Studies on viscosity of mixtures of some freon vapours

Abstract

An oscillating disc viscometer is used for the determination of viscosity of Freon?12, Freon?22 and Freon?114 vapours and their binary and ternary mixtures at room temperature and pressure. The viscosity of Freon?12, Freon?22 and Freon?114 vapours has been determined at room temperature and pressure and is found to be within 1% of the published data. The viscosity of three binary mixtures, namely, Freon?12 – Freon?22, Freon?12 – Freon?114 and Freon?22 – Freon?114, and one ternary mixture of Freon?12 – Freon?22 – Freon?114 vapours is determined at room temperature and pressure using the oscillating disc viscometer. The present experimental results for the binary mixtures agree well with the calculated values from Hirschfelder, Curtiss and Bird’s equation, Wilke’s equation, and Heming and Zipperer’s equation; the agreement is within 1.5%. In the case of ternary mixtures, Wilke’s equation predicts values of viscosity which are in good agreement with the experimental values. However, the prediction by Dean and Stiel’s equation for Freons and their binary mixtures does not compare well with the present experimental results. A novel method that enables determination accurately of the masses of the components of gas mixtures and, hence, their mixture composition has been used. This method enables very accurate determination of mixture composition by the direct weighing of the masses of the components as it obviates the need to resort to the equations of state. The force constants and second virial coefficients for pure Freon?12, Freon?22 and Freon?114 vapours have been determined using Lennard?Jones potential to enable prediction of viscosity of these pure vapours and their mixtures by theoretical equations developed from statistical mechanics. The agreement between theoretical and experimental viscosity is good. In the case of ternary mixtures of Freon?12, Freon?22 and Freon?114 vapours, it was found that when the constituents Freon?12 and Freon?114 of the mixture are in inverse ratio, the viscosity of this ternary mixture remains constant irrespective of the percentage of Freon?22 vapour present in the mixture.