# 280+ Refrigeration and Air conditioning Solved MCQs

Chapters

48
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Chapter: Introduction to Refrigeration
1.

## Reversed carnot cycle comprises

A. two isentropic processes and two adiabatic processes
B. two isentropic processes and two isothermal processes
C. two isentropic processes and two isobaric processes
D. two isentropic processes and two isochoric processes
Answer» B. two isentropic processes and two isothermal processes
2.

## Two Carnot Refrigerators are employed, one for ice making and other for comfort cooling

A. The COP of the refrigerator for ice making is higher than that for other
B. The COP of the refrigerator for ice making is same as that for the other
C. The COP of the refrigerator for ice making is lower than that for other
D. The COP of Carnot refrigerator will depend on refrigerant used
Answer» C. The COP of the refrigerator for ice making is lower than that for other
3.

A. 1.25
B. 1.5
C. 2
D. 2.5
Answer» A. 1.25
4.

## Carnot refrigerator absorbs heat at -13° C and requires 1 kW for each 6.5 kW of heat absorbed, the COP and temperature of heat rejections respectively

A. COP = 6.5, t = 27° C
B. COP = 7.5, t = 27° C
C. COP = 6.5, t = 30° C
D. COP = 7.5, t = 37° C
Answer» A. COP = 6.5, t = 27° C
5.

## The dense air refrigeration system as compared to open air refrigeration system for same range of temperatures using Bell- Colemann cycle requires.

A. Same power/Ton of Refrigeration
B. Lower power/Ton of Refrigeration
C. Higher power/Ton of Refrigeration
D. Unpredictable Results.
Answer» B. Lower power/Ton of Refrigeration
6.

## For very high speed planes cruising at Mach number 2.5 and above, the air craft refrigeration system recommended is

A. Simple evaporative type
B. Boot-strap type
C. Regenerative type
D. Boot strap evaporative type
Answer» D. Boot strap evaporative type
7.

## The air craft system giving Lowest Dry Air Rated Turbine discharge temperature at supersonic cruising speeds of the plane, is

A. Reduced ambient system of Refrigeration
B. Boot-strap system of Refrigeration
C. Regenerative system of Refrigeration
D. Boot strap evaporative system of Refrigeration
Answer» D. Boot strap evaporative system of Refrigeration
8.

## There are two cooling turbines in

A. Reduced ambient system of Refrigeration
B. Boot-strap system of Refrigeration
C. Regenerative system of Refrigeration
D. Boot strap evaporative system of Refrigeration
Answer» A. Reduced ambient system of Refrigeration
9.

## There are two stages of compression of air in

A. Reduced ambient system of Refrigeration
B. Boot-strap system of Refrigeration
C. Regenerative system of Refrigeration
D. Simple evaporative system of Refrigeration
Answer» B. Boot-strap system of Refrigeration
10.

## The amount of heat absorbed by the system at low temperature is

A. COP
B. Refrigerating effect
C. work done on the system
D. refrigeration efficiency
Answer» B. Refrigerating effect
11.

## No refrigerator using reversed Carnot cycle has been constructed because

A. it is less efficient
B. it is uneconomical
C. isentropic portions of cycle require low speeds where as isothermal portions require high speeds
D. isentropic portions of cycle require high speeds where as isothermal portions require low speeds
Answer» D. isentropic portions of cycle require high speeds where as isothermal portions require low speeds
12.

## A refrigeration cycle is usually a

A. open cycle
B. closed cycle
C. mixed cycle
D. Hybrid cycle
Answer» B. closed cycle
13.

## Co-efficient of performance of a Reversed Carnot cycle refrigerator working between higher temperature T2 and lower temperature T1

A. will increase with increase in T1 keeping T2 fixed
B. will decrease with increase in T1 keeping T2 fixed
C. will first increase with increase in T1 and then decrease with increase T1 keeping T2 fixed
D. None of the above
Answer» A. will increase with increase in T1 keeping T2 fixed
14.

## Bell-Colemann cycle comprises

A. two isentropic processes and two adiabatic processes
B. two isentropic processes and two isothermal processes
C. two isentropic processes and two isobaric processes
D. two isentropic processes and two isochoric processes
Answer» C. two isentropic processes and two isobaric processes
15.

## The COP of Carnot Refrigerator is 3 and it produces 1 TR. The work that will be done is equal to

A. 70 kJ/min
B. 100 kJ/min
C. 200 kJ/min
D. 210 kJ/min
Answer» A. 70 kJ/min
16.

## In Bell – Colemann refrigerator for the same temperature range

A. COP of dense air system is equal to COP of open air system
B. COP of dense air system is lower than COP of open air system
C. COP of dense air system is higher than COP of open air system
D. COP of dense air system may be higher or lower than COP of open air system depending upon pressure ratio.
Answer» C. COP of dense air system is higher than COP of open air system
17.

