Mass Transfer around a Cold Cylinder with Condensation of Vapor (1st Report): Mass Flux Decrease Due to Condensation of Vapor at Surface Temperatures from 200 to 250 K

摘要

A fundamental study of frost formation around a single cold cylinder was conducted using both experimental and numerical methods. We specifically examined the mass transfer around the cylinder under conditions in which a phase change of the vapor occurs in the flow. Through the experimental study, the mass flux to the cold surface of the cylinder was measured at a constant surface temperature (200-250 K). The results show that the mass flux decreases according to the decrease of the wall temperature below 230 K, although it increases above 230 K. This phenomenon cannot be expressed using the common equation with the Sherwood number, which excludes the vapor's phase change (condensation). Numerical studies calculated the flow over the cylinder, including the vapor's phase change. The scheme for compressible flow was modified to solve lower speed flow. Results of calculations show that we obtained the same tendency as that of the experiment: the mass flux decreases at low temperatures where the phase change occurs.