Elastocaloric cooling is a novel environment-friendly alternative to vapor compression-based cooling systems. This solid-state cooling technology uses NiTi shape memory alloys (SMAs) as cooling medium. SMAs are well known for lightweight actuator systems and biomedical applications, but in addition, these alloys exhibit excellent cooling properties. Due to the high latent heats activated by mechanical loading/unloading, large temperature changes can be generated in the material. Accompanied by a small required work input, this also leads to a high coefficient of performance superior to vapor compression-based systems. In order to access the potential of these alloys, the development of suitable thermodynamic cooling cycles and an efficient system design are required. This paper presents a model-based design process of an elastocaloric air-cooling device. The device is divided into two parts, a mechanical system for continuously loading and unloading of multiple SMA wire bundles by a rotary motor and a heat transfer system. The heat transfer system enables an efficient heat exchange between the heat source and the SMA wires as well as between the SMA wires and the environment. The device operates without any additional heat transfer medium and cools the heat source directly, which is an advantage in comparison to conventional cooling systems. The design of this complex device in an efficient manner requires a model approach, capable of predicting the system parameters cooling power, mechanical work and coefficient of performance under various operating conditions. The developed model consists of a computationally efficient, thermo-mechanically coupled and energy based SMA model, a model of the system kinematics and a heat transfer model. With this approach, the complete cooling system can be simulated, and the required number of SMA wires as well as the mechanical power can be predicted in order to meet the system requirements. Based on the simulation results a first prototype of the elastocaloric cooling system is realized.
- Aerospace Division
Elastocaloric Cooling: System Design, Simulation, and Realization
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Welsch, F, Kirsch, S, Michaelis, N, Motzki, P, Schmidt, M, Schütze, A, & Seelecke, S. "Elastocaloric Cooling: System Design, Simulation, and Realization." Proceedings of the ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies. San Antonio, Texas, USA. September 10–12, 2018. V002T08A005. ASME. https://doi.org/10.1115/SMASIS2018-7982
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