Modeling Coupled Heat and Mass Transfer in Laminar Forced Convection in a Vertical Channel: Influence of the Fluid's Relative Humidity

The heat and mass exchanges between fluids and walls that accompany two-phase flows in channels are of immeasurable interest in many fields such as energy, food processing, fire engineering, biomedical etc. The aim of the present study is to explore numerically the effect of the relative humidity of an upward laminar forced convection airflow in a channel on heat and mass transfer. The walls of the channel are damp and interact with the outside environment. Based on simplifying assumptions, the flow, whose thermo-physical properties depend on temperature and relative humidity, was modeled by the Navier Stokes equations and the flow conservation equation. The finite volume method was used to discretize the equations, and the resulting systems of algebraic equations were solved using the Thomas and Gauss algorithms. A numerical calculation code written in FORTRAN and validated by comparing our numerical results with those in the literature was used to run the simulations. These numerical simulations, carried out with a relative humidity range of 60 to 90%, a Reynolds number of 500 and a fluid temperature of 323.15K for an ambient temperature of 298.15K, enabled a detailed study of the heat and mass exchanges taking place between fluid and wall. A sensitivity study of the numerical results to the mesh was carried out to demonstrate the stability of the mesh. The numerical results obtained, presented in the form of axial and radial profiles of temperature, mass concentration, Nusselt and Sherwood numbers, reveal the important role of relative fluid humidity in heat and mass transfer in a vertical channel. The heat and mass transfer rates obtained at the leading edge of the channel and at the outlet are different. Keywords: Heat and mass transfer, relative humidity, Nusselt and Sherwood numbers, vertical channel.