Heat Transfer

331. Stefan's block body radiation law can also be derived from _________ law.

  1. Kirchoff’s
  2. Planck's
  3. Fourier's
  4. None of these
Correct answer: (B)
Planck's

332. Stefan-Boltzmann law applies to _________ body.

  1. Black
  2. White
  3. Grey
  4. Any colour
Correct answer: (A)
Black

333. Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K)

  1. t4
  2. T4
  3. 1/t4
  4. 1/T4
Correct answer: (B)

T4

334. Temperature profile in steady state heat transfer is

  1. Asymptotic
  2. Hyperbolic
  3. Parabolic
  4. Linear
Correct answer: (D)
Linear

335. Terminal point temperature differences between fluids in case of a heat exchanger is termed as

  1. Approach
  2. Log mean temperature difference
  3. Arithmetic mean temperature difference
  4. Geometric mean temperature difference
Correct answer: (A)
Approach

336. The absorptivity of a body is equal to its emissivity

  1. At a particular temperature
  2. For circular bodies
  3. Under thermal equilibrium
  4. None of these
Correct answer: (C)
Under thermal equilibrium

337. The absorptivity of a grey body at a given temperature _________ with increasing wavelength of radiation.

  1. Increases
  2. Decreases
  3. Remain constant
  4. May increase or decrease; depends on the material
Correct answer: (D)
May increase or decrease; depends on the material

338. The actual temperature drop across the heating surface in an evaporator depends on the

  1. Feed
  2. Depth of liquid over heating surface
  3. Pressure difference between steam chest and vapour space
  4. All (A), (B) and (C)
Correct answer: (D)
All (A), (B) and (C)

339. The actual temperature drop across the heating surface of an evaporator depends on the

  1. Liquid depth over the heating surface
  2. Solution being evaporated
  3. Pressure difference between the steam chest and the vapor space above the boiling liquid
  4. All (A), (B) and (C)
Correct answer: (D)
All (A), (B) and (C)

340. The advantage of backward feed multiple effect evaporators over forward feed units is that

  1. Heat sensitive material can be handled
  2. There is no additional cost of pumping
  3. Most concentrated liquid is at highest temperature
  4. Equal heat transfer co-efficients exist in various effects
Correct answer: (C)
Most concentrated liquid is at highest temperature
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