## The air craft system giving Lowest Dry Air Rated Turbine discharge temperature at supersonic cruising speeds of the plane, is

A. Reduced ambient system of Refrigeration
B. Boot-strap system of Refrigeration
C. Regenerative system of Refrigeration
D. Boot strap evaporative system of Refrigeration
Answer» D. Boot strap evaporative system of Refrigeration
18.

## A Bell-Colemann cycle is

A. reversed Carnot Cycle
B. reversed Joule Cycle
C. reversed Rankine cycle
D. None of the above
Answer» B. reversed Joule Cycle
19.

## In a refrigeration cycle the heat is rejected by refrigerant at

A. expansion valve
B. compressor
C. condenser
D. all the above
Answer» C. condenser
20.

## A reversible refrigerator working between two fixed temperatures

A. has the same COP whatever the working substance
B. has its COP increased for working substance with high enthalpy of evaporation
C. has its COP increased for working substance with higher specific heats
D. none of the above
Answer» A. has the same COP whatever the working substance
Chapter: Air - Refrigeration
21.

## A reversible refrigerator working between two fixed temperatures

A. has the same COP whatever the working substance
B. has its COP increased for working substance with high enthalpy of evaporation
C. has its COP increased for working substance with higher specific heats
D. none of above
Answer» A. has the same COP whatever the working substance
Chapter: Vapour Compression Refrigeration
22.

## Heat is absorbed by the refrigerant, during vapour compression refrigeration cycle in

A. Compressor
B. Condenser
C. Evaporator
D. Throttle valve
Answer» C. Evaporator
23.

## In a simple saturated vapour compression cycle, the refrigerant is in superheated condition

A. before entering compressor
B. before entering condenser
C. before entering throttle valve
D. before entering evaporator
Answer» B. before entering condenser
24.

## Sub-cooling is a process of cooling the refrigerant in vapour compression refrigeration system

A. after compression
B. before compression
C. before Throttling
D. none of the above
Answer» C. before Throttling
25.

## The order in which main components of vapour compression refrigeration system are used is

A. compressor-evaporator-condenser-throttle valve
B. compressor-condenser-evaporator-throttle valve
C. compressor-throttle valve- evaporator-condenser
D. compressor-condenser- throttle valve- evaporator
Answer» D. compressor-condenser- throttle valve- evaporator
26.

## 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» B. between compressor and condenser
27.

## In vapour compression refrigeration cycle the following data is available Heat rejected in condenser = 65 KW Work done in compressor = 10 kw, then COP( refrigerator) is

A. 4.5
B. 5.5
C. 6.5
D. not possible to find with the given data
Answer» B. 5.5
28.

A. 3.5
B. 4.5
C. 5.5
D. 6.5
Answer» C. 5.5
29.

A. R-11
B. R-12
C. R-717
D. R-22
Answer» A. R-11
30.

A. R-11
B. R-12
C. R-717
D. R-22
Answer» A. R-11
31.

## 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» A. liquid trapped up in the head of cylinder may damage the compressor valves
32.

## An ideal refrigerant should have

A. low latent heat of vaporization
B. high critical temperature
C. high boiling point
D. high specific volume of vapour
Answer» B. high critical temperature
33.

## The refrigerant leaving throttle valve is

A. saturated liquid
B. saturated vapour
C. superheated vapour
D. fraction as saturated vapour and remainder as liquid
Answer» D. fraction as saturated vapour and remainder as liquid
34.

## Freon group of refrigerants

A. toxic
B. inflammable
C. non-toxic and non-inflammable
D. highly toxic and inflammable
Answer» C. non-toxic and non-inflammable
35.

## The leaks of refrigerant from a cycle may be detected by

A. halide torch test
B. sulphur candle test
C. soap and water test
D. any of the above
Answer» D. any of the above
36.

## 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» A. work done is increased
37.

## Heat is rejected by the refrigerant, during vapour compression refrigeration cycle in

A. Compressor
B. Condenser
C. Evaporator
D. Throttle valve
Answer» B. Condenser
38.

## 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» A. Vapour compression takes place in wet region
39.

A. R-11
B. R-12
C. R-717
D. R-22
Answer» D. R-22
40.

## With reciprocating compressor in vapour compression refrigeration system, wet compression 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» A. liquid trapped up in the head of cylinder may damage the compressor valves
41.

