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Third generation CO2 expander.

Author(s) : NICKL J., WILL G., KRAUS W. E., et al.

Summary

If one replaces the throttle valve in a transcritical CO2 refrigeration cycle by a work extracting expander, the COP of the cycle can be improved considerably. Between 1995 and 2000 in our laboratory, a first-generation expander-compressor with two expansion and two compression cylinders was designed and manufactured. It was tested in an experimental refrigeration loop and brought an improvement of about 30% compared with the same plant operated with a throttle valve. One drawback of the first generation expander was that the expander could be operated only in the so-called full-pressure mode. This was caused by the machine principle, where the expander and compressor pistons are moved always with exactly identical strokes. Therefore in a second generation expander, which was described in 2002, the movement of expander and compressor pistons were partly decoupled. This brought a further improvement in performance, but the device still depended on complicated and expensive expander inlet and outlet valves. With the third generation expander we now overcome this deficiency. The expansion is now done by three full-pressure expansion stages in series, whereas the compression is still done by one double-acting piston, in line with the expansion stages. The inlet and outlet flows of the CO2 to and from the expansion cylinders are handled by a common sleeve valve. Testing of this third generation expander is planned for summer 2003.

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Details

  • Original title: Third generation CO2 expander.
  • Record ID : 2005-0071
  • Languages: English
  • Source: 21st IIR International Congress of Refrigeration: Serving the Needs of Mankind.
  • Publication date: 2003/08/17

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