500+ Engineering Thermodynamics Solved MCQs

Engineering thermodynamics is a branch of engineering that deals with the study of energy, heat, and their relationship to work and the transfer of energy from one place to another.

It is a fundamental subject that forms the basis of many other branches of engineering, including mechanical, chemical, and electrical engineering. The principles of thermodynamics are used to design engines, power plants, refrigeration systems, and a wide variety of other devices and systems that are essential to modern society. Some of the key concepts in engineering thermodynamics include the laws of thermodynamics, entropy, and the concept of equilibrium.

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .

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351.	When the temperature of a liquid is less than the saturation temperature at the given pressure, the liquid is called compressed liquid.
A.	true
B.	false
Answer» A. true

352.	Which of the following statement is true?
A.	a subcooled liquid is one which is cooled below its saturation temperature at a certain pressure
B.	subcooling is the difference between the saturation temperature and the actual liquid temperature
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

353.	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. to protect reheat tubes

354.	Net Work output of the plant with reheat.
A.	decreases
B.	increases
C.	remains same
D.	none of the mentioned
Answer» B. increases

355.	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. increases

356.	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. 0.2-0.25

357.	What is the most preferable dryness
A.	0.99
B.	0.77
C.	0.66
D.	0.88
Answer» D. 0.88

358.	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. reheat is not used

359.	At critical point, value of Vg-Vf is
A.	two
B.	one
C.	zero
D.	infinity
Answer» C. zero

360.	Above the critical point, the isotherms are continuous curves.
A.	true
B.	false
Answer» A. true

361.	A piston –cylinder device contains 0.06m3 of saturated water vapour at 350 kPa pressure. Determine the temperature and mass of the vapour inside the cylinder.
A.	0.104 kg
B.	0.124 kg
C.	0.134 kg
D.	0.114 kg
Answer» D. 0.114 kg

362.	A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the pressure in the tank.
A.	60.183 kpa
B.	70.183 kpa
C.	80.183 kpa
D.	90.183 kpa
Answer» B. 70.183 kpa

363.	A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the volume of the tank.
A.	1.73 m3
B.	2.73 m3
C.	3.73 m3
D.	4.73 m3
Answer» D. 4.73 m3

364.	An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the quality.
A.	0.127
B.	0.137
C.	0.147
D.	0.157
Answer» D. 0.157

365.	Determine the specific volume of R-134a at 1 MPa and 50°C, using ideal gas equation of state.
A.	0.022325 m3/kg
B.	0.024325 m3/kg
C.	0.025325 m3/kg
D.	0.026325 m3/kg
Answer» B. 0.024325 m3/kg

366.	What is the unit of Heat rate?
A.	kj/kw
B.	kw/kj
C.	kj
D.	kw
Answer» A. kj/kw

367.	Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2
A.	has higher thermal efficiency than the carnot cycle operating between same pressure limits
B.	has lower thermal efficiency than carnot cycle operating between same pressure limits
C.	has same thermal efficiency as carnot cycle operating between same pressure limits
D.	may be more or less depending upon the magnitudes of p1 and p2
Answer» A. has higher thermal efficiency than the carnot cycle operating between same pressure limits

368.	Rankine efficiency of a Steam Power Plant
A.	improves in summer as compared to that in winter
B.	improves in winter as compared to that in summer
C.	is unaffected by climatic conditions
D.	none of the mentioned
Answer» B. improves in winter as compared to that in summer

369.	Rankine cycle comprises of
A.	two isentropic processes and two constant volume processes
B.	two isentropic processes and two constant pressure processes
C.	two isothermal processes and two constant pressure processes
D.	none of the mentioned
Answer» B. two isentropic processes and two constant pressure processes

370.	In Rankine cycle, the work output from the turbine is given by
A.	change of internal energy between inlet and outlet
B.	change of enthalpy between inlet and outlet
C.	change of entropy between inlet and outlet
D.	change of temperature between inlet and outlet
Answer» B. change of enthalpy between inlet and outlet

371.	What is the actual turbine inlet temperature in Rankine cycle?
A.	700c
B.	800c
C.	550c
D.	1150c
Answer» C. 550c

372.	Rankine cycle efficiency of a good Steam Power Plant may be in the range of?
A.	15 to 20%
B.	35 to 45%
C.	70 to 80%
D.	90 to 95%
Answer» B. 35 to 45%

373.	A simple Rankine cycle produces 40 MW of power, 50 MW of process heat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?
A.	50
B.	60
C.	70
D.	80
Answer» B. 60

374.	Why both reheating and regeneration is used together?
A.	the effect of reheat alone on efficiency is very small
B.	regeneration has a marked effect on efficiency
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

375.	Which of the following statement is true?
A.	open heater is also known as contact-type heater
B.	in an open type heater the extracted or bled steam is allowed to mix with the feedwater
C.	in a closed heater, the fluids are not allowed to mix together
D.	all of the mentioned
Answer» D. all of the mentioned

500+ Engineering Thermodynamics Solved MCQs

When the temperature of a liquid is less than the saturation temperature at the given pressure, the liquid is called compressed liquid.

