Performance Of Microchannel Heat Sink Research Articles

Computational analysis of microchannel heat sinks with constant circular pin fins: Performance evaluation and optimization

This research entails a comprehensive computational simulation aimed at comparing the performance of microchannel heat sinks (MCHS) featuring 55-pin fins, characterized by constant circular pins with a diameter of 15µm, uniform spacing of 50µm, and variable heights ranging from 60 to 35µm. The primary objective was to assess the performance of these models with a reference Mini channel. Mesh independence validation was meticulously executed on MCHS with pin fins to ascertain the accuracy of the computational findings. The simulation encompassed seven Reynolds numbers within the range of 500–1500. The performance evaluation incorporated hydraulic and thermal factors, specifically pressure drop, Nusselt number, and the thermal performance factor (TPF). A holistic assessment of overall performance was achieved through the establishment of a heat sink thermal performance factor, accounting for both hydraulic and thermal aspects. The optimal geometry was determined based on this factor, and corresponding visual representations were generated to illustrate these findings.

Optimization of a microchannel heat sink with surrogate model and genetic algorithm

Flow maldistribution significantly impacts the performance and operation of microchannel heat sinks, which are extensively utilized across various industries. This study develops a surrogate model to address the flow maldistribution in microchannel heat sinks, employing a combination of genetic algorithm backpropagation neural networks and numerical simulations. Genetic algorithms optimize the microchannel heat sink manifold, involving five variables. The optimized manifold reduces the flow maldistribution factor by 38 % at a coolant inlet velocity of 0.1 m/s compared to that of the conventional structure. The mechanisms of this improvement are explored through comparative analyses of the manifold shape and pressure distribution. However, addressing the flow maldistribution alone proves insufficient in eliminating local hot zones within the microchannel heat sink. Consequently, this study introduces the concept of a corrected maldistribution factor and establishes a new structure guided by this factor as the optimization index. The results indicate a 47 % reduction in the maximum-to-minimum channel flow velocity ratio compared to that of the conventional structure at a coolant inlet velocity of 2 m/s. Furthermore, the maximum temperature drops by 20 K, significantly enhancing the flow and temperature distribution within the microchannel heat sink.

Experimental investigation of microchannel heat sink performance under non-uniform heat load conditions with different flow configurations

Cooling methods for multiple hotspots with high heat flux pose a reliability threat to electronic devices. This study investigates the microchannel-based heat sink performance under various non-uniform heat load conditions for different geometry with three different flow configurations (I, U and Z). An in-house designed Heater Array Unit (HAU) facilitates the generation of both uniform and non-uniform heat loads using a heater power supply. Two different microchannel geometries were employed, namely, microchannel-1 (MC-1) with channel and fin widths of 0.6 mm and 0.33 mm, respectively, and MC-2 with dimensions of 0.64 mm and 0.572 mm. Each microchannel incorporates three manifold configurations (I, U, and Z). Each flow configuration is regulated by flow control valves. Various non-uniform heat load patterns were considered, including streamline, non-streamline, and across-streamline conditions. To assess the thermal performance of the heat sinks the parameters used are thermal resistance (Rth), Nusselt number (Nu), and temperature non-uniformity (Ѱ). Experimental findings indicate that the MC-2 design with an I flow configuration is more suitable for uniform heat load conditions. On the contrary, for some non-uniform heat load cases MC-1 also showed up as a suitable design over MC-2.

