U.S. patent application number 15/261321 was filed with the patent office on 2017-03-16 for water minimizing method and apparatus for use with evaporative cooling devices.
The applicant listed for this patent is Munters Corporation. Invention is credited to Paul A. Dinnage.
Application Number | 20170074553 15/261321 |
Document ID | / |
Family ID | 58237681 |
Filed Date | 2017-03-16 |
United States Patent
Application |
20170074553 |
Kind Code |
A1 |
Dinnage; Paul A. |
March 16, 2017 |
WATER MINIMIZING METHOD AND APPARATUS FOR USE WITH EVAPORATIVE
COOLING DEVICES
Abstract
An evaporative cooling system includes a primary cooling unit
that utilizes a cooling fluid flowing through a primary heat
exchange medium to cool supply air flowing past the primary heat
exchange medium, a bleed line and a secondary cooling unit disposed
upstream of the primary cooling unit with respect to a flow
direction of the supply air. The primary cooling unit includes a
supply line for supplying the cooling fluid to the primary heat
exchange medium, a reservoir for collecting the cooling fluid
supplied to the primary heat exchange medium, and a pump for
recirculating the cooling fluid collected in the reservoir back to
the supply line. The bleed line bleeds a portion of the
recirculating cooling fluid from the primary cooling unit. The
secondary cooling unit includes a secondary heat exchange medium
that receives the cooling fluid bled from the primary cooling unit
through the bleed line. By either pumping or wicking, any excess
bleed fluid is refed to the secondary heat exchange medium, or
directed to a tertiary heat exchange medium, to enable complete
evaporation of the bled fluid.
Inventors: |
Dinnage; Paul A.; (New
Braunfels, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Munters Corporation |
Selma |
TX |
US |
|
|
Family ID: |
58237681 |
Appl. No.: |
15/261321 |
Filed: |
September 9, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62216883 |
Sep 10, 2015 |
|
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15261321 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 25/02 20130101;
F28D 5/02 20130101; F25B 49/00 20130101; F28C 1/14 20130101; F28D
5/00 20130101; F24F 5/0035 20130101 |
International
Class: |
F25B 19/00 20060101
F25B019/00; F25B 41/04 20060101 F25B041/04; F25B 49/00 20060101
F25B049/00; F25B 19/02 20060101 F25B019/02 |
Claims
1. An evaporative cooling system comprising: a primary cooling unit
that utilizes a cooling fluid flowing through a primary heat
exchange medium to cool supply air flowing past the primary heat
exchange medium, the primary cooling unit including a supply line
for supplying the cooling fluid to the primary heat exchange
medium, a return reservoir for collecting the cooling fluid
supplied to the primary heat exchange medium, and a pump for
recirculating the cooling fluid collected in the reservoir back to
the supply line; a bleed line configured to bleed a portion of the
recirculating cooling fluid from the primary cooling unit; and a
secondary cooling unit disposed upstream of the primary cooling
unit with respect to a flow direction of the supply air, the
secondary cooling unit comprising a secondary heat exchange medium
configured to receive the cooling fluid bled from the primary
cooling unit through the bleed line, wherein any excess bleed
cooling fluid that is not completely evaporated by the secondary
heat exchange media is directed to a heat exchange medium for
further evaporation.
2. The evaporative cooling system according to claim 1, wherein the
primary cooling unit comprises a direct evaporative cooler.
3. The evaporative cooling system according to claim 1, wherein the
primary cooling unit comprises an indirect evaporative cooler.
4. The evaporative cooling system according to claim 1, wherein the
secondary heat exchange medium comprises evaporative cooling
media.
5. The evaporative cooling system according to claim 1, wherein the
secondary heat exchange medium is of modular form, with each module
of the secondary heat exchange medium being individually
replaceable.
6. The evaporative cooling system according to claim 1, further
comprising a controller for controlling the magnitude of the
portion of the recirculating cooling fluid bled from the primary
cooling unit.
7. The evaporative cooling system according to claim 6, wherein the
controller senses a condition of the recirculated water and
accordingly controls the magnitude of the portion of the
recirculating cooling fluid bled from the primary cooling unit.
8. The evaporative cooling system according to claim 1, wherein the
excess bleed cooling fluid is redirected to the secondary heat
exchange medium by wicking or pumping.
9. The evaporative cooling system according to claim 8, wherein the
secondary heat exchange medium is positioned in a drain pan so that
any excess recirculating cooling fluid from the secondary heat
exchange medium is captured in the drain pan and maintains contact
with a lower edge of the secondary heat exchange medium.
10. The evaporative cooling system according to claim 8, wherein
the secondary heat exchange medium is positioned in a sump so that
any excess recirculating cooling fluid from the second heat
exchange medium is captured in the sump and pumped back to the
secondary heat exchange medium.
11. The evaporative cooling system according to claim 1, further
comprising auxiliary evaporative cooling media, wherein any excess
recirculating cooling fluid from the secondary heat exchange medium
is directed to the auxiliary evaporative cooling media.
12. A gas conditioning system comprising: a primary conditioning
unit configured to condition a gas flowing therethrough, the
primary conditioning unit utilizing a conditioning fluid to
condition the flowing gas; a bleed line configured to bleed a
portion of the conditioning fluid from the primary conditioning
unit; and a secondary conditioning unit disposed upstream of the
primary conditioning unit with respect to a flow direction of the
gas, the secondary conditioning unit utilizing the conditioning
fluid bled from the primary conditioning unit through the bleed
line to pre-condition the flowing gas, wherein any excess bleed
water that is not completely evaporated by the secondary
conditioning unit is directed to a conditioning unit for further
evaporation.
13. The gas conditioning system according to claim 12, wherein the
primary conditioning unit comprises a direct evaporative
cooler.
