Numerical Study on Condensation Heat and Mass Transfer of Refrigerants on a Vertical Channel in Presence of a Non-Condensable Gas

摘要

The purpose of this study is to analyse the combined heat and the mass transfer of liquid film condensation of vapour-gas mixtures (refrigerants R113 and R134a) in the presence of non-condensable gas (air) inside a vertical channel. Both liquid and gas mixtures are approached by two coupled laminar boundary layer. An implicit finite difference method is employed to solve the coupled governing equations for liquid film and gas flow together with the interfacial matching conditions. The effects of a wide range of changes of two independent variables (inlet Reynolds number and the inlet-to-wall temperature difference) on the local Nusselt number, accumulated condensate rate and dimensionless mass fraction at an exit channel are carefully examined. The numerical results indicate that the condensation of refrigerant R113 is important in comparison with the refrigerant R134a at higher difference temperature and lower speed of vapour-air, and the presence of non-condensable gas was found to have a weak effect on the refrigerant Rl 13 relative to R134a.