ABSTRAKT

The paper analyses the performance of several low-Reynolds number turbulence models with moderate Prandtl number fluids (10⁰ < Pr < 10¹) for forced and mixed convection cases. The turbulence models tested include well-used variations of the k-ε eddy viscosity model, and Reynolds stress transport models. For forced convection the results show that the turbulence models perform very similarly to each other at a Prandtl number of 0.71, however for increasingly high Prandtl numbers the results show significant spread in performance. This spread is due to the very-near wall predictions of turbulence levels, which become much more influential on the thermal field at higher Prandtl numbers. For mixed convection buoyancy-aided flow the increase in spread is significantly less than for forced convection due to laminarisation of buoyancy aided flow, whereas for buoyancyopposing flow the spread in model performance at higher Prandtl number is similar to that in forced convection, with only a slight decrease in spread with larger buoyancy forces.