Turbulent Natural Convection Heat Transfer in a Square Enclosure: Turbulence Model Comparisons

A CFD study using four engineering turbulence models has been performed to evaluate the convective heat transfer predictions for an air-filled square enclosure with a Rayleigh number of 1.58 × 10⁹. The four turbulence models considered are, as implemented by FLUENT: a k-ε model, an RNG k-ε model, a “realizable” k-ε model, and a k-ω model. All of the turbulence models investigated employ the Boussinesq approximation to evaluate the unknown turbulent viscosity and use the ideal gas equation of state to evaluate the density in the body force term. The performance of all models was similar. Predicted Nusselt number distributions on the hot and cold walls were overpredicted when compared to experimental data. The predicted average Nusselt numbers were nearly 20% higher on the active walls, and 10% higher on the passive, horizontal walls.