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Refrig. Theory > Industrial > Flashcards

Industrial Flashcards

1
Q

What is a level control switch?

A

Magnetically actuated for close control of liquid level and maintains close control of liquid level. It is a metering device and can be used as a high side float.

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2
Q

What 2 types of compressors are used in industrial refrigeration?

A

screw and semi-hermitic

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3
Q

What is the benefit of screw compressors?

A

Require less maintenance and are efficient

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4
Q

What is the primary side of the ice rink?

A

The side that has the evaporative condenser and compressor which has the refrigerant in it.

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5
Q

What is the secondary side of the ice rink?

A

The ice sheet and evaporator which has the brine in it.

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6
Q

What are the 2 types of flooded evaporators used?

A

shell and tube and plate exchanger

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7
Q

In the flooded evaporator where is the primary (R-717) and secondary refrigerant (brine)?

A

In the shell and the brine is in the tubes

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8
Q

What does a surge drum do?

A

Prevents liquid from getting back to the compressor and is located on top of the flooded evaporator

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9
Q

What is the advantage of the plate heat exchanger?

A

It is smaller and less maintenance

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10
Q

Where is the high side float located and what does it do?

A

It is located between the condenser and evaporator. It responds to the load on the condenser. As the load increases it allows more liquid through the float valve into the condenser.

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11
Q

Where is the low side float located and how does it operate?

A

In the chiller or next to the chiller in a column of liquid. When liquid refrigerant level is low the valve allows liquid in to increase flow.

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12
Q

What is a high side float pilot operated valve?

A

Follows the rise and fall of the liquid column.

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13
Q

How does the evaporative condenser pump get its start?

A

Signal is received from discharge pressure control

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14
Q

Does oil cooling take priority over everything else? T or F

A

True

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15
Q

What is double indirect system?

A

Primary loop with two secondary loops

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16
Q

What is a reverse return system?

A

Keeps every pass across the rink the same distance to keep the pressure drop approximately the same.

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17
Q

25 ppm TLV/TWA

A

Exposure to 25 ppm for an 8 hour work day and a 40 hour work

week is permissible

18
Q

35 ppm ST/STEL

A

Exposure to 35 ppm must be limited to no more than 15 minutes

19
Q

300 ppm IDLH

A

Exposure to 300 ppm is Immediately Dangerous to Life and Health

20
Q

For R-717 how many BTU’S for latent heat of evaporation?

A

575 btu/lbs

21
Q

Why is R717 such a good refrigerant?

A

Because of its
ability to absorb heat while passing through an
evaporator of a refrigeration system. Has no Global Warming Potential or Ozone
Depletion Potential.

22
Q

What level of toxicity and flammability is R717?

A

B2, it is toxic and has some flame propagation

23
Q

Would you need a bigger compressor for R717 in comparison to R404a?

A

Yes, the specific volume is much larger than R404a

24
Q

What happens in low alarm. (25ppm, lower than 35ppm)?

A
  • Initiates MUA and Exhaust Fan.
    • Will create a local alarm strobe/siren
    • Will not dial out to monitoring or emergency services to allow minor problems to be repaired
25
Q

What happens mid level (50ppm)?

A
  • MUA/Exhaust continue to operate
  • Local alarm strobe/siren continue to operate
  • Monitoring company notified
26
Q

What happens at high level alarm (200ppm)?

A
  • MUA/Exhaust continue to operate
  • Local alarm strobe/siren continue to operate
  • Monitoring company notified
  • Emergency Services notified
27
Q

Where is the alarm sensor located?

A

Sensor location 10 ft above finished floor or 10-30 cm from ceiling

28
Q

How many air changes need to happen in the mechanical room?

A

15 air changes per hour

29
Q

How many pounds of water to one pound of ammonia in a deluge tank?

A

8lbs of water to 1lb of ammonia

30
Q

What is different about the TX valve in DX ammonia system?

A

Has a 2 stage pressure drop to reduce wear from flashing

31
Q

Why does the DX coil have to be large in ammonia?

A

To be able to superheat the refrigerant leaving the evaporator

32
Q

How far does the relief pipe need to be pipe according to B52?

A

15ft above the roof or 25ft away from the building or windows

33
Q

How high does the emergency valve/fire box need to be installed B52?

A

No less than 7ft

34
Q

What’s the most popular method of freezing?

A

Air blast freezing

35
Q

How is most industrial compressors, evaporators, and condensers piped?

A

In parallel

36
Q

What is a multi stage or compound system?

A

Refrigerant flows in series through 2 or more compressors. Suction of the high side is discharge of low stage.

37
Q

What temp do you use a compound system?

A

-10C 15F

38
Q

How is de-superheating accomplished?

A

Using an inter cooler between compressors

39
Q

What are the 2 types for feeding the evaporator?

A

Gravity flooded and liquid over feed

40
Q

How is liquid feed different from gravity flooded?

A

You need a pump and a low pressure receiver

Refrig. Theory (2 decks)

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