NUMERICAL SIMULATION OF THE GAS FLOW AND MASS TRANSFER BETWEEN TWO COAXIALLY ROTATING DISKS P. Sandilya, G. Biswas, D. P. Rao, and A. Sharma Indian Institute of Technology, Kanpur^208 016, India This paper deals with the study of the effect of rotation on the gas-side controlled mass transfer between two rotating disks. The velocity and concentration distribution in the gap between the disks have been determined from the solutions of the parabolized Navier–Stokes and species concentrat ion equations. A satisfactory match between the numerical values of mass transfer coefcient with their experiment al counterpart support s the efcacy of the numerical model to predict the mass transfer performance of the cen- trifugal contractor. INTRODUCTION Rotating packed bed (RPB) was introduced to carry out absorption as a measure of process intensi¢cation in the late 1970s [1]. Extensive studies have been carried out on the liquid side £ow and mass transfer behavior in such a device. A comprehensive review of these investigations has been presented by Kelleher and Fair [2]. Experimental data on the overall gas-side mass transfer coef¢cient recently have been reported by Kelleher and Fair [2] and Liu et al. [3]. The studies on gas-side £ow and mass transfer behavior have so far remained con¢ned to macro- scopic analysis involving development of empirical correlations for the pressure drop and mass transfer coef¢cient. However, a fundamental understanding about the transport processes can be gained through a knowledge of the local mass transfer behavior. With this motivation, the laminar inward £ow of a gas between two rotating disks has been studied using the solution of the parabolized Navier^Stokes and species concentration equations. The £ow between stationary disks and rotating disks have been extensively well documented [4]. The preliminary analysis of the £ow between two parallel disks was based on the assumption of creeping £ow. Livesey [5] incorporated the inertia effects on the steady £ow of a viscous incompressible £uid between two in¢nite parallel plates. He presented an approximate solution by assuming parabolic velocity dis- tribution throughout the radial span. Moller [6] reported experimental and theor- etical results for the radial £ow between parallel disks considering both laminar and turbulent £ow. In his analytical derivation for the velocity distribution, he Numerical Heat Transfer, Part A, 39:285^305, 2001 Copyright # 2001 Taylor & Francis 1040-7782/01 $12.00 + .00 285 Received 21 January 2000; accepted 25 September 2000. Address correspondence to Professor G. Biswas, Department of Mechanical Engineering, Indian Institute of Technology, Kanpur^208 016, India. E-mail: gtm@iitk.ac.in