Cooling Tower Section 1 API

COOLING TOWERS

SECTION 1 OPERATION AND CONSTRUCTION

'There aTe exhibits placed in the center of Ihe book that will be referred to later in the program. The1J should be removed and set aside now so Ihal they will be handy when needed.

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1. A refinery uses as much as 25 barrels of water for every barrel of crude processed.

A 200,OOO·bal'l'ei-a-day refinery might _ _ _ _ _ _ _ barrels of water.

use as much as 5,000,000

. 2. Of all the water used by a refinery, 80 to 90 % is used as coolant to absorb energy.

heat

3. Look at tn15 heat exchanger.

HOT

COOL

~-LIQUID

As the liquid travels through the pipe, the heat from the liquid is exchanged or transferred to the _ _ __ __ _

water

4. Heat always travels from areas of higher te'm perature to ·areas of (higher / lower) temperature.

lower

5(, Water can absorb only so much heat. As water becomes hotter, its effectiveness as a coolant (increases / d ocreases).

6. After a while, the temperature of that it can no longer absorb • liquid .

t~e

water becomes so hillh from the hot

decreases

heat

7. The water in this heat exchanger works as a coolant only as than the liquid being cooled. long as it is

cooler

8. Maximum cooling IS achieved by constantly replacing hot water with _ _ _ _ _ _ _ water.

coo1

1

9. In order to provide for further cooling, two things are possible.

First, the hot cooling water can be discharged and _ _ _ __ with fresh water.

replacE'(t

10. Or, the hot cooling water can he _______ and reused

cooled

(or further cooling. 11. The amount oC water needed for cooling in a large refinery is

in the range of (tho.usands/millions) of barrels per day.

millions

12. Drawing millions of barrels o( water per day from the water

supply would be extremely _ _ _ _ _ __

co~tly,

13. The amount of water needed is so large that many water supplies (would /would not) be able to provide enough.

or expE'nsive

would not

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14. A refinery must be careful about the quality of the water it discharges. Discharging millions of barrels of hot water per day might cause a problem.

pollution

15. Cooling the hot water enables the refinery to _ _ _ _ __ water over and over again.

reuse

16. The liest way to handle hot water is to (discharge it / cool and reuse it).

cool and reuse it

17. Hot water is cooled for reuse in special cooling _ _ .. _ __

tower!:::

MmlODS OF HEAT TRANSFER

18. Suppose a steel rod is heated at one end.

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(The entire rod heats up evenly./Section A gets hot first.) 19. AJ3 s~tion A becomes hot, it acquires thermal, or _ _ _ __

Section A gets hot first. heat

energy. 20. Thermal, or heat, energy always travels from higher to _ _ _ _ _ _ _ temperature regions.

2

lower

21. As one seetion of the steel rod beeomes hot, the rod (cond ucts/ does not conduct) the heat to the colder sections.

conducts

22. In this example, the heat transfer from section A to C (occurs/ does not occur) by conduction.

occurs

23. Conduction occurs when heat or thermal energy flows through a substance from a _ _ _ _ _ to a _ _ _ __ temperature region.

higher; lower

24"Suppose a hot baT of steel is placed in contact with a cold one.

COLO BAR HOT BAR

B

POINT OF CONTACT A

will transfer

The. heat energy from baT A (will transfer/will not transfer) to baT B. 25. The cold bar becomes hot first at the point of _ _ _ __ _

contact

26. Then, the heat is transferred through the bar by _ _ _ __

conduction

27. Another method of heat transfer is convection.

WATER

rn---BURNER

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The burner heats the water in the vessel (all at once/at the bottom only).

at the bottom only

28. As the water at the bottom of the container gets hot, it becomes less dense.

.

A volume of hot water weighs (more/ less) than the same

less

volume of cold water.

