Present refrigerator using CFC gases which depleted our ozone layer and other gases such as Amonia and sulpherdioxide and propen materials which are harmful to our environment. Because of that some scientists developed new cooling materials like natural rubber and nickel-titanium wire which cool refrigerators uses the technology of twisting and untwisting of natural rubber .
Theory Of Cooling:
According to law of thermodynamics it was stated that ordinary rubber heats up after stretching and cools down after relax.
Using deformation technique of such materials like rubber, fiber, nickel-titanium and polyethylene fishing line changes their entropy after deformed.
Researchers from Texus university and Nankai University China achieved a surface cooling of 16°c for supercoiled fibers of natural rubber and 20°c for nickel-titunium wire and 5°c for polyethylene fishing line by continuously twisting and stretching of those materials.
Researchers were trying to develoved new materials which cooled more and the materials last long. If twisting referegerator was commercially viable then its very ecofriendly and good for environment.
Source: https://physicsworld.com/a/refrigerator-works-by-twisting-and-untwisting-fibres/