Experimental and numerical study on heavy gas contaminant dispersion and ventilation design for industrial buildings

Heavy gases, in particular sulfur hexafluoride (SF6), are used extensively in the gas insulated substations (GISs) of various industrial buildings, such as nuclear power plants. Although the construction and operation of these facilities are closely monitored and regulated, accidents are possible. A hazardous situation may arise if the SF6 gas in a GIS leaks without effective measures to remove the contaminants in time. In this study, a chamber experiment and CFD numerical simulation were carried out to study SF6 gas dispersion characteristics and the optimal ventilation design for its accidental leakage in industrial buildings. The influence of leakage angle (alpha= 90 degrees, 45 degrees and 0 degrees) on the SF6 dispersion and concentration distribution was analyzed. Several different ventilation design parameters, i.e., air outlet layout, size and air change rate, were proposed to evaluate the ventilation performance. The findings indicated that different leakage angles could result in different space concentration distributions of SF6 and that any leakage angle deviating from 90 degrees could result in an uneven SF6 concentration distribution; a deviation angle of 45 degrees caused the maximum concentration variation in the lower part of the chamber. The removal of SF6 was more effective when the air outlets and inlets were arranged on the same side of the wall. Vent openings and air outlets had a remarkable influence on the removal rate of SF6. It was found that high-efficiency ventilation could be achieved with a 10 h(-1) air change rate, meeting the needs of SF6 emergency ventilation. The current study can serve as a reference for ventilation design and establishment of standards for the accidental leakage of heavy gas in industrial buildings.