|
|
Observe the relationship between
absolute and gauge pressure.
In thermodynamic analysis, pressure is expressed in pounds per square inch above a perfect vacuum. This is called absolute pressure and is abbreviated psia.
Steam pressure is usually measured in gauge pressure. The units are pounds per square inch gauge or psig. It is a measure of pressure above atmosphere (14.696 psia at sea level). Below atmospheric pressure (0 psig), steam is measured in inches of mercury vacuum.
|
