U.S. patent application number 12/804790 was filed with the patent office on 2011-02-03 for evaporative pre-cooler for air cooled heat exchangers.
Invention is credited to Michael Bettencourt, Michael S. Day, Robert D. Penrod, Calvin R. Wylie.
Application Number | 20110023506 12/804790 |
Document ID | / |
Family ID | 43525697 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110023506 |
Kind Code |
A1 |
Day; Michael S. ; et
al. |
February 3, 2011 |
Evaporative pre-cooler for air cooled heat exchangers
Abstract
The pre-cooler includes one or more cells which are oriented
about an air stream to be cooled. A housing defines a perimeter of
the cell with an inlet and outlet for air passing therethrough.
Water outlet nozzles within the housing are preferably supported
upon bars which orient the nozzles facing in a direction counter to
flow of air through the housing. Each nozzle is coupled to a
separate stage with multiple stages of nozzles coupled to separate
valves. A controller opens or closes different valves. The
controller measures ambient humidity and temperature conditions as
well as air flow rates to calculate the amount of water to be added
to the air and then opens appropriate numbers of stages of valves
so that an appropriate number of nozzles spray water into the air
to saturate the air. Flow rate control is thus provided without
pressure variations, for optimal nozzle performance.
Inventors: |
Day; Michael S.;
(Sacramento, CA) ; Wylie; Calvin R.; (Roseville,
CA) ; Penrod; Robert D.; (Loomis, CA) ;
Bettencourt; Michael; (Elk Grove, CA) |
Correspondence
Address: |
BRADLEY P. HEISLER;HEISLER & ASSOCIATES
3017 DOUGLAS BOULEVARD, SUTIE 300
ROSEVILLE
CA
95661
US
|
Family ID: |
43525697 |
Appl. No.: |
12/804790 |
Filed: |
July 29, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61273008 |
Jul 29, 2009 |
|
|
|
Current U.S.
Class: |
62/91 ;
165/104.34; 165/222; 165/248; 165/60; 62/310; 62/314 |
Current CPC
Class: |
F24F 5/0035 20130101;
F28B 1/06 20130101; F24F 6/14 20130101; Y02B 30/545 20130101; F28C
3/08 20130101; Y02B 30/54 20130101 |
Class at
Publication: |
62/91 ; 165/60;
165/222; 62/314; 62/310; 165/248; 165/104.34 |
International
Class: |
F25D 17/06 20060101
F25D017/06; F24F 3/14 20060101 F24F003/14; F28D 5/00 20060101
F28D005/00; F24F 11/04 20060101 F24F011/04; F28F 13/12 20060101
F28F013/12 |
Claims
1. An evaporative pre-cooler with variable water flow, comprising
in combination: a support interposed within an air stream to be
cooled; a plurality of water outlets coupled to said support and
oriented to discharge water into the air stream; said plurality of
water outlets each including a nebulizer, such that the water is
discharged as a fine spray; a source of water coupled to said
plurality of water outlets and upstream of said plurality of water
outlets; each of said plurality of water outlets coupled to one of
at least two valves downstream of said source of water, with each
said water outlet that is coupled to a common valve discharging
water from said source of water when said common valve is open; and
a controller adapted to operate said at least two valves to cause a
water flow rate into the air stream to be varied.
2. The evaporative pre-cooler of claim 1 wherein said nebulizer
includes an ultrasonic nebulizer.
3. The evaporative pre-cooler of claim 1 wherein said nebulizer
includes a sufficiently small hole in each of said plurality of
water outlets, in conjunction with a sufficiently high pressure of
water upstream of said plurality of water outlets that water
exiting said hole is atomized into a fine spray.
4. The evaporative pre-cooler of claim 3 wherein said valves and
lines coupling said source of water to said water outlets through
said valves are each sized to facilitate a greater flow rate of
water than a sum of water outlet flow rates for water outlets
associated with each said valve, such that pressure upstream of
said water outlets is maintained.
5. The evaporative pre-cooler of claim 4 wherein a pump is
interposed between said source of water and said at least two
valves, said pump pressurizing water upstream of said valves to a
pressure greater than a minimum pressure required to maintain
nebulizer fine spray performance at said water outlets.
6. The evaporative pre-cooler of claim 1 wherein said water outlets
coupled to said common valve of said at least two valves define a
stage, with a number of said stages equal to a number of said
valves downstream of said source of water, each of said stages
having at least two water outlets therein, and wherein said water
outlets of each said stage are spaced apart to decrease
concentration of water within the air stream when said valve
associated with said stage is open and each of said water outlets
associated with said valve is discharging water.
