Prediction of ternary azeotropic refrigerants with a simple method

Abstract

Refrigeration systems with azeotropic mixtures can achieve lower energy consumption, higher refrigeration capacity and coefficient of performance than both individual fluids and zeotropic refrigerants. In this paper, a simple method for predicting homogenous ternary azeotropic refrigerants was presented. The Peng-Robinson equation of state combined the Van der Waals mixing rule was proved successfully to represent the vapor + liquid equilibrium behavior of binary system and was employed to describe the ternary mixture phase equilibrium property. One hundred and seventy-one ternary systems were tested and eight azeotropes with six saddle-point azeotropes and two maximum-point azeotropes were found. The Antoine equation was used to correlate the azeotropic pressures and the temperatures, which showed the similar behavior to pure fluids and revealed the reliability of the calculated value. It can be concluded that to form ternary azeotropes in refrigerant mixtures at least two subsystems are azeotropic and if all subsystems are azeotropic, the ternary system is more likely to form ternary azeotrope.