Experimental determination of thermal conductivity and diffusivity using a partially heated surface method without heat flux transducer

Abstract

This study presents a new experimental technique to obtain the thermal conductivity of conductor and non-conductor materials of small dimensions. As usual, the thermal conductivity estimation involves a thermal model with a known heat flux input. The main contribution of this study is the use of inverse techniques to estimate the heat flux input instead of measuring with heat transducers. It can be observed that the presence of transducers represents an additional experimental limitation for small samples. Besides the experimental difficulties, the smaller the transducer dimensions the more difficult it is to obtain the calibration curves due to the low sensitivity. The procedure proposed here is based on the following steps: (i) development of experimental apparatus and thermal model considering a heat flux input in part of the sample surface while the remaining surfaces are kept isolated; (ii) estimation of a dimensionless heat flux, Ф(t), proportional to the heat flux input using inverse techniques; (iii) estimation of thermal diffusivity; (iv) comparison between this heat flux, Ф(t), with the total heat flux supplied by the heating element P/S₁ to estimate the thermal conductivity of the sample.

Keywords:

• inverse problem
• dynamic observers
• heat flux estimation
• thermal properties identification
• thermal diffusivity
• thermal conductivity

Acknowledgements

The authors thank CAPES, Fapemig and CNPq.