Experimental study on thermal performance of water/nano-phase change emulsion through a mini- and micro-channel stacked double-layer heat sink

Abstract

The temperature of the cooling fluid in single-layer micro-channel heat sinks (SL-MCHHSs) increases along the flow direction that leads to non-uniform temperature distribution and high thermal stress. In addition, the corresponding pressure drop in SL-MCHHSs is also higher as compared to the traditional heat sinks. The main aim of this study is to solve the problems of high temperature gradient and pressure drop by using the novel double-layer mini/micro-channel stacked heat sink (DL-MMCHHSs). In the present investigation, an experimental study is performed on the heat dissipation efficacy of a DL-MMCHHS with H2O/nano-phase change emulsion (NPCE) as the coolant. NPCEs are popular coolants owing to their high storage capacity during phase change. The pressure drop and the heat dissipation efficacy of this design of heat sink with NPCE are important parameters, which should be obtained in this study. Compared with a SL-MCHHS, this design can effectively reduce the pressure drop and increase the heat dissipation efficacy. The results reveal that the DL-MMCHHS is dominated by the pressure drop of the micro-channel. When the NPCE with the mass fraction of 9.04% is used instead of H2O in the micro-channel, the heat transfer coefficient is enhanced by 112.4% at Re=1114.88 and Q˙u/l*=0.50. The NPCE with higher mass fraction provides higher convection heat transfer coefficient defined by the inlet temperature. The wall temperature decreases with the decrease in the flow rate ratio. The maximum wall temperature depression of 67% can be achieved by using the NPCE as compared with H2O. Eventually, the uniformity index declines as the mass fraction of NPCE increases.