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Second Half Book 2 > chapter 23 > Flashcards

chapter 23 Flashcards

1
Q

An automatic expansion or constant pressure valve is suitable when compressors are controlled by a:
Select one:

A.
Aquastat

B.
Humidistat

C.
Pressurestat

D.
Rheostat

E.
Thermostat

A

E.
Thermostat

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2
Q

One of the forces that tend to close the thermal expansion valve is the force exerted by the:
Select one:

A.
Receiver inlet pressure

B.
Thermal element

C.
Pressure in the condenser

D.
Evaporator pressure

E.
Compressor outlet pressure

A

D.
Evaporator pressure

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3
Q

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.
Select one:

A.
Speed control

B.
Compressor unloader

C.
Cylinder bypass

D.
Intermittent operation

E.
Hot gas bypass

A

E.
Hot gas bypass

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4
Q

The capillary tube is used to restrict the flow of liquid from the _____ and to maintain the pressure difference between these units.
Select one:

A.
Condenser to the compressor

B.
Receiver to the expansion valve

C.
Evaporator to the condenser

D.
Condenser to the evaporator

E.
Condenser to the receiver

A

D.
Condenser to the evaporator

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5
Q

The thermostatic expansion valve must admit enough liquid to maintain the superheat at the evaporator outlet at _____ to provide for maximum evaporator efficiency.
Select one:

A.
0°C to 1°C (32°F to 34°F)

B.
8°C to 9°C (46°F to 48°F)

C.
2°C to 3°C (36°F to 38°F)

D.
5°C to 6°C (41°F to 43°F)

E.
10°C to 11°C (50°F to 52°F)

A

D.
5°C to 6°C (41°F to 43°F)

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6
Q

One of the forces that tend to close the thermal expansion valve is the force exerted by the:
Select one:

A.
Spring

B.
Thermal element

C.
Compressor outlet pressure

D.
Receiver inlet pressure

E.
Pressure in the condenser

A

A.
Spring

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7
Q

One of the disadvantages of evaporator capacity control by face damper is that the:
Select one:

A.
Refrigerant volume to the space is reduced

B.
Temperature of the space is increased

C.
Air volume to the space is reduced

D.
Temperature of the space is reduced

E.
Refrigerant pressure to the space is reduced

A

C.
Air volume to the space is reduced

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8
Q

All of the following methods are used to control the refrigeration compressor output except:
Select one:

A.
Intermittent operation

B.
Variable inlet guide vanes

C.
Thermodynamic expansion valve

D.
Cylinder Unloaders

E.
Speed control

A

C.
Thermodynamic expansion valve

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9
Q

The high-pressure float valve is a liquid level operated control valve located on the:
Select one:

A.
Evaporator

B.
Downstream side of the expansion valve

C.
High-pressure side of the system

D.
Downstream side of the evaporator

E.
Low-pressure side of the system

A

C.
High-pressure side of the system

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10
Q

One of the safety devices on a centrifugal refrigeration compressor that acts preventing the compressor from being started is the _____ switch.
Select one:

A.
Refrigerant level low

B.
Evaporator temperature high

C.
Vane closed

D.
Condenser temperature low

E.
Refrigerant level high

A

C.
Vane closed

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11
Q

The bulb of a thermostatic expansion valve is usually charged with:
Select one:

A.
Nitrogen

B.
Alcohol

C.
Instrument oil

D.
The same refrigerant that is used in the system

E.
Water

A

D.
The same refrigerant that is used in the system

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12
Q

The charge of refrigerant in a system with a high-pressure float valve is critical. Insufficient liquid refrigerant in the evaporator may starve the:
Select one:

A.
Evaporator and reduce the capacity of the system

B.
Evaporator and increase the capacity of the system

C.
Receiver and increase the capacity of the system

D.
Condenser and increase the capacity of the system

E.
Condenser and reduce the capacity of the system

A

A.
Evaporator and reduce the capacity of the system

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13
Q

A refrigeration system using a high-pressure float provides for storage of the refrigerant in the:
Select one:

A.
Compressor

B.
Condenser

C.
Evaporator

D.
Receiver

E.
Expansion valve

A

C.
Evaporator

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14
Q

What is the purpose of the “weighted valve pin” used with a high-pressure float valve?
Select one:

A.
Control the pressure in the refrigeration system

B.
Control the flow of refrigerant into the evaporator

C.
Maintain a back pressure in the condenser

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

E.
Control the flow of refrigerant into the condenser

A

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

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15
Q

All of the following methods are used to control the refrigeration compressor output except:
Select one:

