Exergetic efficiency optimization for an irreversible quantum Brayton refrigerator with spin systems

The purpose of this paper is to study the optimal performance for an irreversible quantum Brayton refrigerator with spin systems, which consists of two isomagnetic field branches connected by two irreversible adiabatic branches. The time evolution of the total magnetic moment M is determined by solving the generalized quantum master equation of an open system in the Heisenberg picture. The time of two irreversible adiabatic processes is considered based on finite-rate evolution in this paper. The optimization region (or criteria) for an irreversible quantum Brayton refrigerator with spin systems is obtained. The relationship between the exergetic efficiency ε_E and dimensionless cooling load R for the irreversible quantum Brayton refrigerator with heat leakage and other irreversibility losses are derived.