Transient spray cooling: An analytic predictive approach

This study examines transient spray cooling of a heated substrate under a single nozzle, a situation commonly encountered in spray cooling or quenching applications. The temperature range is such that the cooling process goes through the three cooling regimes in time—film boiling, transitional boiling, and nucleate boiling. The heat transfer associated with each drop impact is computed using validated theoretical expressions for each of the boiling regimes. These theoretical expressions and limits for delineating the three boiling regimes are taken from literature. The principle of superposition is then applied, using the local number flux of impacts on the surface, to compute the rate of heat transfer from the substrate. The simulation is performed over time as a full conjugate heat transfer problem, with the temperature decrease in the substrate being computed using a finite difference method. This predictive approach is validated using existing experimental results and then used to investigate the influence of various spray parameters on the cooling performance of a flat plate.