HEAT TRANSFER IN JACKETED VESSEL EQUIPPED WITH DOWN-PUMPING PITCHED BLADE TURBINE

Abstract

Heat transfer to a Newtonian fluid in a jacketed vessel equipped with a down-pumping pitched blade turbine (PBT) has been numerically investigated. The turbine has six blades at 45° angles and the turbine is placed concentrically in a cylindrical vessel with a flat top and bottom. An incompressible Newtonian fluid of constant density and viscosity has been considered. The cylindrical wall of the vessel is maintained at constant wall temperature with the help of an outer jacket. The governing momentum and energy equations were numerically solved to obtain the flow and heat transfer fields. The detailed flow and heat transfer fields have been explored for Reynolds number, Re = 7.2 × 104, and Prandtl number in the range 0.71 ≤ Pr ≤ 50. The obtained flow and heat transfer fields are presented as velocity contours, pressure contours, and isotherm profiles at various sections. It is observed that the velocity gradient is higher in the vicinity of the turbine as compared to the vessel wall. In the vertical plane, the velocity is found to be maximum just below the turbine because of the down-pumping of the fluid. The observation of isotherm profiles shows that the temperature gradient is very large near to the vessel wall and small in the vicinity of the turbine. An almost uniform temperature profile was obtained at the highest Prandtl number of 50. The degree of thermal mixing and heat transfer coefficient increases with increasing value of Prandtl number. The area-weighted average value of the Nusselt number shows positive dependence on the Prandtl number. A functional relationship within the average Nusselt number and Prandtl number has been proposed for the present configuration and the operating conditions.