Thermodynamics (Vapour Power Cycles)

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% .

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.

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 above.

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 above.

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.

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.

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.

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 above.

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.

10. 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 above.

Answers
1. (b) 2. (a) 3. (b) 4. (b) 5. (b) 6. (b) 7. (a) 8. (b) 9. (b) 10. (a).

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