29. As the water at the bottom of the vessel gets hot, it will (float to the top / stay at the bottom).

fioat to the top

30. In this case, heat is carried to other parts of the vessel by (conduction / physical movement).

3

physical movement

31. Convection is the transfer of thermal or heat energy by actual ______________ within a 5ubstance.

physical movement

32. Heat transfer also occurs in another way.

If you bring your hand near any hot object you (feel / do not feel) the heat from it.

feel

33. Usually, solids, liquids or gases have a high enough temperature to emit OT· radiate energy.

hent, or thennal

34. This method of heat transfer or flow is called (convection / radiation).

radiati on

,

.

.

Review

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35. There are three methods of heat transfer: rad iation, conduction, and _ _ _ _ _ __

convection

36. Heat flowing within a substa:lce from a higher temperature region to a lower temperature region is heing transferred by conduc tion

37. This shows a flame heating the bottom opening of , duct. ~:

COLD AIR

Ai;

it enters, the, cold air absorbs thermal energy and

becom~

hot 88. As the air becomes hot, it rises and leaves th e duct, taking its _______ energy with it.

heat, or thennal

,

39. The method of heat traMler by physical movement is calleu convection •

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HOW COOLING TOWERS COOL WATER

Result, "f Evaporation

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;-. 40. Sorr.~ Conn of energy is required for any movement or change

in matter. To boil water) a source of _ _ _ _ _ _ _ energy is needed.

heat

41. The molecules in any body of water move due to the heat _ _ _ _ ___ in them.

energy •

42. The speed of the molecules depends upon the amount of heat energy in them. The more heat, the the

faster

molecules move.

43. In any body of wat er, some molecules move faster than others. /

more

The molecules which move faster have (more / less) heat energy. 44. Some molecules moYe fast enough to break away from the body of water and mix with the air.

The molecules that break away first have a (higher/lower)

higher

amount of heat energy.

45. As the molec ules leave the body of water, they take their _______ energy with them.

/

heat

46. The ",olecules that remain have a lower level of heat energy. With a lower level of energy, these molecules move (slower.' faster).

slower

47. In order for them to escape from the body of water, the slowmoving molecules have to in speed.

increase

48. Adding heat energy to the molecules will cause them to move faster

,,

?nce moving fast enough, the molecules will es;ap:. ·;hi;) IS evaporahon. . _" . ' ._- . _ - After partial evaporation, a bod y of water (is cooler/ stays the same) .

is cooler

5O' I,;Cooling towers are designed to expose hot water to the air.

allows

This (allows/ does not allow) partial evaporation of the water. 51. This partial evaporation (cools/ does not cool) the water.

cools •

What Affects Evaporation

52. In order for water to evaporate, it (needs/ does not need ) to be in contact with air.

needs

53. The 'larger the surface in contact wi th air, the (more/1ess) molecules can leave a body of water at a given time.

more

5

54. The more water molecules that leave a body or water at a given time, the (faster / slowe,') the rate of evaporation.

faster

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55. These two basins contain the same amount of \vater.

8

A

The rate of evapOl'ation is faster from basin (A / B).

B

56. The faste,' the rate of evaporation from a body of water, the (fasteri slower) the body of water will cool.

faster

57. Cooling towe''S are designed to provide the hot water with a _ _ _ _ _ __ surlaceato-air contact.

large

58. The hotter the water, the more (fast / slow) -moving molecul.s in it.

fast

59. Hot water will evaporate _______ than cold lVater.

faster

60. Atmospheric pressure (exerts / does not exert) pressure on a body of water.

exerts

I 61, Atmospheric pressure (resists / does not resist ) the molecules escaping from a body of water.

resist!'

62. It is easier for water molecules to leave a body of water at (high / low) atmospheric pressures.

low

63. As air acquires moisture (water molecules), its humidity rises, or increases

64. Air can hold only a certain amount of water molecules. If it becomes water saturated, it will no longer _ _ _ _ _ __ water molecules.

/ 65. The higher the humidity of th e air in contact with the water, the

the rate or evaporation.

Review

slower

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66. Hot water evaporates at a (higher/ lower) rate than cold water.

