Heat Transfer

391. The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the

  1. Heating volume
  2. Heat transfer area
  3. Nusselt number
  4. None of these
Correct answer: (B)
Heat transfer area

392. The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti - T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by

  1. q = [2π k (Ti + T0)/2]/ln (ri/r0)
  2. q = 2π ri k (Ti - T0)/(r0/ri)
  3. q = 2π k (Ti - T0)/(r0/ri)
  4. q = 2π k (Ti - T0)/[(r0 + ri)/2]
Correct answer: (D)
q = 2π k (Ti - T0)/[(r0 + ri)/2]

393. The ratio of kinematic viscosity to thermal diffusivity is called the _________ number.

  1. Peclet
  2. Prandtl
  3. Stanton
  4. Nusselt
Correct answer: (B)
Prandtl

394. The ratio of momentum diffusivity to thermal diffusivity is the _________ number.

  1. Prandtl
  2. Nusselt
  3. Stanton
  4. Grashoff
Correct answer: (A)
Prandtl

395. The ratio of total radiating power to the absorptivity of the body depends upon the _________ as per Kirchoff‟s law.

  1. Wavelength of radiation
  2. Nature of the body
  3. Temperature of the body
  4. None of these
Correct answer: (C)
Temperature of the body

396. The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is

  1. 2
  2. 43862
  3. 4
  4. 43922
Correct answer: (D)
43922

397. The separation of liquid droplets from the vapor is done by a/an _________, in the evaporators.

  1. Steam ejector
  2. Entrainment separator
  3. Compressor
  4. Vacuum pump
Correct answer: (B)
Entrainment separator

398. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

  1. D-1.8
  2. D-0.2
  3. D0.2
  4. D1.8
Correct answer: (B)
D-0.2

399. The statement that "maximum wavelength of radiation is inversely proportional to the temperature" is _________ law.

  1. Stefan-Boltzmann’s
  2. Planck's
  3. Wien's displacement
  4. None of these
Correct answer: (C)
Wien's displacement

400. The steam ejector is used to

  1. Remove condensate from the steam pipelines
  2. Create vacuum
  3. Superheat the steam
  4. None of these
Correct answer: (B)
Create vacuum
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