Refrigeration and Air-Conditioning



Multiple Choice Questions (MCQs)

1   The heat removing capacity of one ton of refrigeration is equal to
    (A)   21 kJ/min
    (B)   210 kJ/min
    (C)   3.5 kJ/min
    (D)   350 kJ/min

2   One ton of refrigeration means that
    (A)   One ton is the total mass of the machine
    (B)   One ton of refrigerant is used
    (C)   One ton of water is converted
    (D)   One ton of ice when melts from and at 0⁰C in 24hours, the refrigeration effect produced is equivalent to 210 kJ/min

3   The coefficient of performance of heat pump is always
    (A)   Equal to one
    (B)   Less than one
    (C)   Greater than one
    (D)   Equal to half of refrigerator

4   If the condenser and evaporator temperatures are 312K and 273K respectively, then COP of reversed Carnot cycle is
    (A)   5
    (B)   7
    (C)   9
    (D)   10

5   Air refrigeration cycle is used in
    (A)   Commercial refrigerators
    (B)   Domestic refrigerators
    (C)   Air conditioning
    (D)   Passenger aircraft

6   In refrigerating machine, heat rejected is —– heat absorbed.
    (A)   Equal to
    (B)   Less than
    (C)   Greater than
    (D)   Less than or equal to

7   Air refrigerator works on
    (A)   Carnot cycle
    (B)   Reversed Carnot cycle
    (C)   Vapor Compression cycle
    (D)   Bell Coleman cycle

8   For a refrigerating system that works on Bell-Coleman cycle, which one of the following is not a process of the cycle?
    (A)   Isentropic compression process
    (B)   Constant pressure cooling process
    (C)   Isothermal expansion process
    (D)   Constant pressure expansion process

9   Reverse Carnot cycle has the following two combination of processes
    (A)   Isothermal-isobaric
    (B)   Isothermal-Isentropic
    (C)   Isobaric-Isentropic
    (D)   Isentropic-Isochoric

10   Bell Coleman cycle has the following two combination of processes
    (A)   Isothermal-isobaric
    (B)   Isothermal-Isentropic
    (C)   Isobaric-Isentropic
    (D)   Isentropic-Isochoric

11   In a refrigeration system, the expansion device is connected between the
    (A)   Condenser and receiver
    (B)   Compressor and condenser
    (C)   Receiver and evaporator
    (D)   Evaporator and compressor

12   Select most widely used refrigeration cycle in use today
    (A)   Reversed Carnot cycle
    (B)   Bell Coleman cycle
    (C)   Vapor compression cycle
    (D)   Vapor absorption cycle

13   Select sources of heating the air craft
    (A)   Solar radiation
    (B)   Occupants and equipment
    (C)   Skin friction due to fast movement
    (D)   Represent all the given options

14   The C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.
    (A)   Same
    (B)   Higher
    (C)   Lower
    (D)   None of these

15   A refrigeration system
    (A)   Removes heat from a low temperature body and delivers it to a high temperature body
    (B)   Removes heat from a high temperature body and delivers it to a low temperature body
    (C)   Rejects energy to a low temperature body
    (D)   None of the above

16   In vapor compression cycle, heat is rejected by refrigerant in a
    (A)   compressor
    (B)   condenser
    (C)   expansion valve
    (D)   evaporator

17   The higher temperature in vapour compression cycle occurs at
    (A)   Compressor discharge
    (B)   Receiver
    (C)   Evaporator
    (D)   After expansion

18   Montreal protocol is related to the
    (A)   Ozone layer depletion
    (B)   Global warming
    (C)   Sustainable development
    (D)   Food security

19   Which of the following are ozone depleting substances?
    (A)   Chlorofluorocarbons (CFCs)
    (B)   Hydrofluorocarbons (HFCs)
    (C)   Hydrochlorofluorocarbons (HCFCs)
    (D)   Both CFCs and HCFCS

20   What is the value of C.O.P. of VCR cycle?
    (A)   h1 – h2 / h1 – h4
    (B)   h1 – h4 / h2 – h1
    (C)   h2 – h1 / h4 – h1
    (D)   h1 – h3 / h2 – h1

21   When refrigerants take a direct part in the refrigeration system, then these types of refrigerants are called?
    (A)   Primary Refrigerant
    (B)   Secondary Refrigerant
    (C)   Mixed Refrigerant
    (D)   None of the above

22   Refrigerant is
    (A)   Heat carrying medium
    (B)   Heat storing medium
    (C)   Heat dissipating medium
    (D)   Represent all the given options

23   The COP of a Carnot refrigerating machine is 7.8. What will be the COP of heat pump?
    (A)   9.8
    (B)   6.8
    (C)   7.8
    (D)   8.8

24   The relative coefficient of performance (C.O.P.) is equal to…….
    (A)   Theoretical C.O.P./Actual C.O.P.
    (B)   Actual C.O.P./Theoretical C.O.P.
    (C)   Theoretical C.O.P. x Actual C.O.P.
    (D)   Theoretical C.O.P. + Actual C.O.P.

