Category: Objective Questions

Energy Engineering Multiple Choice Questions on “Function of Boilers”.

1. What is the function of boiler?
A. To burn the fuel in a confined closed system with the supply of air
B. To generate steam at varying pressure
C. To generate steam at constant pressure
D. To produce flue gases by burning fuel at a given pressure
View Answer

Answer: C
clarification: Function of boiler is to generate steam at constant pressure as per the process requirement. The steam generated may be nearly dry saturated or superheated steam. Constant pressure in the boiler is maintained by generating the steam equal to the steam flowing out of the boiler.

2. Why single boiler unit per turbine is equipped commonly?
A. For better turbine control
B. To deduce the costs
C. For overcoming losses of power
D. To improve the efficiency

Answer: A
clarification: In modern power plants it is very common to use a single boiler unit per turbine. This leads to simpler piping systems and relatively easier boiler and better boiler control. And also operating is easier when the connection is made in this type.

3. What is the critical average pressure at which the single boiler unit per turbines is designed to handle?
A. 150 bar
B. 220 bar
C. 740 bar
D. 575 bar

Answer: B
clarification: Single boiler per unit turbines is designed to operate at average critical temperature of 220bar. If the boilers are designed to operate above or below the critical pressure, than they are known as super critical boilers are once through boilers. If the boilers are designed to operate below the critical pressure than they are known as sub critical or drum boilers.

4. How can be the plant efficiency of steam power plant is increased?
A. By using high pressure and high temperature steam
B. By equipping ash and flue gas clearance system
C. By maintaining the boiler on daily basis by cleaning the soot and combustion products
D. By using better and efficient type of fuel for combustion

Answer: A
clarification: The plant efficiency can be increased by using high pressure and high temperature steam. This also reduces the cost of electricity production. The development of newer materials permitted the use of higher operating pressure and temperature of the boiler.

5. Which type of boilers is preferred cost wise when the boilers are required to raise less than 30 tonnes of steam?
A. Flued boiler
B. Cornish boiler
C. Butterley boiler
D. Shell boiler

Answer: D
clarification: The use of shell boilers are considered to be cheaper when the boilers are required to raise less than 30 tonnes of steam per hour and at pressures 30bar. Above these limits, i.e. for high pressure and high output, water tube boilers are preferred.

6. What is the temperature at which the steam boilers are capable to withstand?
A. 200^oC
B. 280^oC
C. 540^oC
D. 358^oC

Answer: C
clarification: The modern high pressure boilers have steam capacities of 30 to 650 tonnes/hour and with pressure of upto 160 bar & maximum steam temperature of about 540^oC. Also the furnace shape is not limited to cylindrical form; hence furnace shape can be changed to suit wide range of situations.

7. The _________ may have water circulation either by natural means due to difference in density or by external means.
A. Piping
B. Tubes
C. Furnace
D. Boiler

Answer: D
clarification: The boiler may have a water circulation either by natural means due to difference in density or by external means (forced circulation). All modern high pressure boiler plants use a pump to force the water to circulate through the boiler plant. The use of natural circulation is limited to the subcritical boilers.

8. What increases as steam pressure increases inside a boiler?
A. Force
B. Density
C. Rate of steam conversion
D. Viscosity

Answer: B
clarification: As the steam pressure increases, its density also increases while the corresponding increase in temperature causes density of water to decrease. This makes the pressure difference causing water flow to decrease.

9. What is needed to be increased to increase the heat transfer rate in the boiler?
A. Gas velocities
B. Fuel input
C. Water velocities
D. Air supply

Answer: C
clarification: Water velocity is required to be increased rather than gas velocities to increase the rate of heat transfer rate in the boiler, because a considerable increase in pressure is more easily produced with water than with gas. Hence, for a given output in boiler, smaller diameter tube may be used.

10. In what is water in high pressure boiler circulated through?
A. Conduits
B. Cove
C. Channel
D. Tubes
View Answer

Answer: D
clarification: In high pressure boilers, water is circulated through the tubes. If the flow of water takes place through one continuous tube, there is a large resistance due to friction and also pressure drop will be more. If the flow is arranged through a parallel system of tubing i.e., through several sets of tubes which are arranged parallel pressure loss will be reduced. This also provides better control over the steam quality.

Energy Engineering Multiple Choice Questions on “Hydrology – 1”.

