Performance Study Of Heat Engines Under Feedback Control Or Local Equilibrium

Quantum heat engines produce work using quantum matter as their working substance.Because of the quantum nature of the working substance,quantum heat engines have many exotic properties.For example,under some conditions,quantum heat engines can surpass the maximum limit on the amount of work done by a classical thermodynamic cycle and also surpass the efficiency of a classical Carnot engine cycle.Quantum heat engines offer good model systems to study the relation between thermodynamics and quantum mechanics.Meanwhile,they can highlight the difference between classical and quantum thermodynamic systems,and help us understand the quantum-classical transition problem of thermodynamic processes.In this paper,some heat engines are proposed.We drive the expressions of the related thermodynamic parameters,then analyze their thermodynamic properties and optimal performance.Finally,we got some conclusions.The detailed contents of the paper are listed as follows:In chapter 1,we introduce the research backgrounds about quantum heat engines.In chapter 2,we introduce some knowledge of physics and computing method.In chapter 3,we propose an Otto heat engine that undergoes processes involving a special class of feedback and analyze theoretically its response.We use stochastic thermodynamics to determine the performance characteristics of the heat engine and indicate the possibility that its maximum efficiency can surpass the Carnot value.The analytical expression for efficiency at maximum power,including the effects resulting from feedback,reduces to that previously derived based on an engine without feedback.In chapter 4,we analyze a general model of quantum heat engine operating a cycle of two adiabatic and two heat-transfer processes,where the working substance is composed of a harmonic or spin system.We use the quantum master equation for a system to describe heat transfer current during a thermodynamic process in contact with a heat reservoir.We apply the local equilibrium description to the heat engine cycle working in the linear response regime and derive the expressions of the efficiency and the power.By analyzing the entropy production rate along a single cycle,we identify the thermodynamic flux and force which a linear relation connects.From maximizing the power output,we find that such heat engines satisfy the tight-coupling condition and the efficiency at maximum power agrees with the Curzon-Alhorn efficiency known as the upper bound in the linear response regime.In chapter 5,we mainly give the conclusion of this paper and discuss the shortcomings in this paper.Finally,we give the further research direction.