INFLUENCE OF WATER TEMPERATURE ON HEAT TRANSFER COEFFICIENT IN SPRAY COOLING OF STEEL SURFACES

Cooling of stainless steel surfaces with flat fan nozzles was studied experimentally. Several configurations of jets and pressures were tested. Tests were done with variable coolant (water) temperatures (20 °C, 40 °C, 60 °C and 80 °C). The influence of coolant temperature on the heat transfer coefficient was investigated. An increase in coolant temperature caused a significant decrease of the Leidenfrost temperature (temperature at which the character of boiling is changed - the film boiling is changed into nucleate boiling). Changing the water temperature from 20 °C to 80 °C caused a change of the Leidenfrost temperature of about 140 °C. Furthermore it was observed that in a high temperature region (above Leidenfrost temperature) the heat transfer coefficient has the highest value for the lowest water temperature and for the high coolant temperature (80 °C) the cooling intensity is the lowest.