Refrigeration & Air-Conditioning Practice Set-4

June 7, 2021

Show paginator

Hide paginator

20%

Page 1 of 5

1. Air conditioning means

Heating

Dehumidifying

All of these

Cooling

2. The wet bulb depression indicates _________ humidity of the air.

Relative

Specific

None of these

Absolute

3. The sub-cooling in a refrigeration cycle

None of these

Does not alter C.O.P.

Decreases C.O.P.

Increases C.O.P.

4. During sensible cooling,

Partial pressure of vapour remains constant

Specific humidity increases

Relative humidity remains constant

Wet bulb temperature increases

5. Which of the following statement is correct?

The constant enthalpy lines are also constant wet bulb temperature lines

The wet bulb and dry bulb temperature are equal at saturation condition

The wet bulb temperature is a measure of enthalpy of moist air

All of these

6. For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be

Anything

Small

High

Equal

7. The Freon group of refrigerants are

Halocarbon refrigerants

Hydrocarbon refrigerants

Inorganic refrigerants

Zoetrope refrigerants

8. The thermostatic expansion valve is used in ________ type of evaporators.

Flooded

DX coil

Dry

None of these

9. The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil, and h_A = Enthalpy of air at the end of humidification process)

(hA - h2)/ (h1 - h2)

(h2 - hA)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

(h1 - h2)/ (hA - h2)

10. Relative humidity is given by (where p_v = Partial pressure of water vapour, p_b = Barometric pressure, p_s = Pressure of saturated air, p_d = Pressure at dry bulb temperature, p_w = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)

[Pv (Pb - Pd)]/ [Pd (Pb - Pv)]

None of these

μ/[1 - (1 - μ) (Ps/Pb)]

0.622 Pv / (Pb - Pv)

Page 2 of 5

11. The boiling point of ________ is 10.5°C.

Sulphur dioxide

R-12

Carbon dioxide

Ammonia

12. The advantage of dry compression is that

It permits complete evaporation in the evaporator

It permits higher speeds to be used

It results in high volumetric and mechanical efficiency

All of the above

13. The wet bulb temperature at 100% relative humidity is ________ dew point temperature.

Same as

Lower than

Higher than

None of these

14. The leakage in a refrigeration system using Freon is detected by

Soap and water

Halide torch

All of these

Sulphur sticks

15. The bypass factor (B. P. F.) in case of sensible heating of air is (Where t_d₁ = Dry bulb temperature of air entering the heating coil, t_d₂ = Dry bulb temperature of air leaving the heating coil, and t_d₃ = Dry bulb temperature of heating coil)

(td₃ - td₁)/(td₂ - td₃)

(td₂ - td₃)/(td₃ - td₁)

(td₃ - td₂)/(td₃ - td₁)

(td₃ - td₁)/(td₃ - td₂)

16. In vapour compression refrigeration system, refrigerant occurs as liquid between

Compressor and condenser

Expansion valve and evaporator

Condenser and expansion valve

Compressor and evaporator

17. The index which correlates the combined effects of air temperature, relative humidity and air velocity on the human body, is known as

None of these

Mean radiant temperature

Dew point temperature

Effective temperature

18. The specific humidity during dehumidification process

Increases

Decreases

None of these

Remains constant

19. In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature

Which lies between the wet bulb and dew point temperatures of the incoming stream

Which is lower than the dew point temperature of the incoming stream

Of adiabatic saturation of incoming stream

Which lies between the dry bulb and wet bulb temperatures of the incoming stream

20. The specific humidity during heating and humidification process.

Remains constant

Increases

None of these

Decreases

Page 3 of 5

21. The alignment circle is marked on the psychrometric chart at

20°C DBT and 60% RH

26°C DBT and 60% RH

20°C DBT and 50% RH

26°C DBT and 50% RH

22. The conditioned air supplied to the room must have the capacity to take up

Room sensible heat load only

None of the above

Both room sensible heat and latent heat loads

Room latent heat load only

23. The relative coefficient of performance is

Actual COP/theoretical COP

Theoretical COP/actual COP

Actual COP × theoretical COP

None of these

24. A refrigeration cycle operates between condenser temperature of + 27°C and evaporator temperature of -23°C. The Carnot coefficient of performance of cycle will be