Fluid flow and heat transfer characteristics of a microstructured microchannel heat sink under flow boiling condition

A microchannel heat sink (MCHS) is known as a heat dissipation device from the miniaturized electronic components and devices due to its capability to dissipate high heat flux from smaller surface area. However, the higher pressure drop and the uneven heat removal along the channel length are the noticeable disadvantages of MCHS. Though there are attempts to address these shortcomings, no existing study has been found to study the effect of positions of microstructures (micro-pin fin and blind holes) and combined effect of micro-pin fins and blind holes under flow boiling condition. Therefore, in the present study, an attempt has been made to logically explain the effect of various arrangements and positions of pin fins and blind holes in the selected twenty-four uniformly distributed stations on the thermohydraulic performance of MCHS through numerically predicted results. The objectives of the study have been attained using the following three analyses, flow boiling, (i) with saturated fluid inlet conditions (inlet Re = 500), (ii) with different inlet subcooling (20, 40, and 60 °C), and (iii) with different heat flux conditions (100, 150, 200 and 250 W/cm2). From the study, it is observed that the pin fin enhances heat transfer in single-phase flow and delays the phase change by disturbing the flow. The blind holes act as nucleation sites and help phase change heat transfer. It is also observed that the ratio of single-phase and two-phase length and arrangement of microstructures in these two regions predominately dominate the heat transfer and fluid flow characteristics of the microchannel heat sink. The optimum performance (maximum heat transfer coefficient and minimum pressure drop) is achieved when twelve pin fins are placed in the upstream half and twelve blind holes are located at the downstream half of the channel. However, design improvement is possible through more computational and experimental analysis.

Effect of flow pulsation on heat transfer performance of biomimetic bark microchannel heat sink

Pumping coolant or using pulse flow through microchannels with novel structures on microelectronic devices is suitable for high heat flux dissipation and sensor development. This study proposes a novel microchannel designed as a series of biomimetic bark channel networks. Simulation and experimental testing of temperature distribution and heat transfer performance are conducted under different working conditions, including various fluid parameters. The results show that combining biomimetic bar microchannel and pulsation flow can improve heat transfer performance. The effect of pulsating flow frequency on the temperature is only evident outside the range of 10 mm from the inlet. Compared with non-slip boundaries, the boundary slip of pulsating flow slightly enhances heat transfer. Pulsating flow has an optimal frequency, minimizing thermal resistance for different inlet temperatures.

Thermal-Hydraulic performance of microchannel heat sink designed with counter-flow and different groove shape

Microchannel heat sink is a potential procedure for scatter heat as a result of its little size and high effectiveness. Thermal resistance and pumping power are two significant parameters to assess the behavior of microchannel heat sink. In this review, heat transfer and fluid behavior have been concentrated mathematically in a microchannel heat sink with the counter stream and different shape of the groove. Four unique cases are discussed in this paper, microchannel heat sink with rectangular groove (R-MCHS), microchannel heat sink with circular groove (C-MCHS), microchannel heat sink with triangular groove (T-MCHS), and straight microchannel heat sink (S-MCHS). Three-dimensional numerical simulation is conducted with the Reynolds number, Re, shifting from 100 to 500 with expanding 100 for each step. As the coolant, Single-stage fluid water streams in the heat sink. The thermal and hydraulic performance of these cases are evaluated by comparing the average temperature of the solid domain, Nusselt number, Thermal Resistance, and Pumping Power. Contrasted with the S-MCHS, the thermal performance of MCHSs with grooves is increased, and the Nusselt number increased at the furrow area. Likewise, the pumping power is bigger for all cases with grooves contrasted and S-MCHS. In all grooved cases, R-MCHS has the lowest average temperature on the bottom surface and the highest average temperature in the solid domain. The C-MCHS has the least thermal resistance for all Re between 100 to 500. In light of the component, the plan standards to move toward the presentation of inclination are proposed.

