Comparison of volume flow rate and volume-averaged local mean age of air for evaluating ventilation performance in natural ventilation

Evaluating the ventilation performance is an important part of natural ventilation studies. We considered the volume flow rate, which is used by many researchers, and the volume-averaged Local mean age of air (LMA) as the ventilation performance parameters to evaluate the performance of natural ventilation. Computational fluid dynamics (CFD) simulations were performed on an isolated building model of cross ventilation that contained two openings on the windward and leeward wall and single-sided ventilation model that consisted of a single opening. Parametric studies were performed to evaluate the ventilation performance of eight different building configurations in cross ventilation and single-sided ventilation. Using the volume flow rate it was difficult to evaluate the ventilation performance when the inlet and outlet were very close in cross ventilation and, in single-sided ventilation, it was difficult to evaluate when the airflow speed was fast near the opening but did not penetrate inside the building. While the volume-averaged LMA was an adequate parameter for representing the ventilation performance of the building, the LMA field was a more accurate representation of the local ventilation performance inside the building than the velocity vector field.