Abstract
Mathematical model of non-isothermal gas flow within the framework of tube hydraulics including change of tube cross-section due to hydrate formation and the dependence of coefficient of heat transfer between gas and hydrate layer on varying flow area is proposed. The corresponding conjugate problem of heat exchange between imperfect gas in the pipeline and the environment is reduced to the solution of differential equations describing non-isothermal flow of gas in pipes and heat transfer equations in ground with the corresponding conjugation conditions. In the quasi-stationary mathematical model of hydrate formation (dissociation), the dependence of gas-hydrate transition temperature on gas pressure is taken into account. Some decisions taken in the design of the first section of the main gas pipeline «Power of Siberia» have been analyzed. It has been shown that if gas is not sufficiently dried, outlet pressure may drop below the technological limit in about 6-7 hours. At the same time, for completely dry gas ,it is possible to reduce the cost of thermal insulation of the pipeline at least two fold.
Highlights
The analysis was performed within the framework of the mathematical model of hydrate formation during gas flow in pipes, proposed in the monograph [3] and modified in subsequent publications of the authors [4,5,6,7,8,9]
In the model gas flow in pipe with a crosssection that changes with time is described in a quasi-stationary approximation, since the rate of transition process in pipeline is much higher than that of temperature changes in surrounding frozen ground due to thermal conductivity
The quasi-stationary mathematical model of formation of hydrates in gas pipeline takes into account that the heat transfer coefficient from gas to inner wall of pipe depends on changing with time cross-section as well as that gas-hydrate phase transition temperature depends on flowing gas pressure
Summary
The analysis was performed within the framework of the mathematical model of hydrate formation during gas flow in pipes, proposed in the monograph [3] and modified in subsequent publications of the authors [4,5,6,7,8,9]. In the model gas flow in pipe with a crosssection that changes with time is described in a quasi-stationary approximation, since the rate of transition process in pipeline is much higher than that of temperature changes in surrounding frozen ground due to thermal conductivity.
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