LAUSR

Abstract The combined heat and mass transfer problem in the presence of constant mass fraction at the wall occurring in the process of laminar falling film absorption is undertaken in the present work. The energy and absorbate equations are analytically treated by means of integral transforms due to the versatile analytical solving Laplace method and exact series solutions are obtained for temperature and mass fraction fields under the assumptions of both the insulated (adiabatic) and isothermal wall boundary conditions. The effects of constant wall mass fraction versus the impermeable mass flux are then investigated across the film while the absorption evolves in the streamwise direction. Flow length dependent and independent solutions are eventually presented and discussed. The results clearly indicate that the final output through the film absorption process whether accounting for the adiabatic or isothermal wall boundary conditions can be controlled by the imposition of an adequate uniform mass fraction at the wall, which may have significant implications in the design of new generation absorbent tubes or similar apparatuses in medical applications. Supplying a uniform mass fraction at the wall considerably alters the physical absorption phenomenon. Impermeable wall condition is found to be equivalent to diminishing mass fraction at the wall and initial mass fraction at the wall resulted in enhanced cooling when the Stefan number goes to zero. Enhanced absorbed mass flux at the interface and heat transfer at the wall takes place by the prescription of constant mass fraction at the wall.