Natural Rubber Foil-Based Elastocaloric Cooling

Abstract:
We present the design and characterization of solid-state elastocaloric cooling devices based on a natural rubber (NR) foil. Two different loading mechanisms are explored using either two linear actuators or a bistable actuation mechanism using a rotating lever arm, which allows for reduced loading forces by a factor of three. The thicknesses of the investigated NR foil refrigerants are 290 and 650 µm in initial undeformed state while their lateral size is 9 x 26.5 mm². Owing to the small thickness, heat transfer is accomplished by solid-solid contact between the NR foil and planar heat sink and source elements. The optimal operation frequency depends on the NR foil thickness increasing from 140 to 540 mHz for a thickness of 650 and 290 µm, respectively. The maximum temperature span DeltaTDevice is 4.1 K while the coefficient of performance COPDevice reaches values up to 4.7. A maximum cooling power of 144 mW is achieved for bistable actuation, which is enhanced by 17% compared to linear actuation. The specific cooling power increases with decreasing foil thickness reaching 1.2 Wg-1 at 290 µm for bistable actuation.