I noticed this when I had nickel-titanium glasses frames maybe 20 years ago. If I folded them in half at the bridge they would get hot, I could then conduct the heat away with my fingers, then, releasing the tension, the bridge would get very cold. Just like a refrigerant, but solid.

I did wonder at the time if they could replace the refrigerant in fridges with this but figured they would eventually fail from repeated bending.