Performance analysis of nanofluid-cooled microchannel heat sinks

Microchannel heat sink (MCHS) performance using copper–water (Cu–H2O) and carbon nanotube–water (CNT–H2O) nanofluids as coolants is addressed analytically in this study. The velocity and temperature distributions in the MCHS were obtained by modeling the MCHS as a porous media. The resulting velocity and temperature were then used to evaluate the thermal resistance that characterizes MCHS performance. It was found that the nanofluid reduced the temperature difference between the MCHS bottom wall and bulk nanofluid compared with that from pure fluid. This temperature difference produces a reduction in conductive thermal resistance, which is one of the two sources contributing the total thermal resistance of the MCHS. The other source of thermal resistance, termed as convective thermal resistance, was found to increase when nanofluid is employed as the coolant due to the increase in viscosity and decrease in thermal capacity. Under the condition of a given pressure drop across the MCHS, optimum values of aspect ratio and porosity that producing the minimum thermal resistance can be found. It was found that using nanofluid can enhance the MCHS performance when the porosity and aspect ratio are less than the optimum porosity and aspect ratio. When the porosity and channel aspect ratio are higher than optimum porosity and aspect ratio, the nanofluid did not produce a significant change in MCHS thermal resistance.