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Chemical Engineering :: Heat Transfer

  1. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is

  2. A.
    1.66
    B.
    88.66
    C.
    3.66
    D.
    dependent on NRe only

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  3. Sensible heat of hot industrial flue gases can not be recovered by a/an

  4. A.
    economiser
    B.
    regenerator
    C.
    ceramic recuperator
    D.
    none of these

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  5. The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface)

  6. A.
    K/h0
    B.
    2K/h0
    C.
    h0/K
    D.
    h0/2K

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  7. Radiator of an automobile engine is a __________ type of heat exchanger.

  8. A.
    co-current
    B.
    cross-current
    C.
    counter-current
    D.
    direct contact

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  9. In pipe flow, heat is transferred from hot wall to the liquid by

  10. A.
    conduction only.
    B.
    forced convection only.
    C.
    forced convection and conduction.
    D.
    free and forced convection.

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  11. The value of Stefan-Boltazman constant in SI unit is

  12. A.
    5.6697 x 10-8W/m2.°K4
    B.
    0.1714 x 10-8W/m2.°K4
    C.
    5.6697 x 10-8kcal/m2 . °K4
    D.
    0.1714 x 10-8kcal/m2. °K4

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  13. The unit of heat transfer co-efficient is

  14. A.
    BTU/hr. ft2°F
    B.
    BTU/hr. °F. ft.
    C.
    BTU/hr. °F
    D.
    BTU/hr. ft

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  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

  16. A.
    1
    B.
    1.74
    C.
    6.1
    D.
    37

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  17. 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

  18. A.
    165.4
    B.
    167.5
    C.
    172.5
    D.
    175

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  19. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is

  20. A.
    0.5
    B.
    2
    C.
    10
    D.
    100

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