7. The evaporative pre-cooler of claim 6 wherein a plurality of
bars are oriented extending transverse to the air stream, said bars
supporting a plurality of said water outlets thereon, said water
outlets of each said bar coupled to at least two separate
stages.
8. The evaporative pre-cooler of claim 1 wherein said support
includes a partial enclosure surrounding the air stream on lateral
sides of the air stream, and with an open front and rear, with the
air stream entering said front of said enclosure and exiting said
rear of said enclosure, said enclosure having a depth between said
front and said rear at least as great as a majority of spray
distance of said fine spray of water discharged from said plurality
of water outlets.
9. The evaporative pre-cooler of claim 8 wherein said water outlets
are located closer to said rear than to said front and with said
water outlets facing at least partially toward said front of said
enclosure.
10. The evaporative pre-cooler of claim 8 wherein a drift
eliminator is located adjacent said rear of said enclosure, said
drift eliminator having a plurality of open cells passing entirely
therethrough and adapted to allow the air stream to pass through
said cells in said drift eliminator, said cells having an at least
somewhat curving path such that the air stream is required to curve
while passing through said cells of said drift eliminator.
11. The evaporative pre-cooler of claim 10 wherein said water
outlets are located adjacent said drift eliminator and facing away
from said drift eliminator.
12. The evaporative pre-cooler of claim 11 wherein a drain is
located below said drift eliminator, said drain adapted to collect
water condensing on said drift eliminator and falling down off of
said drift eliminator, said drain coupled to said plurality of
water outlets through a pump upstream of said water outlets, such
that water condensing on said drift eliminator is at least
partially recycled back to said water outlets.
13. The evaporative pre-cooler of claim 1 wherein an anemometer is
coupled to said support and oriented to measure a flow rate of the
air stream to be cooled, said anemometer coupled to said controller
to supply a signal related to speed of the air stream to be
cooled.
14. The evaporative pre-cooler of claim 13 wherein a humidity
sensor is coupled to said support and positioned to measure
humidity of the air stream to be cooled, said humidity sensor
adapted to send a signal to said controller indicative of humidity
of the air stream to be cooled.
15. The evaporative pre-cooler of claim 1 wherein a sensor is
located downstream of said water outlets, said sensor adapted to
measure humidity of the air stream after the air stream has been
cooled by evaporation of the fine spray of water discharged by said
plurality of said water outlets, said sensor supplying a signal in
the form of feedback to the controller to adjust a water flow rate
from said plurality of water outlets responsive to humidity sensed
by said humidity sensor downstream from said water outlets.
16. The evaporative cooler of claim 1 wherein said support is
located adjacent an air inlet of an air receiving mechanical device
with a fan therein, said fan generating the airflow, a signal
associated with speed of said fan coupled to said controller to
supply a signal related to speed of the air stream to be
cooled.
17. A water evaporation pre-cooler, comprising in combination: a
plurality of water outlets oriented to discharge water into an air
stream; said plurality of water outlets each including a nebulizer,
such that the water is discharged as a fine spray; a primary source
of water coupled to said plurality of water outlets upstream of
said plurality of water outlets; a drain below said plurality of
water outlets, said drain adapted to collect condensed water from
said water outlets; said drain routed to a secondary source of
water coupled to said plurality of water outlets upstream of said
plurality of water outlets; and at least one feed valve upstream of
said plurality of water outlets, said at least one feed valve
adapted to control which of said primary source of water and said
secondary source of water supplies water to said plurality of water
outlets.
18. The water evaporation pre-cooler of claim 17 wherein said
primary source of water has a greater water capacity than said
secondary source of water.
19. The water evaporation pre-cooler of claim 18 wherein said
primary source of water has a water capacity greater than twice a
capacity of water in said secondary source of water.
20. The water evaporation pre-cooler of claim 19 wherein said
primary source of water has a water capacity at least ten times
greater than a water capacity of said secondary source of
water.
21. The water evaporation pre-cooler of claim 17 wherein said
secondary source of water has a lesser amount of dissolved solids
contained therein than said primary source of water.
22. The water evaporation pre-cooler of claim 17 wherein a drift
eliminator is located downstream of said water outlets, said drift
eliminator having a plurality of open cells passing entirely
therethrough and adapted to allow the air stream to pass through
said cells in said drift eliminator, said cells having an at least
somewhat curving path such that the air stream is required to curve
while passing through said cells of said drift eliminator.
23. The water evaporation pre-cooler of claim 22 wherein an
enclosure surrounds at least portions of the air stream to be
cooled, said enclosure including an entrance opposite an exit with
said entrance adapted to receive said air stream therein and said
exit adapted to discharge said air stream therefrom, said enclosure
including a floor on one lateral side of the air stream extending
between said entrance and said exit, said floor having said drain
therein, said floor located beneath said drift eliminator, said
drift eliminator located adjacent said exit of said enclosure.
