transportarbete

Transportarbete, or flow work, is the portion of energy transfer in thermodynamic systems that is associated with moving mass across a system boundary. It is the work required to create and sustain the volume of fluid that enters or leaves a control volume, and is most commonly expressed as the pressure–volume term pΔV for a simple process or as ṗV̇ dt in continuous processes.

In open systems, energy balance equations account for material flowing in and out, and the energy carried by that mass includes its enthalpy. The specific enthalpy h is defined as h = u + pv, where u is the internal energy, p is pressure, and v is the specific volume. The pv part represents the flow or transport work. Thus, transportarbete is a component of the energy carried by mass flow and is embedded in the enthalpy term that describes energy transfer with moving streams.

Examples include a gas being pushed into a vessel by a compressor or piston, which requires transport work proportional to the external pressure times the change in volume; similarly, pumping a liquid into or out of a system requires flow work to overcome pressure and create the entering or leaving stream. In a turbine or pump, the external work needed to move fluid against a pressure gradient is a manifestation of transportarbete.

Relation to other terms: transportarbete is distinct from heat transfer and from chemical or shaft work. In many formulations, especially for open systems, the pv contribution is consolidated into enthalpy, while the remaining energy terms account for heat and other forms of work.