Specific P-V Energy

In adding up to the internal energy (U), the other form of energy exists which is significant in understanding energy transfer systems. This kind of energy is termed as P-V energy since it occurs from the pressure (P) and the volume (V) of a fluid. It is numerically equivalent to PV, the product of pressure and volume. Since energy is termed as the capacity of a system to execute work, a system where pressure and volume are allowed to enlarge performs work on its surroundings. Thus, a fluid under pressure has the capacity to execute work. Within engineering applications, the units P-V energy, also termed as flow energy, are the units of pressure times volume (i.e., pounds-force per square foot times cubic feet), that equivalents foot-pounds force (ft-lbf).

The specific P-V energy of a substance is the P-V energy per unit mass. It equivalents the total P-V divided by the total mass m, or the multiplication of the pressure P and the specific volume ν, and is denoted as Pν.

Here:

P = pressure (lbf/f^t2)

V = volume (ft³)

ν = specific volume (ft³/lbm)

m = mass (lbm)