Mechanical Engineering MCQs – Analysis Of Steam Engine ( Power Plant Engineering ) MCQs
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Mechanical Engineering MCQs – Analysis Of Steam Engine ( Power Plant Engineering ) MCQs
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Effect of variation of Steam Condition on Thermal Efficiency
1. The cycle efficiency ________________ with the _____________ of condenser pressure.
a) decreases, decrease
b) increases, decrease
c) remains same, decrease
d) does not vary, decrease
Answer: b
Explanation: As the decrease in condenser pressure mainly depends on the available cooling water temperature & thus on the climatic conditions of the place. Hence, cycle efficiency being a function of condenser pressure has an inverse relation with the condenser pressure.
2. What is the relation between cooling water temperature (tc1) & condenser pressure (pc)?
a) tc1 is directly proportional to pc
b) tc1 is directly proportional to 2xpc
c) tc1 is directly proportional to 5xpc
d) tc1 is directly proportional to 6xpc
Answer: a
Explanation: Cooling water temperature is directly proportional to condenser pressure 1xpc.
3. An increase in inlet steam temperature ___________ the heat rate.
a) lowers
b) increases
c) does not have any effect on
d) temperature has no significance in heat rate
Answer: a
Explanation: An increase in inlet steam temperature, i.e. an increase in superheat at constant inlet steam pressure & condenser pressure gives a steady improvement in cycle efficiency & lowers the heat rate due to an increase in the mean temperature of heat addition.
4. What is the effect of increasing superheat at constant inlet steam pressure & condenser pressure on cycle efficiency?
a) Steady decrement in cycle efficiency
b) Steady improvement in cycle efficiency
c) No effect on cycle efficiency
d) None of the mentioned
Answer: b
Explanation: An increase in inlet steam temperature, i.e. an increase in superheat at constant inlet steam pressure & condenser pressure gives a steady improvement in cycle efficiency & lowers the heat rate due to an increase in the mean temperature of heat addition.
5. What is the effect of increasing superheat at constant inlet steam pressure & condenser pressure on mean temperature of heat addition?
a) increases
b) decreases
c) remains same
d) none of the mentioned
Answer: a
Explanation: An increase in inlet steam temperature, i.e. an increase in superheat at constant inlet steam pressure & condenser pressure gives a steady improvement in cycle efficiency & lowers the heat rate due to an increase in the mean temperature of heat addition.
6. What is the effect of increasing steam inlet temperature on turbine internal efficiency?
a) it remains same
b) it increases
c) it decreases
d) none of the mentioned
Answer: b
Explanation: Increasing the inlet steam temperature decreases the wetness of the steam in the later stages of the turbine & improves the turbine efficiency.
7. What is the percentage drop in the ultimate strength of unalloyed steels when the steam temperature is raised from 400-500 degree Centigrade?
a) 20%
b) 30%
c) 40%
d) 60%
Answer: b
Explanation: The ultimate strength of unalloyed steels is 30% when the steam temperatures are in the range 400-500 degree Centigrade. Alloying can increase this strength.
8. Apart from alloying, name a material that is used instead of ferritic steels to increase the ultimate strength of unalloyed steels.
a) Chromium
b) Molybdenum
c) Austenitic steel
d) None of the mentioned
Answer: c
Explanation: The use of Austenitic steels increases the ultimate strength of unalloyed steels at high temperatures. The temperature limits are in the range 538-565 degree Centigrade.
9. Which of these cases will have a higher cycle efficiency?
a) Condenser Pressure = 25 mm of Hg; Cooling Water Temperature = 12 degree Centigrade
b) Condenser Pressure = 50 mm of Hg; Cooling Water Temperature = 27 degree Centigrade
c) Condenser Pressure = 75 mm of Hg; Cooling Water Temperature = 36 degree Centigrade
d) Condenser Pressure = 100 mm of Hg; Cooling Water Temperature = 45 degree Centigrade
Answer: a
Explanation: In identical steam conditions cycle efficiency is inversely proportional to cooling water temperature.
