface methodology. Consequently, second order polynomial models were developed for water loss and solid gain as a function of the experimental parameters. The optimal conditions for maximum water loss and minimum solid gain were temperature of 36°C, sucrose concentration of 47%, salt concentration of 10%, and immersion time of 4 hours.

Toona Sinensis, whose young leaves and shoots are edible and nutritious, is a perennial deciduous tree vegetable. In this paper, the volatile constituents of dehydrated Toona Sinensis by different drying methods were micro-extracted in solid-phase, and then were analyzed with gas chromatographic/mass spectrometry. The major flavor components include caryophyllene, aromadendrene, β-Elemene, camphene, and cubenol. The results showed that the components and relative contents are lowest by spray drying; meanwhile, the loss of flavor is relatively higher. Comparing with convection oven drying and natural solar drying, vacuum drying and microwave drying can preserve most of the original flavors of Toona Sinensis. Among all the drying methods, vacuum drying results in the highest volatile flavor contents and components.

The objective of this study is to conduct a survey and assess the quality of dried cocoa beans produced by smallholders from different producing areas in Malaysia such as Sabah, Sarawak, Perak, and Pahang. There areas are currently the significant producing areas with Sabah being the biggest producer in Malaysia. Results of the survey showed that most of the bean samples were obtained from plastic sack fermentation (62.5%) followed by box fermentation (25%) and the remaining (12.5%) were obtained from combination of techniques. In terms of fermentation duration, most of the samples were obtained from 5-day fermentation (56.3%) followed by 6-day fermentation (25%) with the remaining samples obtained from 4-day (6.3%) and 3-day fermentation (12.5%). The survey also showed that the samples were dried mostly using natural technique (87.5%), while the remaining samples were artificially dried (6.3%) or dried using combined techniques (6.3%). In terms of drying duration, most of the samples were obtained from 4-day (37.5%) and 5-day drying (31.3%). In some samples drying duration was 6 days (18.8%) and only a small proportion of samples were obtained from 3-day drying (12.5%), which could be from artificial drying. Several quality parameters were assessed such as moisture content, pH, cut test, fermentation index and sensory evaluation. Moisture content of the dried beans samples showed values ranging from 7.15% to 8.27% and pH measurement showed values ranging from 5.42 to 5.98. Cut tests showed that all the samples were well-fermented with percent brown beans of more than 60% which agreed well with the fermentation index with absorbance ratio of more than one. Results showed no significant difference (p>0.05) among the bean samples for moisture content, pH, degree of fermentation (cut test score and fermentation index), and sensory evaluation (cocoa, bitterness, astringency, and sourness flavour attributes) based on the different locations. Sensory evaluation showed that the samples were lower in cocoa flavour and higher in bitterness, astringency, and sourness as compared to the West African reference sample.

Edible films are alternative packaging, which have recently received much attention due mainly to environmental reasons. Edible films may be formed from edible biomaterials such as polysaccharides, proteins or lipids. Among these biopolymers chitosan is of interest because it has a good film forming property, inexpensive, biodegradable, biocompatible and nontoxic. Drying is considered one of the most important steps in the production of edible films. It is therefore interesting to investigate the effects of various drying techniques as well as conditions on the drying kinetics and the various quality attributes of chitosan films. Drying at control conditions (ambient temperature, 30°C; 40°C in a hot air tray dryer) and under vacuum at an absolute pressure of 7 kPa were carried out at different drying temperatures (70°, 80° and 90°C) to investigate the drying kinetics of the films. The properties of chitosan films, in terms of their tensile strength, percent elongation and water vapor permeability (WVP), were also determined. The drying temperature was found to have an effect on the moisture reduction rates of the films. In terms of properties, chitosan films dried at control conditions had significantly less thickness, higher tensile strength and percent elongation than the films dried by vacuum drying. On the other hand, the WVP of chitosan films dried at any drying conditions was not significantly different.

