Refrigeration and Air-conditioning Miscellaneous


Refrigeration and Air-conditioning Miscellaneous

Refrigeration and Air-conditioning

  1. If a mass of moist air contained in a closed metallic vessel is heated, then its









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    Correct Option: A


  1. Air (at atmospheric pressure) at a dry bulb temperature of 40°C and wet bulb temperature of 20°C is humidified in an air washer operating with continuous water recirculation. The wet bulb depression, the difference between the dry and wet bulb temperatures) at the exit is 25% of that at the inlet. The dry bulb temperature at the exit of the air washer is closest to









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    NA

    Correct Option: C

    NA



  1. Atmospheric air at a flow rate of 3 kg/s (on dry basis) enters a cooling and dehumidifying coil with an enthalpy of 85 kJ/kg of dry air and a humidity ratio of 19 grams/kg of dry air. The air leaves the coil with an enthalpy of 43 kJ/kg of dry air and a humidity ratio of 8 grams/kg of dry air. If the condensate water leaves the coil with an enthalpy of 67 kJ/kg, the required cooling capacity of the coil in kW is









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    Mass flow rate of condensate,
    w = ṁa (w1 - w2) 3 × (.019 - .008) = .033kg/s
    By applying energy balance equation we get
    a h1 = ṁa h2 + ṁa hfg + Q
    3 × 85 = 3 × 43 + 0.033 × 67 + Q
    Q = 123.8 kW

    Correct Option: B

    Mass flow rate of condensate,
    w = ṁa (w1 - w2) 3 × (.019 - .008) = .033kg/s
    By applying energy balance equation we get
    a h1 = ṁa h2 + ṁa hfg + Q
    3 × 85 = 3 × 43 + 0.033 × 67 + Q
    Q = 123.8 kW


  1. Dew point temperature is the temperature at which condensation begins when the air is cooled at constant









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    Air is cooled at constant pressure to make unsaturated air to saturated one.

    Correct Option: C


    Air is cooled at constant pressure to make unsaturated air to saturated one.



  1. Various psychrometric processes are shown in the figure below.
    process in FigureName of the Process
    P. 0-1(i) Chemical dehumidification
    Q. 0-2(ii) Sensible heating
    R. 0-3(iii) Cooling and dehumidification
    S. 0-4 (iv) Humidification with steam injection
    T. 0-5(v) Humidification with water injection


    The matching pair are









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    Process 0 - 1 : DBT ↑ ,w C; sensibleheating
    Process 0 - 2 : DBT ↑ ,w ↓ ;heating & dehumidification
    Process 0 – 3; Cooling and dehumidification
    Process 0 – 4 ; Humidification with water injection (DBT↓, w ↑)
    Process 0 – 5; DBT ↑, w ↑ : Humidification with steam injection.

    Correct Option: B


    Process 0 - 1 : DBT ↑ ,w C; sensibleheating
    Process 0 - 2 : DBT ↑ ,w ↓ ;heating & dehumidification
    Process 0 – 3; Cooling and dehumidification
    Process 0 – 4 ; Humidification with water injection (DBT↓, w ↑)
    Process 0 – 5; DBT ↑, w ↑ : Humidification with steam injection.