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Compressors Exam > Powerpoint notes pg. 1+2 > Flashcards

Powerpoint notes pg. 1+2 Flashcards

1
Q

Compressors are essentially ______ pumps

A

vapour

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2
Q

What can damage the compressor?

A

too much liquid

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3
Q

Vapour comes in as _____ temp, _____ pressure and leaves as _____ temp, _____ pressure

A

low, low,

high, high

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4
Q

How does a compressor raise temperature and pressure?

A

by decreasing volume and compressing

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5
Q

In a reciprocating compressor, the refrigerant vapour enters the cylinder when the pressure in the cylinder is _____ that of the suction line

A

below

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6
Q

In a reciprocating compressor, refrigerant vapour is discharged from the cylinder when pressure in the cylinder is ______ than the discharge line

A

greater

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7
Q

what term describes the space 1lb of gas occupies at a certain temperature and pressure?

A

specific volume

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8
Q

Increase in pressure means ________ in specific volume

A

decrease

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9
Q

______ _____rate is based on the density number in lbs in a cubic foot of gas

A

mass flow

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10
Q

________ _____ _____ is determined by the compressor type and design

A

volumetric flow rate

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11
Q

A compressor that delivers a constant volume of gas under a constant speed is called

A

positive displacement

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12
Q

How is capacity measured?

A

but/hr

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13
Q

capacity increases as mass flow rate increases resulting from a decrease in _______ _______

A

specific volume

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14
Q

capacity increases as specific volume decreases resulting from an increase in ____\_____

A

sst/pressure

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15
Q

Capacity increases as volumetric flow rate increases resulting from an increase in ____ _________

A

comp. displacement

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16
Q

Capacity increases as compression ratios decreases resulting from a decrease in _______ _______

A

specific volume

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17
Q

What are the main parts of a reciprocating compressor?

A 
crankshaft
crank throw
eccentric
piston
connecting rods 
cylinder
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18
Q

Mass flow rate =

A

Volumetric flow rate/specific volume

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19
Q

name two types of reciprocating compressor crankshafts

A

crank throw and eccentric

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20
Q

What is the purpose of the shaft seal?

A

keeps refrigerant in and air out

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21
Q

What type of compressor is the centrifugal?

A

non-positive displacement compressor

22
Q

Reciprocating compressors have pistons that when moving down pull air __ through the intake and when moving up push high pressure air ___ the exhaust valve

A

in, out

23
Q

Three types of valves in a reciprocating compressor

A

Reed valve, ring valve, discuss valve

24
Q

Methods of cooling for reciprocating compressors?

A

Air cooled, water cooled, refrigerant vapour cooled

25
Q

How do Hermetic reciprocating compressors look?

A

round and covered

26
Q

how do reciprocating semi-hermetic compressors look?

A

bolts everywhere

27
Q

Hermetic cooling method of cooling?

A

primary method of vapour

28
Q

Semi-hermetic primary method of cooling?

A

vapour/air/water

29
Q

Open drives primary methods of cooling?

A

air/water/oil

30
Q

Oil pressure in a refrigeration compressor is the difference between ______ pressure and ___ _____ pressure

A

crankcase pressure and oil pump pressure

31
Q

Net oil pressure =

A

oil pump discharge pressure - oil pump inlet pressure/crankcase pressure

32
Q

On what side of the compressor is the oil pump located?

A

low side

33
Q

Since the oil pump is on the low side of the compressor, the crankcase is the _ starting point for the oil pump

A

0

34
Q

Most systems operate at the design load less than ___ percent of the time due to variations in lighting, occupancy, ambient temp

A

20

35
Q

operating below design load is to rebalance at a lower ______ temp and pressure

A

evaporator

36
Q

lower evap pressure means lower suction pressure and this lower pressure means less _________ _______

A

compressor capacity

37
Q

operating at lower evap temp could result in:

A

frosted coils, poor oil return, poor humidity control, and short cycling

38
Q

Capacity control methods ; (3)

A

on/off, speed control, multiple compressors

39
Q

Name three types of mechanical unloaders? (Capacity control method)

A

cylinder bypass
suction cutoff
hydraulic

40
Q

what are mechanical unloaders operated by? (3)

A

pressure, electrically, or hydraulics

41
Q

what are mechanical unloaders controlled by?

A

temperature or suction pressure

42
Q

(Capacity control method) Refrigerant hot gas bypass to ______ line and ________ inlet

A

suction line

evaporator inlet

43
Q

Rotary compressors capacity control?

A

speed control on/off

44
Q

Rotary compressors are _______ shaped

A

cylinder

45
Q

Scroll compressors have ___ % less moving parts, and are ___% more efficient

A

70% less

20% more

46
Q

scroll compressors have one fixed ____ and one vibrating against it

A

scroll

47
Q

three structural type of compressors

A

hermetic , semi hermetic , open drive

48
Q

how does a scroll compressor compress the vapour?

A

volume decreases as vapour flows from the outside of the scroll toward the middle

49
Q

positive displacement uses a decrease in _______ in order to compress

A

volume

50
Q

diffuser slows down the refrigerant and converts _______ energy into _______ pressure

A

kinetic energy

static pressure

51
Q

what creates the pressure differential?

A

speeding up and slowing down

Compressors Exam (9 decks)

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