# 190+ Thermal Engineering 1 Solved MCQs

Chapters

42
45.3k
Chapter: Two Phase System
1.

## For water, at pressures below atmospheric,

A. melting point rises slightly and boiling point drops markedly
B. melting point rises markedly and boiling point drops markedly
C. melting point drops slightly and boiling point drops markedly
D. melting point drops slightly and boiling point drops slightly
Answer» A. melting point rises slightly and boiling point drops markedly
2.

A. 373°K
B. 273.16°K
C. 303°K
D. 0°K.
3.

## The critical pressure at which latent heat of vaporisation is zero is

A. 225.65 kgf/cm2
B. 273 kgf/cm2
C. 100 kgf/cm2
D. 1 kgf/cm2
4.

## The latent heat of steam at pressures greater than atmospheric in comparison to latent heat at atmospheric pressure is

A. less
B. more
C. equal
D. may be less or more depending on temperature
5.

## The saturation temperature of steam with increase in pressure increases

A. linearly
B. rapidly first and then slowly
C. slowly first and then rapidly
D. inversely
Answer» B. rapidly first and then slowly
6.

## Heating of dry steam above saturation temperature is known as

A. enthalpy
B. superheating
C. supersaturation
D. latent heat
7.

## Superheating of steam is done at

A. constant volume
B. constant temperature
C. constant pressure
D. constant entropy
8.

## Sublimation region is the region where

A. solid and vapour phases are in equi-librium
B. solid and liquid phases are in equilibrium
C. liquid and vapour phases are in equilibrium
D. solid, liquid and vapour phases are in equilibrium
Answer» A. solid and vapour phases are in equi-librium
9.

A. 0.2
B. 0.8
C. 1.0
D. 0.6
10.

## If a steam sample is nearly in dry condition, then its dryness fraction can be most accurately determined by

A. throttling calorimeter
B. separating calorimeter
C. combined separating and throttling calorimeter
D. bucket calorimeter
11.

## On Mollier chart, flow through turbine is represented by

A. horizontal straight line
B. vertical straight line
C. straight inclined line
D. curved line
12.

## A wet vapour can be completely specified by

A. pressure only
B. temperature only
C. dryness fraction only
D. pressure and dryness fraction.
Answer» D. pressure and dryness fraction.
13.

## On Millier chart, the constant pressure lines

A. diverge from left to right
B. diverge from right to left
C. are equally spaced throughout
D. first rise up and then fall
Answer» A. diverge from left to right
14.

## On Mollier chart, free expansion, or throttling process from high pressure to atmosphere is represented by

A. horizontal straight line
B. vertical straight line
C. straight inclined line
D. curved line
15.

## The dry saturated steam at very low pressure, (5-10 kg/cm2) when throttled to atmosphere will become

A. wet
B. superheated
C. remain dry satruated
D. dry
16.

## The dry saturated steam at very high pressure (150-200 kg/cm2) when throttled to atmosphere will become

A. wet
B. superheated
C. remain dry saturated
D. dry
17.

## In a throttling process

A. steam temperature remains constant
B. steam pressure remains constant
C. steam enthalpy remains constant
D. steam entropy remains constant
Answer» C. steam enthalpy remains constant
18.

## In a throttling process

A. heat transfer takes place
B. work is done by the expanding steam
C. internal energy of steam changes
D. none of the above.
Answer» D. none of the above.
19.

## The latent heat of steam with increase of pressure

A. remains same
B. increases
C. decreases
D. behaves unpredictably
20.

A. 40%
B. 25%
C. 50%
D. 80%
21.

A. volume
B. pressure
C. entropy
D. enthalpy
22.

## The state of vapour under saturation condition is described by

A. pressure alone
B. temperature alone
C. pressure and temperature
D. pressure and dryness fraction
Answer» D. pressure and dryness fraction
23.

## The increase in pressure

A. lowers the boiling point of a liquid
B. raises the boiling point of a liquid
C. .does not affect the boiling point of a liquid
D. reduces its volume
Answer» B. raises the boiling point of a liquid
24.

## What is a pure substance?

A. homogeneous mixture of two substances of same composition
B. a substance with constant chemical composition throughout its mass
C. both a. and b.
D. none of the above
Answer» B. a substance with constant chemical composition throughout its mass
25.

