Thermal Performance Of Microchannel Heat Research Articles

Machine learning-based thermal performance study of microchannel heat sink under non-uniform heat load conditions

The parallel microchannel heat sink stands as a pivotal solution in managing high heat flux electronics due to its efficient heat transfer characteristics and ease of manufacturing. While numerous studies have explored the thermal performance and flow characteristics of microchannel heat sinks, most have focused on uniform heat loads or relied heavily on numerical methods. This study presents an experimental system tailored to generate data for analyzing the thermal performance of microchannel heat sinks under various conditions. Leveraging this dataset, four distinct machine learning models Artificial Neural Network (ANN), XGBoost, LightGBM, and K-nearest neighbor (KNN) were trained using 22 input features, totalling 560 data points categorised into geometry parameters, heating patterns, and boundary conditions details. The models were tasked with predicting six response variables: the average base temperature of the heat sink, temperature change (ΔT), hotspot temperature, heat transfer coefficient (h), Nusselt number (Nu), and thermal resistance (Rth). Among the four machine learning models, XGBoost exhibited a good predictive accuracy of an average R2 value of 0.98 and MAE values of 2.1 across all responses. Furthermore, the study delved into the impact of varying input features on prediction accuracy, revealing a consistent enhancement in accuracy with the inclusion of more features across all models.

Numerical Study About Nanofluids of Spherical and Tube-Shaped TiO2 Nanomaterials on the Thermal Performance and Entropy Generation of Different Cross-Section Microchannel Heat Sinks

We numerically evaluated the thermal performance of microchannel heat sinks, considering rectangular, hexagonal, and circular cross-sections. Moreover, as a passive heat transfer augmentation technique, dimples were added to improve the rectangular microchannel heat sinks. These simulations use nanofluids based on TiO2 nanoparticles or nanotubes dispersed in bidistilled water as working fluids. The mathematical model considered variable thermophysical properties of the nanofluids; for this purpose, polynomial fittings correlate the dependence of the thermophysical properties on the temperature. We considered a heat flux of q″ = 50 W/cm2 at the microchannel’s lower surface as a boundary condition along with laminar flow conditions. The numerical simulations allowed the Nusselt numbers and entropy generation calculation, which were the basis for the thermal performance calculation. Regarding the effect of TiO2 nanoparticles shape, spherical TiO2 nanoparticles based nanofluids using rectangular microchannels improve the Nusselt number. Moreover, the frictional entropy decreases with nanofluids based on TiO2 nanotubes, but the thermal entropy decreases with nanofluids based on TiO2 nanotubes. Incorporating dimples in the rectangular microchannel enhances the Nusselt numbers and lowers the entropy generation. Considering the Reynolds number range and from the perspective of Nusselt number and entropy generation, we concluded that the microchannels must be operated at a high Reynolds number to improve the microchannel heat sinks thermal performance.

Numerical analysis on the thermal performance of microchannel heat sinks with Al2O3 nanofluid and various fins

• A single-phase three-dimensional flow model compares different finned microchannels. • The fin shape has significant effects on microchannel heat transfer characteristics. • A zigzag fin gives the highest rate of heat removal to hydraulic power loss ratio. • The zigzag fin gives a 9 K lower contact temperature and 60% higher Nusselt number. • Higher thermal performance is achieved with the Al 2 O 3 nanofluid compared to water. The hydraulic and thermal performance of microchannel heat sink configurations for high performance electronic cooling applications is investigated by numerical modelling. Conjugate heat transfer simulations are obtained through the silicon walls and the fluid domain of a square base prism heat sink traversed by 50 parallel rectangular cooling ducts, under a 150 W/cm 2 constant heat flux input through the base. Al 2 O 3 nanofluid coolant with a nanoparticle volume fraction ranging from 0 to 3% is supplied at 298 K, over the Reynolds number range 100 to 350, modelled as a single-phase homogeneous medium. Rectangular, twisted, and zig-zag fins are inserted into the plain rectangular duct to enhance the heat transfer rate. The zig-zag fin and 3% Al 2 O 3 nanofluid provide the best thermal performance, with a 6.44 K lower average heated wall contact temperature, 60% higher Nusselt number, and 15% higher second law efficiency than without fins and plain water cooling. Twist in the microchannel fin unexpectedly reduced the microchannel pressure drop by 2% to 15% compared to a straight fin, possibly due to the more evenly distributed axial mass flux across the microchannel.

