Gravity–capillary evaporation regimes in microgrooves

The gravity–capillary evaporation phase change in microgrooves inside a heat pipe is experimentally investigated by a visualization system. The evaporation regime, startup temperature response, and evaporation thermal resistance for gravity–capillary evaporation are evaluated and compared with those for capillary evaporation. The results identify oscillatory motion of vapor–liquid interface for gravity–capillary evaporation in rectangular microgrooves arising from the competition between gravity, the capillary force, and the shear force. In addition, the presence of gravity introduces the transition from fin–film evaporation regime to corner–film evaporation regime in rectangular microgrooves, and hence results in an overshoot startup and temperature oscillation during the process of gravity–capillary evaporation. Interestingly, the corner–film evaporation improves the evaporation phase change performance in the microgrooves.