Microchannel Heat Sink Research Articles

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%.

Improved flow boiling performance and temperature uniformity in counter-flow interconnected microchannel heat sink

Microchannel flow boiling is one of the most effective solutions to the problem of heat dissipation caused by high power electronic devices. However, inherent drawbacks such as low critical heat flux due to dry-out of the liquid film near the channel exit, relatively high two-phase flow pressure drop, severe temperature nonuniformity and boiling instability at high heat flux still prevent widespread commercial application. In this study, based on the idea of uniform vapor quality along the flow direction, a copper Counter-Flow Interconnected Microchannel (CFIM) was proposed to address the main issues currently faced by two-phase microchannel heat sink. A comprehensive comparative study of CFIM, Co-Current Microchannel (CCM) and Counter-Flow Microchannel (CFM) was carried out from the aspects of boiling stability, boiling heat transfer characteristics and temperature uniformity. Three slots of 0.2 mm, 0.5 mm and 0.8 mm in width, denoted as IM0.2, IM0.5 and IM0.8, respectively, are considered. Experiments are conducted at mass fluxes of 291–618 kg/m2·s, saturation temperature of 40 °C and effective heat fluxes of 3–293 W/cm2, using the dielectric fluid R1233zd(E) as the working fluid. The results show that the CHF and average two-phase heat transfer coefficient (HTC) of CFIM are increased by 40.6 ∼ 100.5 % and 70.4–83.6 %, respectively, while the two-phase pressure drop is decreased by 17–32.6 % compared to CCM. The design of the counter-flow interconnected structure can manipulate the void fraction and two-phase flow pattern, resulting in a near uniform void fraction and flow pattern. The structure of these connecting slots promotes nucleate boiling and fluid mixing of neighboring channels. More importantly, the flow boiling instability and temperature non-uniformity in CFIM are well suppressed. In addition, IM0.2 has higher heat dissipation than IM0.5 and IM0.8 due to enhanced bubble nucleation, reducing superheat requirements and periodic rewetting to the center of the channel. The results of this research reveal that utilizing a microchannel heat sink with a counter-flow interconnected configuration can effectively improve heat transfer performance during flow boiling. Furthermore, it helps to mitigate issues such as flow boiling instability and temperature non-uniformity.

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.

Constructal Solid and Perforated Fin Installation in a Combined Microchannel Heat Sink for Maximum Heat Transfer

Constructal Solid and Perforated Fin Installation in a Combined Microchannel Heat Sink for Maximum Heat Transfer

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 study on flow boiling of HFE-7100 in rectangular parallel microchannel

With the rapid development of microelectronic technology, the integration and power of chip are increasing. Heat dissipation with high heat flux in limited space has become a bottleneck restricting the efficient and stable operation of the microelectronic devices. Flow boiling in microchannel heat sink is one of the most essential candidates for solving this problem. It has been shown that remarkable high heat transfer performance can be achieved through the liquid-to-vapor change process, which can dissipate a large amount of heat from a small area. In addition, dielectric fluorinated fluids, such as HFE-7100, HFE-7200, and FC-72, are especially suitable for cooling microelectronic devices, because of their excellent safety and environmental characteristics. However, dielectric fluorinated fluids have poorer thermophysical properties than water. Thus, the flow boiling heat transfer characteristics of dielectric fluorinated fluids can be different from those of water. In this work, flow boiling heat transfer and flow characteristics of HFE-7100 in a rectangular parallel microchannel are investigated. The tests are conducted at mass fluxes from 88.9 to 277.8 kg·m<sup>–2</sup>·s<sup>–1</sup>, inlet subcooling temperature from 20.5 to 35.5 ℃ and effective heat flux from 12 to 279 kW·m<sup>–2</sup> at nearly atmospheric pressure. The effects of mass flux, inlet subcooling temperature, effective heat flux and vapor quality are examined and analyzed. Additionally, flow visualization is also obtained to explain the heat transfer mechanism during the experiments. The results show that the boiling hysteresis is observed for HFE-7100 at low inlet subcooling temperature, and the increasing inlet subcooling temperature and mass flux can delay the onset of nucleate boiling. The increases of inlet subcooling temperature and mass flux can enhance the two-phase heat transfer coefficient. And the two-phase heat transfer coefficient is significantly dependent on the inlet subcooling temperature in the slug flow, while it is significantly dependent on the mass flux in the annular flow. The two-phase pressure drop increases drastically as the effective heat flux increases. And the two-phase pressure drops with different mass fluxes at constant vapor quality are obviously different between the slug flow and the annular flow. Furthermore, the experimental data are compared with four predicted values of the literature. It is found that the correlation of Lockhart has the best statistical agreement with an MAE of 19.6% and over 85% of points in the deviation bandwidth of ±30%. The results in this paper give valuable theoretical guidance for designing and optimizing heat dissipation equipment for microelectronic devices. By utilizing HFE-7100 as the coolant and microchannel heat sinks in flow boiling, it is possible to enhance the stability and reliability of the electronic devices. Additionally, the heat transfer performance associated with different heat fluxes can be improved by regulating the inlet subcooling and mass flow rate. Finally, the two-phase pressure drop correlation proposed by Lockhart can be employed to predict the pump power for heat dissipation equipment.

