Parametric effects of spray characteristics on spray cooling heat transfer

Spray cooling is a commending technique for removing high heat fluxes in many applications. Spray cooling is accomplished by depositing liquid droplets unto a heated surface from a spray nozzle. The characteristics of the nozzle have a far ranging effect on the amount of heat that can be removed. This research reports on experiments that quantify the effects that Sauter mean diameter, droplet number flux, and spray droplet velocity have on high heat flux removal using the spray cooling technique. The experiments systematically varied each of the spray parameters independently to assess the effects of each on the heat transfer in spray cooling. The area of interest for this research is confined to surfaces above the saturation temperature of the fluid, but below its Leidenfrost point. The main body of this research deals with high-density sprays, where the surface is flooded with liquid. Experiments were conducted with room-temperature water. It was shown that droplet velocity has the greatest effect on the critical heat flux but does not significantly affect the heat transfer coefficient. Increasing the droplet number flux was shown to increase both the heat transfer coefficient and the critical heat flux. Decreasing the Sauter mean diameter of the droplets was shown to increase the heat transfer coefficient but slightly lowers the critical heat flux. A fundamental and thorough understanding of the effects of spray parameters on spray cooling heat transfer has been achieved. This is the first time that such a systematic investigation of spray characteristics on heat transfer has been succeeded.