# 390+ Thermal Engineering 2 Solved MCQs

1.

## Nozzle is used to control direction or characteristics of flow.

A. true
B. false
Explanation: nozzle is used to control the direction and characteristics of flow.
2.

## In fountains the type of nozzle used is

A. none of the mentioned
B. turbulent jet
C. high speed nozzle
D. laminar jet
Explanation: laminar jet nozzle is used to convert the fluid in laminar flow.
3.

## If mach number is less than one then its flow is

A. subsonic flow
B. turbulent flow
C. laminar flow
D. none of the mentioned
Explanation: if m<1 then it is subsonic flow.
4.

## The steam leaves the nozzle at a

A. low pressure and a high velocity
B. high pressure and a high velocity
C. high pressure and a low velocity
D. low pressure and a low velocity
Answer» A. low pressure and a high velocity
Explanation: the steam leaves the nozzle at low pressure & a high velocity as the action of steam is best suited for turbine operations under these conditions.
5.

## When mach number is greater than one the flow is

A. subsonic
B. supersonic
C. laminar
D. none of the mentioned
Explanation: when m>1 the flow is supersonic.
6.

## In rocket engines the amount of expansion in Nozzle determines the

A. exit temperature
B. exit pressure
C. exit temperature & pressure
D. none of the mentioned
Answer» C. exit temperature & pressure
Explanation: when the flow is subsonic, air in nozzle expands isoentropically and hence exit temperature and exit pressure depends on the amount of expansion.
7.

## De-Laval turbine is a

A. multi rotor impulse turbine
B. impulse reaction turbine
C. single rotor impulse turbine
D. none of the mentioned
Answer» C. single rotor impulse turbine
Explanation: a de-laval turbine is a single rotor impulse turbine.
8.

## The Parsons’ reaction turbine has

C. fixed and moving blades of different shape
D. identical fixed and moving blades
Explanation: the parsons’ reaction turbine has identical fixed & moving blades.
9.

## What is the critical pressure ratio for initially wet steam?

A. 0.582
B. 0.546
C. 0.577
D. 0.601
Explanation: the critical pressure ratio for initially wet steam is 0.582.
10.

## The ratio of the useful heat drop to the isentropic heat drop is called

A. condenser efficiency
B. nozzle efficiency
C. vacuum efficiency
D. boiler efficiency
Explanation: the ratio of the useful heat drop to the isentropic heat drop is called nozzle efficiency.
11.

## Rateau turbine is

A. pressure-velocity compounded turbine
B. simple reaction turbine
C. velocity compounded turbine
D. pressure compounded turbine
Explanation: a rateau turbine is a pressure compounded turbine.
12.

## When the cross-section of a nozzle increases continuously from entrance to exit, it is called a

A. convergent-divergent nozzle
B. divergent nozzle
C. convergent nozzle
D. none of the mentioned
Explanation: when the cross-section of a nozzle increases continuously from entrance to exit, it is called a divergent nozzle.
13.

## Aeroderivative engines have pressure ratios

A. greater than 30
B. lesser than 30 and greater than 20
C. greater than 50
D. none of the mentioned
Explanation: higher pressure ratios of greater than 30 are used in aeroderivative engines.
14.

## Aeroderivative engines are larger.

A. true
B. false
Explanation: aeroderivative engines are compact and smaller in size.
15.

## Aeroderivative engines release higher emissions.

A. true
B. false
Explanation: aeroderivative engines are smaller and produce high output as a result of which they release higher emissions.
16.

## Critical pressure ratio is ratios of pressures at discharge.

A. minimum
B. none of the mentioned
C. optimum
D. maximum
Explanation: critical pressure ratio is the ratios of pressure at maximum discharge.
17.

## Ratio of critical pressure to inlet pressure in known as

A. none of the mentioned
B. pressure ratio
C. critical pressure ratio
D. isoentropic pressure ratio
Explanation: ratio of critical pressure to inlet pressure is called as critical pressure ratio.
18.

