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Compressors Exam > RACT unit 23 > Flashcards

RACT unit 23 Flashcards

1
Q

Using two compressors can lower the ________ temperature and increases efficiency

A

discharge

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2
Q

______ refrigerant passes through the suction valve of the compressor to fill the cylinders

A

cool

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3
Q

Reciprocating compressors are used most frequently in _____ and _____ sized commercial refrigeration systems

A

small and medium

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4
Q

The screw compressor is used in ______ commercial and _______ systems

A

large commercial and industrial systems

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5
Q

The rotary, the scroll, along with the reciprocating compressors are used in ________ and light commercial air conditioning

A

residential

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6
Q

Centrifugal compressors are used extensively for ___________ in large buildings

A

air-conditioning

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7
Q

A hermetic reciprocating compressor has a __________ mechanism. The same shaft drives the compressor and motor

A

direct drive

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8
Q

Difference between hermetic and semi hermetic

A

hermetic is welded and semi-hermetic is serviceable

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9
Q

What is the only way to service a hermetic compressor?

A

cutting open the shell

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10
Q

hermetic compressors usually have a _____________ system but smaller hermetics are splash lubricated

A

pressure lubrication

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11
Q

semi hermetic compressors are ______ together so that it is easier to service and repair

A

bolted

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12
Q

smaller semi hermitic compressor use _______ lubrication

A

splash type

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13
Q

larger semi hermetic compressors use ________ lubrication

A

pressure

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14
Q

Motor and crankshaft are connected in a semi hermetic compressor although the ________ is usually horizontal

A

crankshaft

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15
Q

Open drive compressors are manufactured in two styles; ______ drive and ______ drive

A

belt driven and direct drive

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16
Q

Any compressor with the drive on the outside of the casting must have a ____ _____ to keep the refrigerant from escaping

A

shaft seal

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17
Q

In belt drive compressors the compressor and motor shaft are _______

A

parallel

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18
Q

direct drive compressors have a coupling between the shafts, shafts must be in very good __________ to run correctly

A

alignment

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19
Q

rotary screw compressor has an open _____

A

motor

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20
Q

In a screw compressor, a ______ seal traps refrigerant in the compressor housing where the rotating shaft leaves the housing

A

shaft

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21
Q

Screw compressors are used in ______ systems

A

large

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22
Q

The ________ of a reciprocating compressor transmits the circular motion of the rods into a back-and-forth motion for the pistons

A

crankshaft

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23
Q

Crankshafts are normally manufactured or _____ iron or _____

A

cast iron or steel

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24
Q

The off-centre shafts normally have _____ main bearing surfaces. One is on the _____ end and the other on the other end

A

two

motor

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25
Q

some reciprocating compressor crankshafts are straight and have a cam-type arrangement called an ________

A

eccentric

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26
Q

All reciprocating compressor shafts must be ________

A

lubricated

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27
Q

Smaller reciprocating compressors using the splash system may have a ______ basin to catch oil and

A

catch

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28
Q

In a reciprocating compressor, when the compressor runs the oil is then slung to the outside of the __________ surface

A

crankshaft

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29
Q

some crankshafts are _________ and lubricated by a pressure lubrication system

A

drilled

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30
Q

(Recip) Connecting rods connect the ________ to the ______

A

crankshaft to the piston

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31
Q

(reciprocating) Two types of connecting rods; one fits the _______ with off centre throws and the other fits the ________ crankshaft

A

crankshaft

eccentric

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32
Q

(recip) rods with large holes in the shaft end are for ______ shafts

A

eccentric

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33
Q

Rods with smaller holes are for the _________ shafts and; these are split and have rod bolts

A

off-centre

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34
Q

The ______ is the part of the cylinder assembly exposed to the high pressure gas during compression

A

piston

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35
Q

Pistons have high pressure gas on _____ and suction or low pressure gas on the ______

A

top

bottom

36
Q

Piston rings are used on the larger pistons and are of two types; _______ and ____

A

compression and oil

37
Q

Smaller compressors use the oil on the cylinder walls as a _____

A

seal

38
Q

The valves in the top of the compressor determine the _______ the gas entering the compressor will flow

A

direction

39
Q

Reed valves and ring valves serve both the _____ and _______ ports of the compressor

A

suction and discharge ports

40
Q

The _____ _____ holds the suction and discharge flapper valves

A

valve plate

41
Q

The component that holds the top of the cylinder and its assembly together is the _____

A

head

42
Q

The head contains ____ ________ gas from the cylinder until it moves into the discharge line

A

high pressure

43
Q

Heads need to accomplish two things;

A

hold the pressure in and hold the valve plate on the cylinder

44
Q

Mufflers are used in many fully _______ compressors to muffle compressor pulsation noise

A

hermetic

45
Q

Compressor housing holds the compressor and sometimes the ______

A

motor

46
Q

The two methods used to mount the compressor inside the shell are ______ mounting and _______ mounting

