Conventional Microchannel Heat Sink Research Articles

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.

Multimodal machine learning for predicting heat transfer characteristics in micro-pin fin heat sinks

As three-dimensional integrated circuit (3D-IC) chip technology advances, thermal management has become increasingly important because of increasing heat flux from thermal stacking. Micro-pin fin-embedded cooling has emerged as a promising solution for 3D-ICs, offering better thermal and hydraulic performance than conventional microchannel heat sinks. It is also easy to integrate into existing 3D-IC structures, such as through-silicon vias between stacks. The utilization of two-phase flow in micro-pin fins further enhances temperature uniformity and improves the heat transfer coefficient by leveraging latent heat. Nevertheless, predicting thermal performance in micro-pin fin heat sinks under boiling conditions remains challenging owing to intricate geometric shapes and diverse operating conditions. The present lack of correlation or theoretical models poses a significant obstacle. To address this problem, our study employed a Multimodal machine-learning (ML) approach, combining image data capturing boiling patterns of two-phase flow and information about geometric shape and operating conditions, to predict heat transfer characteristics in micro-pin fin heat sinks. We utilized experimental data comprising 155 types of boiling heat transfer data with the dielectric fluid FC-72 in two micro-fin shapes directly etched on Si. Four ML algorithms (XGBoost, LightGBM, Multilayer perceptron (MLP), and Multimodal ML) were employed to predict thermal performance. The correlation coefficient analysis before learning revealed the influence of each type of measurement data on the heater surface temperature during two-phase flow. Prediction accuracy was measured using mean absolute percent error (MAPE), and the results were compared in terms of maximum and average temperature depending on the characteristics of each ML algorithm. Overall, the Multimodal approach demonstrated superior capability in predicting temperature distributions with spatial details, surpassing conventional decision-tree algorithms and MLP in performance. When trained with boiling images, the Multimodal ML model achieved remarkable precision, evidenced by a MAPE of 1.81% for the maximum temperature and 0.84% for the average temperature, highlighting its exceptional accuracy in mapping the heated surface temperature profile. By contrast, the traditional MLP model, which lacked training on boiling images, showed diminished accuracy, with a MAPE of 2.54% for the maximum temperature and 1.77% for the average temperature, indicating a comparative shortfall against the Multimodal model results.

Data center energy efficiency enhancement potential of a membrane-assisted phase-change heat sink

This paper presents the latest progress on characterization of our membrane assisted phase-change heat sinks at conditions suitable for implementation in data centers. Experiments are conducted using water as the working fluid at a saturation pressure of 16 kPa, corresponding to a saturation temperature of ∼55 °C. This temperature is sufficiently lower than the silicon junction temperature of ∼80 °C. As anticipated, the overall performance of the membrane-assisted heat sink at sub-atmospheric pressure is lower compared to analogous tests at atmospheric pressure. In agreement with previous studies on membrane-assisted heat sinks, the critical heat flux limit increases with enhancement of the heat transfer area ratio and liquid space pressure. We report a maximum heat flux of 670 W/cm2 on a surface with enhanced area ratio of 3.45, multiple times greater than the heat fluxes reported hitherto by comparable two-phase heat sinks in literature. Heat transfer coefficients as high as 890 kW/m2-K are obtained. We compare the thermal performance of this device with other existing technologies including conventional microchannel heat sinks, thermosyphons, cold plates, jet impingement, and analyze its system level benefits.

Heat transfer performance study of microchannel heat sink with composite secondary channels

To enhance the performance of microchannel heat sinks, secondary channels or ribs are oftenused separately. However, the synergistic enhancement of heat dissipation by secondary channels and individually composite with different types of ribs and the factors influencing them are not yet clear. In this study, the numerical simulation software ANSYS Fluent is used for simulation and obtaining the optimal microchannel heat sink structure from diamond, rectangular, back triangular, front triangular and elliptical ribs with secondary channel composite. Firstly, the results show that overall performance of microchannel heat sink with front triangular ribs with secondary channel composite is better than other designs. Secondly, the optimized microchannel heat sink with front triangular ribs and secondary channels outperforms the conventional microchannel heat sink by up to 34% in terms of overall performance when Reynolds number is 200, relative rib width/rib length is 0.633/0.400 and relative secondary channel width is 0.600. Finally, by sensitivity analysis, it is found the effect of relative rib width on heat dissipation is about 60%, the effect of flow rate on pressure drop is about 40%, and the effect of overall performance on relative rib width and relative secondary channel width are about 26% and 25%, respectively.