Carrots are known as a natural source of β-carotene. Prior to its use, however, carrots must generally be processed and drying is one of the most common methods for processing carrots. During drying β-carotene in carrots suffers degradation. β-carotene degradation is generally due to thermal degradation and isomerization degradation, which refers to the transformation of β-carotene from one isomer to different other isomers. Naturally, β-carotene in carrots exists in its all-trans form. However, upon processing, some all-trans β-carotene isomerizes into different cis-forms, including 13-cis form. Recently, it has been reported that 13-cis β-carotene is the predominant cis-isomer and hence is an interesting isomer of β-carotene. To maximize the antioxidant activity of dried carrots, it is important to have an information on the isomerization kinetics of β-carotene. In this work, the drying kinetics as well as the isomerization kinetics of β-carotene in carrots undergoing hot air drying and vacuum drying were determined within the temperature range of 60 to 80°C and, in the case of vacuum drying, at a pressure of 7 kPa.

Hot air drying, vacuum drying and low-pressure superheated steam drying (LPSSD) of Indian gooseberry flake were carried out at various drying temperatures (65 and 75°C) and absolute pressures (7, 10 and 13 kPa) to monitor the drying kinetics and quality changes, in terms of color changes and antioxidant activity, of the product. The dried gooseberry flake was then soaked in hot water at 70, 80 and 90°C to prepare Indian gooseberry tea. In terms of the drying kinetics, the drying temperature had an effect on the moisture reduction rate of the samples in all cases. Vacuum drying, however, took shorter time to dry the product to the desired moisture content. Regarding the nutritional quality of the dried flake, it was found that the amount of ascorbic acid in the flake dried by vacuum drying was higher than those dried by hot air drying and LPSSD. However, LPSSD could retain flavonoid compounds better than did other drying techniques. On the other hand, total polyphenolic compounds and the total antioxidant activity of the dried flake were not significantly different among all cases. Regarding the release of antioxidants from the flake during tea preparation, no significant difference was observed between using the water temperature of 70, 80 and 90°C. Due to the more porous structure of LPSSD flake, however, higher compound degradation was noted. Nevertheless, it could still be concluded that drying the flake by LPSSD at 75°C and 7 kPa could best retain the active compounds, i.e., 62% of ascorbic acid, 91% of flavonoid compounds, 81% of total polyphenolic compounds and 83% of antioxidant activity; appropriate water temperature and time for tea preparation was 90°C and 5 minutes, respectively.

The object of this study was to investigate the stability and preservation characteristics of modified milk powder by measuring adsorption isotherm of water vapor and isosteric heat. Adsorption isotherms of water vapor for modified milk powders produced by three different companies of Korea (I, Y, M) and imported products (N, S, J) were measured at 15, 25 and 35 °C using modified COST-90 (European Cooperation in the Field of Scientific and Technical Research) method. The BET-model was applied to compare the experimental value. Our experimental results showed that all isotherms were sigmoid shape. As the temperature was increased, the propensity of EMC was decreased in all samples. The domestic infant formula milk powder of I and imported one of S showed the highest monolayer value of 5.07 g and 7.51 g [H2O]/100 g [solid], respectively. Isosteric heat was calculated from the result of application of BET-model using the Clausius-Clapeyron equation. Isosteric heat was declined in all samples as EMC was higher. As the milk powder adsorbed the water vapor and the water molecule is linked in form of free water, the isosteric heat is closed to the vaporization heat of pure water.

The potential therapeutic value of bromelain is due to its biochemical and pharmacological properties and hence, it is desired to obtain bromelain in its highest purified form. Crude bromelain extract can be obtained from the fruit of Ananas comosus using ion exchange chromatography. Bromelain thus obtained can be subjected to either spray or freeze drying. The resulting residual activity and the specific activity were compared between the spray and freeze dried powders. Freeze dried bromelain was found to posses the specific activity twice as compared to the spray dried powder. The effect of protective agents and the bulking agents on the retention of activity was studied in both spray as well as freeze drying. The initial results have been encouraging as 90 % of the bromelain recovery was possible.

