EPA-660/2-75-027
JUNE 1975
Environmental Protection Technology Series
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
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1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES series. This series describes research
performed to develop and demonstrate instrumentation, equipment
and methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
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EPA-660/2-75-027
JUNE 1975
TURBULENT BED COOLING TOWER
By
Ronald G. Barile
Purdue University
Lafayette, Indiana
Grant No. 801867
Program Element 1BB392
Project Officer
Dr. Mostafa A. Shirazi
Pacific Northwest Environmental Research Laboratory
National Environmental Research Center
Corvallis, Oregon 97330
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For Sale by the National Technical Information Service,
U.S. Department of Commerce, Springfield, VA 22151
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ABSTRACT
The purpose of this work is to determine whether the turbulent bed
contactor (TBC), a relatively new and efficient device commonly
used for gas scrubbing, can be proven as a competitive cooling
system in electric power generation. The turbulent bed employs
light, hollow plastic spheres as a packing which fluidize as
air flows upward through the bed, while water is sprayed downward
over the bed. It was desired to demonstrate the feasibility by col-
lecting sufficient data to permit scaleup design, and estimate
the investment and costs involved.
Pressure drop and cooling performance of the bed were measured
for the air-water system in a vertical column, 0.29 m. I.D. and
2.44 m. high, under conditions typical of industrial cooling
tower applications. It was found that the TBC performed margin-
ally as compared with conventional mechanical draft cooling towers,
requiring as much as twice the auxilliary power per unit cooling
load while the capital investment is likely to be less due to the
smaller height of the TBC.
This report was submitted in fulfillment of Grant No. 801867
by Purdue University, Lafayette, Indiana, under the sponsorship
of the Environmental Protection Agency. Work was completed as
of May, 1975.
n
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TABLE OF CONTENTS
Page
Acknowledgement 1v
Section
I Conclusions 1
II Recommendations 3
III Introduction 4
IV Equipment 10
V Results and Discussion 14
VI References 23
VII Glossary 26
VIII Appendix - New Results 28
111
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ACKNOWLEDGEMENT
Many creative and diligent students of Purdue University, School of
Chemical Engineering, are to be thanked for their contributions to this
work: Carlos Dierolf, Donald W. Meyer, David F. Strahorn, Jeffrey L.
Dengler, and Thomas A. Hertwig. In addition, appreciation is expressed
to Professors James Etzel and Henry Tucker who contributed the original
concept of a turbulent bed cooling tower. Finally, special recognition
is given to Dr. Mostafa A. Shirazi who patiently guided this work to
its conclusion.
iv
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SECTION I
CONCLUSIONS
1. The turbulent bed cooling tower (TBC) can accomplish water cooling
ranges within about one foot of packing (10-15 ft tower) which
normally require full-size mechanical draft towers, i.e., 30-50
feet high.
2. Comparison of the TBC with mechanical draft towers in terms of the
tower characteristic shows that the TBC at its best is equivalent
to conventional towers.
3. Comparison of the TBC with mechanical draft towers in terms of the
power ratio, the ratio of total auxiliary water-and air-moving power
to the cooling load, shows that conventional towers have about a
factor of 1.5 to 2 advantage (lower power ratio) as compared to the
TBC, but again, in some cases they are equivalent.
4. Compared to a mechanical draft tower in a given case:
a. The TBC appears to require more air power (due to the requirement
of fluidizing the spherical packing).
b. The TBC would require lower water pumping head (due to the
shorter tower required for a given range).
c. The TBC would require less capital investment (due to the
shorter tower, but similar basin area).
5. The TBC performance is close enough overall to conventional towers
so that it should be investigated for further developments. It
does provide an alternative cooling device with potentials equal
to or superior to mechanical induced draft cooling tower.
1
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6. The non-plugging characteristics of TBC allow its use for cooling
cycles with waste or highly saline waters.
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SECTION II
RECOMMENDATIONS
1. The key factor In improving the TBC is to reduce air pressure
drop, and as a result power ratio and operating costs. This
could be approached by:
a. Enlarging the spherical packing
b. Multiple staging of packing which would require less
packing for a given cooling range.
c. Other mobile packing innovations.
2. The TBC should be assessed in an optimization computer package
for power-generation cooling which includes turbine, condenser,
and cooling tower sizing as well as costing.
