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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

  1. The emissive power of a body depends upon its

  2. A.
    temperature
    B.
    physical nature
    C.
    wave length
    D.
    all of these

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  3. An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be

  4. A.
    25 mm
    B.
    40 mm
    C.
    160 mm
    D.
    800 mm

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  5. A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h1, h2 and h3 respectively. The average heat transfer coefficient for the cube is

  6. A.
    h1 + h2 + h3
    B.
    (h1h2h3)1/3
    C.
    D.
    none of these

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  7. The dehumidification process, on the psychrometric chart, is shown by

  8. A.
    horizontal Sine
    B.
    vertical line
    C.
    inclined line
    D.
    curved line

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  9. The vertical and uniformly spaced lines on a psychrometric chart indicates

  10. A.
    dry bulb temperature
    B.
    wet bulb temperature
    C.
    dew point temperature
    D.
    specific humidity

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  11. In case of sensible heating of air, the coil efficiency is given by (where B.P.F. = By-pass factor)

  12. A.
    B.P.F. - 1
    B.
    1 - B.P.F.
    C.
    D.
    1 + B.RF.

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  13. The coefficient of performance (C.O.P.) is the reciprocal of the efficiency of a heat engine.

  14. A.
    True
    B.
    False

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  15. The wet bulb temperature at 100% relative humidity is __________ dry bulb temperature.

  16. A.
    same as
    B.
    lower than
    C.
    higher than

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  17. The freezing point of sulphur dioxide is

  18. A.
    -56.6°C
    B.
    -75.2°C
    C.
    -77.7°C
    D.
    -135.8°C

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  19. The ratio of the energy absorbed by the body to the total energy falling on it, is called

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

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