Acoustic determination of thermophysical properties and critical parameters for R404A and critical line of xCO(2) + (1-x)R404A

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The thermophysical properties and critical parameters for the alternative refrigerant R404A ( 52 wt % of 1,1,1-trifluoroethane (R143a) + 44 wt % of pentafluoroethane (R125) + 4 wt % of 1,1,1,2-tetrafluoroethane (R134a)) were investigated using two different acoustic techniques. The critical behavior of the system xCO(2) + (1 - x) R404A was also investigated. Experimental data of speed of sound in liquid R404A from 258 K to 338 K and pressures up to 65 MPa were measured using a pulse-echo method. Derived thermodynamic properties are calculated, combining our experimental data with density and isobaric heat capacity values published by other authors. Measurements of the critical temperature T-c and pressure p(c) on (R404A) and mixtures of xCO(2) + ( 1 - x) R404A were performed using another simple ultrasonic time-delay technique. The binary critical line was determined over the whole composition range showing that this system deviates only slightly from ideality since the critical line is a continuous line. The Peng-Robinson equation of state with conventional mixing and combining rules was used to correlate the binary experimental data.
Original languageEnglish
Pages (from-to)1148-1155
JournalJournal of Chemical and Engineering Data
Issue number3
Publication statusPublished - May 2006



  • Thermodynamic properties
  • 65 MPA
  • Pressures
  • Speed
  • Sound
  • Mixtures
  • Equation
  • State
  • Equilibria
  • R-404A

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