Release:
2021. Vol. 7. № 4 (28)About the authors:
Aleksandr A. Vakulin, Dr. Sci. (Tech.), Professor, Honorary Worker of Science and High Technologies of the Russian Federation, Professor of the Department of Applied and Technical Physics, Institute of Physics and Technology, University of Tyumen; a.a.vakulin@utmn.ruAbstract:
The article presents the formulation and solution of the associated problem of oil cooling when the underground laying oil pipeline stops and the temperature changes in frozen soil in the presence of moss and snow cover on the surface. A physical and mathematical model and an associated computational algorithm for calculating the parameters of oil in a pipeline and soil with covers have been developed. Peculiarities of solidification of oil containing N-fractions of paraffins during heat removal into frozen soil have been studied. In this work, an important solved problem is the approximation of a characteristic diagram of phase equilibrium states during cooling of paraffinic oil in the temperature range from the onset of crystallization of paraffins to the pour point. A feature of the problem being solved is that the temperature field of oil in the pipeline (region A) and the temperature field of the moist soil surrounding the pipeline (region B) have a common border — the pipeline wall, which is assumed to be thin. Through the pipeline wall, the temperature of which is not known in advance, the mutual influence of temperature fields (conjugation) is taken into account. The results of an experimental study of changes in the temperature in the pipeline with time in laboratory conditions are presented. The calculation results are in satisfactory agreement with experimental data on the solidification of high-viscosity paraffinic oil in a model oil pipeline when the oil is cooled from +4.5 to −5.5 °C. On the basis of the physical and mathematical model developed in this article and the coupled algorithm for calculating the parameters of soil and oil, it has been established that in the presence of moss and snow cover, characteristic of the winter conditions of the Middle Ob region of Western Siberia, in an oil pipeline with a nominal diameter of 700 mm, oil freezes in a time of 40 60 hours depending on soil parameters and oil fractional composition.
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References:
Antip’yev V. N., Bakhmat G. V., Zemenkov Yu. D., Vazhenin Yu. I. et al. 2002. Operation of main gas pipelines. Tyumen: Publishing House “Vector Buk”. 528 p. [In Russian]
Borodavkin P. P. 1982. Underground trunk pipelines (design and construction). Moscow: Nedra. 384 p. [In Russian]
Vakulin A. A., Shabarov A. B. 1998. Diagnostics of thermophysical parameters in oil and gas technologies. Novosibirsk: Nauka. Siberian Publishing Company RAS. 249 p. [In Russian]
Danielyan Yu. S., Yanitskiy P. A. 1990. “The variational principle in the problem of determining the temperature field around a group of underground pipelines”. Energy and Transport, no. 1, pp. 151-157. [In Russian]
Danielyan Yu. S., Zaitsev V. S. 2009. “Determination of the thermal conductivity coefficient of large soil massifs”. Oil industry, no. 5, pp. 98-100. [In Russian]
Dubina M. M., Krasovitskiy B. A. 1983. Heat exchange and mechanics of interaction of pipelines and wells with soil. Novosibirsk: Nauka. 132 p. [In Russian]
Kutrunov V. N., Mikhailov P. Yu., Puldas L. A. et al. 2012. “Experimental research and physical and mathematical modeling of the oil cooling process in an underground pipeline”. Tyumen State University Herald, no. 4, pp. 61-67. [In Russian]
Moroz A. A., Malyushin N. A, Stepanov O. A. 1999. Oil pipelines of Western Siberia. Saint-Petersburg: Nedra. 188 p. [In Russian]
Nigmatulin R.I. 1987. Dynamics of multiphase media. Moscow: Nauka. 464 p. [In Russian]
Puldas L. A. 2008. “Non-stationary thermal conditions in civil buildings”. Cand. Sci. (Tech.) diss. abstract. Tyumen. 20 p. [In Russian]
Sunagatullin R. Z. et al. 2020. “Investigation of the causes of the formation of asphalt-resin-paraffin deposits of commercial oil under the operating conditions of main oil pipelines”. Science and technology of pipeline transportation of oil and oil products, vol. 10, no. 6, pp. 610-619. [In Russian]
Shabarov A. B., Grigoriev B. V., Vakulin A. A. 2011. “Calometric method for determining the content of unfrozen water in frozen soils”. Materials of the international scientific and practical conference on engineering permafrost, dedicated to the 20th anniversary of NPO Fundamentstroyarkos LLC. Tyumen: City-Press. Pp. 436-437. [In Russian]
Shabarov A. B., Mikhailov P. Yu., Puldas L. A., Vakulin A. A. 2010. “Physical and mathematical modeling of temperature and ice content fields in frozen soils around a buried pipeline”. Tyumen State University Herald, no. 6, pp. 14-19. [In Russian]
Deru M. 2003. “A model for ground-coupled heat and moisture transfer from buildings: Technical report NREL/TP-550-33954”. National Renewable Energy Laboratory.
Gopalakrishnan K., Manik A. 2007. “A mathematical model for predicting isothermal soil moisture profiles using finite difference method”. Journal of Civil and Environmental Engineering, vol. 1, pp. 14-20. DOI: 10.5281/zenodo.1332730
Hartikainen J., Mikkola M. J. 2002. “Numerical solution of soil freezing problem by a new finite element scheme”. IUTAM Symposium on Theoretical and Numerical Methods in Continuum Mechanics of Porous Materials. Solid Mechanics and Its Applications, vol. 87, session A4, pp. 61-66.
Jansen H. 2002. “The influence of soil moisture transfer on building heat loss via the ground: Thesis”. Catholic University Leuven.
Li G. et. al. 2010. “Development of freezing-thawing processes of foundation soils surrounding the China-Russia Crude Oil Pipeline in the permafrost areas under a warming climate”. Cold Regions Science and Technology, 2009. Vol 64, iss. 3, pp. 226-234.
Li G. et. al. 2010. “Forecasting the oil temperatures along the proposed China-Russia Crude Oil Pipeline using quasi 3-D transient heat conduction model”. Cold Regions Science and Technology, 2009. Vol. 64, iss. 3, pp. 235-242.
