Studies on viscosity of mixtures of freon-12 and freon 22 vapours

Abstract

The viscosity of pure Freon?12 and Freon?22 vapours, and their mixtures, has been determined using an oscillating?disc viscometer at room temperature and pressure. The results agree well with the published data for the pure Freons. The viscosity of mixtures calculated from Hirschfelder, Curtiss and Bird’s equation, Wilke’s equation, and Herning and Zipperer’s equation shows good agreement with the present experimental values for the mixtures. However, the predictions by Dean and Stiel’s equation for Freons and their mixtures do not compare well with the present experimental results. A novel method that enables accurate determination of the masses of the components of gas mixtures—and hence their mixture composition—has been devised. This method allows direct weighing of the component masses, eliminating the need to use equations of state. The force constants and second virial coefficients for pure Freon?12 and Freon?22 vapours have been determined using the Lennard?Jones potential to enable prediction of viscosity of these pure vapours and their mixtures through theoretical equations developed from statistical mechanics. The agreement between theoretical and experimental viscosity is good. The excess?viscosity concept has been extended to Freon?12 and Freon?22 vapours and their mixtures. It is established that the excess viscosity is a unique function of density for pure components as well as their mixtures. The viscosity of Freon?12 and Freon?22 vapours and their mixtures may be predicted from the excess?viscosity data obtained in this investigation.