3. Economic evaluation of the TBC should be performed, especially
capital requirements.
4. A scaled-up version of the TBC, say 3-10 ft in diameter, would be of
great value in determining its potential to be a competitive
cooling tower.
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SECTION III
INTRODUCTION
SCOPE AND PURPOSE
This project was undertaken to show the feasibility of using the
turbulent bed contactor (TBC) as a cooling tower for application to
electric power generation. The scope included design, construction
and testing of a pilot-scale TBC and a warm water loop representing
the cooling water efflux from condensers in a power plant. Testing
consisted of measuring air pressure drop, cooling performance, and
limiting operating characteristics (e.g., flooding, slugging, etc.)
for conditions typical of industrial cooling towers. The results
were used in a preliminary analysis to specify operating conditions
for the comparison of the TBC with existing industrial cooling
towers especially the induced-draft, wet, cross-flow type.
GENERAL BACKGROUND
Turbulent bed contacting is a relatively new and highly effective
means of contacting gas and liquid streams. The process is
generally classified as three-phase, countercurrent flow. Operation
in a vertical column consists of a process liquor being sprayed
down through a bed where it contacts an upward flowing gas stream.
The action of the two streams is responsible for fluidizing the
low-density bed packing which is maintained in a highly turbulent
state. This turbulence is responsible for intimate mixing of the
two streams and for a high rate of transfer. Indeed, transfer
coefficients two orders of magnitude greater than those of
4
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1 2
conventional fixed bed operation have been reported.
Most applications of the turbulent bed contactor (TBC) have been as
absorbers or scrubbers. The non-plugging characteristic of this
contactor makes it suitable in handling streams containing particulate
matter, precipitates, algae, etc. Additionally, there is little
tendency for channelling and bypassing. Other less typical uses, e.g.,
dehumidification of a hot, wet air stream, suggest the possibility of
the cooling tower application.
Turbulent Bed Contactors
The first published account of a commercial turbulent bed contactor
appeared in 1959 and explained its use as a scrubber to remove
particulate matter from a dust laden gas. H.R. Douglas et al. made
pilot studies of the absorption of C02 in an alkaline process liquor
and S02 in NaOH and Mg(OH)2 solutions. The striking result of their
work was the large increase in flow rates possible and the increase
of two orders of magnitude in the overall mass transfer coefficients
both compared to conventional fixed bed towers. The authors attributed
the increased transfer to intimate mixing caused by turbulence which
minimized the large transfer resistance characteristic to packed
2
towers. W.J.M. Douglas studied the absorption of ammonia gas by water,
and mass and heat transfer in the dehumidification of a hot, wet air
2
stream. Liquid flow rates ranged from 2460 to 15,000 Ib/hr-ft and qas
2
rates from 1037 to 2040 Ib/hr-ft . The results indicated that dramatic
reductions in tower size would be possible in certain interphase trans-
port situations due to the high mass transfer rates observed.
Experiments by Chen and Douglas delineated important TBC characteristics
of holdup, minimum fluidizing velocity and liquid backmixing. Further
work by Douglas and coworkers has subsequently been reported in the
i,
7
5 6
areas of pressure drop, bed expansion, and hydrodynamic characteristics
including a pressure drop correlation.'
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Parallel studies on the turbulent bed appeared in the Russian
8-11
literature concurrently. Several papers reported " on studies aimed
at generalizing its characteristics and establishing design principles.
Pressure drop, holdup, bed height, and flow regimes were considered.
Much of the pressure-drop data were not applicable to the present
topic because a low-free-area base plate was used (34.5%). Such a
plate offered significant flow resistance, of the order of the bed
itself, and resulted in excessive pressure drop due to liquid holdup
and premature flooding. Pressure drop data were also measured with
a new variation, i.e. with the use of disc packing.
