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

Mixing time of a non-Newtonian liquid in an unbaffled agitated vessel with an eccentric propeller

Jolanta Szoplik and Joanna Karcz

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

E-mail: joanka@ps.pl

Received: 31 March 2007  Revised: 20 July 2007  Accepted: 13 August 2007

Abstract: Experimental study of mixing time of non-Newtonian shear-thinning fluids within the transitional regime (3 × 10² < Re < 3 × 10³) of liquid flow is presented. The purpose of this study was to analyze the effect of eccentricity and pumping mode of the impeller as well as of position of the tracer dosage point into the agitated liquid on mixing time. The measurements were conducted in an unbaffled agitated vessel with inner diameter D = 0.7 m equipped with an up-or down-pumping propeller located centrically (e/R = 0) or eccentrically (e/R ≠ 0) in the vessel. Experiments were carried out by means of computer-aided unsteady-state thermal method for three positions of the tracer dosage point. The experimental data show that eccentric position of the propeller in an unbaffled vessel causes a decrease of the mixing time compared to that obtained in a vessel with a centrically located propeller. Mixing time depends also on the pumping mode of the propeller as well as on the position of the tracer dosage point.

Keywords: mixing time - agitation - agitated vessel - non-Newtonian liquid - eccentric propeller - pumping mode

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-007-0081-9

Chemical Papers 62 (1) 70–77 (2008)