If the suction pressure is 60 PSIG and the discharge pressure is 180 PSIG, what is the compression ratio?

The compression ratio of a system can be calculated by taking the ratio of the discharge pressure to the suction pressure. To find this ratio, it’s important to note that we first need to convert the pressures into absolute values because the compression ratio is determined using absolute pressures.

In this case:

• Suction pressure is given as 60 PSIG. To convert to absolute pressure (PSIA), we need to add atmospheric pressure, which is typically around 14.7 PSIA. Therefore, the absolute suction pressure is:

[

60 , \text{PSIG} + 14.7 , \text{PSIA} = 74.7 , \text{PSIA}

]

• The discharge pressure is given as 180 PSIG. Similarly, converting it to absolute pressure gives us:

[

180 , \text{PSIG} + 14.7 , \text{PSIA} = 194.7 , \text{PSIA}

]

Now we can calculate the compression ratio by dividing the absolute discharge pressure by the absolute suction pressure:

[

\text{Compression Ratio} = \frac{\text{Absolute Discharge Pressure}}