25   In refrigeration cycle, the flow of refrigerant is controlled by ….
    (A)   Condenser
    (B)   Evaporator
    (C)   Expansion Valve
    (D)   Compressor

26   Identify refrigeration cycle as given below sketch
    (A)   Vapour compression cycle
    (B)   Reverse Carnot cycle
    (C)   Bell Coleman cycle
    (D)   Air Refrigeration cycle

27   Ideally two-phase mixture refrigerant enters into………
    (A)   Compressor
    (B)   Evaporator
    (C)   Condenser
    (D)   Expansion valve

28   Refrigeration cycle work on
    (A)   First Law of Thermodynamic
    (B)   Second Law of Thermodynamic
    (C)   Third Law of Thermodynamic
    (D)   None of the above

29   In refrigerating machine, heat rejected is……….heat absorbed.
    (A)   Equal to
    (B)   Less than
    (C)   Greater than
    (D)   Less than or equal to

30   Select the odd one out with respect to Bell Coleman cycle
    (A)   Compressor
    (B)   Condenser
    (C)   Expander
    (D)   Refrigerator

31   In ideal VCR cycle, phase of refrigerant at the exit of compressor will be
    (A)   Dry
    (B)   Wet
    (C)   Superheated
    (D)   Subcooled liquid

32   Subcooling of vapor compression cycle increases
    (A)   Life of compressor
    (B)   COP of cycle
    (C)   Life of compressor as well as COP of cycle
    (D)   Work requirement of compressor

33   Select the cycle shown in figure

    (A)   Reversed Carnot cycle
    (B)   Vapor absorption cycle
    (C)   Vapor compression cycle
    (D)   Bell Coleman cycle

34   Superheating is the process of heating the refrigerant above its normal boiling point under pressure in VCR cycle
    (A)   before compression
    (B)   after compression
    (C)   before expansion
    (D)   after expansion

35   In general refrigerant expression: R(m-1) (n+1) q, “n” is represented by
    (A)   hydrogen atom
    (B)   carbon atom
    (C)   fluorine atom
    (D)   chlorine atom

36   Select the most suitable option from the following with respect to moisture present in the VCR cycle
    (A)   Expansion valve chock up
    (B)   Compressor will run dry
    (C)   Compressor will prone to burst
    (D)   Represent all the given options

37   Sulphur candle can be used to detect which type of refrigerant
    (A)   CO2
    (B)   Ammonia
    (C)   R12
    (D)   SO2

38   Select the correct operations from the following before charging the refrigerant. 1. Evacuate the system 2. Connect a refrigerant cylinder to charging manifold with hoses. 3. Charge with only correct refrigerant. 4. Service connection lines must be clean and free of air. Clean lines by flushing refrigerant through hoses before charging
    (A)   only 1 & 3 are correct
    (B)   only 2 & 4 are correct
    (C)   Only 3 & 4 are correct
    (D)   All are correct

39   Dichlorodifluoromethane is
    (A)   R11
    (B)   R12
    (C)   R13
    (D)   R14

40   Which component is absent in Vapor absorption cycle?
    (A)   Condenser
    (B)   Evaporator
    (C)   Compressor
    (D)   Expansion valve

41   If pressure ratio is 5 and γ=1.4, then find COP of Bell Coleman refrigerator
    (A)   1.7
    (B)   3.1
    (C)   5.1
    (D)   4.2

42   Dehumidification of air is normally done by _______
    (A)   Heating
    (B)   Cooling
    (C)   Superheating
    (D)   Injecting water spray

43   Dew point temperature lines on the psychrometric chart are
    (A)   Horizontal
    (B)   Vertical
    (C)   Curved
    (D)   Straight inclined slopping downward to the right

44   The wet bulb temperature at 100% relative humidity as compared to dew point temperature is
    (A)   Same
    (B)   Lower
    (C)   Higher
    (D)   unpredictable

45   For sensible heating the air is passed over heating coils which may be
    (A)   Electric resistance coils
    (B)   Hot water passed through coils
    (C)   Steam passed through coils
    (D)   All of the above

46   The process used for summer air conditioning for hot and humid conditions are
    (A)   Heating and humidification
    (B)   Cooling and humidification
    (C)   Heating and dehumidification
    (D)   Cooling and dehumidification

47   During sensible cooling of air, relative humidity ____
    (A)   Increases
    (B)   Decrease
    (C)   Remains same
    (D)   None of the above

