Investigation of droplet behaviors for spray cooling using level set method

The droplet dynamics and heat removal is one of the popular research streams in spray cooling applications. The increase in the water droplet temperature as a result of its impact on the hot solid surface would determine the efficiency of the heat removal that is crucial in some sensitive applications such as spray cooling in depressurization systems in commercial nuclear power plants. Computer modelling of the underlying mechanism of the liquid droplet interaction with the hot solid surface would be necessary. The accuracy and the reliability of these models are important in simulating the multiphysics phenomena such as droplet dynamics and heat removal. In present work, the level set method coupled with heat transfer was used to simulate the water droplet impact on an isothermal solid surface. The changes in the temperature of water droplet were found to be highly dependent upon its size and the impingement speed. Topological variations in the droplet shape as a result of its impact onto the solid wall would cause abrupt changes in the temperature of the water droplet. In addition, the droplet detachment, coalescence and flattening were found to strongly influence the temperature of the droplet which would evidently affect the heat removal efficiency in the spray cooling systems employed in the commercial nuclear power plants. Furthermore, we demonstrated that the level set method had the ability to produce more accurate estimations of the water droplet dynamics when compared to the Volume-Of-Fluid (VOF) method in simulating the droplet behavior.