Effect of droplet characteristics and rotation speed on the flow and heat transfer characteristics of mist/air cooling in a rotating ribbed two-pass rectangular channel

Abstract

The flow and heat transfer characteristics of mist/air cooling in the rotating ribbed two-pass rectangular channel are numerically investigated using the CFD software ANSYS-CFX. In this article, a comparison in heat transfer performance between the mist/air cooling and the air-only cooling is performed. Additionally, the effect of the initial mist diameter, temperature, velocity and the channel rotation speed on the mist/air cooling performance is analysed. The results show that the droplet flow distance and Nusselt number of the mist/air cooling increase as the initial mist temperature decreases. In addition, as the initial mist diameter decreases, the diameter of mist on the whole channel decreases, resulting in the higher heat transfer, whilst the mist concentration also decreases, leading to the lower heat transfer. Therefore, there is an optimal initial mist diameter which makes the heat transfer performance best. Nevertheless, the droplet movement and heat transfer performance of mist/air cooling are nearly insensitive to the initial mist velocity. It is also noted that the Coriolis force increases with the channel rotation speed, causing the flow deflection becomes more obvious. Consequently, as the channel rotation speed increases, in the first passage the averaged Nusselt number on the trailing wall increases, and that on the leading wall decreases, while the trend in the second passage is reversed.