Aonla fruits are used in traditional Indian system of medicines, like ayurvedic and unani, due to its therapeutic values. The aonla fruits are used in medicines to treat common cold, gastric troubles, headache, constipation, enlarged liver, etc. The fruit, due to its sour and astringent taste, has very limited table value. However, aonla fruits are processed into a number of products like preserve, candy pickle, juice, shreds, RTS beverages, dried powder, etc. Osmotic dehydration involves the partial removal of water from fruits by immersing it in a hypertonic solution. Osmotic dehydration of aonla is carried out for the preparation of preserves and to increase the sensory quality by removing astringent taste of the fruit. An experiment on osmotic dehydration of aonla fruit segments was carried out to optimize the process parameters. The process variables evaluated were temperature (30 – 50° C), concentration of sugar solution (40%, 50%), time of osmo concentration (1, 2, 4, 8, 12, 24, 36 and 48 h) and fruit sugar ratio (1:4, 1:5 and 1:6). Solids gain, water loss and texture of the final product were studied. Osmotic dehydration of the aonla fruits at 50° C in 50 % sugar solution with 1:4 fruit sugar ratio for 48 h resulted in higher solids gain and moisture loss. Hardness of the samples dehydrated in this condition was also higher.

Absorbable gelatin foam, commonly used in the surgery to stanch the flow of blood from a wound on the parenchymal organs, was synthesized and dried using freeze dryer (FD) and heat pump dryer (HPD). It was observed that heat pump drying takes 15 % lower time as compared to freeze drying at 38 °C for 2 cm thick foam patch. Freeze dried foam was found to be superior in quality in terms of water intake rate, water holding capacity, pliability, softness, and the pore size distribution. Beside quality aspects, the operating cost in freeze drying is almost 4.5 times higher as against the heat pump drying. Also, the equipment cost for freeze drying is 6 times expensive as compared to heat pump dryer.

Dehydration of fruits and vegetables is one of the most ancient and efficient preservation methods, used with various processes (sun drying, hot air, freeze-drying, vacuum drying…). The quality of the product and its cost are influenced by the drying operation. In the present paper we analyze physical mechanisms occurring during drying throughout heat and mass transfer for defining an efficient and economic three stage drying process consisting of hot air drying followed by a texturing by DIC (Instantaneous Controlled Pressure Drop) and finally using microwave assisted by ambient temperature air dehydration.

Water activity combined with the glass transition temperature can be used to predict the shelf life of foods. Water sorption isotherms and glass transition as a function of moisture content were determined for carrot chips after vacuum frying. The GAB model was fitted to the measured sorption data while the Gordon Taylor equation was used to model the water plasticization effect. The critical moisture content and the critical water activity at which the glass transition occurs were obtained at selected storage temperatures. The changes in moisture content, fat content, water activity, breaking force, β-carotene content, ascorbic acid and acid value of vacuum-fried carrot chip at selected storage temperatures (0, 10, 25°C) during a 6 month storage period were investigated. The estimated shelf life of carrot chip, defined by the degradation time of the acid value at different storage conditions, was determined.

Osmotic dehydration and skin abrasion were used as pre-treatments to reduce drying time and preserve total anthocyanin content of Vaccinium corymbosum L. (highbush) and Vaccinium ashei (rabbiteye) blueberries. Multi-stage drying at 90 °C for 90 minutes, 70 °C for 120 minutes and 50 °C until the water activity reached 0.60-0.65 and low temperature drying at 40 °C and 10% relative humidity were used. Skin abrasion provided more significant reduction in drying time than the osmotic dehydration. By using skin abrasion, drying time of the multi-stage dried samples was decreased from 24.5-27.5 hours to 6.5 hours. Similarly, the drying time was reduced from 9-10 days to 2-3 days for low temperature dried samples. The results obtained by LC/MS showed that pre-treatments and drying methods affected each anthocyanin in a different way. The dried samples with the highest total anthocyanin content (10.6 ± 0.7 and 3.9 ± 0.3 mg cyanidin 3-glucoside equivalents/g dry weight for highbush and rabbiteye blueberries, respectively) were the samples treated by skin abrasion prior to multi-stage drying.

