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This paper focuses on applying the Corcione model to the microchannel. The Corcione model is highly relevant because it provides accurate empirical relationships for forecasting the dynamic viscosity and effective thermal conductivity of nanofluids. These qualities are crucial for building and improving different thermal systems. The model presents and discusses two simple empirical correlating equations for forecasting the dynamic viscosity and effective thermal conductivity of nanofluids. Hence the aim of this work is to use Corcione’s model to demonstrate the fully developed laminar flow of an electrically conducting nanoliquid through an inclined microchannel. The energy equation takes into account the physical impacts of the heat source/sink, temperature jamp, and viscous dissipation. TiO₂ nanoparticles in water are taken into consideration in this work for enhanced cooling. Using the numerical program Maple, Runge–Kutta–Fehlberg 4th–5th-order method is utilized to solve the present research. Making use of graphs, all of the flow parameters are shown, and the physical consequences on the flow and temperature profiles are thoroughly examined. It is noted that a higher inclined angle enhances the velocity profile whereas a larger temperature jump declines the temperature profile. Furthermore, Corcione’s model often has greater velocities, temperatures, and reduced surface drag forces than the Tiwari–Das model.

Recent trends in processor power for the next generation devices point clearly to significant increase in processor heat dissipation over the coming years. In the desktop system design space, the tendency has been to minimize system enclosure size while maximizing performance, which in turn leads to high power densities in future generation systems. The current thermal solutions used today consist of advanced heat sink designs and heat pipe designs with forced air cooling to cool high power processors. However, these techniques are already reaching their limits to handle high heat flux, and there is a strong need for development of more efficient cooling systems which are scalable to handle the high heat flux generated by the future products.

To meet this challenge, there has been research in academia and in industry to explore alternative methods for extracting heat from high-density power sources in electronic systems. This talk will discuss the issues surrounding device cooling, from the transistor level to the system level, and describe system-level solutions being developed for desktop computer applications developed in our group at Stanford University.

Microelectroosmotic flow is usually restricted to low Reynolds number regime, and mixing in these microfluidic systems becomes problematic due to the negligible inertial effects. To gain an improved understanding of mixing enhancement in microchannels patterned with heterogeneous surface charge, the lattice Boltzmann method has been employed to obtain the electric potential distribution in the electrolyte, the flow field, and the species concentration distribution, respectively. The simulation results show that heterogeneous surfaces can significantly disturb the streamlines leading to apparently substantial improvements in mixing. However, the introduction of such a feature can reduce the mass flow rate in the channel. The reduction in flow rate effectively prolongs the available mixing time when the flow passes through the channel and the observed mixing enhancement by heterogeneous surfaces partly results from longer mixing time.

Fluid flow and heat transfer in the entrance region of rectangular microchannels of various aspect ratios are numerically investigated in the slip-flow regime with particular attention to thermal creep effects. Uniform inlet velocity and temperature profiles are prescribed in microchannels with constant wall temperature. An adiabatic section is also employed at the inlet of the channel in order to prevent unrealistically large axial temperature gradients due to the prescribed uniform inlet temperature as well as upstream diffusion associated with low Reynolds number flows. A control-volume technique is used to solve the Navier–Stokes and energy equations which are accompanied with appropriate velocity slip and temperature jump boundary conditions at the walls. Despite the constant wall temperature, axial and peripheral temperature gradients form in the gas layer adjacent to the wall due to temperature jump. The simultaneous effects of velocity slip, temperature jump and thermal creep on the flow and thermal patterns along with the key flow parameters are examined in detail for a wide range of cross-sectional aspect ratios, and Knudsen and Reynolds numbers. Present results indicate that thermal creep effects influence the flow field and the temperature distribution significantly in the early section of the channel.

The effects of thermal creep on the development of gaseous fluid flow and heat transfer in rectangular microchannels with constant wall temperature are investigated in the slip-flow regime. Thermal creep arises from tangential temperature gradients, which may be significant in the entrance region of channels, and affects the velocity and temperature fields particularly in low Reynolds number flows. In the present work, the Navier–Stokes and energy equations coupled with velocity-slip and temperature-jump conditions applied at the channel walls are solved numerically using a control-volume technique. Despite the constant wall temperature, tangential temperature gradients form in the gas layer adjacent to the wall due to the temperature-jump condition. The effects of slip/jump and thermal creep on the flow patterns and parameters are studied in detail for a wide range of channel aspect ratios and, Knudsen and Reynolds numbers. Furthermore, the effects of variable properties on velocity-slip and, friction and heat transfer coefficients are also examined.

