Scientists have challenged a foundational concept in thermodynamics by uncovering an exception to Fourier’s law, which has described heat conduction in solids for two centuries. Researchers at the University of Massachusetts, Amherst, led by polymer physicist Kaikai Zheng, observed that in translucent materials such as polymers and glasses, heat doesn’t just diffuse through molecular vibrations and electron movement. They proposed that thermal radiation, a form of heat transfer typically associated with electromagnetic waves in the air, also plays a significant role within these solids.
The team conducted experiments in a vacuum chamber to eliminate air’s influence on heat dissipation and used laser pulses to heat the materials. They then measured the heat spread with sensors, temperature-sensitive coatings, and infrared cameras. The results indicated that heat transmission occurred faster than diffusion alone could account for, suggesting that radiation significantly contributes to heat flux, especially shortly after the heat pulse is applied.
This discovery implies that Fourier’s law doesn’t fully explain heat transmission in translucent materials, where structural imperfections may facilitate internal radiant heat transfer. This insight could lead to new heat management strategies in engineering applications, broadening our understanding of thermal processes in solids. The findings have been published in the journal PNAS.
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