Calculate the compression ratio given a suction pressure of 33 PSIG and a discharge pressure of 181 PSIG.

To calculate the compression ratio in a refrigeration system, you need to determine the ratio between the absolute discharge pressure and the absolute suction pressure. The compression ratio is a key aspect of understanding how efficiently a refrigeration system can operate.

First, it is essential to convert the gauge pressures to absolute pressures. Absolute pressure is calculated by adding the atmospheric pressure (approximately 14.7 PSIA at sea level) to the gauge pressure.

For the given values:

• Suction pressure: 33 PSIG

• Discharge pressure: 181 PSIG

Converting to absolute pressures:

• Suction pressure (absolute) = 33 + 14.7 = 47.7 PSIA

• Discharge pressure (absolute) = 181 + 14.7 = 195.7 PSIA

Now, the compression ratio can be calculated using the formula:

Compression Ratio = Discharge Pressure (absolute) / Suction Pressure (absolute)

Plugging in the values:

Compression Ratio = 195.7 PSIA / 47.7 PSIA ≈ 4.10:1

The result indicates that for every unit of pressure at the suction side, there are approximately 4.10 units of pressure at the discharge side. This