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| Study on Measuring Thermal Conductivity of Materials at High Temperature by Guarded-hot-plate |
| LIU Ye1,2,ZHANG Jin-tao2,WANG Jin-ku2,WANG Ming-kai3,SUN Jian1,XU Hong-wei1 |
1. College of Mechanical and Electrical Engineering,China Jiliang University, Hangzhou, Zhejiang 310018, China
2. Division of Thermophysics and Process Measurements, National Institute of Metrology, Beijing 100029, China
3. Beijing Revitalization Institute of Measurement and Test, Beijing 100077, China |
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Abstract Guarded-hot-plate (GHP) method plays the primary procedure for measurements of the thermal conductivity of insulators. The method has important applications in the fields of new material explorations and industrial energy savings. The National Institute of Metrology(NIM) has newly developed a single sample high temperature protection hot plate method device, the design working temperature ranges from room temperature to 500 ℃, and the thermal conductivity measurement range is 0.02～0.5W/(m·K). We developed a new controlling scheme that effectively suppressed the thermal oscillation caused by the thermal inertia of the big equipment ensemble. The temperature of each component of the device is continuously stablized within 0.005℃ in a period up to 2 hours. The heat leak from the upper guarded plate is a specific question with the GHP devices of the single sample type. The phenomenon become serious with increasing temperatures. We studied the temperature compensation procedure that effectively suppresses the heat leak through the upper guarded plate. We applied the device measuring the standard reference material for thermal conductivity of SRM1450d of NIST, in the sample average temperature from 30℃ to 70℃, the relative deviation from the reference values falls in the range of 0.2%～1.9% with the measurement uncertainty of 1.2% (k=2). We used the device measuring the thermal conductivity of cast polymethyl methalcylate, and observed the relative deviation of -0.8% to -1.5% from the publication data by the PTB. We then measured the thermal conductivity of mineral wool in the temperatures ranging from 40~ 400℃ with the measurement uncertainty of 4.7% (k=2 ).
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Received: 21 August 2022
Published: 25 June 2023
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2023, Vol. 44 
