Combined heat and mass transfer for laminar flow of moist air in a 3D rectangular duct: CFD simulation and validation with experimental data

Computational fluid dynamics (CFD) simulations are performed for convective heat and mass transfer between water surface and humid air flowing in a horizontal 3D rectangular duct. A hydrodynamically fully developed flow of moist air flows over the surface of a water tray. As the air flows over the water tray, water evaporates from water tray to the air stream. Evaporation cools the water until sensible heat transfer from the air equals the latent heat of evaporation. As the water temperature decreases below the air temperature, a simultaneous heat and mass transfer process with heat and mass transfer in opposite direction occurs. This phenomenon was studied experimentally in a previous work and has already been reported. In the present work, attempt has been done to model the same experiment. Numerical and experimental data are compared and sensitivity studies are carried out to understand the discrepancies between them. Effect of Rayleigh number is found to be negligible. Effect of introducing a heat source/sink at the water surface could result negative Nusselt and Sherwood number. Heat and mass transfer analogy is defined for a combined heat and mass transfer problem.