Session: 07-01-01 Liquids Release Consequence

Paper Number: 133911

133911 - Implementation and Optimization of a Multiphase, Transient Release Rate Model for Consequence Estimation 

Abstract: 

Unlike natural gas pipelines where the maximum life safety impact from a large leak or rupture is determined within the early phases of a release, the life safety consequences of CO₂ pipelines and pipelines carrying other toxic chemicals are affected to a greater extent by the temporal decay of the release rate over a much longer timescale. A critical part, therefore, of evaluating the hazard due to releases is outflow modelling. To bridge this technical gap, as well as to produce a general model suitable for evaluating a wide range of product types including natural gas and natural gas-hydrogen blends, a multiphase, transient release rate model was implemented by C-FER Technologies (1999) Inc. (“C-FER”).

This paper discusses the improvements made by C-FER to a method of characteristics-based flow solver, specifically of a formulation described by the University College of London. The method of characteristics is a mathematical strategy used to solve partial differential equations, which has had much success in solving transient scenarios containing shocks or phase-changing fluids. C-FER has improved the evaluation of release scenarios and its use in probabilistic modelling through calculation improvements , including:

a) an adaptive grid implementation, which intelligently restricts the calculation burden to points of the domain that experience significant changes and also supports the use of a locally derived timestep;

b) REFPROP-powered equation of state property lookup, which uses the state-of-the-art accuracy provided by REFPROP and converts the properties into a form that can be rapidly queried without having them be pre-established;

c) a 1D wall treatment, which effectively captures the finite rate at which the wall can supply thermal energy to the fluid by simulating the temperature variation through the wall’s depth; and

d) an enhanced boundary treatment that uses a steady-state implementation of the conservation equations to extrapolate beyond the calculation domain to better approximate a semi-infinite pipeline.

Finally, this paper will illustrate the model’s application in Monte Carlo simulations where the results of using a surrogate model to interpolate the output of subsequent runs from the release rate model, and predicts the release rates over time and, therefore, consequences for cases which were not directly solved by the multiphase, transient release rate model.

Presenting Author: Steven Middleton CFER Technologies Inc.

Presenting Author Biography: Steven Middleton is a Researcher in the Pipeline Integrity and Risk Management department of C-FER Technologies. At C-FER, his focus has been on pipeline consequence estimation, which has specialized into hydrogen releases, CO2 outflow modeling, pipeline crack arrest and dense gas based hazards but also a number of initiatives related to computational modeling and specialized algorithms. He holds an MSc in Mechanical Engineering from the University of Alberta, where his research was the implementation of a modular thermodynamic simulation program for predicting the performance of low-temperature Stirling engines.

Authors:

Steven Middleton CFER Technologies Inc.
Aiden Svitich CFER Technologies Inc.