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REFRIGERATION HVAC MECHANIC RED SEAL LICENSE EXAM REVIEWER - compressor discharge, suction pressures
PROBLEM
(from sample questions on): https://www.red-seal.ca/
The compression ratio of a refrigeration system is 7:1. If the discharge pressure is 300 psig, what is the suction pressure?
Given
7:1 compression ratio
300 psig discharge pressure (gage)
Unknown
suction pressure
SOLUTION
Cr = Pd abs/Ps abs
Ps abs = Pd abs/Cr
where:
Cr = compression ratio
Pd abs = absolute discharge pressure
Ps abs = absolute suction pressure
Absolute Pressure
= gage pressure
+ 14.7
Pd abs
= 300 psig + 14.7
= 314.7 psia
substituting the values, we get,
Ps abs = 314.7/7
Ps abs = 45 psia
Ps gage = 45 - 14.7
Ps gage = 30.3 psig
Checking
Cr = 314.7/45
Cr = 7
*
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