CFD investigation of indoor airflow and heat removal during night cooling with ceiling and attic ventilation in a residential building

This paper investigates the cooling potential of a perforated ceiling as part of a night-time ventilation technique for residential buildings in tropical climates. 3D steady Reynolds-averaged Navier-Stokes computational fluid dynamics simulations were carried out under non-isothermal conditions (wind and buoyancy-driven ventilation) for an isolated realistic single-story residential building with internal partitions and a pitched roof. Three different building ventilation configurations were assessed, i.e. cross-ventilation through window openings on the windward and leeward walls (C1), configuration C1 but with a perforated ceiling and attic ventilation (C2), single-sided ventilation through the windward window opening combined with a perforated ceiling and attic ventilation (C3). The results show that C2 performs better than C1 and C3, as it allows the most efficient heat removal from the occupied zone, resulting in a reduction of the volume-average mean air temperature within the rooms. Configuration C2 resulted in a 98% higher heat removal effectiveness (HRE) and a 20% higher air exchange rate (ACH) than the reference case (C1). Decreasing the porosity of the perforated ceiling for C2, from φ = 40% to φ = 33%, resulted in a reduction of HRE and ACH of 32% and 7%, respectively. Furthermore, different approach-flow angles (i.e. α = -60°; α = -30°; α = 0°; α = 30°; α = 60°) did not significantly affect HRE and ACH within the unpartitioned side of the building (Room 1 (R1)), while a substantial effect was found for the partitioned side (R2/R3). Overall, C2 outperforms C1 and C3 with respect to heat removal.