FILM CONDENSATION GENERATED BY A FORCED COOLING FLUID

In this paper we analyze the condensation process of a saturated Vapor in contact with one side of a vertical thin plate, caused by a forced flow on the other surface of the plate. The effects of both longitudi nal and transversal heat conduction in the plate are considered. Due t o the finite thermal conductivity of the plate, a longitudinal tempera ture gradient arises within it changing the mathematical character of the problem from parabolic to elliptic. The momentum and energy balanc e equations are reduced to a system of integro-differential equations with five parameters: the Prandtl (Pr-c) and a Jakob (J alpha) numbers , a non-dimensional plate thermal conductivity alpha, the aspect ratio of the plate epsilon and beta defined by the ratio of the thermal res istance of the condensed layer to the thermal resistance of the forced cooling how. In order to obtain the spatial evolution of the condense d layer thickness and the related temperature of the plate as a functi on of the longitudinal coordinate position, the coupled balance equati ons are integrated in the asymptotic limit J alpha --> 0, including th e cases of very good and poor conducting plates. For finite values of the parameters alpha and beta, this paper shows that effect of the hea t conduction through the plate modifies the classical Nusselt solution substantially. Two terms of the asymptotic expansions, for the limiti ng case of alpha --> infinity and finite beta, are enough to reproduce the temperature distribution and the condensed layer thickness evolut ion with high accuracy even for values of or of order unity.