muhammad jawhar

1. Cooling Tower
Research Project
Submitted to the department of (Mechanical and Mechatronics) in partial fulfillment of the
requirements for the degree of B.A or BSc. in (Mechanical and Mechatronics)
By:
Muhammad jawhar
Kayfe sayfaddin
Awat yousif
Supervised by:
Dr . sara
May– 2021

2. Table Of Content Page Number
Abstract 4
Chapter 1 introduction 5
background 5
How Cooling Tower
Works?
6
Types of Cooling Tower 7
Psychrometry and Heat
Transfer
9
Cooling Tower
Maintenance
14
Chapter 2 Mechanical
components
16-23
Chapter 3 Thermal
performance
testing
23
General 24
Tower
preparation for
test
24-25
Instrumentation
for test
25
Operating
conditions
during test
28
Conducting the
test
29
Evaluation of
test data
29-34
Chapter 4 Electrical
components
34-42

3. Abstract
In almost every industrial operation, temperature regulation is important. Cooling
towers are essential components of many power plant installations in this regard.
The cooling tower as a heat rejection system works on the concept of extracting
excess thermal energy from hot water and releasing it into the atmosphere using
relatively cold and dry air. A review study is conducted in this study to examine
various types of cooling towers, their application, efficiency, use, and working
principles, which can be useful in the field of nuclear plants and other energy
stations. A variety of studies have been conducted to determine the variations
between the cooling towers and fins that are currently in use.Finally, to explore
the main contours and flow field around the cooling tower, a Fluent simulation
was run.
In cooling towers, deterioration of the packaging material is a big issue. Ceramic
tiles were used as a packaging material in this experiment. The packaging material
is a long-lasting burnt clay that is typically used for roofing. It avoids a common
cooling tower problem caused by corrosion and poor tower water quality. The use
of three different types of ceramic packings is investigated in this analysis, and
their heat and mass transfer coefficients are evaluated. For all three forms of
packaging, a clear comparison of packing behavior is made. resources The
research was carried out in a forced draft cooling tower. The effects of a variety of
variables on tower performance are discussed.

4. Chapter 1
Introduction
A cooling tower is a form of heat exchanger in which air and water are brought
into direct contact in order to lower the temperature of the water. A small amount
of water evaporates as a result, lowering the temperature of the water circulating
through the tower.
Cooling towers are heat rejection devices that use the cooling of a water stream to
pass wasteheat to the atmosphere. Cooling towers are often used in power plants
to cool the flowing water. The cooling towers have been the subject of a variety of
computational and experimental studies. This section contains a list of some
important works. A research project was undertaken to improve the cooling
performance of a natural draft dry cooling tower. The structure was studied using
equations and a computer fluid dynamics technique at varying wind speeds. The
obtained results and consequences confirm that, for wind speeds greater than 4
m/s, the natural draft dry cooling tower's cooling efficiency degrades with
increasing wind speed due to non-uniform ventilation and the vortex within the
tower. It was demonstrated that using an enclosure would improve total cooling
efficiency at all wind speeds tested. (Wang et al. 2017).
Background
The invention of condensers for use with the steam engine gave rise to cooling
towers in the nineteenth century. Condensers condense the steam coming out of
the cylinders or generators by using relatively cold water in a variety of ways. This
lowers back pressure, which lowers steam consumption and thus fuel
consumption, while simultaneously rising power and recycling boiler water. The
condensers, on the other hand, need a large amount of cooling water, without
which they are inefficient. Although water consumption is not a problem for
marine engines, it is a major constraint for many land-based systems.
Several evaporative cooling water recycling methods were in use by the turn of
the century in areas without an existing water source, as well as in urban areas
where municipal water mains might not be sufficient in supply, reliable in times of
demand, or otherwiseadequate to meet cooling needs. The systems took the form
of cooling ponds in areas with available space, and cooling towers in areas with
restricted land, such as cities.

5. These early towers were built on the roofs of buildings or as free-standing
structures, with fans or natural airflow providing ventilation.
One design was defined as follows in a 1911 American engineering textbook: "a
circular or rectangular light plate shell—in essence, a chimney stack that has been
greatly shortened vertically (20 to 40 feet tall) and greatly expanded laterally. The
water from the condenser must be pumped to a series of distributing troughs at
the top of the tower, where it trickles down over "mats" made of wooden slats or
woven wire screens, which fill the space inside the tower."
The Dutch engineers Frederik van Iterson and Gerard Kuypers patented a
hyperboloid cooling tower in 1918. In 1918, near Heerlen, the first hyperboloid
cooling towers wereinstalled. The firstwere installed in 1924 atLister Drivepower
station in Liverpool, England, to cool water used at a coal-fired electrical power
station.
The majority of thermal power plants' power supply is expected to be reduced due
to cooling water use by inland processing and power plants. by 2040–2069.
Figure 01
How Cooling Tower Works?
The hot water enters the tower through the inlet and is pumped up to the header. The header
is made up of nozzles and sprinklers thatspray water and raisethe water's surfacearea. Water
then flows into the PVC filling, which is used to slow down the flow of water. Fans are used at
the top of the cooling tower to raise air from the bottom to the top.
It creates a strong link between air and hot water due to its slow speed and larger water
contact region. The evaporation process lowers the temperature of the water, and the cooled
water is stored at the bottom of the cooling tower, where it is reused in the boiler.

