2008/05/31 by Z. C. Tu, Z C Tu · 7 citations
Engineering · Physics and Astronomy · #Advanced Thermodynamic Systems and Engines #Advanced Thermodynamics and Statistical Mechanics #Heat engine #Heat exchanger #Kinetic energy #Maximum power principle #Maximum temperature #Power (physics) #Ratchet #Thermal #Thermal efficiency #cond-mat.stat-mech #stochastic dynamics and bifurcation
paper · pdf · doi:10.1088/1751-8113/41/31/312003
published as J. Phys. A: Math. Theor. 41, 312003 (2008) · 7 pages, 3 figures; correct some errors
openalex publication_date 2008/07/02 · arxiv created 2008/07/03 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The maximum power of Feynman's ratchet as a heat engine and the corresponding efficiency (η ∗ ) are investigated by optimizing both the internal parameter and the external load. When a perfect ratchet device (no heat exchange between the ratchet and the pawl via kinetic energy) works between two thermal baths at temperatures T 1 > T 2 , its efficiency at maximum power is found to be η ∗ = η 2 C /[η C − (1 − η C )ln(1 − η C )], where η C ≡ 1 − T 2 / T 1 . This efficiency is slightly higher than the value obtained by Curzon and Ahlborn (1975 Am. J. Phys. 43 22) for macroscopic heat engines. It is also slightly larger than the result η SS ≡ 2η C /(4 − η C ) obtained by Schmiedl and Seifert (2008 EPL 81 20003) for stochastic heat engines working at small temperature differences, while the evident deviation between η ∗ and η SS appears at large temperature differences. For an imperfect ratchet device in which the heat exchange between the ratchet and the pawl via kinetic energy is non-vanishing, the efficiency at maximum power decreases with increase in the heat conductivity.