## A pure substance exists in

A. solid phase
B. liquid phase
C. gaseous phase
D. all of the above
Answer» D. all of the above
26.

## Total heat of a substance is also known as

A. internal energy
B. entropy
C. thermal capacity
D. enthalpy
Chapter: Boilers, Mountings and Accessories
27.

## Equivalent evaporation of water is the evaporation "for a feed water supply at 100°C

A. and its corresponding conversion into dry saturated steam at 100°C and 1.033 kg/cm2
B. and its corresponding conversion into dry steam at desired boiler pressure
C. conversion into steam at atmospheric condition
D. conversion into steam at the same pres-sure at which feed water is supplied
Answer» A. and its corresponding conversion into dry saturated steam at 100°C and 1.033 kg/cm2
28.

## Cochran boiler is a

A. horizontal fire-tube boiler
B. horizontal water-tube boiler
C. veritcal water-tube boiler
D. vertical fire tube boiler
Answer» D. vertical fire tube boiler
29.

## Lancashire 'boiler is a

A. stationary fire tube boiler
B. stationary water tube boiler
C. water tube boiler with natural/forced circulation
D. mobile fire tube boiler
Answer» A. stationary fire tube boiler
30.

A. 1-2 m
B. 1.5-2.5 m
C. 2-3 m
D. 2.5-3.5 m
31.

A. 2-4 m
B. 3-5 m
C. 5-7.5 m
D. 7-9 m
32.

A. one half
B. one third
C. one-fifth
D. two-fifth
33.

## Water tube boilers are those in which

A. flue gases pass through tubes and water around it
B. water passes through the tubes and flue gases around it
C. work is done during adiabatic expansion
D. change in enthalpy
34.

## Lancashire boiler is of

A. stationary fire tube-type
B. horizontal type
C. internally fired type
D. all of the above.
Answer» D. all of the above.
35.

## Fire tube boilers are those in which

A. flue gases pass through tubes and water around it
B. water passes through the tubes and flue gases around it
C. forced circulation takes place
D. tubes are laid vertically
Answer» A. flue gases pass through tubes and water around it
36.

A. zero
B. one
C. two
D. four
37.

## Which of the following is a water tube boiler

A. Lancashire boiler
B. Cochran boiler
C. Cornish boiler
D. Babcock and Wilcox boiler
Answer» D. Babcock and Wilcox boiler
38.

## The diameter of cylindrical shell of the Lancashire boiler is of the order of

A. 1 to 1.25m
B. 1 to 1.75 m
C. 2 to 4 m
D. 1.75 to 2.75 m
Answer» D. 1.75 to 2.75 m
39.

## A packaged boiler is one in which various parts like firing equipment, fans, feed pumps and automatic controls are

A. supplied by same manufacturer loose and assembled at site
B. supplied mounted on a single base
C. purchased from several parties and packed together at site
D. packaged boiler does not exist
Answer» B. supplied mounted on a single base
40.

A. one-half
B. one-third
C. one-fourth
D. two-fifth.
41.

## The water tubes in a babcock and wilcox boiler are

A. horizontal
B. vertical
C. inclined
D. horizontal and inclined
42.

A. DIN
B. BS
C. ASTM
D. IBR
43.

## The difference between cornish boiler and lancashire boiler is that

A. former is fire tube type and latter is water tube type boiler
B. former is water tube type and latter is fire tube type
C. former contains one fire tube and latter contains two fire tubes
D. former contains two fire tubes and latter contains one fire tube
Answer» C. former contains one fire tube and latter contains two fire tubes
44.

## A fusible plug is fitted in small boilers in order to

A. avoid excessive build up of pressure
B. avoid explosion
C. extinguish fire if water level in the boiler falls below alarming limit
D. control steam dome
Answer» C. extinguish fire if water level in the boiler falls below alarming limit
45.

## The fusible plug in small boilers is located

A. in the drum
B. in the fire tubes
C. above steam dome
D. over the combustion chamber
Answer» D. over the combustion chamber
46.

A. bismuth
B. copper
C. aluminium
D. nickel
47.

## The ratio of heat utilised to produce steam and the heat liberated in furnace is known as

A. boiler effectiveness
B. boiler evaporative capacity
C. factor of evaporation
D. boiler efficiency.
48.

## It is required to produce large amount of steam at low pressure. Which boiler should be used ?

A. pulverised fuel fired boiler
B. cochran boiler
C. lancashire boiler
D. babcock and wilcox boiler
49.

## Size of boiler tubes is specified by

A. mean diameter and thickness
B. inside diameter and thickness
C. outside diameter and thickness
D. outside diameter and inside diameter
Answer» C. outside diameter and thickness
50.

## The heat loss in a boiler takes place in the form of

A. heat carried away by flue gases
B. heat carried away by ash
D. all of the above.
Answer» D. all of the above.
51.

A. 2 cm
B. 6 Cm
C. 8 cm
D. 12 cm
52.

## In a recuperative air preheater, the heat is transferred

A. from a metal wall from one medium to another
B. from heating an itermediate material and then heating the air from this material
C. by direct mixing ,
D. heat is tr
53.

