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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. In counter-current flow heat exchanger, the logarithmic temperature difference between the fluids is __________ as compared to parallel flow heat exchanger.

  2. A.
    same
    B.
    less
    C.
    greater

  3. Environmental protection agencies advice against the use of chloro-fluoro-carbon refrigerants since

  4. A.
    these react with water vapour and cause acid rain
    B.
    these react with plants and cause green-house effect
    C.
    these react with oxygen and cause its depletion
    D.
    these react with ozone layer

  5. When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

  6. A.
    operating the machine at higher speeds
    B.
    operating the machine at lower speeds
    C.
    raising the higher temperature
    D.
    lowering the higher temperature

  7. The refrigerant carbon dioxide is not widely used because of its __________ power require ments per tonne of refrigeration and high operating pressures.

  8. A.
    low
    B.
    high

  9. The by-pass factor of a cooling coil decreases with

  10. A.
    decrease in fin spacing and increase in number of rows
    B.
    increase in fin spacing and increase in number of rows
    C.
    increase in fin spacing and decrease in number of rows
    D.
    decrease in fin spacing and decrease in number of rows

  11. Dehydration is the process of removing water vapour from the surrounding air.

  12. A.
    True
    B.
    False

  13. The cooling of air, without any change in its specific humidity, is known as sensible cooling.

  14. A.
    Correct
    B.
    Incorrect

  15. The capacity of the cooling tower and spray ponds __________ as the wet bulb temperature of air decreases.

  16. A.
    increases
    B.
    decreases

  17. A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called

  18. A.
    dry air
    B.
    moist air
    C.
    saturated air
    D.
    specific humidity

  19. The total pressure exerted by the mixture of air and water vapour is equal to the sum of pressures which each constituent would exert, if it occupied the same space by itself. This statement is called

  20. A.
    Kinetic theory of gases
    B.
    Newton's law of gases
    C.
    Dalton's law of partial pressures
    D.
    Avogadro's hypothesis