14. The gas conditioning system according to claim 12, wherein the
primary conditioning unit comprises an indirect evaporative
cooler.
15. The gas conditioning system according to claim 12, wherein the
secondary conditioning unit pre-conditions the flowing gas by
cooling the flowing gas via evaporative cooling media that uses the
conditioning fluid received through the bleed line.
16. The gas conditioning system according to claim 12, wherein the
conditioning fluid is recirculated through the primary conditioning
unit and the bleed line bleeds the portion of the recirculating
conditioning fluid from the primary conditioning unit.
17. The gas conditioning system according to claim 12, further
comprising a controller for controlling the magnitude of the
portion of the recirculating conditioning fluid bled from the
primary conditioning unit.
18. The gas conditioning system according to claim 12, wherein the
excess bleed conditioning fluid is redirected to the secondary
conditioning unit by wicking or pumping.
19. The gas conditioning system according to claim 18, wherein the
secondary conditioning unit is positioned in a drain pan so that
any excess recirculating conditioning fluid from the secondary
conditioning unit is captured in the drain pan and maintains
contact with a lower edge of the secondary conditioning unit.
20. The gas conditioning system according to claim 18, wherein the
secondary conditioning unit is positioned in a sump so that any
excess recirculating conditioning fluid from the second
conditioning unit is captured in the sump and pumped back to the
secondary conditioning unit.
21. The gas conditioning system according to claim 12, further
comprising an auxiliary conditioning unit, wherein any excess
recirculating conditioning fluid from the secondary conditioning
unit is directed to the auxiliary conditioning unit.
22. A method of cooling supply air in an evaporative cooling
system, the method comprising: supplying cooling fluid to a primary
evaporative heat exchange medium; bleeding a portion of the cooling
fluid supplied to the primary evaporative heat exchange medium;
supplying the bled cooling fluid to a secondary evaporative heat
exchange medium; flowing the supply air through the primary
evaporative heat exchange medium and the secondary evaporative heat
exchange medium; and directing any excess bleed cooling fluid that
is not completely evaporated by the secondary heat exchange media
to a heat exchange medium for further evaporation.
23. The method according to claim 22, wherein the excess bleed
cooling fluid is redirected to the secondary heat exchange medium
by wicking or pumping.
24. The method according to claim 23, further comprising capturing
the excess bleed cooling fluid in a drain pan and maintaining the
excess bleed cooling fluid in contact with a lower edge of the
secondary heat exchange medium.
25. The method according to claim 23, further comprising capturing
the excess recirculating cooling fluid from the second heat
exchange medium in a sump and pumping the excess recirculating
cooling fluid back to the secondary heat exchange medium.
26. The method according to claim 22, further comprising directing
the excess recirculating cooling fluid from the secondary heat
exchange medium to auxiliary evaporative cooling media.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/216,883, filed Sep. 10, 2015.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to improvements in
evaporative cooling systems, conditioning systems that utilize
thermodynamic laws to cool a fluid. Namely, a change of a fluid
from a liquid phase to a vapor phase can result in a reduction in
temperature due to the heat of vaporization involved in the phase
change.
[0004] 2. Related Background Art
[0005] In a typical evaporative cooler, raw water is supplied to or
recirculated through a heat exchanger and is vaporized by
extracting heat from supply air flowing through the heat exchanger.
Most readily available forms of raw water include various
contaminants, most notably dissolved salts and minerals. In a
recirculating evaporative cooling system, excess water supplied to
the heat exchanger that has not evaporated is collected in a
reservoir and then pumped back to the heat exchanger. As the water
evaporates from heat exchange, minerals and salts dissolved in the
raw water remain, building in concentration as the water volume
decreases. Make-up water is supplied to the system to compensate
for the evaporated water, but the salts and minerals remain and can
become deposited on the heat exchanger as scalants if the
concentration is too high.
[0006] In order to alleviate high concentrations of scalants, most
evaporative cooling devices that use water incorporate a water
bleed to drain to control salt and mineral content in the
reservoir. The techniques to determine an effective amount of bleed
are varied and well-known. In general, the amount of bleed is
dependent on the level of mineral contamination in the feed water
and water chemistry, but varies from as low as about 10% of the
feed water for very fresh water to as much as 50% or more of the
feed water where mineral content is high. Even where chemical
treatment is utilized to extend solubility of the minerals, bleed
is still required to replace water saturated with minerals with
fresh water to prevent scaling within the evaporative process.
[0007] FIG. 3 represents a schematic of a typical direct
evaporative cooler 100. Water or another suitable cooling liquid is
recirculated from a reservoir 110 through a supply line 112 to a
distributor 116 using a pump 114. Distributor 116 evenly
distributes the supplied water over a heat exchanger, such as
evaporative pad 118. Supply air 124 is passed through the pad,
where it is cooled and humidified to exit as cooled air 126. The
water fed from distributor 16 flows down and through the pad and
evaporates as it meets the warm supply air 124. A bleed stream
controlled by valve 120, for example, is removed from the system
through bleed or drain line 121 to drain 122 to control mineral
build-up in the water. Fresh make-up water is added as needed from
water supply 128 to replace the water evaporated and bled. The
make-up water can be controlled by a float valve or other level
sensing device (not shown) provided in the reservoir 110.
