The course of Refrigeration and Air Conditioning is of 2 years and where there is a semester system, its complete study is done in 4 semesters or it can be said that it is divided into 4 semesters, so below you have been given the question paper of its 4th semester.Which has already been asked in its exam, so solve it carefully and many more question papers related to this trade are given on our website, by solving which you can prepare yourself.
1. In a direct expansion system the product to be cooled:
• comes in direct contact with and mixes with the refrigerant flowing through the evaporator
• is outside the evaporator surface and is cooled by heat transfer from the refrigerant flowing through the evaporator
• is cooled by an intermediate coolant which is cooled by the refrigerant flowing through the evaporator
• None of the above
Ans. is outside the evaporator surface and is cooled by heat transfer from the refrigerant flowing through the evaporator
2. The variable portion of moist air is:
• Dry air
• Water vapour
• Both (a) and (b)
• None of the above
Ans. Water Vapor
3. Air in an air washer:
• Gets heated
• Gets cooled
• Gets heated
• Any of the above processes can occur depending on the temperature of the air
Ans. Any of the above processes can occur depending on the temperature of the air
4. HEPA is used for which of the following?
• High Energy Particulate Air
• High Efficiency Particulate Air
• High Entry Particulate Air
• Highly Effective Pressurized Air
Ans. High Efficiency Particulate Air
5. The decrease in pressure in ducts is caused due to………?
• Duct friction
• Change of direction
• Change of velocity
• All of the above
Ans. All of the above
6. Relative humidity may be defined as:
• The ratio of the mass of water vapour in a given volume of air coming at a given temperature to the mass of water vapour in the same volume of saturated air at
the same temperature • The ratio of the mass of water vapour in a given volume of dry air at a given temperature to the mass of water vapour in the same volume of saturated air at the same temperature
• The ratio of the mass of water vapour in a given volume of air coming at a given temperature to the mass of water vapour in the same volume of saturated air at the same temperature
• None of the above
Ans. The ratio of the mass of water vapour in a given volume of air coming at a given temperature to the mass of water vapour in the same volume of saturated air at the same temperature
7. In air conditioning systems, fans with ……… type of blades are preferred.
• Forward curled
• Radial
• Backward curled
• Both forward and backward curves
Ans. Backward curled
8. Various methods of duct design are :
• Equal friction method
• Velocity reduction method
• Static regain method
• All of the above
Ans. All of the above
9. The bypass factor of cooling and dehumidification coil is?
• Between 0.2 to 0.3
• Between 0.3 to 0.4
• Between 0.4 to 0.5
• Less than 0.2
Answer. Less than 0.2
10. Psychrometric chart is valid for:
• Water vapour pressure
• Standard atmospheric pressure
• Dry air pressure
• I air pressure
Answer. Standard atmospheric pressure
11. Vertical lines in psychrometic chart represent ………
• Dry bulb temperature
• Wet bulb temperature
• Dew point temperature
• Specific humidity
Answer. Dry bulb temperature
12. In sensible heating process:
• Relative humidity increases
• Specific humidity remains constant
• Wet bulb temperature increases
• Wet bulb temperature decreases
Answer. Wet bulb temperature increases
13. Hot water adds …..
• Latent heat in the air
• Sensible heat in the air
• Both sensible and latent heat
• First sensible and then latent heat
Ans. Both sensible and latent heat
14. The optimum indoor design conditions in comfortable air conditioning in summer are:
• DBT = 24 ± 1°C and RH 45 ± 5%
• DBT = 25 ± 1°C and RH 50 ± 5%
• DBT = 3D 25 ± 1°C and RH 45 ± 45%
• None of these
Ans. DBT = 25 ± 1°C and RH 50 ± 5%
15. Wet bulb depression (WBD) is the difference between …….
• Dry bulb and dew point temperatures
• Dry bulb and wet bulb temperatures
• Wet bulb and dew point temperatures
• None of these
Ans. Dry bulb and wet bulb temperature
16. Which of the following types of duct requires minimum material for transporting air?
• Rectangular
• Square
• Circular
• Trapezoid
Ans. Circular
17. In low pressure duct system –
• Velocity < 600 mpm and static pressure ≤ 5 cm H2O gauge
• Velocity < 500 mpm and static pressure ≤ 5 cm H2O gauge
• Velocity < 400 mpm and static pressure ≤ 5 cm H2O gauge
• Velocity < 350 mpm and static pressure ≤ 5 cm H2O gauge
Ans. Velocity < 600 mpm and static pressure ≤ 5 cm H2O gauge
18. In summer air conditioning, A.C. equipment uses:
• Cooling and humidification
• Sensible cooling
• Cooling and dehumidification
• Adiabatic humidification
Ans. Cooling and dehumidification
19. For sensible cooling of air, the temperature of the coil
should be • lower than the dew point temperature of the incoming air
• higher than the dew point temperature of the incoming air but lower than its dry bulb temperature
• lower than the dry bulb temperature of the incoming air
• None of these
Answer. It should be higher than the dew point temperature of the incoming air but lower than its dry bulb temperature.
20. Package AC comes in ……. capacities.
• Less than 2 TR
• Between 2 to 4 TR
• Between 5 to 15 TR
• More than 25 TR
Answer. Between 5 to 15 TR
21. Specific humidity may be defined as the ratio of:
• Mass of water vapour in a given quantity of mixture to the mass of moist air
• Mass of water vapour in a given quantity of mixture to the mass of dry air
• Mass of air coming in a given quantity of mixture to the mass of water vapour
• None of these
Answer. Mass of water vapour in a given quantity of mixture to the mass of dry air
22. ADP is used for which of the following?
• Apparatus dew point
• Apparatus desired pressure
• Apparatus defining point
• None of these
Ans. Apparatus dew point
23. Dry bulb temperature (DBT) is actually the temperature of …….
• Dry air
• Dry air
• Dry ice
• None of these
Ans. Dry air
24. In adiabatic humidification process :
• WBT increases
• WBT decreases
• WBT remains constant.
