Numerical analysis on the relationship between rate of outdoor air supply and total air age

Air age is an important parameter to assess indoor air quality in ventilated rooms. In order to consider the contribution of ductwork and recirculation, the concept of total air age was proposed for ventilation systems with ductwork and recirculation in previous study. In this paper, about 16 typical cases are simulated with computational fluid dynamics after introducing the method to calculate total air age for ventilation systems with only one AHU and one room in which several inlets and outlets exist. The total air age in the breathing zone is compared for 4 kinds of flow pattern and 4 kinds of mixing ratio between fresh air and return air with the same amount of supply air. It is shown that the total air age in breathing zone is very different even if with the same amount of outdoor air supply.