[0008] FIG. 4 depicts a typical indirect evaporative cooler, in
this instance a fluid cooler 200. Fluid cooler 200 includes a
housing 202 having air inlets 204 and an air outlet 206. A sump 210
that functions as a reservoir is disposed at the bottom of housing
202. A heat exchanger 218, having a fluid inlet 218-1 and a fluid
outlet 218-2, is disposed above sump 210. Water or another suitable
coolant is drawn from sump 210 through supply line 212 using a pump
214. The pumped water is supplied to a spray head 216, which sprays
the water over heat exchanger 218 so as to draw heat from the heat
exchanger. The sprayed water is collected in the sump 210. As in
the direct evaporative cooler, in order to control the
concentration of salts and minerals in the cooling water, a bleed
valve 220 is provided in supply line 212 in order to bleed off
cooling water through bleed line 221 to drain 222. Air is drawn
through air inlets 204 and out air outlet 206 using a fan 230
driven by a motor 232 via a belt. The fluid to be cooled is
supplied to heat exchanger 218 through inlet 218-1 and discharged
through outlet 218-2.
[0009] In operation, as shown in FIG. 4, cool air 226 is first
passed over the outer surface of heat exchanger 218, through which
flows a hot fluid to be cooled. The fluid to be cooled may be a
liquid such as water, or a gas, such as air. The heat exchanger 218
is sprayed with a recirculated water stream using supply line 212,
pump 214 and spray head 216 and an air stream is simultaneously
generated to flow over the wet exchanger surface to evaporate water
and produce cooling of the primary fluid inside the heat exchanger.
As in the case in the direct evaporative system, a bleed or water
from the recirculation sump is required to prevent mineral
build-up. Make-up water is added from supply 228 to replenish the
evaporated and bled water.
[0010] In both the direct and indirect evaporative cooling systems,
the bled water is directed to drain and is otherwise not used. Such
can result in substantial waste of cooling water. This waste can
significantly increase the cost of operating the system, present a
negative public image of the operator, and also place a significant
burden on water supplies, particularly in areas where fresh water
is scarce.
SUMMARY OF THE INVENTION
[0011] The present invention can improve the efficiency and
effectiveness of evaporative cooling systems by utilizing bleed off
cooling water in a supplemental cooling process.
[0012] The present invention can utilize the bleed water to provide
a portion of the evaporative work and reduce the water lost to
drain and thus the total amount of water consumed by the
evaporative cooling system.
[0013] The present invention can provide an alternative to water
pre-treatment or chemical treatment as a means of reducing bleed
water requirements and thus total water usage. It may be used alone
or in conjunction with other techniques.
[0014] In one aspect of the present invention, an evaporative
cooling system includes a primary cooling unit that utilizes a
cooling fluid flowing through a primary heat exchange medium to
cool supply air flowing past the primary heat exchange medium, a
bleed line and a secondary cooling unit disposed upstream of the
primary cooling unit with respect to a flow direction of the supply
air. The primary cooling unit includes a supply line for supplying
the cooling fluid to the primary heat exchange medium, a return
reservoir for collecting the cooling fluid supplied to the primary
heat exchange medium, and a pump for recirculating the cooling
fluid collected in the reservoir back to the supply line. The bleed
line is configured to bleed a portion of the recirculating cooling
fluid from the primary cooling unit. The secondary cooling unit
includes a secondary heat exchange medium configured to receive the
cooling fluid bled from the primary cooling unit through the bleed
line, and any excess bleed cooling fluid that is not completely
evaporated by the secondary heat exchange media is directed to a
heat exchange medium for further evaporation.
[0015] In another aspect of the present invention, a gas
conditioning system includes a primary conditioning unit, a bleed
line and a secondary conditioning unit. The primary conditioning
unit is configured to condition a gas flowing therethrough, and
utilizes a conditioning fluid to condition the flowing gas. The
bleed line is configured to bleed a portion of the conditioning
fluid from the primary conditioning unit. The secondary
conditioning unit is disposed upstream of the primary conditioning
unit with respect to a flow direction of the gas, and utilizes the
conditioning fluid bled from the primary conditioning unit through
the bleed line to pre-condition the flowing gas, and any excess
bleed water that is not completely evaporated by the secondary
conditioning unit is directed to a conditioning unit for further
evaporation.
[0016] In yet another aspect of the present invention, a method of
cooling supply air in an evaporative cooling system includes
supplying cooling fluid to a primary heat exchange medium; bleeding
a portion of the cooling fluid supplied to the primary heat
exchange medium; supplying the bled cooling fluid to a secondary
heat exchange medium; flowing the supply air through the primary
heat exchange medium and the secondary heat exchange medium; and
directing any excess bleed cooling fluid that is not completely
evaporated by the secondary heat exchange media to a heat exchange
medium for further evaporation.
[0017] These and other aspects and advantages will become apparent
when the description below is read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic view of an evaporative cooling system
of a first embodiment of the present invention.
[0019] FIG. 2 is a perspective view of modified de-watering media
used in the present invention.
[0020] FIG. 3 is a schematic view of a typical direct evaporative
cooling system.
[0021] FIG. 4 is a schematic view of a typical indirect evaporative
cooling system.
[0022] FIG. 5 is schematic view of a second embodiment of the
present invention.
[0023] FIG. 6 is schematic view of a third embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] In a system of the present invention, the bleed water from
an evaporative cooler is utilized to cool the air entering an
evaporative section of a typical evaporative cooling system, such
as a system described above with respect to FIGS. 3 and 4. This is
accomplished by passing the bled water over dewatering media, or
mineral removal media (MRM), which is itself a direct evaporative
cooling section. The mineral removal media cools and humidifies the
air before entering a principal evaporative cooling process
described above.
[0025] The evaporative cooling device following the MRM media can
be of any type, including, as discussed above, the direct
evaporative type where water is evaporated into the air as a means
to cool the air and the indirect evaporative type where water is
evaporated into an air stream as a means to cool a third fluid
contained in a heat exchanger that is wetted in the evaporative
cooling zone, and even a cooling tower, where water is evaporated
to an air stream as a means to cool a water supply.
