What type of pressure does “psia” refer to for refrigerant R717?

The designation "psia" refers to absolute pressure, which is the total pressure measured from a perfect vacuum. This measurement includes atmospheric pressure, meaning that it indicates the actual pressure exerted by the refrigerant R717 in a system, without any reductions that gauge pressure would apply by excluding atmospheric pressure.

In refrigeration systems, accurate pressure measurements are critical for operational efficiency, safety, and regulatory compliance. For R717, which is ammonia and used in many industrial refrigeration applications, knowing the absolute pressure helps in determining its state and behavior under various conditions.

Understanding the distinction between absolute pressure and other types of pressure measurements like gauge pressure, which is referenced to atmospheric pressure, is vital for operating refrigeration systems effectively.