Solve this multiple-choice question and choose the correct option.

Concept/Approach Ideal nozzle expansion is treated as steady-flow, adiabatic, and approximately isentropic, not a complete Rankine cycle (which is a closed power cycle of boiler–turbine/expander–condenser–pump). With wet steam and friction, entropy rises; moisture generally increases (dryness fraction tends to decrease), not increase. Critical pressure is the pressure at the throat when the mass flow is choked (maximum), so the statement about the throat pressure being called critical pressure is correct. Final AnswerThe pressure of steam at the throat is called the critical pressure.

Curioustab

Steam nozzles and flow: identify the correct statement Options describe expansion, frictional effect on dryness fraction, and the definition of critical pressure at the throat. Choose the single correct statement.

Mechanical Engineering Steam Nozzles and Turbines Difficulty: Easy

Choose an option

A

The expansion of steam in a nozzle follows Rankine cycle.
B

The friction in the nozzle increases the dryness fraction of steam.
C

The pressure of steam at the throat is called the critical pressure.
D

All of the above

Answer

Correct Answer: The pressure of steam at the throat is called the critical pressure.

Explanation

Concept/Approach

Ideal nozzle expansion is treated as steady-flow, adiabatic, and approximately isentropic, not a complete Rankine cycle (which is a closed power cycle of boiler–turbine/expander–condenser–pump).
With wet steam and friction, entropy rises; moisture generally increases (dryness fraction tends to decrease), not increase.
Critical pressure is the pressure at the throat when the mass flow is choked (maximum), so the statement about the throat pressure being called critical pressure is correct.

Final AnswerThe pressure of steam at the throat is called the critical pressure.