The real-world conditions of oil transportation by pipelines may require the use of drag-reducing additives (DRAs). Considering that in addition to the reduction of hydraulic resistance (by reducing dissipative heat release), DRAs can reduce the heat transfer percentage to a much greater extent (operating as an “insulator”), the identification of the area where these competing factors appear becomes quite promising for potential practical application in non-isothermal pumping. The conventional ratios of the heat transfer theory do not take into account potential presence of substances in the moving media, which small concentrations can significantly affect the heat transfer rate. There are only a limited number of studies related to the quantification and use of this effect in the engineering applications. One way to include the influence of additives on the heat transfer process is to modify the criterion dependence for the Nusselt number. This study uses a different approach based on the assumption of the velocity field approximation to the temperature field. An indirect measurement model for the heat transfer factor and a procedure for experimental determination of the additive performance in reducing the heat exchange with the environment are formulated. The comparison of calculated values against test bench measurements from the Scientific and Technical Center of The Pipeline Transport Institute LLC (in Ufa) is presented. The results confirm that the “insulator” effect develops at high temperature differences and high hydraulic efficiency of DRAs. The testing of the DRA solution cooled in diesel fuel with the temperature control on the measuring line showed the thermal-hydraulic flow conditions generated in the test bench to be close to the self-similar conditions. The determinant similarity criteria are the Eckert number and the criteria describing the law of fluid flow resistance in circular pipes.
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