10. For the given values of efficiency, inlet steam pressure and quality of steam, pressure limits can be determined by?
a) Mollier Charts
b) Gantt Charts
c) Mollier & Gantt Charts
d) None of the mentioned
Answer: a
Explanation: The pressure limits can be readily determined by drawing the corresponding expansion line of the turbine om a Mollier Diagram.
Reheating of Steam – 1
1. Why Reheating of steam is used?
a) to increase efficiency
b) to increase work output
c) to increase Turbine Inlet Temperature
d) to reduce amount of fuel used
Answer: b
Explanation: Work output = work done by turbine – work done by compressor.
2. Reheating of steam _____________
a) decreases steam rate
b) increases steam rate
c) no effect on steam rate
d) none of the mentioned
Answer: a
Explanation: Since work output increases the steam rate decreases.
3. Efficiency of cycle will increase due to Reheating if _____________
a) mean temperature of heat addition in boiler is higher than in reheat process
b) mean temperature of heat addition in boiler is lower than in reheat process
c) it will increase without any conditions
d) it will not increase
Answer: a
Explanation: Efficiency = work output / heat supplied, heat supplied is less in this condition only.
4. Why don’t we use more than two reheats?
a) not economical
b) increased mechanical stresses
c) net efficiency is decreased
d) all of the mentioned
Answer: d
Explanation: The mechanical stresses increases in much higher proportion than the pressure because of the prevailing high temperature.
5. The cycle efficiency in a single reheat plant is influenced by _____________
a) pressure at tubine inlet
b) pressure at which steam is reheated
c) temperature at which steam is reheated
d) temperature at tubine inlet
Answer: b
Explanation: The cycle efficiency is a function of the ratio of reheat to initial pressure.
6. The optimum reheat pressure for most of the modern power plants is ___________ of the initial steam pressure.
a) 0.1-0.5
b) 0.2-0.3
c) 0.2-0.25
d) 0.25-0.3
Answer: c
Explanation: In this range of reheat pressure efficiency is maximum.
7. What is the effect of reheat on steam quality?
a) increases
b) decreases
c) does not change
d) depends on several parameters
Answer: a
Explanation: Because this steam is undergoing expansion two times.
8. What should be the dryness fraction at the time of exhaust?
a) 0.88
b) 0.80
c) 0.90
d) 0.75
Answer: a
Explanation: For modern turbines the admissible dryness fraction of exhaust steam (at the turbine exit) should be not less than x = 0.86 to 0.88.
9. Reheat is preferred for the plants having efficiency greater than _____________
a) 150MW
b) 200MW
c) 100MW
d) 250MW
Answer: c
Explanation: For producing power less than this reheat will not be economical.
10. Which one of the following is an advantage of reheat cycle?
a) the size of the Low pressure (LP) turbine blades is reduced because specific volume is reduced by 7 to 8%
b) the reheating reduce 4 to 5% fuel consumption with a corresponding reduction in the fuel handling
c) lower steam pressures and temperatures and less costly materials can be used to obtain the required thermal performance
d) all of the mentioned
Answer: d
Explanation: Reheat increases work output.
Reheating of Steam – 2
1. The product of steam rate & network when the steam rate is expressed in kg/kWh is equal to?
a) 36
b) 360
c) 3600
d) 60
Answer: c
Explanation: The Steam Rate in terms of kJ/kWh is given by the expression,
Steam Rate = (3600/Wnet) kg/kWh.
2. The product of heat rate & efficiency when the heat rate is expressed in kJ/kWh is equal to?
a) 60
b) 36
c) 360
d) 3600
Answer: d
Explanation: The heat rate in terms of kJ/kWh is given by the expression,
Heat Rate = (3600/n) kJ/kWh
where, n = efficiency.
3. What is the effect of reheat pressure on mean temperature of heat addition Tml?
a) Reheat pressure is directly proportional to Tml
b) Reheat pressure is inversely proportional to Tml
c) Reheat pressure is equal to Tml
d) Tml is independent of reheat pressure
Answer: a
Explanation: As cycle efficiency is reduced with a decrease in reheat pressure. Hence, the mean temperature of heat addition also decreases.