Pineapple samples were dried in normal and modified atmospheres by addition of 0.5% ethanol v/v to the air stream using two different temperatures and two different velocities. The aroma composition changes during the drying process were determined using the solid phase microextraction coupled to a gas chromatographer with mass spectrometer. The modification of the drying atmosphere with ethanol vapor promoted a less intense water evaporation as well as a less pronounced aroma loss. The aroma composition change significantly during drying not only by the loss of some components but also by the appearance of others.

In this study, three encapsulation methods were employed to prepare the inclusion complex of flavor compounds and cyclodextrin derivatives. The methods included spray drying, solution method in which freeze drying was involved, and kneading in which vacuum drying was involved. Five different types of flavor namely ally isothiocyanate, d-limonene, ethyl butyrate, ethyl propionate, and l-menthol were studied on their encapsulation into two types of cyclodextrin derivatives (randomly methylated β-cyclodextrin, RM-β-CD and 2-hydroxypropyl-β-cyclodextrin, HP-β-CD). The flavor retention in the complex powders was analyzed by gas chromatography in terms of inclusion ratio. For both cyclodextrins, d-limonene retention of complex powders prepared from spray drying increased with the solid content of feed solution (10-50 wt%). However, the initial inclusion ratios were the lowest compared to other preparation methods. The highest retention of d-limonene (0.93) was achieved by kneading and vacuum drying of HP-β-CD system. The value was approximately 2 times of that of the complex powder prepared by spray drying.

Amaranth seeds can be popped under suitable heating conditions. The effects of gas temperature, flow rate and feed speed on expansion ratio, yield ratio and amino acid content were investigated, using continuous popping treatment system. According to the result, the ratio of under-sized product decreases at higher temperature. In addition, to achieve maximum output, while meeting higher expansion ratio, feed speed should be raised at higher gas temperature. Furthermore, the method of measuring the differential pressure in the test section was effective to maintain optimal operating condition.

Thermal transitions of whole fish muscles, and fat and fat-free muscles were measured by Differential Scanning Calorimetry (DSC). The initial freezing points were also measured using a cooling curve method. The fat-free fish muscles showed thermal transitions. However, it was difficult to justify that it was glass transition of whole or fat-free fish muscles. Water adsorption isotherms of king fish (Scomberomorus commerson) muscle were measured at room temperature by isopiestic method and data were modeled with BET and GAB equation. The initial freezing point and water activity showed strong dependence on moisture content.

The influence of drying temperature on rice taste quality was studied in this paper. The heated-air temperature of 40°C, 45°C, 50°C, 55°C, and 60°C, respectively, were used to dry fresh paddy. When the drying temperature exceeded 45 °C for paddy rice with an initial moisture content of 21.36% w.b., the rice taste value started to decrease significantly. In order to preserve rice taste quality, a drying temperature below 45 °C is recommended for drying paddy, if its initial moisture content is less than 21.36%. The relationship between the major rice ingredients such as protein, amylose, moisture, and fat acid and taste value was established based on the experiment data used to predict rice taste quality.

The aim of this work was to optimize the drying process of vegetal pear, and minimize energy resources (cost) under pre-fixed limits involving vegetal pear moisture, color and productivity. The optimization of vegetal pear drying was made by using Response Surface Methodology (RSM) for minimum process cost and color difference between fresh and dried samples (moisture ≤0.10 g water g d.m.^-1). A pilot plant drier was used for dehydrating vegetal pear slices (0.5 cm of thickness). The tests were carried out at different air temperature (60 to 70 °C), samples diameter (4 to 7 cm) and pre-treatment with ascorbic acid solutions (0 to 0.1 % w/w). The optimum conditions of drying process were 63 °C, 5 cm of sample diameter, and 0.075 % of ascorbic acid concentration. On the optimized drying conditions, dried vegetal pear presented values of moisture content of 0.052 g water g d.m.^-1, color difference 11.65, production 0.0073 kg h^-1 and total cost 30.58 $ kg dried product^-1.

