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International Heat Transfer Conference 7

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

THE INFLUENCE OF THE THERMAL DlFFUSIVITY OF THE CONDENSER MATERIAL ON THE HEAT TRANSFER COEFFICIENT IN DROPWISE CONDENSATION

P. Waas
Lehrstuhl A fur Thermodynamik TU Munchen, Germany

Johannes Straub
Technische Universität München Arcisstr. 21, 8000 München 2, FRG

Ulrich Grigull
Lehrustuhl A für Thermodynamik Technische Universität München 80290 München Germany

DOI: 10.1615/IHTC7.330
pages 27-31

Abstract

Heat transfer measurements were performed during the condensation of pure saturated steam on five vertical condenser surfaces with copper, aluminium, brass, bronze and stainless steel as basic materials. The surfaces of the different condensers were gold-plated to guarantee the same dropwise condensation conditions on all materials used. The saturation temperature has been varied between 50 °C and 90 °C at heat-flux densities up to 550 kW /m2. The result is that the heat transfer coefficient grows with ascending thermal diffusivity, independently of the saturation temperature and the heat-flux density. This effect results from the finite thermal conductivity of the condenser material in connection with the distribution of droplets of varying size over the surface that causes a temperature field in the surface, varying with the time. Thus, in an area near the surface of the condenser, heat must be transported parallel to the surface. This event has been calculated with a numerical model, using an experimental droplet function. The agreement of the numerical results with the experimental data is satisfactory.

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