Thermal Conductivity Measurements Of Solid Materials At Low Temperatures Based On A 4k G-M Cryocooler

Thermal conductivity is one of the basic thermal properties of material. With the development and wide application of low-temperature technology, superconducting technology and space technology in engineering fields, low-temperature thermal conductivity measurement is not only an important experimental method of modern thermophysics, but also able to provide the necessary reference data for engineering application.Even for the same kind of solid materials, thermal conductivity still depends on the temperature, composition, impurities, structural defects and other factors. Furthermore, with the advance in technology, more and more new materials are being created whose thermal conductivities are still unknown, in particular at low temperatures. In addition, some differences still exsit for several materials among different literatures. In order to fill the blank of low-temperature thermal properties parameters database and provide reliable technical support for scientific research and engineering, research on the thermal conductivity measurements of solid materials at low temperature has important practical significance.In the present study, a thermal conductivity measurement experiment system for solid materials from 2.5K to 300K was desired according to the one-dimensional steady-state Fourier heat conduction law by using a 1W@4.2K two-stage G-M refrigerator as the cold source. The main work of this paper is summarized below:1) Accordding to the comparison and analysis on the previous study about low-temperature thermal conductivity measurement of solid materials, an experimental apparatus was desired and established for measuring the thermal conductivity of solid materials at low temperatures, specifically including experimental system, vacuum chamber structure, sample frame structure, data acquisition systems,etc.2) Through many practices and summarization, the experimental operations applied for low temperature measurement and high temperature measurement were both proposed; 3) Different data processing methods were analyzed and discussed. Error analysis and heat leakage analysis were also done to ensure the measurement results to be accurate and reliable;4) Several measurements were done on different materials. Validation measurements on 304-stainless steel were done first to verify the reliability of this experimental apparatus, measurement method and data processing methods. And then, the thermal conductivities of several different materials were measured, and their thermal conductivity data in the corresponding measuring temperature range were obtained;5) Based on the measurement data, an equivalent model was proposed to predict the thermal conductivity of epoxy superconducting wire composite, and the temperature distribution of 304-stainless steel was predict by numerical calculation, the impact of the two thermometer holes of sample on its internal one-dimensional temperature distribution were then discussed.According to the experiments and research results, it is found that the accurate and reliable low-temperature thermal conductivity of solid materials could be obtained by this experiment apparatus which has easy maneuverability and relatively low cost, and it is adequate to meet the needs of engineering applications.