24. The water evaporation pre-cooler of claim 23 wherein said water
outlets are located adjacent said drift eliminator and oriented to
spray said fine spray of water at least partially toward said
entrance of said enclosure.
25. The water evaporation pre-cooler of claim 24 wherein each of
said plurality of water outlets is coupled to one of at least two
valves downstream of both said primary source of water and said
secondary source of water, with each said water outlet that is
coupled to a common valve discharging water when said common valve
is open.
26. The water evaporation pre-cooler of claim 25 wherein said water
outlets coupled to said common valve of said at least two valves
define a stage, with a number of said stages equal to a number of
said valves downstream of said source of water, each of said stages
having at least two water outlets therein, and wherein said water
outlets of each said stage are spaced apart to decrease
concentration of water within the air stream when said valve
associated with said stage is open and each of said water outlets
associated with said valve is discharging water.
27. The water evaporation pre-cooler of claim 26 wherein a
plurality of bars are oriented extending transverse to the air
stream, said bars supporting a plurality of said water outlets
thereon, said water outlets of each said bar coupled to at least
two separate stages.
28. A method for cooling an air stream, including the steps of:
providing a plurality of water outlets oriented to discharge water
into the air stream, the plurality of water outlets each including
a nebulizer, such that the water is discharged as a fine spray, a
source of water coupled to the plurality of water outlets and
upstream of the plurality of water outlets, each of the plurality
of water outlets coupled to one of at least two valves downstream
of the source of water, with each water outlet that is coupled to a
common valve discharging water from the source of water when the
common valve is open, and a flow rate controller coupled to the
water outlets and adapted to control a rate of flow out of the
water outlets; determining an amount of water flow needed to cool
the air stream a desired amount by evaporation of the water into
the air stream; and adjusting the at least two valves to adjust a
number of water outlets discharging water to more closely match the
needed amount of water flow.
29. The method of claim 28 including the further step of defining
water outlets coupled to a common valve as being associated with a
common stage, with a number of stages equaling a number of valves,
with each stage having a corresponding water flow rate when open;
and selecting stages to be open as needed to total the desired
amount of water flow.
30. The method of claim 29 including the further step of spacing
water outlets within common stages so that when a stage is
operating water outlets associated with the operating stage are
spaced apart to distribute water evenly within the air stream.
31. The method of claim 30 including the further step of dividing
the air stream into separate portions and providing separate cells
associated with each portion of the air stream to be cooled, the
separate cells each including a separate enclosure which surrounds
at least portions of the air stream to be cooled, said enclosure
including an entrance opposite an exit with the entrance adapted to
receive the air stream therein and the exit adapted to discharge
the air stream therefrom, the enclosure including a floor on one
lateral side of the air stream extending between the entrance and
the exit.
32. The method of claim 31 including the further step of collecting
unevaporated water from the air stream by providing a drift
eliminator adjacent each exit, the drift eliminator having a
plurality of open cells passing entirely therethrough and adapted
to allow the air stream to pass through the cells in the drift
eliminator, the cells having an at least somewhat curving path such
that the air stream is required to curve while passing through the
cells of the drift eliminator.
33. The method of claim 31 wherein said dividing step includes the
step of configuring each cell to have the floor thereof located
beneath the drift eliminator and adjacent the exit of the
enclosure.
34. The method of claim 33 including the further step of
configuring each cell to have a separate controller and separate
valves for independent operation of the separate cells on an
associated portion of the air stream.
35. The method of claim 33 wherein the separate cells include a
common controller and common valves with each stage having at least
one water outlet associated with each cell.
36. The method of claim 28 including the further step of locating a
drain below said plurality of water outlets, the drain adapted to
collect condensed water from the water outlets, the drain routed to
a secondary source of water coupled to the plurality of water
outlets upstream of the plurality of water outlets, and locating at
least one feed valve upstream of the plurality of water outlets,
the at least one feed valve adapted to control which of the source
of water and the secondary source of water supplies water to the
plurality of water outlets.
37. The method of claim 36 wherein the secondary source of water
has a capacity less than a capacity of the source of water.
38. The method of claim 37 including the further step of cycling
the feed valve to cause the water outlets to periodically receive
water from the secondary source of water, the secondary source of
water having a lesser amount of dissolved solids therein, such that
said cycling step purges dissolved solids from water lines upstream
of the plurality of water outlets.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit under Title 35, United
States Code .sctn.119(e) of U.S. Provisional Application No.
