Traditional thermal solutions are reaching their practical limits on heat removal requirement for processers with high circuit power density over the coming years. The implementation of forced convective boiling in microchannels is a promising alternative, as attainable heat transfer rate is very favorable. In this study, the instabilities of two-phase boiling flow in a single microchannel are computationally explored by utilizing commercial software. Based on previous studies, numerical results get really qualitative agreement. For the steady state, the bubble growth, from isolated bubbles to elongated bubbly flow near the outlet region, can be exactly observed in the current simulation. As for transient analysis, boiling regimes are investigated in terms of two specified mass velocities. The time-dependent fluctuations in wall temperature are given to indicate the transition of different flow patterns and the effect of varied mass flux. In addition, boiling mechanisms are found to be strongly dependant on wall surface conditions. A comparison of the computed flow boiling in a microchannel with reentrant cavities on side walls to experimental results is performed. The cavities are shown to help to facilitate boiling nucleation, enhance the critical heat flux, and reduce the superheat for the boiling onset. Finally, the size effect of nucleation sites is analyzed and addressed, the cavity diameter and depth being carefully considered. Based on the compatible view, the optimal configuration of reentrant cavities is located.

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