Numerical investigation of the thermohydraulic characteristics of microchannel heat sinks using supercritical CO2 as a coolant

For compact electronic devices, high-pressure drops that characterize microchannel heat sinks (MCHS) is an issue that needs to be resolved to reduce the size of heat-removing systems. In this regard, supercritical carbon dioxide (sCO2) can be of great value due to its favorable thermophysical properties near the critical point. Thus, the potential of the proposed coolant (sCO2) for microchannel heat sinks (MCHS) is numerically investigated and compared with the conventional liquid coolant. Moreover, a header geometry with minimum flow maldistribution is designed for both coolants. Finally, the impact of various operating conditions on the thermal and hydraulic performance of the proposed sCO2-cooled MCHS is investigated to evaluate its optimal operating conditions. To accomplish this, a 3D Reynolds Averaged Navier–Stokes (RANS) model is developed to analyze the thermal and hydraulic performance of both coolants. Thermophysical properties of sCO2 are implemented through a high-resolution real gas property (RGP) file to capture abrupt variations in its properties and ensure the model's precision. Results suggest that replacing water with sCO2 can enhance the thermal performance of microchannel heat sinks by up to 32% at higher flow rates of the coolant, while pressure losses can be reduced by up to 7 times compared to water-cooled MCHS. Moreover, it is found that sCO2-cooled MCHS can maintain a steady base temperature, even during overload conditions. The proposed coolant can be used to design highly efficient and compact cooling systems with the capability of enhancing the MCHS overall performance by up to 2.2 times.

Study on thermal performance of microchannel heat sinks with periodic jetting and throttling structures in sidewalls

An experimental investigation has been carried out to analyze the flow and heat transfer characteristics in the silicon microchannel heat sinks with periodic jetting or throttling structures by using deionized water with flow rates of 28–95 ml/min. The heat sink includes 10 parallel microchannel with 49 identical units (jetting or throttling structures) long the flow direction, width of 100–200 μm, depth of 215 μm. Results show the heat transfer of throttling microchannel heat sink is enhanced obviously albeit with larger pressure drop penalty. It is because that the fluid is completely blocked by the sudden contractible structure, then forms the severe reflux to wash divergent structure and enhance fluid mixing. Compared with jetting microchannel heat sink, the Nuav of throttling microchannel heat sink is improved to 1.56–1.29 times albeit with f increased to 1.84–1.51 times with increasing of flow rates. But the total performance evaluation criterion (PEC) is increased to about 2.5 times. For maximum temperature <60 °C, the required minimum flow rates of throttling microchannel heat sink are reduced obviously. Even the pumping power of that is increased at heater power larger than 50 W, the thermal resistance is reduced severely. It means the throttling microchannel heat sink can meet larger heater power with lower flow rates in application.

A parametric study on thermal performance of microchannel heat sinks with internally vertical bifurcations in laminar liquid flow

The optimal position of internal vertical bifurcation integrated with a microchannel heat sink (MHS) is investigated numerically in the present research. The corresponding rectangular smooth microchannel is compared with those with internal vertical bifurcation. The optimal position along the streamwise direction for interval distances is studied in detail. The corresponding temperature fields, flow fields, pressure drop and thermal characteristics are presented through verified computational model. The numerical simulation indicates that a clear inflection point of pressure gradient may prevail with the presence of internal vertical bifurcation. It is also found that the microchannel heat sink with a small distance between the tail end of internal vertical bifurcation and the outlet of microchannel shows the best thermal performance instead of those with setting the tail end of internal bifurcation at the outlet of microchannel. The proposed optimal design of internal vertical bifurcation shows improved thermal performance without any pressure drop penalty.