## An ideal refrigerant should have

A. low latent heat of vaporization
B. lower critical temperature
C. lower boiling point
D. high specific volume of vapour
Answer» C. lower boiling point
42.

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

A. C.O.P is reduced
B. C.O.P is increased
C. Work done is reduced
D. Refrigerating effect is reduced
Answer» A. C.O.P is reduced
Chapter: Principles of Evaporators, Condensers, Compressor and Expansion Devices
43.

## Heat is absorbed by a refrigerant, during a refrigeration cycle in a

A. condenser
B. evaporator
C. compressor
D. throttle valve
Answer» B. evaporator
44.

## What is the effect of frost on the cooling coils of the evaporator of refrigeration system

A. It reduces the life of cooling coils
B. It increases the compressor pressure
C. It makes the compressor run for comparatively short runs
D. It acts as the insulator and decreases the heat transfer rate
Answer» D. It acts as the insulator and decreases the heat transfer rate
45.

## The widely used refrigerant in domestic refrigerators is

A. Carbon-dioxide
B. Sulphur dioxide
C. Freon-12
D. Ammonia
Answer» C. Freon-12
46.

## Freon group refrigerants are

A. toxic
B. inflamma
C. nontoxic and inflammable
D. non- toxic & non-inflammable
Answer» D. non- toxic & non-inflammable
47.

## Latent heat of vaporization of a refrigerant ,at lower temperatures and pressures

A. increase
B. decreases
C. remains constant
D. unpredictable
Answer» A. increase
48.

## The refrigerant with highest critical pressure is

A. Carbon dioxide
B. Ammonia
C. Freon-11
D. Freon-22
Answer» B. Ammonia
49.

## The Refrigerant commonly used in commercial ice plants is

A. Carbon-dioxide
B. Air
C. Ammonia
D. Freon-12
Answer» C. Ammonia
50.

## Which of the following refrigerants has the lowest boiling point?

A. Freon-12
B. Carbon-dioxide
C. Ammonia
D. Sulphur dioxide
Answer» B. Carbon-dioxide
51.

## In a flooded type of Evaporator which of the following types of expansion device is utilized

A. Float Valve
B. Thermostatic device
C. Capillary tube
D. Self actuated expansion valve
Answer» A. Float Valve
52.

## Which of the following statements are TRUE?

A. A capillary tube is a variable opening area type expansion device
B. In a capillary tube pressure drop takes place due to fluid friction
C. In a capillary tube pressure drop takes place due to fluid acceleration
D. In a capillary tube pressure drop takes place due to fluid friction and acceleration
Answer» D. In a capillary tube pressure drop takes place due to fluid friction and acceleration
Chapter: Vapor Absorption Refrigeration System
53.

## Co-efficient of performance of vapour absorption refrigeration system as compared to that for vapour compression refrigeration system is

A. more
B. less
C. may be more or less
D. un - predictable
Answer» B. less
54.

## The function of compressor in vapour compression refrigeration system is performed in vapour absorption system by

A. generator
B. absorber
C. generator, absorber and liquid pump
D. absorber and liquid pump
Answer» C. generator, absorber and liquid pump
55.

## In vapour absorption refrigeration system heating in generator is done at 100°C, refrigeration in evaporator at 10°C and cooling by cooling water in condenser at 30°C. The (COP)max is

A. 0.5
B. 0.35
C. 2
D. in sufficient data
Answer» B. 0.35
56.

## Electrolux system of refrigeration has

A. only one liquid pump
B. only two liquid pumps
C. no liquid pump
D. none of the above
Answer» C. no liquid pump
57.

## Electrolux refrigerators has the following working substances

A. Hydrogen
B. Ammonia and Hydrogen
C. Ammonia and water
D. Ammonia, hydrogen and water
Answer» D. Ammonia, hydrogen and water
58.

## Which of the following system can be called as mechanical system of refrigeration

A. Vapour absorption system
B. Vapour compression system
C. Steam jet refrigeration system
D. None of the above
Answer» B. Vapour compression system
59.

## 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» A. higher than that using Lithium Bromide – water
60.

## 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» C. 1 to 2% of that required for vapour compression system
61.

## Work of compression of the fluid in vapour absorption refrigeration system as compared to that for vapour compression refrigeration system is

A. les
B. more
C. may be more or less
D. un - predictable
Answer» A. les
62.

## Munters Platen system of refrigeration is

A. Vapour absorption system with ammonia and water
B. Vapour compression system with ammonia as working substance
C. Electrolux system with Hydrogen, ammonia and water as working substances
D. none of the above
Answer» C. Electrolux system with Hydrogen, ammonia and water as working substances
63.

