CFD predictions for hazardous area classification

doi:10.1016/j.cjche.2018.06.002

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℃ to 400℃. 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.

Key words: Computational Fluid Dynamics, Computer simulation, Safety, Fugitive emissions, Classified area, Flammable gas cloud

摘要： 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℃ to 400℃. 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.

关键词: Computational Fluid Dynamics, Computer simulation, Safety, Fugitive emissions, Classified area, Flammable gas cloud

Andrey Oliveira de Souza, Aurélio Moreira Luiz, Antônio Tavernard Pereira Neto, Antônio Carlos Brandao de Araujo, Heleno Bispo da Silva, Sidinei Kebler da Silva, Jose Jailson Nicacio Alves. CFD predictions for hazardous area classification[J]. Chin.J.Chem.Eng., 2019, 27(1): 21-31.

References

[1] J.T. Miranda, E.M. Camacho, J.A.F. Formoso, J.D.R. Garcia, Comparative study of methodologies based on Standard UNE 60079/10/1 and computational fluid dynamics (CFD) to determine zonal reach of gas-generated Atex explosive atmospheres, J. Loss Prevent. Proc. 26(2013) 839-850.

[2] IEC 60079-10-1/Ed2, Explosive Atmospheres-Part 10-1:Classification of Areas-Explosive Gas Atmospheres, 2015.

[3] R. Thommasini, E. Pons, F. Palamara, Area classification for explosive atmospheres:Comparison between European and North American approaches, Industry Applications Society 60th Annual IEEE 2013, pp. 1-7.

[4] ABNT NBR IEC 60079-10-1(2009).

[5] D.M. Webber, M.J. Ivings, R.C. Santon, Ventilation theory and dispersion modelling applied to hazardous area classification, J. Loss Prevent. Proc. 24(2011) 612-621.

[6] A. Macmillan, Electrical Installations in Hazardous Area, Elsevier Science LTD, Oxford, United Kingdom, 1998.

[7] B.C.R. Ewan, K. Moodie, Structure and velocity measurements in underexpanded jets, Combust. Sci. Technol. 45(1986) 275-288.

[8] X. Liu, A. Godbole, C. Lu, G. Michal, P. Venton, Source strength and dispersion of CO₂ releases from high-pressure pipelines:CFD model using real gas equation of state, Appl. Energy 126(2014) 56-68.

[9] E. Rathakrishnan, Gas Dynamics, 5a ed. Prentice-Hall, 2006.

[10] E. Franquet, V. Perrier, S. Gibout, P. Bruel, Free underexpanded jets in a quiescent medium:A review, Prog. Aerosp. Sci. 77(2015) 25-53.

[11] M.J. Ivings, S. Clarke, S.E. Gant, B. Fletcher, A. Heather, D.J. Pocock, D.K. Pritchard, R. Santon, C.J. Saunders, Area classification for secondary releases from low-pressure natural gas systems, Health and Safety Executive Research Report, RR6302008.

[12] S.E. Gant, M.J. Ivings, A. Jones, R. Santon, Hazardous Area Classification of Lowpressure Natural Gas Systems Using CFD Predictions, Hazards XIX, Manchester, UK, 2006.

[13] R. Santon, M. Ivings, D. Webber, A. Kelsey, New Methods for Hazardous Area Classification for Explosive Gas Atmosphere, Hazard XXⅢ Symposium Series Vol. 158(2012) 339-346.

[14] F. Bonelli, A. Viggiano, V. Magi, How does a high density ratio affect the near- and intermediate-field of high-Re hydrogen jets? Int. J. Hydrog. Energy 41(2016) 15007-15025.

[15] B. Chernyavsky, P. Benard, P. Oshkai, N. Djilali, Numerical investigation of subsonic hydrogen jet release, Int. J. Hydrog. Energy 39(2014) 6242-6251.

[16] L. Dong, H. Zuo, L. Hu, B. Yang, L. Li, L. Wu, Simulation of heavy gas dispersion in a large indoor space using CFD model, J. Loss Prevent. Proc. 46(2017) 1-12.

[17] Q. Zhang, S. Mo, D. Liang, Numerical simulation of natural gas release and risk zone forecast in urban areas, Procedia Eng. 71(2014) 470-475.

[18] ANSYS INC, ANSYS CFX-Solver Theory Guide, ANSYS CFX Release 11.0, ANSYS, Inc., Southpointe, Canonsburg, 2006.

[19] F.R. Menter, M. Kuntz, R. Langtry, Ten years of industrial experience with the SST turbulence model, Proceedings of the Fourth International Symposium on Turbulence, Heat and Mass Transfer, Antalya, Turkey October, 2003, pp. 12-17.

[20] L.E. Sissom, D.R. Pitts, Elements of Transport Phenomena, McGraw-Hill Book Company, New York, 1972.

[21] S.I. Sandler, Models for Thermodynamic and Phase Equilibria Calculations, Marcel Dekker, New York, 1994.

[22] S.I. Sandler, Chemical and Engineering Thermodynamics, 3rd ed. John Wiley & Sons, New York, 1999.

[23] A.D. Birch, D.R. Brown, M.G. Dodson, F. Swaffield, The structure and concentration decay of high pressure jets of natural gas, Combust. Sci. Technol. 36(1984) 249-261.

[24] R.R. Walpole, R.H. Myers, S.L. Myers, K. Ye, Probability & Statistics for Engineers & Scientists, Eighth edition Pearson Education International, 2007.

[25] F. Bonelli, A. Viggiano, V. Magi, A numerical analysis of hydrogen underexpanded jets under real gas assumption, J. Fluids Eng. 135(2013) 121101-121111.

[26] R. Khaksar, M.R. Kameshki, M. Paraschivoiu, Numerical simulation of high pressure release and dispersion of hydrogen into air with real gas model, Shock Waves 20(2010) 205-216.

[27] A.O. Souza, A.M. Luiz, A.T.P. Neto, A.C.B. Araujo, H.B. Silva, S.K. Silva, J.J.N. Alves, A new correlation for hazardous area classification based on experiments and CFD predictions, Process. Saf. Prog. 37(2018)https://doi.org/10.1002/prs.11974.