Experimental investigations on a novel instability suppression mechanism for subcooled flow boiling in microchannel heat sink

Abstract

Flow boiling instability reduces the thermo-hydraulic performance of microchannel heat sink (MCHS) considerably. High rate of vapor bubble generation and their rapid growth block the confined flow passage of the microchannel and induce high flow resistance. Periodic changes in flow regimes and inefficient vapor venting lead to backflow. It increases dry out period and reduces overall heat transfer coefficient in MCHS. In this research, a novel instability suppression mechanism using Inlet Plenum Flow Restrictor (IPFR) is proposed. The subcooled flow boiling experiments are performed in a MCHS using degassed deionized-water (DI water). The inlet fluid temperature is maintained at 78 ± 1 °C (subcooling of 22 ± 1 °C). The results are reported for mass flux of 220, 320 and 416 kg/m2s and heat flux in the range of 21–88 W/cm2. The instability is observed to reduce by 76 % for surface temperature, 74 % for inlet plenum fluid temperature and 52 % for outlet plenum fluid temperature. Hence, the temperature instability is improved by 67 %. The heat transfer coefficient is increased by 13 % and pressure drop penalty is reduced by 34 % for stable operation of MCHS.