Influence of timing between magnetic field and fluid flow in a rotary magnetic refrigerator

An active magnetic regenerator with magnetic Brayton cycle is adopted in a rotary-magnet type refrigerator. For the performance of the magnetic refrigerator, timing between the magnetic field and fluid flow profiles is important. This paper experimentally studied the influence of timing between magnetic field profile and fluid flow profile on the performance of a rotary magnetic refrigerator. A timing ratio is defined to indicate the relative time lengths of four processes (magnetization, hot blow, demagnetization, cold blow). Under four different timing ratios, the cooling capacity, temperature span, pressure drop and power consumption are experimentally investigated. A no-load temperature span of 19.8 K is achieved at the timing ratio of 1:4:1:4, which is 2.6 K higher than that at the ratio of 1:1:1:1. The results reveal that, at the same utilization factor and frequency, the longer the flow time, the larger the temperature span. The influence of utilization factor and operating frequency are also studied. Though limited by the motor power, a cooling power of 20 W at temperature span of 12.3 K is achieved with the timing ratio of 1:2:1:2 at 0.75 Hz, and the corresponding specific cooling power is approximately 94 W/kg.