This test procedure describes the evaluation method used to determine the water consumption performance of cooling towers and evaporative cooling equipment, which provides a unified test instrument, test procedure, parameter measurement, test data processing, and test results. This test procedure provides the manufacturer and the owner an objective and fair evaluation, outlines practical methods for monitoring the water consumption performance of cooling towers. The loss of water in cooling tower is measured by U-type liquidometer, and the law of collecting basin liquid level. When the liquid level of the collecting basin decreased by 1 mm, the water quantity loss of one cooling tower diameter D =42 m was 1.38 m ³ . And cooling tower water loss and specification for water balance test is established. The water quantity loss of cooling tower can be obtained conveniently, accurately and quickly. This provides conditions for further accurate analysis of water quantity loss of cooling tower, etc. It is widely used and has great significance in the hydraulic design of cooling tower, the analysis of air status in the tower, the water balance test to determine the water used in cooling tower, the reduction of water loss and the drift recovery. And provides explicit test procedures that yield results with the highest level of accuracy and consistent with the best current engineering practices and knowledge in this field.
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Specification for water balance test of cooling towers
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CEEPE 2020
Journal of Physics: Conference Series 1585 (2020) 012013
IOP Publishing
doi:10.1088/1742-6596/1585/1/012013
1
Specification for water balance test of cooling towers
Baohong Song, Yu Song
Guizhou Colorful Sunshine Water Co. LTD. No.314, Lvyinhu Industrial Incubation
Park, Duyun City, China, 558000
E-mail:3078601189@qq.com
Abstract. This test procedure describes the evaluation method used to determine the water
consumption performance of cooling towers and evaporative cooling equipment, which
provides a unified test instrument, test procedure, parameter measurement, test data processing,
and test results. This test procedure provides the manufacturer and the owner an objective and
fair evaluation, outlines practical methods for monitoring the water consumption performance
of cooling towers. The loss of water in cooling tower is measured by U-type liquidometer, and
the law of collecting basin liquid level. When the liquid level of the collecting basin decreased
by 1 mm, the water quantity loss of one cooling tower diameter D=42 m was 1.38 m3. And
cooling tower water loss and specification for water balance test is established. The water
quantity loss of cooling tower can be obtained conveniently, accurately and quickly. This
provides conditions for further accurate analysis of water quantity loss of cooling tower, etc. It
is widely used and has great significance in the hydraulic design of cooling tower, the analysis
of air status in the tower, the water balance test to determine the water used in cooling tower,
the reduction of water loss and the drift recovery. And provides explicit test procedures that
yield results with the highest level of accuracy and consistent with the best current engineering
practices and knowledge in this field.
1. Introduction
Literature [1] shows that there is no direct test method for evaporation loss. In literature [1], [2] the
evaporation loss of cooling tower is analysed by using complex methods of approximate estimation or
air humidity ratio difference between inlet and outlet. However, the variation law of evaporation loss
of cooling tower is not explained. Some standards [3],[4],[5],[6] also extensively use sensitive paper to
test drift. And standards [6] adopted tracer and other measures to test drift and Literature [7] tested and
analyzed the plume. Literature [1],[3] shows that empirical estimation is also widely applications in
engineering. Oskar Javier Gonzalez Pedraza et al. [8] estimated the evaporation loss and used the
Euler– Lagrange equation to simulate the falling process of drips numerically in forced airflow. M.
Lucas et al. [9] investigated the effects of ambient temperature, humidity, drift temperature at the
tower outlet on drift loss (and thus deposition). However, the failure of these analyses to obtain
accurate water quantity loss of cooling tower will cause the analysis results to be inconsistent with the
actual changes of drifts, and doesn't explain the law of drifts variation.
For a long time, water quantity loss of cooling tower is not convenient for direct, accurate and real-
time measurement. At present, in practical engineering application, data collection is carried out by the
make-up water meter. The test average of cooling tower water loss is obtained through long time
tracking test, so as to reduce the error value as much as possible. For this reason, such average cannot
well explain and further analyze the water quantity loss of cooling tower. It can neither provide
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doi:10.1088/1742-6596/1585/1/012013
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accurate reference data in the hydraulic design and the application of water balance engineering of
cooling tower, nor can it explain some scientific phenomena such as the air state in the tower. It brings
difficulties to the design and application of cooling tower.
Baohong Song [10] proposed to change the existing test mode of water quantity loss of cooling tower.
The U-tube liquidometer was adopted to test the liquid level in the collecting basin, and it is used
together with the make-up water flowmeter, so as to obtain the water quantity loss of the cooling tower.