61/273,008 filed on Jul. 29, 2009.
FIELD OF THE INVENTION
[0002] The following invention relates to evaporative coolers which
add water to unsaturated air to cause a temperature of the air to
be reduced. More particularly, this invention relates to
evaporative pre-coolers for use upstream of an inlet air stream of
a heat exchanger or other air receiving mechanical equipment, such
as a gas turbine, to improve the thermodynamic performance and/or
heat transfer effectiveness of the equipment.
BACKGROUND OF THE INVENTION
[0003] The efficiency of both air cooled heat exchangers and gas
combustion turbines, as well as other mechanical equipment
increases as air temperature decreases. Furthermore, such equipment
also generally increases in efficiency as the mass of the air
increases, such as high or humidity air versus lower humidity air.
Water (and other liquids) when provided in liquid form adjacent
unsaturated air will tend to evaporate into the air. This
evaporation will continue until the air is saturated. Air is
saturated with water in different amounts based on the temperature
of the air, with hotter air taking a larger amount of water before
reaching saturation.
[0004] A known phenomena when water evaporates into unsaturated air
is that the air is cooled. The water transitioning from a liquid
state to a gaseous state is transitioning from a lower energy state
to a higher energy state. The energy required for this transition
to take place is provided to the water in the form of heat that is
taken out of the surrounding air. This latent heat of vaporization
leaving the air causes a temperature of the air to be reduced.
[0005] A device which utilizes this principle for cooling is often
referred to as an evaporative cooler. Another term for such a
device, when used for air conditioning of a residential space, is a
"swamp cooler." Such evaporative coolers come in a variety of
different configurations. In one configuration, evaporative
pre-coolers are placed upstream of heat exchangers such as those
provided in a direct expansion air conditioning system, an air
cooled chiller, a process cooler, a refrigeration condensing unit
or any other form of air cooled heat exchanger. The water is known
in such systems to be discharged in the form of a fine spray
nebulized by passing the spray at high pressure through a small
orifice. Such water spray nozzle arrays are often also referred to
as a "mister."
[0006] Numerous problems exist in implementing such evaporative
pre-coolers with such heat exchangers or other air receiving
equipment. For instance, large air cooled heat exchangers with
multiple independently staged fans have highly complex and variable
air flow. One section of a device may have air flow of two feet per
second while a different section of the same device may
simultaneously have air flow of ten feet per second. Existing
monoblock pre-cooler systems cannot adapt to this air flow rate
variability, and so either supply too much water or too little.
[0007] Supplying too much water wastes water and can damage a heat
exchanger or turbine. In such cases liquid water is entrained into
the air stream where it can do damage either through direct
impingement or through the deposition of dissolved solids on the
heat exchanger.
[0008] Providing too little water flow results in lower efficiency
gains than could be achieved using the correct amount of water.
Because such fine mist water spray requires substantially constant
high pressure for effective operation, merely throttling water flow
through a flow rate control valve to provide variable water flow
rates results in degradation of performance of the nebulizer and
less fine spray, thus providing an incomplete solution.
[0009] Some pre-cooler systems rely on rapid acting valves to
control flow. This strategy presents a challenge to high pressure
flash evaporative systems. With a rapid acting strategy there are
periods of both ramping up pressure and ramping down pressure. In
both cases, pressure at the nozzle is at less than the optimal
value for some period of time for a portion of the cycle. This
portion of time in each cycle which is spent at sub-optimal
pressure degrades high pressure nozzle performance.
[0010] Other types of pre-coolers which utilize saturated water
pads and flow air through those pads are less than desirable for a
variety of reasons. For instance, they have a tendency to shed
large amounts of water into the air flow which then can damage
downstream equipment. Furthermore, large amounts of water require
recycling, and such recycling systems which recirculate a bulk of
the water therein have a tendency to concentrate dissolved solids
during recycling, ultimately leading to scale buildup and
performance degradation. While chemical treatment (and/or periodic
or continuous water discharge) can reduce scale formation and
biological growth, such chemical treatments (and/or discharge) can
present a negative ecological impact.
[0011] When sodden pads are utilized and droplet carry over is
experienced, the droplets of water, usually containing high levels
of dissolved solids, impinge upon the conditioned device. This
impingement can result in additional scale buildup for downstream
equipment and also potentially damage to downstream equipment
through direct impingement.