[0026] FIG. 1 is a schematic view of an evaporative cooling system
of a first embodiment of the present invention. Evaporative cooling
system 300 utilizes one of the typical direct or indirect
evaporative coolers described with respect to FIGS. 2 and 3, which
is used as a primary cooling apparatus. The selected primary
cooling apparatus is schematically shown by reference numerals 100,
200 in FIG. 1. As in the typical evaporative cooling apparatuses,
the system of the first embodiment of the present invention
includes a sump or reservoir 310, supply line 312, pump 314 and
distributor or spray head 316. These components are used to supply
water or another suitable cooling fluid to the primary evaporator
of the apparatus, that is, evaporative pad 118 or heat exchanger
218.
[0027] In order to lower the concentration of minerals and salts in
the cooling water, the system of the current embodiment utilizes a
bleed valve 320 and a bleed line 321 to bleed off a fraction of the
cooling water. By bleeding off a fraction of the cooling water, the
residual amount of minerals and salts in the cooling fluid can be
minimized, thereby preventing scale from developing on the primary
evaporative pad 118 or heat exchanger 218.
[0028] As in the typical evaporative cooling examples, in the
present embodiment, the cooling water flows down the primary
evaporative pad 118 or heat exchanger 218 and is collected in sump
310 to be recirculated by pump 314 back to the distributor or spray
head 316. As the water level in the sump decreases due to
evaporation and bleed off, make-up water can be supplied to sump or
reservoir 310 from water supply 328, which is controlled by a float
valve (not shown) or any other suitable device.
[0029] As noted above, the amount of bleed from supply line 312 is
determined by bleed valve 320. In the present embodiment, bleed
valve 320 is variable and controllable by a controller 330.
Controller 330 can be any suitable systems microcontroller. The
parameters of the bleed valve can be preset and adjusted according
to system conditions. As one example, a total dissolved solids
(TDS) meter or probe 332 can be provided somewhere in the
recirculating cooling water circuit, such as at the sump 310, to
determine the amount of dissolved solids in the cooling liquid. A
signal from TDS meter 332 to controller 330 can be analyzed so that
controller 330 controls bleed valve 320 to bleed a greater
percentage of cooling water as the amount of detected solids
increases.
[0030] Unlike the typical evaporative cooling systems of FIGS. 3
and 4, the water bled from supply line 312 into bleed line 321 does
not flow directly to drain 322. Rather, the bled water is fed from
bleed line 321 to auxiliary evaporative media or pad 340 via
distributor 342. Auxiliary evaporative media 340 can also be
referred to as dewatering media, sacrificial media, or mineral
removal media. Auxiliary evaporative media 340 is disposed upstream
of evaporative cooling apparatus 100, 200 with respect to the flow
of air to be cooled. Airflow 323 entering auxiliary evaporative
media 340 is cooled and humidified as airstream 324 that passes
through primary evaporative pad 118 or heat exchanger 218. Air that
flows through primary evaporative cooling apparatus 100, 200 is
further cooled and humidified in a principal evaporative cooling
process and exhausted as exhaust airflow 326. By precooling the air
using auxiliary evaporative media 340 before entering the primary
evaporative cooling process, bled water that would typically be
wasted to drain is used to pre-cool the air and allow for improved
efficiency and effectiveness of the evaporative cooling system.
[0031] The bleed water that passes over the mineral removal media
340 is reduced in volume and increases in mineral content as it
evaporates. As this occurs, scale will be deposited on the mineral
removal media 340. Depending on the setting of bleed valve 320, the
water volume may be reduced to zero through complete evaporation
before exiting mineral removal media 340. Any water that does not
evaporate and does pass completely through the mineral removal
media 340 is not returned to the sump, but directed to drain 322.
This residual water will have a very high mineral content, and will
have left behind a substantial amount of minerals and salts on the
evaporative media. As such, the media will eventually become heavy
with thickened and scaled walls and will need replacement or
cleaning.
[0032] In that regard, a disposable or cleanable, low-efficiency
evaporative cooling medium or pad 340 that pre-treats (pre-cools)
the air that enters the primary evaporative cooling device and is
wetted by the bleed water is preferred. The media is designed to be
disposable or cleanable as the minerals will deposit on the surface
as water evaporates. The openings in the media are designed with a
pore dimension large enough to compensate for the shrinking that
occurs as the scale build-up progresses.
[0033] Preferably, the wet bulb efficiency of the pre-treatment
media is selected so that the majority of all of the bleed water is
evaporated before it can leave the media. Depending on the ratio of
bleed water to make-up water in the evaporative cooling system, the
media wet bulb efficiency should be between about 10 and 50%; the
higher the bleed rate, the higher the required evaporative
efficiency.
[0034] It may not be practical to evaporate the water from the
sacrificial pad at all times. This could most notably be due not to
the sizing of the media, as described in detail below, but due to
transitional effects of the system wherein intermittently excess
water is applied to the sacrificial media and not all of it
evaporates. There could be many reasons for this. The most notable
reasons relate to the control system response time. Generally a
control system will bleed water based on the evaporation rate that
has occurred in the past. If, for example, the humidity of the air
rapidly increases to saturation the controller will still try to
bleed water to the sacrificial media but the air will have no
capacity to evaporate the water and remove the solids. Another
example is where the water distribution on the evaporative media is
not sufficiently homogeneous, possibly do to maintenance issues.
Under these conditions, areas with higher than design water
distribution flows may be not be able to completely evaporate the
flow, resulting in bleed break-through in areas of the media.
During these times, especially where the system has been designed
to completely evaporate the bleed water, it may be best to direct
the excess high mineral content water back to the main sump.
