Accurate Numerical Simulation of Turbulent Natural Convection for Fatigue Analysis of Heat Exchanger High Temperature Difference Region

Buoyancy-driven flow in high temperature difference region has attracted more and more attention due to its application in nuclear industry, such as fatigue analysis. A high-precision Non-Boussinesq model is developed to simulate turbulent natural convection by adding source terms through User Defined Functions (UDF) in Fluent software. The analyses of velocity and temperature profile in an air-filled-rectangular cavity are conducted for the validation of this developed model. A correlation between average Nusselt number and Rayleigh number for the large aspect ratio cavity is obtained to predict heat transfer characteristic. Finally, application of Non-Boussinesq model to a high temperature difference region of heat exchanger is investigated. The results reveal that scale effect is important for the heat transfer of natural convection, and the decrease of scale will lead to an increase of heat transfer coefficient.