Some Experimental Observations of Dropwise Condensation of Steam.

摘要

Using a tiltable steam condenser test section, the parametric effects of heat flux, non-condensable gas, promoter, condenser surface thermal resistance, and surface inclination were studied on a 3.18 mm thick flat copper plate and on 0.051 mm thick foils of copper and titanium. Any non-condensable gas concentration, however small, reduces the heat transfer coefficient significantly during dropwise condensation. Non-condensable gases also cause large surface temperature fluctuations, resulting in difficulties of accurately measuring heat transfer coefficients. The recorded data for the heat transfer coefficient of this experiment is lower than previous investigations, possibly due to a concentration of non-condensable gases which resulted from the low steam velocity past the condenser surface or due to the effects of the thin condenser surfaces used. With a vertical, copper surface, the heat transfer coefficient increases by a factor of five when the condenser surface thickness increases from 0.051 mm to 3.18 mm. The heat transfer coefficient is higher for dropwise condensation on copper than for titanium with mixed condensation. Surface inclination from the vertical position decreases the heat transfer coefficient by as much as 50 percent. (Author)