Influence of salt mixture on the heat transfer during spray cooling of hot metals

A hot aluminum alloy AA6082 disc at 560 °C was cooled by a spray nozzle with a constant volumetric spray flux of 3 kg/m2/s. The temperature history during the cooling process was recorded with use of an infrared camera. The influence of salinity in the cooling water was observed by dissolving various concentrations of MgSO4 to the deionized water. Deionized water was used as the reference. Moreover, eight different types of real solution used in the metal processing industry were compared. The heat transfer coefficient α in the film boiling, maximum heat flux, as well as the Leidenfrost and DNB temperature increase with the electrical conductivity (EC) of the real solutions. EC is introduced as a mean to measure the salinity in the cooling water. The change of salinity content in the cooling water must be maintained by product quality control in industries as it can significantly lead to the change of the cooling rate.