For an ammonia refrigeration system operating at an evaporating temperature of 17°F and condensing temperature of 89°F, what is the compression ratio?

To determine the compression ratio in an ammonia refrigeration system, you need to understand the relationship between the evaporating and condensing pressures, which are related to the temperatures provided.

The compression ratio is calculated as the ratio of the absolute pressure in the condenser to the absolute pressure in the evaporator. First, you need to convert the temperatures (in °F) to absolute temperatures in °R (Rankine) using the formula:

Absolute Temperature (°R) = Temperature (°F) + 459.67

So, for the evaporating temperature of 17°F:

• Absolute Temperature (Evaporator) = 17 + 459.67 = 476.67 °R

And for the condensing temperature of 89°F:

• Absolute Temperature (Condenser) = 89 + 459.67 = 548.67 °R

Next, the saturation pressures corresponding to these temperatures can be found from ammonia refrigerant tables. Typically, at the evaporating temperature of 17°F, the saturation pressure is approximately 4.92 psi, and at the condensing temperature of 89°F, it is approximately 36.7 psi.

Using these saturation pressures, the compression ratio can be calculated as follows:

Compression