6. Different Parts of Cooling Tower
1. Eliminator: It is not allowed to pass water. Eliminator is placed the at top of tower, from
which only hot air can pass.
2. Spray Nozzles and Header: These parts are used to increasethe rate of evaporation by
increasing surfacearea of water.
3. PVC Falling: Itreduces the falling speed of hot water and it is similar to beehive.
4. Mesh: When the fan is ON, it uses atmosphere air which contains some unwanted dust
particles. Mesh is used to stop these particles and do not allow to enter dustin
to cooling tower.
5. Float Valve: Itis used to maintain level of water.
6. Bleed Valve: Itis used to controlthe concertation of minerals and salt.
7. Body: Body or outer surfaceof cooling tower is often made up from FRP (fiber
reinforced plastic), which protects the internal parts of cooling tower.
Figure 02
Types of Cooling Tower
Cooling towers are divided into two categories.
1) Natural DraughtCooling Tower: Instead of using a fan to circulate air, this type of cooling
tower encloses the heated air in a chimney, creating a pressuredifferentialbetween the
heated air and the ambient air. Air reaches the cooling tower as a result of the pressure
differential. Since it necessitates a massivehyperbolic tower, the capital costis high, but the
operational cost is low due to the lack of an electrical fan. Rectangular timber towers and

7. reinforced concrete hyperbolic towers are the two styles of natural draughtcooling
towers. Figure03
Figure 04
2) 2) Mechanical or Forced Draught Cooling Tower: A fan circulates the air in this form of
cooling tower. When a power plant is operating at full capacity, it necessitates a large amount
of cooling water. It uses a motor with a speed of about 1000 rpm to rotate the fan. The
principle of operation is similar to that of a natural draught cooling tower, with the exception
that a fan is placed on the cooling tower. When a fan is installed on the top of a cooling tower,
it is known as an induced draught cooling tower, and it is most often used for very large
capacity installations that require a large fan capacity. Thus, a forced draught cooling tower
has a horizontal shaft for the fan at the bottom of the tower, while an induced draught cooling
tower does at bottom of the tower and induced draught cooling tower contains vertical shaft
and it is placed at top of the cooling tower.

8. Figure 05
Figure 06
Psychrometry and Heat Transfer
“Evaporation is used to the fullest degree in cooling towers, which are built to expose the
entire transient water surface to the maximum flow of air – for the longest period of time,”
according to an excellent reference manual on cooling. 1 Cooling towers would be enormous
due to vast air flow requirements if cooling was solely based on sensible heat transfer. The
secret to optimizing productivity is evaporation. Evaporation occurs when air travels through a
cooling tower. Water must expend a lot of energy to transform from a liquid to a gas in order
to evaporate. At atmospheric conditions, this is referred to as latent heat of vaporization
around 1,000 Btu/lb. So, even the small percentage of evaporation that occurs in a cooling
tower significantly lowers the temperature of the water returning to the condenser and other
heat exchangers. We will examine this process in more detail below.

9. The definition of "wet bulb" temperature is crucial to comprehending cooling tower heat
transfer. Consider being outside in the shade on a 90-degree day with a 40% relative humidity.
A normal thermometer will normally read 90 degrees Fahrenheit, which is the temperature of
a “dry bulb.” Let's pretend we have another thermometer attached to the dry bulb
thermometer, except this time we've wrapped a soaked piece of cloth around the bulb of the
other thermometer and mounted both on a swivel so that the thermometers can be swirled
through the air quite quickly. Sling psychrometer is the name of this unit, which is a basic and
popular device. The dry bulb thermometer will still work after a while its read 90 F but the
other thermometer will read 71.2 F.2 This latter reading is the wet bulb temperature, and is
the lowest temperature that can be achieved by evaporative cooling.
A cooling tower, no matter how effective, will never chill the recirculating water to the wet
bulb temperature, and costs and space constraints will eventually restrict cooling tower size.
The method is the temperature difference between chilled water and the wet-bulb value.
According to a well-known cooling tower guide, a “standard” sized cooling tower can reach the
wet bulb temperature within 15 degrees Fahrenheit1. As the temperature gets closer, the
curve becomes asymptotic. As a result, the rule of diminishing returns applies to every cooling
tower application at some stage.
The information required to measure heat transfer through air cooling and evaporation has
been compiled in a psychrometric map.
Both psychrometric charts are "very busy" and can be difficult to read at times. The fact that if
two properties of air are known, all of the other properties can be found is a key feature of a
psychrometric map. Take a look at the diagram below, which shows how heat is transferred in
a cooling tower.
Figure 1 shows how the process conditions that could simply and easily exist in a cooling
system. We will calculate the mass flow rate of air needed to cool 150,000 gpm of tower inlet
water to the desired temperature. We will also calculate the water lost by evaporation.

