Determination of rewetting velocity during jet impingement cooling of hot vertical rod

A vertical hot rod of 12 mm diameter at 800 +/- A 10 A degrees C initial temperature has been quenched by sub-cooled round water jet. The water jet of 2.5 and 3.5 mm diameter, at jet Reynolds number of 5000-24,000, impinges normal to the test section of SS-316. An infrared camera is used to determine the wetting front velocity on the hot test surface. The investigations are made up to 40 mm downstream locations in both upper and down sides of the stagnation point. It has been observed that during transient cooling, the wetting front velocity increases with the rise in jet Reynolds number and jet diameter. However, rewetting velocity reduces drastically for the extreme downstream locations away from the stagnation point. The reduction in the wetting front progression for the upper side downstream locations is higher as compared to corresponding bottom side locations. The correlation proposed for the dimensionless rewetting velocity predicts the experimental data of upper and bottom side downstream locations in the error band of +30 to -20 %.