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Term 2: Ammonia > Ammonia Exam Questions > Flashcards

Ammonia Exam Questions Flashcards

1
Q

Primary refrigerants change state and have a ________ heat process

A

latent

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2
Q

Secondary refrigerants do NOT change state, _______ heat gain or loss only

A

sensible

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3
Q

Secondary refrigerants usually have _____ as a base

A

water

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4
Q

Some of the substances used to make secondary refrigerants when mixed with water are;

  1. 2.
    3.
A
  1. brines (calcium chloride or sodium chloride)
  2. glycol (methylene, ethylene, propylene)
  3. Alcohol (ethyl, methyl)
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5
Q 
Name a few main categories of secondary refrigerants;
1.
2.
3.
4.
5.
6.
A
  1. brines
  2. salt and water
  3. glycols
  4. water
  5. refrigerants
  6. alcohols and water
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6
Q

A eutectic system is a mixture of chemical compounds or elements that has a single chemical composition that __________ at a lower temp than any other composition

A

solidifies

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7
Q

sodium ________ is added to keep brine slightly alkaline

A

hydroxide

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8
Q

Sodium chloride brine is cheaper than calcium chloride brine but cannot be used below its eutectic point of __F

A

-6F

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9
Q

The corrosiveness of a brine is determined by using a __ tester

A

PH

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10
Q

PH levels run 1-14. What numbers are considered neutral, more alkaline, more acidic?

A

Ph level 7 is neutral
below 7 is more acidic
above 7 is more alkaline

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11
Q

*The PH levels of ____ brines should be between 7 and 8.5

A

salt

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12
Q

Systems using aqueous solutions of alcohol or glycol are more susceptible to ________ than those using salts

A

leakage

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13
Q

Which type of brine would corrosion inhibitors be used

A

alcohol type

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14
Q

*What type of glycol is used in food processing?

A

propylene glycol

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15
Q
  1. A solution of any salt in water has a specific concentration at which the freezing point is at its minimum thus it is called a _______ mixture
A

Eutectic mixture

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16
Q

The temperature at which the brine freezes is called the ________ temperature

A

eutectic

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17
Q

Eutectic mixture ratios must be followed. Too much glycol results in gel forming and the freezing point of the remaining solution _________. Too little glycol results in ice ________ forming and damage to system components

A

increases, crystals

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18
Q

Name 2 typical brine types for food freezing/meat packing applications;

A
  1. calcium chloride

2. sodium chloride

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19
Q

With what tool do you determine a solution mixture?

A

hydrometer

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20
Q

What does a hydrometer measure?

A

specific gravity

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21
Q

Recommended specific gravity’s for calcium chloride and sodium chloride?

A

calcium chloride: 1.2 @ 60F

sodium chloride: 1.17 to 1.2 @60F

22
Q

___ is extremely harmful in a brine system

A

air

23
Q

what does air in a brine system promote?

A

corrosion

24
Q

Air also causes ________ in the brine pumps, and can displace the brine to the extent that the brine will overflow down the drain

A

cavitation

25
Q

Hydrometers may be used to measure;

A

battery acid, glycol solutions, salt brines, alcohol

26
Q

A heavy liquid read by a hydrometer is in what range? name two examples

A

1.0 - 2.0

eutectic solutions, battery acids, glycol

27
Q

A light liquid read by a hydrometer is in what range?

name two examples

A

0.7-1.0

water impurities, alcohol

28
Q

Best way to get air out is to shut the brine pump off and let the air rise to the top of the header, and release it at the ______ _____ valve

A

header purge valve

29
Q

What are some common methods of dehumidification?

A

refrigeration, desiccants, or air

30
Q

How would you control the temp of water coming into a cooling tower on a low ambient day?

A

You can use a diverter valve

31
Q

Name the two ways multi stage compression can be accomplished;

A

direct staging and cascade staging

32
Q
  1. Direct staged systems use one refrigerant and one circuit with more than one ________
  2. This method is used on systems that have _____ compression ratios
A
  1. compressor

2. high

33
Q

What is the practical temp limit in direct staging systems?

A

-125F

34
Q

________ are required to cool discharge gas from first stage compression before entering second stage

A

intercoolers

35
Q

Cascade systems use ___ or more refrigerant circuits each using refrigerants with progressively lower ________ points

A

two, boiling

36
Q

Cascade systems are normally used in ultra ____ temperature applications

A

low

37
Q

_______ are not normally used in cascade systems because they are critically charged

A

receivers

38
Q

Why are intercoolers used?

A

avoid overheating the higher stage compressor from excessive discharge temperatures

39
Q

name three types of intercoolers;

  1. open ____ type intercooler
  2. closed shell and ____ type intercooler
  3. the dry ________ type intercooler
A
  1. open flash
  2. closed shell and coil
  3. the dry expansion type
40
Q

In open type intercoolers the liquid from the condenser is expanded in the intercooler and its temperature is reduced by ______ down to intermediate temperature

A

flashing

41
Q
  1. In open type intercoolers the discharge gas is de superheated by causing it to ______ up through the liquid and the sub cooler
  2. name two advantages to open type intercoolers;
A
  1. bubble

2. simple operation, low cost, good liquid temp reduction

42
Q

Cooling towers are heat rejectors. They do not condense _______ so they are not considered condensers

A

refrigerants

43
Q

Entering wet bulb temperature is the lowest temperature that water can theoretically reach by ________

A

evaporation

44
Q

_________ ___ ____ temperature is the most important parameter in tower selection

A

entering wet bulb

45
Q

For most areas in North America, an entering wet bulb temp of ___F is common.

A

78F

46
Q

Approach is the difference between water _____ the tower and the entering ____ ____ temp of the air

A

leaving, wet bulb

47
Q

What is drift in cooling towers?

A

water that gets entrained in airflow and discharged to the atmosphere

48
Q

*Cooling tower fill helps the water gain maximum exposure to ______

A

airflow

49
Q

*___ is the most commonly used material for fill

A

PVC

50
Q

*Current designs for HVAC tend not to use _____ for fill

A

wood

51
Q

*The addition of fill surface to the traditional evaporative condenser design reduces __________ in the coil section, reducing the potential for scaling and fouling.

A

evaporation

Term 2: Ammonia (21 decks)

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