Exceptions to Fourier's Law at the Macroscale

For the past two centuries, heat conduction within materials has been widely described as diffusion according to Fourier's law, with exceptions only observed at the nanoscale. However, this study aims to challenge the prevailing understanding of heat conduction by investigating its limitations at the macroscale. To achieve this, a home-built VacuThermoStretch IR System is utilized to conduct steady and pulse heating experiments. The results reveal anomalous temperature distributions and thermal energy propagation that cannot be explained by the classical Fourier's Law. These anomalies are observed across a range of materials, including slow amorphous polymer glass, crosslinked polymer rubber, and semicrystalline polymers, as well as fast metals. This suggests new strategies of heat transfer design.