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The hot disk transient plane source (TPS) method is a widely used standardtechnique (ISO 22007-2) for the characterization of thermal properties ofmaterials, especially the thermal conductivity, k. Despite its well-establishedreliability for a wide variety of common materials, the hot disk TPS method isalso known to suffer from a substantial systematic errors when applied to low-kthermal insulation materials. Here, we present a combined numerical andexperimental study on the influence of the geometry of hot disk sensor onmeasured value of low-k materials. We demonstrate that the error is stronglyaffected by the finite thickness and thermal mass of the sensor's insulationlayer was well as the corresponding increase of the effective heater sizebeyond the radius of the embedded metal heater itself. We also numericallyinvestigate the dependence of the error on the sample thermal properties,confirming that the errors are worse in low-k samples. A simple correctionfunction is also provided, which converts the apparent (erroneous) result froma standard hot disk TPS measurement to a more accurate value. A standardpolyimide sensor was also optimized using both wet and dry etching to providemore accurate measurement directly. Experimentally corrected value of k forAirloy x56 aerogel and a commercial silica aerogel using the numericalcorrection factor derived based on the standard TPS sensor is in excellentagreement with the directly measured value from the TPS sensor using theoptimized polyimide sensor. Both of these methods can reduce the errors to lessthan 4% as compared to around 40% error of overestimation from raw valuesmeasured with the pristine sensor. Such results show that both the numericalcorrection to a pristine senor or an optimized sensor are capable of providinghighly accurate value of thermal conductivity for such materials.

Analysis and Improvement of the Hot Disk Transient Plane Source Method for Low Thermal Conductivity Materials