Bubble dynamics under an impinging jet

Abstract

Wall heat flux in the case of jet boiling is greatly dependent on bubble size under the jet. A new force balance model has been proposed to determine bubble size addressing the dynamic effect of the jet on a growing bubble. Jet dynamics cause extra two force components compared to flow boiling case: asymmetric bubble growth force for a moving fluid and pressure force caused by jet stagnation. The model can not be completed without studying bubble growth under the jet. Bubble growth has been studied in the stagnation region for jet velocity of 0:65;0:8, and 0:9 m=s and degrees of subcooling of 13; 20, and 30 C and in the parallel flow region for jet velocity of 0.85 m/s and 7 C of subcooling. The instantaneous diameter of the bubble has been measured on the boiling surface by a high speed camera. As the force balance depends on bubble growth rate, Zuber model for non-uniform temperature field is found to best represent the experimental data with different b values.