1. How does Hydro power plays important in development of a country?
A. Shows the amount of water power in a country
B. Providing abundant amount of power
C. Providing power at cheap rate
D. Power production by hydro power plant is easier
View Answer

Answer: C
clarification: In the development of a country the hydro power plays a very important role because it provides power at cheapest rates. No raw material is required for the production of power from hydro power plant.

2. How much of the total amount of power developed world wide consists of hydro power plant?
A. 10%
B. 20%
C. 30%
D. 40%
View Answer

Answer: B
clarification: Nearly 20% of the total world’s power is generated using hydro power plants. To countries in the world 90% of the nation’s power requirement is met by hydro power. When compared country wise this amount is very high.

3. Which two countries have vast hydro resources?
A. Hungary and Luxemburg
B. India and china
C. Russia and Nepal
D. Japan and Georgia
View Answer

Answer: C
clarification: Russia and Nepal have vast hydro resources that are to be harnessed. As per the estimation of world power organization, the world hydro potential is roughly 5000GW whereas only 4% of it (200GW) is presently developed.

4. What type of energy does rain falling holds relative to the oceans?
A. Potential energy
B. Kinematic energy
C. Electrical energy
D. Motion energy

Answer: A
clarification: Rain falling on earth surface has potential energy relative to oceans towards which it flows. This energy can be converted into shaft work by hydraulic prime mover and finally into electrical energy. The conversion of this energy takes time.

5. The shaft power developed by the water passing through the prime mover is given by _______
A. P = (frac{mgH}{1000}) × n_o^.
B. P = (frac{mgH}{10}) × n_o^.
C. P = (frac{mgH}{100}) × n_o^.
D. P = (frac{mgH}{n_{o^.}}) × 1000

6. On what does generation of Hydro power depends?
A. Quantity of water available
B. On capacity of turbine
C. Height of head
D. Storage capacity

Answer: A
clarification: Generation of power depends on the quantity of water available. The available head depends upon the selection of site for hydraulic power plant. The site of the power plant is always selected for the highest available head when other things are in favor of site selection.

7. On what does the Quantity of water available at selected site depends?
A. Temperature at the selected site
B. Humidity at selected site
C. Vegetation of the area
D. Hydrological cycle of area

Answer: D
clarification: The quantity of water available at the selected site depends upon the hydrological cycle of nature. The quantity of water available can be determined from the study of rainfall and run off in the area.

8. Capacity of hydraulic plant is dependent on __________
A. Minimum quantity of water available
B. Vegetation of the selected area
C. Maximum quantity of water available
D. Available head
View Answer

Answer: A
clarification: As the availability of water depends on natural phenomenon of rain, the maximum capacity of hydraulic generating plant is usually fixed on the basis of minimum quantity of water available at selected site.

9. What are used to store water during peak periods?
A. Storage drums
B. Canals
C. Sews
D. Storage Reservoirs
View Answer

Answer: D
clarification: The capacity of the hydraulic plant is done on the basis of minimum quantity available. Usually storage reservoirs are constructed for such plants in order to store the water during peak periods of runoff and supply the same during off peak periods of runoff.

10. The evaporation of water from the surfaces and its precipitation is known as ___________
A. Science
B. Infiltration
C. Hydrological cycle
D. Vegetation

Answer: C
clarification: It’s the science which deals with rainfall and runoff. The evaporation of the water from the surfaces of river and oceans and its precipitation on the earth is known as hydrological cycle. This happens in a particular amount of period.

Energy Engineering Multiple Choice Questions on “Flat Plate Collectors”.

1. To how many types are flat plate collectors divided depending on type of heat transfer fluid?
A. 2
B. 3
C. 4
D. 5

Answer: A
clarification: Based on the type of heat transfer fluid, flat plate collectors are divided into two types, they are Liquid Heating Collectors and Air or gas heating collectors. And also happens that all other types of collectors come under these two types.

2. For what purpose are Gas heating collectors used?
A. To trap solar radiance
B. To act as a medium to help in conversion of sunlight to electrical energy
C. Employed as solar air heaters
D. They act as alternate panels in case of failure

Answer: C
clarification: Air or Gas heating collectors are employed as solar air heaters. Solar air heater is a type of system driving outdoor air through a sealed, sun heated collector mounted on an exterior wall or roof, returning the warmed air back to the living space.

