Heat Transfer Unit Operations of Chemical Engineering MCQ - Set 05 - ObjectiveBooks

# Practice Test: Question Set - 05

1. The film co-efficient between condensing vapor and metal wall increases with
(A) Increasing temperature of the vapor
(B) Decreasing temperature of the vapor
(C) Increasing viscosity of the film of condensate
(D) Increasing temperature drop

2. In Fourier's law, the proportionality constant is called the
(A) Heat transfer co-efficient
(B) Thermal diffusivity
(C) Thermal conductivity
(D) Stefan-Boltzmann constant

3. The non-dimensional temperature gradient in a liquid at the wall of a pipe is the
(A) Heat flux
(B) Nusselt number
(C) Prandtl number
(D) Schmidt number

4. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is:
(A) Free convection
(B) Entry length problem in laminar forced conduction (developing thermal boundary layer)
(C) Mixed convection (both free and forced)
(D) Forced convection

5. "The ratio of the total emissive power to the absorptivity for all bodies is same at thermal equilibrium". This is __________ law.
(A) Kirchoff’s
(B) Planck's
(C) Wien's displacement
(D) Stefan-Boltzmann

6. The units of resistance to heat transfer is
(A) J.m-2.K-1
(B) J.m-1.K-1
(C) W.m-2.K-1
(D) W-1m2K

7. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is
(A) Nu = 0.023 Re0.8. Pr0.4
(B) Nu = (π/2) Gz
(C) Nu = (2/π) Gz
(D) Nu = 2Gz0.5

8. For hot feed, forward feeding as compared to backward feeding results in __________ economy.
(A) Increased
(B) Decreased
(C) No effect on
(D) None of these

9. Pick out the wrong statement.
(A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection
(B) The ratio NNu/NRe . Npr is called the Stanton number
(C) The Peclet number is a measure of the ratio of energy transport by convection to that by conduction
(D) The Colburn jH factor for heat transfer is given by Nst Npr

10. In sub-cooled boiling,
(A) Temperature of the heating surface is less than the boiling point of the liquid
(B) Temperature of the heating surface is more than the boiling point of the liquid
(C) Bubbles from heating surface are absorbed by the mass of the liquid
(D) Very large vapor space is necessary

11. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling?
(A) Square pitch
(B) Triangular pitch
(C) Diagonal square pitch
(D) None of these

12. Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place
(A) Between two bodies in physical contact with each other
(B) Between two bodies not in physical contact with each other
(C) From one part of a body to the another part of the same body
(D) Both 'b' & 'c'

13. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has
(A) Lower heat transfer area
(B) Lower steam economy
(C) Higher steam economy
(D) Higher solute concentration in the product

14. The thickness of condensate layer in filmwise condensation depends on the
(A) Condensation rate
(B) Surface configuration
(C) Liquid flow rate from the surface
(D) All (a), (b) and (c)

15. With increase in temperature, the total emissivity of conductors
(A) Increases
(B) Decreases
(C) Remain same
(D) Decreases linearly

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