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International Symposium on Heat and Mass Transfer in Refrigeration and Cryogenics
September, 1-5, 1986, Dubrovnik, Yugoslavia

DOI: 10.1615/ICHMT.1986.IntSympHMTinRefCryo


ISBN Print: 978-3-54017-957-3

Numerical Study of a Buried Gas Pipe at Negative Temperature. Comparison of Several Models with a Pilot Experiment

pages 324-333
DOI: 10.1615/ICHMT.1986.IntSympHMTinRefCryo.240
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摘要

The operating conditions of the pressure regulating stations on the gas transmission networks often induce a significant cooling of the gas due to Joule-Thomson effect. Then the gas temperature downstream these stations may be found as low as −20°C or even less.
The effect of such low temperatures is the freezing of the soil around the pipe, a few hundreds meters along, causing damages related to ground heave, particularly for pipes buried below roads or pavements, and ice formation on the road or in the water mains incidentally located in the neighborhood.
Consequently, "Gaz de France" (GDF) has been led to approach this kind of problems in order to limit these harmfull effects around pipes in the case of existing equipments and to find good solutions in the case of new installations (shape, location, kind of soils, thermal insulation, etc.). Particularly, field experiments have been conducted in pilot stations and a lot of data concerning the thermal behaviour around the gas pipes have been collected.
Moreover, G.D.F. has developed certain mathematical models. Nevertheless, these models deal only with the stationary thermal problem and don't take into account the freezing phase change.
Consequently, it was very important to compare the results of these simplified models with those obtained with the help of more sophisticated models which take into account the phase change phenomenon and transient analysis. The results of this comparison could allow a more wide knowledge of the problem and a better control for the applications.
Particularly, it was interesting for G.D.F. to know the displacement of the freezing front in function of time. This information allows the estimation of the moment when the interface reaches the location corresponding to 90%, 95% or 100% of the 0°C isotherm location of the stationary system.
This paper reports the results of a collaboration between G.D.F. and the Freezing-Sublimation group of the "Laboratoire d'Aèrothemrique du CNRS" (Meudon, France) (LA) who disposes of two sophisticated numerical models.
The application of the different numerical models and the comparison of results with field data are presented. Conclusions and suggestions are formulated.

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