4. Why is the steam not allowed to expand deep into the two phase region before it is taken to reheating?
a) to control flow rate
b) to control phase change
c) to protect reheat tubes
d) none of the mentioned
Answer: c
Explanation: The steam is not allowed to expand deep into the two phase region before it is taken to reheating, because the moisture particles in the steam while evaporating would leave behind solid deposits in the form of scale which is difficult to remove. Hence, when the steam expands, the reheat tubes are damaged.
5. Net Work output of the plant __________ with reheat.
a) decreases
b) increases
c) remains same
d) none of the mentioned
Answer: b
Explanation: With reheat, the area under the curve increases in comparison to what it was without reheat. Hence, Net Work output of the plant increases.
6. Which of the following problems are posed by increasing the number of reheats?
a) Cost & Fabrication problems arise
b) Heat transfer problems arise
c) Frictional losses arise
d) None of the mentioned
Answer: a
Explanation: Higher the number of Reheats, still higher steam pressures could be used, but mechanical stresses increase at a higher proportion than the increase in pressure, because of the prevailing high temperature. The cost & fabrication difficulties will also increase.
7. What is the effect of decrease of reheat pressure on the quality of steam at turbine exhaust?
a) decreases
b) increases
c) remains same
d) none of the mentioned
Answer: b
Explanation: For too low a reheat pressure, the exhaust steam may even be in the superheated state which isn’t good.
8. The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?
a) 0.1-0.15
b) 0.2-0.20
c) 0.2-0.25
d) 0.1-0.10
Answer: c
Explanation: The efficiency increases as the reheat pressure is lowered & reaches a peak at a pressure ratio between 0.2-0.25.
9. What is the most preferable dryness fraction of the exhaust steam?
a) 0.99
b) 0.77
c) 0.66
d) 0.88
Answer: d
Explanation: The dryness fraction of the exhaust steam is in the range of 0.86-0.88 for modern turbines.
10. For pressure ratio = 1, efficiency = 0, then?
a) reheat is used
b) reheat is not used
c) only reheat is used
d) none of the mentioned
Answer: b
Explanation: There cannot be any reheat cycle employed when the cycle efficiency is zero and the pressure ratio is equal to 1.
Regeneration – 1
1. What is the basic principle of regeneration?
a) Steam after coming out of condenser is circulated to boiler
b) Steam after coming out of condenser is circulated to turbine
c) Steam after coming out of turbine is circulated to boiler
d) Two stage turbine is used
Answer: b
Explanation: In regeneration steam from condenser is circulated through turbine to increase steam temperature before it enters boiler.
2. Ideal regenerative rankine cycle _______
a) Increases efficiency
b) Increases work output
c) Increases the heat supplied
d) Does not effect efficiency
Answer: a
Explanation: Feedwater is preheated so as to decrease the fuel consumption which increases efficiency.
3. Mean temperature of heat addition is _______ due to Regeneration.
a) Decreases
b) Not effected
c) Increases
d) Varied exponentially
Answer: c
Explanation: Since less heat is required in the boiler so mean temperature of heat addition increases.
4. Name the coolants commonly used for fast breeder reactors?
a) Liquid metal (Na (or) Na K)
b) Helium (He)
c) Carbon dioxide
d) All of the mentioned
Answer: d
Explanation: Liquid metals are commonly used, in some plants He and CO2 are also used.
5. Why trash rack is used?
a) To prevent the entry of debris
b) To prevent steam overflow
c) It is used as an insulter
d) Prevents back flow
Answer: a
Explanation: The trash rack is used to prevent the entry of debris, which might damage the turbine runners and chock up the nozzle of impulse turbine.
6. What is the use of surge tank?
a) To store condensate
b) To prevent surging
c) To provide better regulation of water pressure in the system
d) To prevent chocking
Answer: c
Explanation: The surge tank controls the water when the load on the turbine decreases and supplies water when the load on the turbine increases.
7. What is the function of Fore bay?
a) Temporary water storage
b) Steam passage
c) Water flow in penstock
d) Condensate storage
Answer: a
Explanation: It is temporary water storage when the load on the plant is reduced and provides water for initial increment on increasing load.
