The paper presents results of an analysis of the wall waxing effect on the thermal-hydraulic parameters of oil along a non-isothermal section of a 70 km long main oil pipeline with a diameter of 1020 mm.
The paper presents the results of numerical modeling performed using the dynamic CFD simulator OLGA SIS SLB in a specialized calculation module for predicting the waxing process WAX DEPOSITION. The research is a continuation of the previously carried out studies of the influence of deposits on the inner wall of an oil pipeline on its thermal-hydraulic efficiency. Experimental confirmation of the possible positive effects of the presence of a natural protective coating on the inner surface of the pipeline in the form of a layer of asphalt-resin-paraffin deposits have already been done previously by the authors according to average indicators. In this article the results is the use of a dynamic modeling process are considered. Dynamic modeling allows to take into account not only the physics of the process in dependence on external thermobaric conditions, but also its kinetics. The results of dynamic modeling are presented in the form of temporal trends and profiles along the length. That made it possible to numerically measure the thermal-hydraulic efficiency of the near-wall sediment layer, taking into account the non-isothermality and kinetic changes of the process. In particular, the high thermal insulation properties of the sediment layer have been confirmed even with its insignificant thickness that makes it possible to significantly reduce heat transfer and significantly increase the final flow temperature (including the average along the pipeline). Thus, that led to a decrease in the average viscosity and a decrease in the rate of deposition growth. The total effect of a thin (only 2 mm) layer of deposits on the inner surface of the oil pipeline with the inner diameter of 1020 mm was expressed in a significant decrease in the pressure drop even for a short section of 70 km. It is shown the need for further study of the issue in order to develop technologies and effective methods of the waxing process to optimize the costs of in-line cleaning and inhibition of deposits. That is important both for relatively cold and hot non-isothermal sections of oil pipelines.
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