·t· . : ,: :~" : '

higher

/ 67. Which of the following affect the rate of water evaporation: a) humidity of the air b) surface of contact betwe~n water and air c) the temperature of the water 6

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CONSTRUCTION OF COOLING TOWERS

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68. In the early days of continuous processing, no attempt was made to cool process water. Water that was cool already was taken into the plant from the outside, then discarded when hot.

.'

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/' When a plant was located near a river or stream, the cool water

.'

was taken into the plant upstream and released _ _ _ __

downstriam

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" 69. When a plant was not located near a river, the water was taken from a pond. Hot process water was returned to the pond surface and cooled by surface exposure to the ______.

,. air,

or ·itmosphere

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70. The open pond cooling system was eventually modified.

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HEAT EXCHANGER

. "

COOL WATER

'. SPRAY POND COO LING SYSTEM

. '

In this system, hot cooling water is _______ over the

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sprayed

pond surface.

71. By spraying the hot water, more water-to- _____ __ surface contact is reached.

air

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72. With a larger water-te-air surface contact. the rate of evaporation (increases / decreases).

Increases

~'73. However, wind could blow away the sprayed water, resulting

in water

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and damage to nearqy structures. ", .

74. The spray pond . ystem was also modified.

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FENCE

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To reduce water loss due to drift, and to prevent property damage. this system includes _ _ _ _ __ around the pond. 7

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75. The air contacting both of these ponds is at the same humidity level. NO WINO

"'U!~luAIR

WINO

B As evaporatio~ occurs, the air in conlact wilh the water becomes (morelless) saturated.

76. As the ail' becomes

mOTe

more

saturated, the rate of evaporation decreases

77. The air over pond B never becomes saturated because it is constantly being with new air.

replaced

78. The rate of evaporation is mnre constant in pond (A/ B).

B

79. The rate of evaporation in the open pond, t he spray pond, and the spray type cooler is greatly affected by the prevailing

wind 80. The rate of evaporation is also aflected by the . _ _ _ _ __ of the air.

humidity

Atmospheric Cooling Towers 81. Exhibit 1 shows an atmosphen'c cooling tower . This cooling tower, like a pond system, depends on the

_-:-_.,-_ __ velocity and the relative _ _ __ _ __ of the air.

wind; humi'dity

82. Some of the wind entering the tower is carried upward, but most of the wind blows straight the tower.

through

83. The wind flow through the tower is interrupted and changed by the and bars.

louvers ; splash

84. The louvers help direct wind and also prevent water loss

/

85. The hot air and water vapors leaving the top of the tow .... have to pass through the .

drift eliminators

86. Some atmospheric cooling towers have adjustable sections of

_______ and drift control of air flow.

to aid in the

87!':The splash bars slow down the raU of water and break it up into small _______. 8

.... "

louvers; eliminators'. . . " .' ".

drops

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Cooling ,

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EXHIBIT BOOKLEY:: .

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EXHIBIT 1

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ATMOSPHERIC COOLING TOVIER

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___?HOT AIR ANO WATER VAPO

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., FROM HO ' WATER

WATER SPRAY

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LASH ARS

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liND (AIR)

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! LOUVERS

---11rb~~~~~~.-

MAKE WATE

:OLUMN

COOLED

WOTl:"

BASIN

COOL WATER

, solute

humidity readings tell how much water is in a given quantity of air, but (do/ do not) tell how much more water . the air can absorb. 16

do not

. order tc... know how much evaporation can take place, it is _sary to know how much more the air absorb.

water .

ipposewe have a humidity reading that says air at 85 0 holds of the maximum it could hold at that temperature.

