Manifold Microchannel Heat Sink Research Articles

Experimental investigation of heat transfer and pressure drop in copper manifold microchannel heat sinks

Over the past decade, various two-phase cooling solutions have been implemented to dissipate power in high heat flux electronic components. The manifold microchannel heat sink is an efficient thermal management solution that reduces heat resistance while also limiting the pumping power. However, there is limited work available on small form factor manifold microchannels with traditional heat sinking materials like copper. In this study, an experimental investigation is conducted to evaluate the heat transfer and pressure drop performance of copper manifold microchannel heat sinks using an environmentally friendly refrigerant, R1233zd(E), as the working fluid. A microchannel plate and a manifold plate, both made of oxygen-free copper, are sandwiched together to form the manifold microchannel test sample assembly. To compare the effects of geometric parameters, a total of six manifold microchannel test samples are investigated, including two types of manifold plates and three types of microchannel plates. The experiments are performed with refrigerant mass flow rates ranging from 5 to 15 g/s and inlet subcooling temperatures ranging from 3 to 10 K. The heat transfer coefficient increases with a decreasing number of manifolds and with an increase in the number and width of the microchannels. The pressure drop decreases in configurations with more microchannels, more manifolds, and larger microchannel widths. Compared to traditional microchannels, manifold microchannels significantly reduce the total pressure drop. However, their heat transfer performance at higher heat flux conditions is limited by the trapped bubbles phenomena. In comparison to traditional microchannels, manifold microchannels demonstrate much higher performance in dissipating the same amount of heat flux while limiting pumping power, as indicated by the COP.

An innovative manifold microchannel heat sink for thermal management of high-power chips with multiple hotspots

In this study, we propose an innovative manifold microchannel heat sink (MMCHS) featuring perforated baffle structures, which is specifically engineered to address the thermal management challenges associated with chips that exhibit multiple hotspots. By enhancing the conventional Z-shaped MMCHS, we designed a cost-effective and efficient cooling solution tailored specifically for precise temperature regulation across multiple hotspots. We employed numerical simulation techniques to analyze the flow dynamics and heat transfer properties of the optimized manifold microchannel heat sink (OMMCHS) across various baffle configurations and perforation densities. The findings reveal that the OMMCHS significantly outperforms the traditional Z-shaped MMCHS, establishing it as a superior option for cooling of high-power chips with multiple hotspots. Notably, the OMMCHS configuration equipped with I-type baffles and a 50% perforation rate yields the most favorable results, ensuring temperature homogeneity across the hotspots at an inlet velocity of 1.9 m/s. Compared to the MMCHS, the OMMCHS reduces pump power consumption by up to 77.8% while maintaining the same peak temperature, highlighting its efficiency and effectiveness in thermal management.

Numerical study on a new manifold ring-shaped microchannel structure for circular heat source with excellent temperature uniformity

The manifold microchannel heat sink shows great potential for cooling high-heat-flux electronic equipment owing to its exceptional thermal and flow performance. A new manifold ring-shaped channel design is introduced to improve the temperature uniformity for circular heat sources. A comparative analysis of the manifold straight channel, radial expansion channel and manifold ring-shaped channel designs is conducted based on the same heating area under equal mass flow conditions by numerical investigation using single-phase de-ionized water. The findings indicate that the newly proposed manifold ring-shaped channel design exhibits a lower maximum temperature, a lower average temperature, a better temperature uniformity and a smaller pressure drop in comparison to the straight channel and radial channel designs. Specifically, at a mass flow rate of 2.5 g/s, the ring-shaped channel design demonstrates a 71.4 % and 45.4 % reduction in the temperature difference between the maximum temperature and the minimum temperature of the heating surface, and the coefficient of performance is enhanced by 458.2 % and 169.7 % when compared to the straight channel and radial channel designs, respectively. Additionally, three improved designs based on the original manifold ring-shaped channel design are proposed to further enhance fluid flow distribution in the ring-shaped channel design. The results reveal that all three manifold ring-shaped channel optimizations further lower the maximum temperature, the average temperature and the temperature difference. Notably, the improved case3 exhibits the best thermal and hydraulic performances among all structures. When compared to straight channel and radial channel designs, the improved case3 demonstrates an 86.9 % and 75.0 % reduction in the temperature difference, and an increase of 201.2 % and 523.4 % in coefficient of performance under the equal mass flow comparison basis. A heat flux of 1200 W/cm2 can be dissipated at 6 g/s when the maximum temperature rise is kept below 60 K, with a pressure drop of 38 kPa.