Exploiting the flow maldistribution characteristics in parallel microchannel heat sinks of I, U, and Z configurations to tackle the nonuniform heat loads

This study aims to analyze the cooling performance of parallel microchannel heat sinks (PMCHS) under uneven heat flux distributions, taking into account different flow configurations including I, U, and Z. The objective is to demonstrate the potential of utilizing the flow maldistribution inherent in each configuration to effectively manage and mitigate the effects of uneven heat flux distributions. Four different heating arrangements have been considered, namely uniform, non-streamline, streamline, and across-streamline to generate the uneven heat flux distributions. A three-dimensional numerical simulation has been performed to analyze the combined effect of uneven heat flux distributions and flow maldistribution characteristics on the thermal performance of PMCHS. To assess the thermal performances; thermal resistance (Rth), Nusselt number (Nu), temperature nonuniformity (Ψ), and fin efficiency (ηfin) have been employed. The results show that all three flow configurations exhibit similar thermal performances for uniform heat load conditions (0.1 K/W for Rth, 5.5 kW for Nu, 0.3 for Ψ, and 0.98 for ηfin). However, in the case of uneven heat flux distributions, the thermal performance of each configuration is observed to be varying with respect to hotspot positions. This study reveals that each configuration has a huge discrepancy in terms of thermal performance with respect to uneven heat flux distributions. Also, the study concludes that a single flow configuration alone is insufficient to address the cooling challenges that arise due to uneven heat flux distributions. The cooling capability of any configuration to handle uneven heat distributions mainly depends upon the flow maldistribution characteristics of the respective configurations.

Study on the efficient heat transfer mechanism of microchannel pin-fin arrays under low pumping power

The efficient heat transfer with low pressure loss has long been a critical challenge in the microchannel heat sinks (MCHS) design. Further study is required for the quantitative analysis of the longitudinal vortex heat transfer enhancement mechanism. In this research, a microchannel heat transfer experiment and corresponding simulations are conducted. Based on the common Reynolds number range in engineering applications of MCHS, the underlying causes of heat transfer enhancement and pressure loss increase in MCHS with respect to Reynolds numbers is clarified. The results show that when the Reynolds number is 400, the cylindrical wake reduces the synergistic angle between the velocity and the temperature gradient at the streamwise gap, which greatly enhances the heat transfer performance of MCHS. In addition, when the Reynolds number is 900, the early separation of the cylindrical wake vortex leads to a significant reflux near the center of the spanwise gap, which significantly increases the pressure loss. A Different Reynolds number Efficiency Evaluation Criterion (DEEC) is proposed for evaluating the performance of MCHS. It is found that the flow state of cylindrical wake with Reynolds number of 400 has the best heat transfer efficiency. The concept of introducing longitudinal vortices into the pin–fin array can serve as a key guideline in the heat transfer enhancement optimization design of MCHS.

Numerical simulation of convective heat transfer behavior of nanofluids in elliptical microchannels

This study employs a numerical simulation approach to investigate the heat transfer performance of elliptical microchannel heat sinks (MCHS) with varying aspect ratios (AR) of the elliptical cross-section. The convective heat transfer behavior of water and water-based nanofluids containing CuO nanoparticles at different volume fractions within the MCHSs is examined. The research results indicate that at Re = 600, as the AR of the elliptical cross-section increases from 1:1 to 1.75:1, the thermal performance of the MCHS improves by 5.33%. Furthermore, with an increase in the volume fraction of nanofluid from 0 to 0.75%, the convective heat transfer coefficient of the nanofluid increases by 11.87%. Compared to the circle MCHS using water as the coolant, the MCHS with an elliptical cross-section with an AR of 1.75:1 and a nanofluid volume fraction of 0.75% can reduce the maximum temperature of the chip by 9.78%.

Multi-objective optimization design of a cobweb-like–channel heat sink using particle swarm algorithm

Abstract The cobweb-like microchannel heat sink is acknowledged for its exceptional heat transfer capabilities in comparison to other biomimetic microchannel heat sinks. The objective of this paper is to improve the performance of the cobweb-like microchannel heat sink by optimizing its geometric structure parameters through a multi-objective approach. The Box-Behnken design method was utilized to conduct response surface analysis on the design variables, and the Pareto solution set was obtained by applying the multi-objective particle swarm optimization algorithm to the fitted functions of pressure and temperature. The TOPSIS method was used to select the most appropriate solution from the Pareto solution set. The performance of a microchannel heat sink was evaluated using the computational fluid dynamics (CFD) analysis. The optimized structure of the cobweb-like microchannel heat sink led to a decrease in the average temperature by 3K and a reduction in pressure drop by 1514Pa, as compared to the original design. This significant improvement in the overall performance highlights the importance of a well-designed channel structure in further enhancing the comprehensive performance of the microchannel heat sink.