~~\~~~I;'~S expressed as (degree of saturation/ weight per humidity reading is given

~

a

"p~rcentage

degree of saturatio_n

of maximwn

Humidity "erprE:S.Sed as a fJf:'T~ntage Cot maximum humidity at a given tan~tU!e is (rtlative / e;bso\utE: / humidity.

relative

206. A reIati..-~ humidity reading (doc do.,; not) give an indica· tion of how much more wa"ter air can absorb.

doos

207. If air bolds all the water vapor it can hold at any temperature, it is aaid to be _ _ _ _ __ .208. The relative humidity of air at the point of sat uration

saturated

lS

-----0/0.

100

209. AJ. relative humidity increases, evaporation _ _ _ _ __ 210.

decreases

Th~\.performance of a cooling tower (increases/ decreases) as the relative humidity increases.

decreases

211. Relative humidity is the (least/ most) important variable af·

most

fecting the performance of cooling towers.

Dry.and Wet-Bulb Temperatures 212. This combination of thermometers and wick is a hygrometer.

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THERMOMETER

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The thermometers are identical except that one bulb is covered bya _ _ _ _ __ 17

wick

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:213. Beeause the wick is saturated with water, the thermometer it covers is called a ·bulb thermometer.

wet

214. Evaporation has a cooling effect. I If the water in the wick of the wet-bulb thermometer is

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evaporating, it wiJI show a (warmer/cooler) temperature than the other thermometer. .

215. The faster evaporation occurs, the (greater/ less) difference ! there will be in flte readings. 216. Evaporation will occur faster If the air surrounding the wick is (moisUdry).

cooler

greater

dry

217. In dry air, the wet-bulb reading is always (lower/ higher) than the dry-bulb reading.

lower

218. Suppose the dry bulb reads 90°F and the wet bulb reads 75°F.

100' 90% 80 %

/b

90 0:

w 80 fw

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70

::E

a: W :x: f-

ro --' => ro

60

f-

50

w

;0:

40

~v:: ;:::::

~V

60~~

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50'/.·

0

40 ' " 30 '~

20'1

10 0 •

":nm ,:.... < m I C

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>2 -<

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V

:/' 50

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/. ~ f0 ~ :& ~ ./' V; t%= / / V 0 ~ V /. Vy V V ~ ~ V/ ,,:% ~ ~ V V / ' V ~ t:% V V . /V ./ ~ / V ./

70 ~'

60

70

80

90

100

DRY BULB TEMPERATURE

The chart shows that the relative humidity is _ _ _ _ _ %.

50

ZI9. If the dry bulb reads 60°F and the wet bulb reads GO°F, the relative humidity is %.

100

l20. The greater the difference between readings, the (higher I lower) tbe relative humidity.

lower

18

, . A sling psychrometer also measures relative humidity.

GAUZE WICK

.. . .. . ...... . .... _- . DRY BULB

The operator whirls the sling psychrometer

In

the outside

atmosphere after saturating the wick with _____---'_

water

22. If the atmosphere is not saturated , there will be _ __ _ _

different

readings on the two thermometers.

:23. When the wet bulb reads lower than the dry bulb, it is because water has from the wick.

evaporated

124. Evaporation causes _____ __

cooling

!25. Cooling tower performance is (highest/ lowest) when wet- 'and , .. dry-bulb temperatures are equal.

lowest

~6.

Even when the air is saturated in the tower, some cooling occurs by convection and conduction. Therefore, cooling t owers do not depend entirely on _ _ _ _ _ __ to accomplish cooling.

evaporation

1Zl. When the outside air is cooler than the water being cooled, conveetion conduction

some cooling occurs due to radiation, and _______ , even though none occurs due to evaporation.

228. ")ve'\thoullh no evaporation occurs, if the air is cooler than the '.

, water; heat

IS

transferred from the water to the

.

229. The heated air then carries the heat with it out of the tower by _ __ _ _

convection

230. Cooling towers are never 100 % efficient. If the wet-bulb temperature is 65°F, that would be the minimum a.pproach temperature of the water. The lowest possible water temperature after cooling with the

above condition would be (60'F/above 65'F).

