The vapour absorption refrigeration system using Ammonia water has cycle operating pressures

lower than that using Lithium Bromide water

higher than that using Lithium Bromide water

lower than that using Lithium Bromide water

may be higher or lower depending upon application

higher for sub-zero application and lower for above zero application

With reciprocating compressor in vapour compression refrigeration system, wetcompression is not desirable because

liquid trapped up in the head of cylinder may damage the compressor valves

volumetric efficiency of compressor decreases

mass flow rate per ton of refrigerant increases

Shaft work required for vapour absorption system to produce 1 ton refrigeration may be only

50 to 60% of that required for vapour compression system

20 to 30% of that required for vapour compression system

1 to 2% of that required for vapour compression system

During compression in a vapour compression cycle the refrigerant is super heated

Refrigerating effect is reduced

Wet compression vapour compression refrigeration cycle means

Vapour compression in dry region, but evaporation in wet region

Vapour compression takes place in wet region

Vapour compression in dry region, but evaporation in wet region

vapour compression in wet region, but leaves in superheated region

The oil separator is incorporated in vapour compression refrigeration system

between condenser and Throttle valve

between evaporator and compressor

between compressor and condenser

between condenser and Throttle valve

between throttle valve and evaporator

The optimum effective temperature for human comfort is%!

Higher in winter than in summer

The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)%!

(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√Ö -td‚Äö√á√â)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√á -td‚Äö√á√â)/( td‚Äö√á√Ö -td‚Äö√á√â)

(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√â -td‚Äö√á√á)/( td‚Äö√á√Ö -td‚Äö√á√â)

The reciprocating refrigerant compressors are very suitable for%!

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

The air cooling system mostly used in transport type aircrafts is%!

Simple evaporative air cooling system

The advantage of dry compression is that%!

It permits higher speeds to be used

It permits complete evaporation in the evaporator

It results in high volumetric and mechanical efficiency

The capillary tube is not used in large capacity refrigeration systems because%!

Capacity control is not possible

Required pressure drop cannot be achieved

A standard ice point temperature corresponds to the temperature of%!

Mixture of ice and water under equilibrium conditions

The vapour pressure of refrigerant should be%!

Lower than atmospheric pressure

Higher than atmospheric pressure

*$_The reciprocating refrigerant compressors are very suitable for?

Large displacements and low condensing pressures

Small displacements and low condensing pressures

Large displacements and high condensing pressures

Small displacements and high condensing pressures

Large displacements and low condensing pressures

*$_The air cooling system mostly used in transport type aircrafts is?

Simple evaporative air cooling system

*$_The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)?

(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√Ö -td‚Äö√á√â)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√á -td‚Äö√á√â)/( td‚Äö√á√Ö -td‚Äö√á√â)

(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

(td‚Äö√á√â -td‚Äö√á√á)/( td‚Äö√á√Ö -td‚Äö√á√â)

*$_A standard ice point temperature corresponds to the temperature of?

Mixture of ice and water under equilibrium conditions

*$_The vapour pressure of refrigerant should be?

Lower than atmospheric pressure

Higher than atmospheric pressure

*$_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

*$_The bypass factor for a cooling coil?

Decreases with increase in velocity of air passing through it

Increases with increase in velocity of air passing through it

Decreases with increase in velocity of air passing through it

Remains unchanged with increase in velocity of air passing through it

May increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering

*$_The refrigerant supplied to a compressor must be?

Dry saturated liquid refrigerant

A mixture of liquid and vapour refrigerant

*$_Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and ≈í¬∫ = Degree of saturation)?

≈í¬∫/[1 - (1 - ≈í¬∫) (Ps/Pb)]

*/*_The advantage of dry compression is that?

