Double-layered Microchannel Heat Sink Research Articles

Heat dissipation analysis on the designed inner-outer circulation impingement double-layer microchannel heat sinks with chamfers in power electronic cooling system

This study discusses a new design which utilizes chamfers to further improve the thermal performance of inner-outer circulation impingement double-layer microchannel heat sinks by simulations and experiments manufactured with 3-Dimension printing. In contrast to former designed inner-outer circulation impingement double-layer microchannel heat sinks, inner-outer circulation impingement double-layer microchannel heat sinks with chamfer shows significant advantages in improving overall thermal performance in power electronic cooling. The results of simulation are in good agreement with those of experiment in five 3-Dimensional printing tests. It is demonstrated that the introduction of chamfers is effective in controlling the thermal gradient on substrate of heat sinks, and reducing the peak temperature on substrate of inner-outer circulation impingement double-layer microchannel heat sinks with chamfer as a result. The best performance is presented by a 0.2 mm chamfer located on the corner of the inner-outer circulation shaft in inner-outer circulation impingement double-layer microchannel heat sinks with chamfer. Experimental studies and numerical simulations both indicate that inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer significantly enhances heat transfer characteristics. In addition, the average Nusselt number for inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer is higher than that of other tests. Moreover, inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer performs better than other designs in terms of the overall heat transfer performance, which is significantly better than inner-outer circulation impingement double-layer microchannel heat sinks without chamfers.

Experimental analysis of double layer microchannel heat sink with distinct fin configurations in upper and lower layers

In the present experimental study, two distinct configurations of double layer microchannel heat sinks (DL MCHS) are proposed. It consists of rectangular parallel channels in the bottom layer and an array of square pin fins in the upper layer. Pin fin height (Hf) in the first configuration is equals to the channel height (Hc) (i.e. Hf/Hc=1). However, in the second configuration, pin fin height is equivalent to 75 % of Hc such that Hf/Hc=0.75. The proposed modified DL MCHS configurations are then compared with the conventional double layer microchannel heat sink (CDL MCHS). Hence, the idea of the current work is to develop a novel DL MCHS with improved heat transfer capabilities and reduced pressure penalties. Heat dissipation rate, pressure data and coolant flow behaviour are carefully measured and analyzed. Findings reveal that thermal performance of the modified heat sink with Hf/Hc=1 is not appreciable because it delivers almost similar to conventional configuration. Whereas, modified heat sink of Hf/Hc=0.75 has consistently exhibited better heat transfer rate and thermal performance factor. As compared to CDL MCHS, thermal performance factor was found ≈38 % higher in this case. Overall thermal and hydraulic performance of the DL MCHS is significantly influenced by the flow pattern of the coolant, which is a result of the novel channel design.

A facile design of porous heat sink optimized thermodynamically for thermo-hydraulic performance

Implementing active cooling through micro-channel heat sinks integrated with printed circuit heat exchangers demands a simultaneous enhancement of thermal and hydraulic performance, all while avoiding complex designs for ease of fabrication. We propose a porous wall embedded double-layered micro-channel heat sink, aiming to decrease the necessary pumping powers while maintaining a minimal impact on the heat transfer rate. Additionally, this design simplifies geometric complexities, enhancing ease of fabrication. We assessed the feasibility of different porous embedded double-layered micro-channel heat sink configurations by evaluating their thermal and hydraulic performance. Our analysis uniquely integrates the principles of the second law of thermodynamics with traditional first law analysis, providing novel insights into heat sink design. We discovered that configuring porous walls solely in the top layer of the double-layered micro-channel heat sink is the only viable option. Furthermore, our analysis reveals that embedding porous walls exclusively in the top layer reduces irreversibility due to frictional losses by 9.13 %, with a slight increase in irreversibility due to heat transfer by 1.55 %, in comparison to the solid double-layered micro-channel heat sink at a flow rate of 1000 ml/min. Moreover, at the same flow rate, compared to configuration with porous walls in both layers, the top layer configuration exhibits improved thermal performance by 17.28 %. Next, we demonstrate that while the first law analysis indicates the viability of the top porous configuration, the second law analysis limits its viability to a certain coolant flow rate range. Finally, we optimize the heat sink design and coolant flow rates, proposing a viable design by simply incorporating porous walls in only the top layer of double layered micro-channel heat sink, which otherwise proved to be non-viable.