10. Figure 07
The first step is to determine the energy balance around the tower.3
Utilizing algebra, the fact that ma1 = ma2, and that a mass balance on the water flow is m4 =
m3 – (W2 –W1)*ma, where W = humidity ratio; the energy balance equation can be rewritten in
the following form.
From a psychrometric chart and steam table, we find the following.
So, with an inlet cooling water flow rate of 150,000 gpm (1,251,000 lb/min), the calculated air
flow is 1,248,000 lb/min, which, by chance in this case, is close to the cooling water flow rate.
(Obviously, the air flow requirement would change significantly depending upon air

11. temperature, inlet water temperature and flow rate, and other factors, and that is why cooling
towers typically have multiple cells, often including fans that have adjustable speed control.)
The volumetric air flow rate can be found using the psychrometric chart, where inlet air at 68 F
and 50 percent RH has a tabulated specific volume percent of 13.46 ft3/lb. Plugging this value
into the mass flow rate gives a volumetric flow rate of almost 17,000,000 ft3/min.
The amount of water lost to evaporation can be simply calculated by a mass balance of water
only. We have already seen that,
Utilizing the data above, m4 = 146,841 gpm. Thus, the water lost to evaporation is,
A very interesting aspect of this calculation is that only about 2 percent evaporation is
sufficient to provide so much cooling. For those wishing to more quickly evaluate cooling
tower evaporation, a simpler equation is available. The standard formula is
The factor of 1,000 is the approximate latent heat of vaporization (Btu/lb) that was outlined
earlier. To check the general accuracy of this calculation, consider the previous problem we

12. solved in detail. Evaporation was 3,159 gpm with a recirculation rate of 150,000 gpm and a
range of 27 F. This gives a correction factor of 0.78.
The concentration of dissolved and suspended solids in the cooling water rises due to
evaporation. The cycles of concentration are the logical name for this concentration factor (C).
C, or more precisely, permissible C, varies from tower to tower depending on a variety of
factors such as makeup water chemistry and efficiency, heat load, chemical treatment
program efficacy, and potential water discharge restrictions. The ratio of the concentration of
a very soluble ion, such as chloride or magnesium, in the makeup (MU) and recirculating (R)
water can be used to measure concentration cycles. The basic conductivity of the two streams
is frequently compared, particularly when automatic control is used to bleed off recirculating
water when it becomes too concentrated. In systems where chemistry control is simple, a
popular range for C is 4 to 6, as water savings through bleed off, also known as blowdown
(BD), become marginal beyond this range. C will need to be high in arid areas, and “some
[western] states are mandating seven [to even] ten cycles for water conservation.” 4 Of
course, as the number of cycles increases, chemistry control and monitoring become much
more critical and difficult.
Some water escapes the process as fine moisture droplets in the cooling tower fan exhaust, in
addition to blowdown. Drift is the term for this form of water loss (D). Drift is very small in
well-designed buildings, and it can be as low as 0.0005% of the recirculation rate. 5 As
regulations on particulate emissions from cooling towers tighten, minimizing drift particulates
is critical. Losses are the result of leaks in the cooling system (L). Based on flow rates, the
following equations illustrate relationships between evaporation, blowdown, makeup, losses, and
concentration cycles in a cooling tower.
An important development regarding these calculations and many others for cooling towers
comes from the Cooling Technology Institute(CTI, www.cti.org).
Ensuring Good Tower Efficiency
In a cooling tower, close contact between the warm inlet water and the air flowing through
the tower is essential for optimum performance. The invention of film fill is one technological
achievement that has significantly improved heat transfer over the decades, but space
constraints preclude a thorough discussion of tower internals.

13. As the name suggests, the water forms a film on the packing when layers of this film fill
material are put between the inlet water sprays/distributors and the air rising from below.
Most of the surface area of the filming water is exposed to the air. If the water chemistry is
properly controlled and maintained, film fill is very effective. Microbes, especially bacteria,
thrive in enclosed, humid, and moist environments. Bacteria secrete a sticky polysaccharide
coating that traps silt and other debris in cooling water as a defensive mechanism. It's possible
that whole parts of fill will become fully plugged, reducing heat transfer significantly. In
addition, since the deposits add so much weight to the packaging, structuralfailures can occur.
To say the least, cooling tower internals or even whole parts of the tower collapsing is not
pretty. Film fill design has undergone extensive research, and low-fouling configurations are
now available that can be customized based on water quality parameters, especially
suspended solids content. Prior to tower installation, selecting the appropriate fill form is
critical. This does not, however, negate the need for proper chemistry to prevent bacterial
colonization and fungal growth in wood towers, which can lead to rot, and algae blooms on
cooling tower decks and wetted components exposed to sunlight. Good chemistry control is
also imperative to protect fill, condenser tubes, and other components within the cooling
water system from scaling and/or corrosion.6
Cooling Tower Maintenance
For a variety of purposes, cooling towers must be meticulously maintained.
Maintenance of cooling towers: The cooling tower's proper operation is critical to
overall operations. Right maintenance, for example, can help to avoid airborne
diseases. Legionella prevention in cooling towers is critical for the health and
safety of workers and tourists in the building or buildings where the cooling tower
is located. Cooling towers are used in a variety of industries and can be configured
in a variety of ways. As a result, the type of maintenance they need is determined
by the application for which they were designed.
A clogged cooling tower can disrupt the system's operation and put people's
health at risk who work, visit, or live near a cooling tower. The first step in cooling
tower maintenance is to visually check the moving parts and housings and see if
they need to be cleaned. In addition to your cooling tower manufacturer's
instructions, there are five recommended measures to follow to ensure proper
cooling tower maintenance once these areas have been found to require repair
and cleaning or are in working order. These measures are taken care of by the
cooling tower maintenance service..

