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

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 0.035W/(m·℃).