Heat Transfer - GATE Practice Papers - Chemical Engineering - Set 22 - ObjectiveBooks

Heat Transfer - GATE Practice Papers - Chemical Engineering - Set 22

Practice Test: Question Set - 22

1. If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor.
    (A) Increase
    (B) Decrease
    (C) Not affect
    (D) Increase the condensing film co-efficient as well as

2. The most conducive surface for dropwise condensation to occur is the __________ surface.
    (A) Coated
    (B) Oily
    (C) Glazed & polished
    (D) Smooth

3. For a perfectly transparent surface (like gases), the
    (A) Absorptivity = 0
    (B) Transmissivity = 1
    (C) Reflectivity = 0
    (D) All (a), (b) & (c)

4. Shell side pressure drop in a shell and tube heat exchanger does not depend upon the
    (A) Baffle spacing & shell diameter
    (B) Tube diameter & pitch
    (C) Viscosity, density & mass velocity of shell side fluid
    (D) None of these

5. A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to
    (A) d0.8
    (B) d-0.2
    (C) d-1
    (D) d-1.8

6. In evaporators, lowering the feed temperature
    (A) Increases the heating area required
    (B) Reduces the economy
    (C) Both (a) and (b)
    (D) Decreases the heating area required

7. Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by
h = 0.023 (K/D) (DVρ/µ)0.8 (CP.µ/k)0.4. This is valid for the value of NRe equal to
    (A) < 2100
    (B) 2100-4000
    (C) > 4000
    (D) > 10000

8. In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient
    (A) Increases
    (B) Decreases
    (C) Is not affected
    (D) May increase or decrease; depends on the feed

9. The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.
    (A) Peclet
    (B) Prandtl
    (C) Stanton
    (D) Nusselt

10. Intermittent tube cleaning is possible to be done in case of a __________ evaporator.
    (A) Basket type
    (B) Horizontal tube
    (C) Calandria
    (D) None of these

11. Vibrations in the tubes of a shell and tube heat exchanger is induced due to the
    (A) Flow of fluid on the tube and shell sides
    (B) Oscillations in the flow of shell/tube sides fluid
    (C) Vibrations transmitted through piping and/or supports due to external reasons
    (D) All (a), (b) and (c)

12. Pick out the wrong statement.
    (A) Orifice baffles are never used in a shell and tube heat exchanger
    (B) Pressure drop on the shell side of a heat exchanger depends upon tube pitch also
    (C) In a horizontal tube evaporator, surface blanketing by air is avoided
    (D) Split ring type and pull through type floating heads are two commonly used floating heads is heat exchangers

13. What is the steam economy in case of a single effect evaporator system?
    (A) 1
    (B) > 1
    (C) < 1
    (D) 0.1

14. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about
    (A) 50 -100 Kcal/hr.m2.°C
    (B) 50 -100 W/m2.°K
    (C) 50 -100 BTU/hr. ft.2°F
    (D) 1000 - 1500 BTU/hr. ft.2°F

15. For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of
    (A) 1
    (B) 1.74
    (C) 6.1
    (D) 37

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