Influence of different magnetic field profiles on the performance of a rotary magnetic refrigerator

In magnetic refrigerators, operation profiles (including flow profile and magnetic field profile) have great influence on system performance. This paper focuses on the study of the influence of the magnetic field profile in a rotary magnetic refrigerator. Based on the operating modes of the magnet, the magnetic field profile can be separated into two kinds: continuous and intermittent profiles. Firstly, the effects of two profiles on the active magnetic regenerator were experimentally studied. The temperature span, cooling power, power consumption (the direct magnet-driving power plus the fluid-pumping power) and COP were compared. At a fixed flow profile of 0.5 blow fraction, the intermittent profile has better performance in terms of temperature span and cooling power than the continuous profile at frequencies of 0.25, 0.40 and 0.55 Hz. When the frequency and utilization factor was 0.55 Hz and 0.52 respectively, a maximum temperature span of 22.7 K was achieved by the intermittent profile, which was 2 K bigger than the continuous profile. Then, a comprehensive research of three blow fractions (0.35, 0.5 and 0.65) was done for a better intermittent profile. When the blow fraction increased from 0.35 to 0.65, the temperature span and cooling power slightly increased. The experimental results showed a complicated relationship between the blow fraction and COP, which depended on the utilization factor. Typically, when the temperature span was 10 K at 0.40 Hz and 0.52 utilization factor, the COP decreased from 7.64 to 6.43 with the increase of blow fraction from 0.35 to 0.6.