In this work, theoretical analysis is carried out on fully developed hydromagnetic flow of heat generating/absorbing fluid in a vertical microchannel in the presence of Hall and ion-slip effects. The governing coupled flow equations are obtained in dimensional form and thereafter simplified by employing some similarity transformation variables and quantities. The transformed coupled equations are solved by adopting the Adomian Decomposition Method (ADM) and their solution represented in closed form. Interesting influences of some active parameter on different flow features are shown using line graphs and Table. The numerical values for the results obtained in this work using ADM were validated with results obtained from existing benchmark. Results from the analysis reveal that in the existence of heat generation/absorption, the primary velocity and the temperature distribution could be enhanced by growing the ion-slip and Hall current parameter, whereas its influence on velocity is contrary along the secondary direction.

The vortex in the branching microchannel enhances the mixing and heat transfer performance. To investigate the vortex intensity quantitatively, a lattice Boltzmann model for incompressible power-law fluid is developed by setting the range of lattice viscosity (0.001 $\le \nu \le$ 1). The validation of the current model is carried out by modeling the vortex in a T-shaped branching channel and the Poiseuille flow of power-law fluids. Then the vortex intensity in the $\psi$-shaped microchannel is numerically studied in terms of Reynolds number, branching angle and power-law index. The result indicates that both the recirculation length and height increase with the increase of the Reynolds number. The branching angle has a negative impact on the recirculation length, and it has little effect on the recirculation height. The influence of the power-law index on recirculation length and height depends on the Reynolds number.

In this study, numerical simulations are conducted to investigate droplet breakup in an asymmetric $T$-junction microchannel with different cross-section ratios. To this approach, a two-phase model based on the volume of fluid (VOF) method is adopted to study the three-dimensional feature of droplet motion inside $T$-junctions. The comparison reveals that the present results are in good agreement with previous studies. The effects of the capillary number (Ca), the non-dimensional droplet length ($L^{\ast }$), and the non-dimensional width ratio ($W^{\ast }$) on the breakup time and splitting ratio of daughter droplets are studied. Five distinct regimes are observed involving the non-breakup, breakup with tunnel, breakup without tunnel, asymmetric breakup, and sorting. Achieved results indicate that the time of breakup ($t_{\mathrm{\text{breakup}}}^{\ast }$) increases about 15% when the Ca is increased from 0.0134 to 0.0268 (about 100%). It is also found that the mass center of the mother droplet in the primary channel is shifted to a larger wide branch, which facilitates the asymmetric breakup of the droplet in a $T$-junction microchannel.

A new method to fabricate microfluidic channel which has metal electrodes on side wall is presented. Three dimensional electrode patterns were deposited through the shadow mask on highly recessed surfaces of microchannel. Polymer microchannel was fabricated using polymer molding technique. Shadow mask for electrode patterning were fabricated using MEMS process. Electrodes were patterned on side wall of microchannel using shadow effects occurring at angled evaporation through shadow mask. The electrodes on side walls facing each other are expected to provide more sensitivity at bio-analysis devices based on impedance variation.

The biological flow characteristics inside a microchannel were investigated experimentally using a micro-particle image velocimetry (micro-PIV) method. The main objectives of this study were to understand the blood flow in micro-domain blood vessels and to identify the feasibility of nano-scale fluorescent particles for velocity measurement. The flow field was analyzed with a spatial resolution of 1K×1K pixels at low Reynolds number flow. To obtain the spatial distributions of mean velocity, 100 instantaneous velocity fields were captured and ensemble-averaged. As a result, for the case of blood flow, there were substantial velocity variations in the central region of micro-channel due to the presence of blood cells in the blood flow.

