# 439 Thermodynamic MCQ For All Mechanical Exams

376)For a regenerator, coefficient of performance is given by (Q1 is the heat taken from low temperature region and Q2 is the heat given to high temperature region)

1. a) Q1/(Q1-Q2)
2. b) Q2/(Q1-Q2)
3. c) 1- (Q1/Q2)
4. d) 1- (Q2/Q1)

Ans-B

377)Which of the following happens in a reversed Carnot cycle?

1. a) the refrigerant is compressed reversibly and adiabatically
2. b) it is condensed reversibly
3. c) it expands reversibly and adiabatically
4. d) all of the mentioned

Ans-D

378)For a heat pump, coefficient of performance is given by (T1 is the temperature of heat rejection and T2 is the temperature of heat absorption)

1. a) T1/(T1-T2)
2. b) T2/(T1-T2)
3. c) 1- (T1/T2)
4. d) 1- (T2/T1)

Ans-A

379). For a regenerator, coefficient of performance is given by (T1 is the temperature of heat rejection and T2 is the temperature of heat absorption)

1. a) T1/(T1-T2)
2. b) T2/(T1-T2)
3. c) 1- (T1/T2)
4. d) 1- (T2/T1)

Ans-B

380)For the same T1 and T2, COP increases with ____ in temperature difference.

1. a) increase
2. b) decrease
3. c) no change
4. d) none of the mentioned

Ans-B

381)In vapour refrigeration cycle, which of the following is used for expansion?

1. a) expansion engine
2. b) throttling valve or capillary tube
3. c) both of the mentioned
4. d) none of the

Ans-B

382). Which of the following operations occur in a vapour refrigeration cycle?

1. a) compression
2. b) cooling and condensing
3. c) expansion and evaporation
4. d) all of the mentioned

Ans-D

383)Compression can be

1. a) dry compression
2. b) wet compression
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

384)Wet compression is preferred over dry compression.

1. a) true
2. b) false

Ans-B

385). Why is wet compression not preferred?

1. a) the liquid refrigerant can be trapped in the head of cylinder
2. b) this may damage the valves or cylinder head
3. c) liquid refrigerant can wash away the lubricating oil thus accelerating wear
4. d) all of the mentioned

Ans-D

386)In the cooling and condensing, correct sequence of processes is

1. a) desuperheated->condensed->saturated liquid
2. b) desuperheated->saturated liquid->condensed
3. c) condensed->desuperheated->saturated liquid
4. d) saturated liquid->condensed->desuperheated

Ans-A

387)The expansion process is

1. a) isentropic
2. b) reversible
4. d) all of the mentioned

Ans-C

388)The evaporation process is a

1. a) constant volume reversible process
2. b) constant pressure reversible process
3. c) adiabatic throttling process
4. d) reversible adiabatic process

Ans-B

389)The evaporator produces the cooling or refrigerating effect.

1. a) trueKipp
2. b) false

Ans-A

390)In the expansion process, which of the following remains constant?

1. a) work done
2. b) heat supplied
3. c) internal energy
4. d) enthalpy

Ans-D

391)The COP of cycle is given by(Q2=heat absorbed by evaporator and Wc=work done by compressor)

1. a) 1- (Q2/Wc)
2. b) 1- (Wc/Q2)
3. c) Q2/Wc
4. d) Wc/Q2

Ans-C

392)Which of the following is recommended in a refrigeration cycle?

1. a) superheating of vapour
2. b) subcooling of liquid
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

393)Superheating of vapour and subcooling of liquid ____ the refrigerating effect.

1. a) decreases
2. b) increases
3. c) no change
4. d) none of the mentioned

Ans-B

394)A condenser must ____ and then ____ the compressed refrigerant.

1. a) superheat, evaporate
2. b) desuperheat, evaporate
3. c) superheat, condense
4. d) desuperheat, condense

Ans-D

395)Which of the following statement is true for a condenser?

1. a) it can be air-cooled or water-cooled
2. b) small self-contained units use water-cooled condenser
3. c) large installations use air-cooled condenser
4. d) all of the mentioned

Ans-A

396)For an expansion device, which of the following is true?

1. a) it increases the pressure of refrigerant
2. b) it regulates the flow of refrigerant to evaporator
3. c) both of the mentioned
4. d) none of the mentioned

Ans-B

397)Which of the following is a type of expansion device?

1. a) capillary tubes
2. b) throttle valves
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

398)Throttle valves are used in ____

1. a) small units
2. b) larger units
3. c) both of the mentioned
4. d) none of the mentioned

Ans-B

399)Capillary tubes are used in ____

1. a) small units
2. b) larger units
3. c) both of the mentioned
4. d) none of the mentioned

Ans-A

400)When volume flow rate of refrigerant is large, which compressor is used?

1. a) reciprocating
2. b) centrifugal
3. c) rotary
4. d) all of the mentioned

Ans-B

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