Elastocaloric Cooling Based on Tailored Rubber Films

该项目旨在研究和开发利用天然和合成橡胶/类橡胶材料薄膜中的弹性热效应的新型冷却装置。天然橡胶（NR）具有超过基于形状记忆合金的弹性热冷却的潜力，因为它具有17 Jg-1的大潜热、低应力水平、数百倍的大可逆应变和良好的小型化可扩展性的独特组合。此外，NR对环境友好，价格低廉。橡胶基弹性热冷却材料的开发采用两种不同的方法：(1)制备和研究NR，旨在了解分子对应变诱导结晶程度的影响。(2)将开发不同分子量和化学成分的合成橡胶，研究其对结晶、弹热温度变化、迟滞和抗疲劳性能的影响（J. r<s:1> he）。将开发基于橡胶薄膜的工程方法和工具，以实现具有优化效率和冷却能力的弹热冷却装置（M. Kohl）。为了克服导热系数低的问题，将制定策略来调整薄膜厚度和横向几何形状，以及引入和优化导电填料的含量。将通过有限元模拟和热成像来研究设备级温度分布的演变，以了解热/冷生成和热传递的负载依赖动力学。研究了橡胶薄膜与热源/散热器之间机械接触时的冷热分离问题。因此，接触面的形状和力将被调整，导热层的影响将被测试。最后，将制作一个演示系统，并就冷却能力和长期运行进行评估。

The project aims at the research and development of novel cooling devices using the elastocaloric effect in films of natural and synthetic rubber/rubber-like materials. Natural rubber (NR) has the potential to outperform shape memory alloy–based elastocaloric cooling as it exhibits a unique combination of large latent heat of 17 Jg-1, low stress levels, large reversible strain of several hundred percent and good scalability on miniaturization. Furthermore, NR is environmentally friendly and inexpensive. Two different approaches are pursued to develop rubber-based materials for elastocaloriccooling: (1) NR will be prepared and investigated aiming at understanding the molecular effects on the extent of strain-induced crystallization. (2) Synthetic rubber with varying molecular weight and chemical composition will be developed to investigate the effect oncrystallization, elastocaloric temperature change, hysteresis and fatigue resistance (J. Rühe). Engineering methods and tools will be developed based on the rubber films to realize elastocaloric cooling devices with optimized efficiency and cooling capacity (M. Kohl). In order to overcome the problem of low thermal conductivity, strategies will be developed to adjust film thickness and lateral geometry as well as to introduce and optimize the content of conductive fillers. The evolution of temperature profiles on the device level will be investigated by finite element simulation and thermography tounderstand the load-dependent kinetics of heat/cold generation and of heat transfer. Separation of heat and cold will be investigated for the case of alternating mechanical contact between rubber film and heat source/sink. Thereby, the shape and force of contacting surfaces will be adapted and the influence of thermally conductive layers will be tested. Finally, a demonstrator system will be fabricated and evaluated with respect to cooling capacity and long-term operation.