The use of by-products from fruit and vegetable processing plants as sources of dietary fiber and bioactive agents is currently of interest. This work was aimed at studying effect of the drying (60°-80°C) on the hydration properties of cabbage powder, i.e. water holding capacity (WHC) and swelling capacity (SWC). The moisture contents of high dietary fiber powder from cabbage were in the range of 6-8% (wet basis) or 6.4-8.7% (dry basis) which lowered than the desired moisture content (less than 9% (wet basis)) recommended for the commercial dietary fiber powder. Drying temperature did not have a significant effect on the total dietary fiber contents of cabbage outer leaves (40.50-43.15 %). Insoluble dietary fiber (IDF) contents were much higher than the soluble dietary fiber (SDF) contents leading to the SDF:IDF ratios of 1:7.5 to 1:7.8. The effect of particle size of fiber powder in the range of 63-450 μm, on the hydration properties was also evaluated. Decreasing the particle size of cabbage outer leaves resulted in decreasing of WHC and SWC. Comparing at similar particle size, WHC and SWC of outer leaves of cabbage fiber powder were not significantly different among 60°-80°C drying temperatures.

Sapota (Achras zapota) is a tropical fruit found in several parts of India. It is one of the most popular fruits besides mango, custard apple and several others. The fruit is highly perishable and needs proper processing in order to preserve it in a dry form, preferably as a powder or granules. The high sugar content in Sapota (up to 15% on wet basis), besides high aroma and several medicinal properties makes the process of dehydration, a commercially attractive venture. The Sapota paste was dried in a convective dryer at temperatures of 40-60°C and its properties were analyzed. The properties such as water activity, sugar content and rehydration ratio were analyzed. The convective drying was compared with several other drying technologies such as heat pump assisted drying and freeze drying. The drying data was analyzed to compare effect of different operating parameters.

In this research the effect of drying condition on optical properties of apple slices was investigated. Hunter values (L, a, b) were used to measure the color parameters. Effect of various coating materials such as Carboxymethylcellulose (CMC), Starch and Pectin and drying condition including microwave treatment in presence of coating materials on optical properties with respect to microstructural changes, was studied. Some of microstructural properties and its effects on optical properties were discussed. So scanning electron microscopy (SEM) technique were used to analyze the effects of these processes on microstructure. Color changes values including total color difference (ΔE), and browning index (BI) were measured. Results showed that optical properties of samples were affected by drying condition and coating material. So that coated samples by pectin had a lower L and higher BI, but different results in presence of starch were achieved. Microwave treatment in presence of appropriates coatings could improve optical properties of dried slices.

Response surface methodology was used to determine the optimum processing conditions that yield maximum water loss and weight reduction and minimum solid gain and water activity during osmotic dehydration of carrots. Temperature (30-50 °C), processing time (120-240 min), glucose syrup DE = 42 (30–50% w/w) and salt (5–15% w/w) concentrations were the factors investigated with respect to water loss (WL), solid gain (SG) and water activity (a_w). Experiments were designed according to Central Composite Rotatable Design with these four factors each at three different levels, including central and axial points. Experiments were conducted with constant agitation of 150 rpm and solution to sample ratio of 10/1 (w/w). With respect to water loss, solid gain, texture strength and water activity, both linear and quadratic effects of four variables were found to be significant. For each response, second order polynomial models were developed using multiple linear regression analysis. Analysis of variance (ANOVA) was performed to check the adequacy and accuracy of the fitted models.