Baohong Song [11] studied the loss of water in cooling tower is measured by U-type liquidometer,
and the law of collecting basin liquid level and cooling tower water loss and specification for water
balance test is established. The water quantity loss of cooling tower can be obtained conveniently,
accurately and quickly. This provides conditions for further accurate analysis of water quantity loss of
cooling tower, etc.
This test procedure describes the evaluation method used to determine the water consumption
performance of cooling towers and evaporative cooling equipment, which provides a unified test
instrument, test procedure, parameter measurement, test data processing, and test results. This test
procedure provides the manufacturer and the owner an objective and fair evaluation, and explicit test
procedures that yield results with the highest level of accuracy, and consistent with the best current
engineering practices and knowledge in this field.
The following review sequence is recommended to assist in a comprehensive study of this
specification.
This specification can be learned by reading the introduction to each section and the testing process
that follows.
Performance monitoring projects should check this specification or citation specification initially to
examine the details of the code section.
When this specification is used to determine the performance of contractual obligations, the
contracting parties shall agree on test procedures, uncertainty estimates and definitions, data
representation methods, and result representations in advance. Testing the thermal performance of the
cooling tower and issuing an accurate test report are also suggested.
Considerable efforts were exerted to write this cooling tower Code to contain all the related
technology within the document itself. However, this approach was impossible in all instances. In
these cases, and unless otherwise specified, all references to other codes refer primarily to standards
[12] or to standards [13]. Instruments and equipment for water balance testing are described in detail
in this specification. The descriptions of instruments and apparatus of thermal performance testing
may be found in the standards ASME PTC 19 series of supplemental codes or standards [13]. The
general basis of the uncertainty analysis beyond that specified in this Code may be found in the
supplement standards ASME PTC 19.1, Test Uncertainty. A careful study of all the referenced codes
should be conducted. However, quotative instructions shall govern when discrepancies between
specific directions contained herein and those codes incorporated by reference arise.
This specification mainly introduces the method of obtaining real-time and accurate cooling tower
water loss data. The accurate thermal performance of cooling tower (relevant thermal performance
parameters need to be collected) is investigated by establishing the accurate water balance condition of
cooling tower, and the change in water loss in the cooling tower is analyzed on the basis of the
alterations in water level in collecting basin, the law of water loss in cooling tower, the laws of
evaporation loss and drift loss, and drift recovery. This approach is widely used in the fields of
engineering application, design, and research on water loss control of cooling tower operation
parameters.
2. Procedure
2.1. Range
This standard provides uniform procedures for the water balance testing of industrial circulating water
wet cooling towers, the measurement of each parameter, the processing of test data, and the evaluation
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of test results. However, this specification does not include the test of thermal performance-related
items of the wet cooling tower. The ASME PTC 23 and CTI-ATC-105 test standards present the
thermal performance test and analysis. However, the thermal performance of the wet cooling tower
should be tested simultaneously, and the test report should be issued.
This specification provides the latest accurate data processing and evaluation of evaporation and drift
losses.
This standard is applicable to the acceptance test of water balance for new or modified industrial
circulating water cooling towers of wet mechanical and natural drafts. Water balance test of cooling
tower with non-acceptance check nature can refer to this standard. This standard is applicable to the
natural draft cooling tower with or without drift recovery projects.
This standard does not apply to air cooling towers and chimneys.
2.2. Criteria for quotations and references
The terms in the following documents are referenced by this standard and has become the terms of this
standard. For undated references, the latest version applies to this standard.
CTI-ATC-140. Isokinetic drift measurement test code for water cooling tower. USA.
ASME PTC 23 American National Standard Atmospheric Water Cooling Equipment Performance
Test Codes.
CTI-ATC-105 Acceptance Test Code for Water Cooling Towers;
CTI-ATC-150 Acceptance Test Procedure for Wet-Dry Plume Abatement Cooling Towers;
Baohong Song. Test Study of Water Loss of Cooling Tower on U - Type Liquidometer. Intemational
Conference on Energy Engineering and Environmental Protection (EEEP 2019) Xiamen. 2019.
Baohong Song. A accurate measurement method for water loss of cooling tower. [P] Chinese patent.
CN 2019104830076. 2019.
2.3. Definition
The wet cooling tower contains mechanical draft wet cooling tower and natural draft wet cooling
tower.
In this specification, the "evaporation" refers to form the water vapor of vapor phase in the cooling
tower. "evaporation loss" refers to the loss of water vapor of invisible from the cooling tower outlet.
Namely, it is the loss water quantity of increase of air humidity ratio in the tower.
Drift: In the operation of an evaporative cooling tower, moving air contacts water for heat transfer.
The circulating water is distributed as droplets or films to maximize the surface area exposed to the air.
In these processes, small water droplets are entrained in the air moving through the tower. Droplets
that are not removed from the air stream are exhausted from the cooling tower into the environment.
