Heat transfer induced by mixed convection flows through a horizontal opening in a full-scale two-story test-hut

Abstract

This paper undertakes a study to investigate the heat transfer through a horizontal opening connecting two rooms of a full-scale two-storey full-scale test-hut with two ventilation strategies, single ventilation with downward net flow through the opening and independent ventilation in each room. The horizontal opening represents a stairwell opening in buildings. The airflow in the test-hut is characterized by 1.4×105 ≤ Gr ≤ 7.7×106 and Re ≤ 2,060. Based on 74 cases simulated using a CFD model extensively validated by Vera et al. (2010), all heat fluxes through the opening are calculated for each case under study. The collection of results demonstrates that upward heat fluxes through the opening are proportional to the temperature difference between the lower and the upper rooms. Heat fluxes were even found when the upper room is warmer than the lower room due to local non-uniformities of air under and above the opening. Also, it was found that the heat transfer through the opening is mainly caused by buoyancy driven flows with significant contribution from forced flows. This means that mixed convective heat transfer occurs through the opening and the combined effect can be predicted by the correlation Nu⁄〖Re〗^(1/2) =36,86(Gr⁄〖Re〗^2 )^0.08.