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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. Which of the following refrigerant has the maximum ozone depletion potential in the stratophere?

  2. A.
    Ammonia
    B.
    Carbon dioxide
    C.
    Sulphur dioxide
    D.
    Flourine

  3. Which of the following statement is correct?

  4. A.
    The constant enthalpy lines are also constant wet bulb temperature lines.
    B.
    The wet bulb and dry bulb temperature are equal at saturation condition.
    C.
    The wet bulb temperature is a measure of enthalpy of moist air.
    D.
    all of the above

  5. According to Stefan's law, the total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature.

  6. A.
    Correct
    B.
    Incorrect

  7. In electrolux refrigerator

  8. A.
    ammonia is absorbed in hydrogen
    B.
    ammonia is absorbed in water
    C.
    ammonia evaporates in hydrogen
    D.
    hydrogen evaporates in ammonia

  9. Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be

  10. A.
    one
    B.
    two
    C.
    three
    D.
    four

  11. A boot-strap air cooling system has

  12. A.
    one heat exchanger
    B.
    two heat exchangers
    C.
    three heat exchangers
    D.
    four heat exchangers

  13. The boiling point of __________ is -10.5°C.

  14. A.
    ammonia
    B.
    R-12
    C.
    sulphur dioxide
    D.
    carbon dioxide

  15. One tonne of refrigeration (1TR) means that the heat removing capacity is

  16. A.
    21 kJ/min
    B.
    210 kJ/min
    C.
    420 kJ/min
    D.
    620 kJ/min

  17. The operating pressure for refrigerating units using R-12 as a refrigerant is

  18. A.
    2 bar
    B.
    8 bar
    C.
    15 bar
    D.
    30 bar

  19. The specific humidity during heating and humidification process.

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