Experimental study on contamination of building exhaust emissions in urban environment under changes of stack locations and atmospheric stability

摘要

Contamination on exhaust emissions from short stacks on a building is the major concern in the urban environment. Dispersion of exhaust emissions around the building was investigated experimentally in a boundary layer wind-tunnel experiments under changes of stack locations and atmospheric stability conditions. Experiments with different conditions of atmospheric stability were conducted using an isolated cubical building model. Tracer gas (C_2H_4) was released from different stack locations on the building roof. Flow, temperature and dispersion fields were analyzed and measured using a split fiber probe, a cold-wire thermometer, and high-response flame ionization detector. Atmospheric diffusion was examined at different distances downwind of the leeward side of the cubical building. Flow and dispersion characteristics studied included mean velocity, turbulent kinetic energy, mean and fluctuation concentrations around the building. The results show that the stable condition increased the vertical velocity around the building. The unstable condition increased the longitudinal velocity around the building. The concentration distributions increased for the right stack and decreased for the lift stack on the building. There is an increase in the concentrations with stable conditions, and a decrease in the concentrations with unstable conditions.