Section - 11 - Cooling - Towers - XLSX
Section - 11 - Cooling - Towers - XLSX
Section - 11 - Cooling - Towers - XLSX
11-1
Nomenclature
Acfm = actual volumetric flow rate of air-vapor mixture, lba =
cu ft/min
ahp = air horsepower, hp lbw =
AWB = ambient wet bulb temperature, °F L =
B = combined water loss through blowdown and LG =
windage, % of circulating water or cu ft/min
CWT = cold water temperature, °F Q =
DB = dry bulb temperature, °F PF
E = water evaporated, % of circulating water or cu R
ft/min
gpm = gallons per minute V
G = air rate, lb/(sq ft • hr) va =
ha = specific enthalpy of dry air, BTU/lb vas =
has = hs - ha, BTU/lb vs =
Air Horsepower = The power output developed by a fan in moving a Fan Deck =
given air rate against a given resistance.
Air Inlet = Opening in a cooling tower through which air Fan Pitch =
enters. Sometimes referred to as the louvered
face on induced draft towers.
Air Rate = Mass flow of dry air per square foot of cross- Fill =
sectional area in the tower's heat transfer region
per hour.
Air Velocity = Velocity of air-vapor mixture through a specific Forced Draft =
region of the tower (i.e. the fan).
Circulation Rate = Actual water flow rate through a given tower. Natural Draft =
Cold Water = Temperature of the water leaving the collection Net Effect Volume =
Temperature basin, exclusive of any temperature effects
incurred by the addition of makeup and/or the
removal of blowdown.
Collection Basin = Chamber below and integral with the tower where Performance Factor =
water is transiently collected and directed to the
sump or pump suction line.
Counterflow = Air flow direction through the fill is counter- Psychrometer =
current to that of the falling water.
KEY
= Example calculation from the book
= Application worksheet for user to fill out
= Numbers that must be filled in according to the user's data and specific situation
= Numbers that must be filled in according to
graphs and charts
pounds of dry air
pounds of water
water rate, lb/(sq ft • hr)
liquid to gas ratio, lb/lb
cu ft/min
performance factor, dimensionless
cooling tower range, °F
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
This is commonly referred to as 20° Range (105-85) and 10° Approach (85-75).
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
Application 11-1 -- Effect of Varying WB Temperature on Cold Water Temperature (CWT)
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
This is commonly referred to as 20° Range (105-85) and 10° Approach (85-75).
mples published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing in
ulation spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA
accuracy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose o
luding without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to
ation based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site condition
ce to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with Gas Processo
is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information. Reference h
s for a particular purpose or non-infringement of intellectual property.
e, inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any other legal th
perial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process conditions
cooperation with Gas Processors Association (GPA).
such information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name, trademark,
tract, tort or any other legal theory and whether or not advised of the possibility of such damages.
ount actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitations.
ice by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recommendation or fa
dead-band limitations.
sement, recommendation or favoring by the GPA and/or GPSA.
Example 11-2 -- Effect of Varying Cooling Range on Cold Water Temperature Application 11-2 -- Effect of V
What is the new CWT when cooling range is changed from What is the new CWT when co
20 ° to 30 °?
(50% increase in heat load) with gpm and WB held constant? (50% increase in heat load) wi
Enter Nomograph at 85° CWT, go horizontally to 75° WB, vertically to R = 20° F, Enter Nomograph at 85° CWT
horizontally to R = 30° F, vertically downward to 75° WB, read new CWT of horizontally to R = 30° F, verti
87.5 °.
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
plication 11-2 -- Effect of Varying Cooling Range on Cold Water Temperature
= 1000 gpm
= 105 °F
= 85 °F
= 75 °F
es published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing indu
tion spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA an
curacy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose or n
ding without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to or
on based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site conditions e
on as a service to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with G
information is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information.
bility, fitness for a particular purpose or non-infringement of intellectual property.
rom the use, inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any ot
ositions, imperial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process
nd edited in cooperation with Gas Processors Association (GPA).
meliness of such information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name
warranty, contract, tort or any other legal theory and whether or not advised of the possibility of such damages.
king into account actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitati
cess, or service by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recomme
What is the new CWT when water circulation is changed from 1000 gpm to 1500
gpm (50% change in heat load at constant Range).
Varying water rate, particularly over wide ranges, may require modifications to the distribution
system. Enter Nomograph at 85° CWT, go horizontally to 75° WB, vertically to R = 20° F,
horizontally to Performance Factor of
3.1 .
Obtain new PF by multiplying (3.1)(1500/1000) = 4.65, then enter Nomograph at PF of 4.65, go
horizontally to R = 20° F, vertically down to 75° WB, read new CWT of
90.5° .
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
Application 11-3 -- Effect of Varying Water Circulating Rate and Heat Load on
Cold Water Temperature
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
What is the new CWT when water circulation is changed from 1000 gpm to 1500
gpm (50% change in heat load at constant Range).
Varying water rate, particularly over wide ranges, may require modifications to the distribution
system. Enter Nomograph at 85° CWT, go horizontally to 75° WB, vertically to R = 20° F,
horizontally to Performance Factor of
3.1 .
