Research On Guarded Hot Plate Method Measure Thermal Conductivity Of Insulation Material In Low-temperature

The rationality, economy and safety in the use of insulation material is affected by the accuracy of measuring thermal conductivity of the insulation material. Coefficient of thermal conductivity measuring instruments are most based on the steady and transient method. The temperature is mostly in the region of room temperature and high temperature. With the development of low-temperature technology, there's an intensive demand for measuring thermal conductivity of the insulation material in the low-temperature. The method and principle in the measuring thermal conductivity coefficient are introduced in this paper, and a guarded hot plate apparatus which can measure the thermal conductivity of the insulation material in low-temperature according to the national standard was designed. The apparatus' s accuracy was verified by measuring the thermal conductivity of a calibrated polyurethane foam. The apparatus measured the thermal conductivity of the polyimide foam from room temperature to low temperature and the maximum relative error is calculated. The main work of this paper is as follows:1. The basic principle of the measuring thermal conductivity test are briefly introduced. The model and calculation method of hot plate method and guarded hot plate method are descried. The research progress and disadvantages of the measuring thermal conductivity coefficient instrument are reviewed.2. According to the national standard GB/T10294-2008, A guarded hot plate test-bed, the heating unit, the temperature control system, the data acquisition system, the environmental control system were designed. A monitor-control program was been developed by kingview which can acquisition, record and monitor the measured data.3. The thickness of hot plate and the edge thickness of insulation layer was optimized. The evaporation mass of liquid nitrogen in different target temperature was calculated. Conclusions of guarded hot plate testing were investigated by numerical analysis of the test-bed, and validated by experimental research.4. The thermal conductivity coefficient of polyimide foam from room temperature to low temperature was measured and curved. The relative error of test-bed was calculated.