功熵与功(火用)

类似于克劳修斯采用由3个等温过程和3个绝热过程组成的可逆热转功循环,建立热向功转换与热量从高温向低温转换的等价定律,并导出克劳修斯等式和熵的方法.本文采用由3个等压过程和3个等容过程组成的可逆功转热循环,建立了功向热转换与功量从高压向低压转换的等价定律,导出了逆循环等式和功熵,并推广至任意可逆的逆循环.系统的体积就是功熵,它是逆循环的核心物理量.类似于(火用)的定义和表达式,定义了新的物理量——功(火用),并借助于逆p-V循环导得了它的表达式.而后阐明了功熵和功(火用)的物理意义,并与热熵和热(火用)的物理意义进行对比.最后介绍了它们在可逆过程性能分析中的应用.

Optimization of the performance characteristics in an irreversible regeneration magnetic Brayton refrigeration cycle

A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established,in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically.Expressions for the COP,cooling rate,power input,theminimum ratio of the two magnetic fields,etc.,are derived.It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable.It is important that we have obtained several optimal criteria,which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator.The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.