Pollutant dilution in displacement natural ventilation rooms with inner sources

Indoor air quality and pollutant dispersion in natural ventilation rooms have received considerable attention in recent years. In order to evaluate the pollutant concentration levels in the occupant zone in a displacement natural ventilation (DNV) room, the mathematical model in previous studies are employed and extended to estimate pollutant transportation in a DNV room with the consideration of both the incoming air concentration and indoor pollutant source, resulting in exponential type expressions in time for the concentration in the lower zone and the mean concentration in DNV rooms. The results show that for reducing the concentration in the lower zone to a certain value, the concentration of inflow air and indoor emission rate should be less than their critical values for a given effective opening area of the window. The effect of thermal radiation of the inner surface on the reduction of pollutant concentration in the upper zone is greater than that in the lower zone of a DNV room. In addition, the effective opening area of the window primarily influences the final concentration level in the DNV room, and only affects the decay rate of indoor pollutant concentration when the pollutant concentration of incoming air or the strength of the indoor source approach their critical values.