14. 1. Remove Scale Deposits
Since cooling towers use evaporation, scale deposits accumulate and must be
collected on a regular basis. Minerals in the water cause these deposits, which can
vary in intensity depending on the minerals found in the water you're using.
Limescale, for example, will accumulate and reduce your system's efficiency and
output. It can also lead to the premature degradation of your system if left
unchecked. For best performance, Hamon will help you descale your system a few
times a year.
2. Keep Air Flow Running
Weak fan output is a common cause of system failure. Weak air flow and
inadequate cooling can be caused by loose parts, incorrect fan alignment, and a
lack of gearbox maintenance. Hamon will inspect the cooling tower's basin floor
for sludge build-up, which may be obstructing air flow. We will remove the
pollutants and help you restore sufficient air flow to your cooling tower by using a
tower vacuum. You may also apply a biocide to the cooling tower to prevent algae
and bacterial growth.
3. Keep the Tubes Clean
Mud, slime, algae, and scale can all contaminate chiller tubes. This can cause tubes
to become partially or completely clogged. The frequency at which you must clean
your tubes is determined by the consistency of your water and the rate at which it
accumulates. All units experience build-up, and Hamon can assist you in
determining the best maintenance schedule for your company. The most effective
way to remove debris is to clean tubes on a regular basis. Chiller tubes are an
essential part of cooling tower maintenance.
4. Inspect Your Water Pump
Making the pumping process as effective as possible will help you save money on
your monthly energy bills. Your pump is critical for moving water back and forth,
and keeping it in good working order contributes to a more efficient and effective
operation. Allow a Hamon professional to check your water pump on a regular
basis to extend the life of your machine. The pump, motor bearings, and water
seal can all need to be lubricated as part of the operation. Tests for alignment are
also included.
5. Treat Your Water
Maintaining the efficiency of your cooling tower needs good water quality. Scum
and scale build-up can be caused by poor water quality. To avoid prematuredevice

15. failure, test and handle your water. Water treatment is a worthwhile investment
because it can help the system work at its best. Water treatment is even more
efficient when cooling towers are maintained.
Chapter 2
Mechanical Components
-COLD WATER BASIN:
Figure 08
One of the most critical cooling tower components is the cold water
basin, which collects water and directs it to the sump or pump suction
line.
The aim of a cold water basin is to eliminate stagnant water and
prevent bacteria from growing.
They might even have heaters to keep the water from freezing in the
event of a power outage.
-FILLS:

16. Figure 09
Another important component of cooling tower parts is fill material or fill media. This
component is, in some ways, the most critical since it determines the cooling tower's
efficiency.
The rate of heat transfer between the cooling and working media is increased when the
contact surfacebetween them is greater. In cooling towers, the main purpose of fills is to raise
the contact surface as much as possible.
Fill media can be either of the film style type or splash style type. The film style fills, which is
used in most cooling towers, produce thick water strips that increase the rate of heat transfer
and also larger evaporation rates. splash style fills are commonly used in crossflow cooling
towers in which water cascades down on staggered slats that breaks up water droplets to
increase the water surface area.
-Hot Water Distribution Basin:

17. Figure 10
The (hot water) distribution basin is above the fills, which is where the
hot process water collects. They cannot provide a proper flow
distribution down the nozzles to be sprayed over the fills due to
corrosion and degradation over time, resulting in considerable loss of
thermal efficiency, and as a result, they are replaced to prevent such
downfalls in the system's performance.
-NOZZLES:
Figure 11
The nozzles are one of the cooling tower components that can be used in crossflow cooling
towers. Water is lifted to the distribution basins and then cascaded back over the fill through
the nozzles on the hot water basin floor in crossflow cooling towers.
- Cooling Tower Float Valve:

18. Figure 12
Water within the tower must be kept at the correct level in order for it
to function properly. Float valves, while needing only minor
maintenance over time, have become one of the most important
cooling tower components.
Float valves regulate the water level and, when correctly calibrated,
ensurethat no water is lost when the pump shuts down in an overflow.
- Drift Eliminators:

19. Figure 13
The drift eliminator is another important cooling tower component.
This device's aim is to catch large water droplets in the cooling tower
air stream and reduce process water loss.
The eliminator directs moisture and water droplets away from the
cooling tower and into another part of the system, stopping them from
leaving. After that, the air and water will be separated and recycled for
other purposes.
Apart from the importance of preventing process water loss, the
removal of these large water droplets is motivated by the fact that they
contain chemicals and minerals that are considered harmful to the
environment.
- Water Distribution Piping:

20. Figure 14
Another critical cooling tower component is the water distribution
piping system. Despite the fact that heat generation points are often
located near cooling towers, the piping system routing and physical
dimensions are determined by the type of tower, site configuration,
and topography of the region in which the site is located.
-COOLING TOWER FANS:
Figure 15
A draft is generated by natural draft cooling towers without the use of
any mechanical components. Fans are, however, an important
component of mechanical draft, crossflow, and counterflow cooling
towers.
One of the factors to remember when it comes to fans is noise. Despite
the fact that they are commonly known to be very noisy, some designs
are available with lower noise levels while still being durable.

21. -GEAR BOX:
Figure 16
Towers with large fans for generating a draft often have gearboxes for
changing the power exerted by the motor on the fan's driveshaft.
The gearbox is one of the cooling tower components that reduces the
expense of the mechanical system by not only changing the rotational
speed of the pump but also serving as a torque multiplier, reducing the
size of the motor required.
-Driveshafts:

22. Figure 17
The driveshafts transmit the power produced by the motor to the
gearbox, making it one of the cooling tower's most important
components.
It should be remembered that since the shaft is in direct contact with
the cooling tower's internal environment, highly corrosion-resistant
materials must be used in their manufacture.
In the event of shaft run out, the driveshafts should be able to be easily
recalibrated.
Chapter 3
THERMAL PERFORMNCE TESTING

23. A. GENERAL
The actual performance level of an operating cooling tower can be
accurately determined only by thermally testing the tower. The
accuracy of testing is influenced by many variables, some controllable-
some not. This fact normally precludes testing at the specific design
conditions. However, the limitsestablished by the appropriate ASME
(American Society of Mechanical Engineers) or CTI (CoolingTechnology
Institute) Test Codes provide for testing within a relatively broad
variability range.
The ASME Power Test Code for Atmospheric Water Cooling Equipment
(PTC-23) and the CTIAcceptance Test Code for Water Cooling towers
(ATC-105) provide complete details for towerpreparation,
instrumentation, testing procedures ,and computation of test results.
These codes grantthat procedures may be modified by mutual
agreement whenever necessary to meet any specific contractual
obligation, or to compensate for unusual conditions imposed by a
particular installation.
However, they stress the importance of conductingthe test only during
a period when tower operation and atmospheric conditions are stable.
Obtaining accurate data is the most difficult part of the test. Once the
average test values have beenestablished, the comparison with design
capabilityis relatively easy. Both codes state that the measure of
thermal capability of the cooling tower shallbe the ratio of the test
water circulating rate to thecirculating water rate predicted by the
manufactures performance curves. In addition, the CTI Code provides
an alternative method for evaluating capability, whereby the
"characteristic curve" is used in conjunction with basic theoretical data.
B. TOWER PREPARATION FOR TEST
Prior to the test, the physical condition of the tower must be made to
conform to the following:

24. 1. The water distribution system must be free of foreign materials,
and must be regulated to effect uniformwater distribution in individual
cells as well as between cells on multi-cell towers.
2. Fill and distribution systems must be level and free of foreign
material.
3. Drift eliminators must be clean.
4. Positioning of instruments for obtaining temperature and water
flow measurements must be so established as to reflect the true tower
capability See appropriate Test Code. 5. All test variables should be
adjusted, if possible, to within the limitations imposed by the
applicable Test Code.
C. INSTRUMENTATION FOR TEST (Fig. 142)
Test data required for the performance evaluation of a mechanical
draft cooling tower includes the water flow rate, the hot and cold
water temperatures, the wet-bulb temperature, and the fan
horsepower. The testing of a natural draft tower must also include the
dry-bulb temperature but, ofcourse, omits the need for fan power
data. Make-upand blowdown water quantities and temperatures, as
well as any miscellaneous water sources, may need to be measured,
depending upon their effect upon the aforementioned primary
variables.

