In which component is the energy balance described by w = h1 - h2?

In which component is the energy balance described by w = h1 - h2?

• A. Turbine
• B. Boiler
• C. Condenser
• D. Pump

Answer: (A)

In a steady-flow device where there is no heat transfer and negligible changes in kinetic or potential energy, the shaft work is equal to the drop in specific enthalpy. For a turbine, steam enters with higher enthalpy h1 and leaves with lower enthalpy h2, so the work produced per unit mass is w = h1 − h2. This positive enthalpy drop drives the turbine shaft work. In contrast, a boiler adds heat (Q = h_out − h_in), a condenser removes heat (Q ≈ h_in − h_out with little shaft work), and a pump requires input work that raises enthalpy (w = h2 − h1). Therefore, the relation w = h1 − h2 describes the turbine.

In a steady-flow device where there is no heat transfer and negligible changes in kinetic or potential energy, the shaft work is equal to the drop in specific enthalpy. For a turbine, steam enters with higher enthalpy h1 and leaves with lower enthalpy h2, so the work produced per unit mass is w = h1 − h2. This positive enthalpy drop drives the turbine shaft work. In contrast, a boiler adds heat (Q = h_out − h_in), a condenser removes heat (Q ≈ h_in − h_out with little shaft work), and a pump requires input work that raises enthalpy (w = h2 − h1). Therefore, the relation w = h1 − h2 describes the turbine.