Mixed convective heat transfer through a horizontal opening in a ull-scale, two-story test-hut

Abstract

This paper undertakes a study to investigate the heat transfer through a horizontal opening connecting two rooms in a full-scale two-story test-hut with two ventilation strategies, namely ventilation with downward net flow through the opening and independent balanced ventilation in each room. The horizontal opening represents a stairwell opening in buildings. The airflow in the test-hut is characterized by 1.44 × 105 ≤ Gr ≤ 7.66 × 106 and Re ≤ 2782. Based on the simulation of 74 cases using a CFD model, 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 the presence of local eddies under and above the opening. It was also found that the heat transfer through the opening is caused mainly by buoyancy driven flows with some contribution from forced flows. This means that mixed convective heat transfer occurs through the opening and the combined effect can be predicted by the empirical correlation of power-law form Nu = 3.11Gr0.057Re0.63.