Subcooled flow boiling in ultrahigh-aspect-ratio microchannels for high heat flux cooling

In present work, the numerical simulation and experimental investigations were performed on the subcooled flow boiling behavior in ultrahigh-aspect-ratio microchannel heat sink (AR = 25). As the heat flux is low, the unique discotic bubble expands the condensation area while ensuring an adequate evaporation area in the channel. When the heat flux increases, the violently fluctuating liquid-vapor interface forms a throat shape that effectively reduces the cross-section of vapor flow. Furthermore, the flow pattern of annular flow at the channel bottom and nucleate bubble at the channel top realizes a combined heat transfer mechanism (nucleate boiling and liquid film evaporation occurs simultaneously). Moreover, the phenomenon of “droplet inside the bubble” caused by bubble coalescence also significantly enhances the thermal process. The fluctuation of local pressure drop in UARM acts gently, which effectively inhibits the boiling instability, and its average value can be reduced by 68.9%. The maximum CHF reaches 1258.1 W/cm2 under a mass flux of 410.2 kg/(m2·s) based on the experimental data, indicating a tremendous potential for the efficient heat dissipation.

Topology optimization of a pseudo 3D microchannel heat sink: influence of the initial guess

Nowadays, the optimization of microchannel heat sinks involves using algorithms, e.g., topology optimization (TO), to find the optimal layout of fluid channels to enhance certain objectives, e.g., heat transfer, pressure drop. The outcome is an unintuitive material distribution in the design space, subject to constraints such as manufacturability, fluid flow requirements, and thermal performance. This approach has been shown to provide significant benefits compared to traditional design methods, leading to increased cooling performance. However, depending on the application, defining an initial (i.e., starting) guess for the optimization problem is not trivial. Initial guess for TO, i.e., starting design for the optimization process, can play a crucial role in determining the final optimized design. Its choice may affect the convergence rate, the performance of the final solution, and the computational effort, as it can be set in a variety of ways, e.g., a random distribution, a preconceived design, or a combination of these two. In this study, we propose a heuristic approach for incorporating a genetic algorithm (GA) as outer algorithm into the TO routine in order to find the initial guess that ensures the lowest thermal resistance while limiting the pumping power. The aim is to correlate initial designs with final objectives and to define new useful insights on microchannel optimization, since TO has proved to be a promising area of research for the development of advanced thermal management systems.

Heat transfer and flow characteristics of cuo-al2o3 hybrid nanofluids in slotted finned channels

This study aimed to investigate the heat transfer coefficient of CuO-Al2O3 hybrid nanofluids within a microchannel heatsink, focusing on the impact of flow rate and volume fraction. The thermal conductivity and viscosity of hybrid nanofluids with different particle ratios were investigated. The results showed that the nanofluids have a more remarkable enhancement in thermal conductivity than water. Employing the hybrid nanofluids enhanced the heat transfer coefficient significantly. Furthermore, a slight growth in the friction factor was observed.

Numerical Investigation of Thermal and Hydraulic Performance in an Interrupted Microchannel Heat Sink with Aluminum Oxide Nanofluid

Numerical Investigation of Thermal and Hydraulic Performance in an Interrupted Microchannel Heat Sink with Aluminum Oxide Nanofluid

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.