Single-phase and flow boiling heat transfer characteristics in staggered finned manifold microchannel heat sink

The investigation of staggered finned manifold microchannel (MMC) for addressing thermal management challenges in high heat flux electronic devices presents promising insights. The research indicates that staggered finned MMCs exhibit superior heat transfer characteristics in comparison to traditional rectangular microchannels, particularly under single-phase flow conditions. When staggered finned microchannels reduce the maximum temperature of the heating surface by around 10 K, the pressure drop is reduced by 1.3 kPa. Notably, as the heat flux escalates, the advantages of staggered finned MMCs become increasingly pronounced, while higher flow rates lead to a gradual diminishment of these advantages. Furthermore, in scenarios involving flow boiling with low heat flux and high flow conditions, staggered finned MMCs demonstrate enhanced heat transfer performance over traditional rectangular microchannels. When staggered finned microchannels reduce the maximum temperature of the heating surface by around 3 K, the pressure drop is improved by 1.2 kPa. Moreover, the study underscores that at lower flow rates, staggered finned MMCs experience a reduced pressure drop relative to traditional rectangular microchannels, whereas at higher flow rates, this trend is reversed. These findings carry significant implications for the optimization of thermal management strategies for electronic devices operating under high heat flux conditions.

Thermal-hydraulic performance of an imperfectly bonded ultrathin manifold micro pin-fin channel heat sink

This study numerically investigated the thermal-hydraulic performance of an ultrathin manifold microchannel heat sink (MMHS) and an ultrathin manifold micro pin-fin channel heat sink (MMPF-HS) with gaps between the manifold and microchannel layers. Unlike previous researches, the effect of the presence of gaps on flow distribution and overall heat transfer of MMHS and MMPF-HS was analyzed. The simulation results show that the presence of the gap significantly affect the heat transfer of both heat sinks but have minimal impact on pressure drop. For the MMHS with a gap of 0.05 mm in height, the bypass effect introduced by the gaps makes the uneven flow distribution worse and causes the formation of low-speed vortexes, leading to a 25.5% increase in the average temperature and 2.1-fold increase in the temperature non-uniformity of the heating surface. MMPF-HS is more effective in mitigating the effect of gap on temperature non-uniformity compared to the original MMHS due to the structural optimization. For the MMPF-HS with a 0.05 mm height gap, the average surface temperature rises from 34.3 to 40.9 °C, and the temperature non-uniformity increases from 1.1 to 5.5 °C, which remain significantly lower than those of the original MMHS without a gap.

Multi-objective parameter optimization design of tapered-type manifold/variable cross-section microchannel heat sink

Manifold microchannel heat sinks (MMCHS) have been widely used in the thermal management of high heat flux electronic devices. To improve the temperature uniformity of MMCHS and reduce the hot spot temperature, a tapered-type manifold/variable cross-section microchannel heat sink (TMVC-MCHS) is proposed in this study. Key parameters affecting the heat transfer performance of TMVC-MCHS were first investigated numerically. The results indicate that the width inclination ratio (αw,in) of the inlet manifold has a greater influence on the coolant flow distribution than the height inclination ratio (αh,in), with a ratio of more than 2.5. In addition, the microchannel inclination (β) and width ratio (ε) affect significantly the fluid flow and heat transfer. To further improve the cooling effect of the heat sink, this study adopted XGBoost and multi-objective genetic algorithm (NSGA-II) to optimize the structure. The maximum temperature of the substrate (Tmax) and the total pressure drop (ΔP) are the optimization objectives. Besides, the compromise solution (αw,in = 0.40, β = 0.63 and ε = 0.52) was determined by TOPSIS combined with the entropy weight method which was validated by the CFD method with an error margin of only 3 %. Finally, Compared to MMCHS, the temperature field distribution uniformity of TMVC-MCHS is significantly improved. The maximum bottom surface temperature is drastically reduced from 337.79 K to 320.01 K, and the temperature difference is reduced from 17.5 K to 3.5 K, at the cost of only a 3.5 kPa pressure rise. For inlet flow rates ranging from 1 m/s to 2.5 m/s, the TMVC-MCHS exhibits a hydrothermal performance factor (PEC) improvement of over 35 %, indicating superior comprehensive performance.

