Computer simulation of Maxwell demon and Feynman's ratchet and pawl system

Abstract

of thesis entitled COMPUTER SIMULATION OF MAXWELL DEMON AND FEYNMAN’S RATCHET AND PAWL SYSTEM submitted by Jianzhou ZHENG for the degree of Doctor of Philosophy at The University of Hong Kong in September 2009 In this thesis, a simplified trap-door based Maxwell demon and two designs of ratchet and pawl systems are introduced and simulated to examine detailed behavior of these systems. Firstly, a simplified model of trap-door based demon was introduced, and molecular dynamics calculations were carried out to evaluate detailed behavior of such a system. Results show that no temperature differentiation can happen when the trap door and the chamber particles are in thermal equilibrium. When the trap door was cooled down by placing it into a chamber with low temperature, the trap-door creates a temperature and density gradient between the two chambers of the box. The cooled trap door created more readily a density gradient than that of temperature. Secondly, two designs of ratchet and pawl systems were introduced. Molecular dynamics simulations for both particle driven and Langevin force driven systems were carried out to examine the detailed behavior of these systems. The ratchet was found to rotate as designed when the temperature of the pawl chamber was lower than the ratchet side. Several parameters and configurations were tested. The results showed that there was a maximum efficiency when optimum load was applied. The correlation between ratchet and environment of particle driven system was much lower than that of Langevin force driven system. After comparing results between different designs of ratchet, the efficiency of the ratchet was found to be greatly depended on the design. COMPUTER SIMULATION OF MAXWELL DEMON AND FEYNMAN’S RATCHET AND PAWL SYSTEM