DESCRIPTION OF PHASES OF THE PROJECT
Initial results of the group at Purdue University were published in
12
detail by Meyer and later extended and summarized by Barile and
13
Meyer . Meyer's objective was to build the TBC system and take only
representative pressure drop data. In this initial attempt at construc-
tion, flow circulation and flooding in the plenum area, where the air
turned from horizontal to vertical, caused uncertainties in pressure
drop and column flooding measurements. Carefully designed turning
vanes fabricated from brass and an efficient downcomer plate added
below the base plate solved these problems. More accurate pressure and
flow data were then reported by Dengler in his study of cooling
performance. The latter was also extended and summarized by Barile,
Dengler, and Hertwig. Further comprehensive studies of pressure drop
is the topic of a Master's thesis by Hertwig. An overview of work
12-16
reported in ~ is the subject of the present document.
THEORY OF COOLING TOWERS
In the development of the theory, heat and mass balances are made
between the water and air streams and empirical rate equations are
written for mass and heat transfer. Important simplifications result
-------
in the development by introducing the Lewis relation and by using the
enthalpy potential as a driving force for heat transfer. The following
is a summary of the resulting equations as used here for data
interpretation.
Equation (1) may be used to express cooling tower performance
*I9
t LZ ..
r dtl ITaW
p Jt rV• • T1 (1)
where t. ^ anc' Vl = ^et anc* out^et water temperatures, respectively,°F
i. and i'G = the enthalpy of saturated air at the water
temperature, and the enthalpy of the bulk air,
respectively (BTU/lb-dry-air)
o
Ka = overall mass transfer coefficient (Ib/hr-ft )
V = packing depth (ft)
L = liquid flux (Ib/hr-ft2)
C = Specific heat of water (Btu/lb-°F)
The term KaV/L is called "tower characteristic" by Lichtenstein and
is used to enumerate tower performance. Tower characteristic is a
reflection of tower performance over a wide variety of possible
conditions. Its value 1s usually independent of ambient conditions.
The calculation of tower characteristic is made by numerical integration
of the left side of Equation (1).
By making appropriate substitutions, expressions for the number of
transfer units and height of a transfer unit may be found as follows:
= NTU (2)
= = HTU
where G = gas flux (Ib/hr-ft2).
-------
An air enthalpy versus water temperature plot, Figure 1, is convenient
18
for a graphic description of the cooling theory. Wood and Betts have
thoroughly explained the plot. The equilibrium line represents the
enthalpy of the saturated air surrounding each water droplet. The
operating line is a result of the heat balance between the two phases
and has a slope of L/G*. It is bounded by the inlet and outlet water
temperatures and is fixed at point A by the enthalpy of the inlet air.
The vertical distance between the equilibrium and operating lines
represents the enthalpy driving force. By comparison with Equation (1),
tower characteristic may be seen to be inversely related to the area
ABCD of Figure 1.
Chen and Douglas have shown that backmixing is a significant mechanism
of turbulent bed contacting. This deviation from countercurrent
contacting is not accounted for in the above theory and undoubtedly
causes uncertainty in the calculated tower characteristic. It is
difficult to make corrections due to the lack of data available, thus
the theory as presented is used as a first approximation in describing
the cooling process. Also, no correction was made to account for the
heat loss from the column.
The approach used in this study was one of parameter indentification
through experimentation. The parameters were suggested in part by
the theory. No a priori attempt was made to calculate column performance,
•'Assuming Cp=1.0 Btu/lb-°F for water, the true slope, C L/G, becomes L/G.
8
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mo.o-i
20.0
40-0 60-0 60.0 100-0 120.0
TEMPERflTURE IF)
1HQ.O
Figure 1. Air enthalpy versus water temperature.
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SECTION IV
EQUIPMENT
Barile and Meyer have previously presented a description of the
essential equipment used in this study.^ Details of the equipment
12-16
were published earlier. " The equipment can be considered in
terms of the water system,the air system, and the column. A diagram
of the process equipment is given in Figure 2. The main modification
12
after Meyer , causing a significant improvement in operating
characteristics, was the installation of curved vanes below the base
plate to effect a gradual and uniform straightening of air before
entering the column. As a result, uniform air flow was realized at the
bed entrance thus preventing bulk packing rotation, channeling, and
erroneous pressure drop data.
The water system consisted of a 646-liter (170 gal.) reservoir tank
filled with tap water, a feed pump, bypass, heat source, feed lines,
low and high range rotafoeters, 6 hose-type spray nozzles, a bottoms
pump, and a return line emptying back into the reservoir. The heat was
supplied by a wall mounted shell-and-tube heat exchanger using
building steam. Heated water from the exchanger was returned to the
reservoir and thoroughly mixed with the tank contents by the force of
the water returning in the bypass line. The capacitance effect of the
reservoir made hand control of the tower inlet hot water temperature
quite easy.