## The function of injector used in small capacity boilers is to

A. create vacuum
B. inject chemical solution in feed pump
C. pump water, similar to boiler feed pump
D. add make up water in the system
Answer» C. pump water, similar to boiler feed pump
54.

## The maximum discharge through a chimney occurs when the height of chimney is

A. infinitely long
B. around 200 meters
C. equal to the height of the hot gas column producing draught
D. outside temperature is very low
Answer» C. equal to the height of the hot gas column producing draught
55.

## The economiser is used in boilers to

A. increase thermal efficiency of boiler
B. economise on fuel
C. extract heat from the exhaust flue gases
D. increase flue gas temperature
Answer» A. increase thermal efficiency of boiler
56.

## An economiser in a boiler

A. increases steam pressure
B. increases steam flow
C. decreases fuel consumption
D. decreases steam pressure
57.

## The safety valve on boiler drum compared to safety valve on superheater is set at

A. same value
B. higher value
C. lower value
D. lower/higher depending on steam flow
58.

## The capacity of induced draft fan compared to forced draft fan in a boiler is

A. same
B. more
C. less
D. less or more depending on size of boiler
59.

## Evaporative capacity of boiler is expressed as

A. kg of steam produced
B. steam pressure produced
C. kg of fuel fired
D. kg of steam produced per kg of fuel fired
Answer» D. kg of steam produced per kg of fuel fired
60.

A. dry
B. wet
C. saturated
D. superheated.
61.

## The balanced draft furnace is one using

A. induced draft fan and chimney
B. induced draft fan and forced draft fan
C. forced draft fan and chimney
D. any one of the above
Answer» B. induced draft fan and forced draft fan
62.

A. 1 kg/cm
B. 6 kg/cm
C. 17 kg/cm2
D. 100 kg/cm2
63.

## For the same diameter and thickness of tube, a water tube boiler compared to a fire tube boiler has

A. more heating surface
B. less heating surface
C. equal heating surface
D. heating surface depends on other parameters
64.

## The feed check valve is used in order to

A. regulate flow of boiler water
B. check level of water in boiler drum
C. recirculate unwanted feed water
D. allow high pressure feed water to flow to drum and not allow reverse flow to take place
Answer» D. allow high pressure feed water to flow to drum and not allow reverse flow to take place
65.

## Equivalent evaporation is the amount of water evaporated in a boiler from and at

A. 0°C
B. 100°C
C. saturation temperature at given pressure
D. room temperature
66.

## The equivalent evaporation of a boiler is a measure to compare

A. the given boiler with the model
B. the two different boilers of the same make
C. two different makes of boilers operat¬ing under the same operating conditions
D. any type of boilers operating under any conditions.
Answer» D. any type of boilers operating under any conditions.
Chapter: Steam Prime-Movers
67.

## Steam nozzle converts

A. heat energy of steam into pressure energy
B. heat energy of steam into kinetic energy
C. pressure energy of steam into heat energy
D. pressure energy of steam into potential energy
Answer» B. heat energy of steam into kinetic energy
68.

## A nozzle is designed for

A. maximum pressure at the outlet
B. maximum discharge
C. maximum pressure and maximum discharge
D. maximum kinetic energy at the outlet
Answer» D. maximum kinetic energy at the outlet
69.

## Ideal expansion of steam through a nozzle is considered

A. isothermal
C. polytropic
D. none of the above
70.

## Presence of frictional effect during flow through the nozzle

A. reduces the exit velocity
B. increases the exit velocity
C. has no effect on exit velocity
D. none of the above
Answer» A. reduces the exit velocity
71.

## Frictional losses in the nozzle

A. reduces the heat drop
B. increases the heat drop
C. has no effect on heat drop
D. none of the above
Answer» A. reduces the heat drop
72.

## While steam expands in turbines, theoretically the entropy

A. remains constant
B. increases
C. decreases
D. behaves unpredictably
73.

## Nozzle efficiency is defined as

A. ratio of isentropic heat drop to useful heat drop
B. ratio of useful heat drop to isentropic heat drop
C. product of useful heat drop and isentropic heat drop
D. none of the above
Answer» B. ratio of useful heat drop to isentropic heat drop
74.