Swarm-based multi-objective optimization of double-layered microchannel heat sink with hybrid solid-porous ribs

The current article focuses on the thermal and hydraulic optimization of a double-layered microchannel with hybrid solid-porous ribs. Therefore, for both upper and lower layers, solid-porous ribs, having different thickness ratios of porous and solid, are considered. The ratio of solid-porous thickness in the upper and lower layers and Reynolds number variations are taken into account as design variables. The present study is conducted to find an optimum design by which not only thermal performance improves, but also power consumption reduces. At the initial step, the double-layer microchannel is simulated using artificial neural network. The second step involves the application of the optimum network and the microchannel inputs for minimizing the thermal resistance and the power consumption single-objective and multi-objective type’s optimization problems are solved. The two mentioned optimization problems in the proposed strategy are targeted using four swarm-based algorithms. Results indicated that the designed neural network has a maximum error of 4% for producing the desired outputs. Moreover, the single-objective optimization of the second stage showed that by the porous ratios of 0.19 and 1 for the upper and lower layers, respectively, and Reynolds number of 578.7, the minimum values of pressure drop and overall thermal resistance are achieved.

Numerical analysis of flow and heat transfer characteristics of double-layer heterogeneous single crystal diamond microchannel heat sinks

In order to solve the heat dissipation problems associated with highly integrated and high heat flux microelectronic devices, in this work, a novel type double-layer heterogeneous single crystal diamond microchannel heat sink (DLH-SCD-MCHS) is designed and numerically analyzed, in which the upper channel is rectangular and the lower channel consists of various cavities and rib combinations. The comprehensive performance of the DLH-SCD-MCHS was analyzed by the correlation with pumping power and thermal resistance, and the enhanced heat transfer factor (η). The outcome shows that the DLH-SCD-MCHS significantly enhances the heat transfer while appropriately sacrificing part of the pressure drop. Compared with the traditional double-layer microchannel heat sink (DL-MCHS), the pressure drop of DLH-SCD-MCHS is increased by 23.8–43.5 %, the heat transfer coefficient is enhanced by 74.5–117.1 %, and the η is improved by 62.5–87.4 %. The DLH-SCD-MCHS can reduce the irreversible loss, and the minimum augmentation entropy generation number is 0.64 for the DLH-SCD-MCHS with rectangular cavity and rectangular rib (Model V). As Re = 874, the relative rib width, the relative rib length and the relative position of the ribs of the Model V are 0.5, 0.571 and 0.5, respectively, the maximum η is 1.97. The DLH-SCD-MCHS provides new insights for the management of the heat transfer system of microelectronic devices.

Modulating fluid rheology and confinement toward augmenting the performance of a double layered microchannel heat sink

AbstractThe improvement of the cooling performance of liquid‐cooled microchannel heat sinks used for densely packed electronic circuits is sorted via passive techniques like tuning substrate or coolant properties. We propose a design for enhancing heat sink performance by simulataneously modifying the channel geometry and tuning the fluid rheology. By modeling the coolant as a power law fluid, its rheological behavior is varied ranging from shear‐thinning to shear‐thickening, alongside Newtonian fluid. We introduced tapering to the middle wall that separates the bottom and top channels of a double layered microchannel heat sink (DL‐MCHS), causing both channels to converge. This convergence not only increases the flow velocity within the downstream microchannel but also reduces the apparent viscosity of the shear‐thinning fluid being subjected to shear, resulting in enhanced thermal and hydraulic performance. We analyze the results from both the first and the second law of thermodynamics context, demonstrating that a tapered DL‐MCHS with shear‐thinning fluid outperforms a straight partition wall DL‐MCHS with Newtonian coolant. However, we also discovered that extreme tapering compromises thermodynamic viability, but by fine‐tuning the extent of tapering, we inferred that a DL‐MCHS with shear‐thinning fluid can become viable with little compromise in the thermal performance.

