439 Thermodynamic MCQ For All Mechanical Exams

401)Which of the following statement is true?

  1. a) rotary compressors are mostly used for small units
  2. b) reciprocating compressors are employed in plants with capacity up to 100 tonnes
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

402)In reciprocating compressors, actual volume of gas drawn in cylinder is ____ the volume displaced by piston.

  1. a) less than
  2. b) more than
  3. c) equal to
  4. d) none of the mentioned

Ans-A

403)The clearance volumetric efficiency is equal to

  1. a) 1 + C + C(p2/p1)^(1/n)
  2. b) 1 – C – C(p2/p1)^(1/n)
  3. c) 1 – C + C(p2/p1)^(1/n)
  4. d) 1 + C – C(p2/p1)^(1/n

Ans-D

404)Plate evaporator is a common type of evaporator.

  1. a) true
  2. b) false

Ans-A

405)The intercooler pressure is given by

  1. a) p1*p2
  2. b) sqrt(p1*p2)
  3. c) (p1*p2)/(p1+p2)
  4. d) (p1+p2)/2

Ans-B

406)The most widely used refrigerants are

  1. a) freon
  2. b) genetron
  3. c) arcton
  4. d) all of the mentioned

Ans-D

407)Why is ammonia used in food refrigeration?

  1. a) high COP
  2. b) low cost
  3. c) lower energy cost
  4. d) all of the mentioned

Ans-D

408)In absorption refrigeration cycle, which of the following is used?

  1. a) refrigerant
  2. b) absorbent
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

409)Which of the following condenses first?

  1. a) ammonia vapour
  2. b) water vapour
  3. c) both condense at same temperature
  4. d) none of the mentioned

Ans-B

410)The vapour going to condenser is ____ in temperature and ____ in ammonia.

  1. a) higher, less
  2. b) higher, richer
  3. c) lower, less
  4. d) lower, richer

Ans-D

411)Lithium bromide-water vapour is another absorption refrigeration system.

  1. a) true
  2. b) false

Ans-A

412)Water is used as a ____ in air conditioning units.

  1. a) absorbent
  2. b) refrigerant
  3. c) absorbent and refrigerant
  4. d) none of the mentioned

Ans-B

413)The COP of absorption refrigeration system is

  1. a) low
  2. b) high
  3. c) equal to that of vapour compression refrigeration system
  4. d) none of the mentioned

Ans-A

414)A heat pump,

  1. a) extracts energy at low temperature heat source
  2. b) gives energy to high temperature heat source
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

415)A vapour compression heat pump has

  1. a) compressor
  2. b) evaporator
  3. c) condenser
  4. d) all of the mentioned

Ans-D

416)Which of the following can be used to transfer heat to the refrigerant passing through evaporator?

  1. a) outside air
  2. b) water from rivers
  3. c) the ground
  4. d) all of the mentioned

Ans-D

417)An air-air heat pump can be used for

  1. a) heating during winter
  2. b) cooling during summer
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

418)The ideal gas refrigeration cycle is same as

  1. a) the Brayton cycle
  2. b) reversed Brayton cycle
  3. c) the Rankine cycle
  4. d) reversed Rankine cycle

Ans-B

419)The COP of refrigeration cycle is given by

  1. a) 1 / {(p1/p2)^ɣ/(ɣ-1)]} – 1
  2. b) 1 / {(p1/p2)^(ɣ-1)/ɣ]} – 1
  3. c) 1 / {(p1/p2)^(ɣ-1)/ɣ]} + 1
  4. d) none of the mentioned

Ans-B

420)The COP of gas-cycle refrigeration cycle is very high.

  1. a) true
  2. b) false

Ans-B

421)A gas-cycle refrigeration system is used in

  1. a) aircrafts
  2. b) missiles
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

422)In a mixture of dry air and water vapour,

  1. a) mole fraction of dry air = pa/p
  2. b) mole fraction of water vapour = pw/p
  3. c) both of the mentioned
  4. d) none of the mentioned

Ans-C

423)The ____ section of a nozzle or diffuser is called throat.

  1. a) constant area
  2. b) maximum
  3. c) minimum
  4. d) all of the mentioned

Ans-C

424)In a carnot cycle, the working medium receives heat at a _____________ temperature.

  1. a) lower
  2. b) higher
  3. c) constant
  4. d) none of the mentioned

Ans-B

425)In a carnot cycle, the working medium rejects heat at a ____________ temperature.

  1. a) lower
  2. b) higher
  3. c) constant
  4. d) none of the mentioned

Ans-A

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