Wednesday, April 1, 2009

Magnetic Refrigeration Advance

This discovery leaps to the heart of the major technical hurdle facing the development of a low cost Eden Machine. As previously stated it is feasible to produce a device able to meet the parameters established for the Eden Machine from current off the shelf technology. It is unfortunately too expensive to be useful in the market place in any great volume. It is still good enough to shake out and refine operating protocols and markets.

This development put magnetocalorics back into the driver’s seat in the development of new refrigeration tools. We cannot tell yet if this particular alloy will permit a simple cheap system yet, but it must be thought promising. At least the material cost component is starting cheap.

The problem with all refrigeration systems, including the advanced methods, is the need to do technical handstands in order to arrive at the necessary temperature points for the operating conditions. It sounds easy enough, but a study of the history will quickly end that notion. Right now we are discovering excellent starting materials with the correct temperature profiles necessary to make this all work. After that is settled, we are still in the business of trucking heat around a device that can easily become a Rube Goldberg monstrosity.

Technically, we want to parallel developments in the household refrigeration industry to quickly access the economics of mass production. This particular development is likely to be grabbed by that industry. This is very good news for the Eden Machine (check posts late 2008).

New Refrigeration System Based On Magnetics More Economical And Quieter Than Current Technology

ScienceDaily (Feb. 12, 2009) — Your refrigerator’s humming, electricity-guzzling cooling system could soon be a lot smaller, quieter and more economical thanks to an exotic metal alloy discovered by an international collaboration working at the National Institute of Standards and Technology (NIST)’s Center for Neutron Research (NCNR).

The alloy may prove to be a long-sought material that will permit magnetic cooling instead of the gas-compression systems used for home refrigeration and air conditioning. The magnetic cooling technique, though used for decades in science and industry, has yet to find application in the home because of technical and environmental hurdles—but the NIST collaboration may have overcome them.
Magnetic cooling relies on materials called magnetocalorics, which heat up when exposed to a powerful magnetic field. After they cool off by radiating this heat away, the magnetic field is removed, and their temperature drops again, this time dramatically. The effect can be used in a classic refrigeration cycle, and scientists have attained temperatures of nearly absolute zero this way. Two factors have kept magnetic cooling out of the consumer market: most magnetocalorics that function at close to room temperature require both the prohibitively expensive rare metal gadolinium and arsenic, a deadly toxin.

But conventional gas-compression refrigerators have their own drawbacks. They commonly use hydrofluorocarbons (HFCs), greenhouse gases that can contribute to climate change if they escape into the atmosphere. In addition, it is becoming increasingly difficult to improve traditional refrigeration. “The efficiency of the gas cycle has pretty much maxed out,” said Jeff Lynn of NCNR. “The idea is to replace that cycle with something else.”

The alloy the team has found—a mixture of manganese, iron, phosphorus and germanium—is not merely the first near-room-temperature magnetocaloric to contain neither gadolinium nor arsenic—rendering it both safer and cheaper—but also it has such strong magnetocaloric properties that a system based on it could rival gas compression in efficiency.

Working alongside (and inspired by) visiting scientists from the Beijing University of Technology, the team used NIST’s neutron diffraction equipment to analyze the novel alloy. They found that when exposed to a magnetic field, the newfound material’s crystal structure completely changes, which explains its exceptional performance.

“Understanding how to fine-tune this change in crystal structure may allow us to get our alloy’s efficiency even higher,” says NIST crystallographer Qing Huang. “We are still playing with the composition, and if we can get it to magnetize uniformly, we may be able to further improve the efficiency.”

Members of the collaboration include scientists from NIST, Beijing University of Technology, Princeton University and McGill University. Funding for the project was provided by NIST.

Journal reference:

1. D. Liu, M. Yue, J. Zhang, T.M. McQueen, J.W. Lynn, X. Wang, Y. Chen, J. Li, R.J. Cava, X. Liu, Z. Altounian and Q. Huang. Origin and tuning of the magnetocaloric effect for the magnetic refrigerant MnFe(P1-xGex). Physical Review B, Vol. 79, 014435 (2009)

1 comment:

Unknown said...

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Refrigeration Equipment