[0012] Control systems for evaporative pre-coolers often utilize a
temperature sensor at the outlet of the heat exchanger and feed
this temperature sensor back to a controller which controls water
flow into the system. These designs are problematic because the
temperature response signal becomes corrupted by heat rejected by
the heat exchanger of the upgraded unit. For instance, when the
heat exchanger is drawing a large amount of heat from a working
fluid within the heat exchanger, this outlet temperature will
increase. However, the air entering the heat exchanger might
already be saturated, and such a feedback signal will
inappropriately add water flow beyond a point of saturation of the
air with associated negative consequences.
[0013] Other sensors for evaporative coolers may try to sense
ambient psychrometric conditions but fail to measure air flow to
the device. Without knowing both airflow and psychrometric
conditions, it is not possible to calculate or deliver an
appropriate mass of water for a given air stream. Finally, due to
the highly variable nature of airflow for independently staged
multi-fan systems, air streams must be segregated and analyzed
independently to avoid delivering either too much or too little
water.
SUMMARY OF THE INVENTION
[0014] With this invention, an evaporative pre-cooler is provided
for use adjacent an air stream, such as an air stream feeding into
a heat exchanger or turbine or other equipment which receives air
therein. The pre-cooler includes a plurality of water outlets.
These water outlets include a nebulizer to discharge a fine spray
of water into the air stream. To control the flow rate of water
added to the air, the water outlets are divided into separate
stages with each stage having at least two water outlets and each
water outlet associated with a single separate stage. A valve is
provided for each stage to open and close the stage.
[0015] Each stage provides a known amount of water flow being
discharged into the air stream. Thus, when a certain amount of
water flow into the air stream is desired, valves are opened
associated with stages whose flow rates sum to the desired amount
of water flow. Because the valves are either open or closed, rather
than throttling/pressure based flow rate adjustment valves, a high
pressure is maintained and both well-nebulized spray and precise
water flow rates are delivered into the air stream.
[0016] To control the pre-cooler, typically a sensor package is
provided which senses characteristics about the airflow to be
cooled. This sensor package includes an anemometer or other air
flow rate sensor and some measure of the humidity of the air within
the air stream, such as wet bulb temperature and dry bulb
temperature sensors. With such sensors and by characterizing the
humidity of the air to be treated, and knowing an amount of
humidity that can be added to the air, as well as knowing the flow
rate of the air, an operator (or programmed/calibrated machine) can
calculate how much water flow rate to add to the air and then open
associated valves of associated stages to provide the moisture
required.
[0017] When the airflow to be cooled is highly variable, such as at
separate inlets of a multi-unit heat exchanger, such as a typical
rooftop air conditioning heat exchanger of an industrial building,
separate cells can be provided which each measure separate
airflow.
[0018] Humidity conditions can be shared amongst the individual
cells or separately measured also. Calculated amounts of moisture
to add at each cell can then be utilized to open and close valves
associated with stages so that the precise proper amount of water
is supplied in each cell. As an alternative, if the separate heat
exchanger units can be controlled so as to have a common airflow
rate thereinto, then a common signal can be provided to each cell
with a common amount of moisture supplied at each cell. Conceivably
also, valves associated with individual stages can supply water to
multiple different cells in such systems where the heat exchangers
are operating at a common airflow rate.
[0019] One form of equipment which effectively implements this
system includes cells which are in the form of housings with an
open front and an open rear allowing the airflow to pass
therethrough. Water outlets are provided in the form of nozzles
extending from bars located near the exit of this housing. The
nozzles face forward, in a counter-flow direction relative to the
air stream, so that a mist pattern from each nozzle tends to remain
within the enclosure before the moistened air is driven out of the
exit. Housing depth is selected to so keep most of a mist cloud
from the nozzles within the housing.
[0020] A drift eliminator is preferably provided adjacent the exit
which provides multiple separate curving cells through which the
moistened air must pass before leaving the housing. The drift
eliminator keeps water droplets entrained within the airflow but
not yet evaporated from exiting the housing and doing damage
downstream from the cell.
[0021] Each nozzle is associated with a separate stage. If the
stage that a nozzle is associated with is called for by the
controller and the associated valve for that stage is opened, high
pressure water will flow to the nozzle and a fine spray will be
discharged therefrom. Preferably, each bar has multiple lines
therein with one line associated with each stage. The nozzles are
coupled to one of the lines associated with one of the stages in a
pattern which causes nozzles within a common stage to be well
separated from each other and in a generally evenly distributed
pattern. Thus, when a single stage is on, a well distributed
pattern of fine spray is provided within the housing for even
moistening of air passing therethrough.
