Effect of shape change in the flow dirction of mini-channel on the flow patterns.

As a method of improving the heat transfer of vapor-liquid two-phase flow in a mini-channel, there is the method of changing the shape. However, in previous researches, only the channel cross-sectional shape has been changed. In this study, the flow patterns of vapor-liquid two-phase flow in a plate heat exchanger with straight and wavy mini-channel was visualized, and the effect of changing the shape in the flow direction and the prospects for improving the heat transfer characteristics of the heat exchanger were investigated. A visualization experiment showed that imbalance in the liquid film thickness in the annular flow region of the wavy mini-channel in the flow direction. The thickness of the liquid film in the wavy mini-channel was measured and it was found that the thickness of the liquid film in the thin sections was less than half of that in the straight mini-channel and that in the thicker sections it was about 1.4 times thicker than that in the straight mini-channel. Then the heat transfer coefficient of wavy channel was almost 1.53 times better than the straight one.