Optimal Analysis Of Irrevisible Quantum Theymodynamics

Quantum thermodynamics is a new hotspot of the modern thermodynamics. It is mainly used to investigate the performance of thermodynamics cycles which use quantum systems or quantum gases as working substance. Since the 1980s, the investigation on the performance of quantum thermodynamics as well as classical thermodynamics has attractted a great deal of attention and led to many meaningful results. It has important theoretical significance for the study of thermodynamics cycles in low temperature environments, especially for the study of refrigeration cycles.Quantum systems or quantum gases, as the working substance of the quantum thermodyamic cycles, are usually applied to investigate the performance characteristics of various quantum thermodynamic cycles. In the present thsis, the performance of various thermodynamic cycles working with quantum gases are discussed in detail.In chapterâ…¡, the production, development and the present states of quantum thermodynamics are discussed briefly.In chapterâ…¢, the analysis of the performance of some quantum gas thermodynamics cycles is performed. By using the equations of the states of an ideal quantum gas and thermodynamic relations, the general expressions of some important thermodynamic quantities such as the interal energy, entropy, heat capacity at constant volume, and heat capacity at constant pressure are derived. Moreover, the performance parameters including the work output and efficiency of an irreversible Carnot cycle, Stifling cycle and Brayton cycle are analyzed. The influence of the quantum gas degeneracy on the performance of quantum gas cycles is also discussed. It is obtained that the work output and efficiency of irreversible Otto cycle and Brayton cycle using Bose gas as working substance are lager than those of corresponding cylces using classical gas as working substance; however, the results obtained in the cycles using Fermi gas as working substance are intuitively different from those in the cyles mentioned above.The performances of a regenerative irreversible Otto cycle and Stifling cycle are studied in chaprerâ…£. Based on the equations of the states of an ideal quantum gas, the regenerative characteristics of quantum gas Otto refrigeration cycle and Stirling engine cycle are analyzed. It illustrates that the quantum gas Stirling engine doesn't possess the condition of perfect regeneration. Its efficiency is smaller than classical gas regenerative Stirling engine. It's pointed out in this chapter that the influence of the ratio of volume on the performance of this cycle can't be negelected. In addtion, Quantum gas Otto cycle may possess the condition of perfect regeneration. The coefficient of performance(COP) of an irreversible quantum gas Otto cycle is always smaller than the COP of a classical gas Otto cycle. The refrigeration quantity of an irreversible Bose gas regenerative Otto cycle is always larger than that of the classical gas regenerative Otto cycle, but the refrigeration quantity of a Fermi gas Otto cycle is always smaller than that of the classical gas regenerative Otto cycle.