Flow Work Calculator

Calculate the specific flow work (P/ρ) — the energy per unit mass required to push fluid across a control volume boundary.

Fluid Mechanics I

Common fluids — click to auto-fill density

Inputs

Pressure (absolute) P (Pa)

Use absolute pressure in energy equations.

Fluid density ρ (kg/m³)

Mass flow rate (optional — for flow work rate) ṁ (kg/s)

If provided, flow work rate Ẇ = ṁ × P/ρ [W] is also shown.

Theory

Specific flow work:

w = P × v = P / ρ [J/kg]

Flow work rate:

Ẇ = ṁ × P/ρ = Q × P [W]

Role in enthalpy:

h = u + P/ρ (specific enthalpy = internal energy + flow work)

Flow work is the work done by the fluid behind a parcel to push it through a control volume boundary against the pressure P. It is not a form of stored energy but a transfer term. In the steady-flow energy equation, flow work + internal energy combine into specific enthalpy h, which is why enthalpy appears naturally in open-system thermodynamics.