Effect of cross-sectional geometry on the compression fatigue behavior of NiTi refrigerants

Elastocaloric refrigeration requires refrigerants with a good heat transfer ability and a high fatigue life. A million-level fatigue life can be normally obtained for NiTi refrigerants via compressive loading. However, existing compression-based NiTi elastocaloric prototypes only focus on tube refrigerants, and no research has been reported on the cross-sectional geometry design and its influence on the compression fatigue behavior of NiTi refrigerants. Here, we propose tubular NiTi refrigerants of hole-type, fin-type, and layer-type cross sections and compare their compression fatigue behavior with NiTi tubes of the same cross-sectional area under cyclic loading of 20 Hz and 900 MPa. Results show that to achieve a larger specific heat transfer area (SA), the compression fatigue life of NiTi tubes monotonically decreases because of the decrease in the wall-thickness, while the layer-type NiTi refrigerant maintains a relatively high fatigue life of 1.7 × 106 cycles at a high SA level (3.83 cm2 g−1). This gives us insight into enhancing elastocaloric refrigerants’ heat transfer ability and fatigue life via geometry design.