8. What is the use of draft tube?
a) To regain kinetic energy
b) To regain potential energy
c) Passage for water
d) Stores energy
Answer: a
Explanation: The draft tube is used to regain the kinetic energy of water coming out of reaction turbine. It enables the reaction turbine to be placed over tailrace level.
9. Is regenerative cycle alone useful?
a) yes
b) no
c) may be
d) depends on other factors
Answer: a
Explanation: Feedwater is preheated so as to decrease fuel consumption which increases efficiency.
10. What is the function of surge tank?
a) Regulation of water pressure
b) Regulation of steam pressure
c) Storage
d) Regulation of lubricants
Answer: a
Explanation: The surge tank controls the water when the load on the turbine decreases and supplies water when the load on the turbine increases
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
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) (Tml)with regeneration is independent of (Tml)without regeneration
b) (Tml)with regeneration > (Tml)without regeneration
c) (Tml)with regeneration < (Tml)without regeneration
d) (Tml)with regeneration = (Tml)without regeneration
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 (Tml) with regeneration & without regeneration is,
(Tml)with regeneration > (Tml)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
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
Answer: d
Explanation: The steam rate in terms of kg/kWh is given by the expression as,
Steam Rate = 3600/(Wt – WP) kg/kWh.
5. The product of cycle efficiency & heat input is given by which of the following relations?
a) Wt – WP
b) Wt x WP
c) Wt / WP
d) none of the mentioned
Answer: a
Explanation: The expression for cycle efficiency n is given by the following expression,
n = (Wt – WP)/(Q1).
6. What is the effect of increase in regeneration on steam rate?
a) decreases
b) remains same
c) increases
d) none of the mentioned
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
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
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
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
Answer: b
Explanation: Net Work output of the ideal regenerative cycle is less & hence, its steam rate will be more.
Regenerative Feedwater Heating
1. In an ideal regenerative cycle, heat input is at?
a) Boiler
b) Turbine
c) Condenser
d) Pump
Answer: a
Explanation: In a regenerative cycle, the heat input is at Boiler (from the flow chart of an ideal regenerative cycle).
2. In an ideal regenerative cycle, heat output is at?
a) Boiler
b) Turbine
c) Condenser
d) Pump
Answer: c
Explanation: In a regenerative cycle, the heat output is at the Condenser (from the flow chart of an ideal regenerative cycle).
3. In an ideal regenerative cycle, the work output is at?
a) Boiler
b) Turbine
c) Condenser
d) Pump
Answer: b
Explanation: In a regenerative cycle, the work output is at the Condenser (from the flow chart of an ideal regenerative cycle).
4. In an ideal regenerative cycle, the work input is at?
a) Boiler
b) Turbine
c) Condenser
d) Pump
Answer: d
Explanation: In a regenerative cycle, the work input is at the Condenser (from the flow chart of an ideal regenerative cycle).
5. What effect does the heating of feedwater by steam ‘bled’ from the turbine has on the Rankine Cycle?
a) it rankinises the Rankine Cycle
b) it carnotinises the Rankine Cycle
c) it reheats the Rankine Cycle
d) none of the mentioned
Answer: b
Explanation: The heating of feedwater by steam ‘bled’ from the turbine, known as regeneration, carnotinises the Rankine cycle.
6. What is the effect of increase in regeneration on steam rate?
a) steam rate increases
b) steam rate decreases
c) steam rate isindependent of regeneration
d) none of the mentioned
Answer: a
Explanation: More steam has to circulate per hour to produce unit shaft output.
7. If h1 & h10 are the enthalpies at the inlet & at the exhaust, s1 & s10 are the enthalpies at the inlet & exhaust, the mean temperature of heat addition, Tml with regeneration is?
a) (h1 + h10)/(s1 + s10)
b) (h1 + h10)/(s1 – s10)
c) (h1 – h10)/(s1 + s10)
d) (h1 – h10)/(s1 – s10)
Answer: d
Explanation: The expression for mean temperature of heat addition is given as,
T = (h1 – h10)/(s1 – s10).
