真空复合保温预制直埋管散热损失实验研究

Experimental Research on Heat Loss of Prefabricated Directly Buried Pipe with Vacuum Composite Insulation

针对真空复合保温预制直埋管(以下简称真空复合保温管,工作管内直径x壁厚为42.0 mm×4.4 mm,外护管外直径x壁厚为73.0 mm×3.4 mm,纳米气凝胶毡厚度为6 mm,真空层厚度为1.7 mm)展开散热损失实验研究。以导热油为循环介质,分别采用热流计法、表面温度法、热平衡法进行测试。对3种方法的测试计算结果进行对比,分析存在差异的成因。真空复合保温管的散热损失随导热油进口设定温度的增大而增大。导热油进口设定温度一定时,真空复合保温管的散热损失随真空层绝对压力的增大而增大。真空层绝对压力为2.0 kPa时,真空复合保温管的散热损失最小。真空层绝对压力为12.0、22.0、101.3 kPa时,真空复合保温管的散热损失接近。在保温材料种类、厚度、安装方式一定的前提下,真空层绝对压力对获得更低的散热损失发挥着决定性作用。热流计法的测试结果与表面温度法的计算结果接近,热平衡法的计算结果与前二者的差别较大。该实验宜采用热流计法、表面温度法。

Experimental research on heat loss of prefabricated directly buried pipe with vacuum composite insulation(hereinafter referred to as the vacuum composite insulation pipe,the inner diameter × wall thickness of the working tube is 42.0 mm × 4.4 mm,the outer diameter × wall thickness of the outer protective tube is 73.0 mm × 3.4 mm,the thickness of the nano aerogel felt is 6 mm,and the thickness of the vacuum layer is 1.7 mm)is carried out.With heat transfer oil as the circulating medium,the heat flow meter method,surface temperature method and heat balance method are used for testing.The test and calculation results of the three methods are compared,and the reasons for the differences are analyzed.The heat loss of the vacuum composite insulation pipe increases with the increase of the set temperature of the heat transfer oil inlet.When the set temperature of the heat transfer oil inlet is constant,the heat loss of the vacuum composite insulation pipe increases with the increase of the absolute pressure of the vacuum layer.When the absolute pressure of the vacum layer is 2.0 kPa,the heat loss of the vacuum composite insulation pipe is the smallest.When the absolute pressures of the vacuum layer are 12.0,22.0 and 101.3 kPa respectively,the heat loss of the vacum composite insulation pipe is close.Under the premise of certain type,thickness and installation method of insulation materials,the absolute pressure of the vacuum layer plays a decisive role in obtaining lower heat loss.The test result of the heat flow meter method is closer to the calculation result of the surface temperature method,and the calculation result of the heat balance method is quite different from those of the former two methods.The experiment should adopt the heat flow meter method and the surface temperature method.