## Electrolux refrigerators is

A. Vapour compression refrigerator with one compressor
B. vapour absorption refrigerator with no pump
C. vapour absorption refrigerator with one aqua pump
D. None of the above
Answer» B. vapour absorption refrigerator with no pump
Chapter: Introduction to Air Conditioning Psychrometry
64.

A. 0
B. 0.5
C. 0.75
D. 1
Answer» D. 1
65.

## .In a psychrometric chart, the vertical lines parallel to the ordinate indicate

A. Dry bulb Temperature
B. Wet bulb Temperature
C. Specific humidity
D. Enthalpy of saturation
Answer» A. Dry bulb Temperature
66.

## Which of the following statements are TRUE?

A. Thermodynamic WBT is a property of moist air, while WBT as measured by wet bulb thermometer is not a property
B. Both the thermodynamic WBT and WBT as measured by wet bulb thermometer are properties of moist air
C. Under no circumstances, dry bulb and wet bulb temperatures are equal
D. Wet bulb temperature is always lower than dry bulb temperature, but higher than dew point temperature
Answer» A. Thermodynamic WBT is a property of moist air, while WBT as measured by wet bulb thermometer is not a property
67.

## Which of the following statements are TRUE?

A. During cooling and humidification process, the enthalpy of air decreases
B. During cooling and humidification process, the enthalpy of air increases
C. During cooling and humidification process, the enthalpy of air remains constant
D. During cooling and humidification process, the enthalpy of air may increase, decrease or remain constant depending upon the temperature of the wet surface
Answer» D. During cooling and humidification process, the enthalpy of air may increase, decrease or remain constant depending upon the temperature of the wet surface
68.

## 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» A. 20 C
69.

## 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» A. dew point
70.

## When moisture is added to air at constant dry bulb temperature, the process is known as

A. Sensible cooling
B. humidification
C. dehumidification
D. Chilling
Answer» B. humidification
71.

## Which of the following can be measured by a sling psychrometer?

A. Wet bulb temperature
B. Dry bulb as well as wet bulb temperatures
C. Specific humidity
D. Absolute humidity
Answer» B. Dry bulb as well as wet bulb temperatures
More MCQs
72.

## In which part of the vapour compression cycle there is abrupt change in pressure and temperature

A. Drier
B. Solenoid valve
C. Expansion valve
D. The change is gradual throughout the cycle
E. Evaporator
Answer» C. Expansion valve
73.

## The ratio of sensible heat to total heat is known as

A. Relative humidity
B. Humidification ratio
C. Sensible heat factor
D. Specific humidity
E. Dew point
Answer» C. Sensible heat factor
74.

## The flow of the refrigerant in a refrigeration cycle is controlled by

A. Copper tubing
B. Compressor
C. Expansion valve
D. Evaporator
E. Condenser
Answer» C. Expansion valve
75.

## The refrigerant used for the air-conditioning of passenger aircraft cabin is

A. Air
B. Carbondioxide
C. Freon 11
D. Ammonia
E. Freon 12
Answer» B. Carbondioxide
76.

## Under increased atmospheric pressure (as compared to the standard conditions) the steam will condense at

A. 100?C
B. More than 100?C
C. Depends on other conditions
D. Less than 100?C
E. Has nothing to do with pressure
Answer» B. More than 100?C
77.

## Which refrigerant has the highest critical point temperature?

A. Ammonia
B. Freon 11
C. Freon 12
D. Freon 22
E. None of the above
Answer» B. Freon 11
78.

## The ratio of high temperature to low temperature for reversed Carnot refrigerator is 1.25. The COP will be

A. 2
B. 3
C. 4
D. 5
E. All of the above
Answer» C. 4
79.

## When the higher temperature is fixed, the COP of a refrigerating machine can be improved by

A. Operating the machine at higher speeds
B. Operating the machine at lower speeds
C. Raising the higher temperature
D. Lowering the higher temperature
E. None of the above
Answer» C. Raising the higher temperature
80.

## A reversed Carnot cycle has a COP of 4. The ratio of higher temperature to lower temperature will be

A. 1.5
B. 2
C. 1.25
D. 2.5
E. None of the above
Answer» C. 1.25
81.

## A plate of vane used to direct or control movement of fluid or air within the confined area is known as

A. Baffle
B. Bellows
C. Regulator
D. Diffuser
E. None of the above
Answer» A. Baffle
82.

## The leaks of refrigerant from a cycle may be detected by

A. Halide torch test
B. Sulphur candle test
C. Soap and water test
D. Any of above
E. None of the above
Answer» D. Any of above
83.