A.
Hot gas bypass

B.
Cylinder unloaders

C.
High-pressure float

D.
Intermittent operation

E.
Cylinder bypass

A

C.
High-pressure float

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16
Q

The bulb of a thermostatic expansion valve is sensitive to the:
Select one:

A.
Temperature changes in the condenser

B.
Temperature changes in the evaporator

C.
Temperature changes in the receiver

D.
Pressure changes in the evaporator

E.
Pressure changes in the condenser

A

B.
Temperature changes in the evaporator

17
Q

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:
Select one:

A.
Outlet of the evaporator instead of the inlet

B.
Outlet of the condenser instead of the inlet

C.
Outlet of the receiver instead of the inlet

D.
Inlet of the evaporator instead of the outlet

E.
Inlet of the condenser instead of the outlet

A

A.
Outlet of the evaporator instead of the inlet

18
Q

The force that tends to open the thermal expansion valve is the force exerted by the:
Select one:

A.
Spring

B.
Thermal element

C.
Pressure in the evaporator

D.
Compressor outlet pressure

E.
Pressure in the condenser

A

B.
Thermal element

19
Q

Variable inlet guide vanes are used on _____ refrigeration compressors.
Select one:

A.
Positive displacement

B.
Rotary screw

C.
Centrifugal

D.
Rotary lobe

E.
Sliding vane

A

C.
Centrifugal

20
Q

Use of evaporator capacity control requires simultaneous control of the:
Select one:

A.
Compressor capacity

B.
Compressor pressure

C.
Condenser temperature

D.
Evaporator volume

E.
Condenser capacity

A

A.
Compressor capacity

21
Q

The flow of liquid refrigerant from the high to the low-pressure side of the system must be controlled to maintain the desired temperature of the:
Select one:

A.
Cooled medium

B.
Cooling air

C.
Condenser

D.
Compressor inlet

E.
Compressor discharge

A

A.
Cooled medium

22
Q

The low-pressure float valve is a liquid level operated control valve used to maintain a constant level of liquid refrigerant in the:
Select one:

A.
Condenser

B.
Receiver

C.
Expansion valve

D.
Compressor

E.
Evaporator

A

E.
Evaporator

23
Q

The automatic expansion valve is a liquid refrigerant control valve that maintains a constant _____ during the time the compressor is operating, regardless of load.
Select one:

A.
Evaporator temperature

B.
Condenser pressure

C.
Compressor discharge pressure

D.
Evaporator pressure

E.
Condenser temperature

A

D.
Evaporator pressure

24
Q

All of the following methods are used to control the refrigeration compressor output except:
Select one:

A.
Cylinder Unloaders

B.
Capillary tube

C.
Speed control

D.
Intermittent operation

E.
Suction throttling

A

B.
Capillary tube

25
Q

The most common application of evaporator capacity control is to use:
Select one:

A.
Sectional receivers

B.
Sectional condensers

C.
Variable evaporators

D.
Sectional evaporators

E.
Adjustable evaporators

A

D.
Sectional evaporators

26
Q

The charge of refrigerant in a system with a high-pressure float valve is critical. Too much refrigerant in the evaporator may cause:
Select one:

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.
Vapour to be carried over to the condenser with the liquid

D.
Liquid to be carried over to the condenser with the vapour

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

27
Q

One design of a refrigeration compressor cylinder unloader works by keeping:
Select one:

A.
The intake valves in the open position

B.
Both intake and exhaust valves in the open position

C.
The exhaust valves in the closed position

D.
The intake valves in the closed position

E.
The exhaust valves in the open position

A

A.
The intake valves in the open position

28
Q

With the intermittent operation system of refrigeration compressor control the compressor is started and stopped based on the:
Select one:

A.
Temperature of the refrigerant

B.
Pressure of the condenser

C.
Temperature of the substance to be cooled

D.
Temperature of the condenser

E.
Size of the substance to be cooled

A

C.
Temperature of the substance to be cooled

29
Q

The cylinder bypass method of refrigeration compressor capacity control requires returning high-temperature vapour back to the compressor inlet this hot vapor must be tempered by using the _____ expansion valve to mix a low-temperature saturated mixture of refrigerant with the compressor discharge vapor.
Select one:

A.
Thermodynamic

B.
Hand

C.
Automatic

D.
Capillary

E.
De-superheating

A

E.
De-superheating

30
Q

The thermal expansion valve works quite satisfactorily provided the pressure drop across the:
Select one:

A.
Evaporator is small

B.
Receiver is small

C.
Evaporator is large

D.
Condenser is small

E.
Condenser is large

A

A.
Evaporator is small

Second Half Book 2 (15 decks)

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