• Dry bulb temperature decreases
Ans. WBT remains constant.
25. For saturated air :
• DBT = WBT
• DPT > WBT
• WBT > DPT
• DBT > DPT
Ans. DBT = WBT
26. Fresh air or ventilation air is a must in any comfort air conditioning system. Their purpose is?
• Providing oxygen
• Removing carbon dioxide
• Removing odors
• All of the above
Ans. All of the above
27. The advantages of constant-pressure expansion valve are:
• Under low load conditions the constant-pressure valve maintains high suction pressure, thus preventing coil freeze-up
• Under high load conditions the constant-pressure expansion valve maintains low suction pressure, thus reducing power consumption and protecting the compressor from damage due to overload
• Both (a) and (b)
• None of the above
Ans. Both (a) and (b)
28. FCU is used for which of the following?
• Flow control unit
• Fan coil unit
• Fan control unit
• None of the above
Ans. Fan coil unit
29. Central A.C. The expansion devices used in the plant are:
• Thermostatic expansion valve
• Constant pressure valve
• Capillary tube
• Bottom float valve
Ans. Thermostatic expansion valve
30. In chemical dehumidification process:
• WBT increases
• WBT decreases
• WBT remains constant
• Dry bulb temperature decreases
Ans. WBT remains constant
31. AC air conditioning system of a car can be defined as which of the following?
• Dx system
• Indirect expansion system
• Both direct and indirect expansion
• Neither direct expansion nor indirect expansion
Ans. Dx system
32. For unsaturated air :
• DBT = WBT
• DPT – WBT
• DBT > WBT
• None of these
Ans. None of these
33. VRV is used for which of the following?
• Varying recirculated volume
• Variable refrigerant volume
• Varying refrigerant volume
• None of these
Ans. Variable refrigerant volume
34. Sensible heat factor can be expressed as:
• Latent heat
•Sensible heat
• Sensible heat
• Sum of sensible and latent heat
• Sum of sensible and latent heat
Ans. Sensible heat
35. Sensible heat during winter:
• Obtained from space
• Released into space
• Obtained from space or released into space depending upon room temperature
• None of these
Ans. Released into space
36. Dalton’s law mentions ……..
• Sum of partial volumes of gases
• Sum of partial pressures of gases
• Sum of partial temperatures of gases
• None of these
Ans. Sum of partial pressures of gases
37. Damper in AC system is used for……….
• Reducing pressure
• Varying flow rate
• Both (a) and (b)
• None of these
Ans. Both (a) and (b)
38. AHU is used for which of the following?
• Air handling unit
• Air heating unit
• Air humidifying unit
• None of these
Ans. Air handling unit
39. Bypass factor of cooling and coil can be defined as:
• Air coming in contact with the coil / Total air
• Air not coming in contact with the coil / Cool air minus the sum of the air not coming in contact with the coil
• Air not coming in contact with the coil / Total air
• None of these
Answer. Air not coming in contact with the coil / Total air
40. The main working element in air conditioning is:
• Dry air
• Dry ice
• Humid air
• Water vapour
Answer. Humid air
41. Air conditioning means ………
• Maintaining DBT
• Maintaining WBT
• Maintaining dewpoint temperature
• None of these
Ans. Maintaining DBT
42. With the help of psychrometer, we can measure ………
• Wet bulb and dew point temperature
• Dry bulb and dew point temperature
• Wet bulb and dry bulb temperature
• None of these
Ans. Wet bulb and dry bulb temperature
43. Air lock is:
• Simple interlocking spaces between conditioned and unconditioned/outside spaces
• Blockage of air due to temperature
• Inert air at some places
• None of these
Ans. Simple interlocking spaces between conditioned and unconditioned/outside spaces
44. Ducts are mostly made of …….
• Wood
• Expanded polystyrene
• Fibre glass
• GI sheet
Ans. GI sheet
45. ADP represents which of the following?
• Coil pressure
• Coil temperature
• Coil point
• None of these
Ans. Coil temperature
46. When the engine speed is reduced, the cooling capacity of the AC system of a car:
• Increases
• Remains unchanged
• Decreases
• May increase or decrease depending upon the number of people travelling in the car
Ans. Remains unchanged
47. The total pressure in the duct is equal to the sum of ……….
• Partial pressure of water vapour + velocity pressure
• Velocity pressure + static pressure + datum pressure head
• Static pressure + Datum pressure pressure
• Velocity pressure + Datum pressure head
Ans. Velocity pressure + Static pressure + Datum pressure head
48. The psychrometric conditioning process required during winter air conditioning is?
• Heating and humidification
• Heating and dehumidification
• Sensible heating
• Humidification
Answer. Heating and humidification
49. VRF is used for which of the following?
• Varying recalculated flow
• Variable refrigerant functions
• Variable refrigerant flow
• None of these
Answer. Variable refrigerant flow
50. The temperature to which humid air must be cooled at constant pressure before condensation of moisture can take place is called:
• Wet bulb temperature
• Dew point temperature
• Wet bulb depression
• Dry bulb temperature
Answer. dew point temperature
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