These droplets which possess the same minerals (but not necessarily in the same concentrations) as the
circulating water.
Drift loss: Water lost from the tower as liquid droplets entrained in the outlet air.
Cooling tower cell: A cooling tower "cell" is the smallest subdivision of the tower, bounded by
exterior walls and partition walls, which can function as an independent unit. Each cell may have one
or more fans or stacks distribution system.
Air flow: Total quantity of air, including associated water vapor flowing through the tower.
Makeup Water flow: the makeup water added to the circulating water system to replace water loss
from the system by evaporation, drift, purge arid leakage.
Surface area of collecting basin: It's the surface area of the liquid (water) in the collecting basin.
2.4. General rules
2.4.1. Test period selection. After the newly built or rebuilt industrial circulating water cooling tower
is placed in normal operation, the water balance of the cooling tower should be tested or multi-term
acceptance tests should be carried out on time. If the acceptance test cannot be carried out on time
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after the normal operation of the cooling tower because the test conditions do not satisfy the
requirements, then the acceptance test shall be completed within one year after the normal operation of
the cooling tower.
The water balance testing of drift water recovery devices in naturally draft cooling towers is presented
in this test procedure.
The acceptance test of cooling tower water balance shall be entrusted to the unit with cooling tower
test capability and experience.
When new or rebuilt cooling towers need to be tested for water balance acceptance, they should be
clarified in the preliminary design stage of the project, and the cost of acceptance test should be
included in the project investment estimate.
2.4.2. Step. The acceptance test of cooling tower water balance should follow the following procedure.
a) Preparation of the test work outline;
b) Preparation work prior to the test;
c) Site test;
d) Processing and analysis of test data;
e) Preparation of the acceptance test report.
2.5. Preparation work prior to the test (conducting thermal performance test in accordance with CTI-
ATC-105 at the same time is advisable).
2.5.1. Selection of test tower. The test tower shall be designated by the entrusting party. When the cell
towers in the cooling tower group is tested, the test tower can be selected through negotiation between
the entrusting party and the testing party. (For the purposes of this Code, a "cell" is defined as the
smallest subdivision of the tower, bounded by exterior walls and partition walls; it can function as an
independent unit. Each cell may have one or more fans or stacks and one or more distribution systems).
2.5.2. On-site investigation. The test department shall conduct on-site investigation on the test tower
prior to the test.
2.5.3. Uncertainty Analysis. If an uncertainty analysis is desired, then it should be agreed to by both
parties prior to the test because this analysis requires the recording of certain additional data.
2.5.4. Prepare the test outline. Prior to the cooling tower test, the test unit shall prepare the test outline.
The test syllabus should include the following.
a) Test purpose and requirements (to consider the impact of the following changes on the water loss
of the cooling tower, corresponding tests or explanations should be performed).
b) Design, construction, and operation overview of the tested cooling tower, including the following.
Cooling tower type, main geometric dimensions, water surface area of collecting basin, and
design area of water drenching.
Form, material of packing, packing height, packing length of crossflow cooling tower,
mounting support mode, and support material for packing. The design adopted the thermal and
resistance characteristics of the packing.
Drift eliminator form, material, installation location, installation mode, and design adopted for
drift eliminator resistance characteristics. The form and arrangement of the water distribution
system, the form of splash water nozzle, nozzle diameter, nozzle spacing, number of nozzle
with different diameters, and design pressure in different water distribution zones in the tower.
Mechanical draft cooling tower fan form, impeller diameter, fan characteristic curve and
design working point air volume and full pressure, and fan design shaft power.
Problems that exist in the actual operation of cooling tower.
Analysis report of circulating water quality.
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c) As-built drawings or construction drawings of the tested cooling tower, including
Location of the cooling tower in the general plan of the plant;
Plan and section of the cooling tower.
d) Test contents and test conditions.
e) Test items, measuring point arrangement, test methods, and instruments used.
f) Test tools and equipment that need to be machined.
g) Processed method of test data.
h) Analysis of cooling tower water balance.
i) Evaluation method of test results.
j) Composition and division of testers.
k) Test work schedule.
Safety operation precautions and safety measures taken.
Matters requiring the cooperation of the entrusted unit (owner).
2.5.5. Test condition. Before the test of the cooling tower begins, it should be comprehensively
inspected, and the defects of each part of the cooling tower shall be eliminated in accordance with the
design and test requirements. To ensure that the cooling tower is in a good operating condition for
testing, its components and equipment should satisfy the following requirements.
a) The water distribution system of the cooling tower shall be clean, unobstructed, and free from
debris blockage, leakage, and water overflow. The nozzle shall be intact and must have normal
spillage.
b) The appearance of the packing should be neat without defect and deformation, and the surface of
the packing should not have algae, oil, and other sundries.
c) The packing of the countercurrent cooling tower shall be filled with the packing layer. The
crossflow cooling tower should avoid direct current air passage at the top of the wet packing.
d) The surface of the drift eliminator shall be clean and free from debris, algae, and other
attachments that obstruct the normal flow of air.
e) Drift eliminator layer should be full of drift eliminator, and no air bypass channel is available.
