Int. J. Therm. Sci. (2000) 39, 753–761  2000 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S1290-0729(00)00277-5/FLA Effect of an absorbate concentration level on the coupled mass and heat transfer during short gas plugs dissolution Tov Elperin *, Andrew Fominykh Pearlstone Center for Aeronautical Engineering Studies, Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel (Received 14 June 1999, accepted 26 January 2000) Abstract — We studied gas absorption from a rising gas plug when the concentration level of the absorbate in the absorbent is finite (finite dilution of absorbate approximation). It is shown that in the case of the finite dilution the lateral convective term in the equation of convective mass transfer in the absorbate must be taken into account. It is found that the mass transfer rate increases with the increase of the absorbate concentration level. Isothermal and nonisothermal absorptions are considered whereby the latter is described by the coupled equations of mass and heat transfer. It is found that the mass transfer rate decreases when the dimensionless heat of absorption increases.  2000 Éditions scientifiques et médicales Elsevier SAS nonisothermal absorption / mass and heat transfer / rising gas plug / finite dilution of absorbate in the absorbent Nomenclature a thermal diffusivity of a liquid ...... m 2 ·s −1 b coefficient in equation (37) c molar density .............. mol·m −3 c A absorbate concentration ......... mol·m −3 c p specific heat ............... kJ·kg −1 ·K −1 D molecular diffusion coefficient ..... m 2 ·s −1 d coefficient in equation (37) ....... K −1 d ch channel diameter ............. m g acceleration of gravity .......... m·s −2 K = c p /(dL), dimensionless number L heat of absorption ............ kJ·kg −1 L B length of a gas plug ........... m Le = D/a, Lewis number N A r mass flux density of component A in radial direction .............. kg·m −2 ·s −1 N A z mass flux density of component A in axial direction ................. kg·m −2 ·s −1 Pe = U ∞ d ch D −1 , Peclet number for a gas plug Pe ∗ = 8/3(Re Pr), Peclet number for a falling liquid film * Correspondence and reprints. elperin@menix.bgu.ac.il Pr = ν/a, Prandtl number Q c mass flux ................. kg·s −1 Q c 0 mass flux in the approximation of the infinite dilution .............. kg·s −1 Q is c 0 mass flux for isothermal absorption in the approximation of the infinite dilution .. kg·s −1 Q T heat flux .................. kJ·s −1 Q T 0 heat flux in the approximation of infinite dilution .................. kJ·s −1 Re = 8u s δ/(3ν), Reynolds number for liquid film r radial coordinate .............. m R channel radius ............... m R i ratio between terms in equation (13) Sh Sherwood number Sh 0 Sherwood number under the assumption of the infinite dilution s length of an arc measured from a gas plug’s nose .................... m X = (x A − x A 0 )/(x A s − x A 0 ), dimensionless weight fraction of the absorbate x A weight fraction of the absorbate x A s weight fraction of the absorbate at the gas–liquid interface x A 0 weight fraction of the absorbate at the inlet 753