Steam condensation on the underside of a horizontal surface

Experiments and data analysis for the condensation of steam on the underside of a horizontal surface in a closed vessel are described. Heat transfer measurements for condensation with air and helium as noncondensables are reviewed. Observations, including photographs of the condensate configurations, related to the occurrence of dropwise condensation are also discussed. It is noted that data reproducibility over long periods of time was possible only with film condensation and that with dropwise condensation condensing surface temperatures exhibited large nonuniformities and random fluctuations with time. The well known mass transfer calculational model for accounting for the presence of noncondensable gases was found to be reasonable with air. The same model when applied to the helium data was not successful except for small gas contents. It appears that the suppression of convection that would be expected to occur with the less dense gas is counteracted by convection induced by fog or mist formation. 20 refs., 11 figs