USING NUMERICAL-SIMULATION TO PREDICT VENTILATION EFFICIENCY IN A MODEL ROOM

A computational fluid dynamics (CFD) code is used to simulate the air currents and the contaminant decay inside a small scale model room wit h forced ventilation through a simple supply and return. The numerical results are validated with flow visualization experiments and local c learance rate measurements by laser extinction. The comparisons show e xcellent agreement on the inlet side of the room and fair agreement on the outlet side. Based on the concept of local exponential tracer dec ay and mixing factor (m), an arithmetic average of m is proposed as a measure of overall air ventilation efficiency eta(m). The proposed def inition has practical benefit in numerical simulation because it reduc es computational time without sacrificing the concept of air ventilati on effectiveness. Examples of application are demonstrated by evaluati ng eta(m) for different room configurations and ventilation arrangemen ts. The calculated eta(m) correlate well with the time required for ev acuating the contaminants in different room configurations. The result s show that, for the room geometry studied, a ventilation system perfo rms better when the inlet and the outlet are perpendicular to each oth er than when they are parallel to each other, and that partitions in t he room can have a significant influence on ventilation performance. ( C) 1998 Elsevier Science S.A. All rights reserved.