[0035] If this is done, additional precautions should be taken. If
the above situations exist for a sufficient period of time the
bleed itself will not be able to remove sufficient solids from the
recirculated system. The sacrificial pad may also start to act to
selectively remove lower solubility mineral salts, such and calcium
and silica based salts, while not precipitating out higher
solubility salts, such as sodium or chloride based salts, or other
contaminants in the water supply, which may be subject to
regulations relating to the maximum concentration possible to
discharge to a waste water stream.
[0036] An alternate approach is to collect any excess flow that is
not completely evaporated by the auxiliary media, and re-apply the
concentrated water solution to the MRM media. This can be effected
by another pump, or as the excess may be very intermittent and not
of large volume, a drain pan under the auxiliary media may be
designed to collect this excess flow and allow the MRM to act as a
wicking humidification media. In this arrangement, the excess
liquid may flow laterally to other sections of the MRM that are dry
at the lower edge, be wicked up by this media, and then be fully
evaporated. Alternately, additional media may be designed to act
solely as a wicking media for complete evaporation of this water.
This media may then be serviced at intervals separate from the
servicing of the auxiliary media. These alternatives are shown in
FIGS. 5 and 6.
[0037] In more detail, system 400 includes similar elements as in
the first embodiment, such as evaporative pad 118 (unless an
indirect evaporative cooler is used), sump 310, pump 314, bleed
valve 320, bleed line 321, and auxiliary evaporative media 340.
These components work similarly as in the first embodiment and will
not be described in detail here. The current embodiment also
includes drain pan 410, with or without a reapplication pump 412
(FIG. 5), or a modified drain pan 415 and wicking media 420 (FIG.
6). Drain pan 410 is positioned below auxiliary evaporative media
340 to collect any excess flow of the bleed water. If used as
wicking humidification media, auxiliary evaporative media 340 is
positioned so that its lower edge will sit in any accumulated
excess bleed water in drain pan 410 so that the accumulated water
can flow along the lower edge of media 340 to sections of that
media that may be dry. The dry sections will wick up the excess
water to effect total evaporation. If the collected water is to be
reapplied to the auxiliary evaporative media 340, reapplication
pump 412 is provided to pump the collected water back to the upper
edge, or any other appropriate location, of the auxiliary
evaporative media 340 through reapplication line 415. Pump 412 can
be activated by a float switch or any other appropriate device.
[0038] In the modification of FIG. 6, system 500 includes drain pan
510 provided to capture the excess liquid from auxiliary
evaporative media 340 and direct it to the lower edge of wicking
media 520. Wicking media 520 is positioned upstream of auxiliary
evaporative media 340 with respect to the airflow direction, but
can be designed with a smaller profile so as not to significantly
obstruct the airflow through the auxiliary evaporative media 340.
The excess water in drain pan 510 will be wicked by wicking media
520 so as to effect total evaporation. The wicking media 520 can be
made of the same material as the auxiliary evaporative media or any
of the other evaporative materials discussed herein. The modified
drain pan 510 is designed to guide the excess water from the
auxiliary evaporative media 340 to the lower edge of wicking media
520. This can be effected by providing upper and lower sections of
the drain pan, with the excess water being captured in the upper
section and flowing by gravity to the lower section where the
wicking media is positioned.
[0039] Referring back to the original embodiment, during times when
it is sensed that there is excess water exiting the auxiliary MRM
media, the primary bleed can be interrupted to ensure that complete
evaporation of the primary bleed water is accomplished.
[0040] In systems designed as such, to protect against build-up of
these highly soluble minerals, a secondary bleed system which
directs the water directly to drain may be fitted. This bleed
should be based on a second bleed criterion different from the
primary bleed described above. Examples of the control method would
be to operate the bleed in a traditional manner at times when the
TDS is above a second, higher concentration level, operate if the
primary bleed has not been able to respond and correct the TDS
concentration over a given period of time, or by sensing the
presence of the concentration of one of the highly soluble minerals
and bleeding to drain when it exceeds a determined threshold.
[0041] Cycles of concentration (CoC) is a measure that compares the
level of solids of the recirculating water to the level of solids
of the original raw make-up water. For example, if the circulating
water has four times the solids concentration than that of the
make-up water, then the cycles of concentration is 4. For a given
cycles of concentration, the preferred pre-treatment evaporative
cooler efficiency can be calculated. To illustrate this point, the
following tables outline evaporation rates and bleeds rates given a
system treating 1000 scfm of air with an evaporative media with an
85% efficiency rating.
[0042] Table 1 describes the air conditions as they change as the
air travels first from an inlet with conditions of 95.degree. F.
dry bulb and 75.degree. F. wet bulb through 85% efficiency
evaporative media. In this table there is no mineral removal pad so
the efficiency for that pad is given as 0%. In the table, the units
for airflow are both standard cubic feet per minute (scfm) and
pounds per hour (lbs/hr), the units for water flow are lbs/hr, the
units for humidity are grains per pound (grab), and the dry bulb
(db) and wet bulb (wb) temperatures are in degrees F.
