Numerical simulations for regenerator optimization in an experimental elastocaloric cooling prototype based on shape memory alloys

The SMACOOL (acronym for Shape Memory Alloy based elastocaloric CooLing system) project aims to develop a rotary elastocaloric-based air-conditioning system utilizing shape memory alloys as solid-state refrigerants. Solid-state refrigeration based on the elastocaloric effect offers a promising alternative to vapor compression systems, but it still faces major challenges such as low energy efficiency, mechanical fatigue of materials, and complex regenerator design. Addressing these issues is crucial to enable practical implementation in real cooling applications. In this study, a numerical investigation was carried out to optimize the regenerator design, comparing tension and compression loading modes and different geometries, namely parallel plates and spiral cross-sections. Model validation against experimental data and mesh independence analyses confirmed the reliability of the numerical approach. Finite element simulations revealed that compression mode outperforms tension, achieving cold-side temperature lifts up to 10 times higher and cooling powers up to 4 times higher under identical operating conditions. Spiral geometries showed up to 115% higher ΔTcold and up to 314% higher cooling power compared to parallel plates in Active elastocaloric Regenerative refrigeration cycle. In Heat Recovery cycle, the spiral regenerator achieved an increase up to: 123% for ΔTcold, 22% for cooling power and 55% for COP respect to parallel plates. The study also highlights that internal buckling prevention material negatively affects thermal performance. Based on these findings, a spiral compression regenerator was selected for the SMACOOL prototype, targeting enhanced energy efficiency and system durability.