Measurement of Condensate Film Thickness for Solutal Marangoni Condensation

During solutal Marangoni dropwise condensation of a water-ethanol vapor mixture, condensation was observed by a high-speed camera while condensate film thickness was measured by the laser light extinction method. Good correspondence was observed between the film thickness data and the observed condensate behaviors. Minimum condensate film thickness occurred immediately after a departing drop swept by and decreased with increasing initial drop distance in the steep increase region of the condensation characteristic curve. In the region of higher cooling intensity, both initial drop distance and minimum condensate thickness increased with cooling intensity.The smallest thickness of the condensate film was less than 1 mu m. A close relationship was confirmed to exist among condensate film thickness, initial drop distance, and heat transfer characteristics.