Elastocaloric effect of Ni-Ti wire for application in a cooling device
Elastocaloric effect of Ni-Ti wire for application in a cooling device
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DOI：
10.1063/1.4913878
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发表时间：
2015-03-28
影响因子：
3.2
通讯作者：
Pryds, N.
中科院分区：
文献类型：
--
作者：
Tusek, J.;Engelbrecht, K.;Pryds, N.
我们报告的弹性热效应的超弹性镍钛丝用于冷却装置。最初，对每根评估的导丝进行400次加载/卸载训练循环，以稳定其超弹性行为。在不同温度下对丝进行拉伸，得到不同的稳定超弹性行为。在不同温度（从312 K到342 K）下对稳定（训练）的丝进行了进一步的等温（低应变率）和绝热（高应变率）测试。我们研究了训练温度和由此产生的超弹性行为对绝热温度变化的影响。加载过程中测得的最大绝热温度变化为25 K，卸载过程中相应的变化为21 K（322 K）。特别关注加载和卸载之间绝热温度变化的不可逆性。结果表明，有两个来源的温度不可逆性：滞后（和相关的熵产生）和暂时的残余应变后立即卸载，分别。后者导致导线的暂时弯曲和减小的负绝热温度变化。本文还示出了施加的应变的绝热温度变化的影响，以及在加载过程中的两个线在不同的温度下训练的情况下，和处女线，分别在导线上的弹热效应的分布。最后，我们提出了一个有效的弹热冷却装置所需的材料性能的指导方针。(C)2015 AIP Publishing LLC.
We report on the elastocaloric effect of a superelastic Ni-Ti wire to be used in a cooling device. Initially, each evaluated wire was subjected to 400 loading/unloading training cycles in order to stabilize its superelastic behavior. The wires were trained at different temperatures, which lead to different stabilized superelastic behaviors. The stabilized (trained) wires were further tested isothermally (at low strain-rate) and adiabatically (at high strain-rate) at different temperatures (from 312 K to 342 K). We studied the impact of the training temperature and resulting superelastic behavior on the adiabatic temperature changes. The largest measured adiabatic temperature change during loading was 25 K with a corresponding 21K change during unloading (at 322 K). A special focus was put on the irreversibilities in the adiabatic temperature changes between loading and unloading. It was shown that there are two sources of the temperature irreversibilities: the hysteresis (and related entropy generation) and the temporary residual strain immediately after unloading, respectively. The latter results in the temporary bending of the wire and reduced negative adiabatic temperature change. The paper also shows the impact of the applied strain on the adiabatic temperature changes as well as the distribution of the elastocaloric effect over the wire during loading in the case of two wires trained at different temperatures and the virgin wire, respectively. In the end, we propose guidelines about the required material properties for an efficient elastocaloric cooling device. (C) 2015 AIP Publishing LLC.