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International Heat Transfer Conference 6

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

HEAT TRANSFER IN NATURAL CONVECTION BOILING OF POLYNARY MIXTURES

Karl Stephan
Institut fur Technische Thermodynamik und Thermische Verfahrenstechnik, Universitat Stuttgart, Pfaffenwaldring 9, 70550 Stuttgart, Germany

P. Preusser
Institut fur Technische Thermodynamik und Thermische Verfahrenstechnik, Universitat Stuttgart, FRG

DOI: 10.1615/IHTC6.3790
pages 187-192

Abstract

Experiments on pool boiling of mixtures mostly conducted on miscible binary mixtures close to atmospheric pressure, clearly indicate a reduction of heat transfer as compared with that for pure substances, an effect which is usually explained by a diffusion resistance between liquid and vapour. Furthermore the nucleation site density for a given heat flux is smaller than that of a reference mixture with the same thermal properties as the real mixture but vanishing concentration difference between the two phases. This result already predicted from the Gibbs-potential for binary mixtures continues to hold for polynary mixtures, as shown in the present paper. In order to explore the reduction of heat transfer in polynary mixtures, experiments outside a horizontal tube were done with 25 miscible ternary mixtures of methanol, acetone and water. Based on the experiments correlations could be constructed for the evaluation of heat transfer coefficients. They are built up from those of the ternary reference mixture and the corresponding binary mixtures, a procedure well known in thermodynamics of multicomponent systems. It is suggested that this model may also be applied to polynary mixtures with an arbitrary number of components.

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