What is the compression ratio for an air conditioning compressor operating with a suction pressure of 68 psig and a discharge pressure of 240 psig?

To determine the compression ratio for an air conditioning compressor, you need to calculate the ratio of the absolute discharge pressure to the absolute suction pressure. First, it's essential to convert the given pressures from gauge pressure (psig) to absolute pressure (psia).

Absolute pressure is calculated by adding the atmospheric pressure (approximately 14.7 psi at sea level) to the gauge pressure.

For suction pressure of 68 psig:

• Absolute suction pressure = 68 psig + 14.7 psi = 82.7 psia

For discharge pressure of 240 psig:

• Absolute discharge pressure = 240 psig + 14.7 psi = 254.7 psia

Now, the compression ratio is the absolute discharge pressure divided by the absolute suction pressure:

Compression Ratio = Absolute Discharge Pressure / Absolute Suction Pressure

Compression Ratio = 254.7 psia / 82.7 psia ≈ 3.08

This value rounds to approximately 3:1, confirming that the answer to the question is correct.

Understanding this calculation is crucial in refrigeration mechanics, as the compression ratio directly affects compressor performance, efficiency, and suitability for specific applications.