Home / Chemical Engineering / Heat Transfer :: Section 2

Chemical Engineering :: Heat Transfer

  1. What is the unit of thermal conductivity ?

  2. A.
    Kcal/hr. m2 °C
    B.
    Kcal/hr.m.°C
    C.
    Kcal/hr.m
    D.
    Kcal/hr. °C

  3. The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for

  4. A.
    black painted bodies only
    B.
    all bodies
    C.
    polished bodies only
    D.
    a black body

  5. It is not preferable to use superheated steam in evaporators, because of its very

  6. A.
    high temperature
    B.
    high pressure
    C.
    low film co-efficient
    D.
    none of these

  7. It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is

  8. A.
    3.06 x l05
    B.
    6.12 x 105
    C.
    7.24 x 105
    D.
    9.08 x 105

  9. LMTD for counterflow and prallel flow heat exchanger will be the same, when the

  10. A.
    cold fluid is heated to a certain temperature by condensing steam (isothermal fluid).
    B.
    outlent temperature of both the hot and cold fluid are same.
    C.
    outlet temperature of hot fluid is less than the outlet temperature of the cold fluid.
    D.
    none of these.

  11. For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

  12. A.
    NPr
    B.
    NPr1/3
    C.
    NPr-1
    D.
    NPr-1/3

  13. The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns.

  14. A.
    0.38-0.78
    B.
    0.5-50
    C.
    100-1000
    D.
    5-50

  15. Use of transverse baffles in a shell and tube heat exchanger is done to increase the

  16. A.
    rate of heat transfer.
    B.
    flow velocity.
    C.
    turbulence of shell side fluid.
    D.
    all (a), (b) and (c).

  17. The actual temperature drop across the heating surface of an evaporator depends on the

  18. A.
    liquid depth over the heating surface.
    B.
    solution being evaporated.
    C.
    pressure difference between the steam chest and the vapor space above the boiling liquid.
    D.
    all (a), (b) and (c)

  19. Economy of a multiple effect evaporator depends upon the

  20. A.
    heat balance consideration
    B.
    rate of heat transfer
    C.
    both (a) and (b)
    D.
    neither (a) nor (b)