Microchannel Geometries and Rough Surfaces for Critical Heat Flux Enhancement in High Pressure Pool Boiling

Abstract

This paper presents the performance of pool boiling heat transfer (PBHT) from square, parabolic and stepped microchannel under steady and exponential heat supply. The experiments are conducted at pressure ranging from 1 to 10 bar. The effect of channel profile on transient CHF is presented. The channel top and base width of square microchannel is 0.5 mm. The channel base width of parabolic and stepped microchannel is same as that of square microchannel, however, its channel top width is 0.8 mm. The channel height and number of channels are 0.5 mm and 9, respectively. The scratches are formed unidirectionally on the plain surface to attain surface roughness in the range of R<inf>a</inf> = 0.106 to 4.03 µm. The comparison of CHF for surface roughness and microchannel surfaces is also carried to emphasis the effect of structured surfaces. The bubble morphology is studied with the help of 1000 fps high-speed camera. The microchannel geometries enhance the steady and transient CHF at all the operating pressures. However, exponential transient rate has insignificant role in the transient CHF. The forces exert during the bubble growth on the bubble meniscus is considered to determine the bubble departure diameter of the microchannel at all the operating pressures. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.