## In De Laval Nozzle critical pressure ratio is given by (2/y+1)^(y/y-1).

A. true
B. false
Explanation: critical pressure ratio of de laval nozzle is derived theoretically.
19.

## With the increase in pressure, the exit velocity

A. decreases
B. increases
C. same
D. independent
Explanation: pressure is inversely proportional to the velocity. so, with the increase in pressure, the exit velocity decreases. we know that the pressure is equal to force per unit area, this contradicts the above statement.
20.

## The Prandtl Number approximates

A. momentum diffusivity to thermal diffusivity
B. thermal diffusivity to momentum diffusivity
C. shear stress to thermal diffusivity
D. thermal diffusivity to kinematic viscosity
Answer» A. momentum diffusivity to thermal diffusivity
Explanation: the prandtl number is a dimensionless number. it approximates the ratio of momentum diffusivity to thermal diffusivity. it can be expressed as pr = v/ α(1). where α= thermal diffusivity and v= momentum diffusivity.
21.

## Pumps increase

A. pressure
B. velocity
C. momentum
D. heat
Explanation: pumps increase pressure rather than velocity. during the pumping process, a housing is provided for the pumping elements. these parts can change the speed. pumps create a passage way that will squirt the fluid passing through it. thus, pumping increases pressure.
22.

## Which among the following is the formula for volumetric flow rate?

A. q = v/a
B. q = av
C. q = a+v
D. q = a-v
Explanation: volumetric flow rate is given by q= a.v. where v is the flow velocity of the fluid, and a is the area of cross section of the surface. area of a surface is also called as the vector area. thus, the right answer is q = av.
23.

## Which among the following is the formula for mass flow rate?

A. q = m/p
B. q = mp
C. q = m + p
D. q = m – p
Explanation: mass flow rate is given by q=m/p. this is a relation expressed for mass flow rate. when ‘m’ is the mass flow rate.
24.

## Compressible flow mainly deals with

A. solid dynamics
B. liquid dynamics
C. gas dynamics
D. solid and liquid dynamics
Explanation: compressible flow is a branch of fluid mechanics that deals with different
25.

## Which among the following is an assumption of the compressible flow?

A. resistance to flow of object
B. no-slip condition
C. known mass flow rate
D. resistance to flow of heat
Explanation: the related assumption of a compressible fluid flow is no-slip condition. it is assumed that the flow velocity at the solid surface is equal to the velocity of the surface itself. it is in direct consequence with the continuum flow.
26.

## What is Mach number?

A. speed of object * speed of sound
B. speed of object /speed of sound
C. speed of object + speed of sound
D. speed of object- speed of sound
Answer» B. speed of object /speed of sound
Explanation: mach number is defined as the ratio of the speed of an object to the speed of sound. mach number is denoted by ‘m’.
27.

## Which of the following kinetic friction is smaller?

A. limiting friction
B. static friction
C. rolling friction
D. sliding friction
Explanation: the force which comes into play when a body rolls over the surface of another body is called rolling friction. for the same magnitude of a normal reaction, rolling friction is always greater than the sliding friction.
28.

## A mass of 4kg rests on a horizontal plane. The plane is gradually inclined until at an angle θ= 15° with the horizontal, the mass just begins to slide. What is the coefficient of static friction between the block and the surface?

A. 0.814
B. 0.27
C. 1.5
D. 3.5
Explanation: θ = 15° is the angle of response.
29.

## A scooter weighs 120kg f. Brakes are applied so that wheels stop rolling and start skidding. Find the force of friction if the coefficient of friction is 0.4.

A. 60kg f
B. 48kg f
C. 25kg f
D. 32kg f
Explanation: weight of the scooter = 120kg f μ = 0.4
30.

## How is friction due to air reduced?

A. streamlining
B. lubrication
C. by using ball bearings
D. by polishing
Explanation: friction due to air is considerably reduced by streamlining the shape pf the body moving through air. for example, jets have a streamline shape.
31.

## Friction can be increased by

A. using air cushion
B. lubricants
C. using sand
D. using ball bearings
Explanation: by throwing sand the force of friction between the wheels and the track becomes easier. on rainy days, we throw sand on the slippery ground. this increases the friction between our feet and the ground and reduces the chance of slipping.
32.

