Effects of inlet and exhaust locations and emitted gas density on indoor air contaminant concentrations

The steady-state distribution of contaminant concentrations in a workroom is a function of several factors, of which the types and relative position of air inlets and exhausts are some of the most important. Here several different inlet and exhaust locations and types (with or without diffuser) were investigated to determine the optimum inlet and exhaust positions. Room concentration patterns for a workroom were explored by computational fluid dynamics (CFD) simulations for various inlet locations, exhaust locations, contaminant gas densities, and dilution air flow rates. Average contaminant concentrations were calculated for the entire room, the breathing zone plane, and the near-source breathing zone (BZ). The computational results were validated with experimental results. For wall jet inlets and for lighter than air, the exhausts located near the ceiling resulted in lower concentrations than the corresponding exhausts near the floor. Also, the exhausts located on the same wall as the inlet were relatively better than that of the opposite side wall. The relative density of the contaminant was found to have some effects on the concentration distribution at low flow rates, whereas this effect was negligible at higher flow rates (8 ACH or higher). Exhaust location was not important for ceiling inlets as the room was well mixed. Although ceiling inlet type had almost no effect on average concentration, near-source concentrations were markedly less for the ceiling jet inlet than for the ceiling diffuser inlet.