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Introduction To Refrigerant R407C

Environmental friendly

The Montreal Protocol regulation calls for the phase-out of HCFCs by the year 2030 to prevent the ozone

layer from further depletion. R407C is an environment friendly refrigerant to replace R22. The operating

characteristics of R407C system bears close similarity to that of R22. R407C thermophysical properties such

as pressure-temperature behavior, and heat-transfer characteristic are somewhat similar to the properties of

R22.

Physical Property R407C R22

Molecular Wt (g/mol) 86.2 86.5

Vapor Density (kg/m

) 42.0 44.2

Liquid Density (kg/m

) 1134 1195

Boiling Point (°C)

-37.1 to -44.3 -40.8

Latent Heat Vap (kJ/kg) 245 234

Ozone Depletion Potential 0.00 0.05

Global Warming Potential 1600 1700

R407C characteristics

R407C is a ternary mixture of R32, R125, and R134a with weight composition of 23%, 25% and 52%

respectively. These three components have different vapor pressure and boiling points. R407C liquid and

vapor components have different compositions when the fluid evaporates or condenses. This gives rise to a

temperature glide where the bubble point and dew point are of different temperatures. The effect of glide in

heat exchangers is that as the refrigerant mixture flows through the tubing at constant pressure, the

evaporating temperature will change as the composition of the liquid and vapor phases change. Typically,

the glide for R407C is about 5°C to 10°C. The extend of temperature glide actually varies with the pressure

and composition of components present in the mixture during the leak.

The main concerns for R407C is its zeotropic nature. When leak occurs and only vapor leaks out, the

composition of the refrigerant mixture left in the system will change. Especially, when the system is idle, R32

being the lightest component will leak out more than the other components. What remains in the system will

be of different composition. If the leaked system is subsequently top-up with R407C, the mixture in the

system will varies from the original composition percentage ratio.

This composition shift will slightly affect the system performance. However, study has shown that after a

series of repeated leaks and top-ups, the system capacity drops up to 6%.

Another concern for R407C system is the lubricant used for its compressor. Like all HFC refrigerants, R407C

uses polyol ester oil (POE) as its lubricant. This hydroscopic oil is prone to moisture contamination. Extra

precaution must be taken not to expose the R407C system too long to moist air; as the oil will soak up the

moisture into the system.

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