Testing turbulence models to predict interzonal mass airflows through a stairwell opening for both natural and mixed convection flows in buildings

Abstract

The main objective in building design is to balance energy efficiency with healthy, comfortable and productive indoor environments for the occupants. Interior building openings, such as stairwells, are significant paths for the exchange of heat, air, moisture and pollutants. The interzonal airflow through horizontal openings has not been profoundly studied because of its highly transient and unstable nature, the complexity of carrying out experiments and the limited availability of experimental data. Computational Fluid Dynamics (CFD) is an excellent tool to advance the understanding of this phenomenon. In this paper, CFD is applied to evaluate the performance of five two-eddy viscosity turbulence models (k-ε standard, k-ε RNG, k-ε realizable, k-ω standard and k-ω SST) to predict indoor air conditions and upward mass airflows through a horizontal opening in a full-scale, two-story test hut. This study involves six cases with different temperature gradients between the two floors and with three ventilation strategies that represent natural or mixed convection. The main results show that the temperatures are well predicted by all turbulence models while the simulated air speeds present larger variations among the evaluated turbulence models. Overall, the k-s standard and k-s realizable models are the most accurate ones to predict indoor temperatures and air speeds for natural and mixed convection, respectively. Moreover, the upward mass airflows through the horizontal opening estimated by both turbulence models are in very good agreement with the experimental data.