Refrigeration and Air-conditioning Miscellaneous
- If a mass of moist air contained in a closed metallic vessel is heated, then its
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Correct Option: A
- 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
- 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,
ṁw = ṁa (w1 - w2) 3 × (.019 - .008) = .033kg/s
By applying energy balance equation we get
ṁa h1 = ṁa h2 + ṁa hfg + Q
3 × 85 = 3 × 43 + 0.033 × 67 + Q
Q = 123.8 kWCorrect Option: B
Mass flow rate of condensate,
ṁw = ṁa (w1 - w2) 3 × (.019 - .008) = .033kg/s
By applying energy balance equation we get
ṁa h1 = ṁa h2 + ṁa hfg + Q
3 × 85 = 3 × 43 + 0.033 × 67 + Q
Q = 123.8 kW
- 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.
- Various psychrometric processes are shown in the figure below.
process in Figure Name 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.