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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. A condenser of refrigeration system rejects heat at the rate of 120 kW, while its compressor consumes a power of 30 kW. The coefficient of performance of the system will be

  2. A.
    1/4
    B.
    1/3
    C.
    3
    D.
    4

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  3. A refrigerant with the highest critical pressure is

  4. A.
    R-11
    B.
    R-12
    C.
    R-22
    D.
    Ammonia

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  5. In a shell and tube heat exchanger, baffles are provided on the shell side to

  6. A.
    improve heat transfer
    B.
    provide support for tubes
    C.
    prevent stagnation of shell side fluid
    D.
    all of these

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  7. The average value of thermal conductivity for water at 20° C saturate is about 0.51.

  8. A.
    True
    B.
    False

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  9. In aqua-ammonia absorption refrigeration system, incomplete rectification leads to accumulation of water in

  10. A.
    condenser
    B.
    evaporator
    C.
    absorber
    D.
    none of these

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  11. The boiling point of ammonia is

  12. A.
    -10.5°C
    B.
    -30°C
    C.
    -33.3°C
    D.
    -77.7°C

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  13. The by-pass factor (B. P. F.) in case of sensible heating of air is (Where td1 = Dry bulb temperature of air entering the heating coil, td2 = Dry bulb temperature of air leaving the heating coil, and td3 = Dry bulb temperature of heating coil)

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  15. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and

  16. A.
    carbon dioxide
    B.
    sulphur dioxide
    C.
    lithium bromide
    D.
    R-12

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  17. In a black body, all radiations are rejected.

  18. A.
    True
    B.
    False

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  19. Most air cooled condensers are designed to operate with a temperature difference of

  20. A.
    5°C
    B.
    8°C
    C.
    14°C
    D.
    22°C

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