Enhanced Thermal Performance of Internal Y-Shaped Bifurcation Microchannel Heat Sinks With Metal Foams

Internal Y-shaped bifurcation has been proved to be an advantageous way on improving thermal performance of microchannel heat sinks according to the previous research. Metal foams are known due to their predominate performance such as low-density, large surface area, and high thermal conductivity. In this paper, different parameters of metal foams in Y-shaped bifurcation microchannel heat sinks are designed and investigated numerically. The effects of Reynolds number, porosity of metal foam, and the pore density (PPI) of the metal foam on the microchannel heat sinks are analyzed in detail. It is found that the internal Y-shaped bifurcation microchannel heat sinks with metal foam exhibit better heat transfer enhancement and overall thermal performance. This research provides broad application prospects for heat sinks with metal foam in the thermal management of high power density electronic devices.

Forced convection and heat transfer of water-cooled microchannel heat sinks with various structured metal foams

The excellent performance of metal foams is well-recognized in the thermal and energy fields. This paper presents an investigation on the convective heat transfer and thermal performance of microchannel heat sinks with different structures of metal foams, such as Y-shaped, metal foam attached to fins, combined metal foams. The inlet Reynolds number is ranging from 170 to 554 and the porosity of the metal foam is ranging from 0.7 to 0.9. The detailed thermal performance and flow characteristics are presented and analyzed by using computational fluid dynamics with a verified computational model. The influences of flow velocity and porosity of the metal foam on the flow and heat transfer characteristics in a microchannel are also observed. It is found that different configurations and locations of metal foam in microchannel result in different heat transfer characteristics. The microchannel heat sinks with combined metal foams have better overall thermal performance than the other two models because it possesses the advantages of mixing fluid flow caused by Y-shaped metal foam and contacting the fins closely. Therefore, properly designed configurations of metal foams can further enhance the microchannel heat sink cooling capacity. Besides, the porosities have a small effect on the thermal performance but have a larger effect on the pressure drop.

Computational optimization of counter-flow double-layered microchannel heat sinks subjected to thermal resistance and pumping power

Various microchannel heat sinks are widely used to cool electronic chips, but they are often designed to be single-layer channels. To a certain extent, single-layered microchannel heat sinks can solve the problem of high heat flux. However, due to the limitation of pumping power, only a small coolant flow rate can be adopted; and the temperature of the heated plate is non-uniform. In this paper, the structure of double-layered countercurrent microchannel heat sinks is designed. The NSGA-II optimization algorithm is used to optimize the height ratio of the two layers and the length of the upper layer. The corresponding Pareto frontier is obtained. After validation of the optimization Pareto front, some validated characteristic cases are investigated numerically. The results of the optimization show that despite a conflict between reducing the thermal resistance and lowering the pumping power, there is an appropriate structure of the double-layered countercurrent microchannel heat sink optimized by the NSGA-II optimization algorithm. For the selected cases, Case 4 has the best thermal performance, because Case 4 not only has a smaller pumping power than Case 0, but also has a smaller thermal resistance than Case 0. Therefore, it is indicated that better thermal performance of microchannel heat sinks can be achieved through the optimization algorithm.

Parametric study on thermal performance of microchannel heat sinks with internal vertical Y-shaped bifurcations

In this paper, internal vertical Y-shaped bifurcation plates are integrated with the microchannel heat sink (MHS), and its corresponding thermal and fluid flow characteristics are investigated numerically. The effect of the length of Y-shaped bifurcation and the angles of the arms on the overall performance are examined. A best Y-shaped plate length are firstly screened out from three designs and are compared with the corresponding rectangular smooth microchannel. Based on the best thermal performance with a specific length, the effect of arm angles in terms of five different configurations of Y-shaped plates are further investigated. Through the calculations, the corresponding flow field, temperature field and pressure drop characteristics are reported. It is found that the thermal performance of MHSs with internal Y-shaped bifurcations is much better than that of the traditional rectangular microchannel. The longest internal Y-shaped bifurcation microchannel results in best thermal performance. On the other hand, a larger arm angle leads to a better thermal performance of the internal Y-shaped bifurcation microchannel.

