Simultaneous Boiling Visualization and Heat Transfer Measurement of Two Adjacent Water Impinging Jets

Abstract

The effect of jettojet distance of two adjacent jets on boiling heat transfer was investigated by a simultaneous boiling visualization and heat transfer measurement. The hydrodynamics of two adjacent jets were visualized by the highspeed imaging and the 4K camera on unheated surface. The surface temperature of the hot steel plate was estimated by formulating 2D inverse heat conduction, which was measured through the flatplate heat flux gauge. The jet Reynolds number was fixed at Re = 17,000 and the jettojet distance of two adjacent jets was set to the three different jettojet distances (p/d = 10, 20 and 30). The wall jet flow interference between two adjacent impinging jets forms a vertical fountain at its boundary. The more scattered water droplets are observed from the fountain due to the higher intensity at the p/d = 10. The flow interaction becomes to reduce its momentum as increasing the p/d. The boiling visualization shows which boiling mode starts to occur and turns to be disappeared from film boiling to nucleate boiling on the hot surface. The measured surface temperature has a good agreement with the corresponding boiling visualization. The closer jet distance (lower p/d) shows the rapid temperature gradient along the interaction, which provides much higher cooling rate in a multiple jet nozzle when designing an intensive quenching device.