Conventionally, refrigerators or freezers use refrigerants to generate their cold temperatures. To effectively cool the contents inside, refrigerants make use of a cycle of evaporation and condensation. Evaporation is an endothermic process, absorbing heat from the surrounding environment, which results in a cool refrigerator interior.
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As the refrigerant warms up, it is transformed into a gas. A compressor then pressurizes the gaseous refrigerant, and it will eventually be condensed back into a liquid to cool the interior of the refrigerator over again. This refrigeration cycle is the driving force behind the cooling effect in modern fridges and freezers. Now, a new innovation may revolutionize how refrigeration works.
Metal shapeshifter
Nitinol is an alloy made of nickel and titanium. It is a pliable shapeshifting metal that can be manipulated and contorted, and when exposed to heat, it can snap back into its original shape. Nitinol has the capacity to “remember” its original form no matter how much bending and warping it experiences. This behavior is known as the shape memory effect.
Hot and cold
Another key and fascinating feature of nitinol, as it is manipulated into other shapes, deviating from its original form, is that it absorbs heat from its surrounding environment. Conversely, when it snaps back into its original shape, it demonstrates the capacity to release heat.
Nitinol coolant
Academics are now proposing to use nitinol instead of a gaseous refrigerant, and a team of researchers from Saarland University in Germany has developed a proof of concept.
The team amassed bundles of nitinol wire, wrapping it around a cylinder. On one side of the cylinder, the wires were being manipulated and bent; on the other, they were being snapped back. Fans were then placed on either side as cool air flowed out of the side where the wires were bent while warm air was expelled from the other side.
Simply put, the shape memory effect of nitinol acts as a heat pump. When bent, the wire absorbed heat from one side of the cylinder and was then able to transfer it to the other side as the wire returned to its original shape.
Is this the future of refrigeration?
The nitinol-powered cooling system could radically simplify refrigeration systems by eliminating the need for refrigerants and compressors. In turn, this would make such systems much easier to construct and maintain. Moreover, it could cut costs by making refrigeration systems less expensive, as fewer parts are required.
The results of the scientists’ experiments with nitinol cooling are extraordinary, as the team reports that the cooling output is up to 30 times greater than the mechanical energy required to bend and snap back the wires.
The Saarland team also believes this system can be up to three times more efficient than a conventional refrigerator. Moreover, it is also environmentally compatible as no chemical refrigerants are needed, making it a greener solution.
Once this system has been scaled and is ready for commercialization, a new breed of refrigerators, chillers, and ultralow temperature freezers could be on the horizon.
About inTEST Thermal Solutions
inTEST Thermal Solutions (iTS) specializes in the design and manufacture of precision temperature control systems. Our breadth of products and in-house engineering capabilities allow us to be a single-partner-solution for thermal test, process cooling, and cold storage applications. We are recognized globally for our expertise in precise temperature control and simulation of extreme thermal environments, from -185 to +500 °C, with rapid transitions or long dwell times. The iTS family includes four product brands: Temptronic, Sigma Systems, Thermonics, and North Sciences. inTEST Thermal Solutions is a wholly owned subsidiary of inTEST Corp, Mount Laurel, New Jersey, USA.
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