Special operating conditions are excluded.
f) The inlet pipe valve of the cooling tower and the connection pipe valve between the cooling
towers should be opened and closed flexibly for easy adjustment.
g) The fan, motor, and reduction gear of the mechanical draft cooling tower shall operate normally.
h) The water level in the cooling tower collecting basin shall be at the normal operating level or at
the level required by the test.
i) Makeup water and blowdown flowmeters are in good condition;
j) Other requirements set forth in the test outline.
2.5.6. Preparation of instrument. In the cooling tower test, the instrument that passed the checkout
should be used, and attention should be provided to the inspection to ensure the accuracy of the
instrument in the test process to satisfy the test requirements.
2.5.7. Determination of site conditions. The following tasks shall be completed at the test site prior to
the cooling tower test.
a) The location of the measuring points is determined for each test item;
b) The test platform should be set up;
c) The automatic test items of the temporary power supply should be set up;
d) Processing and installation of platform and racks for placing instruments, preparation of test
equipment and instruments.
2.5.8. Ready to forms. Record forms for various tests should be prepared prior to testing.
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2.5.9. Predictive test. Prior to the test, the personnel participating in the test should be organized to
familiarize with the test items and the instruments used, and the predictive test of the items is carried
out in accordance with the requirements of the test outline.
2.6. Test instruments and measurement methods
This specification only describes the instruments and equipment required for water balance testing.
CTI-ATC-105 shows the thermal performance test equipment.
2.6.1. Classification and structure type of level gauge. Different working principles can be divided
into liquid column type, mechanical type, and sensor type forms.
a) Liquid column. Liquid column, such as the u-tube level gauge, is based on the principle of
hydrostatics to convert the pressure signal into the liquid column height signal, often using water
as the working medium of the gauge. The scale is the standard length ruler, and the minimum
resolution is 1 mm.
b) Mechanical. The use of the principle of buoy, buoy mark, and mark up and down on the ruler can
show the change in the level to obtain the level reading, and the minimum resolution is 1mm.
c) Liquid level sensor (automatic data recording system). The principle of liquid level sensor is to
convert the liquid level signal into some types of electrical signal, such as infrared liquid level
meter and radar liquid level meter. Then, the signal is sent back to the machine for reception, and
the minimum resolution is 1 mm.
2.6.2. U-tube liquidometer material. The substrate is made of wood board, aluminum alloy, and glass
reinforced plastic. The surface is painted yellow. U-tube is made of plexiglass tube or glass tube. The
dividing ruler is a standard straightedge with a minimum resolution of 1 mm.
2.6.3. Method used by U-type liquidometer. The U-type liquidometer is vertically mounted at the same
height with the same level as the collecting basin. Then, water was pumped to the transparent siphon
tube and air is eliminated. One end of the tube was placed into the water of the collecting basin, and
the other end was connected to the U-tube liquidometer. The working fluid (water) is shown between
the upper and middle U-shaped glass tube.
When reading, the line of sight should be consistent with the height of the liquid in the U-tube, and
then the line value of the scale is the height value of the liquid level in the catchment tank. When
waiting for the next test time, the method is the same as the above to obtain the reading value of
another measurement.
The change quantity of the liquid level in this period can be obtained through the difference of two
readings, and the value of water loss of the cooling tower can be obtained according to the change law
of the collecting basin liquid level and water loss of the cooling tower.
2.6.4. Liquid level sensor. The liquid level sensor is recommended to be used in accordance with the
instructions to obtain accurate automated test data results.
2.7. Cooling tower water balance test
2.7.1. Test condition. When testing the water loss of the cooling tower, the environmental
meteorological conditions shall satisfy the following requirements.
a) The test should be conducted during the daytime in summer close to the designed meteorological
conditions or higher temperature seasons (when thermal performance analysis is required). In
accordance with the purpose of the test, water balance tests can also be conducted in winter or
other seasons for testing purposes.
b) Testing should not be conducted during rain or immediately after the rain. The start time of the
test after the rain should be 1 h after the rain stops.
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c) The average ambient wind speed of the mechanical draft cooling tower shall not be greater than
4.5 m s-1, and the ambient wind speed of the gust per minute shall not be greater than 7.0 m s -1 .