Investigating the effect of the presence of a pulsating heat pipe on the geometrical parameters of the microchannel heat sink

In this study, the effect of the presence of a pulsating heat pipe on the geometrical parameters of the microchannel heat sink will be investigated. The embedding of a pulsating heat pipe (PHP) in the solid part of the microchannel heat sink (MCHS) increases the cooling performance of the MCHS and reduces the maximum temperature of the electronic piece. A numerical investigation of MCHS equipped with a PHP is investigated and compared with an optimized conventional MCHS without PHP. The inverse problem solution approach is used to optimize the geometric parameters of the MCHS. The geometrical variables in the optimization process are N (number of channels), α (aspect ratio of the channel), and β (width ratio of the channel to pitch). The pumping power is considered a constraint and is tried to reach the minimized objective function (thermal resistance (R)). Results show that the optimal values of geometrical and physical parameters change from N = 100, α = 13.9, β = 0.6, R = 0.0268, in conventional MCHS to N = 120, α = 14.3, β = 0.7, R = 0.0231 in MCHS with PHP. At this point, the system’s thermal performance improved by 16.02% compared to the previous optimal state.

Performance Analysis of Hybrid Microchannel Heat Sink for Non-Uniform Heat Fluxes Under Laminar Flow Conditions

Microchannel Heat Sinks (MCHS) are widely used in high heat flux heat transfer applications. They have become indispensable for modern CPU/GPU cooling. Uniform channel-width Rectangular microchannel heat sinks are widely used for their superior performance and easy manufacturability. However, when heat loads are non-uniform, the performance of conventional MCHS is decreased. To solve this problem a MCHS with subchannels is proposed and numerically investigated. Water is considered as the cooling medium and copper as the heatsink material. Numerical simulations were performed in COMSOL Multiphysics software with water mass flow rates in the range of 0.5-2.5 LPM and five different heat fluxes from 100 W/cm2 to 500 W/cm2 were applied for each mass flow rate. Numerical results are validated against standard pressure drop correlations. Case temperature, pressure drop, and pumping power values are compared between Conventional MCHS and subchannel MCHS. Conventional MCHS provides slightly better case temperatures in comparison with subchannel MCHS, however, it is found that Subchannel MCHS gives significant power savings compared to the Conventional MCHS for non-uniform heat loads.

A machine learning approach for predicting heat transfer characteristics in micro-pin fin heat sinks

Micro-pin fin heat sinks are receiving attention for their use in the thermal management of high-heat-flux electronics systems since they can help to enhance heat transfer characteristics (owing to their large extended surface area) and flow mixing while requiring relatively low pumping power compared with conventional microchannel heat sinks. Although many studies have determined the thermal performance of micro-pin fin heat sinks over the past several decades, a universal model for predicting the thermal performance of micro-pin fin heat sinks with various geometries and under different operating conditions has not been developed. In this study, we developed universal machine learning models for predicting the thermal performance of micro-pin fin heat sinks of various shapes and under different operating conditions beyond the limits of existing correlations by using power law regression. The database for these models comprised 906 data points amassed from 15 studies. Three machine learning models and a newly proposed regression model were compared with the conventional regression models. The prediction accuracies of each model and complex relations between the geometric shape, operating conditions, and heat transfer performance are discussed by comparing the three machine learning models and the regression model. The machine learning models had mean absolute errors (MAEs) of 7.5–10.9%, representing an approximately fivefold enhancement in the prediction accuracy compared with existing regression correlations. Their MAEs were lower than that of the regression model. Moreover, the machine learning models provided high accuracies for rare geometric shapes and operating conditions, such as a triangular pin shape or the use of R134A as a working fluid. These results showed the superiority of the machine learning models over traditional correlations in terms of the prediction accuracy for the thermal performance of micro-pin fin heat sinks over a wide range of geometric and operating conditions.

Performance analysis of microchannel heat sink with flow disrupting pins

Study of thermo-hydraulic characteristics of a novel microchannel heat sink having flow disrupting pins is numerically and experimentally carried out in this paper. Cylindrical pins are inserted from top cover into the rectangular microchannel instead of the conventional technique of pin-fins originating from the base of microchannel. Initially, the effect of pin diameter on the thermo-hydraulic performance is studied and the optimum pin diameter is established, later on thermo-hydraulic performance of pin enhanced microchannel heat sink (PE-MCHS) is compared with conventional microchannel heat sink (MCHS). Of the five pin diameters studied, pin having 0.2mm diameter (relative pin diameter γ=0.4) gives the best performance. Both conventional MCHS and PE-MCHS are subjected to heat flux ranging from 65W/cm2 to 200 W/cm2 and cooled by water flowing at Reynolds number ranging from 745 to 1500. The presence of pins disturbs the velocity distribution completely and increases the heat transfer capacity of the MCHS accompanied by higher pressure drop penalty. The average enhancement factor obtained by this technique is 1.24. Correlations showing the effect of channel width to pin diameter ratio (Wc/ Dp) on Nusselt number (Nu)and friction factor (f) are proposed.

