Research On Three Types Of Heat Engines Based On Nonequilibrium Statistical Mechanics

Understanding the statistical physics of nonequilibrium systems is particularly challenging because of their nonequilibrium charecteristics.The source of nonequilibrium effects has various origins,many of which can be summarized into a common form in the state space.This thesis investigates three types of heat engines that can be casted within the framework of nonequilibrium thermodyanmics,with emphasis both on the law of thermodynamics and engine performance.Firstly,we study the peformance of heat engines coupled with squeezed thermal bath in the framework of quantum thermodynamics.Quantum resources impose peculiar properties on quantum heat engines,such as work extraction from a single heat reservoir and the exceeding of Carnot efficiency.We investigate the finite time performance of reciprocating quantum Otto heat engine coupled to squeezed hot reservoir.To fully exploit the quantum availability provided by the squeezed bath,an optimal frequency protocol in the work extraction stroke is explicitly proposed.Thermodynamic analysis shows that for a wide range of squeezing parameters,efficiency at maximum power exceeds the generalized Curzon–Ahlborn efficiency defined by the effective temperature of the squeezed bath.As the second type of heat engines,we consider the paradigmatic model of Maxwell demon in the theoretical framework of stochastic thermodynamics.Both single-temperature and two-temperature cases are considered.In the single-temperature case,we study the optimal work extraction protocol for a Brownian particle described by generalized Langevin dynamics from a single reservoir with the aid of position measurement.In the overdamped situation,we show that memory effects typically reduce the extracted work,and full information-work conversion can only be achieved by manipulating both the stiffness and center of the potential quasistatically.In the two-temperature case,we consider a colloidal Brownian particle trapped in an elliptical potential well and simultaneously coupled to two heat baths at different temperatures acting along perpendicular directions.Measuring the position of the particle and implementing the discrete feedback control on the potential's position and rotation angle,we are able to extract work.It was confirmed that the output power increase with the frequency of measurements,which is consistent with previous experimental results.Finally,we present numerical simulation results of thermally induced gas flow in the gap between a ratchet surface and a moving wall.The presence of specular wall breaks the symmetry of the velocity distribution of reflected molecules,resulting in highly nonequilibrium flows that produce shear force acting on the moving wall.In this sense,it can be regarded as a heat engine converting heat into work.To simulate this engine,we propose a particle ellipsoidal statistical Fokker-Planck(ESFP)algorithm.In this algorithm,the evolution of individual molecular velocity is modeled as a continuous stochastic process,and the Langevin dynamics is implemented in a particle Monto Carlo manner.In the transition regime,the mechanical power output and thermodynamic efficiency are calculated for various moving speeds of the moving wall and inclination angles of the specular surface.The dependence of efficiency of the inclination angle is identified,and the optimal efficiency is found to be not much different from that in the free molecular regime.