Affiliation:
1. Department of Mechano-Aerospace Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo 152 Japan
Abstract
When a water–ethanol binary mixture condenses on a flat plate, one observes that the liquid film condensate rises locally and eventually forms many droplets on the film. Usually, filmwise condensation is expected because both substances are completely soluble in each other and they wet a copper plate well. This paper presents the droplet growth mechanism during so-called pseudo-dropwise condensation. Instability analysis is used to determine the transition from filmwise condensation to pseudo-dropwise condensation theoretically. In a stress balance at the vapor–liquid interface, the analysis considers not only the surface tension itself, but also the surface tension variation due to changes in temperature and concentration, assuming saturation conditions at the interface. Numerical results indicate that the Marangoni effect plays a more important role than the absolute value of the surface tension in pseudo-dropwise condensation. The change in surface tension with temperature is not always negative; it becomes positive for certain mixtures due to the dependence on concentration. Pseudo-dropwise condensation is only realized when surface tension increases with temperature. This analysis qualitatively predicts the critical Marangoni number experimentally observed during water–ethanol mixture condensation.
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Reference4 articles.
1. Fujii
T.
, KoyamaS., ShimizuY., WatabeM., and NakamuraY., 1989, “Gravity Controlled Condensation of an Ethanol and Water Mixture on a Horizontal Tube,” Trans. JSME, Series B, Vol. 55, No. 509, pp. 210–217.
2. Hayashi, Y., Takimoto, A., Tada, Y., and Teranishi, T., 1993, “Condensation of Binary Vapors of Immiscible Liquids,” Energy Conversion and Utilization With High Efficiency Researches Pursued by Grant-in-Aid on Priority-Area Research Supported by the Ministry of Education, Japan, pp. 235–256.
3. Hijikata
K.
, and HimenoN., 1990, “Condensation of Azeotropic and Non-azeotropic Binary Vapor Mixtures,” Annual Review of Heat Transfer, Vol. III, Hemisphere Publishing Co., pp. 39–84.
4. Mirkovich
V. V.
, and MissenR. W., 1961, “A Study of the Condensation of Binary Vapors of Miscible Liquids,” Canadian J. Chemical Engineering, Vol. 39, pp. 86–87.
Cited by
49 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献