Binary diffusion and heat transfer in mixed convection pipe flows with film evaporation

Abstract

A detailed numerical study has been performed to investigate the heat and mass transfer characteristics in laminar mixed convection pipe flows with film evaporation. Both the thermal conditions of constant wall temperature and uniform heat flux are considered. Results for interfacial Nusselt and Sherwood numbers are presented for air-water and air-ethanol systems for various conditions. Predicted results show that heat transfer along the gas-liquid interface is dominated by the transport of latent heat in association with the vaporization of the liquid film. Additionally, the predicted results obtained by including transport in the liquid film are contrasted with those where liquid film transport is neglected, showing that the assumption of an extremely thin film made in Lin et al. ( J. Heat Transfer 110, 337–344 (1988)) is only valid for systems with low liquid film Reynolds numbers. But for systems having a high liquid film Reynolds number Re 1, the assumption of an extremely thin film is seriously in error.