This paper reports the hydromagnetic mixed convective flow of Carreau nanofluid in the vertical microchannel with slip and convective mechanisms at the boundaries. The main objective of this work is to analyze the conduct of Carreau nanofluid under Buongiorno model as the nano-dimensions of the particle consequently encounters random motion. The novel impression is to retain the outcomes of the flow in regard of Brownian dispersion and thermophoresis. Parameters such as buoyancy ratio, Brownian motion and thermophoresis along with the effect of Weissenberg number are discussed on distribution of flow, temperature and concentration by using graphical demonstration. Surface drag coefficients, transport rates of mass and heat are portrayed by numeric esteems. Boundary layer approximations are made use to tackle nonlinear ordinary differential equations and solved by Runge–Kutta–Fehlberg 4-5th-order method. Results so obtained elaborate that velocity depletes with increased values of buoyancy ratio and viscosity ratio parameter along with power law index. Also, distinct behavior is noticed in the profile of velocity for varying Weissenberg number by boosting and diminishing depending on the power law index. On the other hand, temperature rises by augmentation of thermophoresis and Brownian motion parameter. Elevation in Brownian motion parameter accelerate the concentration panel of the fluid. Skin friction and Nusselt number are in direct proportion with buoyancy ratio parameter and Brownian motion parameter, respectively.

This paper develops an efficient three-dimensional numerical procedure to predict incompressible flow in long microchannels. The major advantage of the present numerical procedure is its fast speed due to the parabolic character of the governing equations.

The physical properties of incompressible fluids used in heat exchangers, such as viscosity and thermal conductivity, change considerably with temperature during their normal operating conditions. This study investigates the heat transfer characteristics of microchannel flows by taking these variations into account. Our results demonstrate that the temperature effects are significant and must be taken into account if accurate predictions are to be obtained.

In order to improve the robustness of microfluidic networks in printed circuit board (PCB)-based microfluidic platforms, a new method was presented. A pattern in a PCB was formed using hollowed-out technology. Polydimethylsiloxane was partly filled in the hollowed-out fields after mounting an adhesive tape on the bottom of the PCB, and solidified in an oven. Then, microfluidic networks were built using soft lithography technology. Microfluidic transportation and dilution operations were demonstrated using the fabricated microfluidic platform. Results show that this method can embed microfluidic networks into a PCB, and microfluidic operations can be implemented in the microfluidic networks embedded into the PCB.

With the increasing flourishing of miniaturized, multifunctional, and heterogeneously integrated system in package (SiP), heating problem is becoming more and more serious. In this paper, to meet the heat dissipation needs of the chips thus assembled and to achieve effective thermal management, linear, serpent and spiral shaped microchannel heat sinks were designed and fabricated into copper substrate by electrical discharge machining (EDM) and precision machining technology, acting both as the cooler and mounting base for passive and active SiP interposers. A test platform was set up to characterize the heat dissipation performance of the copper-based microchannel heat sink. The experimental and simulation results show that heat dissipation rate increases with the increasing heat flux density in the range 5–30 W/cm² for the three microchannel designs, and the peak temperature can all be kept below 340 K (67${}^{\circ }$C) even for the highest heat flux. The three designs are compared from the perspective of peak temperature, temperature distribution uniformity and pressure drop. In all, the solution proposed hereby provides a new and optimal option for in-situ cooling for densely integrated electronic hardware.

This research paper presents an investigation into the behavior of rarefied flow and heat transfer in a rectangular microchannel utilizing a Cu-water nanofluid. The study employs the thermal lattice Boltzmann method (LBM) with a lattice featuring a double distribution function and a BGK collision model. The simulations are performed using Python software, incorporating slip velocity and temperature jump effects. The primary objective is to analyze the influence of various thermophysical parameters of the coolant fluid on the microchannel, specifically focusing on the characteristics of the Cu-water nanofluid. The study considers laminar flow conditions with nanofluid volume fractions of 2%, 4% and 6%. The findings reveal that both rarefaction effect and Reynolds numbers, as well as the nanoparticle volume fraction, significantly impact the system. Moreover, the investigation evaluates key parameters such as the Nusselt number, skin friction coefficient, temperature jump slip velocity and velocity and temperature profiles. Notably, the nanoparticle volume fraction exhibits minimal influence on the velocity distribution or temperature field, whereas the Nusselt number increases with higher nanoparticle volume fractions. Additionally, the rarefaction effect leads to a reduction in velocity and temperature. At a nanoparticle volume fraction of 2%, increasing the Reynolds number results in elevated velocities and lower temperatures. The skin friction coefficient displays a decreasing trend along the microchannel with increasing Reynolds numbers. Furthermore, an increase in Knudsen numbers corresponds to a decrease in the skin friction coefficient. Finally, an increase in the nanoparticle volume fraction is associated with a decrease in the skin friction coefficient.

