Azeotrope refrigerant mixtures

Arita, K. Tomizawa, T. Nagakawa, Y. Yoshida, Y. Vapor-liquid equilibrium of the non-azeotropic refrigerant mixture... 

Refrigerant mixtures are divided into two categories, azeotropes and zeotropes. The 500-series refrigerants are classified as azeotropes, since the vapor composition is identical to the Hquid composition at a given pressure. The 400-series refrigerants are classified as zeotropes, because the equiUbrium... 

Refrigerant mixtures fall into two major groups, zeotropes and azeotropes. In zeotropic mixtures, as the name implies, the liquid-vapor phase change does not occur at a constant temperature (at a fixed pressure) as in the case of pure fluids, but over a range of temperatures. Azeotropic mixtures, on the other hand, boil at a single temperature, much as a pure fiuid does. The temperature alteration during phase change is commonly called temperature An intermediate class of... 

HCFC-123, HCFC-124, and HFC-125 have been found to be useful as refrigerants, either individually or as azeotropic mixtures with other components. These compounds can be prepared by contacting hydrogen fluoride and tetrachloroethylene (PCE) (eq 1) with selected catalysts. 

AZEOTROPIC MIXTURE - Example of azeotropic mixture - refrigerant R-502 is mixture consisting of 48.8 percent refrigerant R-22 and 51.2% R-115. The refrigerants do not combine chemically, yet azeotropic mixture provides refrigerant characteristics desired. 

Mixtures of refrigerants are divided into azeotropic mixtures (the 500-series) and nonazeotropic mixtures (i.e., zeotropes) which are assigned the 400-series. These numbers are not related to the principal naming system and can cause confusion ... 

Non-azeotropic mixtures have been utilized in refrigeration systems for several direct and indirect advantages like, enhanced coefficient of performance, lower power consumption, reduced thermal irreversibility, increased chemical stability, improved oil miscibility, varying condensation temperatures and variable capacity refrigeration systems. All these merits offer rich prospects for the use of mixed component working fluids in heat pumps, power cycles and refrigeration systems. 

There are a least three reasons for distilling under pressure. First, high pressure increases the condensing temperature of the volatile amines and ammonia in the distillation overhead and thus eliminates the need for refrigerated condensers. Second, pressure increases the throughput capacity of a given tower diameter. Third, some of the ammonia-amine azeotropes disappear at elevated pressure. Azeotropic mixtures of ammonia-TMA, TMA-MMA, and TMA-DMA were reported in the literature. Extractive distillation is also a viable way to overcome the difficulties of separating the amines. The extractive solvents are selected for their different solubilities of the three amines. 

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