Effect of Ambient Pressure on Bubble Growth in Micro-Channel and Its Pumping Effect

Over the last two decades, explosive boiling has been widely used in industry, many researches have been dedicated to study its aspects. Some applications of explosive boiling are in thermal bubble jet printers, micro-injectors and micro-medicine devices. In such applications ambient pressure is not usually the atmospheric pressure. To have a good design, there is a great need to simulate the bubble growth under non-atmospheric pressure. In this research a three dimensional numerical analysis of growth and collapse of a bubble in a micro-channel under four different ambient pressures is presented. Flow3D package which solves the Navier-Stokes equations with surface tension effects, is used to reach this aim. Leinhard’s equation is used to compute the temperature of explosive boiling in various pressures. It is considered that the internal pressure of the bubble has an exponential form. Bubble dynamics relations have been used to obtain time constant of the bubble. The bubble volume and the flow rates from both ends of the microchannel are obtained. It has been shown that increasing in the ambient pressure causes decreasing in the bubble volume. Numerical results for the growth and collapse of the bubble in the micro-channel are compared with those of experiments under similar conditions. Results of the growth and collapse of the bubble in the micro-channel of a printer, BJ-80, have been used to validation. Comparisons show that the bubble evolution is well predicted by the numerical results.