3. Liquid heating collectors are mainly used for _________
A. heating water
B. generating electricity
C. cooking
D. trapping sunlight
View Answer

Answer: A
clarification: Liquid heating collectors are mainly used for heating water. A liquid based solar collector is a solar collector that uses sunlight to heat a liquid that is circulating in a solar loop. The fluid in the solar loop may be water, an anti freeze mixture or thermal oil.

4. _______ is a glazing which limits the radiation and convection heat losses.
A. Absorber plate
B. Selective surface
C. Insulation
D. Transparent cover

Answer: D
clarification: A transparent cover is glazing which limits the radiation and heat convection losses. It includes one or more sheets of glass or radiation transmitting plastic film or sheet. The glass itself is always a single pane adding to adding the second reduces the collector efficiency.

5. What are provided to minimize heat loss?
A. Absorber plate
B. Surface plate
C. Insulation
D. Casing
View Answer

Answer: C
clarification: Insulation is provided at the back and sides to minimize heat losses. Fiber glass or styro-foam is used for this purpose. And also most modern collectors use standard insulators such as polyurethane or polyisocynurate.

6. Which part of flat plate collectors is coated in black?
A. Transparent cover
B. Absorber plate
C. Insulation
D. Fins

Answer: B
clarification: Absorber plate is usually metallic or coated in black surface which is used for absorbing radiation energy. The absorber plate’s coating directly affects how efficient the collector is. Coatings always have two rating figures: how much they absorb and how much they emit.

7. The frame which contains all the parts is called __________
A. box
B. plate
C. enclose
D. container

Answer: D
clarification: Container is used to enclose the other components to protect them from weather. These containers are made of extruded aluminum which can be quite heavy and thick for heavy duty collectors. There are some collectors which are enclosed by fiber glass too.

8. In which collector does air flow without any obstruction?
A. Porous absorber plate
B. Non-porous absorber plate
C. Over lapped glass absorber
D. Finned absorber

Answer: B
clarification: In a simple flat plate air collector, commonly known as non-porous absorbers, the air stream flow through the absorber plate without any obstruction. An analysis of black painted solar air collectors in conventional design in which the air flows below the absorber plate has been made.

9. In which absorber matrix material is arranged and the back absorber plate is eliminated?
A. Porous absorber plate
B. Non-porous absorber plate
C. Over lapped glass absorber
D. Finned absorber

Answer: A
clarification: In the porous bed air heater, the matrix material is arranged and the back absorber plate is eliminated. A single glazed porous bed collector with a reflecting honey comb, extending above the porous to just under the glass cover have theoretically examined.

10. Which type of absorber increases the heat transfer area over a simple flat plate absorber of the same capacity?
A. Porous absorber plate
B. Non-porous absorber plate
C. Over lapped glass absorber
D. Finned absorber

Answer: D
clarification: The finned plate absorber increases the heat transfer area over a simple flat absorber of same capacity. A good design of a finned absorber can increase the heat transfer rate. The temperature difference between the absorber plate and air is very low.

11. In which type of absorber plate is the overall flow direction is along the absorber glass plate?
A. Overlapped glass absorber
B. Finned absorber
C. Non-porous absorber plate
D. Porous absorber plate
View Answer

Answer: A
clarification: In overlapped absorber plate, overall flow direction is along the absorber glass plate instead of being across the matrix. Plate and air stream temperature increase gradually along the collector length and across from top to bottom.

12. How is heat loss over come in liquid plate collectors?
A. By insulation
B. By casing
C. By the transparent cover
D. From provided tubes

Answer: A
clarification: Heat is transferred from the absorber plate to a point of use by the circulating fluid via water across the solar heated surface. The heat loss from the surface is prevented by placing thermal insulation of 5 to 10cm thickness behind the absorber plate.

Steam and Gas Turbines Multiple Choice Questions on ” Carnot, Rankine and Reheat Cycle-2″.

1. The cycle of evaporation and rain in nature can be assumed to be a kind of Carnot cycle. If ocean water instead of evaporation are boiled by the heat of Sun at a constant temperature of 100 deg C and the condensation of steam into water droplets within the clouds occur at constant temperature of -20 deg C. Find the thermal efficiency of Carnot cycle of nature?
a) 0.2777
b) 0.3030
c) 0.3333
d) 0.50

Answer: b
Clarification: Carnot thermal efficiency = 1-(Mean temperature of heat addition)/( Mean temperature of heat rejection).

