不可逆回热式磁Brayton循环制冷性能的理论及数值研究

基于统计理论推导的铁磁材料的磁热参数,建立了不可逆回热式磁Brayton循环数学模型.对于顺磁材料作工质的情形,获得了循环放热量QH、制冷量QC、回热量及性能系数δCOP的表达式的解析解.以铁磁材料钆作工质为例,数值研究了循环室温区的制冷性能,考察了归一化温度α、回热不平衡量QR及磁化过程不可逆度η对循环有效制冷量Qeff,C及δCOP的影响,并获得了不同外部磁场H1条件下循环最大温跨δT,max.数值结果显示:Qeff,C随α的增加而增加;当α≥0.6或QR≥0时,循环均能获得良好的制冷性能;磁化过程的不可逆因素会使得δCOP迅速下降.

Theoretical and Numerical Investigations on Refrigeration Performance of Irreversible Regenerative Magnetic Brayton Cycle

On the basis of magneto-thermo parameters of ferromagnetic material deduced by the statistic theory,a mathematical model for the irreversible regenerative magnetic Brayton cycle was established.For the case of paramagnetic material,the analytic solution of heat release Q_H,refrigeration capacity Q_C,regenerative heat,and coefficient of performance δ_(COP) were achieved.The numerical study on the refrigeration performance in room-temperature regions of the cycle was conducted for ferromagnetic material,Gadolinium.The influence of dimensionless temperature α,imbalance regenerative heat Q_R.and irreversible degree η on effective refrigeration capacity Q_(eff).C and δ_(COP) was examined,and maximum temperature span δT,max under different external magnetic field H_1 of the cycle was obtained.The numerical results show that Q_(eff),C increases with the increase of α,and the cycle has high refrigeration performance when α≥0.6 or Q_R≥0.In addition,δ_(COP) of the cycle decreases rapidly because of irreversible factors in magnetizing processes.