Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

A Helmholtz Energy Equation of State for cis-1-Chloro-2,3,3,3-tetrafluoro-1-propene [R-1224yd(Z)]



Ryo Akasaka, Eric W. Lemmon


A fundamental equation of state expressed explicitly in the Helmholtz energy is presented for R-1224yd(Z), an environmentally friendly refrigerant for centrifugal chillers, high-temperature heat pumps, and organic Rankine cycles. The equation of state is based on consistent experimental data for the critical parameters, vapor pressures, saturated liquid and vapor densities, (p, ρ, T) behavior, vapor-phase sound speeds, liquid-phase sound speeds, and ideal-gas isobaric heat capacities. The equation is valid at temperatures from the triple-point temperature (157.8 K) to 473 K and pressures up to 35 MPa. In the valid range, expected relative uncertainties (k = 2) of the equation are 0.04 % for vapor pressures, 0.1 % for saturated liquid densities, 2 % for saturated vapor densities, 0.05 % for liquid densities, 0.3 % for vapor densities, 0.02 % for vapor-phase sound speeds, and 0.04 % for liquid-phase sound speeds, except in the critical region, where more significant uncertainties of up to 2 % are sometimes observed in densities. The equation exhibits reasonable behavior in the critical and extrapolated regions; this is demonstrated by several plots of derived properties over wide ranges of temperature and pressure.
International Journal of Thermophysics


Density · Equation of state · Heat capacity · R-1224yd(Z) · Sound speed · Vapor pressure · Virial coefficient


Akasaka, R. and Lemmon, E. (2023), A Helmholtz Energy Equation of State for cis-1-Chloro-2,3,3,3-tetrafluoro-1-propene [R-1224yd(Z)], International Journal of Thermophysics, [online],, (Accessed June 14, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created November 6, 2023