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RACM > REF UNIT 21 > Flashcards

REF UNIT 21 Flashcards

1
Q

(21.2) What is the normal temperature range for high temperature application for refrigeration?

A

47F to 60F

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2
Q

(21.2) What products are commonly stored in high temp refrigeration applications?

A

flowers and candy

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3
Q

(21.2) What is the normal temperature range for medium temperature application for refrigeration?

A

28F to 40F

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4
Q

(21.2) What products are commonly stored in a medium temp refrigeration application?

A

eggs, lettuce, tomato (stuff in a domestic refrigerator really).

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5
Q

(21.2) What is the normal temperature range for low temperature application for refrigeration?

A

below freezing to -20F

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6
Q

(21.2) What products are commonly stored in a low temp refrigeration application.

A

frozen shit.

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7
Q

(21.7) What material evaporators used when cooling acidic products?

A

stainless steel, even though it doesn’t conduct heat as well as copper.

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8
Q

(21.7) Between what 2 states does the best heat exchange occur?

A

2 liquids

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9
Q

(21.7) Define film factor

A

the relationship between the medium giving up heat and the evaporator itself.

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10
Q

(21.8) What are stamped evaporators?

A

an evaporator with a stamped surface, increasing surface area

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11
Q

(21.8) What are the evaporators with fins called?

A

finned-tube evaporators. They are the most common air-refrigerant evaporators today.

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12
Q

(21.8) Why are finned-tube evaporators more prone to frost accumulation?

A

because the fins act as more surface area for the moisture to freeze.

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13
Q

(21.8) Why are multiple circuits used in evaporators?

A

reduces pressure drop

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14
Q

(21.8) What does FPI stand for?

A

fins per inch

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15
Q

(21.9) How is an evaporator’s capacity rated?

A

in BTUs/hr

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16
Q

(21.11) What is a flooded evaporator?

A

evaporators where instead of the end of the evaporator having vapor, it is still liquid. This improves system efficiency.

17
Q

(21.11) What metering device do flooded evaporators usually use?

A

float-type metering device.

18
Q

(21.11) What is a dry-type or direct expansion evaporator?

A

basically what we’ve been learning.

19
Q

(21.13) What is the term for a coil that isn’t receiving enough refrigerant.

A

starved.

20
Q

(21.14) What is hot pulldown?

A

when the refrigerated box temperature gets very high, so the metering device feeds the evaporator more refrigerant.

21
Q

(21.14) What is the term for a coil that is receiving too much refrigerant?

A

flooded

22
Q

(21.18) Where does condensate meant for defrost go once it passes the evaporator?

A

into the accumulator. dense vapors rise out. Without accumulator, it will flood compressor, causingoil foaming, causing bearing washout.

23
Q

(21.18) What is used to prevent wet compression in a compressor?

A

a thermistor at the discharge line.

24
Q

(21.19)

A

EVAPORATOR EFFICIENCY CONTROLLER

RACM (23 decks)

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