화학공학소재연구정보센터
International Journal of Heat and Mass Transfer, Vol.141, 1238-1251, 2019
Effects of flow loop components in suppressing flow boiling instabilities in microchannel heat sinks
Present work reports an experimental investigation of flow boiling instabilities in three different configurations of a flow boiling loop. The three flow configurations i.e. loop having flexible tubing and connections, loop having stiffed tubing and loop having stiffed tubing with a throttling valve have been investigated and their performances are compared. Experiments are performed with segmented finned microchannels (SMC) to investigate the roles of above mentioned components in flow boiling instabilities. The array of segmented finned microchannels are fabricated on a copper substrate with a footprint area of 10 x 10 mm(2) and experiments have been performed using deionized water at 20 degrees C subcooling. It has been observed that loop components external to the heat sink affect the heat transfer, pressure drop characteristic and assist in mitigating flow boiling instabilities. Based on the flow patterns, the slug ebullition cycle has been categorized into three distinct stages (a) slug formation (b) upstream compression and (c) flooded flushing. Cycle time and number of oscillations during upstream compression stage were reduced in the stiffed connections and throttling valve flow configurations. Heat transfer performance of the throttling valve configuration has been found to be the best among all three, followed by stiffed tubing configuration. The loop with flexible tubing connections demonstrated largest time period of slug ebullition cycle and also experienced large amplitude wall temperature and pressure oscillations. The combination of stiffed tube materials surrounding the heat sink and throttling valve at pump exit effectively reduce the flow boiling instabilities resulting in better thermal and hydraulic performance. (C) 2019 Elsevier Ltd. All rights reserved.