International Journal of Air-Conditioning and Refrigeration

Resorption refrigeration system, a novel type of chemisorption technique, employs two or more inorganic salts as sorbent reactants, which co-operate as working pair. The working conditions and some evaluation indicators of the resorption system with different working pairs in previous studies are collected and summarized in this work. The performance of the reactant salts is compared, and further effort direction of the selection of working pairs is also analyzed.

This paper studies an absorption machine driven by the heat recovered from a Solid Oxide Fuel Cell (SOFC). The absorption unit was first evaluated by a cycle analysis determining the sensitivity to the main boundary conditions and to the internal parameters. Then a specific simulation code of all the different devices of the absorption machine was developed to evaluate the performance and size of the unit together with its operating condition limits.

Recently, nanofluid is a hot research topic among thermal engineers to enhance the heat transfer. However, there are deviations between research groups in the effective thermal conductivity measurements by the transient hot-wire method. Since there has been no report for the researchers to select a proper data range of temperature to estimate the thermal conductivities, the deviation could be partly attributed to the poor selection of the temperature data range. In this study, the impacts of the data range selection, the power supplier response delay, the thermal coefficient of resistors, the hot-wire type and test section size on the thermal conductivity measurement using the transient hot-wire method are analyzed.

The proper selection of the temperature data range to be used to estimate the thermal conductivities of fluids using transient hot-wire method is suggested by investigating the impact of it on the measurement by both computationally and experimentally. The thermal coefficient of resistor is found to affect the measurement seriously whereas the type of hot-wire does not. The test section size of the measuring device is compared with the thermal penetration depth.

The desiccant rotor is the most essential component of desiccant cooling system, but one of its drawbacks to spread out is its rotor size. To reduce the size of rotor the analysis of rotor performance is crucial. Systematic examination on the effect of desiccant and channel geometrics has been conducted based on the numerical program previously developed. Considered parameters related to channel geometrics are channel shape and cross-section area of channel, and parameters related to desiccant are mass fraction, heat capacity, density, maximum water uptake and separation factor of isotherm. Considerable reduction of rotor size is expected by adjusting the parameters.

The Production of high IPF (ice packing factor) ice slurry was realized. The ice slurry maker which can efficiently produce ice slurry under ice particles in-flowing condition was revised. We removed the stagnant region at the top of the ice slurry maker, thereby high IPF ice slurry was realized. The IPF controller with 6 mm diameter holes could not control IPF in a pipe. This is because ice particles in ice slurry flow exist homogeneously not only at the upper part but also at the bottom part. We changed the hole size at the surface of the IPF controller by means of fine meshes, which, then, increased the IPF in the pipe by 70% when the mesh size was 80 μm or less.

There are many attempts to use a fuel cell system as a residential power generation system. The purpose of this study is to investigate the optimal design of a water tank for a hot water system when the fuel cell co-generation system is combined with a domestic hot water supply system. The demands of hot water supply per month per home for 76–168 m² of acreage are investigated in Busan for a year. It showed somewhat large differences between the actual demand and the designed demand of hot water, but the actual capacity of hourly averaged hot water demands is analyzed as 60 ℓ/h in this study based on the actual demand. The experiments are performed in the various inlet and outlet locations of nozzles in the hot water tank, and the hot water consumption rates. The experimental results showed that the optimal capacity of the water tank is 200 ℓ when the thermal efficiency, the storing capacity of hot water and the space for installation are considered.

In this paper, a comparative study of CO₂ and water-based brine secondary cooling systems for refrigeration applications is presented. CO₂ secondary systems are simple and could prove to be attractive for high temperature (HT) and medium temperature (MT) in industrial and commercial refrigeration applications regardless of climate. Calculations show that CO₂ secondary systems give a possibility of energy savings in the range of 10–20% for HT systems and more than 20–30% for MT systems. The design and particular challenges of CO₂ systems are discussed. The analysis is illustrated by case studies. Further possibilities to optimized secondary CO₂ systems by modulating pressure or applying frequency converters are discussed. The use of secondary CO₂ systems in commercial refrigeration installations (supermarket systems) is briefly discussed.

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Hence, the development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the performance of a simultaneous heating and cooling heat pump was investigated in the heat recovery mode (HR mode). The system adopted a variable speed compressor using R-410A with four indoor units and one outdoor unit. In the HR mode, the capacity and COP were improved as compared with those in the cooling or heating mode because the waste heat in the outdoor unit was utilized as useful heat in the indoor units. However, energy imbalance between heating and cooling capacities of each indoor unit was observed in the 2H–1C HR mode. Therefore, the performance of the system in the 2H–1C HR mode was enhanced by controlling refrigerant flow rate through the outdoor unit.