The average ambient wind speed of the natural draft cooling tower shall not be greater than 3.0 m
s-1 , and the ambient wind speed of the gust per minute shall not be greater than 5.0 m s-1 .
d) During the testing of the natural draft cooling tower, the tester on the ground visually eyeballing
that the hot and humid air flow from the air duct outlet of the natural draft cooling tower should
fill the air duct outlet. No air flows back into the cooling tower at the top of the tower.
e) In circulating water quality, the cooling tower inlet should comply with the "Standard Methods
for the Examination of Water, Sewage, and Industrial Wastes" published by the American Public
Health Association of the relevant provisions.
In the test of water balance and thermal performance of cooling tower, the allowable deviation
range of the main parameters from the design value is shown in Table 1. The testing range of each
parameter can be determined according to the testing needs of the non-acceptance cooling tower
test. When the water temperature in the tower inlet deviates from the design value and the water
temperature difference from the design value is large, the influence of the water temperature in the
tower inlet on the cooling tower performance should be calculated.
Table 1, the main parameters are allowed to deviate from the design value range.
Deviation from the design value range is
allowed
Dry bulb temperature of tower inlet t
Wet bulb temperature of tower inlet t
Water flow of tower inlet W
The water temperature difference
between tower inlet and outlet Δt
f) The liquid level and the scale line misalignment of the artificial reading are in accordance with
the liquid level in advance or appropriate to extend the time of testing within ±3–5 min. In the
calculation, the data need to return to the original test time value for the omni hora. Taking
pictures is suggested to record the liquid level value, and using a camera that can record the time
to take pictures is advisable. The liquid level interpretation on the computer is carried out. Using
the level sensor together with the U-type liquidometer is recommended.
g) During the test, the makeup water enters the circulating water system, and the makeup water
pipeline shall be equipped with a flowmeter or ultrasonic flowmeter. Otherwise, the makeup
water operation or test work shall be cancelled.
h) In the test, when a sewage blowdown occurs out of the circulating water system, the sewage
blowdown pipeline should be equipped with a flowmeter or ultrasonic flowmeter. Otherwise, the
sewage blowdown operation or test should be cancelled.
i) The readout of the supplementary water and the blowdown flowmeter shall be carried out
simultaneously with the reading of the U-tube liquidometer. The U-tube liquidometer, the
makeup water, and the blowdown flowmeter are set nearby and completed simultaneously.
2.7.2. Test project
a) Prior to the test, the surface area of the collecting basin should be tested first. Accurate and
reliable data of collecting basin liquid area are ensured; they serve as data source for subsequent
analysis.
b) When analyzing the thermal performance of the cooling tower and the water loss from
evaporation and drifts, relevant thermal performance tests should be carried out according to CTI-
ATC-105. Data collection items are as follows (as shown in the table 2);
Table 2 List of thermal analysis test items.
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Collecting basin liquid area
Collecting basin liquid level
Note: 1. Please select the parameter group under approach design conditions for thermal
performance analysis to determine the actual performance index of the cooling
tower.
2. The data can be averaged after three consecutive tests.
2.7.3. Test requirement
a) Each parameter shall be tested after the adjustment of the test condition and stable operation for a
period of time, from the end of the adjustment of test conditions to the beginning. The testing
time of each parameter is as follows: the single-cell mechanical draft cooling tower shall not be
less than 3 h, and the mechanical draft cooling tower group and the natural draft cooling tower
shall not be less than 6 h.
b) During the test of each working condition, the measured value of each main parameter shall be
subject to the arithmetic mean value of the measured value of each working condition.
The test duration for each working condition shall not be less than 3 h. The test times and time
intervals for each parameter shall not be less than those specified in Tables 3.
Table 3 Test times and intervals of water balance parameters per hour.
Ccollecting basin liquid level
c) The effective working point of the collecting basin liquid level test includes more than two groups.
One set uses U-tube liquidometer, and the other set uses liquid level sensor (automatic data
recording system).
2.8. Test data processing
Each parameter of each working condition should consider the arithmetic mean value of its measured
value as the representative value of this working condition.
2.8.1. Analysis of water balance. The cooling tower water balance:
where W is the makeup water flow (m3 h− 1 ); W b is blowdown loss, (m3 h− 1 ); dL is leakage loss, (kg s− 1 );
dE (kg s− 1) is the variation of water loss per unit time of the cooling tower outlet.
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When no blowdown and leakage losses, W b=0 and L=0. Then, according to the law of collecting
basin liquid level and water loss in the cooling tower in literature [10], Equation (2) is used in the
calculation.
where dh w is the change in liquid level per unit time, (m h− 1 ); A a is the surface area of the collecting
basin (m2 );
When makeup water, if the liquid level rises, it means that the amount of added water is greater than
the amount of loss, then A a *dh w is a negative sign, conversely it's a plus sign.