## When moving along a curved path, he

A. leans inwards
B. leans outwards
C. is still
D. leans sideways
Explanation: when a cyclist goes around a curved path, a centripetal force is required. the force between the tyres and the road is small to provide the necessary centripetal force. that is why a cyclist going around a curve leans inwards because the horizontal component of the normal reaction provides the necessary centripetal force.
33.

## A train has to negotiate a curve of radius 400m. By how much should the putter rail be raised with respect to inner rail for speed of 48 km/h? The distance between the rails is 1m.

A. 0.20m
B. 0.0454m
C. 0.45m
D. 0.020m
Explanation: h = (v2 l)/rg h = 402/32 = 0.0454m.
34.

## When a gas is pushed through a pipe, the gaseous molecules are by the pipe’s walls

A. attracted
B. absorbed
C. deflected
D. dissipated
Explanation: this is because there is no attractive force present in the tube for the process of attraction to occur. also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. a pipe is
35.

## In fluid dynamics, the velocity of the fluid in the stagnation point is

A. zero
B. infinite
C. non-existent
D. negative
Explanation: stagnant point is a point where there is no movement of the fluid. when there is no movement, the velocity will be 0. hence the answer is 0.
36.

## If the speed of sound is much                   than that of the gas, the gas density will stay constant.

A. smaller
B. larger
C. equal to
D. non-existent
Explanation: this is because only with speed of sound is larger, it’ll be able to compensate for the speed of gas. under such situations,
37.

## Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in

A. accelerating
B. decelerating
C. equilibrium
D. exponential increase
Explanation: initially the flow has a velocity. in the stagnant state, the velocity is 0. for this to happen, there should be a deceleration of the velocity. hence, deceleration is the answer.
38.

## To refrain from separation in subsonic nozzles, the expansion angle must not be more than

A. 10 degrees
B. 20 degrees
C. 30 degrees
D. 40 degrees
Explanation: if the angle is more than 10 degrees, there will be a drift amidst the nozzle. at any angle more than 10 degrees, this separation will occur. but the minimum value is 10 degrees. so, the answer is 10 degrees.
39.

## Gas flows through the nozzle from an area of pressure (called the chamber) to one of pressure

A. high, low
B. low, high
C. same, same
D. constant, infinite
Explanation: anything that flows or runs moves from a region of higher value to lower value. we can take the example of any physical parameter like pressure, altitude etc.
40.

## Converging-diverging nozzle is also known as

A. pascal nozzle
B. bernouille’s nozzle
C. toricelli’s nozzle
D. de laval’ nozzle
Explanation: this is because this nozzle was invented by carl de laval. so, it is also named after him. hence de-laval nozzle is the option.
41.

## When the pressure chamber is big, the flow velocities are

A. large
B. negligible
C. constant
D. increasing
Explanation: when the chamber is large, the area is high. velocity is inversely proportional
42.

## For a compressible, ideal gas, mass flow rate depends on parameters such as flow area, pressure, temperature, properties of the gas, and

A. avogardo’s number
B. mach number
C. reynold’s number
D. le-grange’ number
Explanation: mass flow rate should depend on the velocity. here mach number denotes the velocity. so, the mach number gives the right answer.
43.

## Which type of boilers use orifice to control the flow circulation?

A. natural circulation boilers
B. forced convection boilers
C. once-through boilers
D. positive forced circulation boilers
Explanation: in these boilers water is circulated by using an additional pump. these boilers often use orifices to control the flow circulation. orifices are located at the bottom of the tubes that ensure even distribution of flow through water wall tubes. these boilers can generate steam upto about 200 bar.
44.

## What is the advantage of having smaller ratio of water to steam space?

A. steam can be generated at a faster even if the boiler is cold
B. increases the rate of evaporation
C. water is made cyclic, i.e., from boiler drum to water tube and back to drum
D. helps in mobilizing the boiler
Answer» A. steam can be generated at a faster even if the boiler is cold
Explanation: rate of evaporation is more as area of heating surface is more due to presence of large small diameter tubes. due to that smaller water ratio is allowed to steam space where in the steam can be generated as a faster rate even if the boiler is cold. as the rate of evaporation is more, it is preferred in steam power plants for power generation.
45.

