Analysis of the hot-disk technique applied to low-density insulating materials

The measurement error of the TPS method using sensors with common design where the dielectric insulation layer thickness is >30 μm can be significant for thermal insulation materials, especially those with k < 0.05 W m-1 K-1.

“More recently, it has been noticed that the measurement error of the TPS method using sensors with common design where the dielectric (e.g., polyimide and mica) electrical insulation layer thickness is &gt;30 µm can be significant for TI materials, especially those with k &lt; 0.05 W m 1 K -1 . 16-18”

The hot disk TPS method suffers from substantial systematic errors when applied to low-k thermal insulation materials.

“Despite its well-established reliability for a wide variety of common materials, the hot disk TPS method is also known to suffer from a substantial systematic errors when applied to lowk thermal insulation materials, because of the discrepancies between the idealized model used for data analysis and the actual heat transfer process.”

Even with residuals <1 mK by the additional optimization, the resulting k_app can be substantially higher than the true value of k_s, especially for TI materials.

“Even with the residuals &lt; 1 mK by this additional optimization, 17 the resulting k app can be substantially higher than the true value of k s, especially for TI materials.”

There is a lack of a clear understanding and quantitatively useful solution to the problem of relating the measurement error for thermal insulation materials to the sensor parameters in a definitive way.

“Although it was mentioned that the finite thermal mass of the sensor can lead to error in some lowk materials, 17, 20 there is still a lack of a clear understanding and quantitatively useful solution to this problem which relates the measurement error for TI materials to the sensor parameters in a definitive way.”

Several publications investigated the accuracy and performance of commercial TPS devices based on numerical simulations to study the effect of sensors on TPS measurement for bulk or thin film and the error due to thermal radiation in semitransparent sample.

“In the latter aspect, several publications investigated the accuracy and performance of commercial TPS devices based on numerical simulations to study the effect of the sensors on the TPS measurement for bulk or thin film 20, 27-31 and the error due to thermal radiation in semitransparent sample. 17, 33”