48   When air is passed over silica gel or activated alumina, the air gets ____________
    (A)   Heated and humidified
    (B)   Cooled and humidified
    (C)   Heated and dehumidified
    (D)   Cooled and dehumidified

49   Process of adding heat to moist air at the same specific humidity is known as ________
    (A)   Sensible heating
    (B)   Humidification
    (C)   Dehumidification
    (D)   Sensible cooling

50   Ratio of mass of water vapor associated with unit mass of dry air to the mass of water vapor associated with unit mass of saturated air at the same temperature is known as _____
    (A)   Relative humidity
    (B)   Absolute humidity
    (C)   Specific humidity
    (D)   Degree of saturation

51   Dry bulb temperature, wet bulb temperature and dew point are same for_________
    (A)   Dry air
    (B)   Saturated air
    (C)   Unsaturated air
    (D)   Moist air

52   Which type of evaporator is shown in figure
    (A)   Finned type
    (B)   Bare tube type
    (C)   Shell and tube type
    (D)   plate type

53   Which expansion device used in domestic refrigerator?
    (A)   Electrically operated throttling valve
    (B)   Manually operated valve
    (C)   Thermostatic valve
    (D)   Capillary tube

54   Thermostatic expansion valve responds to
    (A)   Suction superheat
    (B)   Liquid subcooling
    (C)   Suction pressure
    (D)   Discharge pressure

55   Automatic expansion valve responds to
    (A)   Suction superheat
    (B)   Liquid subcooling
    (C)   Suction pressure
    (D)   Discharge pressure

56   Which expansion device doesn’t adjust itself to seasonal variation?
    (A)   Capillary tube
    (B)   Thermostatic expansion valve
    (C)   Automatic expansion valve
    (D)   Float valve

57   “Heart” of any refrigeration and air conditioning system is
    (A)   Compressor
    (B)   Condenser
    (C)   Expansion valve
    (D)   Evaporator

58   To cut off and on the refrigerant in the system —– device is used.
    (A)   Solenoid valve
    (B)   Relay
    (C)   Drier
    (D)   Thermostatic switch

59   —– are used for cooling secondary refrigerant.
    (A)   Chillers
    (B)   Evaporators
    (C)   Condensers
    (D)   anyone can be used

60   Pressure in the capillary tube decreases due to following: 1. Frictional resistance offered by tube wall 2. Acceleration of refrigerant in the tube 3. Heat transfer from tube wall 4. Decrease in potential energy
    (A)   1 & 2 statements are correct
    (B)   3 & 4 statements are correct
    (C)   1, 2 & 4 statements are correct
    (D)   All statements are correct

61   Which type of condenser is shown in figure

    (A)   Evaporative type
    (B)   Forced convection type
    (C)   Natural convection type
    (D)   Water cooled type

62   The rate at which body produces heat is
    (A)   metabolic rate
    (B)   Heat storage rate
    (C)   work done by body
    (D)   rate of convection

63   Heat transfer by —– is always positive in thermal exchange of the body with environment.
    (A)   evaporation
    (B)   convection
    (C)   radiation
    (D)   heat storage in the body

64   Usual body temperature for a normal person is (in °C)
    (A)   37
    (B)   43
    (C)   40
    (D)   34

65   Heat exchange between person and its environment is expressed by —–relation. Qm: metabolic rate, W: work done by body, Qe: heat loss by evaporation, Qc: heat loss by convection, Qr: heat loss by radiation, Qs: rate of heat storage
    (A)   Qm – W = Qe ± Qr ± Qc ± Qs
    (B)   Qm – W = ± Qe ± Qr ± Qc ± Qs
    (C)   Qm – W = Qe ± Qr ± Qc – Qs
    (D)   Qm – W = Qe ± Qr ± Qc + Qs

66   Which of the following is not latent heat load?
    (A)   moisture from occupants
    (B)   moisture from cooking foods
    (C)   infiltrated moisture from outside air
    (D)   heat conducted through walls, floors and ceilings

67   Condition of a person which expresses satisfaction with the thermal environment is called
    (A)   Human comfort
    (B)   Human pleasure
    (C)   Human expectation
    (D)   Human contentment

68   Sensible heat loads include
    (A)   heat transmitted through walls, ceilings, floors
    (B)   heat transfer from light, motors machinery
    (C)   heat carried out by outside air through cracks
    (D)   Represent all the given option

69   A human body feels comfortable when heat produced by the metabolism of human body is equal to the
    (A)   Heat dissipated to the surroundings
    (B)   Heat stored in the human body
    (C)   Difference of (a) and (b)
    (D)   Sum of (a) and (b)

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