## Which are the major types of boilers that are operated in world today?

A. natural circulation boiler
B. forced circulation boiler
C. fire tube boiler
D. once through boiler
Explanation: the once through boiler has higher load response characteristics due to the fact that it does not have drum and has much lower water inventory. many times load change response is dictated by the firing system and its controls rather than the boiler, per-say.
46.

## How many level indicators are there in the water level indicator of a boiler?

A. 1
B. 2
C. 3
D. 4
Explanation: the function of the water level indicator is to indicate the level of water
47.

## What is the function of pressure gauge in the boiler?

A. to indicate steam pressure
B. to indicate water pressure
C. to indicate air pressure
D. to indicate flue gas pressure
Answer» A. to indicate steam pressure
Explanation: the function of the pressure gauge is to indicate the steam pressure inside the boiler drum in bar or in kgf in cm2 or in kn/m2 in gauge pressure. if the boiler is fitted with a superheater, one more pressure gauge fitted to the superheater header indicates the superheated steam pressure at any given instant.
48.

## other than Steam stop valve in the boiler which is the other similar type of valve used?

A. non-reversible valve
B. transient valve
C. reversible valve
D. junction valve
Explanation: stop valve and junction valve are essentially same. conventionally stop valves are smaller in size whereas, junction valves are larger. when the valve is mounted on the top most portion of the steam drum, normally the valve is called junction valve. if it is connected in the steam pipe to regulate the flow of steam, the valve is known as stop valve.
49.

## What is the function of Blow down valve of a boiler?

A. to remove sludge
B. to build sediments
C. to remove flue gas
D. to remove ash
Explanation: blow down valve is also called as blow-off-cock. the function of this valve
50.

## What is the function of fusible plug in the boiler?

A. protect the fire tube
C. to act as a junction switch
D. to maintain pressure
Answer» A. protect the fire tube
Explanation: the function of the fusible plug is to protect the fire tube from burning due to excessive heating. this usually happens when the water level inside the drum becomes too low and the shell and crown plate are directly exposed to steam space.
51.

## What is the function of safety valves in the boiler?

A. to prevent excessive steam pressure
B. to prevent excessive air pressure
C. to prevent water pressure
D. to prevent from rising temperatures
Answer» A. to prevent excessive steam pressure
Explanation: the function of safety valve is to prevent the excessive steam pressure inside the boiler drum exceeding the design
52.

## How many types of safety valves are used in boiler in practice?

A. 1
B. 2
C. 3
D. 4
Explanation: two types of safety valves are used in practice
53.

## What happens due to high temperature of feeds water in the economizer?

A. fuel consumption increases
B. fuel mechanical efficiency increases
C. fuel consumption decreases
D. fuel mechanical efficiency decreases
Explanation: function of the economizer is to recover a portion of heat of the exhaust gases before the flue gases enter the chimney and discharged to the atmosphere. due to the high temperature of feed water, fuel consumption reduces. this increases the overall efficiency of the boiler.
54.

## What is the function of superheater in the boiler?

A. increase the temperature of steam
B. reheat the steam
C. superheat the feed water
D. to heat the fuel gas
Answer» A. increase the temperature of steam
Explanation: function of the superheater is to increase the temperature of steam above its saturation temperature. as heat contained in unit mass of superheated steam is more than dry saturated or wet steam, it is extensively used in steam power plants.
55.

## What is the function Air heater in the boiler?

A. preheat the air before entering the boiler
B. recover the heat from flue gas
C. heating of economizer tubes
D. reheat the gas coming out of economizer
Answer» B. recover the heat from flue gas
Explanation: function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. it is places along the passage of the exhaust flue gases in between the economizer and the chimney.
56.

## What is the function of the feed water pump of a boiler?

A. pump water at high pressure
B. to pump water at lower pressure
C. to pull back the water from boiler
D. to convert steam into water after the boiler process
Answer» A. pump water at high pressure
Explanation: function of feed water pump is to pump water at high pressure to the water space of the boiler drum. there are many types of feed pumps, in which they are
57.

