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Updated: Jul 2, 2025

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow
Published on: April 30, 2018
How heat propagates in liquid 3He
Kamran Behnia1, Kostya Trachenko2
1Laboratoire de Physique et d'Étude des Matériaux, (ESPCI - CNRS - Sorbonne Université), PSL Research University, Paris, France. Kamran.Behnia@espci.fr.
Abstract:
In Landau's Fermi liquid picture, transport is governed by scattering between quasi-particles. The normal liquid 3He conforms to this picture but only at very low temperature. Here, we show that the deviation from the standard behavior is concomitant with the fermion-fermion scattering time falling below the Planckian time, and the thermal diffusivity of this quantum liquid is bounded by a minimum set by fundamental physical constants and observed in classical liquids. This points to collective excitations (a sound mode) as carriers of heat. We propose that this mode has a wavevector of 2kF and a mean free path equal to the de Broglie thermal length. This would provide an additional conducting channel with a T 1/2 temperature dependence, matching what is observed by experiments. The experimental data from 0.007 K to 3 K can be accounted for, with a margin of 10%, if thermal conductivity is the sum of two contributions: one by quasi-particles (varying as the inverse of temperature) and another by sound (following the square root of temperature).
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