It permits higher speeds to be used

It permits complete evaporation in the evaporator

It results in high volumetric and mechanical efficiency

368 + Mcqs in Refrigeration And Air Conditioning in Mechanical Engineering Page 2 McqOptions

51.	The vapour absorption refrigeration system using Ammonia water has cycle operating pressures
A.	higher than that using Lithium Bromide water
B.	lower than that using Lithium Bromide water
C.	may be higher or lower depending upon application
D.	higher for sub-zero application and lower for above zero application
Answer» B. lower than that using Lithium Bromide water

Discussion

52.	With reciprocating compressor in vapour compression refrigeration system, wetcompression is not desirable because
A.	liquid trapped up in the head of cylinder may damage the compressor valves
B.	COP of the cycle decreases
C.	volumetric efficiency of compressor decreases
D.	mass flow rate per ton of refrigerant increases
Answer» B. COP of the cycle decreases

Discussion

53.	An air stream at a flow rate of 1 kg/s and a DBT of 30 C mixes adiabatically with another air stream flowing with a mass flow rate of 2 kg/s and at a DBT of 15 C. Assuming no condensation to take place, the temperature of the mixture is approximately equal to:
A.	20 C
B.	22.5 C
C.	25 C
D.	Cannot be found
Answer» B. 22.5 C

Discussion

54.	The Wet bulb depression is zero when Relative humidity equals
A.	0
B.	0.5
C.	0.75
D.	1
Answer» E.

Discussion

55.	Shaft work required for vapour absorption system to produce 1 ton refrigeration may be only
A.	50 to 60% of that required for vapour compression system
B.	20 to 30% of that required for vapour compression system
C.	1 to 2% of that required for vapour compression system
D.	none of the above
Answer» D. none of the above

Discussion

56.	The temperature at which the water vapour in the air starts. condensing is known as
A.	dew point
B.	dry bulb
C.	wet bulb
D.	saturation
Answer» B. dry bulb

Discussion

57.	During compression in a vapour compression cycle the refrigerant is super heated
A.	work done is increased
B.	C.O.P is increased
C.	Work done is reduced
D.	Refrigerating effect is reduced
Answer» B. C.O.P is increased

Discussion

58.	Wet compression vapour compression refrigeration cycle means
A.	Vapour compression takes place in wet region
B.	Vapour compression in dry region, but evaporation in wet region
C.	vapour compression in wet region, but leaves in superheated region
D.	None of the above
Answer» B. Vapour compression in dry region, but evaporation in wet region

Discussion

59.	The oil separator is incorporated in vapour compression refrigeration system
A.	between evaporator and compressor
B.	between compressor and condenser
C.	between condenser and Throttle valve
D.	between throttle valve and evaporator
Answer» C. between condenser and Throttle valve

Discussion

60.	A refrigeration cycle is usually a
A.	open cycle
B.	closed cycle
C.	mixed cycle
D.	Hybrid cycle
Answer» C. mixed cycle

Discussion

61.	At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant%!
A.	decreases
B.	increases
C.	remains same
D.	depends on other factors
Answer» C. remains same

Discussion

62.	In a refrigeration cycle, the flow of refrigerant is controlled by%!
A.	Compressor
B.	Condenser
C.	Evaporator
D.	Expansion valve
Answer» E.

Discussion

63.	An evaporator is also known as%!
A.	Freezing coil
B.	Cooling coil
C.	Chilling coil
D.	All of these
Answer» E.

Discussion

64.	The optimum effective temperature for human comfort is%!
A.	Higher in winter than in summer
B.	Lower in winter than in summer
C.	Same in winter and summer
D.	Not dependent on season
Answer» C. Same in winter and summer

Discussion

65.	Which of the following refrigerant has the highest freezing point.%!
A.	Ammonia
B.	Carbon dioxide
C.	Sulphur dioxide
D.	R-12
Answer» C. Sulphur dioxide

Discussion

66.	The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)%!
A.	(td‚Äö√á√Ö -td‚Äö√á√â)/( td‚Äö√á√á -td‚Äö√á√â)
B.	(td‚Äö√á√á -td‚Äö√á√â)/( td‚Äö√á√Ö -td‚Äö√á√â)
C.	(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)
D.	(td‚Äö√á√â -td‚Äö√á√á)/( td‚Äö√á√Ö -td‚Äö√á√â)
Answer» C. (td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

