High discharge temperature

Question: I've found the Hot Line to be most helpful in answering my questions. I would also like to express my appreciation to Daniel Kramer for answering my questions, which were published in the February 1991 issue.

In one of the answers it states,”HFCF-22 exhibits a high discharge temperature under condition of low evaporating temps.” I don't quite understand why that's the case.

-Brian Hall, Lewiston, NY

Answer: All gases increase in temperature when compressed. Some gases exhibit a greater temperature increase than others when compressed through the same range of saturated pressures, i.e. through the same range of evaporating and condensing temperatures.

For example, if we had a group of open, non-hermetic compressors, each with a different refrigerant, all operating with a 5 ° F saturated suction and all discharge to a water-cooled condenser providing a constant 85 degree condensing temperature; and if we carefully measured the discharge temperature at each compressor we would find the following:

Propane, 97 ° F discharge temperature

CFC-502, 99

CFC-12, 101

HCFC-22, 131

Ammonia, 210

These values were all read directly from the table on page 341 of Section 620-10 (”Characteristics of Refrigerants”) of the Service Applications

-Daniel Kramer P. E., consultant