Velocity of sound in Perfluoropropane (C3F8), Perfluoroethane (C2F6) and their mixtures

Abstract

The paper summarizes development of the new speed of sound data measuring apparatus with its final target range of temperatures between −20°C and 50°C, pressures up to 2MPa. The research was driven by the demands of the several CERN Large Hadron Collider projects, to investigate the possibility of using mixtures of fluorocarbons in cooling circuits for particle physics applications. A new sonar analyzer, described in detail, has been developed also for the continuous real-time mixture composition measurement and is adopted for speed of sound measurements in the gas phase. Advanced sonar electronics has been developed and it is also aimed at expanding the use of the device, not only for sound velocity measurements in various gases and vapors, but also as a combined binary gas mixture analyzer or leak-checker. Verification measurements were made in pure Perfluoropropane, pure Perfluoroethane, and their mixtures. Measurements covered the temperature range between −15°C and 50°C, pressures up to 0.3MPa for the mixtures containing up to 15% of Perfluoroethane in Perfluoropropane. The NIST REFPROP package has been employed to predict expected values of sound velocity. Such predictions in the form of lookup tables can be later used in the reverse process of composition determination from the measured s in refrigerant mixtures. The instrument has many potential applications, including the analysis of mixtures of hydrocarbons, vapors for semi-conductor manufactures and anesthesia.