Direct Numerical Simulation of Heat Transfer in Spray Cooling Through 3D Multiphase Flow Modeling Using Parallel Computing

Thermal management issues have become a major bottleneck for further miniaturization and increased power consumption of electronics. Power electronics require more increasing use of high heat flux cooling technologies. Spray cooling with phase change has the advantage of large amount of heat transfer from the hot surface of many power electronics. Spray cooling is a complex phenomenon due to the interaction of liquid, vapor, and phase change at small length scale. A good understanding of the underlying physics and the heat removal process in spray cooling through numerical modeling is needed to design efficient spray cooling system. A computational fluid dynamics based 3D multiphase model for spray cooling is developed here in parallel computing environment using multigrid conjugate gradient solver. This model considers the effect of surface tension, gravity, phase change, and viscosity. The level set method is used to capture the movement of the liquid-vapor interface. The governing equations are solved using finite difference method. Spray cooling is studied using this model, where a vapor bubble is growing in a thin liquid film on a hot surface and a droplet is impacting on the thin film. The symmetry boundary condition considered on four sides of the domain effectively represents a large spray made up of multiple equally sized droplets and bubbles and their interaction. Studies have also been performed for different wall superheats in the absence of vapor bubble to compare the effect of two-phase heat transfer compared to single-phase in spray cooling. The computed interface, temperature, and heat flux distributions at different times over the domain are visualized for better understanding of the heat removal mechanism.