TED-AJ03-604 EFFECT OF VAPOR VELOCITY ON CONDENSATION HEAT TRANSFER FOR WATER-ETHANOL BINARY VAPOR MIXTURE
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概要
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When the binary vapor mixture forms "positive system", in which the surface tension of the component of high boiling point is larger than that of low boiling component, condensate of irregular thickness such as dropwise mode often appears. The solutal Marangoni condensation, which is driven by surface tension difference due to concentration distribution on condensate surface, appears remarkably for vapor mixture of water-ethanol, water-ammonia and so forth. The condensation characteristic curve, which shows the change in heat transfer coefficient to the surface subcooling, exhibited the non-linear change due to a transition phenomenon with change in condensate modes. The nature of the condensation characteristic curve is summarized Table A-1. In the study, condensation curves were measure over a wide range of vapor velocity from 0.3 to 68m/s for three ethanol mass fractions of 0.09,0.32 (Fig.1) and 0.53 to clarify the heat transfer characteristic of water - ethanol solutal Maragoni condensation. Results and conclusions are as follows : (1) Under any vapor concentration, the whole region of condensation curves shifted towards greater heat transfer coefficient with increasing vapor velocity. (2) The dependency of maximum heat transfer coefficient on the vapor velocity was comparatively low showing a different trend compared to that of the dropwise condensation on a lyophobic surface. (3) Good agreement in variations of maximum heat transfer coefficient to the departing drop size was exhibited between solutal Marangoni condensation and dropwise condensation on a lyophobic surface as shown in Fig.2. The maximum heat transfer coefficient was proportional to power of around -0.35 of departing drop diameter. Thus, it is likely that the main heat transfer is through the thin liquid film among drops similar to dropwise condensation on a lyophobic surface, where heat transferred mainly through small drops.[figure]
- 一般社団法人日本機械学会の論文
著者
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Utaka Yoshio
Department Of Mechanical Engineering And Materials Science Graduate School Yokohama National Univers
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Kobayashi Hironori
Matsushita Electric Co.
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