• above 65'F

23I. The efficiency of cooling t owers, regardless of type, increases as the difference between wet-bulb and dry-bulb temperature increases

19

Winter Operation 232. The degree or cooling in"cooling towers in part depends on the

amount of air flowing through the _ _ _ _ _ __

tower

233. In addition, il the air is hot and humid, the degree 01 cooling is (more/less) than when the air is cold and dry.

less

234. Low air temperature may result in too much _ __ _ _ __

cooling

235. Water freezes at 3Z0F. In winter, air temperatw"e well below 32°F may cause cooling water to on parts of the cooling tower.

freeze

236. Because of more cold air contact, water broken up into small droplets freezes (faster/slower) than if it was in a solid stream.

laster

237. Ice (onnations may

block

_~_

_ _ _ _ the passages between

splash bars. 238. The operator has to watch (or fannation of ice around the fan.

I! ice builds up around the Ian too much, it may shut off the How 01 _ _ _ _ __ 239. In cold weather, moisture-filled air is likely to form _ _ _ _-,

Ice

on the fan blades and other moving parts.

240. This may cause overloading 01 the fan motor and costly ~:

damage, or repairs

24.1. The operator"needs to know how to prevent _ __ _ _ __ . formation in the tower and on moving parts.

ice

242. One way to control freezing is to limit the quantity of cold _ _ _ _ _ _ _ entering the tower.

alf

243. In atmospheric towers, adjustable louvers can limit the intake

01 _ _ _ __

...

244. To limit the intake of air in induced-and forced-draft towers, the

fans

can be slowed or shut down .

245. Decreasing the pitch of the Ian blades will also reduce the _ _ _ _ _ _ intake. 246. If ice has formed in the fill deck, it can be melted by reducing the amount of cold

entering the tower.

•

air

247. The incoming water will melt the ice because the water is hot, or warm .~ ,

248. Fans which do not have variable-pitch blades are usually equipped so that the direction of rotation can be _ _ _ __ Now tum the page, turn the boo&t over, and go on .

changed. or reversed

20

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249. On a forced-draft towel', the fan pushes the aIr into the (top !bottom) of the tower.

bottom

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:250. R',d'sing the pitch of the fan blades causes air to be (pushed .;:: into /;ucked out of) the tower. .

sucked out of ,,'

::t-.'",,'

can

251. Since the ail' in the tower is hot, reversing the fan (can/cannot)

melt an ice buildup. 1.:252. The quantity of ail' flowing through the forced- or induceddraft towel' can be controlled:

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by shutting off one or more _ _ _ _ _ __ ;

fans

by changing the pitch 01' direction of rotation of _____ _ _ _ _ _ _ ;and

fan blades

by changing the _______ of fan motors.

speed

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253. Cooling towers are needed in modern refineries to reduce the temperature of cooling water. Cooling water needs cooling so that it can again be used in exchangers to:

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condense petroleum _ _ _ __ __

vapors

cool products enough so that they do not go off _ _ _ __ in storage due to heat; and to products to

specification cool

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pressure- or fire-safe storage temperature.

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254. Cooling towers depend mostly on the (conduction of heat

,;

partial evaporation of watt

from water to air/ partial evaporation of water).

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255. Evaporation depends on water-to- _ _ _ _ _ _ _ contact.

air

256. The most important condition affecting the rate of evaporation: is the (temperature / relative humidity) of the air.

relative humidity

. . 257. Atmospheric cooli ng towers depend primarily upon the pre-

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draft

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259. In fo""ed- and induced-draft cooling towers, the draft is .~l. caused by motor-driven _ _ _ _ _ __

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260. The draft in forced- and induced-draft cooling towers is (eaaier/harder) to control than the draft in atmospheric \~:; towers:

.

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The natural-draft tower is designed in such a manner that the heat of hot water causes a through it.

