Numerical Investigation of the Impact of Subcooling Inlet on Water Flow Boiling Heat Transfer Through a Microchannel

Abstract

The effect of subcooling inlet has a big effect of the flow patterns for the flow boiling through a microchannel. Higher subcooling lower mass flux will delay the nucleate boiling and vice versa. The water flow boiling inside a microchannel has been analyzed numerically. The microchannel depth was 0.24 mm while the length was 40 mm. The supplied heat fluxes were 500 kW·m-2, 1000 kW·m-2and 1500 kW·m-2 with mass velocities of 400 kg·m-2·s-1 and 800 kg·m-2·s-1. The degrees of subcoooling of inlet water were 5oC, 10oC, 15oC, 20oC, and 25oC. The results showed that the degree subcooling has a considerable impact on both the wall temperature and flow patterns. The rise in the degree of subcooling kept the nucleate flow boiling and retarded the development of convective boiling. In addition, there was a reflection point at which the impact of heat flux on the average of the convective coefficient of heat transfer was altered. The increase in the heat flux may lead to an increase or reduction in the average HTC with respect to the location of the reflection point. The reflection points were 7oC and 5oC for the mass velocities 400 kg·m-2·s-1 and 800 kg·m-2·s-1. Thus, both the degree of subcooling and the heat flux should be simultaneously considered when it comes to the enhancement of HTC during the flow boiling inside the microchannels.