This study investigated the effect of air temperature (100 – 200°C) and velocity (0.15 – 0.45m/s) on drying characteristics and quality of different alfalfa components. The chopped alfalfa components, including stems, crushed stems, crushed stems with attached leaves, and leaves were used for the study. The moisture losses under different drying conditions and times were measured. The quality of dried products, including color, protein, and fiber content was also examined. The leaves and uncrushed stems had the highest and lowest drying rates among the four components. The increase of drying temperature and air velocity resulted in higher drying rates of all components. But increase also caused high difference in moisture contents of leaves and stems of dried stems with attached leaves. No significant different was found for the crude protein in leaves below 160°C. Alfalfa greenness of leave improved with the increase of air velocity and temperature at low range below 0.3m/s and 160°C, respectively. Based on the test results, to achieve high drying rate and desirable product quality of alfalfa a combination of 160°C temperature and 0.3m/s air velocity is suggested.

Pomegranate Punica granatum contains various polyphenolic constituents and has been studied for its anti-oxidant and anti-inflammatory properties. Pomegranate juice has been demonstrated to be high in antioxidant activity and is effective in the prevention of atherosclerosis. It is previously confirmed that pomegranate peel had the highest antioxidant activity among the peel, pulp and seed fractions. In this study, the influence of different drying methods on drying kinetics of pomegranate peels was investigated. Samples were dried in different methods such as vacuum drying, solar drying and microwave assisted air drying. A laboratory microwave-convective dryer was developed which had the provision of regulating microwave power and air temperature. Pomegranate peels of uniform size was used in the drying experiments which were carried out at air temperatures of 50, 60 and 70°C at 600 mmHg and microwave power levels of 300, 450 or 600W.

Drying curves obtained from the data are fitted with different mathematical models for evaluating a suitable thin layer drying model. The page model satisfactorily represented the drying characteristics of pomegranate peels than other models.

Impinging jet flows of various geometric designs are commonly used in industrial drying applications for drying of paper, coatings, textiles etc. Despite the massive R&D effort in this field there are still gaps in our fundamental knowledge and ability to predict the flow and heat transfer characteristics under a wide variety of geometric, flow and thermal conditions encountered in practice. In this work we apply a turbulence model with unique near wall treatment for a rather complex case of a planar impinging jet subjected to medium frequency oscillations cooling a heated surface with large temperature differences between the jet fluid and the wall. Such predictive ability will be helpful for designers who wish to consider pulsing impinging jets for enhanced heat transfer for drying, heating or cooling applications.

Mass transfer in drying of solids is often described as a diffusion process controlled by Fick's second law, in which the temperature dependence of mass diffusivity should be determined, usually by means of a two-step method under isothermal experimental conditions. This method needs several experiments and samples, as would be expensive and time consuming. In this paper, a non-isothermal (linearly increasing temperature) procedure was used to determine the moisture diffusivity as a function of temperature with the complex optimization method. The effects of heating rate and experimental errors on the prediction accuracy of the parameters in Arrhenius equation were evaluated through pseudo-experimental data randomly generated by computer.

Drum drying is extensively used for drying of different types of starchy food products, sludge, suspensions and pastes of a wide range of viscosities. During drying, the drum surface temperature is selected on the basis of the heat sensitivity and desired final quality of the dried products. Condensing steam is commonly used as the source of heat for medium to high temperature applications. A simple liquid diffusion-based model is used in the present study to predict the drying performance of a pilot-scale twin-drum dryer. Numerical results are compared with experimental data obtained for a biological sludge. The agreement of model predictions with the pilot scale experimental data is very good. The validated model is then used to examine the effects of drying air relative humidity and impingement on the drying performance of high and low-temperature drum dryers. It is shown that unlike high-temperature drum dryers, drying performance of low-temperature drum dryers can be improved by using drying air of low relative humidity. Air-impingement helps to improve the moisture evaporation rate remarkably for high and low-temperature drum dryers. Effects of impinging air velocity and location are numerically simulated. A simple mathematical model of this type can be conveniently used for design, analysis and scale-up of industrial drum dryers. Retrofits can be designed to enhance performance or productivity of existing drum dryers as well.

