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Updated: Aug 6, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Hidden heat transfer in equilibrium states implies directed motion in nonequilibrium states
Teruhisa S Komatsu1, Naoko Nakagawa
1Department of Physics, Gakushuin University, Mejiro, Tokyo 171-8588, Japan.
Abstract:
We study a class of heat engines including Feynman's ratchet, which exhibits a directed motion of a particle in nonequilibrium steady states maintained by two heat baths. We measure heat transfer from each heat bath separately, and average them using a careful procedure that reveals the nature of the heat transfer associated with directed steps of the particle. Remarkably we find that steps are associated with nonvanishing heat transfer even in equilibrium, and there is a quantitative relation between this hidden heat transfer and the directed motion of the particle. This relation is clearly understood in terms of the principle of heat transfer enhancement, which is expected to apply to a large class of highly nonequilibrium systems.
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