The air system was made up of a muffler box, blower and motor, orifice
metering device, and column feed line. Room air was used as the feed
to the bottom of the column. The column, which consisted of a
cylindrical plexiglass tube 0.29 m ID by 2.44 m in height, contained
10
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V
\
I \
C£
bl
_l
U.
U.
3
Z
\
8
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the packing,a supporting grid for the packing, and a 0.3 m flow
straightening section. At the base of the column was a 1.05 m. plenum
chamber used to separate water and air streams.
The supporting grid for the packing was a 22-gauge, metal plate with
1.15-cm. square perforations on 1.27-cm straight centers. It was
inserted into the column between the flanges connecting the column
to the plenum chamber. It was purposely selected to have a high
free-area, 82%, to "minimize" the effect of air pressure drop and
water holdup at the grid.
A mist eliminator was set on the top of the column to prevent
entrained water from escaping from the column. The eliminator was
made of sheet metal and heavy screen. It provided a zig-zag path
which entrapped most of the drift before it could escape from the
column.
Hollow plastic spheres were used in the column as packing material.
Two sizes of packing were used, 1.9 (polyethylene) and 3.3 cm
(polypropylene) in diameter. Individually the spheres weighed 1.0
and 4.5 gm., and their bulk densities were 0.149 and 0.0961 gm./cc,
respectively. Because of their low density the spheres were
relatively easily fluidized. The spheres were purchased from Ac-
Cello Products, Inc., New York, N.Y., at approximately $40.00/cu.ft.*
Measurements
Five process measurements were required as depicted in Figure 2.
1. Water and air dry bulb temperatures, inlet and outlet tower
conditions: copper-constantan thermocouples with stainless
steel sheathing.
2. Air wet-bulb temperatures, inlet and outlet: copper-
*In bulk, the price could be as low as $4.00/cu.ft., 1973 dollars.
12
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constantan thermocouples with stainless steel sheathing covered
with reservoir-fed wicks.
3. Water flow rate: rotameters
4. Air flow rate: orifice meter and inclined manometer
(calibrated with pi tot tube).
5. Air pressure drop in tower:water manometer, taps located
just below the base plate and adjacent to the water spray
nozzles. This measurement was corrected by subtracting from
it the pressure drop measured in the same way without any
packing in place and without water flowing. The correction,
never greater than about 0.2 cm water, was calculated from
the following:
-9 2
Pressure drop correction * 3.3 x 10 G , in,, water,
where G is measured in lb/hr-ft^.
13
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SECTION V
RESULTS AND DISCUSSION
The measured tower character!sticjKaV/L are shown in Figure 3 for
d = 3.8 cm and packing depth equal to or less than the pipe diameter.
Three levels of flow are presented, i.e. L x G values, as well as
the amount of cooling with no packing present. These data for d =
3.8 cm are presented instead of for d = 1.9 cm because of smaller
pressure drop associated with the larger particles. A series of
measurements for packing depths V > 30.5cm were omitted in this
summary report due to their questionable use.
It is clear from Figure 3 that tower character!sticsimprove with
increased packing depth, but the incremental improvement appears to
diminish. Also, there is a consistent trend of higher KaV/L at lower
flow levels.
In order to gain some idea of the relative performance of the turbulent
bed contactor as a cooling device, comparisons are made with large
Marley mechanical draft towersin terms of the same scaling parameter
iq
KaV/L calculated from basic data presented in a Marley report.
More discussion of this comparison will be given later.
A summary of the pertinent measured data on the turbulent bed contactor
together with related calculations on Mauley's towers are presented
in Tables 1 and 2, respectively. Even though considerably more data
were available from Dengler, a limited selection was made with the
objective of presenting as meaningful a comparison of the TBC
14
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51.0
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FLOW LEVEL= L xG , (LB/HR-FT2)2
4.9 x I06
9.1 x I06
16.7 x I06
MARLEY
TOWERS,
COMPARABLE
CONDITIONS
Vo=30.5cm
V0= 15.2cm
V0=0
" 0.4 0.6 0.8 1.0 2.0 4.0 6.0
L/G, WATER TO AIR FLOW RATIO
Figure 3. Tower characteristic vs. L/G.
