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Study of a rotary vane expander for the transcritical CO2 cycle. II. Theoretical modelling.

Author(s) : JIA X., YANG B., ZHANG B., et al.

Type of article: Article

Summary

A mathematic model focusing on expander thermodynamics and vane dynamics was developed to investigate the major factors influencing the efficiencies of the rotary vane expander. Several factors were taken into account, including the leakage through various leakage paths, friction associated with the vanes, and flow through the inlet/outlet ports. The model was validated by comparing the calculated thermodynamic processes and vane movement with the experimental data, which showed the deviation was less than 10%. The predicted results from the model indicated that the expander would have an optimum pressure ratio of about 2.2. Although the volumetric efficiency increased with the rotational speed, the optimal rotational speed of 2300 rpm was obtained at inlet and outlet pressures 8 MPa (1160 psi) and 4 MPa (580 psi) and an inlet temperature of 40°C. The leakage through both the end gaps and the sealing arc had a significant influence on the expander efficiency, accounting for 35 and 28%, respectively, of the losses in the volumetric efficiency. Among the major geometric parameters of the expander, larger eccentricity and vane incline angle had a positive effect on the expander efficiencies, and the increase in the vane width had a negative effect, while the effect of the ratio of length to radius seemed to be insignificant. See also this Bulletin, reference 2010-0294.

Details

  • Original title: Study of a rotary vane expander for the transcritical CO2 cycle. II. Theoretical modelling.
  • Record ID : 2010-0295
  • Languages: English
  • Source: HVAC&R Research - vol. 15 - n. 4
  • Publication date: 2009/07

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