**R404A**

R404A is a blend of R125 / R143a / R134a with mass percentages of 44% / 52% / 4% having a molar mass of 97.60 kJ/kg. Although this fluid is a mixture, its properties are well-represented by the equation of state developed by Lemmon, as described in:

E. Lemmon

"Pseudo-Pure Fluid Equations of State for the Refrigerant Blends R-410A, R-404A,R-507A, and R-407C"

International Journal of Thermophysics, Vol. 24, No. 4, July 2003

The reference state is selected such that specific enthalpy=200 kJ/kg and specific entropy=1.0 kJ/kg-K for saturated liquid at 0°C. The reference state can be changed with the $Reference directive.

Mixtures do not necessarily remain at constant temperature during constant pressure evaporation or condensation. EES will return the bubble point temperature as the temperature corresponding to saturation at x=0 and the dew point temperature corresponding to saturation at x=1 at a specified pressure.

Viscosity values are obtained from the correlation presented in Viscosity of Mixed Refrigerants R404A, R407C, R410A, and R507A, V.Z. Geller, presented at the 8th International Refrigeration Conference at Purdue University, July 25-28, 2000, West Lafayette, IN

Thermal conductivity values are obtained from the following publication.

Geller, Nemzer, and Cheremnykh

"Thermal Conductivity of the Refrigerant Mixtures"

International Journal of Thermophysics, Vol. 22 No. 4 January 2001 pp. 1035-1043

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Note: Versions of EES previous to version 9.342 used a different (and less accurate) equation of state based on a modification of the Martin-Hou equation of state (A.I.Ch.E. Journal, 1:142, 1955) as described by:

Bivens and Yokozeki,

1996 Intl. Conference on Ozone Protection Technologies, Washington, DC and DuPont Suva 410A Technical Information T-410A-ENG.

This older formulation used a different reference state for specific enthalpy and entropy so the values obtained with the current version will appear quite different. However, the differences in enthalpy or entropy between two states are comparable.

Although it is not recommended, access to the older property information can be obtained by using fluid R404A_MH.