2. How is it advantageous to expand steam at 250 deg C in a turbine as compared to expanding saturated steam in similar turbine?
a) Enhances the thermal efficiency of the cycle
b) Reduces the mechanical damage caused to turbine blades due to wet steam
c) Increases the mean temperature of heat addition
d) All of the mentioned

Answer: d
Clarification: Superheating steam makes expansion within turbine to take place in dry region to a greater extent.

3. In a steam turbine power plant, the boiler feedwater temperature is marked as 30 deg C, ocean as sink with temperature 20 deg C and desired thermal efficiency of the plant is 0.46. Find the temperature of steam entering the turbine?
a) 500degC
b) 505.55degC
c) 507.62degC
d) 509.18degC

Answer: d
Clarification: Mean temperature of heat addition = (Temperature of feedwater + Temperature of steam entering turbine)/2.

4. In a newly developed innovative idea brought up by CSIR in India, gas turbine exhaust gas are being utilized to convert feedwater into steam. Certain data of the experiment are as follows: mass flow rate of exhaust gas = 40 kg/hr, enthalpy of exhaust gas at the time of their exit from gas turbine is 600 kJ/kg, steam turbine output as measured by brake dynamometer = 60 hp-sec, thermal efficiency of steam power plant is 0.25, efficiency of exhaust gas in converting feedwater into steam is taken as 50%. Find the enthalpy of exhaust gas remaining after they generate steam from feedwater?
a) 350.0KJ/Kg
b) 241.2KJ/Kg
c) 112.45KJ/Kg
d) 512.56KJ/Kg

Answer: b
Clarification: Heat added = difference of enthalpies * efficiency of exhaust gas in converting feedwater into steam and then apply thermal efficiency formula for Carnot efficiency.

5. Why does Carnot cycle has maximum efficiency?
a) Since all the processes in Carnot cycle are completely reversible
b) Since only process of expansion and compression are reversible
c) Since only the process of heat addition and heat rejection are reversible
d) Since all processes involved are irreversible

Answer: a
Clarification: All the processes in Carnot cycle are completely reversible.

6. A researcher during an experiment found that mean temperature of heat addition and heat rejection for a steam power plant operating on a Carnot cycle is 127 deg C and 27 deg C respectively. Later, he calculated the thermal efficiency of the steam cycle. Can you predict what was it?
a) 0.20
b) 0.25
c) 0.30
d) 0.35

Answer: b
Clarification: Thermal efficiency of a Carnot cycle is given by (Mean temperature of heat addition-Mean temperature of heat rejection)/(Mean temperature of heat addition).

7. If Carnot cycle has maximum possible thermal efficiency, then why don’t the steam turbine power plants run on Carnot cycle?
a) Because the process of heat addition is at constant temperature
b) As mean temperature of heat addition is quite low in case of Carnot cycle
c) Since work consumed by compressor is approximately equal to work produced by turbine
d) Because boiler can’t be maintained at constant pressure in Carnot cycle

Answer: c
Clarification: As compressor and turbine both work on wet steam, therefore they don’t have significant difference in their work.

8. The mass of coal(lignite) used in boiler of a steam power plant is 20 ton per hour and calorific value of lignite is 13600 KJ/kg. Also, if the entropy of steam entering turbine is 750 J/K and that of feedwater entering the boiler is 550J/K. Find the mean temperature of heat addition?
a) 100 deg C
b) 115 deg C
c) 110 deg C
d) 105 deg C

Answer: d
Clarification: Tmean = Q/(change in entropy).

9. In a solar operated steam power plant, water is converted into steam via solar heat. If the effective area of solar plate is 200m², value of solar constant is 1.362KW per m², efficiency of solar components is 17% and overall thermal efficiency of steam cycle desired is 12%. Find the turbine power output?
a) 45KW
b) 22.46KW
c) 5.55KW
d) 16.54KW

Answer: c
Clarification: Efficiency of steam cycle = (Turbine power output/(solar constant*area*solar efficiency)).

10. A boiler feed pump is used to raise ___________
a) Static pressure of feedwater
b) Dynamic pressure of feedwater
c) Static & Dynamic pressure of feedwater
d) None of the mentioned

Answer: a
Clarification: Since water needs to be brought to boiler pressure and is not in motion.

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