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/类橡胶材料薄膜的弹性热效应的新型冷却装置。天然橡胶(NR)表现出17JG-1的大潜热、低应力水平、几百%的大可逆应变和良好的小型化可伸缩性的独特组合，因此有可能超过基于形状记忆合金的弹性热冷却。此外，天然橡胶对环境友好，价格低廉。为了开发用于弹性热冷却的橡胶基材料，有两种不同的方法：(1)制备和研究天然橡胶，以了解分子效应对应变诱导结晶程度的影响。(2)将开发不同相对分子质量和化学组成的合成橡胶，以研究其对结晶、弹性热温度变化、滞后和抗疲劳性的影响(J.Rühe)。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性热能冷却装置(M.Kohl)。为了克服导热系数低的问题，将制定调整薄膜厚度和横向几何形状以及引入和优化导电填料含量的策略。将通过有限元模拟和热成像来研究器件水平上的温度分布的演变，以了解热/冷产生和热传递的随负荷变化的动力学。对于橡胶膜与热源/散热器之间的机械接触交替的情况，将研究冷热分离。因此，将适应接触表面的形状和力，并将测试导热层的影响。最后，将制作一个演示系统，并从制冷能力和长期运行方面进行评估。

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.