Journal of Mechanical Science and Technology 22 (2008) 1821~1829 www.springerlink.com/content/1738-494x DOI 10.1007/s12206-008-0614-3 Journal of Mechanical Science and Technology Investigation on hydrodynamics and mass transfer characteristics of a gas-liquid ejector using three-dimensional CFD modeling Tony Utomo 1 , Zhenhua Jin 1 , MSq Rahman 1 , Hyomin Jeong 2 and Hanshik Chung 2,* 1 Graduate School of Department of Mechanical and Precision Engineering, Gyeongsang National University, 445 Inpyeong-Dong, Tongyeong, Gyeongsangnamdo 650-160, Korea 2 Department of Mechanical and Precision Engineering, Gyeongsang National University, 445 Inpyeong-Dong, Tongyeong, Gyeong- sangnamdo 650-160, Korea (Manuscript Received August 21, 2007; Revised June 9, 2008; Accepted June 18, 2008) -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract An investigation of the gas-liquid ejector has been carried out to study the influence of operating conditions and ejec- tor geometries on the hydrodynamics and mass transfer characteristics of the ejector by using three-dimensional CFD modeling. The CFD results were validated with experimental data. Flow field analysis and prediction of ejector per- formance were also conducted. Variations of the operating conditions were made by changing the gas-liquid flow rates ratio in the range of 0.2 to 1.2. The length to diameter ratio of mixing tube (L M /D M ) was also varied from 4 to 10. CFD studies show that at L M /D M =5.5, the volumetric mass transfer coefficient increases with respect to gas flow rate. Meanwhile, at L M /D M =4, the plot of volumetric mass transfer coefficient to gas-liquid flow rate ratio reaches the maxi- mum at gas-liquid flow rate ratio of 0.6. This study also shows that volumetric mass transfer coefficient decreases with the increase of mixing tube length. Keywords: Hydrodynamics; Mass transfer; Ejector; CFD; Gas-liquid -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction In the field of chemical and biochemical reaction engineering, there has been increasing interest in jet loop reactors during the last decade because of their high efficiency in gas dispersion resulting in high mass transfer rate. Jet loop reactors are also used in hydrogenation and chlorination in the chemical proc- ess industry. Many other examples concerning the use of jet loop reactor can also be found, e.g., in the pa- pers of Daucher [1], Zahradnik and Rylek [2], Cram- ers et al. [3,4], Gracia Salas and Cotera-Flores [5], Kim and Choi [6], and Jeong et al. [7]. The principle of this reactor type is the utilization of the kinetic energy of a high velocity liquid jet to entrain the gas phase and to create a fine dispersion of the two phases. Mixing and process equipment are the essential units of any chemical industry that utilize this type of reactor. Due to their favorable mass trans- fer and mixing characteristics, ejectors are being in- creasingly used as gas-liquid contactor in these proc- esses. A standard ejector, shown schematically in Fig. 1, consists of a nozzle, suction chamber, mixing tube, diffuser and draft tube. The primary fluid, typically liquid, is pumped into the system at high velocity through a nozzle. According to Bernoulli’s principle, a low-pressure region is created in the suction cham- ber, into which the secondary fluid gets drawn. Typi- cally this secondary fluid is in the gas phase. The gas and liquid phases are mixed and a gas-liquid disper- sion is created in the mixing tube. The pressure is recovered in the diffuser at the exit of the mixing tube. When the secondary fluid is sucked into the suction chamber, the gas and liquid flows are initially coaxial, consisting of an annular secondary fluid flow and a primary fluid jet. This jet flow persists for a certain * Corresponding author. Tel.: +82 55 640 3184, Fax.: +82 55 640 3188 E-mail address: hschung@nongae.gsnu.ac.kr © KSME & Springer 2008