Investigation On Thermodynamic Performance Of Microscopic Heat Engines And Refrigerators Of Three And Five States

In recent years, there have been many problems about particle transport inbiological and physical experiments. When the particle transport involves thermalphenomenon, the studies on heat engines emerge at the right moment. There aremany determining factors of system environment, including excitation mechanism,thermal fluctuation, etc. Brownian heat engine, quantum heat engine, laser heatengine and thermionic heat engine have been studied by many scholars. Heat enginessuch as Brownian heat engine, molecular pump, and molecular channel, etc,influenced by thermal fluctuation mainly come from biological systems, while thereare many heat engines controlled by electronic transport, for example quantum dotheat engine. The theory of Brownian heat engine is derived from Fokker-Planckequation, Langevin equation, and stochastic thermodynamics combined with thecharacteristics of each kind of particle. Compared with the traditional heat engine,Brownian heat engines are actuated by temperature difference, chemical potentialdifference and barriers associated with time and can overcome load to generate workby the particles in the engines moving in one direction. The issue of microscopicthree and five state’ models involving thermal fluctuation is one subject of Brownianheat engine.In this paper, we investigate the thermodynamic properties of microscopic threeand five states engine or refrigerator, and study how the irreversible factors affect theperformance of the engine and how to improve the efficiency or power of heatengines.In chapter I, we mainly introduce the study background, research status and partof the primitive thesis of microscopic three and five states models.In chapter II, we investigate the microscopic three and five states refrigerator.The transition probability of the models conforms to the detailed balance condition.Based on master equation, the analytical expressions for the coefficient ofperformance and the cooling rate of the microscopic refrigerators are deduced. Thecurve of the cooling rate versus the coefficient of performance is obtained through the method of numerical analysis and we investigated the performancecharacteristics of these two kind models. It is shown that the maximum cooling rateand the corresponding coefficient of performance of the three and five statesrefrigerator increase monotonously with the temperature ratio of the reservoirs. Themaximum cooling rate of three states refrigerator is larger than that of the five statesrefrigerator, but the corresponding coefficient of performance of three statesrefrigerator is smaller than that of the five states refrigerator.In chapter III, we have builted the five states irreversible model. Based onmaster equation, the analytical expressions for the power and the efficiency of themicroscopic heat engine are deduced. The curve of the power versus the efficiency isobtained through the method of numerical analysis and we investigated performancecharacteristics of this kind model. It is shown that the curve of the power versusefficiency is a close one.