Discussion

67.	The reciprocating refrigerant compressors are very suitable for%!
A.	Small displacements and low condensing pressures
B.	Large displacements and high condensing pressures
C.	Small displacements and high condensing pressures
D.	Large displacements and low condensing pressures
Answer» D. Large displacements and low condensing pressures

Discussion

68.	In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is%!
A.	High pressure saturated liquid
B.	Wet vapour
C.	Very wet vapour
D.	Dry vapour
Answer» B. Wet vapour

Discussion

69.	The air cooling system mostly used in transport type aircrafts is%!
A.	Simple air cooling system
B.	Simple evaporative air cooling system
C.	Bootstrap air cooling system
D.	All of these
Answer» D. All of these

Discussion

70.	A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called%!
A.	Dry air
B.	Moist air
C.	Saturated air
D.	Specific humidity
Answer» D. Specific humidity

Discussion

71.	The boiling point of ammonia is%!
A.	-10.5¬¨‚àûC
B.	-30¬¨‚àûC
C.	-33.3¬¨‚àûC
D.	-77.7¬¨‚àûC
Answer» D. -77.7¬¨‚àûC

Discussion

72.	The dry bulb temperature during sensible heating of air%!
A.	Remains constant
B.	Increases
C.	Decreases
D.	None of these
Answer» C. Decreases

Discussion

73.	The advantage of dry compression is that%!
A.	It permits higher speeds to be used
B.	It permits complete evaporation in the evaporator
C.	It results in high volumetric and mechanical efficiency
D.	All of the above
Answer» E.

Discussion

74.	The capillary tube is not used in large capacity refrigeration systems because%!
A.	Cost is too high
B.	Capacity control is not possible
C.	It is made of copper
D.	Required pressure drop cannot be achieved
Answer» C. It is made of copper

Discussion

75.	A standard ice point temperature corresponds to the temperature of%!
A.	Water at 0¬¨‚àûC
B.	Ice at 4¬¨‚àûC
C.	Solid and dry ice
D.	Mixture of ice and water under equilibrium conditions
Answer» E.

Discussion

76.	In case of sensible cooling of air, the coil efficiency is given by%!
A.	B.P.F. - 1
B.	1 - B.P.F.
C.	1/ B.P.F.
D.	1 + B.P.F.
Answer» C. 1/ B.P.F.

Discussion

77.	The vapour pressure of refrigerant should be%!
A.	Lower than atmospheric pressure
B.	Higher than atmospheric pressure
C.	Equal to atmospheric pressure
D.	Could be anything
Answer» C. Equal to atmospheric pressure

Discussion

78.	*$_The reciprocating refrigerant compressors are very suitable for?
A.	Small displacements and low condensing pressures
B.	Large displacements and high condensing pressures
C.	Small displacements and high condensing pressures
D.	Large displacements and low condensing pressures
Answer» D. Large displacements and low condensing pressures

Discussion

79.	*$_The air cooling system mostly used in transport type aircrafts is?
A.	Simple air cooling system
B.	Simple evaporative air cooling system
C.	Bootstrap air cooling system
D.	All of these
Answer» D. All of these

Discussion

80.	*$_In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is?
A.	High pressure saturated liquid
B.	Wet vapour
C.	Very wet vapour
D.	Dry vapour
Answer» B. Wet vapour

Discussion

81.	*$_The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)?
A.	(td‚Äö√á√Ö -td‚Äö√á√â)/( td‚Äö√á√á -td‚Äö√á√â)
B.	(td‚Äö√á√á -td‚Äö√á√â)/( td‚Äö√á√Ö -td‚Äö√á√â)
C.	(td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)
D.	(td‚Äö√á√â -td‚Äö√á√á)/( td‚Äö√á√Ö -td‚Äö√á√â)
Answer» C. (td‚Äö√á√â -td‚Äö√á√Ö)/( td‚Äö√á√á -td‚Äö√á√â)

Discussion

82.	*$_In case of sensible cooling of air, the coil efficiency is given by?
A.	B.P.F. - 1
B.	1 - B.P.F.
C.	1/ B.P.F.
D.	1 + B.P.F.
Answer» C. 1/ B.P.F.

