Detection method of the circulating composition in a refrigeration cycle with ternary zeotropic refrigerant mixture R-407C

摘要

A composition sensing circuit (CS circuit) which detects the circulating composition of the ternary zeotropic refrigerant mixture R-407C in a refrigeration cycle has been developed. The CS circuit consists of a heat exchanger, a capillary tube, two temperature detectors and one pressure detector. The circulating composition is calculated from the temperature and pressure in the circuit and the vapor-liquid equilibria for R-32/R-125/R-134a mixtures together with the approximated relation between mass fractions of R-32 and R-125. The experiments were also carried out to evaluate the accuracy of calculation. The results indicated that the difference between the calculated and measured composition was within 1 % for R-32 and R-125 and within 2 % for R-134a in the circulating composition range from 17/20/63 wt% to 29/30/41 wt%. This difference corresponds to less than 0.5℃ in the saturation temperature. This method is therefore applicable to performance stabilization and reliability improvement of the refrigeration cycle with R-407C.