Refrigeration & Air-Conditioning Practice Set-4

June 7, 2021

Show paginator

Hide paginator

20%

Page 1 of 5

1. 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

Of adiabatic saturation of incoming stream

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

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

2. The specific humidity during dehumidification process

Remains constant

None of these

Decreases

Increases

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

CO2

Freon-22

Freon-12

NH3

4. 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

4 kW

2 kW

3 kW

1 kW

5. 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)/(td₃ - td₂)

(td₃ - td₂)/(td₃ - td₁)

(td₃ - td₁)/(td₂ - td₃)

(td₂ - td₃)/(td₃ - td₁)

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

20°C DBT and 50% RH

20°C DBT and 60% RH

26°C DBT and 50% RH

26°C DBT and 60% RH

7. The Freon group of refrigerants are

Hydrocarbon refrigerants

Halocarbon refrigerants

Inorganic refrigerants

Zoetrope refrigerants

8. During sensible cooling,

Relative humidity remains constant

Partial pressure of vapour remains constant

Wet bulb temperature increases

Specific humidity increases

9. The advantage of dry compression is that

It permits complete evaporation in the evaporator

It results in high volumetric and mechanical efficiency

It permits higher speeds to be used

All of the above

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

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

Page 2 of 5

11. The superheating in a refrigeration cycle

None of these

Increases C.O.P.

Does not alter C.O.P.

Decreases C.O.P.

12. Which of the following statement is correct?

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

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

The constant enthalpy lines are also constant wet bulb temperature lines

All of these

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

Compression of the refrigerant vapour

Condensation of the refrigerant vapour

Metering of the refrigerant liquid

Evaporation of the refrigerant liquid

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

Enthalpy increase in compressor

Heat of compression

Work done by compressor

All of the above

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

Dry

None of these

Flooded

DX coil

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

Dew point temperature

Effective temperature

None of these

Mean radiant temperature

17. Superheating in a refrigeration cycle

Other factors decide C.O.P

Increases C.O.P

Decreases C.O.P

C.O.P remains unaltered

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

Absorption

Compression

Direct

Indirect

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

Small

High

Anything

Equal

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

Dry saturated vapour

Saturated liquid

Superheated vapour

Wet vapour

Page 3 of 5

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

Solid and dry ice

Ice at 4°C

Mixture of ice and water under equilibrium conditions

Water at 0°C

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

Lower than

None of these

Same as

Higher than

23. The specific humidity during heating and humidification process.

Increases

Remains constant

None of these

Decreases

24. Moisture in Freon refrigeration system causes

Corrosion of whole system

High power consumption

Ineffective refrigeration

Freezing automatic regulating valve

25. Ammonia absorption refrigeration cycle requires

Very little work input

Nearly same work input as for vapour compression cycle

Zero work input

Maximum work input

26. 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

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

Condenser and expansion valve

Compressor and evaporator

Expansion valve and evaporator

Compressor and condenser

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

More than 10 kg

More than or equal to 3.65 kg

Less than 2 kg

There is no such consideration

29. 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)

μ/[1 - (1 - μ) (Ps/Pb)]

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

0.622 Pv / (Pb - Pv)

None of these

30. The relative coefficient of performance is

Actual COP × theoretical COP

Theoretical COP/actual COP

Actual COP/theoretical COP

None of these

Page 4 of 5

31. Refrigeration in aeroplanes usually employs the following refrigerant

Freon-11

Freon-22

Air

CO2

32. The sub-cooling in a refrigeration cycle

Does not alter C.O.P.

Increases C.O.P.

Decreases C.O.P.

None of these

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

Remain unaffected

Increase

May increase or decrease depending on the type of refrigerant used

Decrease

34. Air conditioning means

Dehumidifying

All of these

Heating

Cooling

35. Vapour compression refrigeration is somewhat like

Reversed Carnot cycle

Carnot cycle

None of the above

Rankine’s cycle

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

Specific

None of these

Absolute

Relative

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

Sulphur sticks

All of these

Halide torch

Soap and water

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

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

Will remain unaffected

Will be lower

Will be higher

39. 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

1.2

0.2

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

Sulphur dioxide

Ammonia

R-12

Carbon dioxide

Page 5 of 5

41. During cooling and dehumidification, dry bulb temperature

Increases

Remains constant

None of these

Decreases

42. Air refrigeration operates on

Reversed Carnot cycle

Brayton cycle

Rankine’s cycle

Carnot cycle

43. 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)

(h1 - h2)/ (hA - h2)

(h2 - hA)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

(hA - h2)/ (h1 - h2)

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

After passing through the expansion or throttle valve

Before entering the compressor

Before passing through the condenser

After passing through the condenser

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

Both room sensible heat and latent heat loads

None of the above

Room latent heat load only

Room sensible heat load only

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