Total energy at a point in a flowing system:\nWhich energies are included when considering the total specific energy of a fluid stream at a point?

Introduction / Context:
In the steady-flow energy equation and Bernoulli-like formulations extended to real fluids, the total specific energy of a stream at a point is the sum of several contributions. Recognising all components prevents omissions in pump, turbine, and heat-exchanger calculations.

Given Data / Assumptions:

• Single-phase fluid stream at a defined point in a control volume.
• Negligible chemical reaction or phase change at the point considered.
• Classical thermodynamic definition of properties applies.

Concept / Approach:
Total specific energy e_total typically comprises internal energy u, kinetic energy v^2/2, potential energy gz, and flow (pressure) energy p/ρ. In some texts, enthalpy h = u + p/ρ is used, so e_total = h + v^2/2 + gz. Regardless of representation, all four physical contributions are present.

Step-by-Step Clarification:

Verification / Alternative check:
Steady-flow energy equation per unit mass: h1 + v1^2/2 + g z1 + q_in − w_out = h2 + v2^2/2 + g z2. Here h = u + p/ρ incorporates internal and pressure energies, confirming their inclusion.

Why Other Options Are Wrong:

• Options listing only one or two forms omit necessary contributors.
• Pressure-only or internal-only simplifications are incomplete except in very restricted comparisons that hold other terms constant.

Common Pitfalls:
Forgetting to include elevation head in tall columns; neglecting kinetic terms at high velocities; double-counting p/ρ when using enthalpy versus internal energy.

Final Answer:
all: potential, kinetic, pressure (flow) and internal