[0022] A lower portion of the housing preferably includes a drain
therein which can draw away water, such as that resulting from
direct contact of the fine spray with walls of the housing, and to
some extent excess water pulled from the drift eliminator. In
addition, naturally occurring condensate, such as from an
evaporation coil can also be collected. This condensed water will
tend to be relatively low in dissolved solids. These water sources,
together or separately, can be collected and periodically pumped
and recycled back to the water outlets. Such periodic recycling not
only decreases water demand for the overall system but also acts as
a form of purge in that the condensed water that is recirculated
tends to be exceptionally low in dissolved solids and so can tend
to remove scale deposits which might otherwise collect within the
system.
OBJECTS OF THE INVENTION
[0023] Accordingly, a primary object of the present invention is to
provide an evaporative pre-cooler to decrease a temperature of air
upstream of an air inlet of mechanical equipment.
[0024] Another object of the present invention is to provide an
evaporative pre-cooler which increases a mass of air entering an
air inlet of mechanical equipment.
[0025] Another object of the present invention is to enhance
efficiency of a heat exchanger by pre-cooling cooling air entering
the heat exchanger.
[0026] Another object of the present invention is to enhance
efficiency of a power plant by decreasing a temperature of
combustion air entering the power plant.
[0027] Another object of the present invention is to enhance
efficiency of a power plant by increasing effectiveness of a heat
exchanger and/or decreasing a size of a heat exchanger required for
the power plant by evaporatively pre-cooling air utilized for
cooling of working fluid within the heat exchanger.
[0028] Another object of the present invention is to provide an
evaporative pre-cooler which is adjustable to provide a proper
amount of water to air for air saturation, and without excessive
water usage.
[0029] Another object of the present invention is to provide an
evaporative pre-cooler which recirculates condensing portions of
water and run-off water utilized thereby to minimize water
consumption.
[0030] Another object of the present invention is to provide an
evaporative pre-cooler which minimizes scale buildup within the
pre-cooler system itself and minimizes scale buildup for downstream
equipment.
[0031] Another object of the present invention is to provide an
evaporative pre-cooler which is modular in form to be deployable in
a scalable fashion with smaller and larger mechanical equipment
which receives air therein.
[0032] Other further objects of the present invention will become
apparent from a careful reading of the included drawing figures,
the claims and detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a perspective view of a heat exchanger with a
series of pre-cooler cells associated with different heat exchanger
units within an overall heat exchanger system and showing how air
flows through the pre-cooler cells before entering the heat
exchangers.
[0034] FIG. 2 is a perspective view of a single cell with portions
thereof cut away and revealing interior details of the cell.
[0035] FIG. 3 is a side elevation full sectional view of the
pre-cooler cell of FIG. 2.
[0036] FIG. 4 is a schematic view of an alternative embodiment
arrangement for separate stages of water outlets according to an
alternative embodiment of this invention.
[0037] FIG. 5 is a detail sectional view taken along line 5-5 of
FIG. 3 and revealing interior details within a bar supporting
nozzles according to a preferred embodiment of this invention.
[0038] FIGS. 6-16 are schematic views of a preferred embodiment of
this invention and showing how water flow rates from ten percent to
one hundred percent of maximum can each be achieved by opening
different valves for different stages of water outlets according to
this invention.
[0039] FIG. 17 is a flow chart illustrating how water flows within
the system of this invention and particularly illustrating how
partial water recirculation is achieved.
[0040] FIG. 18 is a table with one exemplary set of numbers for
flow rates of air and water within one typical evaporative
pre-cooler system according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] Referring to the drawings, wherein like reference numerals
represent like parts throughout the various drawing figures,
reference numeral 10 is directed to a pre-cooler cell (FIGS. 1 and
2) for use alone or together adjacent a heat exchanger HX or system
1 of multiple heat exchangers HX to pre-cool air (arrow A of FIG.
1) entering the heat exchangers HX. The pre-cooler 10 evaporates
water into the air to reduce a temperature of the air and increase
a mass of the air for enhanced effectiveness of the heat exchanger
HX. The cells 10 are configured to have a precise and highly
adjustable water flow rate while maintaining a fine spray of water
for consistent evaporative effectiveness, maximizing air
temperature reduction while avoiding water droplet carryover
downstream.
[0042] In essence, and with particular reference to FIG. 2, basic
details of the pre-cooler cell 10 of this invention are described,
according to a most preferred embodiment. The cell 10 includes a
housing 20 as a preferred form of enclosure through which air
passes (along arrow A) and receives a fine spray of water (arrow B)
to evaporatively cool the air into humid air discharge flow (arrow
C). Multiple valves 30 (FIG. 3) control water flow through a
manifold 40 and to a plurality of nozzles 60 which are supported on
bars 50 within the housing 20. Each of the nozzles 60 is associated
with one stage and each stage is associated with one of the valves
30. Multiple nozzles 60 are provided within each stage and the
valves 30 can be opened or closed so that a total number of nozzles
60 desired can be opened so that a desired flow rate is
achieved.
