Insulation Situation Test And Evaluation Study Of The Primary Network In District Heating System Of Chengyin District In Daqing City

Thermal insulation of district heating pipelines is the main measure to cut down the heat loss during heating medium transportation. Heating Pipe insulation situation affects not only enterprise efficiency but also user’s thermal comfort. Make sure the heating pipes are in good insulation situation is also the requirement of energy conservation and emission reduction. In order to know if the insulation is in good situation, a thermal insulation test should be carried out. This paper carries out a thermal insulation test on the primary heating pipelines in Chengyin district in Daqing City, research contents are as follows:(1) This study summarizes the principles and applicable scope of insulation test and evaluation methods. Select evaluation method and develop test schemes based on the installation conditions and actual operation characteristics of the primary heating system in Daqing City. According to the test schemes, the field test is carried.(2) The effect of heating source temperature fluctuations on direct-buried heating pipe thermal insulation test is studied. A method to test and calculate heat loss of heating pipes influenced by unsteady heat source is developed in this paper. Test data of three pipe sections in the primary heating network are used to calculate the heat flux outside pipe insulation with or without considering the heat source unsteady characteristics and then the relative errors between them is figured. Calculate the heat loss of one pipe running with steady heat source, and take this as a standard to compare the calculation results of considering and ignoring heat source temperature when running with unsteady heat source, thus verify the correctness of the method developed in this paper.(3) The heat loss of all pipes is calculated with or without considering the heat source unsteady characteristics, and evaluate the insulation situation by national standard respectively. The evaluation results of two methods are compared.(4) This study summarizes the existing heating pipe insulation situation evaluation methods, and analyze the application scope of them. Then comparative studies are carried out through heat transfer calculation on the heat loss of equal thermal insulation condition pipes laid overhead and direct-buried. The influence of running months, pipe diameter, buried depth and supply water temperature is analyzed, and the orthogonal analysis method is used to find out the main influential factor. The heat loss of both overhead and buried pipes on various operation conditions is calculated, and the suggestion on the allowable maximum heat loss of buried pipe is given.