A German research team has created an unusual thermal system based on nickel-titanium shape memory "muscles". When expanding, they are able to absorb heat, and when they return to their original state, give it back - and the temperature difference is more than 20 degrees. But these are the minimum values, in fact, German engineers managed to achieve much higher indicators that allow you to create an effective refrigeration unit.
In a simplified form, the prototype of the new refrigerator looks like a rotating cylinder on which nitinol ropes are wound (this is the name of this alloy). Rotating, the bundles on one side of the unit stretch and extract heat from the air, and then move to the other and shrink, releasing the heat outside. All that remains is to mount boxes with fans for air circulation in order to obtain a combined source of heat and cold.
The whole secret of the technology is in the scrupulous calculation of the parameters - the dimensions of the bundles themselves and their bundles, the speed of movement of individual parts, the load on the cylinder and wire, the parameters of air flows, etc. As a result, according to the authors of the development, they managed to achieve the maximum temperature difference between the two parts of the installation, while the power of the system is 30 times higher than the force that must be applied to expand and contract the nitinol wire mechanically.
The prototype of a mechanical refrigerator is twice as efficient as a conventional heat pump and three times as efficient as a traditional refrigerator. There are no toxic substances here, there is no need for heat exchangers and intermediate links, there is no need for sealed pipes, the air is cooled directly. And the choice of nitinol, as an alloy with the highest fatigue resistance, guarantees uninterrupted operation for many cycles.