Self-driven manifold microchannel heat sink for cooling electronics

The advancement of passive, compact, and lightweight thermal management technology for high-power chips is essential for the stable and efficient operation of the next generation of electronic devices. A novel self-driven heat sink based on embedded manifold microchannel heat dissipation technology is proposed, which uses capillary force as the driving force to replace the pump, and minimize pressure drop and thermal resistance between the heat sink and heat source. This design of the embedded self-driven manifold microchannel heat sink allows for the integration and miniaturization of the heat sink and the chip heat source. Through Micro Electromechanical Systems technology, an experimental sink with microchannels with a high aspect ratio was fabricated. A theoretical model is constructed to analyze the influence of the width and depth of the microchannel on the limit heat flux, and the correctness of the model is verified by experiments. The results indicate that the width has a more significant impact on the limit heat flux compared to the depth. An optimal width of 6.5 μm is identified. As the depth increases, the influence of depth on the limit heat flux diminishes. By conducting theoretical calculations on the embedded self-driven manifold microchannel heat sink, it was determined that the device using HFE7100 as the working fluid demonstrates a wider heat load range than ethanol and acetone, and the limit heat flux can reach 41.5W/cm2.

Optimization of Manifold Microchannel Heat Sink Based on Design of Experiment Method

Abstract The manifold microchannel heat sink (MMCHS) shows high potential to cope with the rapidly increasing power density of electronic devices. It is of significance to search for an optimization method to comprehensively consider multiparameter effects on the performance of microchannel. Here, we have studied the temperature and flow characteristics of the MMCHS via experimental method. Then, the effect of geometric parameters including microchannel aspect ratio (α), hydraulic diameter (Dh), and manifold block numbers (Nm) on the performance of a MMCHS were studied by numerical method. Subsequently, the design of experiment (DOE) method was proposed to optimize the geometric parameters of the MMCHS. The relation of friction coefficient and heat transfer coefficient with respect to the three geometric parameters was gained by the mathematical regression model. The statistically optimized manifold microchannel achieved a 10.0% reduction in temperature rise, 59.9% enhanced in the heat transfer coefficient, and the figure of merit (FOM) of 1.6. Our work shows a novel method to consider the effect of structure parameters on the performance of the manifold microchannel and provides a novel optimization design method for the manifold microchannel.

Liquid metal manifold microchannel heat sink for ultra-high heat flux cooling

Advanced heat dissipation technology is crucial for chip operation and performance utilization. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, hindering the advancement of its cooling technology. To address this, a liquid metal manifold channel structure is proposed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm2, ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. Orthogonal experiments analyzed the impact of structural parameters on dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. The height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of liquid metal's lower specific heat capacity, enabling efficient thermal management for electronic devices under ultra-high heat flux conditions.

Performance Improvement of Z-Type Manifold Microchannel Heat Sink with Novel Fin-Arrangements

The Z-type manifold microchannel heat sinks are mostly used by researchers due to the simple structure and considerable heat transfer performance. In this study, a novel Z-type manifold microchannel heat sink with fins arranged at intervals in an arithmetic sequence is proposed to improve the thermo-hydraulic performance of the conventional Z-type manifold microchannel. The novel feature of the proposed design is the channel widths being in an arithmetic sequence with a negative common difference, which contributes to equalize the flow distribution among the channels. Various fin arrangements with different common differences under the same heat transfer area are numerically investigated to determine the thermo-hydraulic performance. The results show that the fins arranged at intervals in an arithmetic sequence have a great potential in mitigating the flow maldistribution. Compared to the conventional manifold microchannel, the proposed manifold microchannel has better thermal performance without a significant increase in pressure drop.

Experimental study of embedded manifold staggered pin-fin microchannel heat sink

High-heat-flux thermal management of high-power chips in electronic devices is becoming more and more critical. Manifold microchannel heat sink is one of the effective choices. In order to improve the heat dissipation capacity of manifold microchannel heat sink, a silicon-based thermal test chip including staggered pin-fin microchannels is designed and fabricated. Staggered pin-fin microchannels and rectangular microchannels with the same area size are embedded on the opposite side of the silicon-based thermal test chip for liquid-cooled heat dissipation. The experiments are conducted using HFE7100 as the working fluid. The heat transfer performance and the flow characteristic of two distinct microchannel structures are evaluated. It is found that the differences in temperature, convection heat transfer coefficient and pressure drop caused by different microchannel structures are greatly related to the mass flow rate. The heat transfer performance of the staggered pin-fin microchannel heat sink is better than that of the rectangular microchannel heat sink at a larger mass flow rate, but it also brings greater flow pressure drop. The bubble effect caused by the transition from single-phase to two-phase flow in microchannels makes the monotonicity of the convection heat transfer coefficient decrease significantly and the monotonicity of the pressure drop increase significantly. Compared to rectangular microchannel heat sinks, staggered pin-fin microchannel heat sinks reach the two-phase flow at higher heat flux. At the mass flow rate of 5 mL/s and the heat flux of 700 W/cm2, the staggered pin-fin microchannel heat sink can reduce the chip surface temperature by 8 K compared with the chip surface temperature of the rectangular microchannel heat sink.