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.

Experimental and numerical study on thermofluidic characteristics of microchannel heat sinks with various micro pin-fin arrays arrangement patterns

Targeting at improving the comprehensive performance of microchannel heat sink, microchannel heat sinks integrated with various arrangements of micro pin-fins arrays are proposed in this paper. The thermofluidic characteristics and heat transfer enhancement mechanism of different pin-fins arrangement patterns is investigated by experimental test and numerical simulations. It is found that the partially uniform/gradient stagger pin-fins arrangement patterns present largest pressure drop with moderate heat dissipation performance, while the patterns with overall pin-fins distribution demonstrate superior heat transfer performance than all partial pin-fins distribution modes. Thus, overall gradient stagger pin-fins arrangement with moderate pressure drop yields optimal heat transfer capacity, achieving 4.8∼6.1 times enhancement than smooth channel. Furthermore, the partially uniform/gradient stagger pin-fins arrangement patterns indicate best temperature uniformity and thermal resistance with 26.2 K and 47.6% reduction than smooth channel at 80 ml/min, 100 W/cm2, respectively. The temperature trend in the longitudinal direction shows peaks and troughs for arrangements with partial pin fins distribution, while patterns of gradient pin fins distribution exhibit wavy curves of temperature rise. Additionally, the performance evaluation plot is adopted to describe the comprehensive performance of heat sinks with different pin fins patterns. It is observed that the overall gradient stagger pin-fins arrangement shows optimal comprehensive performance among all patterns, achieving heat transfer enhancement ratio greater than 4 in contrast with smooth channel. Finally, the correlations of Nusselt number and apparent friction factor for patterns are established. This study provides feasible insights on the performance improvement of microscale liquid cooling technologies for thermal management of electronic devices.

High heat flux dissipation of membrane-venting heat sink with thin film boiling

Microchannel flow boiling exhibits outstanding heat transfer capabilities, rendering it a promising technology for cooling high heat flux devices. Nonetheless, rapid vapor generation in the channels increases pressure drop and leads to local dryness, restricting the performance of microchannel heat sinks. In this study, we designed a membrane-venting heat sink that has a hydrophobic porous membrane above a thin liquid film for venting vapor. The phase change of this heat sink comprises not only thin film flow boiling in the horizontal direction but also thin film boiling and thin film evaporation in the vertical direction, thereby mitigating the detrimental effects of flow boiling. Experiments indicate that utilizing a membrane with 1.0 µm pore size for venting can enable the effective heat flux of the heat sink to achieve 287.8 W/cm², with a transmembrane heat flux of 152.7 W/cm². Furthermore, the surging trend of pressure drop with heat flux was significantly slowed down, and the maximum effective heat flux increased by 553 % compared to the configuration without vent. This study demonstrates that adding and enhancing the vertical heat and mass transfer channels via hydrophobic porous membranes is a potent method for considerably improving flow boiling.

Oblique microchannel merged with circle micro pin-fin as a novel hybrid heat sink for cooling of electronic devices