8. If Q represents the heat input, P represents the heat output; the efficiency n in terms of Q & P is given by?
a) n = QP
b) n = (Q-P)/Q
c) n = (P-Q)/Q
d) n = Q/(Q-P)
Answer: b
Explanation: The expression of efficiency in terms of heat input & output is given by,
n = (Q-P)/Q.
9. If q represents the work output, r represents the work input, Q represents the heat input, the efficiency n in terms of q & r is given by?
a) n = (q-r)/Q
b) n = ( q+r)/Q
c) n = (qr)/Q
d) n = (qr x qr)/Q
Answer: a
Explanation: The efficiency in terms of work input, work output & heat input is given by,
n = (q-r)/Q.
10. What is the effect of increase in steam rate on boiler size?
a) boiler size increases
b) boiler size increases
c) boiler size is independent of steam rate
d) none of the mentioned
Answer: a
Explanation: Increase in steam rate increases by regeneration, i.e., more steam has to circulate per hour to produce unit shaft output. Hence, it increases boiler size.
Feedwater Heaters – 1
1. Feedwater heaters are of two types, they are ____________
a) natural and forced
b) saturated and non saturated
c) open and close
d) water driven and steam driven
Answer: c
Explanation: Feedwater heaters are classified by the methods of mixing steam and feedwater.
2. In open feedwater heater __________
a) the extracted steam is allowed to mix with feedwater
b) feedwater flows through tubes and steam is condensed outside
c) steam flows outside tubes and feedwater inside
d) steam flows inside tubes and outside inside
Answer: a
Explanation: In a closed heater, the extracted steam is allowed to mix with feedwater and both leave the heater at a common temperature.
3. Closed heaters are also called __________
a) contact type heater
b) shell and heat exchanger
c) drip heaters
d) shell and tube heater
Answer: b
Explanation: Closed heaters are also called shell and heat exchanger where the feedwater flows through the tubes.
4. Expand TTD?
a) turbine temperature difference
b) total temperature difference
c) terminal temperature difference
d) turbine terminal difference
Answer: c
Explanation: Terminal temperature difference = saturation temperature of bled steam – exit water temperature.
5. The value of TTD varies with __________
a) heater pressure
b) heater temperature
c) turbine inlet temperature
d) independent of all mentioned
Answer: a
Explanation: The value of TTD varies with heater pressure. heaters receiving wet steam, the TTD is positive.
6. Why at least one open heater is used?
a) installed vertically
b) feedwater deaeration
c) less cost
d) increase efficiency
Answer: b
Explanation: The open heater works as a deaerator.
7. What are the advantages of open heater?
a) lower cost
b) high heat transfer capacity
c) high feedwater temperature
d) all of the mentioned
Answer: d
Explanation: Open heaters are cheap as compared to closed heaters, in closed heaters feedwater temperature is not high.
8. What do you mean by heater drip?
a) condensate
b) heater failure
c) extract
d) maximum temperature
Answer: a
Explanation: Saturated water at the steam extraction pressure.
9. Which of the following material can be used as a moderator?
a) Beryllium
b) Graphite
c) Heavy water
d) All of the mentioned
Answer: d
Explanation: A neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235.
10. Closed heaters are __________
a) horizontal
b) vertical
c) inclined
d) depends on the requirement
Answer: d
Explanation: Closed heaters are mostly horizontal. Sometimes, they are made vertical to reduce the floor areas.
Feedwater Heaters – 2
1. Feed water heaters are of how many types?
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: There are two types of feed water heaters-
1) Open Heater
2) Closed Heater.
2. What is the other name of the open heater?
a) shell & tube heat exchangers
b) contact type heaters
c) regenerative heat exchangers
d) closed heaters
Answer: b
Explanation: Open heaters are also known as contact type heaters where the extracted steam is allowed to mix with feedwater & both leave the heater at a common temperature.
3. What is the condition of the fluids in closed heaters?
a) they are separate
b) they are mixed
c) they are partially mixed
d) none of the mentioned
Answer: a
Explanation: The fluids in a closed heater are un-mixed or separated. Closed heaters are heat exchangers.
