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WorksheetsTHERMAL ENGINEERING II MCQ (MODEL EXAM - 4)
Total questions: 50
Worksheet time: 50mins
In the context of cogeneration turbine, the thermodynamic process taking place is
expansion
condensation
contraction
both (a) & (c)
The device used for recovering waste heat from the textile drier exhaust
heat wheel
recuperator
economizer
regenerator
Recuperator as a waste heat recovery system is used mainly in a
boiler
reheating furnace
compressor
gas turbine
The Brayton cycle is a characteristic of
steam turbine
petrol engine
gas turbine
none of the above
Power is to be generated from a cement kiln exhaust gas. The applicable type of cogeneration is called
topping cycle
Carnot cycle
bottoming cycle
Brayton cycle
Combined cycle is a combination of
conventional boiler first followed by cogeneration system
Brayton cycle first followed by a standard Rankine cycle
Rankine cycle first followed by a Brayton cycle
extraction in the first portion and then a condensing cycle
A waste heat recovery steam generator is used with
steam turbines
back pressure turbines
gas turbines
condensing turbines
The efficiency of which of the following turbine systems is the highest
condensing
back pressure
double extraction condensing
extraction condensing
Bottoming cycle cogeneration is characterized by
Heat first power later
Only Heat
Power First and Heat Later
Only Power
The heat recovery device in which high conductivity bricks are used for storing heat is
heat pipe
heat pump
thermo compressor
regenerator
A steam turbine, in which a part of the steam after partial expansion, is used for process heating and the remaining steam is further expanded for power generation, is known as
Back pressure turbine
Pass out turbine
Low pressure turbine
Impulse turbine
A turbine is said to have an axial discharge when the steam leaves the blade tip at _________ to the direction of the blade motion.
60°
90°
180°
270°
The isentropic enthalpy drop in moving blade is two-third of the isentropic enthalpy drop in fixed blades of a turbine. The degree of reaction will be
0.4
0.56
0.67
1.67
Degree of reaction is defined as the ratio of
Heat drop in fixed blades to the heat drop in moving blades
Heat drop in moving blades to the heat drop in fixed blades
Heat drop in moving blades to the heat drop in fixed blades plus heat drop in moving blades
Heat drop in fixed blades plus heat drop in moving blades to the heat drop in moving blades
The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.
Same
Less
More
None of these
In an impulse reaction turbine, the pressure drops gradually and continuously over
Fixed blades
Moving blades
Both fixed and moving blades
None of these
In a compound steam engine, the first stage of expansion is carried out in a high pressure cylinder whereas the last expansion is completed in low pressure cylinder. The diameter of high pressure cylinder is _________ the low pressure cylinder.
Equal to
Less than
More than
None of these
Steam turbines may be classified according to
Direction of steam flow
Number of stages
Mode of steam action
All of these
Blading efficiency is also known as
Stage efficiency
Diagram efficiency
Nozzle efficiency
None of these
De-Laval turbines are mostly used
Where low speeds are required
For small power purposes and low speeds
For large power purposes
For small power purposes and high speeds
The critical pressure ratio (p2/p1) is given by
The velocity of steam leaving the nozzle (V) is given by (where K = Nozzle coefficient or nozzle efficiency, and hd = Enthalpy or heat drop during expansion of steam in a nozzle)
V = 44.72 hdk
V = 44.72 khd
V = 44.72 khd
V = 44.72 khd
.The fluid that is vaporized is called the refrigerant
True
False
Another simple method of refrigeration is evaporative cooling.
True
False
The function of evaporator is :
draw the refrigerant from the evaporator through suction valve at low pressure and to force it to the condenser through exhaust valve at high pressure and temperature.
to control the rate of admission of refrigerants to the evaporator.
to condense the refrigerants at saturation temperature from vapour to liquid by transferring its latent heat to the water.
Receive the liquid refrigerants from the condenser through throttle valve and to evaporate it
Define tone of refrigeration
working fluid used in the refrigerator.
the standard unit of the refrigerator.
machine which produces cold.
process of continuous cooling or extraction of heat to below that of the atmosphere from a substance with a help of the external work.
Below are the process in refrigeration system EXCEPT
Compression
Condensation
Power
Evaporation
Below is the main component of refrigeration system EXCEPT:
Compressor
Evaporator
Condenser
Pump
Define refrigeration
It is the process of continuous cooling or extraction of heat to below that of the atmosphere from a substance with a help of the external work.
It is based on the second law of thermodynamics that the heat can made to flow from cold body to a hot body with the help of external source.
used to remove heat from the refrigerated space and reject it to atmosphere.
In what part of a refrigeration system does the refrigerant change from a hot high pressure vapor to a hot high pressure liquid?
Evaporator
Condenser
Liquid line
Suction line
What is Pressure and state of the refrigerant in the suction pipe?
High pressure vapor
Low pressure vapor
Low pressure liquid
High pressure liquid
The performance of a boiler is NOT measured by the
amount of water evaporated per hour
steam produced in kg/h
steam produced in kg/kg of fuel burnt
complete combustion of one kg of fuel per hour
What is done to increase the rate of heat transfer in the Velox boiler?
The boiler is heated up to very high range of temperature
Combustion gases are circulated through tubes with supersonic speed
High grade fuel is made use for the combustion
The size of the boiler is changed as it is flexible
Heat balance in a boiler furnace is improved by sending air to the furnace
At low temperature
At high temperature
Does not depends on temperature
depends on pressure
At which pressure the properties of water and steam become identical
1 bar
273 bar
221 bar
100 bar
What is the function of air preheater?
To increase air temperature by flue gases
To increase water temperature by air
To increase steam temperature by air
To increase air temperature by steam
In a gas power cycle, hot combustion gas having specific heat 0.98 kJ/Kg-K enters the turbine at 25 bar, 1300 K and exits at 1 bar. The ratio of specific heat of the working fluid is 1.3. The isentropic efficiency of the turbine is 92%. The work developed (kJ/kg) by the turbine is
614.44
725.95
667.87
576.82
Which type of steam separator is used for low pressure (<20 bar) boiler?
Cyclone Separator
Baffle Separator
Gravity Separator
Choice of Separator doesn’t depend on boiler pressure
0.641 kg/kg of fuel
0.222 kg/kg of fuel
0.321 kg/kg of fuel
1.641 kg/kg of fuel
when fuel oil with 84.9 % carbon, 11.4 % hydrogen, 3.2 % Sulphur, 0.4 % oxygen and 0.1 % ash by weight is burnt with 20 % excess air, assume complete combustion calculate Total air supplied
6.42 kg/kg of fuel
9.24 kg/kg of fuel
16.72 kg/kg of fuel
19.52 kg/kg of fuel
The heat balance sheet for the boiler shows the
complete account of heat supplied by 1 kg of dry fuel and the heat consumed
moisture present in the fuel
steam formed by combustion of hydrogen per kg of fuel
complete combustion of one kg of fuel
65.6 %
86.5 %
72.5 %
80.6 %