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wind

for performance.

fans

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261. Redwood and fir is used in the construction of cooling towers because it resists wet _ _ _ _ _ __

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rot

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262. Ideally, metal parts of the towers should be highly _ __ to con-osian .

reslstan ~

263. Metal parts are coated with special _ _ _____ to in· crease their corrosion resistance.

coating, or paint

264. The operator should keep alert to evidence 01 excessIve _ _ _ _ _ _ and wet _ _ _ _ __

corrosion. or rust: rot

265. Cooling towers perlorm best when the air passing through them- is cool .and (dry j wet).

dry

266. Hygrometers and psychrometers .are instruments used in

determining the _-,-_ _ _ _ _ _ _ _ 01 the air.

relative humidit}'«'

267. If there is no difference in the temperature readin g of a dry. and wet~bulb thermometer, the relative humidity is %.

100

268. At 100% relative humidity, there will be (some / no) cooling

no

•

due to evaporation.

269. Even though there might not be any cooling due to evapora· tion, a cooling tower will still cool water slightly due to radiation,

and _ _ _ _ _ __

conduction; convection

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270. In cold climates, where temperatures get belol. Ireezing, the

- operator must guard against the (ormation 01 _ _ _ _ __ in the tower as wen as the fans.

ice

271. A natural·dralt tower (needs / does not need ) drift eliminators. 272. All other towers have _ _ _ _ _ __

does not need

_ _ _ _ _ to

drirt eliminators

reduce loss of water due to wind . 273. Makeup water is needed in cooling towers to replace water

loss aue to leaks,

and _ __ _ _ __

evaporation; drift

SECTION 2

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WATER CONDITIONING PHYSICAL AND CHEMICAL PROPERTIES OF WATER

1. H20 is a chemical symbol (or water. It shows that a water

•

molecule is a compound made up of two atom s of hydrogen

and one atom of _ _ _ _ __ 2. wnen hydrogen and oxygen combine to (orm water, the process is a (chemical/physical) change. 22

oxygen

chemical

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3. The drawings show different changes that water can undergo. E:J

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(

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"'-_ _- - l

ICE (SOLID) BELOW 32' F

WATER (L IQUID) 32'F TO 212'F

STEAM (GAS) ABOVE 212'F

These changes are (chemical/ physical).

physical

4. Whether water is a solid, liquid, or vapor, its molecule$ are . still composed of two a toms and one _ _ _ _ _ _ atom.

hydrogen oxygen

5.~Heating

or cooling water causes it to change state from one form to another.

. Changing ·the state of water is only a

change.

physical

occurs only when atoms or molecules change from one substance into an entirely _ _ _ _ _ __ substance.

different

. 6. A · ehemical change .

: ·7 . .Water does not undergo chemical change easily. Chemically, it is relatively (stable / unstable).

!.

stable

il' , 8:' Water also has . a good heat capacity. That means that it has

i'

.a good capacIty to absorb

.

heat

! 9. BTU stands for British Thermal Unit. It is a measurement of ~~ quantity of energy.

heat

10. Spteiji£ Mal is the number of BTU's required to raise the temperature of 1 pound of any substance 1°F. For water, this

takes 1 BTU.

,.

To raise 2 pounds of water by 1 OF, for example, requires _ _ _ _ _ BTU's.

2

11. Here is a table of specific heat values for different substances.

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Specific Heats

toY;'

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t' b*_

't ....'

Substanee

Air .

i"~ ...::! Alcohol

r '···Aluminum .... ....

Sp. Ht .

Substance

Kerosine Lead Lube Oil

0.24 0.60 0.22 0.091 . 0.093 0.20 0.21 0.032 0.51 0.115

Sp.Ht.

0.50 0.03 0.45 0.033 0.48 0.192 0.055 1.00 '0.42 0.093

Mercury Brass Steam Copper Stone fj>;; ·Earth (dry soil) • cTin ''. , ..: Glass " ; Water Gold ,.J. !ce Wood (avg.) Zinc Iron (steel) ;; " .,". .'( .'Kerosine .. has a specific heat value of _ _ _ _ _ __

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0.50

12. To raise the temperature of 2 pounds of kerosine by 1°F BTU. ",requires

1

13. When any 1iquid or fluid is used as a coolant, it absorbs heat

energy from the material being _ _ _ _ __ _

cooled

14. As a coolant absorbs heat energy, its temperalllre'_ _ _ __

rIses

15. Raising the temperature of 1 gallon of ker osine a certain amount requires (more/ less) heat than raising a gallon of water the same amount.

less

'.

