microchannel, flow boiling, flow reversal, instability
Flow boiling in micro-channels have significantly different characteristics from flow boiling in larger channels. One particular behavior of micro-channel boiling is the instability that results in oscillations and flow reversals. This has been a unique challenge for researchers, and a satisfactory solution that eliminates the instability without a substantial performance penalty has not been found. In this study, a simple analytical model based on mass and momentum conservation is developed to identify the mechanistic conditions corresponding to the conditions of flow reversal in a boiling flow in micro-channels. The results indicate that flow reversal can occur when a rapid evaporation occurs near the inlet of the channel. The model also confirms the observations of existing studies that, if a large pressure differential in the channel is imposed in combination with a throttling section before the inlet, the flow reversal can be suppressed.