Bubble columns are widely used as gas-liquid contactors and as reactors in chemical, petrochemical and biochemical industries. Effective mixing as well as high interfacial area between the phases lead to improved heat and mass transfer characteristics. Gas-liquid flow in bubble column reactors is characterized by a combination of inherently unsteady complex processes with widely varying spatial and temporal scales. Understanding the complexity of the fluid dynamics and heat transfer in bubble column is important due to their application in chemical and bioprocess industries. The potential of Computational Fluid Dynamics (CFD) for describing the hydrodynamics and heat and mass transfer of bubble columns has been established by several publications in the past. CFD predicts what happens quantitatively when fluids flow, often with the complications of simultaneous flow of heat, mass transfer, phase change, chemical reaction, mechanical movement, stresses and displacement of immersed or surrounding solids. This paper reports the heat transfer characteristics of a semi-batch gas (air)-liquid (water) up-flow bubble column by CFD analysis. The Euler-Euler approach has been used for modeling the multiphase flow and to find the time averaged radial profiles of heat transfer coefficient along the column height. The standard k – ? dispersed turbulence model has been used to account for the effect of turbulence. The simulated results have been compared with the experimental results found in literature.

Bubble column reactors are widely used in many industrial applications including chemical, biochemical, petrochemical, environmental and metallurgical processes. The industrial importance of bubble columns is due to the advantages that they offer which include: absence of moving parts, easier maintenance, simple construction, high effective interfacial area, excellent temperature control and high The IUP Journal of Chemical Engineering, Vol. III, No. 2, 40 2011 heat and mass transfer rates caused by strong gas-liquid interactions. Usually bubble columns operate either in a bubbly flow (homogeneous) regime or churnturbulent flow (heterogeneous) regime depending on the phase’s physical properties, operating conditions and the system flow characteristics (Shaikh and Al-Dahhan, 2007). Recently, in many of the commercial installations and industrial applications of bubble columns, the churn-turbulent flow regime has been found to be of considerable and practical interest (Dhotre and Joshi, 2004). In churnturbulent flow regime, high gas is used throughout which yields higher volumetric productivity. This causes increased liquid circulation intensity that affects the dynamics of the bubbles and transport (heat and mass) characteristics. Hence, design and scale-up of bubble columns remain challenging tasks due to the complexity of their non-linear hydrodynamics and phases interactions. In many industrial processes where bubble columns are used, thermal control is of importance because reactions are usually accompanied by heat supply or removal of endothermic or exothermic operations, respectively. Therefore, maintaining a desirable bulk media temperature is necessary which plays an important role in the performance of the reactor.

Gas-liquid bubble column, Hydrodynamics, Heat transfer coefficient, Radial profiles, CFD simulation, Eulerian multiphase model, Chemical Engineering Journal, Cross Linked Pva Membranes, Pervaporation Catalytic Membrane Reactor, Membrane Separation Process, Esterification Reactions, Plant Scale Production, Catalytic Membranes, Kinetic Model Equations, Regression Analysis, Pervaporation Reactors.