To provide main pipeline safe operation in course of transportation of oils with non-Newtonian rheology, a possibility to start temporarily shutdown pipelines shall be ensured. In this regard, a problem of predictive evaluation of congealed oil starting pressure is relevant. Uncertainty of this design value depends on initial parameters, specified by ranges of values. Use of an analogy between computing experiments and indirect measurements in theoretical metrology has permitted to apply a standard procedure on expressing the uncertainty to the starting pressure value. Calculations show that the oil temperature, which is initial information, contributes maximum uncertainty at the final calculation stage, the total value of which could reach 70% and more. A comparative assessment method for various modifications of calculation models for a specific sought quantity through standard uncertainty comparison is an effective formalized instrument, which is universal. Modification of a known starting model with account of oil parameters nonuniformity in radial direction was performed. With account of known experimental data, a scheme of congealed oil displacement with partial section was adopted, and a procedure for this section radius definition was offered. At that it is possible (with account of an obtained recalculation formula) to apply results of engineering calculations in compliance with an approach, which uses oil temperature averaged in cross section in each pipeline point. Prospective of using a medium flow mathematic model based on a combined rheological model of Kelvin - Voigt body and a viscoplastic Bingham model was noted.
References
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