General Energy Equation

The conservation of energy principle defines that energy can be neither created nor destroyed. This is equal to the First Law of Thermodynamics that was used to build up the general energy equation in the module on thermodynamics. The equation below is a statement of the general energy equation for an open system.

Q+(U+PE+KE+PV)_in = W+(U+PE+KE+PV)_out +(U+PE+KE+PV)_stored

Here:

Q = heat (Btu)

U = internal energy (Btu)

PE = potential energy (ft-lbf)

KE = kinetic energy (ft-lbf)

P = pressure (lbf/ft²)

V = volume (ft³)

W = work (ft-lbf)