TABLE-US-00001 TABLE 1 Example 1: Dewater Evap Efficiency = 0%
airflow 1000 scfm airflow 4500 lbs/hr Cycles of Concentration 2.2
Dewatering Pad Efficiency 0% Direct Evaporative efficiency 85%
Direct Inlet After Evap Air Dewater Cooler Notes db 95 95 78 wb 75
75.0 75 gr/lb 99.1 99.1 126.9 Water Evaporated (lbs/hr) 0.0 17.9
Bleed to Dewatering 14.9 Bleed = Evap Pad (lbs/hr) Rate/(CoC - 1)
Water To Drain (lbs/hr) 14.9 Resultant Cycles 2.2 (Evap Rate/Bleed
Rate) + 1
[0043] In the table above, Evaporative (Evap) efficiency or Wet
Bulb Efficiency is defined as (Temperature of the entering
air-temperature of the air exiting an adiabatic evaporative
exchanger)-(Temperature of the air entering-Web Bulb temperature of
the air entering). By common definition, the bleed rate for a
defined Cycles of Concentration can be calculated by the formula
Bleed=Evaporation Rate/(CoC-1). In the example above, the air is
cooled and humidified from 95.degree. F. db, 75.degree. F. wb, 99
gr/lb to 78.degree. F. db, 75.degree. F. wb and 127 gr/lb. The
evaporative cooling results in an evaporation of 17.9 lbs per hour.
In order to maintain the desired Cycles of Concentration at 2.2,
14.9 lbs/hr of water are required to be led to drain.
[0044] In a second example, the system is fitted with a mineral
removal pad with a 25% efficiency rating. The following table shows
the results of the air traveling through the system.
TABLE-US-00002 TABLE 2 Example 2: Dewater Evap Efficiency = 25%
airflow 1000 scfm airflow 4500 lbs/hr Cycles of Concentration 2.2
Dewatering Pad Efficiency 25% Direct Evaporative efficiency 85%
Direct Inlet After Evap Evap Efficiency Air Dewater Cooler Notes db
95 90 77.25 wb 75 75.0 75 gr/lb 99.1 107.2 128.1 Water Evaporated
(lbs/hr) 5.2 13.5 Bleed to Dewatering 11.2 Bleed = Evap Pad
(lbs/hr) Rate/(CoC - 1) Water To Drain (lbs/hr) 6.0 Resultant
Cycles 4.1 (Evap Rate/Bleed Rate) + 1
[0045] In this example, the air first is exposed to the dewatering
pad where its temperature is first reduced from 95.degree. F. to
90.degree. F. and its moisture increased from 99 gr/lb to 107 gr/lb
before it enters the primary direct evaporative cooling exchanger.
In the exchanger, its temperature and moisture are further reduced
to 77.degree. F. and 128 gr/lb. As the mineral removal pad has done
some of the evaporative cooling work, the amount of water
evaporated in the primary exchanger has been reduced from 17.9
lbs/hr to 13.5 lbs/hr. In order to maintain the primary exchanger
sump with a Cycles of Concentration of 2.2, 11.2 lbs/hr must be
bled. This water, however, does not go to drain, but is fed to the
mineral removal pad, where 5.2 lbs are evaporated. The remaining
6.0 lbs per hour are led to drain and the resultant CoC is
increased from 2.2 to 4.1.
[0046] In a third example, the mineral removal media efficiency is
further increased to 35%.
TABLE-US-00003 TABLE 3 Example 3: Dewater Evap Efficiency = 35%
airflow 1000 scfm airflow 4500 lbs/hr Cycles of Concentration 2.2
Dewatering Pad Efficiency 35% Direct Evaporative efficiency 85%
Direct Inlet After Evap Air Dewater Cooler Notes db 95 88 77 wb 75
75.0 75 gr/lb 99.1 110.5 128.6 Water Evaporated (lbs/hr) 7.3 11.7
Bleed to Dewatering 9.7 Bleed = Evap Pad (lbs/hr) Rate/(CoC - 1)
Water To Drain (lbs/hr) 2.4 Resultant Cycles 9.0 (Evap Rate/Bleed
Rate) + 1
[0047] In this example, by increasing the efficiency of the mineral
removal pad the evaporating rate from the primary exchanger is
further reduced to 11.7 lbs/hr resulting in a bleed to the mineral
removal media of 9.7 lbs/hr, of which 7.3 lbs are evaporated. The
remaining 2.4 lbs/hr of water which leaves the mineral removal
media and goes to drain represents a CoC of 9 for the net
evaporative cooler.
[0048] Taking the analysis to its conclusion, increasing the
mineral removal media evaporative efficiency to 42% results in no
water remaining to go to drain and a resultant CoC approaching
infinity.
TABLE-US-00004 TABLE 4 Example 4: Dewater Evap Efficiency = 42% -
Bleed evaporated airflow 1000 scfm airflow 4500 lbs/hr Cycles of
Concentration 2.2 Dewatering Pad Efficiency 41.65% Direct
Evaporative efficiency 85% Direct Inlet After Evap Evap Efficiency
Air Dewater Cooler Notes db 95 86.7 76.8 wb 75 75.0 75.0 gr/lb 99.1
112.7 129.0 Water Evaporated 8.7 10.5 (lbs/hr) Bleed to Dewatering
8.7 Bleed = Evap Pad (lbs/hr) Rate/(CoC - 1) Water To Drain 0.0
(lbs/hr) Resultant Cycles 1343615 (Evap Rate/Bleed Rate) + 1
[0049] As is shown by these examples, by adapting the mineral
removal efficiency to the CoC and the main evaporative load, the
pre-treat evaporation rate can be made to match the main evaporator
bleed rate. Alternatively, even higher efficiency media can be used
to ensure more or all the water is evaporated, but at a cost of
higher pressure drop and higher capital cost.
[0050] In the above examples, the total evaporative efficiency of
the system increased by the addition of increasingly efficient
mineral removal pads. Another approach is to reduce the efficiency
of the primary exchanger as the efficiency of the mineral removal
pad is increased. In the example below, the combination of a
mineral removal pad efficiency of 39% coupled with a primary
exchanger efficiency of 77% results in air being conditioned to
78.degree. F. db as in Example 1, but with no resultant bleed
water.
