Exceptions to Fourier's Law at the Macroscale.

Area of Science:

• Materials Science
• Thermodynamics
• Physics

Background:

• Fourier's law, established 200 years ago, is the standard model for heat transfer analysis.
• This law is mathematically analogous to Fick's law of mass diffusion.
• Its applicability to translucent materials under specific conditions warrants re-examination.

Purpose of the Study:

• To investigate the validity of Fourier's law for heat transport in translucent materials.
• To compare model predictions with high-resolution experimental measurements.
• To identify deviations from established heat transfer models.

Main Methods:

• Experiments were conducted in a vacuum to eliminate convective heat transfer.
• Infrared-based thermometry with millikelvin temperature resolution was employed.
• Surface temperature profiles were analyzed after heat pulses and at steady state.

Main Results:

• Observed macroscale non-Gaussian tails in surface temperature profiles post-heat pulses.
• Identified macroscale anomalous hot spots in topographically rough samples at steady state.
• Validated findings using two independent surface temperature measurement techniques.

Conclusions:

• Discrepancies suggest Fourier's law is insufficient for describing heat transfer in these translucent materials.
• Internal radiation interacting with material defects generates secondary heat sources, enabling non-local heat transport.
• Findings propose novel heat management design strategies for polymers and inorganic glasses.