Evaluation of measuring thermal conductivity of isotropic and anisotropic thermally insulating materials by transient pl
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Evaluation of measuring thermal conductivity of isotropic and anisotropic thermally insulating materials by transient plane source (Hot Disk) technique Artem A. Trofimov1 · Jerald Atchley2 · Som S. Shrestha2 · André O. Desjarlais2 · Hsin Wang1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The transient plane source (TPS) technique, also referred as the Hot Disk method, has been widely used due to its ability to measure the thermal properties of an extensive range of materials (solids, liquids, and powder). Recently, it has been recognized that typical Hot Disk sensors can influence TPS results of thermally insulating materials and lead to an overestimation of thermal conductivity. Although improvements have been proposed, they have not yet been implemented in the commercial TPS, leaving researchers with non-standardized modifications or options provided by a commercial Hot Disk apparatus. An empirical study of thermally insulating materials such as extruded polystyrene (XPS) and aerogel blanket is conducted in order to address the factors that affect the reliability of thermal conductivity k obtained using the commercial TPS apparatus. Sensor size, input power, duration of the measurements, applied pressure, and, in the case of anisotropic materials, heat capacity are investigated, and the results are compared with those using a Heat Flow Meter apparatus. The effect of sensor size on the k value is ascribed to heat loss through connecting leads and is more pronounced in smaller sensors and in materials with lower k values. In the case of XPS and aerogel, the effect becomes minimal for sensors with a radius r ≥ 6.4 mm. The low input power yields a high scattering of the results and should be avoided. Applied contact pressure and the tested region of the specimen play an important role in experiments with low-density fibrous materials due to the large percentage of heat being transferred by radiation and the heterogeneous nature of the samples, respectively. Additionally, the sensitivity of anisotropic measurements to the value of the material’s volumetric heat capacity (ρCp) is shown, emphasizing the need for the precise determination. Keywords Transient plane source (TPS) · Hot Disk sensor · Thermally insulating material · Aerogel · Thermal conductivity · Anisotropic material · Specific heat capacity
1 Introduction The development of modern engineering applications, such as heat flow management in the semiconductor industry, insulation for space shuttles, and home insulation using various building materials, is quickly increasing the need for novel thermally insulating materials with a ultra-low * Hsin Wang [email protected] 1
Materials Science and Technology Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37830, USA
Energy and Transportation Science Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37830, USA
2
thermal conductivity due to demands for energy efficiency and energy conservation. Traditional stead
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