TABLE-US-00005 TABLE 5 Example 5: Netting of Total evap efficiency
to equal the initial design airflow 1000 scfm airflow 4500 lbs/hr
Cycles of Concentration 2.2 Dewatering Pad Efficiency 39% Direct
Evaporative efficiency 77% Direct Inlet After Evap Air Dewater
Cooler Notes db 95 87 78 wb 75 75.0 75.0 gr/lb 99.1 111.9 127.2
Water Evaporated (lbs/hr) 8.2 9.9 Bleed to Dewatering 8.2 Bleed =
Evap Pad (lbs/hr) Rate/(CoC - 1) Water To Drain (lbs/hr) 0.0
Resultant Cycles 1908 (Evap Rate/Bleed Rate) + 1
[0051] An initial prototype was created to test the method and
prototypical device. An evaporative cooler module designed to treat
10,000 scfm of air was positioned outdoors in the hot summer
climate in San Antonio, Tex. The cooler included evaporative
cooling media, in particular, Munters GLASdek 7060, 8'' deep
structured fill evaporative cooling media as the primary
evaporative cooling pad, a sump with float fill valve, a
recirculating pump to apply water continuously to the top of the
GLASdek pad, and a fan to draw air across the cooler. The system
was also fitted with a conductivity controller and a bleed valve in
order to control sump Total Dissolved Solids (TDS).
[0052] Water analysis for the San Antonio water district (SAWS) was
used to conduct a Puckorius scale index evaluation to determine the
appropriate cycles of concentration (CoC). Table 6 below sets forth
of values contained in the SAWS water quality report:
TABLE-US-00006 TABLE 6 Make-up Water Analysis Constituent User
Entry Units Ca (as CaCO3)* 67.00 mg/l, ppm Mg (as CaCO3) 14.20
mg/l, ppm T Alkalinity (as 220.00 mg/l, ppm CaCO3)* Conductivity
604 .mu.S/cm, .mu.ohms/cm pH** 7.70 units Water Temp (.degree. F.)*
70.00 (.degree. F.) (Set by Administrator) Silica (as SiO.sub.2) =
0.50 mg/l, ppm Chloride (as Cl.sub.2) = 20.00 mg/l, ppm Phosphate
(as PO.sub.4) = 0.5 mg/l, ppm Iron (as Fe) = 0.05 mg/l, ppm
Manganese (as Mn) = 14.20 mg/l, ppm Barium (as Ba) = 0.00 mg/l, ppm
Fluoride (as Fl) = 0.10 mg/l, ppm Sulfate (as SO.sub.4) = 25 mg/l,
ppm Sodium (as Na) = 10 mg/l, ppm
[0053] Given the Puckorius scaling index evaluation in Table 7
below, it was decided to set the Cycles of Concentration for the
test to 2.2. The value of 2.2 was chosen as it is slightly above
ideal, but still stable and would provide a long scale-free primary
exchanger life.
TABLE-US-00007 TABLE 7 # of Calcium (as Mg (as TAlk (as
Conductivity pH Water SiO2(as Cycles CaCO3) CaCO3) CaCO3) (mmho/cm)
(Estimated) Temp (F.) such) Recommended Maximum Scaling No Limit
Scaling Scaling 6.8-9.5 95 125 Values for Circulating Index Index
Index Driven Water Driven Driven Raw Water 1.00 67.0 14.20 230.0
604.0 7.7 70.0 0.50 Low Cycles 1.63 108.9 23.09 250.5 982.0 8.4
70.0 0.81 Ideal Cycles 2.02 135.5 28.71 311.6 1221.2 8.5 70.0 1.01
High Cycles 2.51 168.5 35.70 387.4 1518.5 8.6 70.0 1.26 # of
Chloride Phosphate Floride Sulphate Puckorius Cycles (as such) (as
such) (as such) (as such) Index Scaling Tendency Recommended
Maximum 400 10 10 6-7 Values for Circulating Water Raw Water 1.00
20.00 0.50 0.10 25.00 7.51 Slight Scale Dissolving Low Cycles 1.63
32.52 0.81 0.16 40.64 7.00 Very Slightly Scale Dissolving Ideal
Cycles 2.02 40.44 1.01 0.20 50.55 6.50 Ideal High Cycles 2.51 50.29
1.26 0.25 62.86 6.00 Stable Water
[0054] At the time of the test, the incoming water TDS was measured
to be 250 ppm, so the conductivity controller was set to 550 ppm to
achieve the desired CoC. The system was run with water meters on
both the fill and bleed lines to confirm that an appropriate amount
of water, approximately 45%, was bleeding in order to maintain the
sump TDS at 550 ppm.
[0055] Next, the system was fitted with 2'' deep CELdek 7060
evaporative cooling media on the inlet air stream as the auxiliary
evaporative cooling media. Other types of evaporative media can
also be used, such as Aspen pads made of random weaving of shaved
aspen wood; however, design considerations would favor the use of a
structured evaporative fill such as CELdek due to the low pressure
drop and consistently sized air openings that will provide
consistent and repeatable scale build-up with negligible effect on
the air pressure drop. The bleed water that was used to control the
main sump TDS was directed to the top of this media. Any water that
left the bottom of the pads was measured and directed to drain.
[0056] Evaporative performance of the auxiliary media (mineral
removal media) was analyzed. Over the majority of the face of the
media, water completely evaporated from the surface of the media
before it could exit the bottom to drain, while in areas where the
water supply distributed to the top of the media was above the
average, a portion of the water would make it to the bottom of the
media and to drain. Despite this deficiency, the net amount of
water leaving the pad to drain was reduced from 45% (CoC 2.2) to
approximately 10% (CoC 10).