Constructal Parallel-Flow and Counterflow Microchannel Heat Sinks with Bifurcations

Based on the Constructal Theory, parallel-flow and counterflow microchannels heat sinks with bifurcations are put forward to manage the temperature nonuniformity and further reduce the temperature of microchannel heat sinks bottom plates. Several models with different lengths of bifurcations are designed, and the corresponding laminar fluid flow and heat transfer of all models have been investigated through numerical simulations. The pressure, velocity, temperature distributions, and averaged Nusselt numbers are analyzed in details, and then the overall thermal resistances and overall thermal performance are compared. The results show that the thermal performance of counterflow microchannel heat sinks is better than that of parallel-flow heat sinks for the same geometry, and bifurcation can improve the thermal performance for all cases. It is suggested that a proper design of the length of bifurcation counterflow microchannel can be employed to improve the overall thermal performance of microchannel heat sinks. The study complements and extends previous works.

Laminar thermal performance of microchannel heat sinks with constructal vertical Y-shaped bifurcation plates

With increasing output power of integrated chips, the involved heat flux is accordingly increased. Traditional cooling methods failed to satisfy such a situation, and thus new cooling methods incorporating microchannel heat sinks with high capabilities of heat removal are necessary. In this paper, on the basis of a water-cooled smooth microchannel heat sink, vertical Y-shaped bifurcation plates are designed into the heat sink, and then the corresponding laminar flow and heat transfer are investigated numerically. Four different configurations of Y-shaped plates are considered by adjusting the angle between the two arms of the Y profile. The effects of the angle on heat transfer, pressure drop, and the thermal resistance are also observed and compared with those of the traditional straight microchannel heat sink without bifurcation flow. The overall resistances subjected to inlet Reynolds number and pumping power are also compared for the five microchannel heat sinks. The results show that the thermal performance of the microchannel heat sinks with Y-shaped bifurcation plates is much better than that of the corresponding straight channel. It is suggested that the Y-shaped bifurcation plates placed in water-cooled microchannel heat sinks could improve the overall thermal performance when the angle between the two arms of the Y-shaped plates is designed properly.

Numerical Analysis of Flow and Thermal Performance of Liquid-Cooling Microchannel Heat Sinks with Bifurcation

Single-phase liquid-cooling microchannels have received great attention to remove the gradually increased heat loads of heat sinks. Proper changes of the flow path and/or heat transfer surface can result in much better thermal performance of microchannel heat sinks. In this study, a kind of rectangular straight microchannel heat sink with bifurcation flow arrangement has been designed, and the corresponding laminar flow and heat transfer have been investigated numerically. Four different configurations are considered. The effects of the bifurcation ratio (the initial channel number over the bifurcating channel number) and length ratio (the channel length before bifurcation over the bifurcation channel length) on laminar heat transfer, pressure drop, and thermal resistance are considered and compared with those of the traditional straight microchannel heat sink without bifurcation flow. The overall thermal resistances subjected to inlet Reynolds number and pumping power are compared for the five microchannel heat sinks. Results show that the thermal performance of the microchannel heat sink with bifurcation flow is better than that of the corresponding straight microchannel heat sink. The heat sinks with larger bifurcation ratio and length ratio provide much better thermal performance. It is suggested to employ bifurcation flow path in the liquid-cooling microchannel heat sinks to improve the overall thermal performance by proper design of the bifurcation position and number of channels.

