SMA Film-Based Elastocaloric Cooling Devices

Abstract

AbstractThe ongoing trend of miniaturization and increasing power density in miniaturized systems demand for active temperature control and cooling. The cooling technologies utilized today depend on environmentally harmful substances or are bound to low efficiencies. This leads to an urgent need for innovative cooling technologies that are both environmentally friendly and efficient. This report focuses on shape memory alloy (SMA) film-based elastocaloric (eC) cooling, as SMA films exhibit a large eC effect and enable efficient heat transfer through solid-to-solid contact due to their large surface-to-volume ratio. Among the different material candidates, TiNiCuCo films are of special interest due to their ultra-low fatigue properties and small hysteresis. Single-stage SMA film-based eC devices reach a device temperature span up to 14 K combined with a high specific cooling capacity of up to 19 W g−1. However, absolute cooling capacities in the small-scale device are limited to 220 mW and the device temperature span already reaches the adiabatic limit of the used SMA film. To overcome the limitations in cooling capacity and device temperature span, novel advanced device architectures are explored. A parallelized cooling device combining the eC effect of five SMA films is engineered to increase the absolute cooling capacity up to 900 mW, while it preserves the high specific cooling capacity unique to SMA film-based cooling devices. A cascaded eC cooling device is developed, which consists of a serial arrangement of three SMA films. In this case, the device temperature span is increased beyond the adiabatic limit of a single film to 27.3 K. These results provide a basis for next-generation SMA film-based eC cooling technology.