## Rotary pumps are driven by

A. electric motors
B. batteries
C. diesel engines
D. biogas fuel
Explanation: rotary pumps are driven by electric motors. water is pumped due to rotary action of the impeller. rotary pumps are invented by charles c barnes. it is a positive displacement pump. the efficiency of these pumps depends on the percentage of slip to the total quantity displaced.
58.

## Which fuel is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber?

A. charcoal
B. anthracite
C. coke
D. briquette coal
Explanation: coal is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber in the absence of air 500oc to 700oc. during this process the volatile matter is removed from the coal, leaving a dull black color to coke. it is a hard porous structure and smokeless. it contains 85 to 95% carbon. when the bituminous coal is heated between 900oc to 1000oc, hard coke
59.

## Which fuel is produced by powdering low grade coal with high ash content?

A. coke
B. pulverized coal
C. charcoal
D. briquette coal
Explanation: pulverized coal is prepared by powdering low grade coal with high ash content. dry coal is pulverized in pulverizing mills. it burns most efficiently when mixed with air and hence it is used in most of the power plants.
60.

## Which is the correct advantage of solid fuels out of the given option?

A. they have low ignition temperature
B. they produce small amount of smoke
C. they have higher calorific value
D. they do not form any clinker
Answer» A. they have low ignition temperature
Explanation: they have low ignition temperature’. ignition temperature is the minimum temperature at which a substance starts to burn. different fuels have different ignition temperature. some fuels have low ignition temperature and some have high ignition temperature. the fuels that have low ignition temperature are highly inflammable and burn quickly at the spark of fire. while some fuels that have high ignition
61.

## Choose the proper disadvantage of solid fuels out of the given option?

A. they produce lot of smoke
B. they have low ignition temperature
C. they are high in production cost
D. they cannot be easily transported
Answer» A. they produce lot of smoke
Explanation: solid fuels tend to produce lot of smoke because they have large percentage of ash content. they are also brittle in nature and they contain some amount of ash in it when they are in ground. due to their brittleness, it is common nature of solid fuels that they break into pieces while mining and transporting and form ash.
62.

## In what forms are liquid fuels available in nature?

A. light distillate
B. petroleum spirit
C. petroleum naphtha
D. crude petroleum
Explanation: liquid fuels are available in nature in the form of crude petroleum. all commercial liquid fuels are derived from crude petroleum or crude oil. the crude oil, as it comes out from oil wells contains 83- 87% carbon, 10-14% hydrogen and small percentages of sulfur, nitrogen, oxygen and gases containing mainly ethane and methane.
63.

## Name the process used to eliminate impurities present in crude oil?

A. distillation
B. filtration
C. sedimentation
D. coagulation
Explanation: the impurities present in the crude oil are eliminated by the process of refining oil by distillation. it is based on the principle that boiling points of various hydrocarbons increase with an increase in molecular weight and when distilled, the crude oil is separated into gasoline, kerosene, fuel oil or reduced crude oil.
64.

## Which fuel is heavier than petrol but less volatile and it is commonly used as domestic fuel?

A. diesel
B. distilled fuel
C. kerosene
D. alcohol
Explanation: kerosene is heavier than gasoline but less volatile than it. it has a specific gravity ranging from 0.78 to 0.85. it is obtained between 150 to 300oc. it is mainly used in aviation gas turbines as jet
65.

## Which fuel is slightly heavier than kerosene and is produced in petroleum fractions?

A. diesel
B. crude oil
C. gasoline
D. distillate
Explanation: distillate is slightly heavier than kerosene and is used as fuel and
66.

## Which fuel has higher thermodynamic efficiency in liquid fuels?

A. diesel
B. petrol
C. kerosene
D. lpg
Explanation: diesel is heavier than kerosene. it has specific gravity ranging from 0.86 to
67.

## Which liquid fuel has a wider composition than diesel and used in furnaces of oil fired boiler?

A. fuel oil
B. petrol
C. distillate
D. alcohol
Explanation: fuel oil is similar to diesel but has wider composition than diesel. it is used in furnaces of oil fired boilers. broadly speaking, fuel oil is any liquid fuel that is burned in furnace or boiler for the generation of power, except oil is having a flash point of approximately 42oc and oils burned in cotton or wool-wick burners.
68.

