LIBERAÇÃO ACIDENTAL EM LINHA DE GÁS PRESSURIZADA: SIMULAÇÃO DE CENÁRIOS E GERAÇÃO DE DADOS PARA MODELOS DE GESTÃO DE RISCO

Abstract

Three numerical models were proposed to represent the main phenomena resulting from the leakage of pressurized gases in pipe using the Ansys Fluent software, each of the presented models were validated qualitatively and quantitatively. The experiments used for validating the proposed numerical models were, Botros et al. (BOTROS et al., 2004) for depressurization, Eggins and Jackson (EGGINS; JACKSON, 1974) for expansion and Davies and Singh’s (DAVIES; SINGH, 1985) for dispersion. The results obtained were satisfactory because the maximum mean error range obtained for the MG (geometric mean) and VG (geometric variance) were between 4,97% and 8,88% in relation to the experimental parameters. The results for the depressurization phenomenon showed a fast pressure drop over time to approximately 5 MPa that persisted in P1 and P8 sensors located at 0,399 m and 1,149 m before the outlet to atmosphere. For the expansion phenomenon, the main regions were obtained, which are the barrel-shaped shock and the limit region of transition from Mach ≫1 to ≤1 called “Mach disk”, necessary for the correct lifting of the input data for the dispersion phenomenon, it was obtained at 4,56 mm after the pipe exit, with an error of only 2.04% in relation to the equation proposed by Franquet et al. (FRANQUET et al., 2015). Finally, the dispersion phenomenon had as its principle the validation of the pollutant gas (Freon 12) concentration field in a domain where an obstacle was 50 m from the leak source. The model well represented the behavior of the molar concentration of Freon 12 on the windward and leeward faces of the obstacle, showing that its presence increases the lateral dispersion of the gas and traps it for a longer time on the leeward face, showing the maximum distance that the pollutant gas cloud can reach, beyond the critical points of the study domain in relation to the dangerous concentration of the polluting gas. How contributions, the use of the patch tool present in fluent allowed the application to the mesh elements of the stagnation conditions of the pipe as well as the environment conditions, representing better the physics of the problem, moreover, mesh adaptive was used to capture velocity and pressure gradients, significantly improving the results, therefore UDF (User Defined function) applying to accounted for the buoyancy effects caused by the density change by the real gas equation of Peng-Robinson. The presented models will be a great tool to help gas pipelines companies and industries with to know the main consequences resulting from this type of leak that later create a database through an application case, formulating more accurately plans for contingency for this type of accident. Key words: Pipelines; leakage phenomena; pressurized gases; Ansys Fluent.