A dense gas is defined as any gas whose density is greater than the density of the ambient air through which it is being dispersed. This result can be due to a gas with a molecular weight greater than that of air or a gas with a low temperature due to auto-refrigeration during release, or other processes. The importance of dense gas dispersion has been recognized for some time. Early field experiments (Van Ulden, 1974; Puttock et al., 1982; Koopman et al., 1984) have confirmed that the mechanisms of dense gas dispersion differ markedly from neutrally buoyant clouds. The situation is further complicated when dense gases are released in an indoor environment. Available transport and dispersion models for modeling of dense gases are differentiated by release time into instantaneous and continuous categories. A wide category of models has been developed on the assumption that the mean concentration of a species emitted from a point source follows a Gaussian distribution. Such an approach is questionable when it is applied to an indoor environment where strong three dimensional flow effects are present.
In this work, a CFD based model is developed for simulating the dense gas dispersion in an indoor environment. The model is validated with the experimental literature data. The spatial and temporal variation of the dense gas concentrations is predicted under a given flow domain and initial and boundary conditions. The results bring out the unique characteristics of spreading and dispersion of dense gases and its application to risk assessment is discussed. The information of the local concentration would also help in designing of mitigation systems and emergency evacuation measures.