# Power Plant Questions and Answers – Binary Vapour Cycle

This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Binary Vapour Cycle”.

1. Rankine cycle efficiency of a good steam power plant may be in the range of ___________
a) 15 to 20%
b) 35 to 45%
c) 70 to 80%
d) 90 to 95%

Explanation: The efficiency of a Rankine cycle lies in the range of 35-45 percent mostly.

2. Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2 ___________
a) has higher thermal efficiency than the Carnot cycle operating between same pressure limits
b) has lower thermal efficiency than Carnot cycle operating between same pressure limits
c) has same thermal efficiency as Carnot cycle operating between same pressure limits
d) may be more or less depending upon the magnitudes of p1 and p2

Explanation: For two pressure limits, the thermal efficiency of a Rankine cycle is more than that of the Carnot cycle operating between the same pressure difference which is evident in the P-V diagrams of both the cycle.

3. Rankine efficiency of a steam power plant ___________
a) improves in summer as compared to that in winter
b) improves in winter as compared to that in summer
c) is unaffected by climatic conditions
d) none of the mentioned

Explanation: Rankine cycle efficiency depends upon condenser temperature.

4. Rankine cycle comprises of ___________
a) two isentropic processes and two constant volume processes
b) two isentropic processes and two constant pressure processes
c) two isothermal processes and two constant pressure processes
d) none of the mentioned

Explanation: A rankine cycle is a thermodynamic cycle which comprises of two isentropic and two isobaric processes which is a major thermodynamic cycle in various applications.

5. In Rankine cycle the work output from the turbine is given by ___________
a) change of internal energy between inlet and outlet
b) change of enthalpy between inlet and outlet
c) change of entropy between inlet and outlet
d) change of temperature between inlet and outlet

Explanation: The power output from the turbine is given by the change of internal energy between inlet and outlet.

6. Regenerative heating i.e., bleeding steam to reheat feed water to boiler ___________
a) decreases thermal efficiency of the cycle
b) increases thermal efficiency of the cycle
c) does not affect thermal efficiency of the cycle
d) may increase or decrease thermal efficiency of the cycle depending upon the point of extraction of steam

Explanation: Bleeding decreases the thermal efficiency of the cycle as it reheats feed water to the boiler.

7. Regenerative cycle thermal efficiency ___________
a) is always greater than simple Rankine thermal efficiency
b) is greater than simple Rankine cycle thermal efficiency only when steam is bled at particular pressure
c) is same as simple Rankine cycle thermal efficiency
d) is always less than simple Rankine cycle thermal efficiency

Explanation: A regeneration is done to increase the efficiency of a reheat cycle so naturally the efficiency of a regenerative cycle is much more than a Rankine cycle.

8. In a regenerative feed heating cycle, the optimum value of the fraction of steam extracted for feed heating ___________
a) decreases with increase in Rankine cycle efficiency
b) increases with increase in Rankine cycle efficiency
c) is unaffected by increase in Rankine cycle efficiency
d) none of the mentioned

Explanation: In case of regenerative feed heating cycle, the optimum value of the fraction of steam extracted for feed heating decreases with increase in Rankine cycle efficiency. As the efficiency of regenerative cycle is more than the Rankine cycle.

9. In a regenerative feed heating cycle, the greatest economy is affected ___________
a) when steam is extracted from only one suitable point of steam turbine
b) when steam is extracted from several places in different stages of steam turbine
c) when steam is extracted only from the last stage of steam turbine
d) when steam is extracted only from the first stage of steam turbine

Explanation: Steam extraction is an important factor in deciding the economy of a regenerative cycle. The greatest economy is affected when steam is extracted from several places in different stages of steam turbine.

10. What is the maximum percentage gain in Regenerative feed heating cycle thermal efficiency?
a) increases with number of feed heaters increasing
b) decreases with number of feed heaters increasing
c) remains same unaffected by number of feed heaters
d) none of the mentioned

Explanation: In case of regenerative feed heating cycle, the optimum value of the fraction of steam extracted for feed heating decreases with increase in Rankine cycle efficiency. As the efficiency of regenerative cycle is more than the Rankine cycle. Naturally, the maximum percentage gain in regenerative feed heating cycle thermal efficiency increases with number of feed heaters increasing.

Sanfoundry Global Education & Learning Series – Power Plant Engineering.

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