Chemical Engineering Questions and Answers - Heat Transfer - Set 15 - ObjectiveBooks

Chemical Engineering Questions and Answers - Heat Transfer - Set 15

Practice Test: Question Set - 15

1. Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger?
    (A) Tube side pressure drop and the heat transfer rate
    (B) Convective heat transfer co-efficient
    (C) Effective tube surface area for convective heat transfer
    (D) All (a) (b) and (c)

2. A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36°C. The temperature difference across the layer A is __________ °C.
    (A) 6
    (B) 12
    (C) 18
    (D) 24

3. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is
    (A) 0.5
    (B) 2
    (C) 10
    (D) 100

4. Economy of a multiple effect evaporator depends upon the
    (A) Heat balance consideration
    (B) Rate of heat transfer
    (C) Both (a) and (b)
    (D) Neither (a) nor (b)

5. The main purpose of providing fins on heat transfer surface is to increase the
    (A) Temperature gradient
    (B) Mechanical strength of the equipment
    (C) Heat transfer area
    (D) Heat transfer co-efficient

6. Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law.
    (A) Stefan's
    (B) Dalton's
    (C) Wien's
    (D) Kirchoff’s

7. Trap is used to remove __________ from steam pipe lines.
    (A) Steam
    (B) Condensate
    (C) Non-condensable
    (D) None of these

8. Prandtl number is given by
    (A) CP µ/a
    (B) hD/k
    (C) CP µ/k
    (D) µ/h CP

9. Pick out the wrong statement:
    (A) With change in temperature, the radiant energy emitted by a black body remains unchanged
    (B) Absorptivity of a body approaches unity in case of diffuse reflection
    (C) Absorptivity of a perfectly black body is unity
    (D) Value of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/°K4

10. Prandtl number is the ratio of
    (A) Momentum diffusivity to mass diffusivity
    (B) Momentum diffusivity to thermal diffusivity
    (C) Thermal diffusivity to mass diffusivity
    (D) Thermal diffusivity to momentum diffusivity

11. In the free convection regime of pool boiling, the heat flux is proportional to
    (A) Δt1/2
    (B) Δt2
    (C) Δt5/4
    (D) Δt

12. Radiation heat losses from satisfactorily insulated high pressure boiler may be about __________ percent.
    (A) 1
    (B) 7
    (C) 18
    (D) 26

13. When vaporization takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling.
    (A) Pool
    (B) Nucleate
    (C) Transition
    (D) Film

14. In SI units, fouling factor is expressed in
    (A) m2°K/W
    (B) W/m2°K
    (C) m2°K
    (D) m°K/W

15. Kg of liquid evaporated per hour in an evaporator is defined as its
    (A) Capacity
    (B) Economy
    (C) Steam load
    (D) None of these

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