Refrigeration & Air-Conditioning Practice Set-4

June 7, 2021

Show paginator

Hide paginator

20%

Page 1 of 5

1. 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)]

None of these

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

0.622 Pv / (Pb - Pv)

2. 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)

(td₂ - td₃)/(td₃ - td₁)

(td₃ - td₁)/(td₃ - td₂)

(td₃ - td₂)/(td₃ - td₁)

(td₃ - td₁)/(td₂ - td₃)

3. 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)

(h2 - hA)/ (h1 - h2)

(h1 - h2)/ (hA - h2)

(hA - h2)/ (h1 - h2)

(hA - h1)/ (h2 - h1)

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

All of the above

Work done by compressor

Heat of compression

Enthalpy increase in compressor

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

Decrease

May increase or decrease depending on the type of refrigerant used

Increase

Remain unaffected

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

Water at 0°C

Solid and dry ice

Ice at 4°C

Mixture of ice and water under equilibrium conditions

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

Superheated vapour

Dry saturated vapour

Saturated liquid

Wet vapour

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

Compression of the refrigerant vapour

Metering of the refrigerant liquid

Evaporation of the refrigerant liquid

Condensation of the refrigerant vapour

9. 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

2 kW

3 kW

1 kW

4 kW

10. The Freon group of refrigerants are

Hydrocarbon refrigerants

Halocarbon refrigerants

Zoetrope refrigerants

Inorganic refrigerants

Page 2 of 5

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

Equal

Anything

Small

High

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

Sulphur dioxide

Carbon dioxide

Ammonia

R-12

13. 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 lower

Will be higher

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

Will remain unaffected

14. 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

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

Compression

Direct

Absorption

Indirect

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

Dry

Flooded

None of these

DX coil

17. 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

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

Before entering the compressor

After passing through the condenser

After passing through the expansion or throttle valve

Before passing through the condenser

19. Ammonia absorption refrigeration cycle requires

Very little work input

Zero work input

Maximum work input

Nearly same work input as for vapour compression cycle

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

Expansion valve and evaporator

Condenser and expansion valve

Compressor and condenser

Compressor and evaporator

Page 3 of 5

21. Moisture in Freon refrigeration system causes

Freezing automatic regulating valve

Ineffective refrigeration

High power consumption

Corrosion of whole system

22. The specific humidity during heating and humidification process.

Increases

None of these

Remains constant

Decreases

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

Mean radiant temperature

None of these

Dew point temperature

Effective temperature

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

CO2

Freon-22

NH3

Freon-12

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

Sulphur sticks

All of these

Halide torch

Soap and water

26. Which of the following statement is correct?

All of these

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

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

Absolute

Specific

None of these

Relative

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

Lower than

None of these

Higher than

Same as

29. The sub-cooling in a refrigeration cycle

Increases C.O.P.

Does not alter C.O.P.

None of these

Decreases C.O.P.

30. The advantage of dry compression is that

It results in high volumetric and mechanical efficiency

It permits complete evaporation in the evaporator

All of the above

It permits higher speeds to be used

Page 4 of 5

31. The superheating in a refrigeration cycle

None of these

Increases C.O.P.

Does not alter C.O.P.

Decreases C.O.P.

32. Superheating in a refrigeration cycle

Other factors decide C.O.P

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

33. Vapour compression refrigeration is somewhat like

Reversed Carnot cycle

Rankine’s cycle

None of the above

Carnot cycle

34. The specific humidity during dehumidification process

Increases

Decreases

Remains constant

None of these

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

More or less depending on ambient conditions

Less

Same

36. The relative coefficient of performance is

Actual COP/theoretical COP

Theoretical COP/actual COP

None of these

Actual COP × theoretical COP

37. Air refrigeration operates on

Carnot cycle

Rankine’s cycle

Brayton cycle

Reversed Carnot cycle

38. Refrigeration in aeroplanes usually employs the following refrigerant

Freon-11

Freon-22

Air

CO2

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

R-12

Ammonia

Sulphur dioxide

Carbon dioxide

40. Air conditioning means

Heating

Cooling

All of these

Dehumidifying

Page 5 of 5

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

Room sensible heat load only

Both room sensible heat and latent heat loads

None of the above

Room latent heat load only

42. During cooling and dehumidification, dry bulb temperature

Increases

Decreases

None of these

Remains constant

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

26°C DBT and 50% RH

20°C DBT and 60% RH

20°C DBT and 50% RH

26°C DBT and 60% RH

44. During sensible cooling,

Wet bulb temperature increases

Relative humidity remains constant

Partial pressure of vapour remains constant

Specific humidity increases

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

There is no such consideration

More than or equal to 3.65 kg

Less than 2 kg

More than 10 kg

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