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Mechanical Engineering :: Heat Transfer,Refrigeration and Air Conditioning

Heat Transfer,Refrigeration and Air Conditioning - Section 1
Heat Transfer,Refrigeration and Air Conditioning - Section 2
Heat Transfer,Refrigeration and Air Conditioning - Section 3
Heat Transfer,Refrigeration and Air Conditioning - Section 4
Heat Transfer,Refrigeration and Air Conditioning - Section 5
Heat Transfer,Refrigeration and Air Conditioning - Section 6
Heat Transfer,Refrigeration and Air Conditioning - Section 7
Heat Transfer,Refrigeration and Air Conditioning - Section 8

  1. A composite slab has two layers of different materials with thermal conductivities k1 and k2. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be

    2. A.
    k1 k2
    B.
    k1 + k2
    C.
    D.

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  2. The critical temperature is the temperature

    3. A.
    below which a gas does not obey gas laws
    B.
    above which a gas may explode
    C.
    below which a gas is always liquified
    D.
    above which a gas will never liquified

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  3. The evaporator changes the low pressure liquid refrigerant from the expansion valve into

    4. A.
    high pressure liquid refrigerant
    B.
    low pressure liquid and vapour refrigerant
    C.
    low pressure vapour refrigerant
    D.
    none of these

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  4. For air conditioning the operation theatre in a hospital, the percentage of outside air in the air supplied is

    5. A.
    zero
    B.
    20
    C.
    50
    D.
    100

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  5. In case ofsensible cooling of air, the coil efficiency is given by

    6. A.
    B.P.F. - 1
    B.
    1 - B.P.F.
    C.
    D.
    1 + B.P.F.

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  6. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.

    7. A.
    True
    B.
    False

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  7. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because

    8. A.
    it considerably reduces mass of the system
    B.
    it improves the C.O.P., as the condenser is small
    C.
    the positive work in isentropic expansion of liquid is very small
    D.
    it leads to significant cost reduction

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  8. The unit of overall coefficient of heat transfer is

    9. A.
    W/m2K
    B.
    W/m2
    C.
    W/mK
    D.
    W/m

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  9. Most thermostatic expansion valves are set for a superheat of

    10. A.
    5°C
    B.
    10°C
    C.
    15°C
    D.
    20°C

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  10. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is

    11. A.
    reciprocating
    B.
    rotating
    C.
    centrifugal
    D.
    screw

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