Cooling with “muscle” – Cooling Post
GERMANY: Engineers from the University of Saarland will present a prototype heating and cooling system using shape memory materials at the Hanover fair next month.
The machine is able to transfer heat using “muscles” made from nickel-titanium. Also known as nitinol, nickel titanium is a shape memory material that releases heat into its surroundings when mechanically charged in its superelastic state and absorbs heat from its surroundings when discharged.
This unusual property is the reason why nitinol is also called smart alloy or muscle wire. This effect was exploited by the research team led by Professors Stefan Seecke and Andreas Schütze who developed an environmentally friendly heating and cooling system that would be two to three times more efficient than heaters and heaters. conventional cooling.
The European Commission and the US Department of Energy have both reportedly evaluated the new process and see it as the most promising alternative technology to existing vapor compression refrigeration systems.
The underlying principle is simple and essentially consists in subjecting a particular shape memory alloy – in this case nickel-titanium – to controlled loading / unloading cycles.
“The resulting phase transitions that occur in the alloy’s crystal lattice release or absorb latent heat, depending on which part of the cycle the material is in,” Prof. Stefan Seecke explained. The effect would be particularly pronounced in nickel-titanium wires.
Research has shown that when pre-stressed nitinol wires are discharged at room temperature, they cool down to 20º. When the wires are mechanically loaded, they heat up by a similar amount, so the process can also be used as a heat pump.
The prototype is claimed to be the first continuously operating machine that cools the air using this process. The team designed and developed a patent pending cam drive whose rotation ensures that bundles of 200 micron thick nitinol wires are alternately charged and discharged so that heat is transferred as efficiently as possible. . The air is blown through the fiber bundles into two separate chambers: in one chamber the air is heated, in the other it is cooled. The appliance can therefore be used either as a heat pump or as a refrigerator.
They say the system is very efficient. Depending on the alloy used, the heating or cooling power of the system is up to 30 times the mechanical power required to load and unload the alloy wire bundles. According to the researchers, this already makes the new system at least twice as efficient as a conventional heat pump and 3 times better than a conventional refrigerator.
“Our new technology is also environmentally friendly and does not harm the climate, as the heat transfer mechanism does not use liquid or vapor. Thus, the air in an air conditioning system can be cooled directly without the need for an intermediate heat exchanger, and we do not need to use sealed high pressure piping, ”explained Professor Seekeke.
The team is currently working to further optimize heat transfer within the system to further increase the efficiency of the new technology. The goal is to reach a stage where almost all of the phase transition energy is used for heating or cooling.
The Saarbrücken engineering team will be exhibiting the technology at this year’s Hanover Fair from April 1-5 at the Saar Research and Innovation booth.
Develop the cold with “muscle” – February 3, 2016
GERMANY: Refrigeration using shape memory materials could be the energy-efficient, refrigerant-free cooling medium in the future, scientists say. Read more…