A method to predict the composition of zeotropic refrigerant mixtures circulating in a refrigeration cycle

摘要

A theoretical analysis is developed to predict the composition of zeotropic refrigerant mixtures circulating in a refrigeration cycle. The composition is calculated by considering the composition distribution in the cycle and mass conservation of the each component of the mixtures. The composition distribution in the gas-liquid two-phase region is calculated with an assumption of local equilibrium in each phase. The predicted compositions are also compared with experimental results, which are obtained for R-407C (23wt% R-32/25wt% R-125/52wt% R134a). The theoretical analysis shows that the composition distributions of the more volatile components, R-32 and R-125, in the two-phase regions are lower than the initially charged compositions. As a result, the circulating fractions of R-32 and R-125 are slightly larger than the charged fractions when appropriate amount of refrigerant is charged in the cycle. This difference increases with addition of more refrigerants, which results in the presence of liquid in the accumulator. The theoretical analysis shows good agreement with the experimental results.