COUPLED HEAT TRANSFER PHENOMENA IN CAVITATING BUBBLE DYNAMICS

摘要

Cavitation is an incipient technique that finds application in advanced medicine, engineering and chemistry, where the high temperature and pressure of the cavitating bubbles are used as micro-reactors. However, present models to study the dynamics of cavitating bubbles have ignored important aspects of the transport phenomena, such as the actual gas and liquid thermal boundary layers across the bubble interphase. This leads to gross inaccuracies in estimating the heat transfer between the liquid and the gas, and to wrong interphase temperatures. In order to depth the understanding of this complex phenomena, a more realistic model has been developed, which includes the radial variation of the flow variables. In this model, the heat transfer across the bubble interphase is given directly by the coupled gas and liquid boundary layers. Other physical phenomena, such as, mass transfer and chemical reactions, have also been accounted for. The new model is able to predict the dynamics and internal state of the bubble with more accuracy than existing methods, allowing a more comprehensive knowledge of the bubble physics. In particular, it has been shown that the bubble dynamics depends heavily on the pressure difference across the bubble interphase. The predicted maximum temperature at the center of the bubble is slightly larger than that given by uniform models, whereas the calculated interphase temperature has been reduced to experimental values. Finally, the radial dependence of the temperature, pressure and chemical concentrations allows a more detailed analysis of the reaction processes occurring inside the bubble.