Study On Heat Transfer Of Shutdown And Restart Of Buried Oil Pipeline

The calculation method about shutdown and start-up of buried oil pipelines has been studied in this paper, and numerical simulation program has been developed. The study involves complex multiphase flow problems and relates to many fields such as oil-gas gathering and transportation system, thermodynamic engineering, heat transfer, numerical heat transfer, experiment technology and computer technology etc, around which, the paper researched in several aspects as following.1 Heat transfer characteristics and unstable environment in the process of buried pipeline transportation change have been discussed. Using a rectangle area as simplification of hemi-infinity ground and considering the influence that buried pipeline and its surroundings temperature field act on each other, a new mathematic model has been built, which simplified later calculation greatly.2 New physical and mathematical models have been built to calculate the surroundings temperature field and its reliability has been testified by program calculations and experiment research. Considering different pipeline parameters, the equations are discrete according to finite element and finite difference methods.3 Heat conduction differential equations with its boundary condition are provided to establish the physical and mathematical model of buried pipeline in the shutdown. Considering the variable thermodynamic parameters of the covered desert sand and the influence of phase-change, the calculation method is advanced and a program is developed for heat transfer simulating of buried pipelines, which can worked out the unstable temperature field and oil temperature unstable change after pipeline shutdown. Comparing with the test result, the program is revised, and its reliability makes it available for engineering calculation.4 To get the change law of buried oil pipeline in unstable environment, the ground unstable temperature field change law of unstable thermal process has been discussed. Data calculated by program is testified by test data; calculate result is exactitude and can response the locale working, which can be used in actual engineering calculation.5 Restart physical and mathematical models of overhead and buried pipelines are established. Heat conduction differential equations with its boundary condition are provided. The simulating program about the pipelines restarting is devised. The medium temperature in pipelines relates with time and location when the overhead pipelines restarting. And the flow temperature will decrease exponentially before pipeline is filled with medium. The change law of the buried pipeline is resembled with the overhead ones when starting. Due to buried depth and soil parameters, the temperature change more slowly. In periodical unstable environment condition, the relationship that flow medium temperature change varies with distance has been studied in buried pipelines. The flow medium temperature is influenced by many factors, such as restarting season, buried depth, flow velocity and thickness of insulating layer etc. 6 A suit of heat transfer experiment equipment about buried pipelines has been established.A suit of heat transfer experiment equipment about buried pipelines has been established to research shutdown and restart about pipelines under different situation.According to exploration and research in this paper, academic reference and scientific basic, about the shutdown and restarting of buried pipelines in different situation, are provided, which is benefit to the developing of this field and makes magnificent sense for academic and application.