16. A substance with a high specific heat can absorb (more/ less) heat per degree of temperature change than a substance with a low specific heat.

more

17. A substance with a high specific heat should make a (good / poor) coolant.

good

18. Water can'disso1ve m!l.ny things. Water is norrnally a (good /

poor) solvent.

good

19. Many tiny, inso~uble particles, such as grains of sand, rust, and calcium carbonate, become suspended in water.

Water can contain two kinds of solids : (1) dissolved solids and (2) solids.

suspended, or undissolve

Review

20. Water is made up of two _______ _______ atom.

~ to m s

and one

hydrogen oxygen

21. Chemically speaking, water is (stable/ unstable ' .

stable

22. Water makes a good coolant because it has a _ _ _ _ __ specific heat.

high

23. Because of its properties. water can _ __ ._ _ _ and carry various solids.

dissolve

, ,~

24. The two types of solids that can be found _ _ _ _ _ _ and _ _ _ _ _ _ solids.

In

water are

EFFECTS OF TOTAL SOLIDS ON COOLING

dissolved; suspended

•

", 25. The makeup water used in refineries comes from natural sources such as rivers, lakes, and wells.

•

Such waters are likely to contain both and solids even though they may appear perfectly clear.

24

dissolved suspendod

..

26. Because the water circulates many times through pipes, exchangers" rooling towers, and basins, it picks up (more/ less) solids.

"

•

more

27. ,The total solids increase because the water _ _ _ _ _ __ a little bit of the substances it contacts. ;;~ . '

dissolves

,i8'.'When water evaporates, it (takes/does not take) the solids : , ~: with it.

does not take ,"

,,'

. "i·

" .' 29. Mter partial evaporation,

,"

,

; ~R'

"

the solids tend t o concentrate in 'v-"l'the remaining water. Ccx.>led water leaving a cooling tower },~! has (mOl'e:1ess) total sohds per gallon than the hot water , i . entering the tower. -.\~t . ' .. I.. '

more

H {

.

."

80. The circulating water in a cooling system has (more/less)

more

~11ir.~ 't otal solids than the fresh makeup water. . ·ji}:!.

•

:' slf, So, the discarding of some cooling water and the addition of

~ makeup water tends to keep the total volume of solids

l"!'

.(up/down).

)J

r "

down

'

~' S2., Suspended solids tend to settle out in sections o( the cooling ~~g ': .system where the velocity o( the water is (slowed/increased). C'

1

f 3S.'Some diasolved solids are less soluble in hot water than in cold i;l¥"iiw.ater. When the water becomes hot, these dissolved solids '., . ,Decome solids . .:;.... ~~),' " , . 34. Calcium and magnesium carbonate are less soluble in hot ", ,:: water than in cold water. When cooling water goes through

t!.: heat exchanger, calcium and magnesium carbonate become

0" •

, . . , 'j

solids.

':'1-

:~1:~

i

",.>

~3~,:~,~e~ ~ter containing calcium and magnesium carbonate

!>otled In a vessel, ~(~t bottom of the vessel.

form on the sides and

,_ .'., \8

t-f ~l'f>: , .l-" .... ' .oj. ~:

136.' " The aame thing happens when the water passes through a ~" '.'h e a t . ' J\ ~ ""," .... . . ... .}1 " "

~~

"

,)

~3'i:'Deposits or scales (ormed in the tubing o( heat exchangers '-"

decrease

,will {increase/decrease} heat transfer.

...... r··

D; I '. ~.