2.8.2. Analysis of thermal performance of cooling tower (analysis of evaporation and drift losses only) .
a) The analysis of evaporative water loss d e (kg s− 1) and drift loss E e (kg s− 1) in cooling towers
prioritizes Equations (5), (6), and (7) introduced in literature [11].
The partial pressure of water vapor can be obtained by adopting Equation (3), as follows:
where P ' is the water vapor pressure at air saturation, (MPa); and T is the temperature of the
air, (°C).
The humidity ratio is obtained by using Equation (4):
where d is the humidity ratio (kg kg− 1 DA); and P is the atmospheric pressure, (MPa);
The analysis of evaporation loss d e (kg s− 1) of the cooling tower is calculated according to
Equation (5), as follows:
where d 0 is the saturation humidity ratio (kg kg− 1 DA) that corresponds to the ambient air
isotherm; and dφ represents the changes in the relative humidity of the ambient air at the
unsaturation and saturation; G is the air flow rate in the tower (kg s− 1 ).
The ambient air and tower outlet air temperature dt are in the range of 20 °C –40 °C, and it is
recommended for use in Equation (6) in the evaporation loss of cooling tower to solve d e .
a= 0.00172;
where the air temperature change at the tower inlet and outlet is dt (°C).
b) The analysis of the drift water loss E e (kg s− 1) of the cooling tower should be calculated according
to Equation (7), as follows:
c) The principle of heat balance analyzes evaporation loss d e and drift loss E e as follows:
In accordance with the principle of thermal balance, given that the increment of air enthalpy
entering the differential unit simultaneously is equal to the heat loss of the inside water, Eq. (8)
is obtained as follows. Air enthalpy i 2 at the tower outlet can be calculated according to
Equation (8):
where dE is the change of water loss of the tower outlet (kg s − 1); the air flow is G (kg s− 1); the
specific water heat is c (kJ kg− 1 ·°C− 1 ). The circulating water temperature of the tower inlet is
tw1 (°C); the temperature change of the circulating water is dt w (°C). The change in enthalpy of
the air in the tower inlet and outlet is di (kJ kg −1).
The air temperature t 2 at the tower outlet is obtained according to Table H in the appendix
CTI-ATC-105. The humidity ratio d2 at the tower outlet is calculated according to Equations
(10) after Equation (9) separating the variables.
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where t is the air temperature (°C) at the outlet of the tower; d is the air humidity ratio at the
tower outlet (kg kg− 1 DA).
Evaporation loss d e, that is, the increased air humidity ratio is calculated according to Equation
(11), as follows:
where d 2 and d 1 represent the air humidity ratios (kg kg− 1 DA) in the tower outlet and inlet,
respectively.
The total water content of unit discharge air in tower outlet d c (kg kg –1 DA) is calculated
according to Eq. (12):
According literature [10] the water loss dE of cooling tower outlet is equal to the evaporation
loss dd e (m3 h− 1) plus the drift loss dE e (m 3 h −1). The drift loss dE e is obtained according to
Equation (13).
2.9. Test report
After the cooling tower test is completed, the test unit shall prepare the test report, which shall include
the following contents:
a) Test tasks, test objectives, and requirements.
b) Overview of the cooling tower design, construction, and operation management, horizontal and
sectional drawing of cooling tower under test, and location map of the measuring points of each
test project.
c) Test items, test methods, placement of measuring points, instruments used, instrument names,
specifications, and accuracy.
d) Test scope and test conditions.
e) Test data processing method and test data summary.
f) Test results, evaluation, and analysis of test results.
g) Existing problems and suggestions.
h) Issues that require special clarification in accordance with the contract and owner's requirements.
i) List of units and personnel participating in the test.
2.10. Experiment
The two natural draft wet towers provided by the Guizhou Panjiang Coal Industry Co., Ltd., has the
same size. The water drenching area of one tower is 1000 m2, and the height is 60 m. Two collecting
basins, with a diameter of 42 m, are connected to each other and simultaneously supply water
operation. The rated circulating water flow of the 45 MW unit (gangue small power plant) is 9720 m3
h− 1 , and its pressure is 0.15 MPa. The water distribution system consists of channels and water pipes.
The drift eliminator is a 50 –50/160 double-wave type, and the packaging is made of plastic
35×15×60° with a height of 1.2 m. The air inlet height is 5 m.
In the circulating pump room, the U-type liquidometer is vertically mounted on the stairs with the
same level as the collecting basin (Figure 1). Then, water was pumped to the transparent siphon tube
(Φ14 mm), and air is eliminated. One end of the tube was placed into the water of the collecting basin,
and the other end was connected to the U-tube liquidometer. The U-type liquidometer is modified by a
U-type manometer. The scale plate of U-type manometer was replaced with a 1 m ruler. The
resolution is 1 mm.
