Study Of High-temperature Thermal Conductivity Measuring Instrument Basedon The Guarded Hot Plate Method

Precise measurement of an important parameter to measure the thermal properties of the insulation material- thermal conductivity has important practical significance for modern production. The guarded hot plate method is an international common standard measurement method and has advantage of high accuracy, good reproducibility, wide temperature range, etc. The domestic instruments can only measure the thermal conductivity of near room temperature, not thermal conductivity measuring instrument for high temperature. As the demand for insulation materials thermal conductivity at high temperatures increasingly significant, laboratory developed the first generation of high-temperature thermal conductivity measuring instrument. While the first generation of thermal conductivity measuring instrument capable of measuring thermal conductivity at high temperatures, but there are still some deficiencies in the mechanical structure, the calibration methods. Therefore, the development of second-generation high-temperature thermal conductivity measuring instrument for the development and production of insulation materials is of great significance.Based on the first generation laboratory prototype of thermal conductivity measuring instrument based on the guarded hot plate method, this study improved the original mechanical structure by Ansys finite element simulation, such as improved temperature hole, etc; used a new temperature measurement method, to realize the accurate control of temperature; and proposed calibration method for high temperature; And tested accuracy and repeatability of instrument by assessing the uncertainty thermal conductivity.The major work of this thesis is as following:1. This paper introduced the concept and the main measuring method of thermal conductivity; and briefly illustrated the current research status of thermal conductivity measuring instrument at home and abroad, and the problems of domestic thermal conductivity measuring instruments and the first generation laboratory prototype; put forward the purpose and the contents of this research.2. According to the basic principle of guarded hot plate method, the mechanical structure was designed. The main structure of thermal conductivity measuring instrument was analyzed in detail, improved the key mechanical structure using Ansys finite element simulation, including thermometer hole, electric heating wire, difference in temperature sensor, etc.3. Control circuits and software programs of thermal conductivity measuring instrument were designed, including the overall solution program of the control system, the selection and installation of sensor, the measuring and control circuit of temperature, the program design of the instrument.4. F or high temperature, a calibration method of the hot-plate power loss was proposed and established.5. The sources of thermal conductivity measurement error was summarized, tested the accuracy and repeatability of instrument by assessing the uncertainty of thermal conductivity.6. The content and work of this research were summarized, the existence shortcomings and deficiencies of the instrument were analyzed.