Discussion

83.	*$_A standard ice point temperature corresponds to the temperature of?
A.	Water at 0¬¨‚àûC
B.	Ice at 4¬¨‚àûC
C.	Solid and dry ice
D.	Mixture of ice and water under equilibrium conditions
Answer» E.

Discussion

84.	*$_The boiling point of ammonia is?
A.	-10.5¬¨‚àûC
B.	-30¬¨‚àûC
C.	-33.3¬¨‚àûC
D.	-77.7¬¨‚àûC
Answer» D. -77.7¬¨‚àûC

Discussion

85.	*$_The vapour pressure of refrigerant should be?
A.	Lower than atmospheric pressure
B.	Higher than atmospheric pressure
C.	Equal to atmospheric pressure
D.	Could be anything
Answer» C. Equal to atmospheric pressure

Discussion

86.	*$_The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases,?
A.	Will be higher
B.	Will be lower
C.	Will remain unaffected
D.	May be higher or lower depending upon the nature of non-condensable gases
Answer» B. Will be lower

Discussion

87.	*$_The bypass factor for a cooling coil?
A.	Increases with increase in velocity of air passing through it
B.	Decreases with increase in velocity of air passing through it
C.	Remains unchanged with increase in velocity of air passing through it
D.	May increase or decrease with increase in velocity of air passing through it depending upon the condition of air entering
Answer» B. Decreases with increase in velocity of air passing through it

Discussion

88.	*$_Bell Coleman cycle is a?
A.	Reversed Carnot cycle
B.	Reversed Otto cycle
C.	Reversed Joule cycle
D.	Reversed Rankine cycle
Answer» D. Reversed Rankine cycle

Discussion

89.	*$_The refrigerant supplied to a compressor must be?
A.	Superheated vapour refrigerant
B.	Dry saturated liquid refrigerant
C.	A mixture of liquid and vapour refrigerant
D.	None of these
Answer» B. Dry saturated liquid refrigerant

Discussion

90.	*$_Absorption system normally uses the following refrigerant?
A.	Freon-11
B.	Freon-22
C.	CO2
D.	Ammonia
Answer» E.

Discussion

91.	*$_The humidification process, on the psychrometric chart is shown by?
A.	Horizontal line
B.	Vertical line
C.	Inclined line
D.	Curved line
Answer» C. Inclined line

Discussion

92.	*$_The vertical and uniformly spaced lines on a psychrometric chart indicates?
A.	Dry bulb temperature
B.	Wet bulb temperature
C.	Dew point temperature
D.	Specific humidity
Answer» B. Wet bulb temperature

Discussion

93.	*$_As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.?
A.	Same as
B.	Lower than
C.	Higher than
D.	None of these
Answer» C. Higher than

Discussion

94.	*$_Critical temperature is the temperature above which?
A.	A gas will never liquefy
B.	A gas will immediately liquefy
C.	Water will evaporate
D.	Water will never evaporate
Answer» B. A gas will immediately liquefy

Discussion

95.	*$_Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and ≈í¬∫ = Degree of saturation)?
A.	0.622 Pv / (Pb - Pv)
B.	≈í¬∫/[1 - (1 - ≈í¬∫) (Ps/Pb)]
C.	[Pv (Pb - Pd)]/ [Pd (Pb - Pv)]
D.	None of these
Answer» C. [Pv (Pb - Pd)]/ [Pd (Pb - Pv)]

Discussion

96.	*$_The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.?
A.	More
B.	Less
C.	Equally
D.	Unpredictable
Answer» B. Less

Discussion

97.	*$_The atmospheric air at dry bulb temperature of 15¬¨‚àûC enters a heating coil maintained at 40¬¨‚àûC. The air leaves the heating coil at 25¬¨‚àûC. The bypass factor of the heating coil is?
A.	0.376
B.	0.4
C.	0.6
D.	0.67
Answer» D. 0.67

Discussion

98.	*$_In a pressure enthalpy chart, the space to the left of the saturated liquid line represents?
A.	Wet vapour region
B.	Superheated vapour region
C.	Sub-cooled liquid region
D.	None of these
Answer» D. None of these

Discussion

99.	/_The advantage of dry compression is that?
A.	It permits higher speeds to be used
B.	It permits complete evaporation in the evaporator
C.	It results in high volumetric and mechanical efficiency
D.	All of the above
Answer» E.