## When a nozzle operates with maximum mass flow, it is said to be

A. under expanding flow
B. over expanding flow
C. choked flow
D. none of the above
75.

## For supersaturated flow in the nozzle, the discharge

A. increases
B. decreases
C. remains constant
D. none of the above
76.

## For the flow through the convergent and divergent nozzle, whole of friction loss is assumed

A. in the converging portion
B. in the divergent portion
C. between inlet and outlet
D. none of the above
Answer» B. in the divergent portion
77.

## The presence of friction in the nozzle

A. increases the final dryness fraction of steam
B. decreases the final dryness fraction of steam
C. it does not affect the dryness fraction of steam
D. none of the above
Answer» A. increases the final dryness fraction of steam
78.

## When the back pressure of a nozzle is below the critical pressure, the nozzle is said to be

A. under expanding flow
B. over expanding flow
C. choked flow
D. none of the above
79.

## Which ideal process is carried out at the turbine in vapour power cycle?

C. reversible constant pressure heat addition
D. reversible constant pressure heat rejection
80.

## The steam turbines is a

A. rotary machine
B. reciprocating machine
C. rotodynamic machine
D. none of the above
81.

## From inlet to exit of steam nozzle, the pressure

A. increases
B. decreases
C. remains constant
D. none of the above
82.

## From inlet to exit of moving blades in case of impulse turbine, the pressure

A. increases
B. decreases
C. remains constant
D. none of the above
83.

## From inlet to exit of moving blades in case of a reaction turbine, the pressure

A. increases
B. decreases
C. remains constant
D. none of the above
84.

## In an impulse turbine, steam expands

A. in the nozzle only
B. in the moving blades only
C. in the fixed and moving blades
D. none of the above
Answer» A. in the nozzle only
85.

## In a reaction turbine, steam expands

A. in the nozzle only
B. in the moving blades only
C. in the fixed and moving blades
D. none of the above
86.

## A simple impulse turbine consists of

A. one set of nozzles and one set of moving blades
B. two sets of nozzle and one set of moving blades
C. one set each of fixed and moving blades
D. none of the above
Answer» A. one set of nozzles and one set of moving blades
87.

## In a velocity-compounded impulse steam turbine, steam expands in

A. one set of nozzles only
B. more than one set of nozzles
D. none of the above
Answer» A. one set of nozzles only
88.

## In a pressure-compounded impulse steam turbine, steam expands in

A. nozzles and fixed blades only
C. fixed and moving blades both
D. none of the above
89.

## In a pressure-compounded impulse steam turbine, pressure drop over each ring of moving blades

A. remains constant
B. is increasing
C. is decreasing
D. none of the above
90.

## In a pressure-compounded impulse steam turbine, as compared to velocity compounding, the number of stages is

A. less
B. more
C. same
D. none of the above
Chapter: Steam Condenser and Cooling Towers
91.

## The condensation of steam in a condenser takes place at

A. constant pressure
B. constant temperature
C. constant pressure and constant temperature
D. none of the above
Answer» C. constant pressure and constant temperature
92.

## During condensation process, the temperature of the condensing fluid

A. remains constant
B. decreases
C. increases
D. none of the above
93.

## The function of a condenser in a steam power plant is

A. to reduce back pressure
B. to condense the exhaust steam
C. to reduce specific volume of fluid
D. all of the above
Answer» D. all of the above
94.

## In a high-level jet condenser, the condenser shell is installed at a height of

A. more than 5.5 m
B. more than 10.33 m
C. less than 10.33 m
D. none of the above
Answer» B. more than 10.33 m
95.

## The surface condensers are preferred in steam power plant, because

A. they require less coolant
B. condensate can be reused
C. they are more efficient
D. none of the above
Answer» B. condensate can be reused
96.

## In evaporative condensers, the condensing of steam is achieved

A. by rejecting heat to surrounding air
B. by rejecting heat to coolant
C. by evaporation of some coolant
D. none of the above
Answer» C. by evaporation of some coolant
97.

## Dalton's law of partial pressure, applicable to condensers, states that

A. Pa = Pabs + Psat
B. Psat = Pabs + Pa
C. Pabs = Pa+ Psat
D. none of the above
Answer» C. Pabs = Pa+ Psat
98.

## The absolute pressure in a condenser is given by

A. Pabs = Patm + Pvacuum
B. Pabs = Patm -Pvacuum
C. Pabs = Pvacuum
D. none of the above
Answer» B. Pabs = Patm -Pvacuum
99.

## Air leakage into the condenser reduces

A. turbine output
B. cooling capacity
C. life of condenser
D. all of the above
Answer» D. all of the above
100.

## The vacuum maintained in a condenser depends on

A. pressure of cooling water
B. temperature of cooling water
C. back pressure maintained in the condenser
D. all of the above
Answer» B. temperature of cooling water