>1 :1/

.

exchanger

,:

~ S8. ,The 'buildup of deposits in an exchanger, regardless of the

t .'-. 'cause or source of the deposit, is called fouling. Fouling makes ~ilt(Periodic

necessary.

'

.

¥A~i~oarse, suspended solids also cause wear in narrow passages .. ;or in the flow. This kind of wear is (erosion/ corrosion). ~~' ~ ~:

'

~40.

..

turns

ri.too much buildup of solids is permitted in a cooling tower,

,. . ;. it, too, has to be

periodically.

25

cleaning

::.:! , ••.

erosion'

.~

.~

cleaned

-!

"

"

\

41. Tiny, microscopic plants sometimes thri ve in cooling water

systems. These tiny growths, often green in color, require ligh t in ord er to grow. They start growing on the walls of (closed/open) parts of the system.

open

42. Parts of the growth break away from the walls and start floating in the water. They become part of the _ _ _ _ __

solids.

suspended

.

43. They Cfl,n plug narrow passages in the system and damage woodinthe _ _ _ _ _ _ _ _ _ _ _ __

cooling towers

.

44. These are biological, or living, substances. To control or stop

their growth they have to be _ _ _ _ __ _

killed, or poisoned

45. The biological growths are algae and slime. There are a number of varieties; all cause

to cooling systems.

damage, or fouling

46. Cooling water, in addition to dissolved soli ds and suspended solids, contains some dissolved oxygen and carbon dioxide

which are (solids/ gases).

gases

47. It is not the water in the system that causes corrosion, erosion, and fouling. It is the disSolved _ _ _ _ _ _ , suspended solids, and dissolved _ _ _ _ __

solids gases

KEEPING COOLING WATER IN CONDITION

48. Waters from different water sources are likel y to contain

_______ kinds and quantities of solids and gases.

different, or various

49. The chemical analyses and the physical tests made on the different waters are likely to be _ _ _ __ _ _

different

50. The chemist prescribes what the operator must do to keep the cooling water in good _ _ _ _ __

condition

51. The operator may be required to make a few simple tests and of the water as the t est may indicate. change his

l: eatrnent; "."r eonditi

52. Because each cooling system is different and t he natural make· up water is different, methods of treatment are _ _ _ __

different

CONTROLLING SUSPENDED AND DISSOLVED SOLIDS

,63. If it is necessary (or the operator to make certain tests on cooling water, his supervisor will arrange f or the necessary

instructions and

for the test.

equipment, or tools

. 54'. Chemists use two measures to express the quantity of various f/- . impurities in water: grains per gallon (gr./gal. ) and parts per

: million (PPM). One grain per gallon equals 17 parts per million. If the total solids in cooling water is 10 gr. / gal., the PPM is _ _ _ __

26

170

· : 55: Cooling water analyses usually are reported in PPM. 50 PPM .. . total solids means that in one million pounds of water there · . ; ". are pounds of suspended and dissolved solids.

50

.t

, . .•j ~,

; 56.;rhere are both suspended and dissolved solids in the natural

;;: ~~ ' r: makeup water. These solidc; increase in the cooling tower water ;'(,)r~~ beca~ of ..~ l~:·r chemIcals that are added. , . ,',"',',

evaporation

and because of the treating

.-

., .

'.'

,

.! ...

· . 57. Some small increase of both kinds of solids also comes from "the basins, pipes, and wood in the cooling system . 1

J\. :t

~,~

.

,

.' . ~;;; :rhe total of solids in cooling waters varies from one PPM in :.(.;,j;lt relatively clear water to 50,000 PPM in muddy river water . ..}~"!. Muddy rive,' water probably has (more / less) suspended solids ~.t .:::~ than dissolved solids.

:r: ..

. ..',

.'

more

:':~' .~.~:., .

' ."

.t

.","

',1,' •..;,·,(-

... -".4., •

:'.:

•I.,:.\i.i"

-~. ; .:.~."

sedimentation Ba$in$ " - ' , I' ~

.," '1!