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International Heat Transfer Conference 12

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Unsteady Measurement of Condensate Film Thickness for Solutal Marangoni Condensation

Yoshio Utaka
Yokohama National University, Department of Mechanical Engineering, Tokyo Institute of Technology 2-12-1 0-okayama, Meguro-ku Tokyo 152 JAPAN; School of Mechanical Engineering, Tianjin University, 135 Ya Guan Rd. Tianjin Haihe Education Park, Jinnan District, Tianjin300350, China; Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education, China

Tetsuji Nishikawa
Air Liquide Japan

DOI: 10.1615/IHTC12.600
6 pages

Abstract

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.

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