Brine-water experimental study on the natural ventilation flow rate induced by a localized buoyancy source in an inclined narrow space

Abstract

Natural ventilation is an energy-saving strategy for diluting indoor contaminants. A series of brine-water experiments are conducted to investigate the mechanisms influencing the ventilation flow rate induced by stratified buoyancy-driven flows in inclined narrow spaces, such as tunnels, corridors and pathways. The results indicate that the flow stratification is determined by source location, tunnel inclination and source buoyancy flux. While Bernoulli’s theorem still can be used to estimate the ventilation flow rate, flow stratification and the buoyant layer thickness should be taken into consideration in such an inclined configuration. The flow is divided into three flow regimes in terms of the mechanisms controlling the flow rate q. A dimensionless parameter η is proposed to categorize the flow regimes. When η < 0.5, the air inflow is mainly induced by plume entrainment and q is approximately equal to that in a horizontal tunnel. When 0.5 < η < 2, q is influenced by the stratification and increases with η. When η > 2, the flow is approximately well-mixed and a constant dimensionless ventilation flow rate is obtained. Models are proposed to estimate q in different flow regimes. The study can be a reference for natural ventilation design in such configurations.