Abstract
Dropwise condensation heat transfer coefficients can be calculated from the density of drop-size distribution and the growth rate of drops. In the case of steam including non-condensable gases the heat transfer coefficient can be calculated. The purpose of this study is to investigate the effect of pressure and non-condensable gas concentration for dropwise condensation heat transfer. Furthermore, the validity of the density of drop-size distribution formula in the presence of non-condensable gases proposed by Tanaka is evaluated. Heat transfer coefficients are measured in the air mole fraction range between 1 % and 25 % and in the pressure range between 0.1 MPa and 0.4 MPa. And drop diameters and drop numbers are measured using image analysis. As a result, the theoretical formula proposed by Tanaka is applicable when non-condensable gas concentration is 25 % or less.
