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Thread: Heat Rejection Factor
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18-04-2007, 08:52 AM #1
Heat Rejection Factor
To do a quick estimate of heat rejection of a refrigeration system, you could guess COP=3.
From that, Qe/(Qc-Qe) = 3
and therefore Qc = Qe (1 + 1/3)
The heat rejection factor = 1.3
But this is incorrect because the COP depends on the cyle temperatures.
The unknown is only the compressor efficiency.
Text book figures for Isentropic efficiency are 0.72 for a recip.
Surely this is not realistic? I would expect the same compressor with a very low suction to have a lower isentropic efficiency.
Has anybody seen a relationship for isentropic efficiency and pressure ratio?