Heat transfer properties of single crystal diamond zigzag double-layer microchannel heat sinks

Efficient heat transfer in modern microelectronic devices plays an essential part in improving the devices functionality and lifetime. Microchannel heat sinks offer excellent heat transfer properties, and have widespread applications in highly integrated electronic devices. The flow and heat transfer properties of single crystal diamond zigzag double-layer microchannel heat sinks (DL-MCHSs) were investigated by numerical simulation. The mechanism of enhanced heat transfer in zigzag DL-MCHSs was analyzed by the velocity, temperature and pressure fields, and the geometric parameters of the single crystal diamond DL-MCHSs were evaluated and optimized by means of performance evaluation criteria. The results illustrate that the zigzag channel not only increases the convective area, but also enhances the fluid disturbance leading to higher degree of fluid blending, which greatly enhance the heat transfer of the single crystal diamond DL-MCHSs. Upper zigzag and lower zigzag single crystal diamond DL-MCHSs can offer the highest performance evaluation criteria among the four structures. When Re = 700, the relative height of zigzag (α), the number of zigzag cycles (β), and the height ratio of upper to lower channels (γ) are 0.5, 45, and 1.2, respectively, the optimized upper zigzag and lower single crystal diamond zigzag DL-MCHSs achieve the 38 % enhancement in comprehensive performance. This work contributes to the corresponding scientific instruction for the management and implementation of the single crystal diamond DL-MCHSs.

Topology optimization of laminated-sheet microchannel heat sinks based on a pseudo-three-dimensional method

Laminated-sheet microchannel heat sinks (LS-MHSs) have shown enormous potential in the thermal management of integrated chips due to their advantages of easy integration, high surface-to-volume ratio and high heat transfer efficiency. In this paper, a five-layer pseudo-3D (P3D) conjugated heat transfer model of the double-layer microchannel heat sink (DL-MHS) was established, and topology optimization (TO) was applied for optimal design of the DL-MHS. The effects of different inlet pressures and lamination methods on the optimal design were discussed, and then, the optimization results were compared with those obtained for a single-layer microchannel heat sink (SL-MHS) and conventional parallel microchannel heat sink (CP-MHS). A full-scale 3D conjugate heat transfer numerical model was also built to investigate the heat transfer and fluid flow performance of the topology optimized microchannel heat sink. The results showed that the topology optimized microchannel heat sink can enhance heat transfer and show a higher heat transfer and comprehensive performance compared to the conventional parallel microchannel heat sink. Under the same pumping power consumption, the topology optimization of the DL-MHS with parallel flow obtains the best heat transfer performance, which is 2.04 times that of the CP-MHSs and 1.09 times that of the SL-MHS. Under the same pumping power consumption, the topology optimization of the DL-MHS with counter flow achieves the best temperature uniformity and its maximum temperature difference is 5.0–16.9 K lower than that of the CP-MHSs and 1.6–3.4 K lower than that of the SL-MHS.

Thermal analysis and experimental verification on double-layer microchannel heat sinks with impact jet nested arrays

The present study investigate a novel combined features which make use of impingement jet nested arrays (IJNAs) to strength the thermal performance of double-layer microchannel heat sinks (DMCHS) based on 3D printing technologies. The IJNAs are firstly introduced into the DMCHS to enhance the thermal characteristics compared with the traditional straight and impact jet straight arrays DMCHS. Three 3D-printed test samples were manufactured for experiments, and it is found that the numerical simulations are in line with the experimental measurements. The thermal control of the substrate temperature by introducing IJNAs is very effective, and the reduction in peak temperature on substrate is more than 20 K lower than that of traditional DMCHS. The experimental study and numerical simulation both show that the heat transfer enhancement of the impingement jet and nested structure is very pronounced. Besides, the average Nusselt number of IJNA-DMCHS is 5.33% higher than that of IJSA-DMCHS. Even though the proposed structure of IJNA yields higher pressure drop penalty, the overall thermal performance factor that balances the influence of heat transfer augmentation and pressure drop penalty still favors the proposed IJNA-DMCHS with nested channels, and it outperforms considerably that of IJSA-DMCHS with straight channels.

