Saturated vapor pressure measurement and fitting analysis of green insulating gas C₄F₇N within the temperature range of 251 to 309 K

Abstract Perfluoroisobutyronitrile (C4F7N) is an environmentally friendly SF6 substitute with excellent insulation performance and safety, which is a focal point in the field of power insulation. This paper employs vapor pressure measuring instruments to gather 59 groups of saturated vapor pressure data of C4F7N within the temperature range of 251 to 309 K. The experimental data are fitted with the Peng Robinson equation, Antoine equation, and the “2.5, 5” Wagner equation. The following deviation analysis of the results reveals that the Wagner equation yields the most optimal fitting performance, with the absolute, relative, and average deviation percentages of ±0.5 kPa, ±0.3%, and 0.095%, respectively. These results fulfill the requisites of engineering design, applied research, and thermodynamic computations.