Joseph Joel, Ohtsuka Makoto, Miki Hiroyuki, Kohl Manfred
Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Postfach 3640, D-76021 Karlsruhe, Germany.
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
Materials (Basel). 2021 Mar 5;14(5):1234. doi: 10.3390/ma14051234.
This paper presents a lumped element model (LEM) to describe the coupled dynamic properties of thermomagnetic generators (TMGs) based on magnetic shape memory alloy (MSMA) films. The TMG generators make use of the concept of resonant self-actuation of a freely movable cantilever, caused by a large abrupt temperature-dependent change of magnetization and rapid heat transfer inherent to the MSMA films. The LEM is validated for the case of a Ni-Mn-Ga film with Curie temperature T of 375 K. For a heat source temperature of 443 K, the maximum power generated is 3.1 µW corresponding to a power density with respect to the active material's volume of 80 mW/cm. Corresponding LEM simulations allow for a detailed study of the time-resolved temperature change of the MSMA film, the change of magnetic field at the position of the film and of the corresponding film magnetization. Resonant self-actuation is observed at 114 Hz, while rapid temperature changes of about 10 K occur within 1 ms during mechanical contact between heat source and Ni-Mn-Ga film. The LEM is used to estimate the effect of decreasing T on the lower limit of heat source temperature in order to predict possible routes towards waste heat recovery near room temperature.
本文提出了一种集总元件模型（LEM），用于描述基于磁形状记忆合金（MSMA）薄膜的热磁发电机（TMG）的耦合动态特性。TMG发电机利用了自由移动悬臂梁的共振自驱动概念，该概念由MSMA薄膜固有的与温度相关的大的磁化突变变化和快速热传递引起。针对居里温度T为375 K的镍锰镓薄膜情况对该LEM进行了验证。对于443 K的热源温度，产生的最大功率为3.1 μW，相对于活性材料体积的功率密度为80 mW/cm。相应的LEM模拟允许对MSMA薄膜的时间分辨温度变化、薄膜位置处的磁场变化以及相应的薄膜磁化强度变化进行详细研究。在114 Hz处观察到共振自驱动，而在热源与镍锰镓薄膜机械接触期间，1 ms内会出现约10 K的快速温度变化。该LEM用于估计降低T对热源温度下限的影响，以便预测接近室温的废热回收的可能途径。