Experimental investigation on additive manufactured single and curved double layered microchannel heat sink with nanofluids

Experimental investigation on additive manufactured single and curved double layered microchannel heat sink with nanofluids

Thermal performance enhancement and optimization of double-layer microchannel heat sink with intermediate perforated rectangular fins

In the present work, three-dimensional numerical investigation has been carried out to comprehend the thermohydraulic performance of novel design of double-layer microchannel heat sinks (DL MCHS). Conventional DL MCHS is modified by incorporating intermediate rectangular fin with holes of four distinct shapes namely triangular, rectangular, circular and square having equal perimeter. Series of numerical simulations have been performed for the Reynolds number (Re) ranging from 100 to 400, and uniform heat flux varied from 500 to 2000 kW/m2. Single-phase liquid water with varying thermophysical properties is used as cooling medium. Predicted numerical results confirm that compared to conventional configuration; modified DL MCHS has significantly augmented the heat transfer rate causing average Nusselt number to be increased by ≈ 45–60%. But they also encounter higher pressure drop due to massive flow restrictions prevailing in such configurations. Nevertheless, overall thermal performance of the modified DL MCHS is better than the conventional design. Among all the considered cases, heat sinks with circular and triangular holes consistently show superior thermal performance compared to square and rectangular holes, but it is very marginal of the order of ≈ 2–5%. Analysis of coolant flow behavior reveals that intermediate fins with holes facilitate better fluid mixing and provides staggered flow passages in addition to thinner boundary layer which keeps on re-evolving. All these favourable flow behaviors led to improve the heat transfer rate in modified DL MCHS. Furthermore, optimization study of the heat sink with circular holes identify that a configuration with hole radius (Rh) = 0.286 mm and number of holes (Nh) = 15 is superior which exhibits maximum heat transfer rate ≈51–64% higher than conventional DL MCHS.

The Effect of Geometric Parameters on Flow and Heat Transfer Characteristics of a Double-Layer Microchannel Heat Sink for High-Power Diode Laser.

The effect of the geometric parameters on the flow and heat transfer characteristics of a double-layer U-shape microchannel heat sink (DL-MCHS) for a high-power diode laser was investigated in this work. FLUENT 19.2 based on the finite volume method was employed to analyze the flow and heat transfer performance of DL-MCHS. A single variable approach was used to fully research the impact of different parameters (the number of channels, the channel cross-sectional shape, and the aspect ratio) on the temperature distribution, pressure drop, and thermal resistance of the DL-MCHS. The rectangular DL-MCHS heat transfer performance and pressure drop significantly increased with the rise in the channel's aspect ratio due to there being a larger wet perimeter and convective heat transfer area. By comparing the thermal resistance of the DL-MCHS at the same power consumption, it was found that the rectangular DL-MCHS with an aspect ratio in the range of 5.1180-6.389 had the best overall performance. With the same cross-sectional area and hydraulic diameter (AC = 0.36 mm, Dh = 0.417 mm), the thermal resistance of the trapezoidal microchannel heat sink was 32.14% and 42.42% lower than that of the triangular and rectangular ones, respectively, under the condition that the pumping power (Wpp) was 0.2 W. Additionally, the thermal resistance was reduced with the increment of the number of channels inside the DL-MCHS, but this would induce an increased pressure drop. Thus, the channel number has an optimal range, which is between 50 and 80 for the heat sinks in this study. Our study served as a simulation foundation for the semiconductor laser double-layer U-shaped MCHS optimization method using geometric parameters.