25. Figure 18
1. Water flow rate to the cooling tower can be determined by several
means. Most commonly used is the pitot tube traverse method. It is
both practical and accurate, provided laboratory calibration has been
made. Other acceptable means include the orifice plate, venturi tube,
and flow nozzle, all of which also require laboratory calibration. Tracer
methods, as well as acoustic methods, have been developed (usually
dilution techniques) and are being refined. Occasionally, pump curves
are used to approximate the flow. Distribution basin nozzle curves
(gpmvs depth of water over nozzle) are frequently used as a
checkmethod and, in the absence of other methods, may be used to
measure flow directly. The water flow rate is generally the initial test
measurement made, so that any necessary adjustments may be made
before the thermal data is obtained. The constancy of the water rate
during the thermal test run may be checked by observing the pitot tube
center-point reading, circulating pump discharge pressure, or other
acceptable means.
2. Water temperatures should be obtained with calibrated mercury-in-
glass thermometers or resistance-type sensors (RTDS, thermistors,
etc.), either used in direct contact with the flowing water or inserted in
thermometer wells. These instruments must reflect the true average
temperature to and from the tower. The return (hot) water
temperature to the tower is usually well mixed, and a single point of
measurement will normally suffice. However, cold water temperatures
from the tower can vary considerably throughout the collection basin.
Therefore, care must be taken to select a point of measuremen where
thorough mixing has occurred. The pump discharge is generally
considered to be a satisfactory location.
3. Air temperatures include both the wet-bulb and dry-bulb
temperatures. Wet-bulb temperatures should be measured with
mechanically-aspirated psychrometers whenever feasible, although
sling psychrometers are occasionally used and do afford an alternate
and accurate means of mea- suring this variable. (Figs. 19, 20 and 21)
All precautions required by the ASME or CTI Test Codes regarding the
measurement of wet-bulb temperature should be exercised.
Temperature-sensitive elements should, of course, be laboratory-

26. calibrated if a high degree of accuracy is desired. Representative
temperatures obtained if the air flow induced across the thermometer
bulb is approximately 1000 fpm, and distilled water is used to wet the
wick. Generally, the average of three readings taken in rapid succession
(10 seconds apart), after equilibrium is reached, will indicate the true
wet-bulb temperature at any one point. The location of wet-bulb
temperature measurement stations will depend on the contract
guarantee. That is, whether the guarantee basis is ambient or entering
wet-bulb temperature. (Sect. I-E-1) Reference should be made to the
appropriate test code for exact locations of instruments. Any effect on
wet-bulb thermometers from extraneous sources of heat must be
taken into account when data evaluation is made. Dry-bulb
temperatures must also be measured with laboratory-calibrated
instruments at locations called out by the appropriate test code. The
measurement of dry-bulb temperature is confined primarily to natural
draft towers.
4. Brake horsepower refers to the output of the fan prime mover,
which is usually an electric motor. Thermal performance guarantees
are based on aspecific brake horsepower at the design thermal
conditions, which establish a design air density. Fans should be
adjusted prior to a scheduled test so that the horsepower is within 10%
ofthe design value, after corrections to design air density have been
made. Since input electric power is usually measured, the brake or
output power must be computed by multiplying the input power by the
motor efficiency. The efficiency and power factor are obtained from
the motor manufacturer. The preferred instrument for power
determination is a wattmeter. Power may also be obtained with a volt-
ammeter, but power factor as well as efficiency must be applied as
multipliers to determine the brake horsepower. Line losses from the
point of measurement to the fan motor must be considered when the
power is remotely measured.
5. Tower pumping head is the total dynamic head of water at the
centerline of the circulating water inlet to the cooling tower, with
equalized flow to all sections, and referred to the tower basin curb as a
datum. It is the sum of the static pressure at the inlet centerline, the
velocity pressure at that point, and the vertical distance between that
point and the top of the basin curb. The tower pumping head does not
normally include the friction loss in the riser. The static pressure is

27. seldom measured directly at the inlet centerline because of the
unsuitability of this location. It is usually measured at some point in the
tower riser by using either a differential manometer or a calibrated
pressure gauge. Pitot tube tap locations are usually suitable for this
measurement.
The measured static pressure must be converted to the equivalent
pressure at the centerline of inlet. The velocity pressure at inlet
centerline is calculated from the measured water flow rate and the
flow area of the conduit at that point. The vertical distance from the
inlet centerline to the top of the basin curb is obtained by direct
measurement.
D. OPERATING CONDITIONS DURING TEST
Current ASME and CTI Test Codes suggest the following limitations to
variations from design to be observed during testing:
Water Rate ±10% of
design
Cooling
Range
±20% of
design
Heat Load ±20% of
design
Wet-Bulb
Temperatur
e
±10°F of
design
Wet-Bulb
Temperatur
e
+5°F, - 15°F
of design
Dry-Bulb
Temperatur
e
±20°F of
design
Wind
Velocity
generally
less than 10
mph
Fan Power ±10% of
design

