Heat Transfer Chemical Engineering Interview Questions - Set 12 - ObjectiveBooks

Heat Transfer Chemical Engineering Interview Questions - Set 12

Practice Test: Question Set - 12

1. jH factor for heat transfer depends upon the __________ number.
    (A) Biot
    (B) Nusselt
    (C) Reynolds
    (D) Prandtl

2. In pipe flow, heat is transferred from hot wall to the liquid by
    (A) Conduction only
    (B) Forced convection only
    (C) Forced convection and conduction
    (D) Free and forced convection

3. A perfect black body is a perfect __________ of radiation.
    (A) Absorber
    (B) Emitter
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

4. Heat transfer rate described by Fourier's law will decrease, if the __________ increases.
    (A) Thermal conductivity
    (B) Thickness
    (C) Temperature difference
    (D) Heat transfer area

5. The absorptivity of a body is equal to its emissivity
    (A) At a particular temperature
    (B) For circular bodies
    (C) Under thermal equilibrium
    (D) None of these

6. In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will
    (A) Increase
    (B) Decrease
    (C) Remain unchanged
    (D) Either increase or decrease; depends on the coolant flow rate

7. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1. °C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is
    (A) 165.4
    (B) 167.5
    (C) 172.5
    (D) 175

8. Which one gives the monochromatic emissive power for black body radiation?
    (A) Planck's law
    (B) Kirchhoff’s law
    (C) Wien's law
    (D) Stefan-Boltzmann law

9. If heat transfer rate varies with the time, it is termed as
    (A) Forced convection
    (B) Steady state conduction
    (C) Monochromatic radiation
    (D) None of these

10. Absorptivity and reflectivity of a perfect black body are respectively
    (A) 1 and 0
    (B) 0 and 1
    (C) 1 and ∞
    (D) 0 and 0.5

11. __________ heat exchanger is used for chilling oil to be dewaxed.
    (A) U-tube
    (B) Double pipe
    (C) Fixed tube
    (D) Floating head

12. Pick out the correct equation.
    (A) jH = (St)(Pr)2/3 = f/2
    (B) jH = (St)(Pr)1/3 = f/2
    (C) jH = (St)2/3(Pr) = f/2
    (D) jH = (St)1/3(Pr) = f/2

13. It is not preferable to use superheated steam in evaporators, because of its very
    (A) High temperature
    (B) High pressure
    (C) Low film co-efficient
    (D) None of these

14. Water is normally used as a coolant in the heat exchange equipments mainly because of its
    (A) Abundance & high heat capacity
    (B) Low density
    (C) Low viscosity
    (D) High fluidity

15. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of
    (A) 2
    (B) 20.8
    (C) 20.2
    (D) 20.5

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