4. Closed heaters are ______________ heat exchangers.
a) parallel flow
b) shell-and-tube
c) counter flow
d) cross- flow
Answer: b
Explanation: Closed heaters are shell-and-tube heat exchangers where the feedwater flows through the tubes & the extracted steam condenses outside the walls in the shell. The heat released by condensation is transferred through the walls of the tubes.
5. What is the other name of the condensate obtained after condensation in a shell-and-tube heat exchanger type closed heaters?
a) Heater rise
b) Heater fall
c) Heater drip
d) None of the mentioned
Answer: c
Explanation: Closed heaters are shell-and-tube heat exchangers where the feedwater flows through the tubes & the extracted steam condenses outside the walls in the shell. The heat released by condensation is transferred through the walls of the tubes. The condensate sometimes called the heater drip then passes to the next lower level.
6. What is the function of the trap applied to the condensate?
a) the trap stops the condensate fully
b) the trap stops only vapour & allows liquid to pass through it
c) the trap stops only liquid & allows vapour to pass through it
d) none of the mentioned
Answer: b
Explanation: The main function of the trap applied to the flow of condensate is to stop vapour & allow liquid to flow through it.
7. Which of these is the correct expression for terminal temperature difference(TTD)?
a) TTD = saturation temperature of ‘bled’ steam – exit water temperature
b) TTD = saturation temperature of ‘bled’ steam + exit water temperature
c) TTD = saturation temperature of ‘bled’ steam x exit water temperature
d) TTD = saturation temperature of ‘bled’ steam / exit water temperature
Answer: a
Explanation: The expression for terminal temperature difference for a closed heater is given as,
TTD = saturation temperature of ‘bled’ steam – exit water temperature.
8. If terminal temperature difference (TTD) is too small, what will be its impact on plant efficiency?
a) it increases
b) it decreases
c) it remains same
d) none of the mentioned
Answer: a
Explanation: The formula for TTD is given as,
TTD = saturation temperature of ‘bled’ steam – exit water temperature.
9. If plant efficiency is high, what will be its effect on heater size?
a) it remains same
b) it increases
c) it decreases
d) none of the mentioned
Answer: b
Explanation: Too small a value of TTD, it is good for plant efficiency & consequently, this would require a larger heater.
10. When is a drain-cooler used?
a) when the extracted steam upon condensation gets subcooled
b) when the extracted steam upon subcooling gets condensed
c) the extracted stream has no dependence on drain-cooler
d) none of the mentioned
Answer: a
Explanation: When extracted steam gets subcooled upon condensation, a drain cooler may be used.
11. Which of these is a disadvantage of open heater?
a) simplicity
b) lower cost
c) high heat transfer capacity
d) none of the mentioned
Answer: d
Explanation: The disadvantage is the necessity of a pump at each heater to handle the large feedwater stream.
12. Which of the following is not an advantage of an open heater?
a) simplicity
b) lower cost
c) high heat transfer capacity
d) necessity of a pump at each heater to handle the large feedwater stream
Answer: d
Explanation: The disadvantage is the necessity of a pump at each heater to handle the large feedwater stream.
13. The number of pumps required by a closed heater for pumping the main feedwater stream is?
a) 1
b) 2
c) 3
d) 4
Answer: a
Explanation: A closed heater requires only a single pump for the main feedwater stream regardless of the number of heaters.
14. What is the purpose of using open heaters in steam power plants?
a) feedwater purification
b) feedwater esterification
c) feedwater deaeration
d) feedwater carbonisation
Answer: c
Explanation: In most steam power plants, closed heaters are more favored than open heaters & so are used primarily for the purpose of feedwater deaeration.
15. Why are closed heaters sometimes made vertical?
a) to reduce weight of heaters
b) to reduce floor areas for installations
c) to minimize losses due to weight
d) none of the mentioned
Answer: b
Explanation: Closed heaters are mostly horizontal. Sometimes, they are made vertical to reduce the floor areas needed for their installations.