Investigation On The Performance Of Two Typical Regenerative Thermodynamic Cycles

Finite-time thermodynamics is a new important branch of the modern thermodynamics. It is mainly used to investigate the regulation of energy and entropy flows of non-equilibrium systems in finite time. It has been extensively applied to many fields such as national defense, industrial and agricultural production, energy technology, chemical engineering and thermal economics. It has important theoretical significance for ones to open up new energies, develop new technologies, utilize energies efficiently, improve ecological environments, protect natural resources and exploit cross-subjects.Finite-time thermodynamics has deal: with many research fields. Specially, in the investigation of optimizing the performance of thermodynamic cycles, a lot of important achievements have been obtained. In the present thesis, the performance of two typical regenerative thermodynami; cycles is investigated on the basis of previous achievements. It has not only important theoretical but also practical significance. The regenerative thermodynamic cycles are a class of the typical thermodynamic cycles. The Ericsson and Stirling cycles are two of the important regenerative thermodynamic cycles. The regenerative characteristics, performance parameters and optimal theories of the Encsson and Stirling cycles using respectively a ferroelectric material, a ferromagnetic material, a classical gas, a quantum gas and a spin system as the working substance are researched for different operating conditions. The influence of several factors such as non-perfect regeneration, finite-rate heat transfer, internal irreversibility of the working substance, heat leak loss between the heat reservoirs, heat transfer laws and the quantum degeneracy on the performance of thermodynamic cycles is studied. Some novel results are obtained, which will not only provide some theoretical bases for the optimal design and performance improvement of real thermodynamic cyclic equipments such as ferroelectric refrigerators, magnetic refrigerators and gas heat engines but also promote the development of new fields such as gas refrigerators for ultra-low temperatureapplications, molecule refrigerators and laser refrigeration technologies. In the present thesis, the performance of two typical regenerative thermodynamic cycles will be investigated by the following chapters.In chapter I, the production and development, theoretical characteristics and the present states of the study on finite time thermodynamics are introduced abstractly.In chapter II, the regenerative and performance characteristics of the regenerative ferroelectric refrigeration cycles are investigated. By using the expressions of the electrical polarization of ferroelectric materials and thermodynamic fundamental equations and relations, the general expressions of some important thermodynamic parameters such as the internal energy, entropy, heat capacity at constant polarization and heat capacity at electrical field intensity are derived. Moreover, the regenerative characteristics of the ferroelectric Stirling and Ericsson refrigeration cycles are analyzed, based on the common criterion that a thermodynamic cycle may possess the condition of perfect regeneration. It is illustrated that a ferroelectric Stirling refrigeration cycle may possess the condition of perfect regeneration and its coefficient of performance (COP) is equal to that of a Carnot refrigeration cycle, while a ferroelectric Ericsson refrigeration cycle does not possess the condition of perfect regeneration so that its COP is smaller than that of a Carnot refrigeration cycle. Again, the COP of a ferroelectric Ericsson refrigeration cycle is calculated in detail and the analytic expressions of the COP for some special dielectric materials which obey Curie law, Curie-Weiss law and other laws are obtained.In chapter III, the optimal performance of the regenerative ferromagnetic refrigeration cycles is studied. By using the general expression of the magnetization of a ferromagnetic material, the thermodynamic properties of t...