CEEPE 2020
Journal of Physics: Conference Series 1585 (2020) 012013
IOP Publishing
doi:10.1088/1742-6596/1585/1/012013
11
Figure 1 Application of U-tube liquidometer in collecting basin.
3. Results
3.1. Test result
The change data of water quantity in the collecting basin per unit time are measured using the U-type
liquidometer, result see Table 4.
Table 4. Test data summary.
Note: 1. When calculating the liquid level data, the liquid level change is obtained by
subtracting the previous data.
2. This is the water data when two cooling towers are connected in parallel and
the water is supplied.
3. The no blowdown loss, W b=0.
3.2. Analysis of result
According to the liquid level of the collecting basin and the change law Eq. (2) of water quantity loss
of the cooling tower analyzed data of Table 1, result show in Table 5:
Table 5. Results of liquid level data, evaporation and drift losses.
Note: The data refer only to one cooling tower.
4. Discussion
When the liquid level of the collecting basin decreased by 1 mm, the water quantity loss of one
cooling tower diameter D=42 m was dE = W 1–A a *dh w =0–1384×(0.001– 0), E = 1.38 m3.
This finding indicates the cooling tower operation process, the circulating water flow rate, and the
inconsiderably changed temperature. However, the results show different changes in the collecting
basin level, with a max drop between group 5 and group 6, dh w =50.1–54.6, h w=4.5 cm h− 1, in Table 4.
The most water loss is group 6, dE = W 1 –A a*dh w =0 –1384×(0.501–0.546 ) , E =17.3 kg s− 1, in Table 5.
The liquid level change between 9 am and 10 am is 2.1 cm h− 1, and the increased water quantity of the
liquid level is 29.06 m3 h− 1. The minimum water quantity loss of one tower is group 1 dE = W 1 –
Aa *dhw =160/2–1384×(0.574–0.553 ) , E = 14.15 kg s− 1, in Table 5, instead of a constant.
5. Conclusion
We use the U-type liquidometer to test the water loss in the cooling tower. This work provides
conditions for the further accurate analysis of the cause of water loss.
CEEPE 2020
Journal of Physics: Conference Series 1585 (2020) 012013
IOP Publishing
doi:10.1088/1742-6596/1585/1/012013
12
This specification mainly introduces the method of obtaining real-time and accurate cooling tower
water loss data. The accurate thermal performance of cooling tower (relevant thermal performance
parameters need to be collected) is investigated by establishing the accurate water balance condition of
cooling tower, and the change in water loss in the cooling tower is analyzed on the basis of the
alterations in water level in collecting basin, the law of water loss in cooling tower, the laws of
evaporation loss and drift loss, and drift recovery. The method is widely used and is significant in the
hydraulic design of the cooling tower, the analysis of air status in the tower, the water balance test for
determining the water used in the cooling tower, and the reduction of water loss.
6. References
[1] Code for design of cooling for industrial recirculating water. (2014) GB/T 50102-2014[S].
[2] Method of measurement and evaluation of thermal performances of wet cooling towers. (2005)
BS EN 14705:2005 BRITISH STANDARD
[3] Water cooling tower Part 2. Methods for performance testing. (1988) BS 4485-2. 1988 [S]. 6-11
[4] Specification for acceptance test of water-cooling tower. (2017) T/CECS 118-2017[S]. 2-3.
[5] Acceptance test specification of industrial cooling tower. (2006) DL/T 1027-2006. 21-22.
[6] Isokinetic drift measurement test code for water cooling tower (2011) CTI-ATC-140. USA.
[7] Acceptance Test Procedure for Wet-Dry Plume Abatement Cooling Towers (1999) CTI-ATC-150.
[8] Oskar Javier González PedrazaJ, JesúsPacheco Ibarra Carlos Rubio-Maya 2018 Numerical study
of the drift and evaporation of water droplets cooled down by a forced stream of air Applied
Thermal Engineering 142 292-302
[9] M Lucas, P J MartÃnez, J Ruiz, A S Kaiser, A Viedma 2010 On the influence of psychrometric
ambient conditions on cooling tower drift deposition International Journal of Heat and Mass
Transfer 53(4) 594-604
[10] Baohong Song. (2019) A accurate measurement method for water loss of cooling tower. [P]
Chinese patent. CN 2019104830076.
[11] Baohong Song. Test Study of Water Loss of Cooling Tower on U - Type Liquidometer. 2020 IOP
Conf. Ser.: Earth Environ. Sci. 467 012034
[12] American National Standard Atmospheric Water Cooling Equipment Performance Test Codes
(2003) ASME PTC 23.