Recently, the advantages of microchannel and micro pin-fin heat sinks for cooling have become clear. This study delves into the effects of hybrid designs on electronic chip cooling by combining microchannel and pin-fin patterns. The research contrasts the performance of a straight microchannel heat sink (Case Ⅰ), circular pin-fin (Case Ⅱ), straight-circular pin-fin-straight (Case Ⅲ), and oblique grooved straight-circular pin-fin-oblique grooved straight (Case Ⅳ). Results show that Case Ⅳ's Nu number reaches 61 at Re = 1250, surpassing Case Ⅰ, Case Ⅱ, and Case Ⅲ by 517 %, 32 %, and 235 %, respectively. Case Ⅳ also has the highest pressure drop. The study calculates each Case's performance evaluation index (ƞ), highlighting the balance between enhanced Nu numbers and pressure drops. Case Ⅳ's ƞ is notably higher than Case Ⅱ and Case Ⅲ. To achieve a more uniform thermal distribution across the entire heat sink, the orientation of the oblique grooves is modified in Case Ⅳ, resulting in a new design labeled Case Ⅴ. While Cases Ⅳ and Ⅴ have similar Nusselt numbers, Case Ⅴ's design ensures consistent temperature distribution, reducing hotspot risks on the chip.

Experimental investigations on a novel instability suppression mechanism for subcooled flow boiling in microchannel heat sink

Flow boiling instability reduces the thermo-hydraulic performance of microchannel heat sink (MCHS) considerably. High rate of vapor bubble generation and their rapid growth block the confined flow passage of the microchannel and induce high flow resistance. Periodic changes in flow regimes and inefficient vapor venting lead to backflow. It increases dry out period and reduces overall heat transfer coefficient in MCHS. In this research, a novel instability suppression mechanism using Inlet Plenum Flow Restrictor (IPFR) is proposed. The subcooled flow boiling experiments are performed in a MCHS using degassed deionized-water (DI water). The inlet fluid temperature is maintained at 78 ± 1 °C (subcooling of 22 ± 1 °C). The results are reported for mass flux of 220, 320 and 416 kg/m2s and heat flux in the range of 21–88 W/cm2. The instability is observed to reduce by 76 % for surface temperature, 74 % for inlet plenum fluid temperature and 52 % for outlet plenum fluid temperature. Hence, the temperature instability is improved by 67 %. The heat transfer coefficient is increased by 13 % and pressure drop penalty is reduced by 34 % for stable operation of MCHS.

Thermal performance of microchannel heat sink integrated with porous medium, slip coefficient and phase change material and machine learning approach

In this study, the thermal performance (TP) of the microchannel heat sink (MCHS) under the influence of the slip coefficient on the microchannel wall, the use of porous medium (PM) and phase change material (PCM), and the changes in the geometrical parameters and the shape of the microchannel have been discussed. The flow and energy equations were solved using the finite volume method. The validation of the melting process, slip coefficient, and porous medium with the previous literature demonstrate the high accuracy of the numerical solution, with the difference between the results being <8 %. The results indicate that using a wavy microchannel can improve TP by approximately10.6 % and 5 % compared to smooth and converging microchannels. Additionally, using non-Newtonian fluids with a power characteristic of 0.53 leads to improved TP about 2.8 % by reducing shear stress compared to Newtonian fluids. Furthermore, the presence of slip on the microchannel wall influences the flow pattern, resulting in reduced convection resistance and improved TP about 3.2–3.8 %. The highest TP was observed at a slip coefficient of 0.00001. Incorporating PM in the microchannel (either in the center or around it) can enhance TP by approximately 8–15 % compared to the base state, with greater improvements observed when PM is placed around the microchannel. The type of PM material and the porosity coefficient significantly impact TP. Varying the cross-sectional shape of the microchannel (square, rhombus, and triangle) has a substantial effect on improving TP compared to a circular cross-section, with the highest TP (with a 71 % increase) observed in microchannels with a square cross-section. Lastly, the use of PCM and PM on the active surface leads to a significant TP improvement of over 80 % compared to the base state. Using the Group Method of Data Handling algorithm, thermal resistance was estimated with an R-square value of 0.94 to validate the available data.

