Refrigeration & Air-Conditioning Practice Set-4

Page 1 of 5

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

Relative

None of these

Absolute

Specific

2. 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

Effective temperature

Dew point temperature

None of these

3. The relative coefficient of performance is

Actual COP × theoretical COP

Actual COP/theoretical COP

None of these

Theoretical COP/actual COP

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

R-12

Carbon dioxide

Sulphur dioxide

Ammonia

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

Water at 0°C

Mixture of ice and water under equilibrium conditions

Ice at 4°C

Solid and dry ice

6. The specific humidity during heating and humidification process.

Remains constant

Decreases

Increases

None of these

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

May increase or decrease depending on the type of refrigerant used

Decrease

Increase

Remain unaffected

8. The specific humidity during dehumidification process

Remains constant

None of these

Decreases

Increases

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

Flooded

Dry

None of these

DX coil

10. During sensible cooling,

Partial pressure of vapour remains constant

Wet bulb temperature increases

Specific humidity increases

Relative humidity remains constant

Page 2 of 5

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

26°C DBT and 60% RH

20°C DBT and 60% RH

20°C DBT and 50% RH

26°C DBT and 50% RH

12. The superheating in a refrigeration cycle

Decreases C.O.P.

None of these

Increases C.O.P.

Does not alter C.O.P.

13. 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 10 kg

More than or equal to 3.65 kg

Less than 2 kg

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

Carbon dioxide

R-12

Sulphur dioxide

Ammonia

15. During cooling and dehumidification, dry bulb temperature

Remains constant

None of these

Increases

Decreases

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

Indirect

Absorption

Compression

Direct

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

Work done by compressor

All of the above

Enthalpy increase in compressor

Heat of compression

18. Air conditioning means

Cooling

All of these

Dehumidifying

Heating

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

Room latent heat load only

None of the above

Both room sensible heat and latent heat loads

Room sensible heat load only

20. The Freon group of refrigerants are

Halocarbon refrigerants

Zoetrope refrigerants

Inorganic refrigerants

Hydrocarbon refrigerants

Page 3 of 5

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

Soap and water

Halide torch

Sulphur sticks

All of these

22. 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 - td₁)/(td₂ - td₃)

(td₃ - td₂)/(td₃ - td₁)

23. Ammonia absorption refrigeration cycle requires

Very little work input

Maximum work input

Zero work input

Nearly same work input as for vapour compression cycle

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

More

More or less depending on ambient conditions

Less

Same

25. Refrigeration in aeroplanes usually employs the following refrigerant

Freon-22

Air

CO2

Freon-11

26. 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

5

1.2

6

0.2

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

Compression of the refrigerant vapour

Evaporation of the refrigerant liquid

Metering of the refrigerant liquid

Condensation of the refrigerant vapour

28. The sub-cooling in a refrigeration cycle

Does not alter C.O.P.

Decreases C.O.P.

Increases C.O.P.

None of these

29. 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 remain unaffected

Will be higher

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

30. Moisture in Freon refrigeration system causes

High power consumption

Freezing automatic regulating valve

Corrosion of whole system

Ineffective refrigeration

Page 4 of 5

31. 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

1 kW

2 kW

3 kW

32. 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)

33. Vapour compression refrigeration is somewhat like

Reversed Carnot cycle

Rankine’s cycle

Carnot cycle

None of the above

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

Dry saturated vapour

Superheated vapour

Wet vapour

Saturated liquid

35. 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

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

Condenser and expansion valve

Compressor and condenser

Expansion valve and evaporator

Compressor and evaporator

37. The advantage of dry compression is that

It permits complete evaporation in the evaporator

It results in high volumetric and mechanical efficiency

All of the above

It permits higher speeds to be used

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

CO2

NH3

Freon-22

Freon-12

39. Which of the following statement is correct?

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

The constant enthalpy lines are also constant wet bulb temperature lines

All of these

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

40. 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

0.622 Pv / (Pb - Pv)

μ/[1 - (1 - μ) (Ps/Pb)]

Page 5 of 5

41. Superheating in a refrigeration cycle

C.O.P remains unaltered

Decreases C.O.P

Increases C.O.P

Other factors decide C.O.P

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

None of these

Higher than

Same as

Lower than

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

High

Small

Equal

Anything

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

After passing through the condenser

Before passing through the condenser

Before entering the compressor

After passing through the expansion or throttle valve

45. Air refrigeration operates on

Reversed Carnot cycle

Rankine’s cycle

Brayton cycle

Carnot cycle

Refrigeration & Air-Conditioning Practice Set-4

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection

Refrigeration & Air-Conditioning Practice Set-4

Share this Now with Friends:

Related

Leave a ReplyCancel reply

Ads by Google

Recent Posts

Membership Registration

Secured Payment

Protection