An experimental investigation of single- and two-phase flow in copper and aluminum microchannel heat sinks

In this study, single- and two-phase flow and heat transfer characteristics in copper and aluminum heat sinks were investigated experimentally. Deionized water was used as the working fluid in the experiments. Two-phase flow tests were performed at low vapor qualities (∼0.1). Each heat sink has a square shape of 20 mm × 20 mm. Heat sinks have 15 parallel microchannels. The hydraulic diameters of the channels range from 400 to 500μm, and their aspect ratios range from 0.4 to 2.5. The effects of material and aspect ratio on two-phase flow were studied. Experimental Nu values for single-phase flow were found to vary with an increasing trend between 4.6 and 7.2 values. The data overlap with the data obtained from the Sieder-Tate correlation for Re > 280. For Re < 280, the difference reaches 25%. The pressure drop in two-phase flow is 2.5 times higher than that measured in single-phase flow. The heat transfer coefficients of two-phase flow decreased with increasing the degree of vapor quality and increased with increasing mass flow rate. Heat transfer coefficients were found to be higher for 2.5 aspect ratio than coolers with similar hydraulic diameters. Additionally, the heat transfer coefficients of the copper heatsink were higher than those of aluminum.