Numerical Analysis on the Exploitation of Niti-Based Shape Memory Alloys in an Elastocaloric Device for Air Conditioning

Elastocaloric is a promising cooling technique that offers a solid-state alternative to vapor compression. The elastoCaloric Effect (eCE) refers to the reversible changes in temperature and entropy that occur in Shape Memory Alloy (SMA) when loaded/unloaded by an external mechanical load. The research introduced in this paper compares various Ni–Ti-based SMAs to determine the optimal one to be exploited in an experimental air conditioner. The device can lodge 600 SMA wires in the space stacked by two cylinders concentrically arranged, with inner/outer diameter of 250/280 mm. Tests are performed while the device rotates at variable frequencies ranging from 0.3 Hz to 0.7 Hz. A rotary meshing two-dimensional tool has been developed and used to perform the test campaign under variable working conditions and NiTi-based SMAs. The energy performances are evaluated and (Ni₅₀Mn_31.5Ti_18.5)_99.8B_0.2 resulted in the most suitable SMA showing 2.13 kW as peak of cooling power (at a cycle frequency of 0.6 Hz and a utilization factor of 0.7) and a maximum COP of 8.35 (at 0.3 Hz and 0.7 as utilization factor). This work demonstrates that the use of the (Ni₅₀Mn_31.5Ti_18.5)_99.8B_0.2 alloy can enable the device to achieve performances superior to vapor compression-based devices.