What is the compression ratio of an ammonia refrigeration system operating at 29 PSIG suction pressure and 180 PSIG discharge pressure?

To determine the compression ratio of an ammonia refrigeration system, you calculate it using the formula:

Compression Ratio = Discharge Pressure / Suction Pressure

In this case, the discharges pressure is 180 PSIG, and the suction pressure is 29 PSIG. Before applying the formula, it’s essential to convert these pressures to absolute values, as the compression ratio must be calculated using absolute pressures:

• Absolute Discharge Pressure = 180 PSIG + 14.7 (approximately, since atmospheric pressure at sea level is around 14.7 PSIA) = 194.7 PSIA

• Absolute Suction Pressure = 29 PSIG + 14.7 = 43.7 PSIA

Now, you can perform the calculation:

Compression Ratio = 194.7 PSIA / 43.7 PSIA ≈ 4.45

When rounded to one decimal place, this results in a compression ratio of approximately 4.5:1.

The choice labeled as D, which corresponds to 4.5:1, accurately reflects this calculated compression ratio. This is crucial in refrigeration systems, as the compression ratio influences system efficiency, performance, and operational characteristics. Understanding this ratio helps operators optimize system designs and