CFD predictions for hazardous area classification

Abstract

Abstract This study aimed to describe a Computational Fluid Dynamics (CFD) procedure using the ANSYS CFX software 16.1 and Design of Experiments for the determination of volume and extension of explosive atmospheres due to fugitive emissions of flammable gases. The multidimensional statistical sampling technique Latin Hypercube was used, which defined 100 simulations of random methane gas leak conditions. The CFD model proved to be robust in predicting the extension and volume of the explosive atmosphere for orifice diameters from 0.1 to 2.5 mm, pressure from 0.1 MPa to 12 MPa and temperatures from 0 °C to 400 °C. It was found that the calculation domain must be parameterized 8 m in length for each millimeter of the diameter of the source of release to ensure the predictions. In order not to lose precision for very small diameters, the mesh was parameterized with 50 elements along the orifice diameter. It was proved that gravity does not influence the extension and volume of the explosive atmosphere at sonic emissions. The deviation from the ideal gas behavior in the reservoir, achieved by applying the Soave–Redlich–Kwong equation of state, also has not significantly influenced the extension and volume of the explosive atmosphere. The results showed that the size of the explosive atmosphere varies directly with the diameter of the source emission and reservoir pressure, and inversely with the temperature of the reservoir. The diameter of the source is the parameter that has the major effect on the extension of the explosive atmosphere, followed by the pressure and lastly the temperature of the reservoir.