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Modelling of compressors and expansion devices with two-phase refrigerant inlet conditions.

Author(s) : SHEN B., BRAUN J. E., GROLL E. A.

Summary

Simulation models for unitary air conditioners and heat pumps usually cannot provide accurate predictions in the case of two-phase refrigerant entering the compressor or fixed-area expansion device. This paper focuses on improving modelling methods in these situations. The study utilized extensive laboratory tests and detailed modelling of two unitary air conditioners, one using R-410A and the other R-407C. Heat exchanger models were used to give upstream qualities of the compressor and fixed orifice. It was found that it is best to use a two-phase suction density correction for compressor maps to predict the mass flow rate. However, using a two-phase suction density correction with a compressor map to predict the power consumption leads to significant under-predictions. It is best not to correct the compressor map power consumption for a two-phase entering condition. For the case of two-phase refrigerant entering a fixed-area expansion device, mass flow rate predictions from short-tube orifice models are extremely sensitive to the upstream quality. A two-point charge tuning method is recommended, as it can lead to an accurate prediction of upstream state for the expansion device at all refrigerant charge levels.

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Details

  • Original title: Modelling of compressors and expansion devices with two-phase refrigerant inlet conditions.
  • Record ID : 2008-2066
  • Languages: English
  • Source: 2006 Purdue Conferences. 18th International Compressor Engineering Conference at Purdue & 11th International Refrigeration and Air-Conditioning Conference at Purdue [CD-ROM].
  • Publication date: 2006/07/17

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