## Which is the artificial liquid fuel obtained by fermentation process?

A. fuel oil
B. alcohol
C. distillate
D. kerosene
Explanation: alcohol is an artificial fuel obtained from vegetable matter by fermentation process. it is used in many chemical processes. the first four aliphatic alcohols (methanol, propanol, ethanol and butanol) are of interest as fuels because they can be synthesized chemically or biologically. the general chemical formula for alcohol fuel is cnh2n+1oh.
69.

## Which among the following fuels need excess amount of air for complete combustion?

A. natural fuels
B. liquid fuels
C. gaseous fuels
D. artificial solid fuels
Explanation: artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. they have tendency to form clinkers at high temperatures.
70.

## Which of the following is not a type of steam turbine?

A. impulse turbine
B. reaction turbine
C. pelton wheel turbine
D. axial flow type turbine
Explanation: pelton wheel turbine is a water
71.

## Majority of the turbines are axial flow type.

A. true
B. false
Explanation: in axial flow type turbines the steam flows over the blades in a direction parallel to the axis of the wheel. in radial flow turbines the blades are arranged radially so that the steam enters at the blade tip nearest the axis of the wheel and flows towards the circumference.
72.

## Which turbines are employed for driving alternator at synchronous speed?

A. central station turbine
B. reheating turbine
C. extraction turbine
D. extraction induction turbine
Explanation: central turbines are for driving the alternator at synchronous speed. in reheating turbine steam is returned back to the boiler after partial expansion for superheating and then allowed to expand to back pressure. in extraction turbines steam leaves the turbine casing before the exhaust, for feed water heating.
73.

## Non Condensing steam turbine can also be called as

A. extraction steam turbine
B. back pressure steam turbine
C. impulse steam turbine
D. none of the mentioned
Answer» B. back pressure steam turbine
Explanation: the other name for non condensing turbines is back pressure turbines.
74.

## Steam turbine is classified on basis of

B. exhausting condition
C. type of steam flow
D. all of the mentioned
Answer» D. all of the mentioned
Explanation: steam turbines are classified by type of blades, exhausting condition, type of steam flow, division of steam flow, type of compounding.
75.

## High pressure turbine is a Non-Condensing turbine due to

A. exhaust conditions
B. axial flow of the steam
C. pressure-velocity compounding
D. velocity compounding
Explanation: for high pressure turbines exhaust conditions are controlled by regulating valve which makes them to come under the category of non-condensing turbines.
76.

## Impulse blades are in the shape of

A. rain drop
B. circular
C. half moon
D. none of the mentioned
Explanation: blades used in impulse turbines are half moon shaped because as steam enters the moving blade it pushes the blade forward.
77.

## Astern turbines are used in

A. power generation
B. marine purposes
C. aircraft
D. none of the mentioned
Explanation: astern turbines are those classified based on exhaust conditions and are used for marine purposes.
78.

## Cross compound steam turbines are once used in

A. generation of electricity
B. marine ships
C. automobiles
D. none of the mentioned
Explanation: cross compound turbines are once used in marine ships before two stroke diesel engines.
79.

## When steam reaches turbine blades the type of force responsible for moving turbine blades are

A. axial force
B. shear force
C. longitudinal force
D. none of the mentioned
Explanation: axial force pushes the turbine blade forward and causes movement in turbine blade.
80.

## Multi stage arrangement of turbines is called as

A. impulse turbine
B. reaction turbine
C. compounding
D. none of the mentioned
Explanation: multi stage arrangement of turbines reduces the pressure loss and velocity losses and hence it is called as compounding.
81.

## Compounding efficiency at low speed.

A. decrease
B. increase
C. maximizes
D. none of the mentioned
Explanation: even at low speeds velocity wastage is prevented and hence efficiency is increased.
82.

