Thermodynamic work is organized energy transfer associated with a generalized force acting through a generalized displacement. Pressure-volume boundary work is only one work mode.

Common engineering examples include:

• shaft work, transferred by a rotating shaft; if torque $\tau$ and angular speed $\omega$ are steady, the power is $\dot W=\tau\omega$;
• electrical work, transferred by an electric potential difference driving current; for steady voltage $V$ and current $I$, $\dot W=VI$;
• spring work, transferred when a force acts through the displacement of an elastic element;
• pressure-volume work, transferred when a system boundary moves against pressure.

The bookkeeping depends on the system boundary. For a turbine analyzed as a control volume, the rotating shaft crosses the boundary and shaft power is an energy transfer. Mechanical energy already carried by the fluid must not be counted again as shaft work.

For example, a shaft delivering torque $\tau=50\ \mathrm{N,m}$ at angular speed $\omega=100\ \mathrm{rad/s}$ transfers

$$\dot W=50(100)=5000\ \mathrm W=5\ \mathrm{kW}.$$

Identifying the work mode before writing an energy balance prevents the same physical transfer from being counted twice.