15
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performance with mechanical draft tower performance as possible. Repre-
sentative performance characteristics are presented to enable
relative operating cost comparison of the TBC with mechanical draft
towers. It is anticipated that the capital cost of TBC's will be
smaller than conventional towers due to the smaller height of the TBC
required to handle a given cooling load. However, no data can be
produced at this time to justify this claim.
The entries in Tables 1 & 2 must be explained in order to gain under-
standing of the performance comparisons. In Table 1, the columns
indicate the run number, the static packing depth ,V, the tower
characteristic, KaV/L, liquid to gas mass flow ratio, L/G, and the
cooling load,all self explanatory. The corrected pressure drop AP
does not include the wall effects of the tower as discussed earlier.
This pressure drop was converted into equivalent thermal energy for
delivering the air through the TBC. It is contained in the last
column as the ratio of the total auxiliary power, i.e., the power
delivered to the air and water, divided by the cooling load. The
water pumping power was calculated for4.6mwater injection level for
85% efficiency. No fan efficiency was included,i.e. r^ was assumed 1.0.
Therefore the auxiliary power is optimistically underestimated, a point
not to be overlooked when comparing TBC data with Marley's. As a
rough estimate of this difficiency, it should be noted that the water
pumping power represented nearly 20-30% of the total auxiliary power.
Therefore, the data can be adjusted accordingly when the fan efficiency
becomes available. The power ratio is presented as a percentage level
as the quantity of auxiliary power required to reject a unit power
(thermal energy/time) as waste.
In Table 2 the tower characteristics were obtained from a numerical
19
integration based on Marley's data of selected job number cases.
The fan BHP was used directly, and the water pumping power was cal-
culated for 9.1 m injection height at 85% assumed pumping efficiency.
19
-------
It is apparent from the comparisons of the power ratios presented 1n
Table 1 to those in Table 2 that the TBC when taken at its best
appears equal in performance to the mechanical draft towers. The
majority of the data show that pressure drop per unit of cooling load
through a TBG is twice that of mechanical draft towers. It must be
mentioned that the mechanical draft towers of reference 19 were optimized
as an integral part of a power generation system to produce power at
least cost. Similar optimization of the TBC would result in a balanced
performance vs. capital cost and might appear competitive despite the
apparent performance disadvantage.
DISCUSSION
A primary concern in assessing the turbulent bed cooling tower is
to compare it with acceptable towers already being used. Although there
appears to be no parameter which reduces all variables to a common basis,
the tower characteristic gives one widely recognized basis for
comparison. Figure 3 demonstrates that industrial mechanical draft
towers exhibit characteristics approximately 1.5 to 2 times as large
as the TBC for one stage packing and 106°F inlet water temperature.
However, note in Tables 1 and 2 that the comparison is more favorable
for eases with similar inlet air wet bulb temperatures and inlet
water temperature. Only the latter type cases are shown on this
figure for Marley towers. Of course, the influence of both these
temperatures are included in the tower characteristic but there appears
to be some interaction of effects that is not eliminated by using tower
characteristic. More questionable is the factor of V (bed height) in
the characteristic since conventional vs. TBC towers would have fill or
packing ratios of about forty to one. Thus, comparing tower character-
istics may not be a critical variable for discriminating between grossly
different tower designs but it is useful for crude screening.
20
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A second parameter for comparison is introduced above*:
nru.m nnrm (fan + water) power input „ lnn
POWER RATIO = - r.^-iiJ,. *n*A—— x IUU
— x 100
tfc Qair/nf+ZgWl
-i- _
W, C AT,
L p L
where
AP = corrected bed pressure drop
nf = fan efficiency
Q_. = air flow, SCFM
U I i
AT. = water cooling range
Z = water injection height
g = gravity acceleration
W, = water mass rate
n = pump efficiency
C = water heat capacity
This ratio appears to be better than the tower characteristic in
demonstrating a fair comparison between different towers, yet it does
not distinguish between favorable and poor ambient conditions or
differences in inlet-water temperature. Generally, low inlet-air wet
bulb and high inlet-water temperatures cause tower performance to look
good in terms of both tower characteristic and power ratio. However,
for a case with similar inlet temperatures, the tower with a lower power
ratio is desired if their capital costs are equal; or, the tower with
lower capital cost is desired if their power ratios are equal. At this
writing, it appears that the conventional mechanical draft tower, as
represented by Marley case studies, is slightly more, favorable in power
ratio,and the TBC may be more favorable in capital cost. As noted
*Suggested by M. Shirazi, EPA project coordinator at Corvallis, Oregon.