Which of the following statement is true?

Why is the steam not allowed to expand deep into the two phase region before it is taken to reheating?

Net Work output of the plant with reheat.

What is the effect of decrease of reheat pressure on the quality of steam at turbine exhaust?

The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?

What is the most preferable dryness

For pressure ratio = 1, efficiency = 0, then?

At critical point, value of Vg-Vf is

Above the critical point, the isotherms are continuous curves.

A piston –cylinder device contains 0.06m3 of saturated water vapour at 350 kPa pressure. Determine the temperature and mass of the vapour inside the cylinder.

A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the pressure in the tank.

A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapour form, determine the volume of the tank.

An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the quality.

Determine the specific volume of R-134a at 1 MPa and 50°C, using ideal gas equation of state.

What is the unit of Heat rate?

Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2

Rankine efficiency of a Steam Power Plant

Rankine cycle comprises of

In Rankine cycle, the work output from the turbine is given by

What is the actual turbine inlet temperature in Rankine cycle?

Rankine cycle efficiency of a good Steam Power Plant may be in the range of?

A simple Rankine cycle produces 40 MW of power, 50 MW of process heat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?

Why both reheating and regeneration is used together?

Which of the following statement is true?

Which of the following is true for an open heater?

Deaerator is a type of open heater.

Which of the following is true for a closed heater?

The efficiency gain follows the law of diminishing return with the increase in the number of heaters.

Which of the following statement is true?

The corrected gas equation is given by

Which of the following statement is true about the correction terms?

Compressibility factor Z is given by

For an ideal gas, Z has the value

The magnitude of Z at a particular pressure and temperature indicates the extent of deviation of the gas from the ideal gas behaviour.

For the ideal gas equation, what assumptions are made?

When does a real gas obey the ideal gas equation closely?

The real gases deviate from the ideal gas equation when the pressure increases.

Real gases conform more closely with the van der Waals equation of state than the ideal gas equation of state.

What is the pressure of H2 with compressibility 0.6, molar volume 5 liter/mole at 27oC?

3 COMPRESSIBILITY CHART AND ITS USE

What is the pressure of 80 grams of CH4 with compressibility 5, with 10 liter volume at 27oC?

What is the compressibility of neon (molar mass = 20) with density 20 g/liter at 27oC and 100 atm?

90 g glucose is filled in a container at 10 atm, if the volume of container is 2 liter, what is the temperature of glucose (z = 1.5)?

at 1 atm and 27oC?

39 grams of benzene (z = 1.4) is filled in a container of volume 10 liter at 27oC, what is the pressure of container?

Which of the following relation is correct?

Maxwell’s equations consists of equations.

The first TdS equation is

The second TdS equation is

376.	Which of the following is true for an open heater?
A.	it is simple, has low cost and low heat transfer capacity
B.	a pump is required at each heater
C.	both of the mentioned
D.	none of the mentioned
Answer» B. a pump is required at each heater

377.	Deaerator is a type of open heater.
A.	true
B.	false
Answer» A. true

378.	Which of the following is true for a closed heater?
A.	it requires a single pump regardless of the number of heaters
B.	it is costly
C.	both of the mentioned
D.	none of the mentioned
Answer» C. both of the mentioned

379.	The efficiency gain follows the law of diminishing return with the increase in the number of heaters.
A.	true
B.	false
Answer» A. true

380.	Which of the following statement is true?
A.	in some cases, an increase in feedwater temperature may reduce the boiler efficiency
B.	number of heaters are optimized
C.	most often, five points of extraction are used
D.	all of the mentioned
Answer» D. all of the mentioned

381.	The corrected gas equation is given by
A.	(p+a/(v2))(v+b)=rt
B.	(p-a/(v2))(v-b)=rt
C.	(p-a/(v2))(v+b)=rt
D.	(p+a/(v2))(v-b)=rt
Answer» D. (p+a/(v2))(v-b)=rt

382.	Which of the following statement is true about the correction terms?
A.	the coefficient a was introduced to account for the existence of mutual attraction between the molecules
B.	the term a/(v2) is called the force of cohesion
C.	the coefficient b was introduced to account for the volumes of the molecules and is known as co-volume
D.	all of the mentioned
Answer» D. all of the mentioned

383.	Compressibility factor Z is given by
A.	rt/pv
B.	pv/rt
C.	(rt/pv)2
D.	(pv/rt)2
Answer» B. pv/rt

384.	For an ideal gas, Z has the value
A.	0
B.	2
C.	1
D.	infinity
Answer» C. 1

385.	The magnitude of Z at a particular pressure and temperature indicates the extent of deviation of the gas from the ideal gas behaviour.
A.	true
B.	false
Answer» A. true