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Compressors Exam > Powerpoint notes pg. 3+4 > Flashcards

Powerpoint notes pg. 3+4 Flashcards

1
Q

Screw compressors are ________ displacement compressors

A

positive

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2
Q

The rotation of the two screws in a screw compressor causes the chambers to move vapour from ______ to _______ side

A

suction to discharge

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3
Q

Screw compressor construction and types; (2)

A

male rotor driven

female rotor driven

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4
Q

Screw compressor capacity controls; (2)

A

speed control and slide vane

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5
Q

Centrifugal compressor is a ____________ displacement compressor

A

non-positive

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6
Q

In a centrifugal compressor, the motor drives the impeller which turns and sucks in refrigerant through the __________ and pushes out through the ________ line

A

intake suction line

discharge line

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7
Q

In a centrifugal comp the refrigerant goes through the _______ into the _______ and out the discharge line

A

diffuser into the vallute

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8
Q

The diffuser is a thin channel between the _______ and the ________

A

impeller and the vallute

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9
Q

purpose of the diffuser is to slow the refrigerant down and convert its _________ into ________ pressure

A

kinetic energy into static pressure

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10
Q

The increase in static pressure is known as _____ or ______ pressure

A

lift or head pressure

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11
Q

Lift/head pressure is the difference between the pressure of the refrigerant in the _________ and pressure of the refrigerant in the _________

A

condenser

evaporator

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12
Q

Single stage centrifugal compressor has ___ impeller

A

one

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13
Q

Multistage centrifugal compressor has _______ impellers

A

2 or more

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14
Q

Purpose of the economize is to reduce _________ by having a two stage pressure drop through the float section

A

flash gas

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15
Q

Purpose of purge unit :

A

remove non-condensable gases from the system

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16
Q

centrifugal capacity controls; (3)

A

variable inlet vanes

butterfly dampers

Speed control

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17
Q

Reciprocating Compressors- factors that control efficiency; (4)

A

piston/compressor displacement

suction/discharge valve designs

clearance picket sizes

number of cylinders

18
Q

Positive displacement compressors _______ a contained gas

A

squeeze

19
Q

Non-positive/dynamic compressor works to build up molecular velocities and converts this energy into ____________

A

static pressure

20
Q

Most compressors are limited to the types of _________ selected by the manufacturers

A

refrigerants

21
Q

Ref properties are different from ref to ref and will impact the operation of the ________

A

compressor

22
Q

Max discharge temperature is measured from the _____

A

head

23
Q

Max discharge temperature: _____F to ____F

A

225F to 275F

24
Q

Max suction temperature high temp application: ____F to ____F

A

65F to 95F

25
Q

Minimum suction superheat: ___F

A

20F

26
Q

Net positive oil pressure: ____psig to ____psig (minimum ____psig)

A

30 to 40psig and minimum 10psig

27
Q

SST?

A

saturation suction temp (PT CHART)

28
Q

SDT

A

saturated discharge temp (PT CHART)

29
Q

CFM?

A

Cubic feet per minute

30
Q

SEER?

A

Seasonal energy efficiency rating (btu output/watt input)

31
Q

EER?

A

Energy efficiency rating

32
Q

COP?

A

coefficient of performance (output/kw and input in btu)

33
Q

SPF?

A

Seasonal performance factor

34
Q

Maximum compression ratios:

Reciprocating:

  • single comp = ___ to ___
  • multiple comp = ___ to ___
A

10 to 1

20 to 1

35
Q

Maximum compression ratios:

Rotary compressor = ___ to ____

Centrifugal comp = ____ to ____

A

5 to 1

3 to 1

36
Q

Maximum compression ratios:

  • Screw compressor = ____ to ____
  • Scroll compressor = ____ to ____
A

20 to 1

20 to 1

37
Q

Flooding: liquid refrigerant returning to the compressor during the __________

A

running cycle

38
Q

Slugging: Extreme flood back of liquid refrigerant or oil, _________ migration results in liquid refrigerant in the crankcase

A

off cycle

39
Q

Migration: Off cycle refrigerant gas returning to a ____________ crankcase. gas condenses in the oil

A

cold compressor

40
Q

Liquid dilution: Crankcase has a mixture of _______ refrigerant and __________ refrigerant sinks to the bottom, and the oil floats on top

A

liquid refrigerant and oil liquid refrigerant

41
Q

Liquid washout: Compressor starting when crankcase has a mixture of _________ refrigerant and _____

A

liquid refrigerant and oil

Compressors Exam (9 decks)

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