At this compression ratio, a compressor designed for a 10:1 ratio would have a tough time surviving. In this example, the suction pressure drops by 10 psia, which doubles the compression ratio. If you are thinking about air conditioning, it is often around 3:1 or 4:1 Using these psia pressures from the examples above, a 10:1 compression ratio is calculatedġ0:1 is a compression ratio commonly found in refrigeration applications. This example uses a low temperature application range, and rounds the 14.7 (atmospheric) to 15. (At 0 psig, the actual reading is 14.7 psia.) 14.7 represents the atmospheric pressure that the manifold gauge already takes into consideration. To convert any gauge pressure to absolute, add 14.7 (or 15 to make it easy) to the pressure reading from a manifold gauge set. As the compression ratio increases, the volumetric efficiency decreases in reciprocating compressors. In that chart that accompanies part one of this series, the left side (Y-axis) represents compression ratios. The compression ratio is the ratio of the absolute discharge pressure (psia) to absolute suction pressure (psia), found using the formula Discharge Pressure Absolute ÷ Suction Pressure Absolute. The volumetric efficiency of a reciprocating (piston) compressor can vary over a wide range, depending on the compressor design and the compression ratio.
What are compression ratios and how do they affect compressors?Īs discussed in the first part of this series, an air conditioning compressor’s re-expansion gas directly affects its volumetric efficiency at different system operating conditions.
PSI COMPRESSION RATIO CALCULATOR SERIES
This is part 2 of a 3 part series on understanding compressor replacements. Understanding Service Compressor Replacements
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