Martynov, S;
Mahgerefteh, H;
Nikolaidis, IK;
Economou, IG;
(2021)
Entropy – stagnation enthalpy interpolation tables for calculation of the critical flow properties of compressible fluids.
Presented at: Qatar Process Safety Symposium (QPSS 2021), Doha, Qatar.
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Abstract
High-pressure pipelines provide the most cost-effective and established method for long-distance transportation of large quantities of compressible fluids, such as natural gas, hydrogen and carbon dioxide. Given significant safety hazards associated with these pipelines, their design and operation requires using mathematical modelling tools quantifying consequences of accidental pipeline failure. Central to this is the accurate and robust prediction of the critical discharge flow from the pipeline, accounting for the real fluid thermodynamic behaviour, including the phase transition induced by the decompression process. In this work, a method of inverse interpolation tables is developed to calculate physical properties of compressible fluid, for use in a computational model of transient outflow from an accidently ruptured pipeline. In particular, the density – energy interpolation tables are applied to calculate the fluid pressure, temperature and phase composition as required for solving the mass, momentum and energy conservation equations describing the decompression flow inside pipeline, while the entropy – stagnation enthalpy interpolation tables are introduced to obtain the critical (choked) flow properties at the rupture section of the pipe. To construct the latter, the choked flow properties are calculated by solving simultaneously the total enthalpy conservation equation along with the constant entropy condition. The interpolation is performed using Akima splines fitted to the thermodynamic properties data predicted using highly-accurate Perturbed Chain-SAFT (PC-SAFT) equation of state. The interpolation tables are constructed for ethylene and carbon dioxide, covering pressures from 0.1 to 10 MPa and temperatures ranging from the triple point to 350 K. The study provides recommendations for the optimal resolution of the interpolation tables to achieve a balance between the accuracy and computational efficiency of the calculated physical properties. Practical implementation of the interpolation method in a pipeline decompression flow model is discussed. Acknowledgement. This research has received funding from the European Union’s Horizon 2020 Research & Innovation Programme under the Grant Agreement No 884418, and Qatar National Research Fund (a member of the Qatar Foundation) NPRP award 8-1339-2-569.
| Type: | Conference item (Presentation) |
|---|---|
| Title: | Entropy – stagnation enthalpy interpolation tables for calculation of the critical flow properties of compressible fluids |
| Event: | Qatar Process Safety Symposium (QPSS 2021) |
| Location: | Doha, Qatar |
| Dates: | 21 - 22 June 2021 |
| Open access status: | An open access version is available from UCL Discovery |
| Publisher version: | https://qpss.qa/qpss-2021-2/ |
| Language: | English |
| Keywords: | Pipeline rupture, two-phase flow, critical flow, choked flow, homogeneous equilibrium model, CO2 |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10136283 |
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