Effect of PCM and porous media/nanofluid on the thermal efficiency of microchannel heat sinks

The present study is a genuine attempt to improve the thermal behavior and hydraulic performance of a conventional microchannel heat sink (MCHS) using porous material, phase change material (PCM) and nanofluid. Three-dimensional microchannels with square, circular and flattened circular geometries are examined numerically by considering the thermal conduction in solid parts. Various factors are examined, including the effect of the number of channels, fluid velocity passing through channels, porous substrate thickness, PCM layer thickness, Darcy number, porosity coefficient, thermal conductivity ratio in the porous material, volume fraction and nanoparticle diameter. According to the findings, for a critical thickness of the porous substrate, the thermal performance is at its minimum. With increasing values of Darcy number, porosity coefficient, nanoparticle diameter and PCM thickness, the thermal performance of MCHS decreases. An MCHS with square geometry displays a better thermal performance compared to the other two geometries. Furthermore, the use of porous material, nanofluid and PCM improves the thermal behavior compared with a conventional microchannel. The thermal performance of MCHS with PCM is approximately 47% and 17% higher than that of a microchannel with the porous substrate and a microchannel incorporating a combination of the porous layer and nanofluid.

Effect of circular pin-fins geometry and their arrangement on heat transfer performance for laminar flow in microchannel heat sink

A computational simulation of seventeen types of microchannel heat sink (MCHS) models with the channels equipped with circular pin fins having various diameters (0.25 and 0.5 mm), spacing (1.5, 3.0 and 6.0 mm) and height (0.1, 0.25, 0.4 and 0.5 mm) in order to compare their performance with the conventional MCHS was performed. Mesh independence validation and experiments on MCHS without any pin fins were used to assess the reliability of computer simulation results. The simulation was carried out for five different Reynolds numbers in the range from 100 to 1000. Hydraulic and thermal parameters including pressure drop, Nusselt number and thermal resistance were considered for performance evaluations. To evaluate comprehensive performance, the heat sink effectiveness factor which represents a combination of the hydraulic and thermal performance was defined and corresponding figures were provided to define an optimum geometry. It was observed that thermal resistance substantially depends on the height of the pins: the higher are the pins, the better is the heat flux. The optimal pin placement step sp was revealed as six diameters dp of the pin: sp = 6 dp for the height of the pins hp = 0.1–0.25 mm; for hp = 0.5 mm the effectiveness factor of MCHS has the maximum value at sp = 3 dp.

Numerical assessment on heat transfer performance of double-layered oblique fins micro-channel heat sink with Al2O3 nanofluid

This paper demonstrates a numerical study on heat transfer characteristics of laminar flow in a double-layered oblique finned heat sink using nanofluids with Al2O3 nanoparticles. Micro-channel heat sink with primary channel width of 0.5 mm with aspect ratio of 3 is employed. Instead of having conventional straight fins, oblique fins with narrow secondary channels are used. In this numerical study, single-phase fluid model with conjugate heat transfer is considered. The numerical modeling was first validated with existing data for double-layered conventional micro-channel heat sink having water (base fluid) as the working fluid. Numerical investigations on oblique finned micro-channel heat sink were then conducted for flow rates ranging from 3 ? 10?7 to 15 ? 10?7 m3/s, equivalent to primary channel inlet velocity in between 0.2 and 1.0 m/s. It was found that double-layered oblique finned configuration yields better heat transfer performance, inferred by the lower overall thermal resistance obtained as compared with that of double-layered conventional heat sink. Employing double-layered oblique finned heat sink, the heat transfer performance could be further enhanced, by using nanoparticles that are added into water-based fluid. It is found that the reduction of overall thermal resistance is proportional to the volume fraction of nanoparticles. Using cross-flow double-layered oblique finned configuration, the largest reduction in the overall thermal resistance can reach up to 25%, by using nanofluids with 4% volume fraction of Al2O3 nanoparticles.