## In velocity compounded turbines flow passage is from

A. moving blades to fixed nozzles
B. fixed nozzles to moving blades
C. fixed blades to moving nozzles
D. none of the mentioned
Answer» D. none of the mentioned
Explanation: in velocity compounded turbines velocity drop is maintained in stages and hence reducing velocity loses. hence in velocity compounded turbines flow passage is from fixed nozzles to multiple rows of
83.

## A velocity compounded impulse turbine is also called as

A. curtis wheel
B. pressure compounded
C. curtis wheel & pressure compounded
D. none of the mentioned
Explanation: velocity compounded turbines are invented by a scientist called curtis and hence it is named after his name.
84.

## Reaction turbine is also called as

A. impulse turbine
B. curtis wheel
C. parsons turbine
D. none of the mentioned
Explanation: reaction turbine was invented by a scientist names parson and hence it was named after his name.
85.

## A turbine comprising of fixed blades and moving nozzles is called as reaction turbines.

A. true
B. false
Explanation: in reaction turbines the reaction produced when steam hits the turbine is also utilized to produce power output.
86.

## Which of these is not an application of back pressure turbine?

A. desalination of sea water
B. filtration of water
C. process industries
D. petrochemical installations
Explanation: the applications of back pressure turbine are desalination of sea water, process industries, petrochemical installations, district heating and also for driving compressors and feed pumps.
87.

## Pass-out turbines are used in which of these cases?

A. relatively high back pressure
B. small heating requirement
C. only relatively low back pressure
D. both relatively high back pressure and small heating requirement
Answer» D. both relatively high back pressure and small heating requirement
Explanation: pass-out turbines are used in cases of relatively high back pressure and small heating requirements. they are used in cases where a certain quantity of steam is continuously extracted from the turbine at an intermediate stage for heating purposes at the desired temperature and pressure.
88.

## Heat exchangers are classified into how many categories?

A. 1
B. 2
C. 3
D. 4
Explanation: nature of heat exchange process, relative direction of motion of fluid, mechanical design of heat exchange surface and physical state of heat exchanging fluids.
89.

## Based upon the nature of heat exchange process, the heat exchangers are classified into how many categories

A. 1
B. 2
C. 3
D. 4
Explanation: direct contact, regenerators and recuperators.
90.

## Which type of flow arrangement is this?

A. counter flow
B. parallel flow
C. regenerator
D. shell and tube
Explanation: in this type of arrangement, the fluids enter the unit from the same side, flow in the same direction and leave from the same side.
91.

## Which of the following is not an example of recuperators type heat exchanger?

B. condensers
C. chemical factories
D. oil heaters for an aero plane
Explanation: recuperators are not used in chemical factories.
92.

## In how many categories heat exchangers are classified on the basis of direction of flow of fluids?

A. 4 categories
B. 3 categories
C. 2 categories
D. 1 categories
Explanation: parallel, counter and cross flow.
93.

## In how many categories heat exchangers are classified on the basis of physical state of heat exchanging fluids?

A. 1
B. 2
C. 3
D. 4
Explanation: condenser and evaporator.
94.

## Which of the following operations occur in a vapour refrigeration cycle?

A. compression
B. cooling and condensing
C. expansion and evaporation
D. all of the mentioned
Answer» D. all of the mentioned
Explanation: these are the processes which constitute the vapour refrigeration cycle.
95.

## Compression can be

A. dry compression
B. wet compression
C. both of the mentioned
D. none of the mentioned
Answer» C. both of the mentioned
Explanation: dry compression starts with saturated vapour and wet compression starts with wet vapour.
96.

## Wet compression is preferred over dry compression.

A. true
B. false
Explanation: dry compression is always preferred.
97.

## Why is wet compression not preferred?

A. the liquid refrigerant can be trapped in the head of cylinder
B. this may damage the valves or cylinder head
C. liquid refrigerant can wash away the lubricating oil thus accelerating wear
D. all of the mentioned
Answer» D. all of the mentioned
Explanation: these are the reasons why dry compression is preferred over wet compression.
98.

## The expansion process is

A. isentropic
B. reversible
D. all of the mentioned
Explanation: the expansion process is adiabatic but not isentropic and is irreversible.
99.

## The evaporation process is a

A. constant volume reversible process
B. constant pressure reversible process