Buoyancy effects on the mass transfer in absorption with a nonabsorbable gas

This paper describes the vapor side buoyancy effects on the mass transfer in absorption in the presence of a nonabsorbable gas. Experimental results on a diffusion-absorption refrigerator (DAR) indicate that the vapor side buoyancy effects on the mass transfer are significant when the density of the nonabsorbable gas is significantly less than that of the absorbable gas. A rectangular enclosure absorption problem is first solved to demonstrate the buoyancy effects without the presence of a forced flow. Then, mixed convection heat transfer in a circular pipe is simulated in such a way as to be analogous to the mixed convection mass-transfer problem in the DAR absorber. Finally, the vapor side mixed convection absorption between parallel plates is simulated including the effects of the absorbed mass on the mass balance. The Sherwood number dependence on the mass transfer Grashof number and Reynolds number as well as the effects of the suction boundary conditions are discussed. Each of these simulations had individual limitations, but, taken together, they illuminate the major aspects of the absorption physics.