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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. R-12 is generally preferred over R-22 in deep freezers since

  2. A.
    it has low operating pressures
    B.
    it gives higher coefficient of performance
    C.
    it is miscible with oil over large range of temperatures
    D.
    all of the above

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  3. The temperature of air recorded by a thermometer, when its bulb is surrounded by a wet cloth exposed to the air, is called

  4. A.
    wet bulb temperature
    B.
    dry bulb temperature
    C.
    dew point temperature
    D.
    none of these

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  5. During sub-cooling, sensible heat from a liquid refrigerant is removed.

  6. A.
    Yes
    B.
    No

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  7. The expression is used for calculating relative humidity.

  8. A.
    Yes
    B.
    No

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  9. If the energy radiated per second per sq. cm. of the surface for wave lengths lying between λ, and λ + dλ is represented by (eλ.dλ), then eλ is called

  10. A.
    absorptive power
    B.
    emissive power
    C.
    emissivity
    D.
    none of these

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  11. Dry bulb temperature is the temperature of air recorded by a thermometer, when

  12. A.
    it is not affected by the moisture present in the air
    B.
    its bulb is surrounded by a wet cloth exposed to the air
    C.
    the moisture present in it begins to condense
    D.
    none of the above

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  13. In a spray washing system, if the temperature of water is higher than the dry bulb temperature of entering air, then the air is

  14. A.
    heated and dehumidified
    B.
    heated and humidified
    C.
    cooled and humidified
    D.
    cooled and dehumidified

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  15. A valve which maintains a constant degree of superheat at the end of the evaporator coil, is called

  16. A.
    automatic expansion valve
    B.
    high side float valve
    C.
    thermostatic expansion valve
    D.
    low side float valve

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  17. The atmospheric air at dry bulb temperature of 15°C enters a heating coil maintained at 40°C. The air leaves the heating coil at 25°C. The by-pass factor of the heating coil is

  18. A.
    0.376
    B.
    0.4
    C.
    0.6
    D.
    0.67

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  19. An infinite parallel planes with emissivities e1 and e2, the interchange factor for radiation from surface 1 to surface 2 is given by

  20. A.
    B.
    C.
    e1 + e2
    D.
    e1e2

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