CHARACTERISTICS OF BINARY MIXTURES OF CARBON DIOXIDE WITH ETHANE AND PROPANE AS WORKING SUBSTANCES OF REFRIGERATING MACHINES

Abstract

Equations of state for mixtures of carbon dioxide (R744) with ethane (R170) and propane (R290)  were composed in the form of combination of free Helmholtz energy of components of mixture and the interaction function of components. Coefficients of equations were determined mainly on the basis of data on density at temperatures 207…478 K and pressures up to 69 MPa for mixture R170/R744 and at 222…511 K up to 70 MPa for mixture R290/R744 tacking into account the requirements of phase equilibrium. The thermodynamic behavior of mixtures at saturation state was analysed. It was established that the difference of temperatures of saturated vapor and liquid on isobars for mixture R170/R744 reach 5,8 K. At mole fraction R744 equal 0,6 mixture practically is azeotropic. In the mixture R290/R744 this difference reaches 38 K. The values of performance factor and specific volume refrigerating effect were calculated of cycle of one-step refrigerating machine using these mixtures as working medias.