Two-Dimensional Variable Property Conjugate Heat Transfer Simulation of Nanofluids in Microchannels

Laminar two-dimensional forced convective heat transfer of CuO-water and Al2O3-water nanofluids in a horizontal microchannel has been studied numerically, considering axial conduction effects in both solid and liquid regions and variable thermal conductivity and dynamic viscosity. The results show that using nanoparticles with higher thermal conductivities will intensify enhancement of heat transfer characteristics and slightly increases shear stress on the wall. The obtained results show more steep changes in Nusselt number for lower diameters and also higher values of Nusselt number by decreasing the diameter of nanoparticles. Also, by utilizing conduction number as the criterion, it was concluded from the results that adding nanoparticles will intensify the axial conduction effect in the geometry considered. 1. Introduction In the last two decades, many cooling technologies have been pursued to meet the high heat dissipation rate requirements and maintain a low junction temperature for electronic components. Among these efforts, the microchannel heat sink (MCHS) has received much attention because of its ability to produce high heat transfer coefficient, small size and volume per heat load, and small coolant requirements [1]. Tuckerman and Pease [2] were first to introduce the concept of microchannel heat sinks for high heat flux removal and employ water flowing under laminar conditions in silicon microchannels. Afterwards, various aspects of the fluid flow in microchannel have been studied experimentally and numerically. Some of them, such as Li et al. [3], Hetsroni et al. [4], and Lee and Garimella [5], have done experimental observations to analyze microchannels from friction and heat transfer point of view and others such as Gamrat et al. [6] and Xie et al. [7] studied numerical aspects of them. Also some others used different numerical methods to consider the conjugate heat transfer characteristics such as Wang et al. [8] who used Lattice Boltzmann method. Nanofluids have been proposed as a means to enhance the performance of heat transfer liquids currently available. Recent experiments on nanofluids have indicated significant increase in thermal conductivity compared with liquids without nanoparticles or larger particles, strong temperature dependence of thermal conductivity, and significant increases in critical heat flux in boiling heat transfer. Fluid flow and heat transfer of nanofluid in different geometries have been studied by several authors such as Santra et al. [9], but there are little works related to the nanofluid flow in