Topologically optimized manifold microchannel heat sink with extreme cooling performance for high heat flux cooling of electronics

The manifold microchannel heat sink (MMCHS) has become one of the most promising cooling solutions for high heat flux electronics due to its lower pressure drop and higher temperature uniformity compared to the traditional microchannel heat sink (MCHS). However, the microchannel configurations in previous MMCHS are dominated by parallel, straight microchannels, which would limit their further enhancement in cooling performance. In this work, we designed the microchannel configuration in the MMCHS using a topology optimization method and proposed a manifold microchannel heat sink with a topologically optimized microchannel substrate (MMCHS-TOMS). The thermohydraulic performance of the MMCHS-TOMS was experimentally and numerically studied. The results showed that the microchannel configuration with optimal cooling performance is achieved at a width ratio of inlet to outlet (Win/Wout) = 0.5 and inlet pressure (Pin) = 10 Pa. The MMCHS-TOMS demonstrates a uniform flow distribution in adjacent arrays, and the discrepancies of volumetric flow rate (V̇d) among all inlets are less than 6 %. The MMCHS-TOMS is capable of removing 1570 W/cm2 heat flux under a footprint area of 42 × 10.5 mm2 with a pressure drop of 11.9 kPa, in which the volumetric flow rate and inlet temperature are 3 L/min and 293 K, respectively. With a volumetric flow rate of 1 L/min and a heat flux of 687 W/cm2, the MMCHS-TOMS achieved a maximum cooling coefficient of performance (COP) of 78273, which is the highest value reported up to date. Moreover, oscillations in temperature (mild) and pressure drop (large) are observed in the MMCHS-TOMS when violent boiling occurs; the system stability caused by those oscillations can be suppressed via increasing the volumetric flow rate, although the COP would thus be reduced.

Study on single-phase and two-phase flow and heat transfer characteristics of HFE-7100 in manifold microchannel heat sink with corrugated bottom

To solve the problem of high heat flux heat dissipation in microelectronic devices, a manifold micro-channel heat sink with corrugated bottom (CB-MMC) is pro-posed on the basis of the manifold microchannel heat sink (MMC). The flow and heat transfer characteristics of HFE-7100 in MMC and CB-MMC are investigated numerically. The results show that CB-MMC reduces the pressure loss and enhances the heat transfer performance in single-phase flow. The orthogonal test method is used to obtain structural design solutions with optimal thermal performance. It is observed that the temperature reduction is always at the expense of the increase of the pressure drop. In addition, the optimization parameters combination obtained through comprehensive evaluation of temperature and pressure drop through weight matrix ? optimized solution 19 (wavelength A = 800 ?m, am-plitude B = 40 ?m, channel depth C = 180 ?m, outlet width D = 300 ?m, channel width E = 25 ?m). Its Tave has decreased by 6.89?C, ?P decreased by 10.27 kPa. Moreover, the subcooled boiling flow and heat transfer performance in MMC and CB-MMC are comparatively studied. The results demonstrate that the dynamic behavior of vapor bubbles causes large pressure fluctuations, which further leads to small temperature fluctuations, and thus reduces the stability of the flow and boiling heat transfer. Compared with MMC, CB-MMC exhibits more stable two-phase flow and better boiling heat transfer.

Experimental study on the flow and heat transfer characteristics of pin-fin manifold microchannel heat sink

A manifold microchannel radiator with a cylindrical pin-rib microchannel is designed and fabricated to enhance the heat dissipation capability of the manifold microchannel radiator, and its flow and heat dissipation capability are investigated by experiments. The fabrication and experiment of the manifold pin-rib microchannel radiators are introduced in detail. The heat dissipation capability of manifold pin-rib microchannel radiators at different flow rates is compared. The result shows that the manifold pin-rib microchannel radiator has excellent heat dissipation performance. When HFE7100 is used as the working medium, the average heated surface temperature of the manifold pin-rib microchannel radiator is about 100°C at the thermal flux density of 1000 W/cm2.