21
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above, further optimization of case studies would probably make the TBC
appear more favorable. In addition, if there are any breakthroughs in
reducing auxiliary air power in the TBC, this entire conclusion could
change substantially. It is in this direction that further work is
proceeding.
22
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SECTION VI
REFERENCES
1. Douglas, H.R., 1.1-!.A. Snider, and G.H. Tomlinson. II. The
Turbulent Contact Absorber, Chem. Enq. Progr. 59; 85-89,
December 1963.
2. Douglas, W.J.M. Keat and Mass Transfer in a Turbulent Bed
Contactor. Chem Eng. Progr. 60; 66-71, July 1964.
3. New Floating Bed Scrubber Won't Plug. Chem. Eng. 66; 106,
December 14, 1959.
4. Chen, B.H., and W.J.M. Douglas. Liquid Holdup and Minimum Fluidi-
zation Velocity in a Turbulent Contactor. Can. J. Chem. Eng. 46:
245-249, August 1968. ~
5. Tichy, J., A. Wong, and W.J.M. Douglas. Pressure Drop in a Mobile-
Bed Contactor. Can. J. Chem. Eng. 50_: 215-220, 1972.
6. Tichy, J., and W.J.M. Douglas. Bed Expansion in a Mobile-Bed
Contactor. Can. J. Chem. Eng. 50: 702-707, 1972.
7. Tichy, J., and W.J.M. Douglas. Certain Characteristics of the
Mobile-Bed Contactors. Can. J. Chem. Eng. 51_: 618-620, October 1973.
8. Balabekov, O.S., P.G. Romankov, E. Ya. Tarat, and M.F. Mikhalev.
Operating Conditions of Columns with Wetted Moving Spherical
Packing. Zhur Prikladnoi Khimii. 42_: 1540-1547., July 1969.
23
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9. Gel1 perl n, N.I., V.Z. Grishko, V.I. Savchenko, and V.M. Shchedro.
Investigation of the Operation of Absorption Apparatus with a
Refluxed Ball Packing Type of Pseudoliquified Layer. Khimich
Neft. Mashin. 1: 22-26, January 1966.
10. Gel'perin, N.I., V.I. Savchenko, and V.Z, Grishko. Several
Hydrodynamic Working Principles of Absorption Apparatuses with
Fluidized Spherical Packing. Teoret Osnovy Khimich Tech. II.
1 (66): 76-83, 1968.
11. Levsh, I.P., N.I. Krainev, and M.I. Niyazov. The Calculation of
Hydraulic Resistances and Height of a Three Phase Fluidized Bed.
Uzbek Khimich Zhur. 5_ (72): 72-74, 1967.
12. Meyer, D.W. Hydraulics and Heat Transfer in a Turbulent Bed
Cooling Tower. Purdue University. Master of Science Thesis.
June 1971, 113 p.
13. Barile, R.G., and D.W. Meyer. Turbulent Bed Cooling Tower, Chem.
Eng. Progr. Symp. Ser. 67, (119): 134-143, 1971.
14. Dengler, J.L. Heat and Mass Transfer in a Turbulent Bed Cooling
Tower. Purdue University. Master of Science Thesis. June 1971. 153 p,
15. Barile, R.G., J.L. Dengler, and T.A. Hertwig. Performance and
Design of a Turbulent Bed Cooling Tower. AIChE Symposium Series.
70 (138): 154-162, 1974.
16. Hertwig, T.A. Pressure Drop in a Three-Phase Fluidized Bed
Suitable for Use as a Turbulent Bed Cooling Tower. Purdue University.
Master of Science Thesis. May 1974. 124 p.
17. Lichtenstein, J. Performance and Selection of Mechanical Draft
Cooling Towers. Trans. Am. Soc. Mech. Eng. 65_: 779-787,
October 1943.
