UNDERSTANDING HIGH HEAT TRANSFER IN SPRAY COOLING FOR DIFFERENT DROPLET VELOCITIES AND WALL SUPERHEATS BY 3D MULTIPHASE FLOW MODELING

摘要

Spray cooling with phase change has the advantage of relatively large amount of heat transfer from the hot surface of many power electronics system. In our previous works in 2-D model of spray cooling, the importance of moving the cooler liquid quickly to heated dry surface which causes the high heat flux due to transient conduction is recognized to be the main reason for high heat transfer. In reality the phenomena of spray cooling are three dimensional in nature. The major draw back in extending the 2-D model to 3-D model is huge computing time in serial computer. Here the 3-D model is developed in parallel computing environment to reduce the turn around time. The 3-D multiphase model used here considers the effect of surface tension between liquid and vapor, gravity, phase change and viscosity. The level set method is used to capture the movement of the liquid vapor interface. The governing equations of multiphase flow are solved using the finite difference method. In this work the spray cooling phenomena is studied in 3-D multiphase model where a vapor bubble is growing in a thin liquid film on a hot surface and a droplet is impacting on the thin liquid film. This study has been done for different droplet velocities and for different wall superheats with our 3-D multiphase model to understand the high heat removal mechanism in spray cooling for different velocities and wall superheat situations.