Thermal-hydraulic characterization of manifold microchannel heat sink with diverging channels and uniform heating

This study presents the design and experimentation of a manifold microchannel heat sink with diverging channels, employing ammonia as the working fluid to evaluate its thermal–hydraulic performance under uniform heating conditions. The impact of heat flux, inlet subcooling, saturation temperature, and outlet thermodynamic quality were investigated. Under single-phase conditions, the heat sink exhibited low sensitivity to variations in heat flux with constant thermal resistance and pressure drop. However, with the onset of boiling, the heat transfer capability and pressure drop rapidly increased. A lower inlet subcooling boosted boiling inside the heat sink, leading to decreased thermal resistance and increased pressure drop. Under near-saturated inlet conditions, a higher saturation temperature enhanced heat transfer owing to smaller bubble nucleation and detachment size. The outlet thermodynamic quality for engineering applications should be moderately low because it provides a balance between high heat transfer capability and low pressure drop. Moreover, the results demonstrated excellent thermal–hydraulic performance, with a heat flux of up to 636.9 W/cm2 efficiently dissipated under uniform heating conditions while maintaining the heating surface temperature and pressure drop below 79.3 °C and 150.3 kPa, respectively.

A numerical investigation of the thermal–hydraulic performance during subcooled flow boiling in MMCs with different manifolds

Thermal management of high-heat-flux electronics has been a critical bottleneck for integrated circuit miniaturization and increased power density, and manifold microchannel (MMC) heat sinks are expected to be an efficient near-junction thermal solution. A numerical investigation based a self-developed solver has been conducted to explore the effects of manifold geometries on the thermal–hydraulic performance of MMC heat sinks during subcooled flow boiling, and phase, pressure, and mass distribution among microchannels are analyzed combined with temperature distribution. Heat flux makes little difference on the mass maldistribution among microchannels of MMCs regardless of single-phase and flow boiling, and flow patterns in the outlet manifolds of Z-type MMCs changes from bubbly flow, slug flow to vapor columns with segmented bubbles with increasing heat fluxes. As for the effect of manifold numbers, both the maximum temperature and the pressure drop decrease with increasing manifold numbers, and a relatively uniform distribution of mass and void fraction has been found for all cases of HU-type MMCs regardless of heat fluxes with the best thermal–hydraulic performance at N = 10. However, the thermal performance of Z-type MMCs would improve firstly and then flatten out with increasing manifold number, while the pressure drop presents an opposite trend. The differences in thermal–hydraulic performance are attributed to the longer flow path in Z-type manifolds, and the increasing manifold number presents a higher manifold pressure drop and thus would worsen the mass maldistribution. As for tapered manifolds, a tapered ratio of 0.33 could provide a slightly lower base temperature than the original case with a pressure drop decreased by over 25 %, and the pressure drop fluctuation at high heat fluxes could be suppressed by 70 % with significantly improved flow boiling stability. This work can serve as a basis for the further optimization of subcooled flow boiling in MMC heat sinks, and the results indicate that both an even mass distribution among microchannels and a desirable inlet/outlet port ratio for improved flow field are of great importance for the manifold design applied in MMC heat sinks for two-phase heat dissipation.

Influence of restrictor on the thermal-hydraulic performance in manifold microchannel heat sink

Manifold microchannel heat sinks (MMCHSs) are essential in thermal management. Conventional Z-type MMCHS encounter flow maldistribution and large temperature gradients on the heating surface. This work proposes an innovative MMCHS with restrictors to reduce flow maldistribution and compared with other optimization schemes. Through the numerical simulation, we optimize three dimensionless parameters (the width ratio α and length ratio β of the restrictor and inlet-to-outlet width ratio of manifold γ). Introducing the restrictor into the MMCHS can reduce flow maldistribution. In the research scope, the maximum mass flux discrepancy of MMCHS with α = 0.3 decreased from 327.17% to 64.51% compared to MMCHS with α = 1 when the volumetric flow rate is 8.51 mL/min. The reason is that restrictors increase the ratio between pressure drop in microchannels and total pressure drop(Δpc/Δp). Additionally, the coupling effect of the restrictor and γ on thermal-hydraulic in MMCHS are complicated. Therefore, the thermal resistance ratio (Rt/Rt,0), the pumping power ratio (Pp/Pp,0) and performance evaluation criteria (PEC) are taken as references to consider the thermal-hydraulic performance of MMCHS comprehensively. The results display that the MMCHS with α = 0.5– 0.6, β = 0.4 and γ = 0.8– 1 can further control the synchronization of Rt/Rt,0 and Pp/Pp,0 at about 0.75. The PEC values are all greater than 1.59.

