| Summary: | A partition method mathematical model was established for the shutdown process of an overhead pipe, and the effects of crude oil’s variable physical properties on the heat transfer performance were analyzed. The model and solving method were verified by the existing experimental data. The oil temperature distribution in pipe was simulated by FLUENT software, and the allowance shutdown time, which is the time of the oil temperature in the pipe center that it takes to drop to its freezing point, was discussed. In simulation, oil properties including densities, thermal conductivities, viscosities, and specific heat were modeled with their values as functions of temperature or set to their average values in the temperature range. Results show that compared with the latter (oil properties were average value), the allowance shutdown time using variable physical properties were shortened by 16.3%, 7.9%, 0.2%, and increased 61%, respectively; the influence of thermal conductivity was embodied in the second half of the shutdown process. In numerical simulation of the shutdown process for an oil pipeline, the effect of oil viscosity variation can be ignored and, the other properties must not be regarded as constant, especially heat capacity, whose change reflects the influence of latent heat.
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