Hybrid Methods in Engineering Modeling, Programming, Analysis, Animation

ISSN for PRINT: 1099-2391

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2000, Volume2

Issue 3

110 pages

Issue price - $125.00

Rubem da Cunha Reis
Depto. de Eng Quimica, PUCRS e Programa de Pos-Graduacao em Engenharia Mecanica, UFRGS, Av. Ipiranga 6681, CEP 90619-200, Porto Alegre, RS, Brazil

Cesar Antonio Leal
Depto. de Eng Nuclear e Programa de Pos-Graduacao em Engenharia Mecanica, UFRGS, Av. Sarmento Leite 425, CEP 90050-170, Porto Alegre, RS, Brazil

The evaluation of consequences of industrial accidents requires modeling and estimation of the physical effects of a chain of events that compose the accident scenario. Whenever a dangerous substance is accidentally released into the atmosphere, the estimate of the possible number of casualties, in a given situation under consideration, needs quantification of the amount of material being released, its physical state, and the amount of it that goes into the gaseous state to compose the source of gas for atmospheric dispersion, the region covered by the cloud, and, finally, the interaction of the cloud with the population in the area covered by the cloud of gas. Transportation of ethylene between distant points is done under very high pressures, above the critical pressure for this substance. Accidents happening under these circumstances require special treatment in terms of modeling of the behavior of the material leaving the system, to allow the simulation of the scenario. In this work, the rupture of a pipeline initially at a supercritical pressure is modeled for the calculation of mass flow, temperature, and pressure as a function of space and time, as the material is released into the atmosphere, forming of a two-phase critical flow. The evaluation of the consequences for risk analysis involves the characterization of the discharge of material following the accident. For the case of a rupture in a pipeline containing ethylene at very high pressure, the evaluation of the dispersion of the gas in the atmosphere requires the amount of ethylene released as a gas to form the source term for dispersion. The resulting set of partial differential equations was solved by a hybrid method in which the equations were integrated over a discretized region of the x, t plane (method of Godunov) and the solution found using characteristic directions. Results are presented and discussed for the calculation of the amount of ethylene discharged to the atmosphere due to the rupture of a pipeline initially at 10.1 MPa and ambient temperature (298 K).

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