[0043] Most preferably, the nozzles 60 are oriented in a direction
opposite that of air flow A for maximization of residence time and
mixing to achieve full evaporation of the fine mist of water
discharged from the nozzles 60. A drift eliminator 70 is provided
at an outlet side of the housing 20. This drift eliminator 70
prevents less than fully evaporated water vapor from passing out of
the housing 20, by providing a curving pathway for the air to
travel upon leaving the housing 20, and capturing such water vapor
thereon.
[0044] An anemometer 80 is associated with the housing 20 to
measure airflow through the cell 10. The anemometer 80 is
configured to send a signal to a controller which opens and closes
valves 30 according to an operational program, and also potentially
taking in other ambient conditions, such as wet bulb temperature
and dry bulb temperature to provide the flow rate of water into the
cell 10 available for maximum evaporative cooling of the air A, or
to achieve other design objectives. Additionally, a dry bulb
temperature sensor 90 or other sensor related to humidity can be
provided downstream of the cell 10 to monitor the effectiveness of
the cell 10 and provide feedback to the controller to increase or
decrease water flow through adjustment of the valves 30 responsive
to actual measurements provided at each cell 10.
[0045] An overall evaporative cooler system 100 can be configured
with water reclamation incorporated therein (FIG. 17). In such a
system water condensing within the cell 10 can be drained into a
collection tank 110 with an associated booster pump to pump the
condensed water back to the cells 10 periodically, such that
overall water demands are diminished. An ambient calculator 120
associated with the system 100 can measure system parameters such
as wet bulb and dry bulb temperatures, or otherwise measure
relative humidity or absolute humidity of the air, and use this
information along with anemometer 80 readings to feed into a
controller for effective control of the system 100.
[0046] More specifically, and with particular reference initially
to FIG. 1, details of systems in which the evaporative pre-cooler
of this invention can be used are described, according to a
preferred embodiment. FIG. 1 displays a multi-fan air cooled heat
exchanger. Multiple cells 10 are arranged around the heat exchanger
HX, such as with one cell 10 adjacent each inlet for air adjacent
each heat exchanger HX. Air entering the heat exchangers HX (along
arrow A) must thus pass through the cells 10 first. Such arrays of
heat exchangers HX often have individually staged fan arrangements
so that the air speed of air passing through one cell may be
different than that passing through another cell.
[0047] In such systems, even though all surrounding air may have a
similar humidity, different cells 10 need to supply a different
amount of water for evaporation within each cell 10 to accommodate
these differing air flow rates. Even if all fans are operated at a
single speed, and velocity is common for all of the heat exchangers
HX, there is still the opportunity to account for other ambient
conditions, such as variability in temperature and/or humidity. For
instance, adjacent equipment might be producing consistently higher
temperatures on one side of the system 1 than on the other side, so
that cells 10 on one side are hotter than on the other side.
[0048] Heat exchangers increase in effectiveness proportional to
temperature difference between the heat transfer fluids. Hence, the
cooler the air entering the heat exchanger HX, the more effective
the heat exchanger. Furthermore, the greater the mass of the heat
exchange fluid removing heat, the more effective the heat exchanger
is, in that each unit mass of heat transfer fluid can carry a
greater amount of heat out of the heat exchanger HX. Thus, by
cooling the air A and increasing a mass density of the humidified
air into humidified air (arrow C), a greater amount of heat
transfer can occur through the heat exchanger HX. Either system
performance is enhanced in that the fluid being cooled is cooled to
a lower temperature, or fans which draw cooling air A into the heat
exchanger HX need not run as hard to provide sufficient air A for
cooling. Ultimately, heat exchangers HX can be sized smaller if
they are configured to operate more effectively.
[0049] Furthermore, many power plants operate on power production
cycles which have an overall thermal efficiency which is
proportional to changes in temperature of the working fluid. The
cooler the working fluid is at an inlet of such power cycles, the
greater thermal efficiency which can be obtained. For instance,
with a combustion gas turbine operating on a Brayton cycle, the
cooler the inlet air, the greater the thermal efficiency of the
power plant, and hence the greater amount of power that can be
generated for a given amount of fuel being combusted.
[0050] Depending on the equipment with which the cells 10 are to be
utilized, the cells 10 can be scaled in size or can be provided in
arrays of greater or lesser numbers of cells 10. When multiple
cells 10 are utilized, they can be configured to operate
independently and separately with their own controls and their own
sensors. Alternatively, the cells 10 can be to at least some extent
integrated together such as by utilizing similar sensors, similar
valves and similar water supply and water recirculation
systems.
