Numerical investigation of heat transfer enhancement and fluid flow characteristics in a microchannel heat sink with different wall/design configurations of protrusions/dimples

An inadequate cooling associated with a straight microchannel heat sink for electronic components requires an improved thermal management with an acceptable cost of hydrodynamic deterioration by extending the effective heat transfer area. The present study is an attempt to numerically investigate the heat transfer and fluid flow characteristics in a microchannel heat sink having novel sidewall ribs configurations. The investigated geometric profiles include symmetrical ellipse-, trapezoid-, hydrofoil-, and rectangular-shaped ribs. A thermodynamics-based assessment has been conducted involving various evaluation parameters that include a friction factor ratio, a Nusselt number ratio, a thermal enhancement factor, transport efficiency, and entropy generation rates for a Reynolds number in the range of 100 to 1000. The predicted results supported the motivation of adding sidewall ribs to a microchannel heat sink with a significant heat transfer enhancement and a reasonable increase of pressure drop. The increased pressure drop leads to a higher pumping requirement for the flow system design, and is therefore assessed carefully with the evaluation parameters to yield a favorable configuration based on the overall performance for range of the Reynolds number . The results show that the sidewall ribs of a hydrofoil configuration are the best performers, yielding the least augmented entropy generation rates among all considered configurations.

Three-dimensional numerical investigation of flow and heat transfer performances of novel straight microchannel heat sinks

Characteristics of heat transfer and fluid flow in microchannel heat sinks with rectangular grooves and different shaped ribs

Experimental study of flow boiling in a hybrid microchannel-microgap heat sink

Experimental and numerical study of fluid flow and heat transfer characteristics in microchannel heat sink with complex structure

Influence of aspect ratio on the thermal performance of rectangular shaped micro channel heat sink using CFD code

Wavy microchannels have been shown to possess improved heat transfer capabilities because of greater fluid mixing and boundary layer thinning. In this study, fluid flow and heat transfer characteristics of circular wavy microchannels with tangentially branched secondary channels, were numerically investigated. Its heat transfer and fluid flow characteristics were compared with other specific wavy microchannel geometries. Three-dimensional numerical studies were carried out in the Reynolds number range of 100–300 with uniform heat flux wall boundary condition, using Ansys Fluent commercial software. Validation of the model was done with experimental data from literature. Circular wavy microchannels, owing to constant curvature, lead to nearly constant Dean vortices strength. The tangential branched secondary channels helped in further effective fluid mixing and in reinitializing the boundary layer. These phenomena had significant effect on its heat transfer and fluid flow behavior. Circular wavy microchannels with tangentially branched secondary channels, having secondary channel width to primary channel width ratio (ω) equal to 0.25, showed higher overall performance than other designs considered in the present study. Velocity vectors, velocity and temperature contours are presented to explain the fluid flow and heat transfer characteristics. It is observed that circular wavy microchannels with tangentially branched secondary channel design (ω = 0.25) gives 39.36% higher Nusselt number with 21% increased pressure drop as compared to sinusoidal wavy microchannel design. The overall performance factor of circular wavy microchannel with tangentially branched secondary channel design (ω = 0.25) is higher in the Reynolds number range of 100–250 than all other designs considered in this study.

A novel microchannel heat sink with oval-shaped micro pin fins (MOPF) is proposed and the characteristics of fluid flow and heat transfer are studied numerically for Reynolds number (Re) ranging from 157 to 668. In order to study the influence of geometry on flow and heat transfer characteristics, three non-dimensional variables are defined, such as the fin axial length ratio (α), width ratio (β), and height ratio (γ). The thermal enhancement factor (η) is adopted as an evaluation criterion to evaluate the best comprehensive thermal-hydraulic performance of MOPF. Results indicate that the oval-shaped pin fins in the microchannel can effectively prevent the rise of heat surface temperature along the flow direction, which improves the temperature distribution uniformity. In addition, results show that for the studied Reynolds number range and microchannel geometries in this paper, the thermal enhancement factor η increases firstly and then decreases with the increase of α and β. In addition, except for Re = 157, η decreases first and then increases with the increase of the fin height ratio γ. The thermal enhancement factor for MOPF with α = 4, β = 0.3, and γ = 0.5 achieves 1.56 at Re = 668. The results can provide a theoretical basis for the design of a microchannel heat exchanger.

Heat transfer in rectangular microchannels heat sink using nanofluids

Microchannel heat sinks have gained prominence in the field of thermal management, offering compact and efficient solutions for dissipating heat flux from high performance electronic devices. Escalating heat flux in modern electronic devices, such as those found in telecommunication equipment, industrial automation equipment, solar devices, and data centre servers has driven the continuous development of microchannel heat sink to achieve efficient thermal management. The critical challenge in thermal management for these devices is to develop a microchannel that enhances heat transfer performance and minimises pressure drop. Heat transfer and pressure drop are two competing factors that determine the practicability of the design for real world application. Improvement in heat transfer performance usually results in an increase in pressure drop and pumping power. This study addresses the challenges of designing microchannel through comprehensive numerical analysis of fluid flow and heat transfer characteristics of a novel design that combines ribs, secondary channels, and tertiary channels. The numerical results showed that the novel microchannel design achieves a favourable balance between heat transfer and pressure drop, demonstrating its potential to be used in application where high heat transfer and efficiency are paramount. To assess the performance of the microchannels, thermal resistance, a measure of system’s resistance to heat transfer is used. At the same pumping power, thermal resistance in the new design is consistently lower compared to other designs.

Numerical simulation of fluid flow and heat transfer in a microchannel heat sink with offset fan-shaped reentrant cavities in sidewall

Thermal-hydraulic performance of interrupted microchannel heat sinks with different rib geometries in transverse microchambers

Heat transfer and flow characteristic in microchannel heat sinks (MCHS) are extensively studied in the literature due to high heat transfer rate capability by increased heat transfer surface area relative to the macroscale heat sinks. However, heat transfer and fluid flow characteristics in MCHS differ from conventional ones because of the scaling effects. This review summarizes the studies that are mainly based on heat transfer and fluid flow characteristic in MCHS. There is no consistency among the published results; however, everyone agrees on that there is no new physical phenomenon in microscale that does not exist at macroscale. Only difference between them is that the effect of some physical phenomena such as viscous dissipation, axial heat conduction, entrance effect, rarefaction, and so forth, is negligibly small at macroscale, whereas it is not at microscale. The effect of these physical phenomena on the heat transfer and flow characteristics becomes significant with respect to specified conditions such as Reynolds number, Peclet number, hydraulic diameter, and heat transfer boundary conditions. Here, the literature was reviewed to document when these physical phenomena become significant and insignificant.

Characteristics of laminar flow and heat transfer in microchannel heat sink with triangular cavities and rectangular ribs

Thermohydraulic performance of microchannel heat sinks with triangular ribs on sidewalls – Part 1: Local fluid flow and heat transfer characteristics