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Solidifying transportation of goods by rail, namely, tank wagons is accompanied a number of difficulties. These include: lowering the temperature of the transported oil, accompanied by the growth of its viscosity, the inability to quickly discharge, change in performance of transported oil products, an increase in idle tank cars. The analysis of the cooling rate of the goods transported, depending on the size and thickness of the insulating layer. Introduced formulas show that the presence of the heat-insulating sheath is cylindrical vessel radius deviation from the optimum value. When this thermal insulation reduces considerably the heat transfer coefficient in the surrounding area and to accelerate the discharge process.

Transportation in tank cars of viscous liquid cargo (fuel oil, paraffins, industrial oils, cracking residues, etc.) is difficult with their solidification, accompanied by a sharp increase in viscosity. In fact, this leads to the need to warm up or partially warm up the transported oil product before unloading, usually carried out as a gravity discharge, in order to restore the fluidity of the delivered oil cargo. The process of unloading in this case with heating leads to a significant increase in the cost of transporting petroleum products, including the downtime of tank cars, and in general, a decrease in the turnover of rolling stock. According to the analysis carried out to determine the costs of the technological process of heating frozen petroleum products transported by rail, about 600 thousand tons of conventional fuel are spent per year, and the idle time of tank cars under unloading and subsequent cleaning of boilers from high-viscosity residues of oil cargo exceeds 1 million car-hours. The urgency of the issue of reducing the cost of railway transportation of viscous cargo is due to the intensive development of the Northern and Eastern regions of the Russian Federation. Important factors for transportation in these conditions are not only the negative average daily air temperature, but also long distances. The issue of reducing the cost of transportation of viscous petroleum products at low air temperatures is considered. Viscous petroleum products, when thickened, turn into a rheological liquid, which does not have a clear interface between the liquid and solid phases. The methods of transfer to the stratified state of hot fuel oil during its slow cooling and partial solidification with the formation of a heat-insulating layer of solidified fuel oil are applied. The positive effect is achieved by reducing the time and cost of thermal energy for unloading the delivered oil product by reducing the rate of its cooling during transportation. This, in turn, is achieved by suppressing the natural convection of the hot oil product on the cold walls of the boiler of the tank car in the first few hours after filling the tank. From the comparison of the experimental data and the calculation results, the values of the empirical coefficients of the equation for the heat transfer coefficient of liquid petroleum products are selected. The standard deviation of the absolute temperature of the liquid petroleum product was 8 %.