Discussion

100.	/_A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called?
A.	Dry air
B.	Moist air
C.	Saturated air
D.	Specific humidity
Answer» D. Specific humidity

Discussion

Explore topic-wise MCQs in Mechanical Engineering.

The vapour absorption refrigeration system using Ammonia water has cycle operating pressures

With reciprocating compressor in vapour compression refrigeration system, wetcompression is not desirable because

An air stream at a flow rate of 1 kg/s and a DBT of 30 C mixes adiabatically with another air stream flowing with a mass flow rate of 2 kg/s and at a DBT of 15 C. Assuming no condensation to take place, the temperature of the mixture is approximately equal to:

The Wet bulb depression is zero when Relative humidity equals

Shaft work required for vapour absorption system to produce 1 ton refrigeration may be only

The temperature at which the water vapour in the air starts. condensing is known as

During compression in a vapour compression cycle the refrigerant is super heated

Wet compression vapour compression refrigeration cycle means

The oil separator is incorporated in vapour compression refrigeration system

A refrigeration cycle is usually a

At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant%!

In a refrigeration cycle, the flow of refrigerant is controlled by%!

An evaporator is also known as%!

The optimum effective temperature for human comfort is%!

Which of the following refrigerant has the highest freezing point.%!

The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)%!

The reciprocating refrigerant compressors are very suitable for%!

In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is%!

The air cooling system mostly used in transport type aircrafts is%!

A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called%!

The boiling point of ammonia is%!

The dry bulb temperature during sensible heating of air%!

The advantage of dry compression is that%!

The capillary tube is not used in large capacity refrigeration systems because%!

A standard ice point temperature corresponds to the temperature of%!

In case of sensible cooling of air, the coil efficiency is given by%!

The vapour pressure of refrigerant should be%!

*$_The reciprocating refrigerant compressors are very suitable for?

*$_The air cooling system mostly used in transport type aircrafts is?

*$_In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is?

*$_The bypass factor, in case of sensible cooling of air, is given by (where td‚Äö√á√Ö = Dry bulb temperature of air entering the cooling coil, td‚Äö√á√á = Dry bulb temperature of air leaving the cooling coil, and td‚Äö√á√â = Dry bulb temperature of the cooling coil)?

*$_In case of sensible cooling of air, the coil efficiency is given by?

*$_A standard ice point temperature corresponds to the temperature of?

*$_The boiling point of ammonia is?

*$_The vapour pressure of refrigerant should be?

*$_The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for condensing temperatures without non-condensable gases,?

*$_The bypass factor for a cooling coil?

*$_Bell Coleman cycle is a?

*$_The refrigerant supplied to a compressor must be?

*$_Absorption system normally uses the following refrigerant?

*$_The humidification process, on the psychrometric chart is shown by?

*$_The vertical and uniformly spaced lines on a psychrometric chart indicates?

*$_As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.?

*$_Critical temperature is the temperature above which?

*$_Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and ≈í¬∫ = Degree of saturation)?

*$_The change in evaporator temperature in a refrigeration cycle, as compared to change in condenser temperature, influences the value of C.O.P.?

*$_The atmospheric air at dry bulb temperature of 15¬¨‚àûC enters a heating coil maintained at 40¬¨‚àûC. The air leaves the heating coil at 25¬¨‚àûC. The bypass factor of the heating coil is?

*$_In a pressure enthalpy chart, the space to the left of the saturated liquid line represents?

*/*_The advantage of dry compression is that?

*/*_A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called?

/_The advantage of dry compression is that?

/_A mixture of dry air and water vapour, when the air has diffused the maximum amount of water vapour into it, is called?