As a kind of microchannel layout with good transport performance, tree-like branching microchannel network has been widely used for microfluidic systems, however, the optimal analysis of the tree-like branching microchannel network for electroosmotic flow (EOF) to reach a minimized fluidic resistance still needs a deep study. In this work, the EOF in tree-like branching microchannel network is theoretically and numerically studied. It is found that there is an optimal structure of the tree-like branching network for the EOF to achieve a minimum fluidic resistance under the size constraint of constant total channel volume. This work found that the optimal channel radii of the tree-like network for EOF to reach a minimum fluidic resistance satisfy the relationship of $r_k^2={\sum }_{i=1}^N{r}_{k+1,i}^2$, where $r_k$ is the radius of the parent channel, $r_{k+1,i}$ is the radius of the child channels and $N$ is the total number of child channels. This formula can be regarded as an extended Murray’s law for EOF and is helpful for the optimization design of tree-like branching microchannel network for EOF to reach maximum transport efficiency under the constant applied driven voltage.

A two-dimensional model is developed to numerically study the water flow boiling through a tree-shaped microchannel by VOF method. In this work, the bubble dynamics and flow patterns along the channel are examined. Additionally, the pressure drop, heat transfer performance and the effects of mass flow rate and heat flux on the heat transfer coefficient are analyzed and discussed. The numerical results indicate that, there are three main bubble dynamic behaviors at the wall, namely coalesce-lift-off, coalesce-slide and coalesce-reattachment. At the bifurcation in high branching level, the slug bubbles may coalesce or breakup. The flow patterns of bubbly, bubbly-slug flows occur at low branching level and slug flow occurs at high branching level. The passage of bubbles causes the increasing of fluid temperature and local pressure. Additionally, the pressure drop decreases with the branching level. The flow pattern and channel confinement effect play a vital role in heat transfer performance. The nucleate boiling dominant heat transfer is observed at low branching level, the heat transfer performance is enhanced with increasing branching level from $k=0$ to 2. While, at high branching level, the heat transfer performance becomes weaker due to the suppression of nucleate boiling. Moreover, the heat transfer coefficient increases with the mass flow rate and heat flux.

This work theoretically studies the effects of wall velocity slip on the hydraulic resistance and convective heat transfer of laminar flow in a microchannel network with symmetric fractal treelike branching layout. It is found that the slip can reduce the hydraulic resistance and enhance the Nusselt number of laminar flow in the network; furthermore, the slip can also affect the optimal structure of the fractal treelike microchannel network with minimum hydraulic resistance and maximum convective heat transfer. Under the size constraint of constant total channel surface area, the optimal diameter ratio of microchannels at two successive branching levels of the symmetric fractal treelike microchannel network with a minimized hydraulic resistance is only dependent on branching number $N$ in the manner of $N^{-2/5}$ for no slip condition, but decreases with the increasing slip length, the increasing branching number and the increasing length ratio of microchannels at two successive branching levels for slip condition. The convective heat transfer of the treelike microchannel network is independent on the diameter ratio for no slip condition, but displays an increasing after decreasing trend with the increasing diameter ratio for slip condition. The symmetric treelike microchannel network with the worst convective heat transfer performance is the network with diameter ratio equaling one for slip condition.

The present work presents a simplified mathematical model to calculate the flowrate of the combined electroosmotic flow (EOF) and pressure driven laminar flow (PDLF) in the symmetric tree-like microchannel network under the assumptions of small zeta potential and thin electrical double layer. A numerical analysis of the combined EOF and PDLF in symmetric Y-shaped microchannel is also carried out to validate the mathematical model. The analytical results and numerical results are found to be in good agreement with each other. Using the mathematical model, the present work further investigates the effect of diameter ratio of the tree-like network on the flowrate of the combined EOF and PDLF to recognize a possible conclusion being similar to the Murray’s law. Based on the present work, it is found that the symmetric tree-like network has an optimal diameter ratio to achieve the maximum flowrate for the combined EOF and PDLF when the total microchannel volume is constant; however, this optimal diameter ratio for the combined flow disobeys the generalized Murray’s law in a simple form of power function of the branching number $N$, and it is not only related on the branching number, but also depends on the branching level and channel length ratio of the tree-like network. Furthermore, the optimal diameter ratio shows a monotonous transition from $N^{-1/3}$ for the pure PDLF to $N^{-1/2}$ for the pure EOF with the increasing ratio of the driven voltage and driven pressure. The present work discusses the effects of these parameters on the optimal diameter ratio for the combined EOF and PDLF.