Abstract
The enhancement of drop-wise condensation heat transfer was examined for steam at 0.1 MPa by using grooved-heat transfer surfaces. The drop-wise condensation was attained by plating the surface with gold. In the case that the surface was flat, the drop-wise condensation heat flux was of course much higher than that of the film-wise condensation. The drop-wise condensation heat flux on the grooved heat transfer surface that was defined hypothetically by the flat surface was larger than that of the flat heat transfer surface. When the top and the wall of the groove were plated with gold, the hypothetical drop-wise condensation heat flux was highest. Next was the case that the top, the wall and the bottom of the groove was plated and third was only the top of the groove was plated. It appeared in the recorded high speed video images that condensate drops on the top and the wall of the groove was pull down to the bottom of the groove. As a result of it, the bare area that was exposed to steam seemed to increase. When the groove size was increased from 2 mm to 3 mm, the enhancement of the drop-wise condensation heat flux was mitigated.
