Research On Thermophysical Properties Measurement Of Thermal Protective Material With The Guarded Plane Source Method

This dissertation is a phasic research on"High temperature thermophysical properties measurement of thermal protective material", which is suggested by Aerospace Research Institute of Materials and Processing Technology. The objective may be categorized as follows: (1) To develop a high precision thermal properties measuring technique and a practical measuring instrument used in high temperature; (2) To further improve the high-temperature thermal properties measuring standards; (3) To tentatively set up the first high-temperature thermophysical properties database; (4) To serve the development of new style thermal protective material; (5) To serve the design of thermal protective system and the development of national defence and spaceflight.Aim at the urgent demand of high-temperature thermal properties parameters of thermal protective material, the disseration focus on the contact transient plane source methods which are adopted extensively at present after a large amount of literature researching work. But untill now, there are still several weak points and subject problems existing which limit these methods applied to high-temperature and high-precision measurement. Based on such a situation, a new style, guarded plane source method for contemporary measuring thermal conductivity, thermal diffusivity and thermal contact resistance is presented through deep research work on measuring theory, method and key technology. In present work, the ambient temperature tests from room temperature up to 1200℃on two standardized material have been performed employing this method for the purpose of establishing the data processing procedure and recognizing the experimental troubles likely to be found. Particularly, the main creative research work are as follows:1. A new style method for high-temperature contact transient-measurements of thermal properties is presented, which is aiming at the present weak points and subject problems. Deep research work has been focused on the mechanism and transient measuring technique of contact thermal resistance, and the presented guarded plane source method can realize the contemporary thermal contact resistance estimation during the thermal conductivity and thermal diffusivity measurement through combining the transient measuring techniques of thermal properties and contact thermal resistance ingeniously. In comparison with other methods, the guarded plane source method can take into account thermal contact resistance in evaluating thermophysical properties which will greatly adds accuracy to the measuring results.2. A set of apparatus is designed and developed based on the principle of the new method. The high-temperature probe act both as film heater and high-accuracy temperature sensor, and can be applyed from room temperature to 1500℃. The employed structural design of the probe and the sample holder can reduce and remedy the side border heat loss of samples, and can guarantee the adiabatic conditions needed strictly. The developed high-vacuum and high-temperature tubular blackbody furnace can not only offer steady measuring condition, but also prevent the side border convection heat loss of samples and the oxidation problem while testing at high temperature. The simutaneous measurement of the contact thermal resistance and thermal properties is realized based on the the developed measuring apparatus and the standardized material VespelTM SP1. In the present work the experiment prove not only the exactness of the new method, but also recognize the data processing procedure and experimental troubles likely to be found. The results reported show a good capacity of determining both thermal properties and contact resistance, and the relationship between the measurement accuracy of thermal properties and the contact thermal resistance is revealed. It is possible to conclude that the method can give steady estimation results in different experimental conditions, which reflect the completion of the theory model. At last, a uncertainty analysis model is established, and the uncertanty evaluation can guarantee the accuracy and comparativity.3. The parameters standardization experiment of the new method is completed between thermal conductivity range of 0.1~0.5W/mK with the standardized material VespelTM SP1. It is confirmed experimentally that the relative error of thermal properties is sensitive to different choices of experimental parameters, and the standardization work is aiming at the improvement of measurement accuracy of thermal properties using the guarded plane source method. The effects analysis of different parameters selection on measuring-accuracy is investigated experimentally, and leads us to a conclusion of parameters choosing principle. At the same time, the measurement accuracy of the guarded plane source method is further investigated based on the standardiazation experiment.