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Equations of state for design of centrifugal compressor.

Number: pap. ID: 645

Author(s) : OLDRICH J.

Summary

The main goal of this contribution is to show how important is selection of real gas model for thermodynamic design of compressor. This is particularly important especially for refrigeration compressor. This compressor work very often in range of pressure and temperatures that is very closed to saturated vapour curve where the compressed refrigerant has significant deviations from ideal gas behavior. Centrifugal compressors compress a various gas mixtures. Compressors usually operate in a wide range of temperatures and pressures, where the thermodynamic properties of gases and gas mixtures deviate from the ideal gas laws. It is therefore necessary for design of the compressor and for evaluation of measurements carried out on the compressor to use real gas methods. The base of thermodynamic calculations is the solution of equations of state. There are a large number of equations for a description of the state behavior of real gas. In technical practice are usually used BWR type equations, which are from mathematical point of view nonlinear algebraic equations. Their solution is performed by iterative methods. Isentropic head has important role in case of the thermodynamic calculation of the centrifugal compressor. Again, we can take into account the ideal or real behavior of gases. Assuming that the gas behaves as an ideal, the calculation is very simple but also very inaccurate. Only real gas model gives good results. In engineering practice, we can see a relatively large number of equations of real gas. But only a few of them are suitable for compressor calculations. The paper demonstrates what criteria the equation of state used to design of compressors have to meet. Because for the design of compressor stages CFD methods are very often used, a comparison of equation used in ANSYS CFX with the most commonly used BWR equation of state was done.

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Pages: 8 p.

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Details

  • Original title: Equations of state for design of centrifugal compressor.
  • Record ID : 30002101
  • Languages: English
  • Source: Proceedings of the 23rd IIR International Congress of Refrigeration: Prague, Czech Republic, August 21-26, 2011. Overarching theme: Refrigeration for Sustainable Development.
  • Publication date: 2011/08/21

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