Contact angle measurements in the refrigerant falling film evaporation process

作者：Li, Guoli; Liu, Jinping^*; Xu, Xiongwen^*; Lu, Xingbin; Chen, Jianxun

来源：International Journal of Refrigeration, 2020, 112: 262-269.

DOI：10.1016/j.ijrefrig.2019.12.017

• Contact angle
• Superheat
• Wettability
• Refrigerant

Rivulet is a very common form of flow during the refrigerant falling film evaporation process. In this work, a visual refrigeration cycle system is designed to observe the evaporative flow characteristics of R134a. The cross-sectional profile of the liquid film is obtained using a camera equipped with a charge-coupled device (CCD HV1351UM), after which the contact angle is measured by an edge detection technique and circle fitting under superheated conditions (0.2-1.8 degrees C). In the image fitting process, the pixels with the largest coefficient of determination (R-2) are selected for fitting. The data show that the contact angle increases with the wall superheat because the increase in the wall superheat intensifies the evaporation at the contact line. In conclusion, we show that the measured contact angles lie close to the curve, theta = 12.12 Delta T-0.343.