CFD simulation of heat transfer in an agitated vessel with a pitched six-blade turbine impeller

Abstract

In this work, heat transfer to a Newtonian fluid in a jacketed vessel equipped with a pitched blade turbine (PBT) has been numerically investigated. The turbine has six blades at a 45 angle and it is placed in a cylindrically baffled vessel with a flat top and bottom. The cylindrical walls and bottom of the vessel are maintained at constant heat flux q = 3000 W/m^2 boundary condition. Numerical simulations of heat transfer in the agitated vessel for different rotational speeds from 300 to 900 rpm were performed. Heat transfer coefficients at the bottom and vertical walls with off-bottom clearance h/d =1, 2/3, 1/3 (impeller distance from the bottom of the agitated vessel) were evaluated. To study the flow field and transient heat transfer in the agitated vessel, a commercial software ANSYS Fluent 15.0 has been employed. The sliding mesh technique available in ANSYS Fluent was used to model flow around the rotating impeller. k- based Shear-Stress-Transport (SST) turbulence model was chosen to model turbulence. An internal source (sink) of heat was used to eliminate the increase of fluid temperature, which might influence the evaluation of the heat transfer coefficients. By performing the transient simulations, the Nusselt numbers at the bottom, wall and bottom + wall were evaluated, and the heat transfer correlation was developed and compared with experimental data in the existing literature.

In this work, heat transfer to a Newtonian fluid in a jacketed vessel equipped with a pitched blade turbine (PBT) has been numerically investigated. The turbine has six blades at a 45⁰ angle and it is placed in a cylindrically baffled vessel with a flat top and bottom. The cylindrical walls and bottom of the vessel are maintained at constant heat flux q = 3000 W/m^2 boundary condition. Numerical simulations of heat transfer in the agitated vessel for different rotational speeds from 300 to 900 rpm were performed. Heat transfer coefficients at the bottom and vertical walls with off-bottom clearance h/d =1, 2/3, 1/3 (impeller distance from the bottom of the agitated vessel) were evaluated. To study the flow field and transient heat transfer in the agitated vessel, a commercial software ANSYS Fluent 15.0 has been employed. The sliding mesh technique available in ANSYS Fluent was used to model flow around the rotating impeller. k-⍵ based Shear-Stress-Transport (SST) turbulence model was chosen to model turbulence. An internal source (sink) of heat was used to eliminate the increase of fluid temperature, which might influence the evaluation of the heat transfer coefficients. By performing the transient simulations, the Nusselt numbers at the bottom, wall and bottom + wall were evaluated, and the heat transfer correlation was developed and compared with experimental data in the existing literature.