Abstract The present study deals with the modeling and simulation of flow through an annular reactor at different hydrodynamic conditions using computational fluid dynamics (CFD) to investigate the flow behavior. CFD modeling was utilized to predict velocity distribution and average velocity in the annular geometry. The results of CFD simulations were compared with the mathematically derived equations and already developed correlations for validation purposes. CFD modeling was found suitable for predicting the flow characteristics in annular geometry under laminar flow conditions. It was observed that CFD also provides local values of the parameters of interest in addition to the average values for the simulated geometry. Keywords Annular reactor, computational fluid dynamics (CFD), hydrodynamics, Rhodamine B I. INTRODUCTION NNULAR reactors have been extensively studied in literature because of advantageous basic features of this geometry. Some of the studies on annular geometry include investigation on role of a Pt/Al 2 O 3 catalyst in the oxidative dehydrogenation of propane [1], kinetics of carbon monoxide oxidation at high temperature [2], partial oxidation of methane [3], treatment of dye manufacturing plant effluent using UV/H 2 O 2 and multi UV lamps [4], photocatalytic degradation of some of VOCs in the gas phase [5], role of gas-phase chemistry in the rich combustion of H 2 and CO over a Rh/Al 2 O 3 catalyst [6], simulation of degradation of perchloroethylene in air [7], influence of fins on photocatalytic removal of formaldehyde [8], photocatalytic degradation of gaseous 1-propanol: kinetic modeling and pathways [9], modeling of annular flow [10] and direct conversion of methane to formaldehyde under high temperature and short residence time [11]. The hydrodynamics of the flow is one of the most important issues in the annular reactors depending upon the kinetics, operating conditions, and geometrical properties of the system. Hence modeling, design and scale-up of these reactors require an accurate prediction of hydrodynamics. The traditional methods of predicting fluid flow in annular reactors depends heavily on theoretical modeling and empirical correlations. These theoretically developed equations are suitable only to specific reactor configurations and not take into account the local effects [12]. Jatinder Kumar 1 & Ajay Bansal 2 are with Department of Chemical Engineering, Dr B R Ambedkar National Institute of Technology,Jalandhar- 144011,India (e-mail: replytojk@yahoo.com 1 , bansal@nitj.ac.in 2 ) A new method to estimate the hydrodynamics is required which should also be able to predict the velocity profiles and concentration fields in the annular reactor for better design and scale-up applications. A very effective approach to tackle this challenge is computational fluid dynamics (CFD). Computational fluid dynamics (CFD) is a well established technique for the analysis of systems involving fluid flow, mass transfer, heat transfer, reaction and associated phenomena. There are several advantages of using CFD such as ability to study hazardous system in a safe environment and reduction in the time and cost of analysis [13]. The recent CFD studies on annular reactors include simulation of a pilot-scale annular bubble column photocatalytic reactor [14], analysis of photocatalytic gas phase vinyl chloride oxidation [15], simulation of trichloroethylene (TCE) oxidation at various pollutant concentrations, flow rates, and reactor lengths [16] and study of annular photoreactor hydrodynamics [17]. More recently, Duran et al. [12] applied CFD to investigate single- phase flow mass transfer prediction in annular reactor for laminar, transitional and turbulent flow condition. It was found that laminar model predicted mass transfer successfully under laminar conditions. For turbulent conditions, AKN (Abe, Kondoh and Nagano) model, and RSM (Reynolds Stress Model) performed well. Santoro et al. [18] studied the oxidation of tributyl phosphate (TBP) and tri(2-chloroethyl) phosphate (TCEP) in parallel and cross-flow annular photoreactor. CFD simulations enabled the spatial visualization of hydrogen peroxide and hydroxyl radical distributions in the reactor. Queffeulou et al. [19] investigated the removal of acetaldehyde in annular photocatalytic reactor with a thin film of TiO 2 coated on stainless steel plate. Modeling of fluid dynamics and reaction was realized with a CFD approach. In terms of conversion yield, model predictions and experimental results were found in good agreement. Vincent et al. [20] studied the hydrodynamics and degradation of acetone in annular reactor. It was observed that CFD modeling estimate the kinetic parameters of the degradation of acetone very close to the experimental results. The aim of the present work was to carry out CFD modeling of the annular geometry to predict the fluid flow of aqueous solution of a dye at various hydrodynamic conditions. The aqueous solution of dye was used to explore the application of annular reactor for dye degradation in future. The results of the CFD model were compared with theoretical modeling for validation of the model. Rhodamine B was used as model dye. It is organic in nature and most important xanthene dye [21]. Jatinder Kumar, Ajay Bansal Study of Flow Behavior of Aqueous Solution of Rhodamine B in Annular Reactor Using Computational Fluid Dynamics A World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering Vol:6, No:4, 2012 252 International Scholarly and Scientific Research & Innovation 6(4) 2012 ISNI:0000000091950263 Open Science Index, Chemical and Molecular Engineering Vol:6, No:4, 2012 publications.waset.org/14072/pdf