Experimental investigation of heat transfer and pressure drop of alumina–water nano-fluid in a porous miniature heat sink

The thermal management of electronic devices has become of great concern in the last decade. Recent research has focused on heat transfer enhancement methods for heat removal from such devices. In this study, we investigated the convective heat transfer and pressure drop of alumina-water nano-fluids in a miniature heat sink occupied with a copper porous medium under a 62.5 heat flux. Nano-fluid volume fractions of 0.1, 0.3, and 0.5% were synthesized by a two-step method, and the thermal conductivity and kinematic viscosity of the nano-fluids were measured experimentally. Two copper metal foam heat sinks, with different pore densities of 15 pores per inch (PPI) and 30 PPI, were manufactured and inserted into a channel. The results indicated an enhancement in the convective heat transfer coefficients and Nusselt numbers with increase in the Reynolds number. The enhancement in the heat transfer coefficients using different nano-fluid volume fractions in higher- and lower-porosity media varied from 1 to 22% and 2.3 to 26.4%, respectively. An increment in the nano-fluid volume fraction, and pore density, led to a higher heat transfer rate. However, the higher pore density medium caused larger pressure drops. The thermal resistance of the samples was also studied. The results indicated an increase in Reynolds number, and volume fraction decreased the thermal resistance. According to the efficiency index, a lower pore density medium as well as higher nano-fluid volume fractions provided better performance in this porous heat sink.