New scales for assessing ventilation performance.

Several new scales have been developed to quantify fresh air diffusion and contaminant dispersion in ventilated spaces. The local purging effectiveness is proposed for analyzing the individual contribution of each supply opening for a multi-inlet system. The local specific contaminant-accumulating index is defined to indicate the tolerance of a ventilation flow to contaminants. Furthermore, the regional purging flow rate, Up, is re-embodied in a simple expression different from the previous description. Two Up related parameters applicable for characterizing ventilation flows, i.e., the equivalent regional Peclet number and the back-mixing index, are also described. These new scales and their application are discussed and demonstrated by means of numerical simulations. The present new scales appear to be promising for designing, diagnosing and optimizing ventilation systems.