Steam Engine Regeneration - Power Plant Questions and Answers

This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Regeneration – 2”.

1. External Thermal Irreversibility can be removed by which of the following process?
a) Reheat
b) Regeneration
c) Pre-heat
d) None of the mentioned
View Answer

Answer: b
Explanation: In the process of regeneration, energy is exchanged internally between the expanding fluid in the turbine & the compressed fluid before heat addition.

2. When is the relation between mean temperature of heat addition (T) with regeneration & without regeneration?
a) (T_ml)_{with regeneration} is independent of (T_ml)_{without regeneration}
b) (T_ml)_{with regeneration} > (T_ml)_{without regeneration}
c) (T_ml)_{with regeneration} < (T_ml)_{without regeneration}
d) (T_ml)_{with regeneration} = (T_ml)_{without regeneration}
View Answer

Answer: b
Explanation: The efficiency of the regenerative cycle will be higher than that of the Rankine cycle. Hence, the relation between mean temperature of heat addition (T_ml) with regeneration & without regeneration is,
(T_ml)_{with regeneration} > (T_ml)_{without regeneration}.

3. What is the relation between energy gain of feedwater & energy given off by vapour in condensation?
a) energy gain of feedwater > energy given off by vapour in condensation
b) energy gain of feedwater < energy given off by vapour in condensation
c) energy gain of feedwater = energy given off by vapour in condensation
d) none of the mentioned
View Answer

Answer: c
Explanation: Here heaters are assumed to be adequately insulated, & there is no heat gain from or heat loss to, the surrounding.

4. The product of Steam rate & the difference of work done between turbine & pump, when the steam rate is expressed in kg/kWh is equal to?
a) 36
b) 60
c) 360
d) 3600
View Answer

Answer: d
Explanation: The steam rate in terms of kg/kWh is given by the expression as,
Steam Rate = 3600/(W_t – W_P) kg/kWh.

5. The product of cycle efficiency & heat input is given by which of the following relations?
a) W_t – W_P
b) W_t x W_P
c) W_t / W_P
d) none of the mentioned
View Answer

Answer: a
Explanation: The expression for cycle efficiency n is given by the following expression,
n = (W_t – W_P)/(Q₁).

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6. What is the effect of increase in regeneration on steam rate?
a) decreases
b) remains same
c) increases
d) none of the mentioned
View Answer

Answer: c
Explanation: More steam has to circulate per hour to produce unit shaft output.

7. What is the relation between efficiencies of Carnot cycle & the ideal Sterling Engine?
a) Both are equal
b) Carnot cycle efficiency > Efficiency of Sterling Engine
c) Carnot cycle efficiency < Efficiency of Sterling Engine
d) No relation between Carnot cycle efficiency & efficiency of Sterling Engine
View Answer

Answer: a
Explanation: All the heat is added reversibly & all the heat is rejected reversibly. Hence, the efficiency of Carnot Cycle is equal to efficiency of Sterling Engine.

8. Heat transfer taking place in the turbine is?
a) from the vapour to the condensate
b) from the condensate to the vapour
c) no heat transfer
d) none of the mentioned
View Answer

Answer: a
Explanation: Following the Stirling cycle, in the ideal regenerative cycle the condensate after leaving the pump circulates around the turbine casing so that heat is transferred from the vapour expanding in the turbine to the condensate circulating around it.

9. The heat transfer taking place in the turbine is?
a) irreversible
b) reversible
c) irreversible & reversible
d) none of the mentioned
View Answer

Answer: b
Explanation: At each point the temperature of the vapour is only infinitesimally higher than the temperature of the liquid.

10. The relation between the steam rate of ideal regenerative cycle & steam rate of rankine cycle is?
a) steam rate of ideal regenerative cycle = steam rate of rankine cycle
b) steam rate of ideal regenerative cycle > steam rate of rankine cycle
c) steam rate of ideal regenerative cycle < steam rate of rankine cycle
d) no relation
View Answer

Answer: b
Explanation: Net Work output of the ideal regenerative cycle is less & hence, its steam rate will be more.

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