Numerical study on temperature distribution uniformity and cooling performance of manifold microchannel heat sink

The manifold microchannel heat sink (MMCHS) is a promising design for cooling electronic devices due to its ability to effectively dissipate high heat flux. The structural changes of the heat sink play a crucial role in achieving uniform heat dissipation and optimal cooling performance. In order to enhance temperature distribution uniformity and cooling performance, this study conducted numerical simulations by introducing flow-regulating baffles between the manifold channels and microchannels. Additionally, two different types of diverging/converging manifold channels, namely horizontal (z direction) and vertical (y direction) diverging/converging manifold channels, were examined. The simulations were performed under single-phase conditions with varying coolant mass flow rates, and various parameters such as flow distribution, pressure drop, thermal resistance, temperature uniformity, and overall heat transfer performance were analyzed. The findings indicate that the modified MMCHS with baffles exhibited improved temperature distribution uniformity at the base of the heat sink and reduced average thermal resistance. However, it was observed that the pressure drop increased in all cases. The MMCHS with baffles demonstrated an average increase of 70.68% in microchannel flow distribution uniformity, an average increase of 44.55% in temperature distribution uniformity at the base of the heat sink, and an average increase of 7.67% in cooling coefficient of performance (COP). On the other hand, the MMCHS with diverging/converging manifold channels in the z and y directions showed an average increase of 81.44% and 83.65% in microchannel flow distribution uniformity, and an average increase of 57.71% and 62.13% in temperature distribution uniformity. However, it was noted that the COP decreased by an average of 14.58% and 29.81% for these cases.

Thermal-hydraulic performance of ammonia in manifold microchannel heat sink

With the increasing miniaturisation of electronic devices, the demand for cooling technologies with high efficiency has increased. Therefore, in this study, a manifold microchannel heat sink was designed and fabricated to enhance the dissipating capability of high-heat-flux hotspots. Owing to its excellent thermophysical properties, ammonia was selected as the working fluid, and its thermal–hydraulic characteristics were evaluated. In addition, the effects of flow rate, heat flux, saturation temperature, and inlet conditions were investigated through experiments. High-subcooled inlet experiments revealed that the thermal resistance decreased and pressure drop increased with increasing flow rate. Moreover, localised subcooled boiling was observed near the heated region. In near-saturated inlet experiments, jet impingement and microchannel cooling were identified as the dominant heat transfer mechanisms over different flow ranges. Notably, the higher heat flux, lower saturation temperature, and two-phase inlet condition reduced the thermal resistance under the operating conditions of the study. The proposed heat sink dissipated the heat flux (up to 1542 W/cm2) from the heat source (1 mm × 6 mm) with a pressure drop of 10.6 kPa, and the corresponding heating surface temperature and thermal resistance were 68.05 ℃ and 0.450 K/W, respectively.

Numerical investigation of novel manifold microchannel heat sinks with countercurrent regions

Manifold microchannel (MMC) heat sink is a potential method to dissipate high heat fluxes of electronic devices. Traditional Z-type MMC is a simple configuration but usually encounters high temperature difference and pressure drop. In this work, we introduced countercurrent flows to alleviate these problems by revising the design of manifold configurations. Six cases with different manifold arrangements are numerically investigated using single-phase deionized water at mass flow rates ranging from 0.04 - 0.12 g/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The cases with countercurrent regions can reduce the maximum temperature around 5 K compared with the original cases with parallel regions. The temperature difference of the ZU-type MMC with double-layer countercurrent flow configuration is lower than 4 K, which is about 25% of the original Z-type MMC. For the revised manifold configuration with countercurrent flows, the pressure drops also decrease due to the split of inlets and outlets of the manifold. The pressure drops of single-layer and double-layer countercurrent manifolds are respectively 27.13% and 33.36% lower than that of the case with traditional Z-type manifold. This leads to a higher comprehensive performance of revised cases with countercurrent flows. Besides the better temperature uniformity, the fluid flow becomes more uniform in the microchannels for the revised case. The improved ZU-type MMC with double-layer countercurrent flow can dissipate 1100 W/cm2 for single-phase flow with a temperature increase of 80 K and a pressure drop of 22 kPa at mass flow rate of 1.2 g/s.