24
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18, Wood, B., and P, Betts, A Temperature-Total Heat Diagram for
Cooling Tower Calculations. The Engineer (London). 189: 337-339,
March 1950.
19. Dickey, J.B., Jr., and R.E. Gates. Managing Waste Heat with the
Water Cooling Tower, 2nd Ed. The Marley Co. Mission, Kansas.
April 1973. 26 p.
20. Mostafa A. Shirzai, U.S. Environmental Protection Agency, Corvallis,
Oregon, private communication, May 1975.
25
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SECTION VII
GLOSSARY
Backmlxing - Axial mixing of a fluid in the reverse direction relative
to the bulk fluid direction.
Flooding - A condition in a vertical tower in which water can not
pass down through the tower and begins to form a pool at the bottom.
Fluidized (Bed) - Solid particles, held in a column by a screen,
which become suspended or mobile (as a liquid) due to air (friction)
passing through the particles.
Height of a Transfer Unit - Defined by Equation (3), inversely
proportional to good cooling performance.
Minimum Fluidizing Velocity - The air velocity which provides just
enough friction to make a bed of particles become fluidized.
Number of Transfer Units - Defined by Equation (2), increasing as the
tower load increases.
Plenum (Chamber) - Any section of a tower or column situated just
below the packing or fill area. Usually air-water disengaging occurs
here.
Slugging. - A condition of flow within a fluidized bed where large
portions of the packing (across the entire cross-section) move upward
26
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together, I.e. non-random particle motion.
TBC - Turbulent bed contactor as applied to the task of cooling
water.
27
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SECTION VIII
APPENDIX
NEW RESULTS
At the time of this writing, new experiments are being performed which
show improved performance in the TBC. Two stages of particles,
separated by 0.81 m vertical space with each stage having 7.6 cm. (or
15.2 cm.) of 3.4 cm spheres, have exhibited substantially increased
tower characteristics. Also, certain changes in the spheres appear
to have lowered pressure drop by 10 to 20% while fractionally enlarging
the cooling range. These results will be reported at a later date.
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TECHNICAL REPORT DATA
(I'lrase read Instructions on the reverse before completing)
I. RLPORT NO.
EPA-660/2-75-027
3. RECIPIENT'S ACCESSIOI»NO.
4, TITLE AND SUBTITLE
Turbulent Bed Cooling Tower
5. REPORT DATE
Mav 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ronald G. Barile
8. PERFORMING ORGANIZATION REPORT NO,
NA
9. PERFORMING ORG "VNIZATION NAME AND ADDRESS
School of Chemical Engineering
Purdue University
West Lafayette, Indiana 47907
10. PROGRAM ELEMENT NO.
1BB392
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
National Thermal Pollution Research Program
National Environmental Research Center
Con/all is, Oregon 97330
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The purpose of this work is to determine whether the turbulent bed contactor
(TBC), a relatively new and efficient device commonly used for gas scrubbing,
can be proven as a competitive cooling system in electric power generation.
The turbulent bed employs light, hollow plastic spheres as a packing which
fluidize as air flows upward through the bed, while water is sprayed downward
over the bed. It was desired to demonstrate the feasibility, collect sufficient
data to permit scaleup design, and estimate the investment and costs involved.
Pressure drop and cooling performance of the bed were measured for the air-
water system in a vertical column, 0.29 m. I.D. and 2.44 m. high, under condi-
tions typical of industrial cooling tower applications. It was found that
the TBC performed marginally as compared with conventional mechanical draft
Cooling towers, requiring as much as twice the auxilliary power per unit
cooling load while the capital investment is likely to be less due to the
smaller height of the TBC.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
*Turbulent bed
*Cooling tower
*Thermal pollution
Particles
Electric power plant
*Water cooling
Power cost
Capital
*Mechanical-draft
Feasibility
Thermal pollution
control
Cooling tower innova-
tion
Mobile-particle fill
c. COSATI Field/Group
18. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS /]
21. NO. OF PAGES
Unclassified
(This page)
22.TRICE
EPA Form 2220-1 (9-73)
ft U. S GOVERNMENT PRINTING OFFICE 1975-699-138 121 REGION 10
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