A Three-Dimensional Simulation Analysis of Fluid Flow and Heat Transfer in Microchannel Heat Sinks with Different Structures

Abstract Numerical studies have been performed to analyze the fluid flow and heat transfer characteristics of nine microchannel heat sinks (MCHS) with different shapes and different arrangements of the ribs and cavities on the sidewalls, using three common shapes (square, triangle, and circular) of ribs or cavities as the basic structure in this work. The boundary conditions, governing equations, friction factor (f), Nusselt number (Nu), and performance evaluation criteria (ξ) were considered to determine which design was the best in terms of the heat transfer, the pressure drop, and the overall performance. It was observed that no matter how the circular ribs or cavities were arranged, its heat sink performance was better than the other two shapes for Reynolds number of 200–1000. Therefore, circular ribs or cavities can be considered as the best structure to improve the performance of MCHS. In addition, the heat sink performance of the microchannel heat sink with symmetrical circular ribs (MCHS-SCR) was improved by 31.2 % compared with the conventional microchannel heat sink at Re = 667. This was because in addition to the formation of transverse vortices in the channel, four symmetrical and reverse longitudinal vortices are formed to improve the mixing efficiency of the central fluid (low temperature) and the near-wall fluid (high temperature). Then, as the Reynolds number increases, the heat sink performance of MCHS-SCR dropped sharply. The heat sink performance of microchannel heat sinks with staggered ribs and cavities (MCHS-SCRC, MCHS-STRC, and MCHS-SSRC) exceeded that of MCHS-SCR. This indicated that the microchannel heat sink with staggered ribs and cavities was more suitable for high Reynolds number (Re > 800).

ENHANCEMENT IN THERMO-HYDRAULIC PERFORMANCE OF MICROCHANNEL HEAT SINK WITH SECONDARY FLOWS OF LEAF VENATION PATTERN

A new microchannel heat sink (MCHS) design comprising of secondary channels which connect neighboring primary channels are numerically analyzed to study their thermo-hydraulic characteristics. The inclusion of secondary channels in the continuous walls results in disturbance of thermal and hydrodynamic boundary layers which leads to drop in boundary layer thickness. Number of such secondary channel on either side of main channel will cause the flow to be continuously in developing state. The new MCHS are tested for heat flux range of 65 Watt per sq.cm to 200 Watt per sq.cm and cooled by water flowing at Reynolds number ranging from 650 to 1300. Compared to conventional MCHS, the thermal performance of new MCHS is higher but at the cost of pressure drop. The overall enhancement factor of the new design which is a function of Nusselt number and pressure drop of enhanced MCHS and conventional MCHS is 1.4 to 1.85.

Thermal Performance Analysis in Sinusoidal-Cavities-Ribs Microchannel Heat Sink with Secondary Channel Geometry for Low Pumping Power Application

The increases in the demand for high performance electronic device has led cooling technology from air cooling to liquid cooling method in order to prevent the operating temperature in the electronic device goes beyond the junction temperature of the electronic device. Liquid as a heat transportation in a micro-cooling technology is an effective method to maintain the operating temperature. Among the micro-cooling technology, microchannel heat sink appears as a promising method that provides high heat transfer rate with minimal pressure drop. However, the conventional microchannel heat sink which has straight channels (CR MCHS) inadequate to remove high heat flux generated by the current devices due to high thermal resistance in laminar region. High heat transfer rate just can be obtained in the microchannel heat sink by using a large mass flowrate which affects the pumping power consumption. The method is not suitable for the low pumping power application. So instead of increases the mass flowrate, in this paper, a hybrid microchannel heat sink was proposed in order to satisfy the cooling demand with low pumping power consumption. The effect of sinusoidal cavities, rectangular ribs and secondary channel geometry on thermal resistance and pumping power in the hybrid microchannel sink (SD-RR-SC MCHS) was studied numerically. The result showed the SD-RR-SC MCHS and RR MCHS had the lowest thermal resistance and temperature variation for the mass flowrate that less than 6.78×10−5 kg/s. Despite both designs had a similar thermal performance with the average deviation of 5%, SD-RR-SC MCHS required only 11.3% of CR MCHS pumping power, while RR MCHS required 31.3% of CR MCHS pumping power in order to achieve the optimum thermal performance of CR MCHS. Means, SD-RR-SC MCHS is the most suitable design which can fulfil cooling demand for low pumping power application.

Effect of microchannel heat sink configuration on the thermal performance and pumping power

This paper presents a computational modeling of ten different configurations of microchannel heat sink (MCHS) with single phase liquid flow in order to compare their performance with the conventional MCHS. New configurations with a longitudinal and transverse arrangement of microchannels relative to the base plate, different number of coolant passages, cocurrent and countercurrent coolant supply were studied to obtain maximum thermal performance and uniform temperature distribution. The formation of the developing flow zones in a number of new configurations allowed to achieve higher Nusselt numbers and low thermal resistances at the same pumping power in comparison with conventional MCHS. The proposed methods of coolant supply make it possible to reduce the temperature gradients and improve the temperature uniformity on the base due to better distribution of coolant.

