Russian Federation
Purpose: Transport infrastructure facilities include a variety of water supply systems. In the conditions of negative ambient temperatures, there is a risk of freezing and destruction of water pipelines. In mathematical modeling of the operation of aboveground pipelines, the correct description of the heat exchange process between the outer wall of the pipeline and the surrounding atmosphere is of great importance. The boundary condition corresponding to this process traditionally includes a heat transfer coefficient depending on a number of unpredictable parameters (wind speed and direction, atmospheric pressure, air humidity). The purpose of this work is to carry out a comparative analysis of the role of free and forced convective heat exchange and to justify the possibility of setting a boundary condition that depends only on the outside air temperature. Methods: To solve this problem, the work uses numerical analysis of similarity criteria for the heat exchange process under conditions typical for the operation of an above-ground pipeline with thermal insulation. The justification of the boundary condition on the external surface of the pipeline is based on the law of energy conservation. Results: The values of the parameters of the problem are determined, in which free or forced convective heat exchange prevails. It has been shown that forced convection prevails in conditions typical for the operation of above-ground water pipelines. Under these conditions, the difference between the temperature of the external surface of the insulated pipeline and the surrounding atmosphere is small. It has been shown that in this case, it is advisable to use the equality of atmospheric air temperatures and pipeline surface temperatures as a boundary condition. Practical significance: Understanding the mechanisms of heat exchange makes it possible to create an adequate model of the operation of pipelines in conditions of negative temperatures. Setting a more accurate and simple boundary condition on the surface of the pipeline simplifies the task of mathematical modeling. The results obtained in this article can be used in mathematical modeling of any pipelines with thermal insulation.
Above-ground pipeline, heat insulation, convective heat exchange, heat transfer coefficient, boundary condition, mathematical model
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