28. *CTI Test Code
**ASME Test Code
There will be times when operating or atmospheric conditions will not
permit a test to be performed within the above limits. However, testing
can proceed by mutual agreement among responsible testing parties,
provided test conditions are covered by the manufacturer s
performance curves.
E. CONDUCTING THE TEST
The accuracy of the test depends upon stable operating and
atmospheric conditions. Those conditions which are subject to control
should be closely regulated. For conditions that cannot be controlled
(such as wet-bulb temperatures and wind velocity), tests should be
confined to time periods when minimum variances occur. The duration
of any test period should not be less than one hour after steady-state
conditions have been established.
A test schedule should be established with a CTI Licensed Test Agency,
or other mutually agreed independent third party testing agency. Most
testing is now conducted using electronic data acquisition systems.
F. EVALUATION OF TEST DATA
Arithmetical averages are developed for all temperatures, and water
flow rates as well as fan power are calculated at the conclusion of data
collection. The test analysis of data should follow the ASME or CTI Test
Code methods for evaluation of tower capability. If the manufacturer's
performance curves are not available to the Owner, the following
method will afford a reasonably accurate means of evaluating the
thermal performance of a tower:
For every gpm of water cooled by a tower, the cooling range and the
approach temperature (Fig. 26), relative to a given wet-bulb
temperature, establishes the degree of thermal capability or "Rating
Factor". Rating Factors for various combinations of range and approach
(at indicated wet-bulb temperatures) are shown in figures 143 thru

29. 147. "Capacity Units" are then established as the product of the Rating
Factor and the water rate in accordance with the following formula:
Capacity Units = gpmx Rating Factor (23)
The capacity Units required to meet the design thermal conditions are
calculated from Formula (23). The available Capacity Units are also
determined from Formula (23). In general, the tower capability is the
ratio of the Capacity Units available to the Capacity Units required, as
follows:
Capacity Units avail.
Capacity Units req.

31. Figure 19
However, because tests are seldom conducted with the fans operating
exactly at the design fan brake horsepower, an adjustment must be
made to account for the variation in air flow ( or fan power) Since air
rate varies directly as water rate and also as the cube root of fan power
(at constant hot water, cold water, and wet-bulb temperature ) the
adjustment is applied directly to the tea) water rate as follows :
Adj. teslgpm= test gpm x √
𝒅𝒆𝒔𝒊𝒈𝒏 𝒇𝒂𝒏 𝒃𝒉𝒑
𝒕𝒆𝒔𝒕 𝒇𝒂𝒏 𝒃𝒉𝒑
𝟑
(
The available "Capacity Units" must then be calculated as the product
of the adjusted test water rate (gpm) and the lest Rating Factor. Tower
capability (Formula (24)) must then incorporate a fan power correction
whenever required. The following example typifies the evaluation of
lest data;
Design
Test
Water Rate
(gpm):
10,000
10,83
0
Hot Water
Temperatur
e (°F )
105.0
99.2
Cold Water
Temperatur
e (°F ):
85.0
81.1
Wet-Bulb 76.0

32. Temperatur
e (°F ):
72.2
Range(°F) : 20.0
18.1
Figure 20
1.41 × 10,000 gpm = 14,100 Capacity Units required
Available capacity : Testing was conducted at 71.2 fan bhp, so the
calculated test gpm at 75 fan bhp (design) must be calculated, using
Formula (25).
Adj. test gpm = 10,830 × √
75
71.2
3
= 11,019 gpm
Because the test was conducted at 72.2 F wet bulb and 8.9 F approach,
a double interpolation is required to obtain the corresponding lest
Rating Factor.
Rating factor
@
8
A
@
9
A
°
@
1
0
A
F
o
r
1
8
.
1

33. ° °
1
.
5
2
0
1
.
3
7
0
1
.
2
5
0
1
.
3
3
5
1
.
2
0
5
1
.
1
0
0
1
.
1
9
0
1
.
0
8
0
0
.
9
8
5
Fig. 144.701°wet-bulb
Fig. 145.74°wet-bulb
Fig. 146.78'wet-bulb
The Rating Factor for each approach areplotted against wet-bulb
temperature shown in Figure148. The Rating Factors for 72.2'F wet-
bulb and 8° 9° & 10°F approach are read from this curve aa 1.414,
1.276 & 1.162 respectively. Thesefactors arethen plotted in Figure
149, and 1.29 is seen to be the Rating Factor unique to an 8.9 °F
approach, an 18.1 °F range, and a 72.2 °F wet-bulb temperature.
Substituting calculated values in Formula (23):
Capacity Units available = 1.29 × 11,019
(adjusted test gpm ) = 14, 215
substituting the available and required
Capacity Units in Formula (24):
Tower Capability =
14,215 ×100
14,100
= 100.8 %
The test indicates that the tower will cool 100.8%
of the design water rate, or that it has 1 00.8%
of the required capacity. This is well within recognized
test tolerances of ±2%, under stable test conditions

