Heat Transfer Lab Manual Chemical Engineering Questions - Set 10 - ObjectiveBooks

# Practice Test: Question Set - 10

1. Finned tube heat exchangers
(A) Give larger area per tube
(B) Use metal fins of low thermal conductivity
(C) Facilitate very large temperature drop through tube wall
(D) Are used for smaller heat load

2. Tube expansion allowances exist in __________ heat exchanger.
(A) Multipass fixed tube sheet
(B) U-tube
(C) Single pass fixed tube sheet
(D) None of these

3. Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.
(A) Long tube
(B) Falling film
(C) High pressure
(D) None of these

4. Pick out the wrong statement.
(A) In process heat exchangers, saturated steam is preferred over the superheated steam
(B) The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of Î»1. If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 Î»1
(C) When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, exhibits a maximum
(D) A body at 925 K emits an energy of 1.42 x 1011ÏƒW/m2 (Ïƒ is the Stefan-Boltzmann constant) in the wavelength band between 3 Î¼m to 4 Î¼m. The fraction of this energy in the total energy emitted over the entire wavelength range is equal to emissivity

5. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu Î± 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
(A) D-1.8
(B) D-0.2
(C) D0.2
(D) D1.8

6. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter).
(A) 0.2 D
(B) 0.5 D
(C) 0.66 D
(D) 0.80 D

7. For heat flow through very thick walled cylinder, use _________mean radius.
(A) Arithmetic
(B) Logarithmic
(C) Geometric
(D) Either (a) or (c)

8. Corrosiveness of steam condensate is due to the presence of
(A) CO2
(B) Dissolved O2
(C) Both (a) & (b)
(D) Neither (a) nor (b)

9. In a shell and tube heat exchanger, the shell side fluid velocity can’t be changed by changing the
(A) Tube layout
(B) Tube diameter
(C) Tube pitch
(D) Number of baffles

10. Solid angle subtended by the finite surface at the radiating element is
(A) Called the view factor
(B) Called the angle of vision
(C) Proportional to the square of the distance between surfaces
(D) Expressed in terms of radians

11. LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the __________ flow.
(A) Parallel
(B) Mixed
(C) Counter flow
(D) Same in either 'a', b' or 'c'

12. A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is
(A) 0
(B) R2/(R1+R2)
(C) 1
(D) (R1/R2)2

13. The maximum heat transfer co-efficient from steam heating will be attained when the steam is:
(A) Supersaturated
(B) Saturated
(C) Wet
(D) None of these

14. One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to
(A) Heat the water from 0°C to 100°C
(B) Evaporate the water
(C) To superheat the steam
(D) Data insufficient, can't be predicted

15. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is
(A) More
(B) Less
(C) Some
(D) Either more or less; depends on the nature of vapor

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