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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be

  2. A.
    dehumidification
    B.
    cooling and humidification
    C.
    cooling and dehumidification
    D.
    dehumidification and pure sensible cooling

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  3. During heating and dehumidification process, dry bulb temperature

  4. A.
    remains constant
    B.
    increases
    C.
    decreases

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  5. The C.O.P. of a refrigerator working on a reversed Carnot cycle is (where T1 = Lowest absolute temperature, and T2 = Highest absolute temperature)

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  7. A refrigerant compressor is used to

  8. A.
    raise the pressure of the refrigerant
    B.
    raise the temperature of the refrigerant
    C.
    circulate the refrigerant through the refrigerating system
    D.
    all of the above

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  9. In which of the following refrigeration system, waste heat can be effectively used?

  10. A.
    Vapour compression cycle
    B.
    Vapour absorption cycle
    C.
    Air refrigeration cycle
    D.
    none of these

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  11. During heating and humidification, the final relative humidity of air

  12. A.
    is higher than that of the entering air
    B.
    is lower than that of the entering air
    C.
    can be lower or higher than that of the entering air
    D.
    none of the above

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  13. The fluids used in electrolux refrigerator are

  14. A.
    water and hydrogen
    B.
    ammonia and hydrogen
    C.
    ammonia, water and hydrogen
    D.
    none of these

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  15. The process of undercooling is generally brought about by

  16. A.
    circulating more quantity of cooling water through the condenser
    B.
    using water colder than the main circulating water
    C.
    employing a heat exchanger
    D.
    any one of the above

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  17. The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called

  18. A.
    sub-cooling or under-cooling
    B.
    super-cooling
    C.
    normal cooling
    D.
    none of these

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  19. R-12 has the __________ freezing point.

  20. A.
    lowest
    B.
    highest

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