Compression Temperature:

When a refrigerant gets compressed, there is a hike in the temperature of the refrigerant resulting in the heating of the cylinder walls of the compressor. It necessitates external cooling of the cylinder walls to stop volumetric & material losses. Refrigerants with lowest compression temperatures are therefore better than others.

Volume of Refrigerant Handled Per Ton of Refrigeration:

It should be as small as possible to contain a small size of the compressor. The kind of compressor is determined by this value. For refrigerants as R12, R500, R22 etc., a reciprocating compressor is appropriate. For others as R11 and water, a centrifugal compressor is needed to handle the big volume.