CFD Simulation of Turbulent Heat Transfer in an Agitated Vessel

Abstract

Blending and mixing is an important unit operation in process industries. It has broad spectrum of applications ranging from concrete mixing to polymer processing including cosmetics, paints, food stuff, etc. The quality of final product is depends upon the degree of mixing, hence, it is the important area for research and industrial development. The present work is aiming to explore flow and heat transfer characteristics in an agitated vessel in the turbulent flow regime using CFD simulation. ANSYS Fluent is used as a solver to simulate flow and heat transfer in agitated vessel. A pitched blade turbine with six blades at 45o has been used for the study. The turbine placed concentrically in a cylindrical vessel with flat top and bottom. The cylindrical vessel is subjected to uniform constant wall temperature(jacketed vessel). The Reynolds number of 7.2×104 has been chosen for present study. For heat transfer study six values of Prandtl number have been taken as 0.71,7,20,30,40 and 50. The flow dynamics shows that the velocity near the turbine is very high as compare to vessel surfaces in the horizontal plane and in the vertical plane it is maximum below the turbine. The pressure was found minimum near the impeller and maximum at cylindrical walls. The heat transfer simulation shows that the temperature gradient is small and this gradient further reduces with increasing the Prandtl number and the almost uniform temperature profile obtained at Prandtl number 50 at Reynolds number =7.2×104. Overall, the present study shows that the degree of thermal mixing increases with increasing Prandtl number. The overall heat transfer also increases with increasing Prandtl number and it shows functional dependency on Prandtl number.