Thermal Management of Discretized Heaters using CuW Microchannel Heat Sinks and FC3283

Thermal Management of Discretized Heaters using CuW Microchannel Heat Sinks and FC3283

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.

Heat transfer enhancement of staggered water-droplet grooved microchannel heat sink using Al2O3 nanofluid

The performance reliability and durability of modern cutting-edge technology are highly dependent on the ability of the devices to dissipate enormous amounts of heat to the ambient environment. A synergetic combination of two passive heat transfer enhancement techniques would be favourable to prevent overheating. The concurrent implementation of Al2O3 nanofluid and staggered water-droplet groove geometries in micro-channel heat sink application was investigated using numerical approach. Numerical results reported in this study revealed that the heat dissipation capability of the micro-channel heat sink can be improved when Al2O3 nanofluid is used in conjunction with the water-droplet grooves arranged in staggered manner. The predictive accuracy of the numerical method has been validated with published results available.

A Study of the Thermal Performance of a Converging-Diverging Microchannel Heat Sink with Triangular Ribs

A Study of the Thermal Performance of a Converging-Diverging Microchannel Heat Sink with Triangular Ribs

A novel step-gap design on the top-cover of the microchannel cold plate to improve the flow boiling stability and heat transfer performance

The current study investigates the impact of incorporating the step gap in the cover above the microchannel heat sink subject to two-phase convective boiling. The microchannel heat sink size is 49 mm × 52 mm, with a channel width of 200 μm and a height of 3 mm, with a fin thickness of 200 μm. The effect of the step gap above the microchannels (SGAM) was compared at different heights, one 1 mm, which represents 1/3 fin height, and 3 mm, which means the same fin height with the same sample with no step gap above the microchannels (NSGAM). The working fluid used dielectric fluid HFE-7000 at the mass flux ranges from 30 to 260 kg/m2·s, while the heat flux ranges from 50 to 156 W/cm2. Providing a step gap above the microchannels in the cover reduces pressure drop significantly, around 37 ∼ 48% lower than the NSGAM. The experimental results demonstrate that the SGAM configuration reduces wall superheat temperatures by approximately 4 ∼ 6 °C compared to the NSGAM configuration. Flow visualizations indicate that the SGAM design avoids flow reversal, where the pressure drop fluctuations are significantly reduced by more than three times. The experimental outcomes for excessive temperatures and total thermal resistance exhibit a high level of concordance with the analytical results, with a deviation being less than 11%. The spreading resistance comprises the major portion of the total resistance, accounting for approximately 52∼58%. The SGAM samples effectively reduce local wall temperature downstream for step gap heights 1 mm, and 3 mm are 4 ∼ 6 °C, and 2 ∼ 4 °C, respectively. Overall, these findings demonstrate the potential of the step gap above microchannels to improve flow boiling stability and heat transfer performance appreciably while offering a much lower pressure drop penalty.

Multi-objective optimization of a microchannel heat sink with a novel channel arrangement using artificial neural network and genetic algorithm

Effective cooling solutions become increasingly crucial as micro-electrical devices advance in complexity and miniaturization. Microchannel heat sinks (MCHSs) are one of the solutions, and researchers are continuously exploring innovative designs and optimization techniques to ensure that these cooling solutions meet the evolving demands of modern electronics. In the current research, a novel disk-shaped MCHS with strategically positioned baffles was selected to be investigated. Total thermal resistance (Rt) and pressure drop (ΔP) were scrutinized to assess the role of the baffle’s structural parameters (length of baffles in the first row (L), with the values of 500 μm–1500 μm, space between the baffles (S), with the values of 1700 μm–2500 μm, and angle of baffles (θ), with the values of 45°–90°). Firstly, various combinations of structural parameters of the baffles were selected as study designs, and each was numerically simulated. Artificial neural network (ANN) models and a genetic algorithm were employed to predict the data and identify the optimal designs. Based on the obtained results, higher R2 values (0.9940 for Rt Model and 0.9996 for ΔP model) indicated the accurate performance of both ANN models. Two optimal designs of optimal thermal performance (OTP) and optimal hydraulic performance (OHP) with separate objectives of minimizing Rt and minimizing ΔP were recommended. The utilization of baffles with the dimensions of L = 1500 μm, S = 2500 μm, and θ = 90° in the disk-shaped MCHS led to the attainment of the OTP. While to acquire the OHP, it was necessary to use the baffles with dimensions of L = 500 μm, S = 1700 μm, and θ = 81.8325°. In the OTP design, Rt was reduced by about 49.47 %, while in the OHP design, it decreased by approximately 30.36 % compared to the reference design.