Obtain new PF by multiplying (3.1)(1500/1000) = 4.65, then enter Nomograph at PF of 4.65, go
horizontally to R = 20° F, vertically down to 75° WB, read new CWT of
90.5 °.
published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing industry
spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA and G
acy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose or non-
without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to or reli
based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site conditions etc)
o the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with Gas Processors
voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information. Reference here
r a particular purpose or non-infringement of intellectual property.
ability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any other legal theory
al curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process conditions, flu
tion with Gas Processors Association (GPA).
ormation. Reference herein to any specific commercial product, calculation method, process, or service by trade-name, trademark, and serv
t or any other legal theory and whether or not advised of the possibility of such damages.
ual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitations.
rvice by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recommendation or
nt dead-band limitations.
dorsement, recommendation or favoring by the GPA and/or GPSA.
Example 11-4 -- Effect of Varying WB Temperature, Range, and Water Circulating Rate on
Cold Water Temperature
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
Enter Nomograph at 85° CWT, go horizontally to 75° WB, vertically to R = 20° F, horizontally read PF =
3.1
then multiply (3.1)(1250/1000) = 3.88 (new PF). Enter Nomograph at PF = 3.88, go horizontally to R = 25° F,
vertically down to 60° WB, read new CWT of
82 °.
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
Application 11-4 -- Effect of Varying WB Temperature, Range, and Water Circulating Rate on
Cold Water Temperature
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
Enter Nomograph at 85° CWT, go horizontally to 75° WB, vertically to R = 20° F, horizontally read PF
3.1
then multiply (3.1)(1250/1000) = 3.88 (new PF). Enter Nomograph at PF = 3.88, go horizontally to R = 25° F,
vertically down to 60° WB, read new CWT of
82 °.
les published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing indu
tion spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA an
curacy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose or n
ding without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to or
on based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site conditions e
ulating Rate on
60
1000
orizontally read PF
orizontally to R = 25° F,
vice to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with Gas Proces
n is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information. Reference
ess for a particular purpose or non-infringement of intellectual property.
se, inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any other legal t
mperial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process condition
operation with Gas Processors Association (GPA).
ch information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name, trademark, an
ct, tort or any other legal theory and whether or not advised of the possibility of such damages.
nt actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitations.
by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recommendation or favo
d-band limitations.
ment, recommendation or favoring by the GPA and/or GPSA.
Example 11-5 -- Effect of Varying Fan HP Input on Cold Water Temperature Application 11-5 -- Effect of Va
What is the new CWT if motor is changed from 20 HP to 25 What is the new CWT if motor i
HP in Example 11-4? Example 11-4 information given below: HP in Example 11-4? Example
WB change: 75 to 60 WB change:
R change: 20 to 25 R change:
GPM change: 1000 to 1250 GPM change:
Original PF: 3.1 (see previous example for how to get this value) Original PF:
The air flow rate varies as the cube root of the horsepower and performance varies The air flow rate varies as the cu
almost directly with the ratio of water rate to air rate, therefore the change in air almost directly with the ratio of
flow rate can be applied to the Performance Factor. Increasing the air flow rate flow rate can be applied to the P
(by installing a larger motor) decreases the Performance Factor. (by installing a larger motor) dec
PF correction factor = (25 HP/20 HP)^(1/3) = 1.077. Divide PF by PF correction PF correction factor = (25 HP/20
factor to get new PF. Applying this to Example 11-4, we get 3.875/1.077 = 3.6. factor to get new PF. Applying
Enter Nomograph at 3.6 PF (instead of 3.88 PF) go horizontally to R =25° F, Enter Nomograph at 3.6 PF (inst
vertically down to 60° WB, read CWT of vertically down to 60° WB, read
81 °.
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
cation 11-5 -- Effect of Varying Fan HP Input on Cold Water Temperature
= 1000 gpm
= 105 °F
= 85 °F
= 75 °F
r flow rate varies as the cube root of the horsepower and performance varies
directly with the ratio of water rate to air rate, therefore the change in air
ate can be applied to the Performance Factor. Increasing the air flow rate
stalling a larger motor) decreases the Performance Factor.
s published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing indust
on spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA and
uracy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose or no
ng without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to or re
n based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site conditions etc
ce to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with Gas Processo
is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information. Reference h
s for a particular purpose or non-infringement of intellectual property.
inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any other legal the
erial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process conditions,
d edited in cooperation with Gas Processors Association (GPA).
eliness of such information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name, tr
ranty, contract, tort or any other legal theory and whether or not advised of the possibility of such damages.
ng into account actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitation
ss, or service by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recommend
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
Use the PF correction factor from Example 11-5 to increase gpm instead of decreasing
CWT.
Example 11-5:
What is the new CWT if motor is changed from 20 HP to 25
HP in Example 11-4? Example 11-4 information given below:
WB change: 75 to 60
R change: 20 to 25
GPM change: 1000 to 1250
Original PF: 3.1 (see example 11-4 for how to get this value)
In Example 11-4, we developed a new CWT of 82 when circulating 1250 gpm at R = 25° F
and 60° WB. If motor HP is increased from 20 to 25 under these conditions with PF
correction factor = 1.077 (as shown in Example 11-5), GPM could be increased from 1250
to (1250)(1.077) =
1347 gpm.