Thermofluids performances on innovative design with multi-circuit nested loop applicable for double-layer microchannel heat sinks

This study numerically proposes a novel microchannel heat sink design named multi-circuit nested loop (ML) to strength the thermal performance of double-layer microchannel heat sinks (DMCHS). The ML is introduced into the DMCHS to enhance the thermal characteristics and is compared with the traditional straight DMCHS. Due to the complexity of the ML-DMCHS, 4 different working conditions on inlets and outlets are designed to find the optimal one. Based on the analysis of the thermal gradients on substrate, flow characteristics of coolant, overall thermal resistance and thermal performance factor, it is found that the novel ML-DMCHS not only can significantly reduce the peak temperature, but also offer better temperature uniformity on substrate. The peak temperature on substrate can be reduced up to 34 K when compared with traditional parallel straight double-layer microchannels (P-DMCHS). Furthermore, the inner cooling circuit in ML-DMCHS shows greater impact on the lowest temperature on substrate, while the outer cooling circuit affects more on the peak temperature.

Truncated Double Layer Microchannel Heat Sink and Its Performance Improvement by Implicating Secondary Channel Combined along with Appropriate Cavities and Ribs in Channel Flow

The reliability of double layer microchannel heat sink can be upgraded if the top liquid channel is made shorter or truncated. Because heating effect on the bottom channel coolant caused by top the channel’s hot coolant is relieved for truncated double layer microchannel heat sink. In the present study, the performance parameters of truncated double layer microsinks have been improved by utilizing secondary sub-channel, appropriate cavities, and ribs in their flow channels. In the primary analysis, before utilizing appropriate secondary sub-channel, cavities, and ribs, truncation effect of the upper channel is evaluated by varying design variable, i.e., truncated length ratio from 0.5 to 1, where truncated length ratio = 0.8 has been found as optimum value. In the second analysis, the design variable, i.e., cavity width–depth ratio of 2.4, 3.2, 3.6 for the optimally truncated double layer microsinks possessing secondary channel, cavities, and ribs, are compared. In this study of total eight cases, 43% and 29% enhancement in Nusselt number ratio and thermal performance factor respectively are optimally predicted in the heat sink designs by implicating the appropriate secondary channel, cavities, and ribs into the flow channel.

Parametric study for optimizing double-layer microchannel heat sink for solar panel thermal management

The most significant issue affecting the electric efficiency of solar panels is overheating. Concentration photovoltaic (CPV) modules work by converting approximately 80% of sunlight to heat; this may exceed the cell operating temperature limits. Therefore, thermal management is the best choice for keeping such panels working under specified conditions. Prior to producing an actual solar indoor unit, the current research primarily focuses on optimizing the heat sink dimensions that affect the cooling performance of the solar panel. Two parametric studies were employed to optimize the microchannel heat sink design. First, a two-dimensional numerical study was implemented to optimize the best channel height for more uniform flow inside a double-layer microchannel heat sink (DL-MCHS); the width of channels was kept as a constant value. Second, a three-dimensional conjugate heat transfer model for fluid flow in the optimized heat sink was used to optimize the inlet/outlet header length. To evaluate the overall CPV performance, a further numerical case study was carried out for the optimized designs at a wide range of inlet mass flow rates and steady-state heat flux. The findings indicated that a channel height of 0.5 mm and a header length of 20 mm were the best design points for the suggested heat sink. To assess the effectiveness of a solar/thermal module, the selected design points were applied to a 3D model. The maximum electricity efficiency measured was 17.45%, nearly 40% greater than the typical CPV/T system.

Numerical Study of Thermal Enhancement in a Single- and Double-Layer Microchannel Heat Sink with Different Ribs.