[0057] The weight of the media can be monitored over time to
measure the scale buildup and determine how long it may be able to
be used before it will need to be replaced or cleaned. In the
example, after one week of operation there was no noticeable scale
buildup on the auxiliary media. After one month, slight scale could
be seen, but with no blocking of the air passages of the media.
Estimation of the weight of scale that CELdek media can hold and
the water bleed savings indicate that the media can provide an
entire season's cooling (3-6 months) without replacement. Media
with higher scale holding content, or media produced from polymeric
materials or other materials that may be cleaned, can also be
used.
[0058] In the example, the bled water was not uniformly distributed
to the top of the auxiliary (mineral removal) media. Preferably,
however, the bleed water distribution to the top of the de-watering
media is made as uniform as possible so that flow across the face
is even and no channeling occurs. Channeling of the water flow
allows excess flow to leave as system bleed in the high flow areas,
which is detrimental to system performance.
[0059] To further improve the prototype efficiency and
effectiveness, the 2'' cellulose based CELdek media can be replaced
by 3'' deep GLASdek 7060 glass fiber based media acting as the MRM.
The GLASdek product has a higher wicking and water holding
capacity. This effectively slows the flow of water down the MRM
face and also provides a certain degree of side-to-side and
front-to-back wicking to even the water flow out. The combination
of the added surface area, which results in a net effective
evaporative efficiency increase, and the improved wicking and water
holding capacity of the GLASdek allowed for complete evaporation of
the bleed water with a net effective CoC of infinity for the
system.
[0060] Also, preferably the mineral removal media is formed as a
matrix of small modular media sections 340-1, as shown in FIG. 2.
The modular media sections 340-1 are preferable mounted with a
mechanism that allows them to be easily interchangeable, such as
frame 341. As the media depth is small, the strength of the media
to resist the force of airflow is low. Smaller, modularized
sections in simple frames will allow for complete media support and
provide for easy interchangeability. Additionally, by modularizing
the media face, only those sections with the highest scale content
would need replacing, reducing ongoing costs. This is important as
it is expected that the upper media will scale more readily and
thus need replacing more frequently.
[0061] It should be noted that in retrofit applications, the
mineral removal media can be added to the existing primary
evaporative cooler inlet face. This, of course, creates added
pressure drop and with it extra operating costs. For systems
designed with the mineral removal media as part of the initial
system, the evaporative performance of the de-watering media can be
included in the system performance, thus reducing the performance
need on the primary evaporative surface. In such a manner the
system could be designed with no substantial increase in pressure
drop while increasing the CoC, thus reducing the water usage by a
large factor.
[0062] One method of control involves sensing the location of a wet
to dry line on the mineral removal media. Ideally, the media should
be wet nearly to its lower edge, with the lowest portion dry. The
wetness of the media can be determined most easily by a sensor 350
that either measures the temperature of the media, directly or
optically, or measures the temperature of the air exiting the
media.
[0063] Another approach to control is to size the mineral removal
media efficiency above that required by the analysis of the
suitable CoC for the given water quality. Bleed water can then be
fed to the mineral removal media at a rate that just allows for the
bleed water to reach the exiting edge of the media. The presence of
water can be monitored by the temperature method outlined above or
by the use of a water presence detection system. As the efficiency
of the mineral removal media was oversized, more bleed water will
have been taken from the main sump than was necessary, and the sump
mineral level will be below the specified maximum content.
[0064] It should be noted that some evaporative cooling systems do
not include a sump and recirculation pump. Instead, fresh water is
applied to the evaporative section and any excess water that is not
evaporated in the process is directed to drain. These
"once-through" systems intentionally apply excess water so that the
minerals in the water do not exceed a threshold which will allow
for scale formation as the water evaporates in the process. Thus,
ideally the water leaving the system is of nearly saturated mineral
content and of small volume. In these cases the excess water which
leaves the system with high mineral content can be utilized in the
same manner as the bleed water in the examples above. It can be
used to treat the mineral removal media to reduce or eliminate its
volume in the same fashion as the bleed water described in the
recirculated water example. Therefore, the term "bleeding" can be
used to connote both bleeding a portion of cooling fluid
recirculating through a primary cooling unit as well as collecting
the remaining "once-through" cooling fluid and supplying the
collected fluid to the secondary cooling unit.
[0065] The auxiliary cooling system of the present invention is not
exclusively for use with direct and indirect evaporative coolers.
Any system that creates bleed or waste fluid and that could benefit
from utilizing that fluid in a preconditioning process can be
included within the scope of the invention. It should be noted that
in indirect evaporative systems, the heat load and thus the primary
evaporation rate is not necessarily contingent on the ambient
conditions of the air into which the water is being evaporated. In
these systems, heat is being transferred from a heat load within
the exchanger to a second air stream, the scavenger air stream.
When scavenger (or the cooling) air is dry it will have a large
ability to evaporate the bleed water from the sacrificial media as
the air passes over it on the way to the cooling heat exchanger.
When the scavenger air has a high relative humidity, the amount of
bleed water that can be evaporated in the sacrificial media is
limited. In this case, a sacrificial pad with a very high
evaporative efficiency may be insufficient to evaporate all the
bleed water.
[0066] Thus, for indirect evaporative systems where the load being
cooled is decoupled from the sacrificial air conditions, an optimal
sacrificial media effectiveness cannot be calculated. Thus, it may
be beneficial to increase the evaporative pad efficiency up to 95%
as the bleed water rate is proportional to the evaporative load
which is now likely higher than the available adiabatic evaporating
potential of the cooling air stream.
[0067] Thus, there have been shown and described new and useful
evaporative cooling systems. Although this invention has been
exemplified for purposes of illustration and description by
reference to certain specific embodiments, it will be apparent to
those skilled in the art that various modifications, alterations,
and equivalents of the illustrated examples are possible.
* * * * *