A

rigid mounting and spring mounting

47
Q

Internal ________ protection devices in hermetic motors protect the motor from overheating

A

overload

48
Q

open drive compressors are manufactured with the motor external to the __________ shell

A

compressor

49
Q

the shaft protrudes through the casing to the outside where either a _____ or _______ is attached

A

pulley or coupling

50
Q

The shaft seal has a rubbing surface designed to keep the refrigerant and the ________ separated

A

atmosphere

51
Q

A belt-drive compressor has the motor mounted at the ____ of the compressor and a pulley mounted on the ______ as well as the compressor

A

side

motor

52
Q

The pulley on the motor of a belt drive compressor is called the ______ pulley

A

drive

53
Q

The pulley on the compressor of a belt-drive compressor is called the _______ pulley

A

driven

54
Q

On a belt drive compressor, the drive pulley is sometimes adjustable, which allows the compressor ______ to be adjusted

A

speed

55
Q

direct drive compressors at limited to the _____ speed that the drive motor is turning

A

motor

56
Q

direct drive compressors can be ______ and serviced in place

A

rebuilt

57
Q

recip. compressor efficiency 1: Piston at the top of the stroke and starting down- When the piston has moved down far enough to create ___________ in the cylinder than is in the suction line the ______ valve will open and cylinder will start to fill

A

less pressure

flapper valve

58
Q

Recip. compressor efficiency 2: Piston continues to the bottom of the stroke- At this point the cylinder is nearly as full as it’s going to get. There is a very slight _______ at the bottom of the stroke as the crankshaft carries the road around the bottom of the stroke

A

time lag

59
Q

Recip. compressor 3: Piston is starting up - The rod throw is past bottom dead center and the piston starts up. When the cylinder is as full as it’s going to get, the _______ flapper valve closes.

A

suction

60
Q

recip. comp efficiency 4: The piston proceeds to the top of the stroke - When the piston reaches nearly the top, pressure in the cylinder becomes _______ than the pressure in the discharge line

A

greater

61
Q

Recip. compressor 5: The piston is at exactly top dead centre - The piston is as close to the top as it can. There has to be a certain amount of clearance in the valve assemblies and between the piston and the head, or they would touch. This clearance is know as ________ volume. Piston will push as much gas out as time and clearance volume allow

A

clearance

62
Q

the discuss valve allows a closer tolerance inside the compressor cylinder at top _____ centre

A

dead

63
Q

The closer tolerance makes the compressor more efficient because it reduces the ______________

A

clearance volume

64
Q

DOE?

A

department of energy

65
Q

SEER is calculated based on total amount of cooling (in btu) over the season divided by the total number of ________ it will consume

A

watt hours

66
Q

The two scrolls in a scroll compressor are often referred to as _______ _______

A

involute spirals

67
Q

Scroll compressors conduct their ______, compression, and discharge phases simultaneously

A

intake

68
Q

Scroll compressor is known as a ____________________ type because the scroll compressor compresses the discharge gas to a zero volume

A

fixed compression ratio

69
Q

Scroll compressors have the ability to handle some ______

A

liquid

70
Q

Scroll type compressors are gaining popularity due to the efficiency, _______, and quieter operations

A

reliability

71
Q

As the orbiting scrolls orbit, centrifugal forces on the sides of the mating scrolls, along with lubricating oil, form a seal that prevents ____ pocket leakage (known as flank sealing)

A

gas pocket leakage

72
Q

Advancements in scroll compressor design allow the compressor to have a two-step capacity of either ___% or ____%

A

67% or 100%

73
Q

The rotor shaft and impellers are the only moving parts in the _________ compressor

A

centrifugal

74
Q

Soft starting reduces __________ currents at start up

A

high inrush

75
Q

The centrifugal compressor is ___ free

A

oil

76
Q

In a centrifugal compressor, the rotor shaft has ___________ levitated bearings for frictionless operation

A

magnetically

77
Q

In most compressors a large amount of liquid (liquid slugging) will cause _________ damage

A

immediate

78
Q

When small amounts of liquid enter the compressor it ______ the oil which means no lubrication and can cause the compressor to fail

A

dilute

79
Q

Causes that may lead to liquid slugging a compressor with liquid refrigerant, which may in turn lead to electrical failures because of a motor seizure (name 5)

A 
metering device over feeding
low air circulation over evaporator 
low heat load 
evaporator fan motor not working
iced up evaporator coil
80
Q

A dirty evaporator will cause the suction pressure to _____

A

drop

81
Q

When suction vapour goes below normal, the vapour becomes less dense and gets thin (sometimes called ______ vapour)

A

rarified vapour

82
Q

Most manufacturers recommend that the compression ratio not be more than ___:1

A

12:1

83
Q

Dirty condensers and dirty evaporators cause the ______________ to rise

A

compression ratio

84
Q

Dirty condenser means high _____ pressure

A

head

85
Q

dirty evaporator means ____ suction pressure

A

low

Compressors Exam (9 decks)

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