Numerical simulation of condensation from isobutane vapour – air mixture

Abstract

Hydrocarbon condensation has been a topic of interest in recent years due to its applications in refrigeration, chemical processing and air conditioning. The condensation of friendly fluids reduces the Global Warming Potential and Ozone Depletion Potential, which can be used as an alternative to many hydrofluorocarbon (HFC) refrigerants. The main objective of this study is to investigate the combined heat and mass transfer of laminar film condensation from isobutane vapour in the presence of a small percentage of non-condensable gas (air) inside a vertical tube. The external tube wall is subjected to a constant temperature. To achieve our goal, a mathematical model based on mass conservation, momentum, and energy in both gas and liquid phases is established. The discretization of equations in each region with the boundary conditions is realised using an implicit finite difference scheme. The validity of the numerical model developed is verified in comparison with the results of the literature. The obtained results show that the condensation process is enhanced by increasing the inlet velocity and the inlet-to-wall temperature difference. Moreover, the results indicate that the presence of non-condensable gas reduces the efficiency of heat and mass exchanges.