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
Application 11-6 -- Effect of correction factor on gpm instead of Cold Water Temperature
Given Data:
Flow = 1000 gpm
Hot Water = 105 °F
Cold Water = 85 °F
Wet Bulb = 75 °F
Use the PF correction factor from Example 11-5 to increase gpm instead of decreasing CWT.
Example 11-5:
What is the new CWT if motor is changed from 20 HP to 25
HP in Example 11-4? Example 11-4 information given below:
WB change: 75 to 60
R change: 20 to 25
GPM change: 1000 to 1250
Original PF: 3.1 (see example 11-4 for how to get this value)
In Example 11-4, we developed a new CWT of 82° when circulating 1250 gpm at R = 25° F
and 60° WB. If motor HP is increased from 20 to 25 under these conditions with PF
correction factor = 1.077 (as shown in Example 11-5), GPM could be increased from 1250 to
(1250)(1.077) =
1347 gpm.
g examples published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas process
d calculation spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the
es of accuracy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purp
r (including without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , referen
calculation based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site con
on as a service to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with G
information is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information.
bility, fitness for a particular purpose or non-infringement of intellectual property.
rom the use, inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any ot
ositions, imperial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process
nd edited in cooperation with Gas Processors Association (GPA).
meliness of such information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name,
arranty, contract, tort or any other legal theory and whether or not advised of the possibility of such damages.
ing into account actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitatio
ess, or service by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, recommen
Calculate the concentrations and blowdown rate for the following cooling tower:
Circulation Rate = 10000 gpm
Water Temperature
Drop Through Tower = 20 °F
Type of Tower = Mechanical-draft towers
Blowdown Rate = 20 gpm
or 0.2% of circulation rate
Therefore:
Evaporation Loss = 2% (1% for each 10° temperature drop)
Windage Loss = 0.3% (Maximum for mechanical draft tower, p. 11-9)
B = E / (Cycles - 1) = 0.67%
The windage component of B is 0.003, therefore the blowdown rate required would be
0.0067 - 0.003 = 0.0037 or
(10000 gpm) (0.0037) =
37 gpm.
The sample calculations, equations and spreadsheets presented herein were developed using examples published in the Enginee
While every effort has been made to present accurate and reliable technical information and calculation spreadsheets based on t
The Calculation Spreadsheets are provided without warranty of any kind including warranties of accuracy or reasonableness of
In no event will the GPA or GPSA and their members be liable for any damages whatsoever (including without limitation, thos
These calculation spreadsheets are provided to provide an “Operational level” of accuracy calculation based on rather broad ass
Application 11-7 -- Cooling tower calculations on concentration and blowdown rate
Calculate the concentrations and blowdown rate for the following cooling tower:
Circulation Rate = 10000 gpm
Water Temperature Drop
Through Tower = 20 °F
Type of Tower = Mechanical-draft towers
Blowdown Rate = 20 gpm
or 0.2% of circulation rate
Therefore:
Evaporation Loss = 2% (1% for each 10° temperature drop)
Windage Loss = 0.3% Maximum for Mechanical-draft towers, p. 11-9
B = E / (Cycles - 1) = 0.67%
The windage component of B is 0.003, therefore the blowdown rate required would be 0.0067
- 0.003 = 0.0037 or
(10000 gpm) (0.0037) =
37 gpm.
ples published in the Engineering Data Book as published by the Gas Processor Suppliers Association as a service to the gas processing ind
lation spreadsheets based on the GPSA Engineering Data Book sample calculations, the use of such information is voluntary and the GPA a
accuracy or reasonableness of factual or scientific assumptions, studies or conclusions, or merchantability, fitness for a particular purpose or
uding without limitation, those resulting from lost profits, lost data or business interruption) arising from the use, inability to , reference to o
tion based on rather broad assumptions (including but not limited to; temperatures, pressures, compositions, imperial curves, site conditions
ft towers, p. 11-9
4.0
a service to the gas processing industry. All information and calculation formulae has been compiled and edited in cooperation with Gas Pr
mation is voluntary and the GPA and GPSA do not guarantee the accuracy, completeness, efficacy or timeliness of such information. Refer
fitness for a particular purpose or non-infringement of intellectual property.
he use, inability to , reference to or reliance on the information in thes Publication, whether based on warranty, contract, tort or any other le
ns, imperial curves, site conditions etc) and do not replace detailed and accurate Design Engineering taking into account actual process cond
edited in cooperation with Gas Processors Association (GPA).
eliness of such information. Reference herein to any specific commercial product, calculation method, process, or service by trade-name, tr
ranty, contract, tort or any other legal theory and whether or not advised of the possibility of such damages.
g into account actual process conditions, fluid properties, equipment condition or fowling and actual control set-point dead-band limitations
hod, process, or service by trade-name, trademark, and service mark manufacturer or otherwise does not constitute or imply endorsement, r