基于不同流动时间占比的紧凑式室温磁制冷系统实验研究

Experimental study of compact room temperature magnetic cooling system based on different flow time ratios

磁制冷因高效、环保、结构简单等特点,正有望成为替代传统蒸气制冷的新型室温制冷技术之一.当前针对单一影响因子对磁制冷样机的影响作用规律研究较为丰富,但对磁场-流场时序中流动时间占比工况的研究较少,且影响规律尚不明晰.本文以前期研制的紧凑型室温磁制冷系统为基础,在固定的磁场时序情况下开展不同流动时间占比的实验研究,探索制冷温跨、制冷量、压降及性能系数与流动时间占比之间的关联.以磁场时序1:4:1:4与频率0.45 Hz的工况为例,开展了固定磁场时序的不同流动时间占比(100%,80%,60%)的实验研究.结果表明:1)小利用系数和高流动时间的组合可获得较大温跨,大利用系数和高流动时间占比的组合可获得较大冷量,其中当利用系数为0.42、流动时间占比为100%时,获得最大无负荷制冷温跨26.2 K;2)对比研究了利用系数与流动时间占比对回热器压降及性能系数的影响,流动时间占比的增大和利用系数的减小均会造成流体速度的减小,会使压降进一步减小,性能系数进一步增大.本研究阐明了制冷温跨、制冷量、压降及性能系数与流动时间占比之间的影响规律,为进一步提升室温磁制冷机的性能奠定基础.

Magnetic refrigeration has become a promising new technology to replace conventional vapor-compression refrigeration technology,for it has excellent application characteristics such as the high efficiency,environmental friendliness and structural simplicity.Many studies have been carried out to analyze the various subsystems,but the interaction laws between the systems are not yet clear,and the optimization of each subsystem is still an area of research worth exploring.This work is based on a compact room temperature magnetic refrigeration system developed before,and carries out experimental research on the different flow time ratio to explore the correlation among refrigeration temperature span,cooling capacity,pressure drop,coefficient of performance(COP)and blow fraction under a fixed magnetic field timing.Especially,the effects of different flow time ratios(100%,80%,60%)on the system performance are studied under magnetic field timing of 1∶4∶1∶4 and a frequency of 0.45 Hz.The experimental results reveal that a low utilization factor combined with a high flow time ratio can achieve a greater temperature spread,whereas a high utilization factor combined with a high flow time ratio can accomplish a bigger cooling capacity.When the utilization factor is 0.42 and the flow time ratio is 100%,the maximum unloaded cooling temperature span is 26.2 K.Meanwhile,the effects of the utilization factor and flow time ratio on the pressure drop and COP of the regenerator are studied in detail.It is discovered that raising the flow time ratio and reducing the utilization factor both result in a fall in fluid velocity,which leads the pressure to further decrease and the COP to rise.In a word,this research investigates the relationship among cooling temperature span,cooling capacity,pressure drop,COP,and flow time ratio in a fixed magnetic field timing,thus providing the groundwork for future improving the performances of room temperature magnetic refrigeration systems.