Abstract
This study deals with heat transfer enhancement surface manufactured by thermal spraying. Two thermal spraying methods using copper as a coating material, wire flame spraying (WFS) and vacuum plasma spraying (VPS) , were applied to the outside of copper cylinder with 20 mm OD. The heat transfer performance around the horizontal cylinder under microgravity was evaluated in pool boiling experiments with HCFG123 for heat fluxes between 1.0 and 160 kW/m2 and saturation temperature of 30°C. The microgravity experiments were carried out during a parabolic flight of an airplane. As a result, the surface by VPS produced higher heat transfer coefficient and lower superheat at the onset of boiling under microgravity. For the smooth surface, the effect of gravity on boiling heat transfer coefficient was a little. For the coated surface, a large difference in heat transfer characteristics to gravity was observed in the moderate heat flux range. Heat transfer was improved in gravity transition from hyper-gravity to microgravity. The difference in heat transfer coefficient was a little between the normal gravity and microgravity. For all the test section, test section was covered by vapor with the heat flux of 160 kW/m2 under microgravity.