Constructal design and thermal analysis of microchannel heat sinks with multistage bifurcations in single-phase liquid flow

Based on constructal theory, five different cases with multistage bifurcations are designed as well as one case without bifurcations, and the corresponding laminar fluid flow and thermal performance have been investigated numerically. All laminar fluid flow and heat transfer results are obtained using computation fluid dynamics, and a uniform wall heat flux thermal boundary condition is applied all heated surfaces. The inlet velocity ranges from 0.66 m/s to 1.6 m/s with the corresponding Reynolds number ranging from 230 to 560. The pressure, velocity, temperature distributions and averaged Nusselt number are presented. The overall thermal resistances versus inlet Reynolds number or pumping power are evaluated and compared for the six microchannel heat sinks. Numerical results show that the thermal performance of the microchannel heat sink with multistage bifurcation flow is better than that of the corresponding straight microchannel heat sink. The heat sink with a long bifurcation length in the first stage (Case 1A) is superior. The usage of multistage bifurcated plates in microchannel heat sink can reduce the overall thermal resistance and make the temperature of the heated surface more uniform (Case 3). It is suggested that proper design of the multistage bifurcations could be employed to improve the overall thermal performance of microchannel heat sinks and the maximum number of stages of bifurcations is recommended to be two. The study complements and extends previous works.

A Numerical Study of the Thermal Performance of Microchannel Heat Sinks with Multiple Length Bifurcation in Laminar Liquid Flow

A rectangular, straight microchannel heat sink with multiple length bifurcation has been designed, and the corresponding laminar flow and thermal performance have been investigated, numerically. Five different cases with multiple length bifurcation and various arrangements are investigated, as well as one case without bifurcations. All laminar fluid flow and surface heat transfer results are obtained using computation fluid dynamics, and a constant heat flux thermal boundary condition is applied to the heated surfaces. The inlet velocity ranges from 0.6 m/s to 1.4 m/s, with the corresponding Reynolds number from 220 to 520. The local pressure, velocity, temperature distributions, and averaged heat transfer coefficient are presented. The overall thermal resistances subjected to inlet Reynolds number are evaluated and compared for six different microchannel heat sinks. Numerical results show that the thermal performance of the microchannel heat sink with bifurcation flow is better than that of the corresponding straight microchannel heat sink, especially the heat sink with longer length bifurcation. The usage of multiple length bifurcated plates in microchannel heat sink can reduce the overall thermal resistance by a factor of up to 2, and make the temperature of a heated surface more uniform, especially for the heat sink having a short bifurcation in the center and two bifurcations near the sides (case 4). It is suggested that proper design of the multiple length bifurcation could be employed to improve the overall thermal performance of microchannel heat sinks.

Analysis of the Transient Single-Phase Thermal Performance of Micro-Channel Heat Sinks

The objective of this study is to examine the transient single-phase thermal behavior of micro-channel heat sinks during startup and over a short-duration power surge, and to investigate the effects of property and geometry parameters on this behavior. The transient analysis required the solution of three-dimensional conjugate heat transfer in the heat sink. These solutions were obtained numerically using the finite control-volume method and the numerical accuracy of the results was carefully assessed. Accuracy of the numerical model was validated by comparisons with available experimental data. The behavior of heat sinks with different values for the fin width, channel width, material thickness between the top of the channels and top of the heat sink, and different sink materials was examined during startup from a uniform initial temperature with a uniform input heat flux, followed by a short-duration power surge from the steady-state condition. It is concluded that increasing the fin width or channel width increases the steady-state and maximum transient temperatures in the solid, and that increasing the material thickness between the heat-sink channels and the chip or using a material with larger density and specific heat increases the transient period and lowers the maximum transient temperature in the solid during the power surge.

Forced Convective Heat Transfer in Parallel Flow Multilayer Microchannels

Abstract In this paper, the effect of increasing the number of layers on improving the thermal performance of microchannel heat sinks is studied. In this way, both numerical and analytical methods are utilized. The analytical method is based on the porous medium assumption. Here, the modified Darcy equation and the energy balance equations are used. The method has led to an analytical expression presenting the average dimensionless temperature field in the multilayer microchannel heat sink. The effects of different parameters such as aspect ratio, porosity, channel width, and the solid properties on the thermal resistance are described. The results for single layer and multilayer heat sinks are compared to show the effectiveness of using multilayer microchannels.