Based on the concept of AAE(apparent activation energy), the warped apparent activation energy (WAAE) is introduced into the reaction engineering model in order to simplify the model. In the paper, the drying dynamic performance of three kinds of dried materials, potato, soap and silica gel, was studied by investigation of the impact of the drying medium (hot-air) relative humidity, which is 8%, 15% and 25%, on the WAAE of dried materials. The studied results show that the WAAE not only reflects the comprehensive effect of water evaporating resistance caused by capillary of porous solid, shrinkage of material surface, but also appears to the diffusivity of vapor molecule in drying medium during drying process.

Mass transfer in osmotic dehydration of fruits at atmospheric pressure has been modeled either by a phenomenological approach using Crank's model (which is a Fick's law solution), or empirically, using models developed from polynomial equations, mass balances, or relations between process variables (i.e. Magee's, Azuara's, and Page's models). For all these models, experimental data are required to determine the values of their adjustable parameters for specific processing conditions. From a wide variety of published data, the parameters for moisture loss (ML) and solid gain (SG) were calculated for the above-mentioned models, and a comparison of their correlation capability was made. Azuara's and Page's models yield better correlations (with mean absolute errors less than 1.26% for ML and 0.46% for SG) than Magee's and Crank's models (with mean absolute errors of up to 2.98% and 1.68% for ML and SG, respectively).

In this study, the drying behaviour of bergamot was fitted with the Page model with temperature dependence. The experiments were conducted at five different air temperatures (40, 50, 60, 70 and 80°C), wheras the air velocitiy was at 2 m/s. The effective diffusivities (D_eff) of bergamot were found to be 1.91×10^-9, 2.23×10^-9, 3.08×10^-9, 3.80×10^-9 and 4.15×10^-9 m²/s at 40, 50, 60, 70 and 80°C, respectively. Therefore, it can be concluded that the effective diffusivity increases with air temperature. The activation energy (Ea) for diffusion and The diffusivity constant (D_o) were calculated and were 17319 J/g mol and 1.86×10^-6 m²/s. During the falling drying rate, D_eff is the main process that controls drying.

Drying is one of the primary methods of food preservation. Determining coefficients used in drying models is essential to predict the drying behaviour. The present study was conducted to compute effective moisture diffusivity and activation energy of samples of orange slices. The thin-layer drying experiments were carried out under five air temperatures of 40, 50, 60, 70 and 80°C, air velocities of 0.5 and orange slice thickness of 6 mm. Results indicated that drying took place in the falling rate period. Moisture transfer from orange slices was described by applying the Fick's diffusion model. The effective diffusivity values changed from 6.27×10^-10 to 3.50×10^-9 m²/s for the range of temperatures considered. An Arrhenius relation with an activation energy value of 16466.8 to 40898.8 J/mol and the diffusivity constant value of 7.74 ×10^-7 to 3.93×10^-3 m²/s were obtained which shows the effect of drying air temperature, air velocity and slice thickness on the diffusivity.

By a theoretical analysis of heat transfer mechanism of a steam tube rotary dryer (STRD) based on practical data, this paper conducts a systematic analysis and comparison of various factors influencing heat transfer. It formulates a mathematic correlative model (MCM) that could be used in the design of a large-scale commercial dryer. Industrial operation data verified that MCM is reliable.

The aim of this paper is to study the conditions of origin of residual stresses in capillary-porous materials subjected to drying, and the influence of these stresses on deformation of a cylindrical isotropic body during secondary rehydration. The curve of material deformation following from secondary rehydration obtained on the basis of present model is compared with experimental data taken from the literature. Good agreement is observed between experimental and theoretical results.

