ISSN Online: 2377-424X
International Heat Transfer Conference 12
Unsteady Measurement of Condensate Film Thickness for Solutal Marangoni Condensation
Abstrakt
The simultaneous measurement of the condensate film thickness using the laser light absorption by condensate
liquid and observation of condensation using a high-speed camera were performed for solutal Marangoni
dropwise condensation of water – ethanol vapor mixture. Good correspondence between the measuring film
thickness data and condensate behavior was observed. The heat transfer surface always covered by the
condensate film and was wetted. The minimum condensate thickness appeared after the sweeping of departing
drop decreased with increasing initial drop distance in the steeply increase region of the condensation
characteristic curve. In the region of larger cooling intensity, both initial drop distance and minimum condensate
thickness increased with cooling intensity. Observation of the minima of the minimum condensate thickness
almost agreed with minimum initial drop distance. Since the initial drop distance and minimum condensate
thickness were a minimum in the surface subcooling region near to the maximum heat transfer coefficient in the
heat transfer characteristic curve, the surface tension difference acting as the driving force behind the generation
of a thin and irregular condensate film increased with heat transfer coefficient. Therefore, the close relation
among the condensate film thickness, the initial drop distance and the heat transfer characteristics was
confirmed.