Stability Analysis On The Performance Of An Irreversible Carnot Cycle And The Performance Characteristics Of Micro/nano Scaled Gas Cycle

In recent years, with the development of the technology and the need of practice, a new branch of course named finite-time thermodynamics developed rapidly. It is the optimal analysis for the power output and efficiency and other performance parameters of the cycle system considered the different internal and external irreversibility i.e. thermal resistance, heat leak, dissipative processes inside the working fluid etc. The main target is to decrease the irreversibility of system in the contraction of the finite-time and -size. Finite-time thermodynamics has been widely applied to many fields such as industrial and agricultural production, chemical engineering and thermal economics. It is also important in theory to open up new energies, improve ecological environments, and protect natural resources, etc.Most of the studies of the finite-time thermodynamic cycle have focused on their steady-state energetic properties. But the real heat engines are always no-steady and there exists intrinsic cycle variability in the operation of the cycle, for example, incomplete combustion of fuel, friction and other causes. It is necessary to analyze the effect of noisy perturbations on the stability of system's steady-state base on the consideration. The local stability of a general irreversible Carnot cycle considered the different irreversibility i.e. thermal resistance, heat leaks, dissipative processes inside the working fluid are studied from the chapter II to chapter IV in this thesis. The influences of the coefficient of heat transfer, the coefficient of heat leak and the internal irrversiblity degree for the cycle system are analyzed. The results are more detailed and general than the origin results. Furthermore, it is given a new guidance of theory for the design of the real thermodynamic cycle.With the rapid development of the nanotechnology, the thermodynamic relations of the micro/nano mechanical systems get much attention gradually. Many doctors have studied the thermodynamic performance of the ideal gas and quantum gas confined in a micro/nano scaled system. Furthermore, the quality of gas in the micro/nano mechanical systems is different from the quality of gas in the macro mechanical systems. For example, by using classic Maxwell-Boltzmann statistics, A. Sisman found that the expressions of the thermodynamic quantities of the ideal gases in micro/nano scaled systems are the appropriate conventional terms plus correction terms. Thus, these global thermodynamic quantities are non-additive and depend strong on the size of the containers. The thermosize effects of the ideal gas in the miro/nano scaled system make us possibly to design the miro/nano scaled heat exchange devices. A gas heat engine cycle is estabiltished innovatory by the thermosize effects in chapter V and some optimal performancesof heat engine are attained by finite-time thermodynamics. The cycle model gives some guidance of theory for the design of the micro/nano scaled heat exchange device. Furthermore, the theory model can use to measure the value of the thermosize effect. By using the reversibility of the Casimir-like effect of the ideal gas in the miro/nano scaled systems, a miro/nano scaled gas refrigerator device used to produce the temperature difference is established in chapter VI.In this thesis, the investigations of the local stability analysis of the performance of an irreversible thermodynamic cycle and the performance characteristics of a miro/nano scaled gas cycle will be presented by the following chapters.In chapter II, the local stability of an irreversible Carnot heat engine with a Newton heat transfer law are analyzed. By using the linearization and stability analysis method, the local stability of the system working in the maximum power output and maximum efficiency steady-state point are studied and the expressions of relaxation time represented the stability of system are derived base on the finite-time thermodynamic theory and the optimal performance of the irreversible Carnot heat engine. So the design of the practical heat engine must consider the optimal performance and local stability of the system. The effects of internal and external irreversibility i.e. thermal resistance, heat leak, dissipative processes inside the working fluid on the relaxation time are discussed by using plot. Especially, the stability of system working in the maximum power output is independent of the heat leak. The results put forward the higher desire for the design of the realistic heat engine.In chapter III, the local stability of an irreversible heat engine with a linear phenomenological heat transfer law are analyzed. By using the linearization and stability analysis method, the local stability of the system are studied and the expressions of relaxation time represented the stability of system are derived base on the finite-time thermodynamic theory and the optimal performance of the irreversible Carnot heat engine in the maximum power output and maximum efficiency when the state of heat engine system departs form the original steady state because of the change of the temperatures of the heat and cold reservoirs. The effects of the internal and external irreversibility i.e. thermal resistance, heat leak, dissipative processes inside the working fluid on the relaxation time are discussed by using plot. Furthermore, the local stability of system working in the maximum power output is higher than the local stability of system working in the maximum efficiency.In chapter IV, the local stability of an irreversible refrigerator with a general heat transfer law is analyzed. By using the linearization and stability analysis method, the local stability of the system are studied and the expressions of relaxation time represented the stability of system are derived base on the finite-time thermodynamic theory and the optimal performance of the irreversible refrigerator in the optimal objective function when the state of refrigerator system departs form the original steady state because of the change of the temperatures of the heat source and heat sink. The effects of the temperature ratio of heat reservoirs and thermal resistance on the relaxation time are analyzed by using plot. In particular, the temperatures working fluid decay with a different rate.In chapter V, the performance of miro/nano scaled gas heat engine cycle is studied. The Casimir-like effect in the system will become very important when the mean thermal wave length of gas atoms may be comparable with the sized of the system for the micro/nano mechanical systems. By using the Casimir-like effect of the ideal gas in the miro/nano scaled systems, a new miro/nano scaled gas heat exchange device is established. It is composed of the two isothermal and two isobaric processes. The general expressions of the power output and efficiency of miro/nano scaled gas heat engine are derived according to the first and second laws of thermodynamics. The relations between the power output and efficiency of the heat engine and external parameters are analyzed. The cycle model will provide theoretical guidance for the design of miro/nano scaled heat exchange device.In chapter VI, the performance of miro/nano scaled gas refrigerator cycle is studied. The Casimir-like effect in the system will become very important when the mean thermal wave length of gas atoms may be comparable with the sized of the system for the micro/nano mechanical systems. Furthermore, the Casimir-like effect in the micro/nano system is reversible. By using the reversibility of the Casimir-like effect of the ideal gas in the miro/nano scaled systems, a miro/nano scaled gas refrigerator device used to produce the temperature difference is established. Similarly, it is composed of the two isothermal and two isobaric processes. The general expressions of the rate of refrigeration and coefficient of performance of miro/nano scaled gas refrigerator are derived according to the first and second laws of thermodynamics. The relations between the rate of refrigeration and coefficient of performance of the refrigerator and external parameters are analyzed by the numerical calculation. The important optimal parameters for the refrigerator system are list. The result attained here provide a new way and theoretical guidance for the design ofmiro/nano scaled refrigerator device...