# Practice Test: Question Set - 23

1. For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Î”t = excess temperature)
(A) Î”t
(B) Î”t2
(C) Î”t3
(D) √(Î”t)

2. Baffles in the shell side of a shell and tube heat exchanger
(A) Increase the cross-section of the shell side liquid
(B) Force the liquid to flow parallel to the bank
(C) Increase the shell side heat transfer co-efficient
(D) Decrease the shell side heat transfer co-efficient

3. The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoff’s law.
(B) Nature of the body
(C) Temperature of the body
(D) None of these

4. __________ chart is known as transient heat conduction chart.
(A) Dirhing's
(B) Heisler's
(C) Mollier's
(D) Cox

5. Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C.
(A) 10-50
(B) 100-500
(C) 1000-1500
(D) 5000-15000

6. Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.
(A) No
(B) The least
(C) The largest
(D) Lower

7. The main function of baffles provided in a shell and tube heat exchanger is to
(A) Facilitate the cleaning of outer tube surface
(B) Enhance turbulence
(C) Hold the tubes in position
(D) All 'a', 'b' & 'c'

8. Pick out the wrong statement:
(A) The capacity of an evaporator is reduced by the boiling point elevation
(B) Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger
(C) Steam jet ejector is used for vapor compression in a thermal recompression evaporator
(D) Heat sensitive materials should be concentrated in high pressure evaporators

9. Boiling point elevation of an ideal solution
(A) Increases rapidly with temperature rise
(B) Decreases rapidly with temperature rise
(C) In independent of pressure
(D) Both (b) and (c)

10. Which of the following is concerned with both heat and mass transfer?
(A) Lewis relationship
(B) Nusselt number
(D) Froude number

11. The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is
(Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4)
(A) 1000
(B) 727
(C) 800
(D) 1200

12. Duhring’s rule is important in solving problems on
(A) Distillation
(B) Crystallization
(C) Evaporation
(D) Humidification

13. Which is the most suitable for the concentration of foamy & frothy liquors?
(A) Agitated film evaporator
(B) Long tube vertical evaporator
(C) Open pan evaporator
(D) None of these

14. Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on
(A) T1 - T2
(B) T1 - Ta
(C) T2 - Ta
(D) None of these

15. Air is best heated with steam in a heat exchanger of
(A) Plate type
(B) Double pipe type with fin on steam side
(C) Double pipe type with fin on air side
(D) Shell and tube type

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