Heat transfer peculiarities and crisis phenomena development in spray cooling using various types of nozzles

Spray cooling is one of the most effective methods for two-phase cooling but the mechanism of heat transfer and crisis phenomena development remains partially elusive due to the diverse range of phenomena observed during droplet impingement, boiling and dry spots formation in liquid film. This study focuses on spray cooling of subcooled water of a silicon surface using both pressure nozzle and atomizer at different liquid flow rates and nozzle-to-surface distances. Experiments show that for different nozzle types, the optimal distance for maximizing heat transfer is noticeable less than the distance where the spray cone fully covers the heated area. In order to achieve the highest critical heat flux (CHF), it is essential to select the distance that minimizes local temperature maximum. The temperature field non-uniformity in spray cooling depends on the nozzle-to-surface distance, spray flow parameters, and heat transfer mechanism. It's revealed that the development of intensive boiling in the liquid film changes the heat transfer curve slope and significantly reduces cooling non-uniformity. CHF values of 13.2 and 10.2 MW/m2 are attained for pressure nozzle (Q = 24.2 mL/s) and atomizer (Q = 6.6 mL/s), respectively.