Relative ventilation effectiveness in a mechanically ventilated airspace under isothermal conditions

The relative ventilation effectiveness for airborne dust was evaluated in a mechanically ventilated airspace under isothermal flow conditions. Three supply air inlets, specifically, one-way ceiling, two-way ceiling, and sidewall, were compared at ventilation rates of 0.1, 0.5, 0.7, and 1.0 m³/s. The dust concentrations were measured with inhalable dust samplers, from which the relative ventilation effectiveness at various locations, the overall relative ventilation effectiveness for the airspace, and the spatial variability in dust concentrations were obtained. Results showed that the dust concentration and the relative ventilation effectiveness varied with location and for the three air inlets. The one-way ceiling air inlet, in which the supply air jet was directed away from the exhaust fan, was the best in removing the dust from the locations considered. It had the highest overall relative ventilation effectiveness (E_o = 1.34), although it also had the highest spatial variability in dust concentration (CV = 0.48). The sidewall air inlet, on the other hand, had the most uniform dust concentration (CV = 0.38); however, it had the lowest relative ventilation effectiveness (E_o = 0.67). Additional research should consider other types of air inlets and nonisothermal conditions.