[13] Acceptance Test Code for Water Cooling Towers (2000) CTI-ATC-105.
... Baohong Song et al. [11] proposed the accurate test program of water loss of cooling tower, can analyze detailedly the drift loss and drift concentration. Under the circumstances, we'll be to the benefit of study its laws and influencing factors. ...
... Thus, water loss increases as wind speed increases. E=0.0152G +4.1852 (11) Note: d e ' is calculated by using [16]. d e '' is calculated by using [17]. ...
... Take Table 1, group 7, as an example (in this group E=13.4 kg s −1 is nearest daily mean water loss). When G increases and decreases, the result of E is obtained according to Equation (11). If [2], [16] , [17] proposed too little quantity of E e , can be ignored. ...
- Baohong Song
The water loss of a wet cooling tower was analyzed by changing the collection method for the collecting basin level data. The water quantity loss of the cooling tower was measured using a U-tube liquidometer to obtain real-time and accurate data. When the liquid level of the collecting basin decreased by 1 mm, the water quantity loss of one cooling tower was 1.38 m ³ . In stable engineering application operation and under different environmental and climatic conditions, the water quantity loss was between 13.83 kg s ⁻¹ and 18.07 kg s ⁻¹ . Through the accurate measurement of the collecting basin level and the established water quantity loss law of the cooling tower, the correctness of Merkel assumption of air saturation in the cooling tower is analyzed. In addition, the variation laws of the evaporation and drift losses of the cooling tower were established. The testing and theoretical analysis of water quantity loss by using a test device will be widely used in the design and other related engineering fields, such as the control and research of the water quantity loss of the cooling tower and the drift recovery.
Evaporation is the basic heat transfer mechanism to reduce temperature of water in a cooling tower. Drift is a phenomenon in which water particles are carried by the leaving air stream causing water losses. In both processes the droplet size plays an important role for an effective cooling and minimum losses. A numerical simulation of water droplets falling in a forced air stream was performed by means of an Eulerian-Lagrangian reference framework. The aim of this work is to investigate water droplet size, inlet air temperature and inlet air velocities that reduce water losses. Particularly, the study is focused on the assessment of water losses caused by evaporation, as well as to determine the suitable size of water droplets for reducing water losses caused by drift. The mathematical model includes improvements to represent in a more realistic manner the heat and mass transfer mechanisms. One of these improvements is related to the convective heat transfer coefficient that for this study varies according to the temperature as well as to the instantaneous velocities of the continuous and dispersed phases. The results shows that the amount of mass evaporated for particles of 1 mm in diameter was around 1.2% of the total droplet's mass. On the contrary, for particles of 8 mm that percentage was around 1% for the same residence time. Results also indicate that the minimum diameter of water droplets should be higher than 3 mm and air velocities lower than 5 m/s, in order to avoid drifting.
Water drift emitted from cooling towers is objectionable for several reasons, mainly due to human health hazards. A numerical model to study the influence of psychrometric ambient conditions on cooling tower drift deposition was developed as a tool to evaluate liquid droplet dispersion and risk area. Both experimental plume performance and drift deposition were employed to validate the numerical results. This study shows the influence of variables like ambient dry bulb temperature, ambient absolute humidity and droplet exit temperature from cooling tower on the drift evaporation (and therefore deposition) and on the zone affected by the cooling tower. The strongest effect detected corresponds to the ambient dry bulb temperature. When a higher ambient temperature was present, deposition was lower (evaporation was therefore higher) and the zone affected by the cooling tower was smaller. The influence of the other two variables included in the study was weaker than the dry bulb ambient temperature. A high level of ambient absolute humidity increased drift deposition and also the size of the zone affected by the cooling tower. Finally, a high level of droplet exit temperature decreased deposition and increased the zone affected by the cooling tower.
JesúsPacheco Ibarra Carlos Rubio-Maya 2018 Numerical study of the drift and evaporation of water droplets cooled down by a forced stream of air Applied Thermal Engineering
- Oskar Javier Gonzá Lez Pedrazaj
Oskar Javier Gonzá lez PedrazaJ, JesúsPacheco Ibarra Carlos Rubio-Maya 2018 Numerical study of the drift and evaporation of water droplets cooled down by a forced stream of air Applied Thermal Engineering 142 292-302
A accurate measurement method for water loss of cooling tower
- Song
Baohong Song. (2019) A accurate measurement method for water loss of cooling tower. [P] Chinese patent. CN 2019104830076.
Test Study of Water Loss of Cooling Tower on U - Type Liquidometer
- Song
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Source: https://www.researchgate.net/publication/343010331_Specification_for_water_balance_test_of_cooling_towers
