chemical engineering research and design 89 (2011) 352–366 Contents lists available at ScienceDirect Chemical Engineering Research and Design journal homepage: www.elsevier.com/locate/cherd A jet mixing study in two phase gas–liquid systems T. Yousefi Amiri a , J.S. Moghaddas a,* , Y. Moghaddas b a Transport Phenomena Research Center, Chemical Engineering Faculty, Sahand University of Technology, P.O. Box 51335/1996, Tabriz, Iran b Islamic Azad University - Ahar Branch, P.O. Box 54516, Ahar, Iran abstract All studies concerned with jet mixing have been focused on liquid phase systems and no studies have been found on jet mixing for gas–liquid two phase systems. In the present study the use of jet fluid as a mixer in gas–liquid systems was proposed. Further by installing an experimental setup, the mixing behavior of liquid phase was studied. Gas flow and jet flow are injected to the mixing vessel countercurrently. In this study, the effect of jet injection, location of the conductivity probe, aeration rate and jet Reynolds number on the mixing time are investigated. The created flow pattern was extracted for each condition and the results often analyzed on the basis of them. It is observed that, for low aeration rates, the injection of jet decreases the mixing time considerably. By increasing the aeration rate, the difference in mixing times between the two cases of jet injection and without jet is reduced. Results also show that the closer the probe is to encounter location of the jet and airflow, the lower the mixing time obtained. Dependence of mixing time on the probe location decreases by increasing the mixing intensity and eliminating dead zones. It is obtained, on the basis of Re j and the amount of jet travelling in the vessel, increasing the aeration rate has different effects on the performance of mixing. Generally, four different trends for the variation of mixing time with increasing the aeration rate are observed. Crown Copyright © 2010 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. Keywords: Mixing time; Gas–liquid systems; Jet flow; Aeration; Flow pattern 1. Introduction In a jet mixer, a high-velocity liquid jet is injected into a vessel, where it entrains some of the surrounding fluid and creates a circulation pattern within the vessel, thus leading to mixing of the contents. The relative velocity between the jet and the bulk liquid creates a turbulent mixing layer at the jet boundary. This mixing layer grows in the direction of the jet flow, entrain- ing and mixing the jet liquid with the bulk liquid (Zughbi and Rakib, 2004; Patwardhan, 2002; Jayanti, 2001). The studies on jet mixing can be classified into two main categories: experimental studies in which the main objectives have been to investigate the effect of operating conditions and geometries such as jet velocity, jet diameter, the angle and location of the jet injection, liquid viscosity, tank dimen- sions and the shape of the tank bottom on the mixing time, and to propose empirical equations for calculating the mixing time as an important criterion in mixing (Fossett and Prosser, ∗ Corresponding author. Tel.: +98 412 3459155; fax: +98 412 3444355. E-mail address: jafar.moghaddas@sut.ac.ir (J.S. Moghaddas). Received 7 November 2009; Received in revised form 14 June 2010; Accepted 15 June 2010 1949; Fossett, 1951; Fox and Gex, 1956; Okita and Oyama, 1963; Hiby and Modigell, 1978; Lane and Rice, 1982; Maruyama et al., 1982; Simon and Fonade, 1993; Grenville and Tilton, 1996, 1997). The other category is the modeling or simulation stud- ies on the basis of CFD techniques, the focus of which has been on investigating the detailed hydrodynamics of jet mix- ing, the homogenization progress and the effect of various parameters on mixing performance (Brooker, 1993; Hoffman, 1996; Ranade, 1996; Jayanti, 2001; Patwardhan, 2002; Zughbi and Rakib, 2004; Rahimi and Parvareh, 2005, 2007). A review of these two categories studies can be found in Wasewar (2006) and Patwardhan (2002). All of the previously conducted studies concerned with jet mixing have been focused on single liquid phase sys- tems and no studies have been found on jet mixing for gas–liquid two phase systems. Considering this fact that the gas–liquid agitated vessels are extensively applied in chemical and related processes such as physical/chemical absorption 0263-8762/$ – see front matter Crown Copyright © 2010 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. doi:10.1016/j.cherd.2010.06.009