Cooling Characteristics by Impinging Spray Jet of Ellipsoidal Liquid Film.

Abstract

The hydrodynamic and heat transfer characteristics of the impinging spray jet of an ellipsoidal liquid film were experimentally investigated in order to estimate the cooling performance of a rotating roll in a hot mill system. The following four conclusions were reached in the study. (1) In the case of a single spray jet, the local heat transfer coefficient at the center position depends on the forced convective heat transfer by the impinging jet. But the average heat transfer coefficient is proportional to the flow rate density of cooling water, and it does not depend on the distance between the nozzle and heated surface. (2) In the case of a double spray jet, liquid film interference occurs. The local heat transfer coefficient at the center position is greater, and the cooling performance increases with the increasing flow rate density of cooling water. (3) The cooling performance of a multi-spray jet is proportional to flow rate density of cooling water, it does not depend on the nozzle construction, distance or specifications. And there is no relation to the liquid film interference. (4) When the optimum specifications of the spray nozzle are used, the temperature at a 1.3mm depth from the surface is below 130°C according to the thermal analysis of the rotating roll.