A two-stage elastocaloric cooler for increased temperature span

Elastocaloric cooling has been pursued as an alternative to vapor compression refrigeration because it does not require the use of refrigerants that are harmful to the environment, and because comparable or greater coefficients of performance have been experimentally reported. However, no studies to date have demonstrated cold-side temperatures necessary for common refrigeration purposes, and instead report temperature spans more applicable to heat pumping. In this study, we have focused on maximizing the temperature drop from ambient in an experimental elastocaloric cooler. The cooler uses relatively inexpensive linear actuators for loading the refrigerant (as compared to other studies, which have used universal tensile testing machines), allowing for a multistage cooling approach using multiple linear actuators. We also implement regeneration – as has been demonstrated in other studies – to further minimize the cold-side temperature. The cooler has achieved temperatures down to 11°C using regeneration and no staging, which is about 4°C below the previous cold-side temperature record. We predict the cooler will be able to reach temperatures down to 7°C after implementation of a second stage. Nitinol wires with a diameter of 1.27 mm were used as the refrigerant, and we observed that it was essential that the transition temperatures of the Nitinol be sufficiently below the minimum temperature of the refrigerator. Our study provides an experimental method to push elastocaloric cooling towards temperatures relevant to common refrigeration applications.