Ammonia Exam Questions

Question 1

Primary refrigerants change state and have a ________ heat process

Answer 1

latent

Question 2

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

Answer 2

sensible

Question 3

Secondary refrigerants usually have _____ as a base

Answer 3

water

Question 4

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

1. 2.
   3.

Answer 4

1. brines (calcium chloride or sodium chloride)
2. glycol (methylene, ethylene, propylene)
3. Alcohol (ethyl, methyl)

Question 5

Name a few main categories of secondary refrigerants;
1.
2.
3.
4.
5.
6.

Answer 5

1. brines
2. salt and water
3. glycols
4. water
5. refrigerants
6. alcohols and water

Question 6

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

Answer 6

solidifies

Question 7

sodium ________ is added to keep brine slightly alkaline

Answer 7

hydroxide

Question 8

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

Answer 8

-6F

Question 9

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

Answer 9

PH

Question 10

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

Answer 10

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

Question 11

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

Answer 11

salt

Question 12

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

Answer 12

leakage

Question 13

Which type of brine would corrosion inhibitors be used

Answer 13

alcohol type

Question 14

*What type of glycol is used in food processing?

Answer 14

propylene glycol

Question 15

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

Answer 15

Eutectic mixture

Question 16

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

Answer 16

eutectic

Question 17

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

Answer 17

increases, crystals

Question 18

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

Answer 18

1. calcium chloride

2. sodium chloride

Question 19

With what tool do you determine a solution mixture?

Answer 19

hydrometer

Question 20

What does a hydrometer measure?

Answer 20

specific gravity

Question 21

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

Answer 21

calcium chloride: 1.2 @ 60F

sodium chloride: 1.17 to 1.2 @60F

Question 22

___ is extremely harmful in a brine system

Answer 22

air

Question 23

what does air in a brine system promote?

Answer 23

corrosion

Question 24

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

Answer 24

cavitation

Question 25

Hydrometers may be used to measure;

Answer 25

battery acid, glycol solutions, salt brines, alcohol

Question 26

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

Answer 26

1.0 - 2.0 eutectic solutions, battery acids, glycol

Question 27

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

Answer 27

0.7-1.0 water impurities, alcohol

Question 28

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

Answer 28

header purge valve

Question 29

What are some common methods of dehumidification?

Answer 29

refrigeration, desiccants, or air

Question 30

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

Answer 30

You can use a diverter valve

Question 31

Name the two ways multi stage compression can be accomplished;

Answer 31

direct staging and cascade staging

Question 32

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

Answer 32

1. compressor | 2. high

Question 33

What is the practical temp limit in direct staging systems?

Answer 33

-125F

Question 34

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

Answer 34

intercoolers

Question 35

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

Answer 35

two, boiling

Question 36

Cascade systems are normally used in ultra ____ temperature applications

Answer 36

low

Question 37

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

Answer 37

receivers

Question 38

Why are intercoolers used?

Answer 38

avoid overheating the higher stage compressor from excessive discharge temperatures

Question 39

name three types of intercoolers; 1. open ____ type intercooler 2. closed shell and ____ type intercooler 3. the dry ________ type intercooler

Answer 39

1. open flash 2. closed shell and coil 3. the dry expansion type

Question 40

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

Answer 40

flashing

Question 41

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;

Answer 41

1. bubble | 2. simple operation, low cost, good liquid temp reduction

Question 42

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

Answer 42

refrigerants

Question 43

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

Answer 43

evaporation

Question 44

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

Answer 44

entering wet bulb

Question 45

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

Answer 45

78F

Question 46

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

Answer 46

leaving, wet bulb

Question 47

What is drift in cooling towers?

Answer 47

water that gets entrained in airflow and discharged to the atmosphere

Question 48

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

Answer 48

airflow

Question 49

*___ is the most commonly used material for fill

Answer 49

PVC

Question 50

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

Answer 50

wood

Question 51

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

Answer 51

evaporation