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Phase behavior of some binary mixtures of refrigerants with carbon dioxide


A. Vasserman1, S. Kozlovsky1 and V. Malchevsky1

1Odessa National Maritime University, Ukraine

Keywords: mixtures, phase behavior
property: saturated state, temperature, pressure
material: carbon dioxide, refrigerants, R23, R41, R170

The binary mixtures of ozone-safe refrigerants R23, R41 and natural refri-gerant R170 with carbon dioxide (R744) are considered as new working media for refrigerating machines. The temperatures of solidification of these mixtures are lower than of carbon dioxide and mixtures R41/R744 and R290/R744 are not inflammable (in contradistinction to R41 and R290).

On the basis of the experimental p, ρ, T, x - data we compiled equations of state for binary mixtures of refrigerants R23, R41 and R170 with carbon dioxide [1-3]. By means of these equations the thermodynamic properties of three mixtures were calculated and their phase behavior at saturation state was analysed.

For the analysis of the phase behavior of mixtures the diagrams p, T, x were drawn. They represents the dependence of pressure from temperature and composition for four compositions (0.2; 0,4; 0;6 and 0.8 mole fraction of first component) and for pure components. From these diagrams it can show that three mixtures are not aseotropic. Nevertheless the curves of boiling and condensation for all compositions are very near.

The dependence of temperatures' difference of vapor and liquid at saturation state on isobars `Delta`T from pressure and from middle values of temperature on isobars was investigated for indicated compositions of mixtures. The value of ΔT in intervals from 0.1 up to 5.9 MPa and from 180 to 310 K not exceed 1,3 K for mixture R23/R744, 1,8 K for R41/R744 and 4,3 K for R170/R744. For the last mixture at 0,4 mole fraction of R170 maximum value ΔT is equal 1,7 K.

The indicated little value of ΔT permits to maintain the optimum values of temperatures' difference between refrigerant during its condensation and water or air and also between the cooled body and refrigerant during its boiling. This promotes to decrease the losses from irreversibility of processes of heat exchange at finite difference of temperatures. Therefore these mixtures may be used as refrigerants.

References
  1. V.P. Malchevsky, Re-frigeration engineering and technology (2006)No.6. p. 66-69 (Ukrainian edi-tion)

  2. A.A Vasserman, V.P. Malchevsky, Herald of Odessa national maritime university (2007) №21 p. 97-108 (Ukrainian edition)

  3. A.A. Vasserman, S.V. Kozlovsky, V.P. Malchevsky, Refrigeration engineering and technology (2009) No.6 p. 55-59 (Ukrainian edition)

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