## Super-conductors

A. Cannot be magnetised at low temperatures
B. Can be rubbed with other superconductors without frictional effects at low temperatures
C. Offer no resistance to flow of electricity at low remperatures
D. Offer no resistance to flow of heat at low temperatures
E. Offer no resistance to flow of fluids at low temperatures
Answer» C. Offer no resistance to flow of electricity at low remperatures
84.

## A desicant is

A. A process of removing heat under controlled conditions
B. A substance which reduces the viscosity of liquids
C. A solid substance capable of removing moisture from a gas, liquid or solid
D. Anammonia and a water solution
E. Heat given off by cargo
Answer» C. A solid substance capable of removing moisture from a gas, liquid or solid
85.

## A device designed to remove moisture from a refrigerant is called

A. Dehumidifier
B. Drier
C. Solenoid
D. Expansion valve
E. Humidstat
Answer» B. Drier
86.

## The difference between wet and dry bulb temperatures

A. Increases at atmospheric temperature
B. Increases as air gets wet
C. Increases as air gets drier
D. remains constant always
E. None of the above
Answer» C. Increases as air gets drier
87.

## In a vapour compression cycle the vapour as it leaves the compressor is

A. In liquid form
B. Wet vapour
C. Dry vapour
D. Dry and saturated vapour
E. None of the above
Answer» D. Dry and saturated vapour
88.

## Refrigerant No. 717 is

A. Ammonia
B. Freon 12
C. Carbondioxide
D. Freon 22
E. Methyl chloride
Answer» A. Ammonia
89.

## In a domestic refrigerator if the compressor runs continuously, it shows that

A. The system is working perfectly all right
B. The refrigeration is to full capacity
C. The system is overloaded
D. Any of the above
E. None of the above
Answer» C. The system is overloaded
90.

## The ability of an evaporator to absorb heat does not depends on

A. Temperature difference between the evaporator and the surrounding air
B. Its size, surface condition and material
C. Kind of refrigerant used
D. Velocity of turbulence
E. Compressor speed
Answer» C. Kind of refrigerant used
91.

## pH value of a brine solution is

A. More than
B. 14
C. 70
D. Less than 7
E. Could be any value
Answer» E. Could be any value
92.

## In case of freon as refrigerant the pipe lines should be of

A. Copper
B. Brass
C. Seamless steel tubes
D. Stainless steel tubes
E. None of the above
Answer» C. Seamless steel tubes
93.

## When Freon 12 is used as a refrigerant in vapour compression cycle, the mass circulated per ton of refrigerating effect will be nearly

A. 1.8 kg
B. 0.5 kg
C. 12 kg
D. 1 kg
E. 0.2 kg
Answer» A. 1.8 kg
94.

## In control cooling water system, chromates, phosphates and silicates are added to water

A. To remove odour
B. To increase remove foreign particle
C. To inhibit corrosion
D. To prevent scale formation
E. To prevent algae growth
Answer» C. To inhibit corrosion
95.

## In a psychrometric chart horizontal line indicate

A. Percentage humidity
B. Dew point temperature
C. Wet bulb temperature
D. Relative humidity
E. Dry bulb temperature
Answer» B. Dew point temperature
96.

## In a mechanical refrigeration system the highest temperature of refrigerant occurs

A. Between condenser and evaporator
B. In evaporator
C. Before expansion valve
D. Between compressor and condenser
E. Before expansion valve
Answer» D. Between compressor and condenser
97.

## Which of the following refrigerant has the freezing point?

A. Ammonia
B. Carbondioxide
C. Freon 11
D. Freon 22
E. All of the above
Answer» D. Freon 22
98.

## Dehumidification means

A. Removing humidity from a space
B. Reducing the quantity of water vapour in a space
C. Reducing the moisture content of a substance
D. Any of the above
E. None of the above
Answer» C. Reducing the moisture content of a substance
99.

## In a refrigeration system a condenser

A. Receives liquid refrigerant and supplies liquid refrigerant
B. Receives vapour refrigerant and supplies vapour refrigerant
C. Receives vapour refrigerant and supplies liquid refrigerant
D. Receives liquid refrigerant and supplies liquid refrigerant
E. None of the above
Answer» C. Receives vapour refrigerant and supplies liquid refrigerant
100.

## Dry ice is

A. Free from water
B. Free from dissolved air or gases
C. Does not contain impurities
D. Solidified form of carbondioxide
E. None of the above
Answer» D. Solidified form of carbondioxide

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