Coupled heat and mass transfer during nonisothermal absorption by falling droplet with internal circulation T. Elperin a, * , A. Fominykh a , Z. Orenbakh b a The Pearlstone Center for Aeronautical Engineering Studies, Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel b Negev Academic College of Engineering, 71 Bazel St., P.O. Box 45, Beer Sheva 84100, Israel Received 9 July 2005; received in revised form 7 May 2006; accepted 11 July 2006 Available online 11 September 2006 Abstract We considered mass and heat transfer during nonisothermal absorption of a gas by a falling droplet with internal circulation. Gas phase is assumed to be free of inert admixtures and mass transfer is liquid phase controlled. Mass flux is directed from a gaseous phase to a droplet, and the interfacial shear stress causes a fluid flow inside the droplet. Droplet deformation under the influence of interface shear stress is neglected. Absorbate accumulation and temperature increase in the bulk of liquid phase are taken into account. The problem is solved in the approximations of a thin concentration and temperature boundary layers in the liquid phase. The thermodynamic parameters of the system are assumed constant. The system of transient partial parabolic differential equations of convective diffusion and energy balance with time-dependent boundary conditions is solved by com- bining the similarity transformation method with Duhamel’s theorem, and the solution is obtained in a form of Volterra integral equation of the second kind which is solved numerically. Theoretical results are compared with available experimental data for water vapor absorption by falling droplets of aqueous solution of LiBr. Ó 2006 Elsevier Ltd and IIR. All rights reserved. Keywords: Absorption system; Absorption; Gas; Drops; Heat transfer; Mass transfer; Modelling Transfert de chaleur et de masse lors de l’absorption a ` gouttelettes tombantes, avec circulation interne Mots cle ´s : Syste `me a ` absorption ; Absorption ; Gaz ; Gouttelettes ; Transfert de chaleur ; Transfert de masse ; Mode ´lisation 1. Introduction Spray absorption and spray absorber design and anal- ysis attracted considerable attention in recent years be- cause of higher contact surfaces per unit volume and higher rates of mass transfer in spray absorbers in *Corresponding author. Fax: þ972 8 6472813. E-mail addresses: elperin@bgu.ac.il (T. Elperin), fominykh@ bgu.ac.il (A. Fominykh), zakhar@nace.ac.il (Z. Orenbakh). 0140-7007/$35.00 Ó 2006 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2006.07.006 International Journal of Refrigeration 30 (2007) 274e281 www.elsevier.com/locate/ijrefrig