Mathematical Model And Optimization Design Study On Pipe-insulation

Energy-saving and environmental protection is a key factor to achive the sustainable development of national economy. Insulation is called the fifth energy. It is effective to improve the pipe insulation for energy-saving and consumption reduction in enterprises. At present, The insulation of single layer for the cylinder-pipe is overwhelming majority in the optimization researches. there is less research on the square-pipe insulation. A complete model of double layer pipe-insulation in square-pipe and cylinder-pipe has been built and the optional design of pipe-insulation structure has been achived by the numerical simulation.The main contents and specialties of this work are cummarized as following:(1) Based on the finite difference method and the enthalpy drop method, a integrated mathematical model of three-dimensional square-pipe insulation is built on considering the thermal conductivity change with temperature,the thermal resistance of pipe inner surface and the physical parameters of medium inside the pipe with temperature. Studies show that the outlet temperature error of media inside the pipe between the calculation and the test is less than 2.1%; a more accurate temperature field and thermal calculations can be provided in square-pipe insulation.The effect of thermal conductivity change and thermal resistance on the outlet temperature of media in the short pipe can be neglected; the thermal conductivity change need be considered to the outlet temperature calculation of media when the pipe length is more than 2.35km; the heat loss error of outside surface of pipe from neglecting thermal conductivity change is more than 11%. It is necessary to consider thermal conductivity change for the heat loss and outlet temperature calculation of media in the long pipe, but thermal resistance of pipe inner surface can be neglected in lower precision demand.(2) In comprehensive consideration of three constraints, for example, heat loss, temperature of outside surface and temperature drop of media inside the pipe, the optiomally internal and external thickness of square-pipe insulation can be obtained. Optimization researches show the price and performance of insulation materials, the heat price, the flow rate of medium inside the pipe are the main factors of economic thickness; there is different optimally internal and external economic thickness of square-pipe insulation in different constraints.The heat loss on unit area, the highest temperature of insulation surface are taken from the increasing of insulation thickness, the outlet temperature of media inside the pipe increases by the insulation thickness.(3) A kind of new software for square-pipe insulation, widely used in the insulation engineering of fluid storage and transportation, the flue of the power boilers and industrial furnaces, and the rectangle industrial furnaces, has been developed. It is combined graphic capacity of Matlab 7.0, friendly interface capacity of Visual Basic 6.0 and Excel, and is successfully used the technology of Hybrid programming with Visual Basic, Matlab and Excel. Three dimensional temperature profile, the outlet temperature of the inner medial, the heat loss and the optiomally internal and external thickness of insulation can be obtained. It is characteristic of the simple operation, the wide application and the interface friendly.(4) An integrated mathematical model of cylinder-pipe insulation is built on considering the thermal conductivity change with temperature, the thermal resistance of pipe inner surface and the physical parameters of medium inside the pipe with temperature. Comparison of the results of square-pipe insulation and cylinder-pipe insulation with equivalent diameter, the results of comparison show that the outlet temperature error of hot air inside the pipe is reduced with the increase of pipe diameter. Square-pipe insulation with long side can be simplified as the cylinder-pipe insulation by the equivalent diameter.