Buried Pipe Temperature Field Calculation And Analysis

The directly buried technology has manifest economical and social benefit for small area, quickly built, good performance of heat preservation, long service life, low cost, saving construction material and manpower, environmental factors and so on. Technologies of directly buried hot water pipes have been mature and are widely used in thermal pipe network of a city. Now people are trying to apply those technologies to steam transportation. For its high temperature, multi-layer insulation is used. But as a result of lacking parameters about the form of layers and thickness of layers, insulation layers aren't used effectively and some accidents are caused as well. Developing a method of designing insulation layers is key to advance technologies of multi-layer insulation pipes.Effective forms of multi-layer insulation can't be gotten unless the temperature and the rate of heat flow in insulation layers, especially in the boundary of insulation layers can be calculated. In this paper, the heat transfer problem in directly buried pipes with multi-layer insulation was solved by boundary element method and the corresponding computer program was designed.The first chapter presents the significance and its values in the practice of the task. It briefly introduces the development history of BEM and its advantage. The main task of this paper is presented in the chapter.In the second chapter the theory of weighted residual technique is illustrated and the boundary integral function of the potential problem is deduced by it. Method of obtaining Green's function fundamental solution is presented. It also illustrates how to deal with inhomogeneous regions and the third boundary condition. At last the numerical solution of boundary integral function is presented.The third chapter is the major work of the paper. It deals with mathematic model construction of the problem and ideas of designing the computer program. It also introduce the concept of economical thickness of insulation layer and how to design the computing program to optimize the thickness of insulation layer. It also presents interface of the program, the frame figure of a subprogram and explains how to use the program.The fourth chapter is the emphasis of the paper. At first, the program calculates an instance that can be solved by analytical method. By comparing the results obtained by the two methods it demonstrates that the program is credible and its result is precise. Then some rules are achieved by analyzing the results of many different cases.Finally in the fifth chapter an overview of the thesis is made and the research in future is foreseen.