In this paper, a microchannel heat sink model was proposed to realize single- and double- layer flow through built-in ribs. The finite element volume method was used to analyze the influence of the length, thickness and angle of the inner rib on the flow and heat transfer characteristics of the microchannel heat sink. The pressure drop, temperature field, flow field, and thermal characteristics are given. The numerical simulation results show that the rectangular rib plate makes the fluid in the microchannel heat sink flow alternately in the upper and lower layers, which can effectively enhance heat transfer. However, with the increase in rib length, the comprehensive evaluation factor decreases. The change of the angle of the rectangular rib plate has little influence on the Nusselt number. The change rate of the comprehensive evaluation factor of the thickness of the rectangular rib plate is the largest. When the Reynolds number is 1724, the comprehensive evaluation factor of Case 9 is 4.7% higher than that of Case 2. According to the parameter study of the built-in rib plate, the optimal parameter combination is given, in which the angle is 0°, the length is 7.5 mm, and the thickness is 0.2-0.3 mm.

Interplay of wettability and confinement enhancing the performance of heat sinks

• Tapered Double layer heat sink performance is enhanced by modifying surfaces (slip). • Value of slip length has been obtained using Molecular Dynamics simulation. • Analysis has been done based on both the first law and the second law of thermodynamics. • Entropy generation rate due to changes in kinetic energy has been introduced. • The optimal design of a double-layer microchannel heat sink has been obtained. Engineering microchannel heat sinks can help to develop compact and highly efficient cooling systems for electronic devices. In the present study, we demonstrate the coupled effect of surface modification and confinement on the performance of Double Layered Microchannel Heat Sink (DL-MCHS). The effect of wettability is incorporated using interfacial slip obtained from Molecular Dynamics (MD) simulations performed for various wettabilities, and the effect of confinement, through varying tapering degrees, is directly embodied in the geometry. The coupled transport equations are solved using the Finite Element Method (FEM) to depict the thermo-hydraulic characteristics of DL-MCHS. We quantified the enhancement in hydraulic performance and thermal performance of DL-MCHS with varying degrees of surface modification and varying tapering. For the first time, we demonstrate a regime where thermal and hydraulic performances can be enhanced simultaneously in tapered DL-MCHS thereby, making the configuration a viable heat sink system. Also, for the first time, we perform an entropy generation rate analysis in tapered DL-MCHS and demonstrated ways to reduce irreversibility making it a thermodynamically advantageous system, and following that perform an all parameter optimization study. We show that by tuning the tapering factor and interfacial characteristics, the performance of the heat sink can be adjusted for the best performance. The present study will provide helpful guidelines in designing viable heat sinks or exchangers with smart surfaces for electronics cooling and associated applications.

A narrow shape double-layer microchannel heat sink (DL-MCHS) designed for high-power laser crystal

• A narrow shape DL-MCHS is designed for the small-size high power laser crystal. • The multi-layers are inner-soldered to enhance the vertical heat transfer rate. • Extension of DL-MCHS in the length enhances the overall heat transfer capability. • Heat diffusion reduces the influence of fluid flow rate ratio in the two layers. • The DL-MCHS exhibits a low pumping power. The thermal effect-induced problem has become a bottleneck in high power laser systems. The laser crystal, which dissipates a heat flux over 150 W/cm 2 , is the most challenging component when considering the solution of the thermal problem. In this work, we designed a double-layer microchannel heat sink (DL-MCHS) for the heat release of a small-size laser crystal. The main constraints, including the high power density of the laser crystal, space restriction, and the fabrication method are taking into account. A narrow shape DL-MCHS is proposed. The microchannels are fabricated micro-mechanically, and the layers of the DL-MCHS are welded together using a vacuum brazing method. A systematic experimental study is performed to evaluate the performance of the DL-MCHS. The results show that the narrow shape DL-MCHS, which extends the volume only in its length, shows good heat transfer capability. The overall heat transfer coefficient reaches 42 × 10 3 W/(m 2 ·K). The surface temperature of the heating source is well controlled below 55 °C at a typical heat power of 234 W. When the same fluid flow rates are adopted in the two microchannel layers, the first microchannel layer (bottom) absorbs two thirds of the total heat, while the rest is absorbed in the second layer (top). In the solid base of the DL-MCHS, thermal resistance in the vertical direction is over three times that in the longitudinal direction. When the fluid flow ratio in the first microchannel layer increases, the overall heat transfer coefficient is enhanced slightly, while the temperature distribution on the heating head is little affected. Comparing the single-layer cooling pattern, the double-layer flow pattern improves the uniformity of temperature distribution on the heat sink when the counter-current flow is used, and saves the pumping power by up to 60%.

