Mechanism of Uneven Thermal Distribution Formation during Water Cooling at Low Temperature for a Moving Plate

Abstract

In order to investigate the basic mechanism of uneven thermal distribution formation at low temperature during water cooling for a moving plate, an experimental study with full cone spray cooling or flat spray cooling was carried out.
The results obtained under certain conditions are summarized as follows.
(1) The quench point was at a temperature range between 230°C and 240°C during full cone spray cooling, and it was almost constant for a stationary plate and a moving plate.
(2) The cooling curve varied with starting temperature of cooling, velocity of the plate and water flux during flat spray cooling. Three types of thermal distribution were formed in the following order, as starting temperature of cooling decreased.
Type I: Uneven thermal distribution was formed in the case where the temperature of the whole surface after cooling is higher than the saturation temperature of water (100°C).
Type II: Uneven thermal distribution was formed in the case where the surface was cooled partially to the saturation temperature of water.
Type III: Uniform thermal distribution was formed in the case where the temperature of the whole surface was cooled to the saturation temperature of water.
(3) Both quenching during full cone spray cooling and forming of type II·III during flat spray cooling could be explained by a boiling mechanism (i.e. film boiling, transition boiling and nucleate boiling) in a temperature range of 180°C to 200°C.