Characteristics of quenching high temperature cylindrical surface with an impinging jet. Relationship between flow aspect and heat transfer

An experimental study has been conducted to understand characteristics of transient heat transfer during quenching a hot cylindrical block with an impinging water jet. The experiment was done at atmospheric pressure for the following condition: an initial block temperature of 250 and 300degC, a subcooling of 20-80 K, a jet velocity of 3-15 m/s, and a nozzle diameter of 2 mm. The surface temperature and heat flux are estimated by applying two-dimensional inverse solution to the measured temperatures in the block during the quench and then the flow configuration on the surface during the quench is synchronously observed with high speed video. As a result, the changes in the surface temperature and in the surface heat flux are clearly shown with movement of the wetting front. The resident time at which the wetting from starts spreading after the impingement of jet can be predicted by a proposed correlation. The fundamental character of how the surface temperature and heat flux changes with the wetting front, can be understood. (author)