Computational analysis of new microchannel heat sink configurations

Computational experiments were carried out on flow and heat transfer in four new microchannel heat sink (MCHS) configurations to compare their performance with the conventional MCHS. The new microchannel heat sinks simulated consist of four compartments with separate coolant inlet and outlet plenum for each compartment. The presence of several regions of developing flow in new designs result in higher Nusselt number and heat transfer rates. The substrate temperature gradients in new configurations are lower than that in conventional MCHS due to better distribution of coolant and recirculation. At the same pumping power, thermal resistances in the new designs are lower than the thermal resistances in conventional MCHS. The design may be further optimized by varying channel dimensions.

Numerical simulations of interrupted and conventional microchannel heat sinks

We provide three-dimensional numerical simulations of conjugate heat transfer in conventional and the newly proposed interrupted microchannel heat sinks. The new microchannel heat sink consists of a set of separated zones adjoining shortened parallel microchannels and transverse microchambers. Multi-channel effect, physical property variations, and axial thermal conduction are considered. It is found that flow rate variations in different channels can be neglected, while heat received by different channels accounts for 2% deviations from the averaged value when the heat flux at the back surface of the silicon chip reaches 100 W/cm 2. The computed hydraulic and thermal boundary layers are redeveloping in each separated zone due to shortened flow length for the interrupted microchannel heat sink. The periodic thermal developing flow is responsible for the significant heat transfer enhancement. Two effects influence pressure drops across the newly proposed microchannel heat sink. The first one is the pressure recovery effect in the microchamber, while the second one is the head loss when liquid leaves the microchamber and enters the next zone. The first effect compensates or suppresses the second one, leading to similar or decreased pressure drop than that for the conventional microchannel heat sink, with the fluid Prandtl number larger than unity.

Experimental investigation of heat transfer performance for a novel microchannel heat sink

We demonstrated a novel microchannel heat sink with a high local heat transfer efficiency contributed by a complicated microchannel system, which comprises parallel longitudinal microchannels etched in a silicon substrate and transverse microchannels electroplated on a copper heat spreader. The thermal boundary layer develops in transverse microchannels. Meanwhile, the heat transfer area is increased compared with the conventional microchannel heat sink only having parallel longitudinal microchannels. Both benefits yield high local heat transfer efficiency and enhance the overall heat transfer, which is attractive for the cooling of high heat flux electronic devices. Infrared tests show the temperature distribution in the test objects. The effects of flow rate and heat flux levels on heat transfer characteristics are presented. A uniform temperature distribution is obtained through the heating area. The reference temperatures decrease with the increasing flow rate from 0.64 ml min−1 to 6.79 ml min−1 for a constant heat flux of 10.4 W cm−2. A heat flux of 18.9 W cm−2 is attained at a flow rate of 6.79 ml min−1 for assuring the maximum temperature of the microchannel heat sink less than the maximum working temperature of electronic devices.

Numerical analysis of heat transfer in a manifold microchannel heat sink with high efficient copper heat spreader

A manifold microchannel heat sink integrated with a high efficient copper heat spreader is presented. A series analysis of three-dimensional fluid flow and heat transfer performance in this mirochannel heat sink and conventional structure are performed by CFX commercial software package. The temperature difference along the flow direction in the new microchannel heat sink is less than that of the conventional microchannel heat sink due to effect of the transverse channel arrays. The maximum heat flux input of the new microchannel heat sink increases 75% more than the conventional structure with the flow rate of 1 m/s. The new design has better heat transfer characteristics than conventional one for the full range of flow rates considered.

Microscale heat transfer enhancement using thermal boundary layer redeveloping concept

We demonstrated a new silicon microchannel heat sink, composing of parallel longitudinal microchannels and several transverse microchannels, which separate the whole flow length into several independent zones, in which the thermal boundary layer is in developing. The redeveloping flow is repeated for all of the independent zones thus the overall heat transfer is greatly enhanced. Meanwhile, the pressure drops are decreased compared with the conventional microchannel heat sink. Both benefits of enhanced heat transfer and decreased pressure drop ensure the possibility to use “larger” hydraulic diameter of the microchannels so that less pumping power is needed, which are attractive for high heat flux chip cooling. The above idea fulfilled in microscale is verified by a set of experiments. The local chip temperature and Nusselt numbers are obtained using a high resolution Infrared Radiator Imaging system. Preliminary explanation is given on the decreased pressure drop while enhancing heat transfer. The dimensionless control parameter that guides the new heat sink design and the prospective of the new heat sink are discussed.