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Book 2 PanGlobal Assessment Test > Chapter 23 Refrigeration Metering Devices & Capacity Controls > Flashcards

Chapter 23 Refrigeration Metering Devices & Capacity Controls Flashcards

1
Q 
1. The most widely used refrigerant control is the:
A. Automatic expansion valve
B. Hand operated expansion valve
C. Low pressure float
D. Thermostatic expansion valve
E. Capillary tube
A

D. Thermostatic expansion valve

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2
Q
  1. To compensate for a large pressure drop in an evaporator, the thermal expansion
    valve is equipped with an equalizing line which connects the underside of the
    diaphragm or bellows with the:
    A. Outlet of the evaporator instead of the inlet
    B. Outlet of the condenser instead of the inlet
    C. Inlet of the evaporator instead of the outlet
    D. Inlet of the condenser instead of the outlet
    E. Outlet of the receiver instead of the inlet
A

A. Outlet of the evaporator instead of the inlet

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3
Q 
3. The bulb of a thermostatic expansion valve is sensitive to the:
A. Temperature changes in the evaporator
B. Temperature changes in the condenser
C. Pressure changes in the evaporator
D. Pressure changes in the condenser
E. Temperature changes in the receiver
A

A. Temperature changes in the evaporator

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4
Q
  1. The bulb of a thermostatic expansion valve is usually charged with:
    A. Alcohol
    B. Water
    C. Instrument oil
    D. Nitrogen
    E. The same refrigerant that is used in the system
A

E. The same refrigerant that is used in the system

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5
Q
  1. What is the purpose of the weighted valve pin” used with a high-pressure float
    valve?
    A. Control the flow of refrigerant into the evaporator
    B. Control the flow of refrigerant into the condenser
    C. Maintain a back pressure in the condenser
    D. Control the pressure in the refrigeration system
    E. Reduce the amount of line frosting after the float valve
A

E. Reduce the amount of line frosting after the float valve

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6
Q
  1. The cylinder bypass method of refrigeration compressor capacity control requires
    returning high-temperature vapour back to the compressor inlet this hot vapor must
    Book 2 PanGlobal Page 138
    be tempered by using the _____ expansion valve to mix a low-temperature
    saturated mixture of refrigerant with the compressor discharge vapor.
    A. Automatic
    B. Thermodynamic
    C. De-superheating
    D. Hand
    E. Capillary
A

C. De-superheating

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7
Q
  1. The charge of refrigerant in a system with a high-pressure float valve is critical.
    Insufficient liquid refrigerant in the evaporator may starve the:
    A. Condenser and reduce the capacity of the system
    B. Evaporator and increase the capacity of the system
    C. Evaporator and reduce the capacity of the system
    D. Condenser and increase the capacity of the system
    E. Receiver and increase the capacity of the system
A

C. Evaporator and reduce the capacity of the system

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8
Q
  1. The low-pressure float valve is a liquid level operated control valve used to
    maintain a constant level of liquid refrigerant in the:
    A. Condenser
    B. Compressor
    C. Evaporator
    D. Expansion valve
    E. Receiver
A

C. Evaporator

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9
Q
  1. The automatic expansion valve is a liquid refrigerant control valve that maintains
    a constant _____ during the time the compressor is operating, regardless of load.
    A. Condenser pressure
    B. Evaporator pressure
    C. Evaporator temperature
    D. Condenser temperature
    E. Compressor discharge pressure
A

B. Evaporator pressure

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10
Q 
10.An automatic expansion or constant pressure valve is suitable when compressors
are controlled by a:
A. Pressurestat
B. Humidistat
C. Thermostat
D. Rheostat
E. Aquastat
A

C. Thermostat

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11
Q 
11.All of the following methods are used to control the refrigeration compressor output
except:
A. Intermittent operation
B. Cylinder Unloaders
C. Speed control
D. Variable inlet guide vanes
E. Thermodynamic expansion valve
A

E. Thermodynamic expansion valve

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12
Q 
12.A disadvantage of the \_\_\_\_\_ method of capacity control is that the power required
by the compressor does not change even though the amount of system cooling
effect is reduced.
A. Cylinder bypass
B. Intermittent operation
C. Speed control
D. Hot gas bypass
E. Compressor unloader
A

D. Hot gas bypass

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13
Q

13.One design of a refrigeration compressor cylinder unloader works by keeping:
A. The exhaust valves in the open position
B. The intake valves in the open position
C. The intake valves in the closed position
D. The exhaust valves in the closed position
E. Both intake and exhaust valves in the open position

A

B. The intake valves in the open position

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14
Q

14.One of the safety devices on a centrifugal refrigeration compressor that acts
preventing the compressor from being started is the _____ switch.
A. Vane closed
B. Refrigerant level low
C. Refrigerant level high
D. Condenser temperature low
E. Evaporator temperature high

