Effect on noncondensable gas on laminar film condensation along a vertical plate fin

Laminar film condensation along a vertical plate fin in the presence of a noncondensable gas is numerically investigated. In the present analysis, the gas mass fraction and temperature: at the liquid-vapor interface is regarded as the spatial variation along the fm surface. Governing boundary layer equations together with their corresponding boundary conditions for the condensation system and the one-dimensional fin heat conduction equation with its negligible tip leakage are cast into dimensionless forms. The resulting system of equations is solved by using the central finite-difference approximation for the fin and local nonsimilarity method for boundary layer equations, Results show that the fin efficiency decreases with increasing the thermal resistance ratio of fin-to-liquid Nc, and relatively small amounts of the noncondensable gas in the bulk of the vapor have a significant effect on the fin efficiency for small values of Nc. In addition, the interface temperature is not equal to the fin temperature along the vertical fin, and the local heat transfer coefficient is not uniform, either. (C) 1998 Elsevier Science Inc. All rights reserved.