EFFECT OF 2-DIMENSIONAL CONDUCTION IN THE CONDENSATE FILM ON LAMINAR-FILM CONDENSATION ON A HORIZONTAL TUBE WITH VARIABLE WALL TEMPERATURE

Earlier solutions of the problem of laminar film condensation on a hor izontal tube with variable surface temperature have assumed locally ra dial conduction across the condensate film. The present paper describe s an investigation of the effects of two-dimensional conduction, inevi tably present when the surface temperature of the tube is non-uniform. It was found that the simple approach is conservative and only signif icantly in error for (mu k(Delta T)over bar>)/rho<(rho)over tilde>gd(3 )h(fg))(1/4)greater than or equal to about 0.01, i.e. around the highe st value which might be found in practice of the dimensionless paramet er. When the streamwise convection term is included in the energy equa tion for the condensate film, the results depend (very weakly) on the additional parameter rho<(rho)over tilde>gd(3)c(p)/mu k, but are negli gibly affected in the practical range. Copyright (C) 1996 Elsevier Sci ence Ltd.