Development And Experimental Study Of The Device For Measuring Apparent Thermal Conductivity Of Multilayer Insulation Materials

Thermal insulation material can reduce heat transfer and is used widely in the field of cryogenic liquid storage and transportation.Multilayer insulation(MLI),invented in1951 by the Swedish scholars Peterson,is known as"super insulation"for its low thermal conductivity under high vacuum.Apparent thermal conductivity is one of the important indexes of MLI insulation performance,including solid conductivity,gas conductivity and thermal radiation.The apparent thermal conductivity is related to material,vacuum,layer number,layer density,boundary temperature and other factors.In order to evaluate the insulation performance of MLI materials and unify evaluation criteria,the following research work was carried out in this paper:1.A test platform is designed and built.According to GB/T31480-2015,with liquid nitrogen as working fluid,a test platform is built.The cold boundary temperature can be adjusted from 77.35 K to 91 K.The hot boundary temperature can be controlled from–50?to 140?.the vacuum can be adjusted from 10^-5pa to 10⁵Pa.2.The control system independent of test system is designed.The test data can be automatically collected based on the LabVIEW.Logical control adopts PLC control.3.Empty cylinder experiment is carried out and the apparent thermal conductivity of a MLI material is measured.The availability of the test platform is verified by the empty cylinder experiment.The apparent thermal conductivity of a MLI material under different vacuum is obtained,which is consistent with the curve in the literature,proving that the test platform can be used to characterize the insulation performance of MLI materials.4.A complete set of test specifications for insulation performance of MLI materials is given.The basic parameters of the test platform are determined.The normal operation of mechanical system,control system and test system are verified.The working conditions including gas type,vacuum and boundary temperature can be controlled and analyzed.The test steps and specifications are formulated.