Thermal performance of double-layer porous-microchannel with phase change slurry

Combining porous media paved on sidewall and microencapsulated phase change material (MPCM) suspension as coolant is presented in double-layered microchannel heat sink (MCHS), in which more surface area of porous copper matrix with high thermal conductivity as well as greater temperature difference between the heating wall and working fluid during phase transition of MPCM will enhance heat transfer. The Forchheimer-Brinkman-Darcy model together with energy equation in local thermal equilibrium are employed to deal with fluid flow and heat transfer in porous ribs, and the equivalent heat capacity method is used to describe the phase change process of microcapsules under laminar flow. The influences of coolants, heat sink designs (including the thickness, height, porosity and pore size of porous medium as well as channel number) and working conditions (involving inlet velocity, heat flux and suspension concentration) on thermal and hydraulic characteristics are numerically investigated. The performance evaluation factor (PEF) is introduced to evaluate the comprehensive thermal–hydraulic performance of double-layered MCHS, and the effective performance evaluation factor (PEFeff) is used to compare the overall performance of porous-wall MCHS between conventional arrangements, different channel aspect ratio and channel height ratio configurations. The thickness and height of porous media paved on sidewall should be adjusted reasonably, especially for the arrangement of non-equal porous media, to obtain better overall performance. Different from the variable porosity configuration, the double-layered MCHS cannot rely on losing part of flow performance to obtain better thermal performance in smaller pore size mode, so a larger pore size can be selected to obtain better thermal–hydraulic performance according to actual working conditions. The PEF at larger flow velocity decreases due to higher pressure drop exceeding the benefit of more convection on heat transfer enhancement, in which case the phase change effect in porous-wall mode with MPCM suspension as coolant is suppressed and higher viscosity amplifies the effect of frictional resistance, resulting in a greater drop ratio of PEF than water. The greater PEF in porous-wall MCHS with suspension concentration increasing from 3% to 20% arises than that in non-porous mode, due to the larger surface area of copper matrix with high thermal conductivity and more MPCM particles available for phase transition. The larger aspect ratio configuration can achieve greater PEFeff rise and better overall performance by optimizing fluid velocity in the current mode due to greater thermal resistance drop and less pressure drop rise at lower flow rates, but the variable height ratio structure makes the comprehensive performance of porous-wall MCHS inferior to conventional arrangement due to larger pressure drop rise outweighing the benefits of heat transfer enhancement at the same total volume flux.

Thermohydraulic Performance Intensification of Wavy, Double-Layered Microchannel Heat Sink with Height Tapering

Thermohydraulic performance analysis of a wavy, tapered, double-layered microchannel heat sink is done numerically. The coolant used is water with temperature-dependent properties in single-phase flow considering Reynolds number in the range of 100–500. Uniform heat flux at the base of the microchannel heat sink is applied. The study suggested that the tapered, wavy channel has given better thermal performance than the straight, wavy channel; however, pressure drop has increased. Also, a comparison with a smooth, tapered, double-layered microchannel heat sink showed 13.6% enhancement on overall performance with wave , , Reynolds , and tapering when all three plates of the double-layered microchannel heat sink are considered wavy. Moreover, it has also been observed that considering only the middle plate wavy, the cost of fabrication could be minimized and still similar enhancement over a smooth, double-layered microchannel heat sink could be obtained.