Modeling of Bubble Growth Under an Impinging Free Planar Water Jet

Abstract

ABSTRACTDeveloping a wall heat flux-partitioning model (WHFP) would reduce the empiricism commonly encountered in modeling of jet impinging boiling (JIB). An integral and necessary part of any WHFP model is a method to predict the area fraction on the heated surface influenced by bubble generation. Addressing such need, a scenario identification procedure (SIP) has been developed to predict bubble growth termination (BGT) during JIB. Two conditions have been considered in determining the most probable BGT scenario for JIB configuration: (1) the thermal equilibrium of the bubble with the surrounding liquid bulk, and (2) the dynamic equilibrium of forces acting on the bubble. If the bubble diameter corresponding to thermal equilibrium is reached first, then most probably the bubble will locally collapse. If the bubble diameter associated with dynamic equilibrium is reached first then bubble departure and sliding along the heated surface are expected to take place. The BGT predictions obtained using the developed SIP has been validated using visual observations of nucleate JIB on a horizontal flat surface. The planar free water jet velocity, degree of water subcooling, and surface superheat were varied between 0.4 m/s and 1.7 m/s, 10°C and 28°C, and 0°C and 30°C, respectively. Bubble dynamics was observed over a span of the heated surface from jet stagnation 10 ten jet widths. Experimental results show that the proposed SIP is capable of predicting both the prevailing BGT scenario and the maximum bubble diameter reasonably well. As mentioned before, these are very important elements in developing a WHFP model for JIB.