管道泡沫保温层导热系数测定

The Determination of Heat Conductivity of the Foam Insulating Coating for Pipes

保温材料导热系数是衡量管道保温性能的重要参数之一,也是保温管道设计和管理中必不可少的基础数据。目前测定保温层导热系数的方法是取样快速导热系数测定仪测定,该方法会破坏保温材料测试表面的微观结构,因测试探头与试件之间存在接触热阻,测试结果误差较大,而且由于保温预制管发泡均匀程度不同,取样测试结果不能全面反映成型保温管道的整体保温效果。泡沫保温层整体导热系数测定法可以在不破坏保温层的情况下得到保温层整体平均导热系数,实验方法有两种:稳态法和瞬态法。由于稳态法有许多技术问题不好解决,故采用瞬态法,即静置温降法,具体方法是让温度恒定的液体在实验管段内流动,当温度场达到基本稳定时,停止流动,测量管内液体温度和夹克内壁温度,计算保温层整体导热系数。根据4次实验求得的整体导热系数平均值为0.039W/(m·℃),其值更接近部颁标准0.035W/(m·℃)。

The heat conductivity of insulating material is one of the important parameters for the determination of insulating performance for pipeline, and is the indispensable basic data for design and management of insulated pipeline. The method of determining heat conductivity used at present is sampling and measuring by means of fast heat conductivity meter. This method has such disadvantages as destruction of the microstructure of the coating,great error due to the contact heat resistance between probe and specimen,and great difference between sample result and the actual insulating effect of the whole pipeline because of foam non-uniformity of the prefabricated insulated pipe. There are two test methods,namely steady state method and transient state method, are available for determining the mean heat conductivity of the insulating coating without any destruction. Because many technical problems exist in steady state method, transient state method,i. e. stationary-cool down method is used. The following is the procedure:keep the thermostated liquid flow in the test pipes until stable temperature field is realized, measure the temperature of the liquid and the inner wall of jacket,and calculate heat conductivity. According to the four tests,the average value of heat conductivity is 0.039 W/(m·℃), very close to the ministrial standard value of 0.035 W/(m·℃).