Twistocaloric cooling with shape memory alloy wire bundles for low driving force

Twistocaloric cooling has shown promising advantages in terms of driving force requirement, specific cooling power, and coefficient of performance, demonstrating its potential for future elastocaloric refrigeration devices. However, compared to uniaxial or bending-induced elastocaloric effects, twistocaloric loading introduces complex multiaxial stress states that complicate both modeling and design. This study integrates experimental investigation and theoretical modeling to systematically examine the twistocaloric behavior of shape memory alloy (SMA) wire bundles, which resulted in a maximum average temperature drop of − 21.8 K and a normalized heat absorption of 338.627 μJ mm⁻³N⁻¹. The modeling framework also provides a powerful tool to comprehensively assess the stress distribution, temperature variation, and martensite volume fraction (phase transformation degree) across the cross-section of twisted SMA wires, as well as their safe operation range. Moreover, the mechanism of low driving force for twistocaloric cooling is also elucidated. Furthermore, parametric modeling also shows that the specific volumetric cooling power of the material increases with both the twisting loading rate and the helical radius of the SMA wire, while the cooling/heating capacity depends on the twist density. This work is expected to offer valuable insights into optimizing the design of twistocaloric refrigerants and the operational parameters.