| The research presented in this dissertation is an experimental and theoretical investigation of spray cooling with an air atomizing nozzle. The study focuses on the heat transfer processes when a dense spray impinges on a surface whose temperature is below the Leidenfrost point. The heat transfer is characterized by the range of water and air flow rates. The spray droplet size and velocity, liquid film thickness and flatness were measured using phase Doppler, Fresnel diffraction, and holographic techniques. An analytical method for calculating the liquid film thickness and velocity distribution within a liquid film deposited on a surface by gas atomized spray has been developed based on easily measured flow field parameters. The effect of spray and liquid film characteristics on the heat transfer and critical heat flux was also studied. Mechanisms of the heat transfer in three different regions of spray cooling, i.e., surface temperature below the saturation temperature, above the saturation temperature and at the point corresponding to the critical heat flux are identified. The experimental data and the modeling provide evidence that the proposed mechanisms do control the heat transfer. This study is a comprehensive work based on the spray parameters, liquid film characteristics, and heat transfer phenomena at the surface to explain the spray cooling heat transfer process. |
