Thermal Performance Of Microchannel Heat Sink Research Articles

CFD investigation of the feasibility of polymer-based microchannel heat sink as thermal solution

Abstract Microchannel heat sinks (MCHSs) are promising thermal solutions in miniaturized or compact devices. Lightweight aspect has been given huge emphasis in recent years. Metal-based materials are commonly used to fabricate MCHSs due to their high thermal conductivity. Consequently, MCHSs are heavy due to the high density of these materials albeit the small footprint of MCHSs. Polymer-based materials are interesting alternatives. Despite their poor thermal conductivity, lightweight feature attracts the interest of researchers. Heat transfer is a conjugate process of heat conduction and heat convection. Poor heat conductions aspect may be compensated through enhancement of heat convection aspects. Although polymer-based materials have been used in microscale heat transfer studies, their focus was not on their feasibility. The present study aims to evaluate the feasibility of polymer-based MCHSs as thermal solutions. The effect of thermal conductivity of fabrication materials, including polymer-based PDMS, PTFE, PDMS/MWCNT, and metal-based aluminum, on the thermal performance of MCHSs was investigated and compared at various inlet flow rate, fluid thermal conductivity, and microchannel ratio at different constant heat fluxes using three-dimensional CFD approach. Results showed that the thermal performance of MCHSs was greatly affected by the heat conduction aspect in which poor heat conduction limited the thermal performance improvement due to enhanced heat convection aspects. This suggests polymer-based materials have the potential for heat transfer applications through thermal conductivity enhancement. This was confirmed in the further analysis using a recently proposed high thermal conductivity polymer-based graphite/epoxy MCHS and a hybrid-based PDMS/aluminum MCHS.

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.

Investigating the effect of Brownian motion and viscous dissipation on the nanofluid heat transfer in a trapezoidal microchannel heat sink

In the present study, laminar forced convection of copper-oxide nanofluid in a trapezoidal microchannel-heat-sink (MCHS) is studied using the Eulerian–Eulerian two-phase approach. The incompressible, three dimensional and steady state conservation equations are solved using finite volume method. The substrate material is assumed to be silicon, mean diameter of spherical nanoparticles are considered 100nm and in the 1–4% volume concentration range. The effects of viscous dissipation, Brownian motion and geometry change on thermal performance of MCHS are evaluated. It is observed that the Brownian motion depends on three parameters, namely, nanofluid inlet temperature, nanoparticles diameter and volume fraction. Also, it is found that with the increase in aspect factor at constant Re, average Nusselt number and pressure drop reduce, while at a specified length of MCHS, average Nusselt number decreases. Finally, it is shown that considering the viscous dissipation, pressure drop varies very slowly, while with the increase in nanoparticles volume fraction and therefore increase in viscous dissipation, heat transfer reduces non-linearly.

Analysis of Brownian motion and particle size effects on the thermal behavior and cooling performance of microchannel heat sinks

In the present paper the thermal performance of nanofluid flow in microchannel heat sinks (MCHSs) was analyzed using three different nanofluids. The fluid flow and heat transfer in the MCHS are modeled using the Darcy–Brinkman–Forchheimer and two-equation model, respectively. In order to check the validity of the results, they were compared with available experimental and numerical data in the literature and excellent agreement was found between them. The key novelties of present work are (i) using a novel and complex temperature dependent thermal conductivity model for nanofluids, based on Brownian motion induced micro mixing, (ii) using new nanofluids with three types of nanoparticle materials i.e. aluminum oxide (Al2O3), zinc oxide (ZnO) and copper oxide (CuO) and 60:40 (by mass) EG–water for the base fluid, (iii) investigating the effect of nanoparticles size and Brownian motion of particles on thermal performance of MCHS.

Heat transfer enhancement in microchannel heat sinks using nanofluids

Heat transfer enhancement in a 3-D microchannel heat sink (MCHS) using nanofluids is investigated by a numerical study. The addition of nanoparticles to the coolant fluid changes its thermophysical properties in ways that are closely related to the type of nanoparticle, base fluid, particle volume fraction, particle size, and pumping power. The calculations in this work suggest that the best heat transfer enhancement can be obtained by using a system with an Al2O3–water nanofluid-cooled MCHS. Moreover, using base fluids with lower dynamic viscosity (such as water) and substrate materials with high thermal conductivity enhance the thermal performance of the MCHS. The results also show that as the particle volume fraction of the nanofluid increases, the thermal resistance first decreases and then increases. The lowest thermal resistance can be obtained by properly adjusting the volume fraction and pumping power under given geometric conditions. For a moderate range of particle sizes, the MCHS yields better performance when nanofluids with smaller nanoparticles are used. Furthermore, the overall thermal resistance of the MCHS is reduced significantly by increasing the pumping power. The heat transfer performance of Al2O3–water and diamond–water nanofluids was 21.6% better than that of pure water. The results reported here may facilitate improvements in the thermal performance of MCHSs.

Evaluation of Heat Transfer Augmentation in a Nanofluid-Cooled Microchannel Heat Sink

Present investigation deals with appraising heat transfer enhancement of single phase microchannel heat sink (MCHS) by ultra fine Cu particle incorporation in base coolant fluid. The particle diameter is of nanometer size and base fluid in combination of nanoparticles is called nanofluid. Governing equations for fluid flow and heat transfer are based on well established “porous medium model” and accordingly, modified Darcy equation and two-equation model are employed. Appropriate equations for both fluid flow and heat transfer are derived and cast into dimensionless form. Velocity profile is obtained analytically and in order to solve conjugate heat transfer problem a combined analytical–numerical approach is employed. For heat transfer analysis, thermal dispersion model is adopted and latest proposed model for effective thermal conductivity – which considers the salient effect of interfacial shells between particles and base fluid – is integrated into model. The effects of dispersed particles concentration, thermal dispersion coefficient and Reynolds number are investigated on thermal fields and on thermal performance of MCHS. Additionally, the impact of turbulent heat transfer on heat transfer enhancement is considered.