Question

Assertion (A): In a power plant working on a Rankine cycle, the regenerative feed water heating improves the efficiency of the steam turbine.
Reason (R): The regenerative feed water heating raises the average temperature of heat addition in the Rankine cycle.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Regeneration improves efficiency by increasing mean temperature of heat addition.

Answer 1

The Correct Option is A

Concept: In the Rankine cycle, efficiency depends strongly on the temperature at which heat is added. Regenerative feed water heating is a method used to improve thermal efficiency.

Step 1: Understand regenerative feed heating.
In this process:
• Steam is extracted from intermediate stages of the turbine
• This steam is used to preheat the feed water before entering the boiler

Step 2: Effect on cycle efficiency.
Preheating the feed water:
• Reduces the amount of heat required in boiler
• Increases the mean temperature of heat addition

Step 3: Thermodynamic reasoning.
From Carnot principle: \[ \eta \propto \text{Higher average temperature of heat addition} \] Thus efficiency improves.

Step 4: Evaluate Assertion (A).
Regeneration improves efficiency → Correct.

Step 5: Evaluate Reason (R).
It raises average temperature of heat addition → Correct.

Step 6: Logical connection.
Reason directly explains why efficiency increases. Final Answer: \[ \boxed{\text{Both (A) and (R) are correct and (R) explains (A)}} \]