Objective type questions and answers in refrigeration and air conditioning - Set 15

Practice Test: Question Set - 15


1. The formation of frost on cooling coils in a refrigerator
    (A) Increases heat transfer
    (B) Improves C.O.P. of the system
    (C) Increases power consumption
    (D) Reduces power consumption

2. The power per tonne of refrigeration is
    (A) 3.5/C.O.P.
    (B) C.O.P/3.5
    (C) 3.5 × C.O.P.
    (D) None of these

3. The wet bulb temperature during sensible heating of air
    (A) Remains constant
    (B) Increases
    (C) Decreases
    (D) None of these

4. The relative humidity is defined as
    (A) The mass of water vapour present in 1 m3 of dry air
    (B) The mass of water vapour present in 1 kg of dry air
    (C) The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure
    (D) The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure

5. As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.
    (A) Same as
    (B) Lower than
    (C) Higher than
    (D) None of these

6. In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
    (A) 0.3
    (B) 0.6
    (C) 0.67
    (D) 1.5

7. An Electrolux refrigerator is called a _________ absorption system.
    (A) Single fluid
    (B) Two fluids
    (C) Three fluids
    (D) None of these

8. It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be
    (A) Dehumidification
    (B) Cooling and humidification
    (C) Cooling and dehumidification
    (D) Dehumidification and pure sensible cooling

9. The difference between dry bulb temperature and wet bulb temperature, is called
    (A) Dry bulb depression
    (B) Wet bulb depression
    (C) Dew point depression
    (D) Degree of saturation

10. The coefficient of performance of Heat Pump is always _________ one.
    (A) Equal to
    (B) Less than
    (C) Greater than
    (D) None of these

11. An evaporator is also known as
    (A) Freezing coil
    (B) Cooling coil
    (C) Chilling coil
    (D) All of these

12. A refrigeration system
    (A) Removes heat from a low temperature body and delivers it to a high temperature body
    (B) Removes heat from a high temperature body and delivers it to a low temperature body
    (C) Rejects energy to a low temperature body
    (D) None of the above

13. Nusselt number (NN) is given by
    (A) NN = hl/k
    (B) NN = μ cp/k
    (C) NN = ρ V l /μ
    (D) NN = V²/t.c

14. The temperature of ammonia after compression in a vapour compression system is
    (A) 20 to 50°C
    (B) 50 to 70°C
    (C) 70 to 110°C
    (D) None of these

15. A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
    (A) Lack of cooling water
    (B) Water temperature being high
    (C) Dirty condenser surface
    (D) All of these

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