0.2

1.2

25. Moisture in Freon refrigeration system causes

Corrosion of whole system

Ineffective refrigeration

Freezing automatic regulating valve

High power consumption

26. In refrigerator, liquid receiver is required between condenser and flow controlling device, if quantity of refrigerant for system is

Less than 2 kg

There is no such consideration

More than or equal to 3.65 kg

More than 10 kg

27. Ammonia absorption refrigeration cycle requires

Nearly same work input as for vapour compression cycle

Maximum work input

Very little work input

Zero work input

28. Aqua ammonia is used as refrigerant in the following type of refrigeration system

Absorption

Direct

Compression

Indirect

29. The coefficient of performance is the ratio of the refrigerant effect to the

Work done by compressor

Heat of compression

All of the above

Enthalpy increase in compressor

30. The refrigeration effect in a dry evaporator compared to flooded evaporator in a similar plant is

Same

Less

More or less depending on ambient conditions

Page 4 of 5

31. Refrigeration in aeroplanes usually employs the following refrigerant

Freon-22

Air

Freon-11

CO2

32. Air refrigeration operates on

Carnot cycle

Brayton cycle

Rankine’s cycle

Reversed Carnot cycle

33. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be

1 kW

3 kW

4 kW

2 kW

34. Which of the following refrigerant has the highest freezing point.

Carbon dioxide

R-12

Ammonia

Sulphur dioxide

35. During cooling and dehumidification, dry bulb temperature

Decreases

Remains constant

None of these

Increases

36. The superheating in a refrigeration cycle

None of these

Does not alter C.O.P.

Increases C.O.P.

Decreases C.O.P.

37. Which of the following refrigerants has lowest freezing point?

Freon-12

NH3

Freon-22

CO2

38. A standard ice point temperature corresponds to the temperature of

Water at 0°C

Ice at 4°C

Mixture of ice and water under equilibrium conditions

Solid and dry ice

39. The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases,

Will be higher

Will remain unaffected

Will be lower

May be higher or lower depending upon the nature of non-condensable gases

40. The C.O.P. of a refrigeration cycle with lowering of condenser temperature, keeping the evaporator temperature constant, will

Decrease

Increase

Remain unaffected

May increase or decrease depending on the type of refrigerant used

Page 5 of 5

41. Vapour compression refrigeration is somewhat like

Carnot cycle

Rankine’s cycle

Reversed Carnot cycle

None of the above

42. The condition of refrigerant as it leaves the compressor in a vapour compression system is

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

43. Superheating in a refrigeration cycle

Decreases C.O.P

Other factors decide C.O.P

C.O.P remains unaltered

Increases C.O.P

44. The lower horizontal line of the refrigeration cycle plotted on pressure-enthalpy diagram represents

Evaporation of the refrigerant liquid

Condensation of the refrigerant vapour

Compression of the refrigerant vapour

Metering of the refrigerant liquid

45. In vapour compression cycle, the condition of refrigerant is very wet vapour

Before entering the compressor

After passing through the expansion or throttle valve

After passing through the condenser

Before passing through the condenser

Share this Now with Friends:

www.binance.info注册 says:
April 6, 2026 at 7:50 pm
Your point of view caught my eye and was very interesting. Thanks. I have a question for you. https://www.binance.info/register?ref=IXBIAFVY
注册 says:
April 11, 2026 at 6:27 am
Your point of view caught my eye and was very interesting. Thanks. I have a question for you.

Refrigeration & Air-Conditioning Practice Set-4

Related

2 Responses

Leave a ReplyCancel reply

Secured Payments

Protection