Heat and Mass Transfer of Laminar Free Convection Film Condensation of Vapor–Gas Mixture

Abstract

AbstractThe theoretical equations on heat and mass transfer are set up for laminar free Convection film condensation of vapor–gas mixture. In the theoretical equations only dimensionless wall temperature gradient and condensate mass flow rate parameter are no-given variables respectively for prediction of heat and mass transfer rates. The laminar free Convection film condensation of water vapor in presence of air on a vertical flat plate is taken as example for the numerical solutions on condensate heat and mass transfer, including those on the dimensionless temperature gradient and mass flow rate parameter. Both by decreasing the bulk vapor mass fraction and the reference wall subcooled grade, the wall dimensionless temperature gradient will increase at accelerative pace. Both decreasing the bulk vapor mass fraction and the reference wall subcooled grade will cause decreasing the condensate mass flow rate parameter at accelerative pace. These phenomena demonstrate the decisive effect of the non-condensable gas on condensate heat and mass transfer of the laminar forced film condensation of vapor–gas mixture. The system of the rigorous key solutions on the wall dimensionless temperature gradient and the condensate mass flow rate parameter is formulated to the simple and reliable equations for the laminar free Convection film condensation of water vapor–air mixture. Coupled with these formulated equations, the theoretical equations on the condensate heat and mass transfer can be respectively used for reliable and simple prediction of heat and mass transfer rate on laminar free Convection film condensation of water vapor–air mixture. Additionally, it is found that the condensate heat transfer rate is dominated by the wall subcooled temperature\(t_\text{w}-t_{\text{s},\,\text{int}}\) and the wall temperature gradient, the condensate mass flow rate is dominated by the condensate mass flow rate parameter, and the condensate heat transfer rate is identical to the condensate mass flow rate. Due to the quite different condensate mechanisms, the condensate heat and mass transfer rate of the laminar free Convection film condensation from vapor in presence of non-condensable gas is quite different from that of pure vapor, even for \(C_{\text{mv},\infty } \rightarrow 0.\) KeywordsHeat Transfer RateFilm CondensationCondensate Heat TransferCondensate MassPure VaporThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.