High-quality fabrication of diamond straight microchannels heat sink with large aspect ratio microchannels using UV nanosecond laser based on multi-feed method

The high heat flux density of modern chips presents a major challenge to their development. Single-phase or two-phase flow heat dissipation techniques using high thermal conductivity materials are seen as a potential solution. However, creating microfluidic channels from ultra-high thermal conductivity diamond materials is a significant challenge. In this paper, we present an experimental study on the fabrication of diamond heat sinks with high aspect ratio microchannels using a UV-nanosecond laser processing system, along with two multi-feed processing techniques for the collecting grooves and microchannels. We used a 1 μm spacing grid path combined with a polished multi-feed process to fabricate a 1600 μm deep collecting groove with a smooth bottom morphology. We also proposed a multi-area multi-feed fabrication technique for microchannels with an aspect ratio of 8:1 and a depth of 1600 μm. Finally, we have successfully fabricated a diamond straight microchannels heat sink, featuring a high aspect ratio and low phase change damage.

Heat Transfer of Air-Water Flow in Wavy Microchannels

Effective cooling of the electronic devices is of great importance to their performance. Of particular interest is when the size of the equipment has scaled down to micro level. Despite a continuous improvement over the years, there is only a handful information on gas-liquid flow in wavy microchannels. This paper presents an experimental study of the air-water two-phase flow in a wavy microchannels heatsink typically used for cooling of electronic devices. The heatsink was made from copper with 26 wavy channels. The width and the depth of each channel were 800 and 500 μm, respectively. Two cartridge heaters were used to generate a constant heat flux. Pressure and temperatures of the working fluid at the inlet and outlet of the test section were measured using a pressure transducer and thermocouples. To evaluate the benefit of using the wavy microchannels, experiment was performed using water as the working fluid. The results showed that the wavy microchannels could elevate the Nusselt number by up to 112% compared to that obtained from the straight microchannels. Experiments at various air and water flowrates in the wavy microchannels suggested that the advantages of using the air-water flow would be obvious at the liquid Reynolds number above 379.

Optimization of microchannel heat sink based on multi-objective particle swarm optimization algorithm for integrated circuit chips cooling

The microchannel heat sink is an effective way to solve the heat dissipation problem in integrated circuit chips. In order to obtain the high efficiency and low resistance microchannel heat sink, the three variables (△h, f, g) were selected as the design variables, and the thermal resistance and pumping power were selected as objective functions. Then, the RSM, multi-objective particle swarm optimization algorithm and K-means clustering method were comprehensively applied to the multi-objective optimization of the microchannel heat sink with turbulence to obtain the five representative solutions (Case A–Case E), and the results were verified by CFD. The research shows that the maximum relative errors between Pareto optimization values and numerical simulation values of thermal resistance and pumping power of the five groups representative solutions are 0.637% and 1.187%, respectively. The Pareto optimization values are in good agreement with the numerical simulation values, and there is an effective tradeoff point between the five representative solutions of the Pareto optimal solution to make both the pumping power and thermal resistance within the optimal range. Compared with before optimization and the research results of Han Wang et al. [Appl. Therm. Eng. 2022;215:118849], the comprehensive heat transfer performance of the optimized microchannel heat sink has been improved, where the comprehensive heat transfer performance of the Case B ( Δ h = 0.0400 mm, f = 0.0979 mm, g = 0.5000 mm) is the best. The maximum temperature and pressure drop of the optimized microchannel heat sink can be reduced by 3.045% and 7.659%, respectively. Compared with the research results of Han Wang et al. [Appl. Therm. Eng. 2022;215:118849], the temperature distribution more uniform and the pressure drop of the microchannel heat sink after optimization (Case B) decreased by 7.058%. This optimization method can provide a reference for the optimization design of the microchannel heat sink structure parameters for integrated circuit chips cooling.