ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Transport phenomena in an agitated vessel with an eccentrically located impeller

Magdalena Cudak, Joanna Karcz, and Anna Kiełbus-Rąpała

Department of Chemical Engineering, West Pomeranian University of Technology, Szczecin, al. Piastów 42, PL-71 065 Szczecin, Poland

E-mail: Joanna.Karcz@zut.edu.pl

Abstract: The paper presents results of an experimental analysis of the transport phenomena at the vicinity of the wall of an unbaffled agitated vessel with an eccentrically located impeller. Distributions of the transport coefficients were experimentally studied using an electrochemical method within the turbulent regime of the Newtonian liquid flow. Measurements were carried out in an agitated vessel with the inner diameter T = 0.3 m. Liquid height in the vessel was equal to the inner diameter, H = T. The agitated vessel was equipped with a Rushton or a Smith turbine or an A 315 impeller. Eccentricity of the impeller shaft was varied from 0 to 0.53. Local values of the dimensionless shear rate, shear stress, dynamic velocity and friction coefficient were integrated numerically for the whole surface area of the cylindrical wall of the vessel. Averaged values of these quantities were correlated with the impeller eccentricity and modified Reynolds number. The proposed Eqs. (5)–(8), with the coefficients given in Table 2, have no equivalent in open literature concerning this subject. Distributions of the shear rate, γ/n, and friction coefficient, f, at the vicinity of the cylindrical wall of the unbaffled vessel equipped with eccentric Rushton or Smith turbine or A 315 impeller are very uneven and they depend significantly on the impeller eccentricity, e/R. Maximum local values of these variables are located on the wall section closest to the impeller blades. From among the tested impellers, the greatest effects of the impeller eccentricity, e/R, and the liquid turbulence (described by the modified Reynolds number Re _P,M) on the averaged dimensionless shear rate (γ/n)_m and friction coefficient, f _m, are found for the radial-flow Rushton turbine located eccentrically in an unbaffled agitated vessel.

Keywords: transport phenomena – agitated vessel – eccentrically located impeller – shear rate – friction coefficient

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-010-0086-7

Chemical Papers 65 (2) 146–155 (2011)