34. Chapter 4
Electrical components
MOTORS & VARIABLE SPEED DRIVES
Electric motors are used in HVAC systems to drive fans, pumps, refrigeration equipment and
other processes thatrequire motive (moving) force.
Figure 21
Motors rely on a very simple principle that mostof us have seen when the ‘like’ poles of two
magnets are broughtclosetogether.
A forceflings them apart, as twosouth poles repel, as two north poles repel.
Squirrel cage induction motor:
The Squirrel cage induction motor which is the most common electric motor has four main
parts:
1.Stator: it is a stationary componentmade of copper windings that carry current. The stator’s
coils set up a magnetic field that moves in a circular motion. The stator surrounds the Rotor.
2. Rotor: as the name suggests,itrotates.It is caused to rotate under the influence of the
magnetic field of the stator. The rotor tries to keep up with the stator’s magnetic field.
3. Fan: it is used to cool the motor.
4.Bearings and seals: allow a motor shaft to move smoothly and reduce energy losses that

35. would occur through friction.The seals keep dust from entering the motor.
Figure 22
There are severaladvantages to the induction motor: no brushes or commutator means easier
manufacture, no wear, no sparks, no ozoneproduction and none of the energy loss associated
with them.
Speed of rotation: synchronous speed:
The synchronous speed of a motor can be determined by the following formula: Where:
Synchronous speed =
𝟏𝟐𝟎 ×𝒇
𝒏𝒐.𝒐𝒇 𝒑𝒐𝒍𝒆𝒔
• speed is expressed in rpm (revolutions per minute)
• f equals frequency in Hz (hertz)
• poles is an even number i.e. 2,4,6 etc.
The ideal speed of rotation is determined by two (2) factors:
1. The number of magnetic poles.
2. The frequency of the AC supply.
It is possible to arrange the stator windings in such formations as to provide any number of
pairs of poles and so we can offer 2, 4, 6, 8, 10, 12 pole motors. Motors over 12 poles are
available if required, but they are not in common use.
rotor

36. motors are best suited to operate in heavy conditions, driving
processes in particularly critical environments requiring equally difficult
work cycles. Rotors can especially be subject to external harmful
vibrations that can reduce their useful lifetime
Figure 23
bearings
are an essential element for a smooth, free of vibration and low noise
motor operation.
Figure 24
stator
The stator core relies on the proven and robust ABB design used in all
modular induction motors.

37. Figure 25
slip
In any AC induction motor the synchronous speed is never achievable,
since friction losses in the bearings, air resistance within the motor,
and additional drag imposed by the load combine to cause the rotor to
lag slightly behind the rotational speed of the magnetic field. This
lagging effect is known as the slip. The percentage slip varies from one
motor to the next. As a general rule of thumb, the larger the motor, the
less slip is experienced. For any given motor the slip will decrease as
the load decreases. At no load, the slip may be as little as 0.5%, while
at full load and depending on the size of the motor, it can be as high as
5.0%.

38. Figure 26
Actual speed:
The actual speed is determined by following:
• the slip
• the loading of the motor
It is not surprising to find that the slip of a motor is closely related to
the motor's efficiency and, in fact, the full load speed of a motor is a
good indicator of the motor's efficiency.
Motor Efficiency:
We all know that to get a motor to do work we need to supply a source
of electrical power. In an ideal world, all of the power that is put in
would be seen at the output. However, all real systems have losses:
Power losses in induction motors can be grouped into two main
components. These are: Fixed losses, i.e. independent of motor load:
• Iron or magnetic loss in the stator and rotor cores
• Friction and windage loss
Losses proportional to the motor load:
• Resistive (I2 R) or copper loss in the stator and rotor conductors
• Stray loss caused by components of stray flux

39. Figure 27
Defining Efficiency:
'Efficiency is the percentage of the power input that reaches the load:
Where: η =
𝑷 𝒐𝒖𝒕
𝑷 𝒊𝒏
• η is a decimal value; if multiplied by 100, it will give the efficiency as a
percentage.
• Pout is the output power.
• Pin is the input power. The efficiency rating of an induction motor
accounts for the losses in both the stator and the rotor.
• In the ideal world an electric motor would be 100% efficient.
• In the real world it is more realistic to expect 50% efficiency.
• Low efficiency means higher running costs.

40. • Not all electric motors are created equal. Some are more efficient
than others.
Motor Sizing:
Motors are most efficient when they are optimally loaded. A significant
reduction in efficiency occurs at loads of 25% full load or less, and it is
at this level that serious consideration should be given to fitting a
smaller motor.
It is important to remember that it is the load that determines how
much power the motor draws. The size of the motor does not
necessarily relate to the power being drawn. For example, a fan
requiring 15 kW could be driven by 15 kW motor – in this case it is well
matched. It could also be driven by a 55 kW motor, and although it
would work, it would not be very efficient. However connecting it to a
10 kW motor would soon cause the motor to trip out. This shows the
importance of knowing the actual power drawn by the motor
Cooling Tower Features
 Increased efficiency and power factor performance
 Operates at optimal systemefficiency point with variablespeed control
 Increased systemreliability with fewer mechanical parts
 Simplified installation or retrofitwith gearbox foot print
 Easy to use drive controlparameters
 Interfaces easily to building automation control systems

41.  Replaces high maintenance conventionalgear and belt drivearrangements
 Quieter operation than conventional motor/gearbox system

42. Reference