Thermal stratification affects comfort and air quality in naturally ventilated amphitheater classrooms

We numerically investigate the steady mean turbulent flow and temperature fields developing in a model of an amphitheater classroom affected by stratification, and the associated consequences on thermal comfort, and air quality. The classroom is ventilated through external doors, warmed by the occupants and exchanges heat through the walls. The fluid dynamics is governed mainly by the competition between the momentum of the incoming air and buoyancy due to occupants’ heat fluxes as well as inflow temperature. The inflow velocity is the primary determinant of the indoor conditions: when low occupants’ heat fluxes dominate, the resulting stratification leads to poor air quality and reduced comfort in the upper tiers. Conversely, higher inlet velocity promotes mixing and prevents stratification, thus homogenizing and reducing the Age of Air. Albeit with less intensity, thermal stratification is also observed with low external temperature. Conversely, high external temperatures enhance mixing, improving the overall comfort and air quality. These findings highlight flow structures in a level of detail that complements previous literature and contributes to the understanding of buoyancy-driven ventilation in rooms of large height and complex geometry, such as auditoriums.