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 efficiency of microchannel heat sink: Incorporating nano-enhanced phase change materials and porous foam gradient and artificial intelligence-based prediction

This study investigates the impact of incorporating phase change materials (PCMs), nano-particles (NPs) enhanced PCMs (nePCMs), and porous foam gradients on the thermal performance (TPEF) of microchannel heat sinks (MCHS). Specifically, the effect of different PCM types, hybrid NPs, and spiral microchannels on the TPEF is examined using numerical solutions based on the finite volume method. The results indicate that increasing Re and using spiral microchannels significantly enhance the TPEF. The incorporation of NPs-water and PCM can reduce the thermal resistance (R) of MCHS, with PCM significantly improving the TPEF. Among the PCMs, ENCAPSUL demonstrates the best performance for MCHS. The combination of hybrid nePCM increases TPEF by approximately 9%. The combination of PCM-aluminum oxide-iron oxide NPs exhibits the highest TPFE. The use of a porous medium with PCM can decrease the R by about 60 %, and it improves the TPEF by altering the conduction and convection mechanism. various scenarios of changes in the porosity coefficient have been considered for porous foam gradient and the best performance is achieved for the NYPC mode. Various scenarios of MCHS with PCM-water combinations have been explored, and the best performance is observed when PCM is situated in the microchannel. Additionally, artificial intelligence techniques, such as the Group Method of Data Handling (GMDH), have been utilized to estimate R, and a multivariate polynomial regression (MPR) equation has been developed to calculate R based on input variables. GMDH is more accurate compared to MPR.

Numerical investigation of a hybrid double layer microchannel heat sink with jet impingement

This study investigates numerically, with experimental verification, the performance of a hybrid multilayer microchannel heat sink with jet impingement. The three-dimensional fluid flow and heat transfer processes were solved using the finite volume method using Fluent CFD Solver. The surface temperature distribution and pressure drop across the system were monitored under a range of designs and operating conditions including different flow rates, channel aspect ratios, jet spacings, and distribution of the flow rate between the jets and the channels. Our results show that increasing the number of jets minimizes the pressure drop, yet, results in higher surface temperatures. Increasing channel height decreased the pressure drop and enhanced the temperature uniformity. Using a double-layer heat sink instead of a single-layer one resulted in a decrease of 7.5% in surface temperature with a considerable reduction in pressure drop. Nevertheless, adding copper fins/posts in the lower channel layer is essential to help conduct the heat to the top layer and improve the heat removal rate. We also studied dividing the total flow rate between the jets and the main cooling channel and found that it can reduce the average temperature on the hot surface even though it did not improve the temperature uniformity. We verified our simulation results with experimental measurement for a single-layer hybrid heat sink with jet impingement and results matched with a temperature difference below 5 °C. Based on our simulations, the DL-hybrid module can remove high heat fluxes while maintaining an acceptable pressure drop.

Experimental and numerical investigation of a single-phase microchannel flow under axially non-uniform heat flux

The design of microchannel based heat sinks for advanced electronic component continues to receive research interest, especially with the ever-increasing density of advanced chips with concomitant increase in heat generation. One aspect of microchannel heat sink design objectives is the optimum employment of non-uniform heat dissipation through the channel length. Two dominant schools in the performance optimization of non-uniform heat sinks are: 1) entropy minimization and 2) thermal resistance minimization. These two approaches usually result in contradictory conclusions: one recommending the use of increasing heat flux, the other recommending a decreasing heat flux. The current study seeks to explain this discrepancy by experimentally and numerically studying the heat transfer mechanisms in a single microchannel tube under the effect of non-uniform heat flux. This study presents an experimental framework capable of generating a wide range of pre-specified heat flux profiles over a single microchannel, mimicking actual heat flux profiles observed in thermo-electronic devices. We employ three flux profiles: 1) hotspots located at different locations with uniform background heat flux, 2) linearly ascending heat flux, and 3) linearly descending heat flux. The results show good agreement between numerical simulations and experimental measurements and provide insights into the microchannel tube's fundamental heat transfer mechanisms. Based on these insights, the study provides design guidelines to enhance microchannel heat sink performance under non-uniform axial heat fluxes. Finally, the discrepancy between entropy and heat resistance minimization approaches is explained.