Heat and Mass Transfer MCQ pdf Online Practice Test - Set 20 - ObjectiveBooks
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Heat and Mass Transfer MCQ pdf Online Practice Test - Set 20

Practice Test: Question Set - 20


1. For concentrating an aqueous solution of a material like anhydrous Na2SO4, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
    (A) High pressure
    (B) Vacuum
    (C) Backward feed
    (D) None of these

2. Small scale evaporation is done in a
    (A) Heat exchanger
    (B) Condenser
    (C) Multiple effect evaporator
    (D) Steam jacketed kettle

3. Leidenfrost point is a term concerned with the
    (A) Condensation of the saturated vapor on a cold surface
    (B) Concentration of a corrosive solution by evaporation
    (C) Heat transfer between two highly viscous liquids
    (D) Boiling of a liquid on a hot surface

4. In a single effect evaporator, the economy is
    (A) 1
    (B) < 1
    (C) > 1
    (D) None of these

5. At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below: The thermal conductivity of material ‘I’
    (A) Is smaller than that of II
    (B) Is greater than that of II
    (C) Is equal to that of II
    (D) Can be greater than or smaller than that of II

6. Mode of heat transfer involved in the cooling of air cooled internal combustion engine is
    (A) Conduction
    (B) Natural convection
    (C) Forced convection
    (D) None of these

7. Which of the following is not used as a medium for high temperature heating?
    (A) Dowtherm
    (B) Mercury
    (C) Liquid metal (e.g. molten sodium)
    (D) Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

8. In counter flow compared to parallel flow,
    (A) LMTD is greater
    (B) Less surface area is required for a given heat transfer rate
    (C) Both (a) and (b)
    (D) More surface area is required for a given heat transfer rate

9. The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8.
    (A) 20.8
    (B) 40.8
    (C) 40.4
    (D) 20.4

10. Heat exchangers operating, when the asymptotic range is reached,
    (A) Provide very large heat transfer co-efficient
    (B) Results in making part of the heating surface inactive
    (C) Results in abruptly increased velocity
    (D) None of these

11. In regenerative air preheater (as practiced in heating of coke ovens), the heat is transferred
    (A) Through a metallic wall
    (B) By direct contact of hot flue gas with air
    (C) By heating an intermediate material (like chequer bricks) and then heating the air from this hot material
    (D) None of these

12. In case of evaporators, liquid entrainment results primarily due to
    (A) High vacuum in the evaporator
    (B) High evaporation rate
    (C) Foaming of the solution
    (D) High heat transfer rate

13. A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is
    (A) 6000
    (B) 24000
    (C) 60000
    (D) 48000

14. Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube
    (A) Exit-fluid temperature > wall temperature
    (B) Exit fluid temperature < wall temperature
    (C) Exit fluid temperature = wall temperature
    (D) Graetz number > 100

15. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is
    (A) 1.66
    (B) 88.66
    (C) 3.66
    (D) Dependent on NRe only

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