A

A. Vane closed

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15
Q

15.One of the disadvantages of evaporator capacity control by face damper is that
the:
A. Air volume to the space is reduced
B. Refrigerant volume to the space is reduced
C. Temperature of the space is reduced
D. Temperature of the space is increased
E. Refrigerant pressure to the space is reduced

A

A. Air volume to the space is reduced

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16
Q 
16.The force that tends to open the thermal expansion valve is the force exerted by
the:
A. Pressure in the evaporator
B. Thermal element
C. Pressure in the condenser
D. Spring
E. Compressor outlet pressure
A

B. Thermal element

17
Q

17.The charge of refrigerant in a system with a high-pressure float valve is critical.
Insufficient liquid refrigerant in the evaporator may starve the:
A. Condenser and reduce the capacity of the system
B. Evaporator and increase the capacity of the system
C. Evaporator and reduce the capacity of the system
D. Condenser and increase the capacity of the system
E. Receiver and increase the capacity of the system

A

C. Evaporator and reduce the capacity of the system

18
Q 
18.The thermostatic expansion valve must admit enough liquid to maintain the
superheat at the evaporator outlet at \_\_\_\_\_ to provide for maximum evaporator
efficiency.
A. 0°C to 1°C (32°F to 34°F)
B. 5°C to 6°C (41°F to 43°F)
C. 8°C to 9°C (46°F to 48°F)
D. 2°C to 3°C (36°F to 38°F)
E. 10°C to 11°C (50°F to 52°F)
A

B. 5°C to 6°C (41°F to 43°F)

19
Q 
19.One of the forces that tend to close the thermal expansion valve is the force
exerted by the:
A. Pressure in the condenser
B. Thermal element
C. Spring
D. Receiver inlet pressure
E. Compressor outlet pressure
A

C. Spring

20
Q 
20.One of the forces that tend to close the thermal expansion valve is the force
exerted by the:
A. Pressure in the condenser
B. Thermal element
C. Receiver inlet pressure
D. Evaporator pressure
E. Compressor outlet pressure
A

D. Evaporator pressure

21
Q 
21.Use of evaporator capacity control requires simultaneous control of the:
A. Condenser capacity
B. Compressor capacity
C. Compressor pressure
D. Condenser temperature
E. Evaporator volume
A

B. Compressor capacity

22
Q

22.The capillary tube is used to restrict the flow of liquid from the _____ and to
maintain the pressure difference between these units.
A. Evaporator to the condenser
B. Condenser to the compressor
C. Condenser to the receiver
D. Condenser to the evaporator
E. Receiver to the expansion valve

A

D. Condenser to the evaporator

23
Q

23.The charge of refrigerant in a system with a high-pressure float valve is critical.
Too much refrigerant in the evaporator may cause:
A. Vapour to be carried over to the compressor with the liquid
B. Liquid to be carried over to the compressor with the vapour
C. Liquid to be carried over to the condenser with the vapour
D. Vapour to be carried over to the condenser with the liquid
E. Liquid to be carried over to the receiver with the vapour

A

B. Liquid to be carried over to the compressor with the vapour

24
Q 
24.The thermal expansion valve works quite satisfactorily provided the pressure drop
across the:
A. Evaporator is large
B. Receiver is small
C. Condenser is small
D. Condenser is large
E. Evaporator is small
A

E. Evaporator is small

25
Q 
25.All of the following methods are used to control the refrigeration compressor output
except:
A. Intermittent operation
B. Cylinder Unloaders
C. Speed control
D. Capillary tube
E. Suction throttling
A

D. Capillary tube

26
Q

26.What is the purpose of the weighted valve pin” used with a high-pressure float
valve?
A. Control the flow of refrigerant into the evaporator
B. Control the flow of refrigerant into the condenser
C. Maintain a back pressure in the condenser
D. Control the pressure in the refrigeration system
E. Reduce the amount of line frosting after the float valve

A

E. Reduce the amount of line frosting after the float valve

27
Q

27.With the intermittent operation system of refrigeration compressor control the
compressor is started and stopped based on the:
A. Temperature of the substance to be cooled
B. Pressure of the condenser
C. Temperature of the refrigerant
D. Temperature of the condenser
E. Size of the substance to be cooled

A

A. Temperature of the substance to be cooled

28
Q

28.The high-pressure float valve is a liquid level operated control valve located on the:
A. Low-pressure side of the system
B. Evaporator
C. Downstream side of the expansion valve
D. High-pressure side of the system
E. Downstream side of the evaporator

A

D. High-pressure side of the system

29
Q

29.Variable inlet guide vanes are used on _____ refrigeration compressors.

A. Positive displacement
B. Rotary screw
C. Sliding vane
D. Rotary lobe
E. Centrifugal
A

E. Centrifugal

30
Q 
30.The most common application of evaporator capacity control is to use:
A. Sectional condensers
B. Sectional receivers
C. Variable evaporators
D. Adjustable evaporators
E. Sectional evaporators
A

E. Sectional evaporators

Book 2 PanGlobal Assessment Test (40 decks)

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