Simple heat transfer model for laminar film condensation in a vertical tube

► We propose a new physical model for laminar film condensation. ► The model considers the effects of gravity, liquid viscosity and vapor flow in the core. ► To estimate the velocity profile in the liquid film, the liquid was assumed to be in Couette flow forced by the interfacial velocity at the liquid–vapor interface. ► To calculate the interfacial velocity, an empirical power-law velocity profile was introduced. The proposed model described the liquid film thinning effect by the vapor shear flow reasonably well. A new physical model for estimating the liquid film thickness and condensation heat transfer coefficient in a vertical tube, considering the effects of gravity, liquid viscosity, and vapor flow in the core region, is proposed. In particular, for calculating the velocity profile in the liquid film, the liquid is assumed to be in Couette flow forced by the interfacial velocity at the liquid–vapor interface. The interfacial velocity is calculated using an empirical power-law velocity profile. The film thickness and heat transfer coefficient from the new model are compared with existing experimental data and the original Nusslet condensation theory. The new model describes the liquid film thinning effect due to the vapor shear flow and predicts the condensation heat transfer coefficient from experiments reasonably well.