Influence Of Quantum Degeneracy Research Articles

Quantum degeneracy effect on performance of a thermoacoustic refrigeration micro-cycle

A new model consisting of two isobaric branches connected by two straight-line branches is established to investigate the thermodynamic performance of a thermoacoustic refrigeration micro-cycle. The influence of quantum degeneracy on the dimensionless cooling load R* of the cycle is analysed based on the correction equation of state of an ideal Bose gas. The relationship between the dimensionless cooling load R* and the coefficient of performance (COP) e is obtained under the condition of weak gas degeneracy. The results show that the lowest temperature of the working fluid in the thermoacoustic refrigeration micro-cycle has to be higher than the Bose--Einstein condensation temperature so that the cycle can be carried out. Under the condition of weak gas degeneracy, the dimensionless cooling load R* is a monotonically increasing function of the COP e, the initial pressure p 0 and the parameter y. Under the condition of weak gas degeneracy, the COP e is the same as that of the classical ideal gas, whereas the dimensionless cooling load R* is larger than that of the classical ideal gas. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Thermodynamic performance on a thermo-acoustic micro-cycle under the condition of weak gas degeneracy

The thermodynamic cycle of a gas parcel in the thermo-acoustic engine is referred to as a thermo-acoustic micro-cycle, which consists of two isobaric branches by two straight line branches. The influence of quantum degeneracy on the work output of the cycle is investigated based on the correction equation of state of an ideal Bose gas. The relationship between the dimensionless work output W ∗ and the efficiency η ∗ is obtained under the condition of weak gas degeneracy. Some significant results are discussed.

Influence of quantum degeneracy on the performance of a gas Stirling engine cycle

Based on the state equation of an ideal quantum gas, the regenerative loss of a Stirling engine cycle working with an ideal quantum gas is calculated. Thermal efficiency of the cycle is derived. Furthermore, under the condition of quantum degeneracy, several special thermal efficiencies are discussed. Ratios of thermal efficiencies versus the temperature ratio and volume ratio of the cycle are made. It is found that the thermal efficiency of the cycle not only depends on high and low temperatures but also on maximum and minimum volumes. In a classical gas state the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal quantum gas state the thermal efficiency of the cycle is smaller than that of the Carnot cycle. This will be significant for deeper understanding of the gas Stirling engine cycle.

Influence of quantum degeneracy and regeneration on the performance of Bose-Stirling refrigeration-cycles operated in different temperature regions

The Stirling refrigeration cycle using an ideal Bose-gas as the working substance is called the Bose-Stirling refrigeration cycle, which is different from other thermodynamic cycles such as the Carnot cycle, Ericsson cycle, Brayton cycle, Otto cycle, Diesel cycle and Atkinson cycle working with an ideal Bose gas and may be operated across the critical temperature of Bose–Einstein condensation of the Bose system. The performance of the cycle is investigated, based on the equation of state of an ideal Bose gas. The inherent regenerative losses of the cycle are considered and the coefficient of performance and the amount of refrigeration of the cycle are calculated. The results obtained here are compared with those derived from the classical Stirling refrigeration cycle, using an ideal gas as the working substance. The influence of quantum degeneracy and inherent regenerative losses on the performance of the Bose Stirling refrigeration cycle operated in different temperature regions is discussed in detail, and consequently, general performance characteristics of the cycle are revealed.

Influence of quantum degeneracy on the performance of a Stirling refrigeration cycle

Based on the equation of state of the ideal quantum gas, regenerative characteristics of the quantum Stirling refrigeration cycle is analyzed. The general expression for the coefficient of performance is derived. Under the condition of strong and weak gas degeneracy, the special expressions for the coefficient of performance are discussed. These results will be significant for the research of a Stirling refrigerator in the low temperature range.

The influence of quantum degeneracy and irreversibility on the performance of a Fermi quantum refrigeration cycle

An irreversible cycle model of the quantum refrigeration cycle using an ideal Fermi gas as the working substance is established. The cycle consists of two adiabatic and two isobaric processes and consequently may be simply referred to as the Fermi Brayton refrigeration cycle. The performance of the cycle is investigated, based on the equation of state of an ideal Fermi gas. Expressions for several important performance parameters, such as the coefficient of performance, work input and refrigeration load, are derived. The influence of the quantum degeneracy of the Fermi gas and the irreversibility in the cycle on the performance of the Fermi Brayton refrigeration cycle is analysed. The minimum pressure ratio of the cycle is determined. The optimally operating problems of the cycle and several special cases are discussed in detail. The results obtained here are general and may reveal the general performance characteristics of the Fermi Brayton refrigeration cycle.

The Influence of Quantum Degeneracy on the Performance of a Fermi Brayton Engine

The influence of quantum degeneracy on the performance of a Brayton engine using an ideal Fermi gas as the working substance is investigated, based on the theory of statistical mechanics. The general expressions of the efficiency and work output of the engine cycle are derived. The maximum work output and the corresponding efficiency are calculated. The bound of the pressure ratio of the two constant-pressure processes that the Brayton engine cycle can be operated normally is determined. Some important characteristic curves of the cycle, such as the work output versus pressure ratio curves, the efficiency versus pressure ratio curves, the maximum work output ratio versus temperature of the heat reservoirs curves, and so on, are presented. Three special cases are discussed in detail. The results obtained may reveal the general performance characteristics of a Brayton engine working with an ideal Fermi gas.

The Performance Analysis of a Quantum Brayton Refrigeration Cycle with an Ideal Bose Gas

A Brayton refrigeration cycle using an ideal Bose gas as the working substance is simply referred to as a quantum Brayton refrigeration cycle, which consists of two constant-pressure and two adiabatic processes. The influence of quantum degeneracy on the performance of the cycle is investigated, based on the correction equation of state of an ideal Bose gas. The general expressions of the coefficient of performance, refrigeration load and work input of the cycle are calculated. The lowest temperature of the working substance and the minimum pressure ratio of the two constant-pressure processes for a quantum Brayton refrigeration cycle are determined. The variations of the relative refrigeration load with the temperature of the cooled space and the pressure of the low constant-pressure process are discussed for three special cases. Some curves related to the important performance parameters are given. The results obtained here are compared with those of a classical Brayton refrigeration cycle using an ideal gas as the working substance. Some significant conclusions are obtained.

Influence of quantum degeneracy on the performance of a Stirling refrigerator working with an ideal Fermi gas : He, J. et al. Applied Energy, 2002, 72, (3–4), 541–554

Influence of quantum degeneracy on the performance of a Stirling refrigerator working with an ideal Fermi gas : He, J. et al. Applied Energy, 2002, 72, (3–4), 541–554

Influence of quantum degeneracy on the performance of a Stirling refrigerator working with an ideal Fermi gas

The influence of quantum degeneracy on the performance of a Stirling refrigeration cycle is investigated, based on the equation of state of an ideal Fermi gas. The inherent regenerative losses and the coefficient of performance (COP) of the cycle are calculated. It is found that, under the condition of strong gas degeneracy, the COP of the cycle in the first approximation is a function only of the temperatures of the heat reservoirs, while under other conditions, the COPs of the cycle depend on the temperatures of the heat reservoirs and other parameters of the cycle. The results obtained here reveal the general performance characteristics of a Stirling refrigeration cycle having a Fermi gas as its working substance.