Contact angle measurements of pure refrigerants

The contact angle is the most important measurable characteristic to describe wettability, which plays a critical role in two-phase heat transfer. In this work, the contact angle of refrigerants (R134a, R22, R290, R600a, R32) with the metal copper/stainless steel/aluminum has been measured in the temperature range of 0-45 degrees C. The meniscus liquid-vapor interface of refrigerant was observed through the view port installed on the experimental pressure vessel. Its curve was fitted by Laplacian differential equations. The analysis of Laplacian curve shows that the error of contact angle measurement will increase with the decrease of the contact angle. Comparing the curve fittings of Laplacian and automatic polynomial, the defect of the automatic polynomial curve fitting in prediction area is exposed. The contact angle measurements show the super wettability of the refrigerants in regards to common material surfaces. (C) 2016 Elsevier Ltd. All rights reserved.