Solid state refrigeration: Cooling and refrigeration using crystalline phase changes in metal alloys

The well-known fact that a phase change is normally accompanied by a relatively large change in internal energy is explored and is used to develop an innovative method of achieving refrigerative effects in solid state metal alloys. Applying a cyclic mechanical stress in certain materials can induce crystalline structural changes, with accompanying absorption or release of heat. Simple experiments are reported with a particular nickel-titanium alloy where temperature drops well below 10 °C of ambient were achieved. The experimental work was undertaken at ambient temperature and temperature excursions of + 16 and -14 °C of ambient temperatures were measured. These temperature excursions occurred in a material with a density of over 6000 kg/m3. Ways in which the concept of ‘solid state refrigeration’ using mechanical actuation are suggested and partially examined.