The objectives of this study were to measure and compare the heat flux produced by a steady flow impinging jet with that produced by a pulsating jet. Data was collected using fast response thermocouples (10 kHz sampling rate) embedded in a steel block. The block was modelled as a semi-infinite solid, allowing heat flux to be calculated from surface temperature history. The pulsating jet was generated using a combustor with self-excited combustion oscillations. Both the pulsating and steady flow jets had similar exhaust pipe diameters, combustion chamber geometries, time-averaged mass flow rates, and exhaust pipe exit temperatures. However, results showed that the pulsating jet yielded significantly greater heat flux than its steady state counterpart. The heat flux enhancement was quantified and compared for two flow rates. This enhancement factor was found to be as high as two. Additionally, measurements were taken at multiple locations below the exhaust pipes to form a first order approximation of the heat flux profiles. These profiles were used to compare total heat transfer rates for all conditions. The complete experimental results and analysis of those results are presented and suggestions for future works are offered.

The drying process often defines such quality indices as: solubility, release rate of the active component, shape and size of particles, shelf life and the like. Among innovative drying technologies, the atmospheric freeze-drying with active hydrodynamics may be used to produce pharmaceutical preparations of superior quality. The application of this drying technology for heat-sensitive products allows transformation of typically batch processes into the continuous ones and therefore, to increase productivity and reduce energy consumption.

Developed mathematical model and software allows to determine stable operation parameters of the process, to control the quality of final product, and allows to solve such important problem as scalling-up.

A pulse combustor employed in a spray drying system offers a new approach for liquid atomization that yields high quality powders at low cost. Using a pulse combustion atomizer, there is no need for any form of nozzle dispersion and its atomization mechanisms differ from those of conventional atomizers, such as rotary atomizers, pressure and pneumatic nozzles. In this work, atomizing experiments, using a Helmholtz-type resonator as atomizer and an optical analyzer for measuring the mean diameters of atomized droplets and their distribution, were carried out and the effects of liquid feed rate, combustion flux oscillating frequency and liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. Results indicate that the droplet-size distribution is similar during conditions with a low feed rate, high frequency pulsating flow, and moderate viscosity. The droplet-size distribution is approximately a normal distribution. The Sauter mean diameter of the droplets ranges from 50 to 80 μm.

The tower continuous vacuum dryer was a new kind of drying equipment that has been developed in recent years. Its prominent characteristics were high efficient production, saving energy and friendly environment. It could be used for drying of granular material that was required excellent quality. It has been applied to drying corn and peanut, and was trying to apply to catalyst of activated carbon-supported zinc acetate. The main designing difficulty of the dryer structure was that the dryer must have excellent airtight performance in order to keeping the required vacuum degree when continuous feeding and blowdown, the contact surface area between drying product and heater should be as big as they could in order to getting higher heat efficiency and must increase crossflowing probability of dried products in drying room in order to uniformly supplying heat for dried product. In this paper, the difficulty above-mentioned was well solved by designing the new continuous vacuum valve (rotary valve for feed/discharge), and adopting the heating surface of diamond-shaped pipes and thin layer cross-type plates.

This paper presents a pre-drying scheme for molecular sieve based upon the analysis of a Rotary Flash Dryer (RFD) applied in the LAY type molecular sieves. It also formulates a mathematical model of drying height computation which results from an analysis of the solid movement in the RFD. Both cases were validated by experimental data obtained from a commercial equipment.

Aerogel is a nano material composed of porous permeated with uncoagulated gas based on pellets among 1 to 100 nm. A model describing the major features of the drying process of aerogel was developed based on the theory of integration of molecule to form a method for estimating drying time, a calculation formula for mass transfer rate was derived, and then a computerized research method for supercritical CO₂ drying was achieved. Not only the suitable operation and control to realize the simulate scale-up of drying process could be seek to reduced invest risk according economic budget before investment, but also the means of researching the supercritical CO₂ drying could be chosen to reduce the exploring experiment.

A rotary device was built in a home microwave oven, where wet grain kernels were dried in a moving state in random. It is aimed to improve the drying uniformity of the material to be dried in an electric field intensity which is not necessarily uniform in microwave dryers. Experiments were conducted to investigate the distribution of electric field and to compare the drying characteristics between static microwave drying and rotary microwave drying. The rotary microwave drying seems a promising alternative to dry large particles by overcoming the uneven drying problem in microwave dryers.