The article describes the basic principles of mathematical modeling of sampling devices (SD) in order to determine the design of their sampling tubes, allowing to ensure the highest representativeness of samples. The calculations were carried out for slot-type SD that are widely used at present in systems for measuring the quantity and quality of oil. To establish the boundary conditions for mixing the components, the authors substantiated the mixing criteria. To calculate the solution model, a dispersion turbulence model was chosen, implemented in the ANSYS application software. The analyzed components contained in the stream were water, chloride salts, and mechanical impurities. The main results obtained indicate the operability of the mathematical model, which makes it possible to calculate the SD for various incompressible media. The main research results also include the following conclusions. An increase in the content of chloride salts in the stream improves the representativeness of the water samples taken; increased turbulization of the flow can lead not only to an improvement in the representativeness of samples, but, under certain conditions, to their deterioration; in some cases, the representativeness of samples for water and chloride salts may coincide. In the process of research it was noted that it is impossible to obtain the same improvement in the representativeness for all substances contained in oil (in some cases, an improvement in the representativeness of samples for mechanical impurities led to deterioration in the previously achieved representativeness for water). Thus, the task of uniform improvement of the representativeness of samples with respect to water, mechanical impurities and chloride salts was taken as an optimization problem. In the course of research, this problem was solved: the obtained design of the SD allows to improve the representativeness of samples for water by 17.29%, for chloride salts by 21.89 %, for mechanical impurities by 6.77 %.
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