Experimental investigation of heat transfer characteristics and performance of smooth and wicking surfaces in spray cooling for high heat flux applications

Abstract

In this work, studies have been conducted on heat transfer performance of both smooth and modified wicking surfaces in a spray cooling experiment for high heat flux applications. The heat transfer performance of the two surfaces in terms of critical heat flux (CHF) and heat transfer coefficient (HTC) were determined in an experiment using a two-phase thermal loop, operating with de-ionized water as the working fluid in a pressure range of 101.45–165.80 ​kPa and working fluid mass flow rates of 0.84–1.26 ​g per second. The result shows that the modified wicking surface has higher CHF of 225 ​W/cm2 at cooling temperature difference of 130 ​°C compared to 160 ​W/cm2 at cooling temperature difference of 180 ​°C for the smooth surface. Further analysis of the results indicates that, maximum HTC enhancement of 8500 ​W/m2-K is achieved at cooling temperature difference of about 100 ​°C for the modified wicking surface over the smooth surface. Using a high speed camera set at 10,000 frames per second, it was observed that there was increased surface wettability on the modified surface due to fluid wicking and spreading, with reduced Leidenfrost effect at the onset of CHF. This effect resulted in lower surface temperatures and higher CHF for the modified surface compared to the smooth surface.