Spray cooling using multiple nozzles: visualization and wall heat transfer measurements

Time- and space-resolved heat transfer data on a nominally isothermal surface, cooled by two spray nozzles, were obtained using an array of individually controlled microheaters. Visualization and measurements of the liquid-solid contact area and three-phase contact line length were made using a total internal reflectance technique. The spacing between the nozzles and the heated surface was varied between 7 and 17 mm. Little interaction between the two sprays was observed for the tested conditions, with the heat flux due to a single nozzle remaining comparable to that due to two nozzles, provided the areas considered were limited to the regions impacted by the sprays. Variations in the heat transfer across the surface, however, increased significantly with decreasing nozzle-to-heater spacing. The phase change heat transfer was strongly correlated with the length of the three-phase contact line and was not correlated with the wetted area.