Local ventilation effectiveness dependence on the airflow pattern and temperature in the case of isothermal balanced ventilation

Appropriate ventilation may help in the mitigation of airborne transmission of viruses in buildings. Before the COVID-19 pandemic, the ventilation rate was determined depending on the number of occupants, net floor area, and building pollution category. Increasing the ventilation rate, the risk of cross infections may be reduced substantially. Ventilation effectiveness provides information about the airflow capacity to remove the pollutants from the breathing zone of occupants. In the present study, the interrelation between ventilation effectiveness and the air temperature was analysed in the case of different isothermal balanced ventilation strategies. Mixing, displacement, and personalized ventilation were investigated in a test room, measuring the CO(2) concentration, and having the air exhaust positions above the floor and under the ceiling. The air temperatures were set between 21 °C and 26 °C. To illustrate the airflow patterns numerical simulations have been carried out. It was shown that there are significant differences between ventilation effectiveness depending on the air temperature and ventilation strategy. In most cases, the ventilation effectiveness was higher when the air exhaust was positioned under the ceiling. For investigated air temperatures, differences of even 20%–40% have been determined between ventilation effectiveness values in the case of a certain ventilation strategy.