Experimental Research On Characteristic Of Oil's Temperature Decrease In Buried Pipe By Real Scale Flow Loop

The Pipeline's transporting condition is increasingly complex, leading to a higher requirement for the safe operation and running assurance. The processes of real pipeline's commissioning,shutdown and restart are simulated with the real flow-loop's two diameters(DN300 and DN150), the length and depth are 402m and 2.2m. The heat and the initial restart-pressure wave velocity's transfering are studied, which can provide technical reference for the safety of waxy crude oil pipeline's running.Firstly, the effects of preheating caused by changing running conditions (eg.flow's change, oil temperature's fluctuations and preheating suspension) are investigated, the correlation analysis of the soil's heat-storage,heat-affected radius and the isothermal lines are made. By selecting four shutdown conditions, which include the production's long,medium and short-term accidents, the analysis of soil's temperature decrease scope is made and it's power function relationship between soil's recovery time and shutdown time in the range of 1.5m around pipeline is got. At last, the criterion equation of nature convection is regressed using the oil's decreasing temperature data.Secondly, the initial restart-pressure wave velocity of the oil transported in Qin-Jing pipeline is measured by the flow-loop. Base on 20 groups of the wave velocity experimental data, the program of BP artificial neural net is wrote for forecasting, which can forecast the restart-pressure wave velocity with acceptable error. By the range analysis of orthogonal experiment theory, the restart-pressure wave velocity's influencing factors (restarting temperature,restarting flow and stop temperature)and its impact are analyzed. The oil's cooling contraction and structural change during shutdown is characterized by the concept of temperature affecting coefficient put forward firstly and the empirical formula is fitted, having the advantage of simple form and convenient operation. Comparing to the current different calculation methods and experimental data in different flow-loop's diameters, the empirical formula fits better.Then, the two-dimensional physical and mathematical models are established. The heat-transfer form of nature convection is transferred into conduction using the law of equivalent thermal conductivity and the form of differential equations is unified. The issues of the latent heat of wax and the division of the liquid-solid phase are solved by using the oil's C-T relations and the temperature of stagnation point. The software is formed which can be used to simulate the temperature decreasing process about the buried pipeline.At last, against the simplifying of soil's numerical calculation as the conduction form and the soil moisture's impact on heat transfer, one-dimensional heat and moisture transfer model is improved and a preliminary study is made about the temperature and moisture's distribution around the pipeline.