[0051] With particular reference to FIGS. 2 and 3, details of each
individual pre-cooler cell 10 are described, according to a most
preferred embodiment. Each pre-cooler cell 10 preferably has a
similar configuration to other cells 10. Each cell 10 includes an
outer housing 20 which is a substantially complete enclosure except
for an inlet 26 and outlet 28 for air A to enter into the cell 10
and exit as humid air out (arrow C of FIGS. 2 and 3). The housing
10 includes a floor 21 opposite a cap 22. Sides 25 extend up from
the floor 21 to the cap 22. Preferably, the sides 25 are parallel
with each other and the floor 21 and cap 22 are parallel with each
other and perpendicular to the sides 25, so that the housing 20 is
generally rectangular/square in cross-section.
[0052] A lattice 24 is preferably provided which spans the inlet
26. This lattice 24 can tend to keep debris out of the housing 20
or can be used to mount a pre-filter to enhance the same effect, as
well as keeping water spray contained. A depth of the housing 20
between the inlet 26 and outlet 28 is sized so that the water spray
within the housing 20 from the nozzles 60 tends to remain
substantially within the housing 20. Thus, the housing 20 defines a
reaction chamber where the water is evaporated fully into the air
A, before exiting the housing 20 as humidified cooled air C.
[0053] The floor 21 not only defines a wall of the housing 20 but
also preferably acts as a drain pan with a drain included at a low
point of the floor 21. Thus, any non-evaporated water occurring
within the housing 20 is captured for potential recycling, as
described in detail below.
[0054] A plurality of valves 30 are preferably associated with each
cell 10, and typically mounted on the cap 22 under an optional
cover 23 to protect the valves 30 from weathering, solar radiation
or damage from other surrounding environmental conditions. An array
of such valves 30 is preferably configured so that one valve 30 is
provided for each stage within each cell 10. In a preferred cell 10
four stages are provided so that four valves 30 are provided. Each
valve 30 is coupled to a high pressure water main line 32. This
main line 32 preferably supplies each of the cells 10 with high
pressure water from a single high pressure pump package 106 (FIG.
17) or other high pressure water source. High pressure water is
utilized to ensure that the nozzles 60 maintain optimal performance
and nebulize the water being discharged by the nozzles 60.
[0055] Each valve 30 includes a body 34 and a control 36 which
interacts with a valve element within the body 34. An outlet 38 is
provided opposite the high pressure water main line 32. This outlet
38 feeds a manifold 40 which splits up the water for each stage
associated with the valve 30 and sends it to multiple separate
lines located within multiple separate bars 50 (FIG. 5) for
ultimate routing to nozzles 60 associated with the stage to which
the valve 30 is coupled.
[0056] The valves 30 are preferably of a type which transitions
between either a fully open or a fully closed position, as opposed
to being a variable flow rate valve. Thus, when the valves 30 are
open the pressure drop across the valve 30 is negligible. When the
valve 30 is closed, no flow across the valve 30 occurs. The control
36 interacts with the valve element within the body 34 to cause the
valve 30 to transition between an open and a closed state depending
on signals received from a central controller associated with each
cell 10, or conceivably a controller which serves all of multiple
cells 10.
[0057] Each valve 30 is associated with a single stage, as well as
a separate manifold 40 (FIGS. 3 and 4). The manifold 40 has
separate lines 42. These lines typically include junctions 44 (FIG.
4) which allow the manifold 40 to direct water to separate lines 42
which are in parallel with each other. These lines 42 can then pass
into individual bars 50. Most preferably, each bar 50 has multiple
lines 42 therein, with at least one line 42 associated with each
stage (FIG. 5). As an alternative, and as shown in FIG. 4,
conceivably only one line 42, or multiple lines 42 but less than
the number of stages, could be supplied to each bar 50. In the
system depicted in FIG. 4, the separation of the stages and the
individual valves 30 associated with each stage can be most readily
seen. However, the nozzles 60 tend to be somewhat tightly grouped
together for less than optimal distribution to all of the air
entering the housing 20, in the embodiment of FIG. 4. Thus,
preferably each bar 50 has nozzles 60 associated with different
stages on each bar 50 to better distribute nozzles 60 within a
common stage away from each other.
[0058] The nozzles 60 preferably face in a direct counter flow
direction (along arrow B of FIGS. 2 and 3). Alternatively, the
nozzles 60 could be angled somewhat in different directions to
better enhance their ability to direct fine spray of water
uniformly within the housing 20. While the embodiment of FIG. 4
shows a single line fed to each bar 50 and with each nozzle 60 of
each bar 50 being associated with the stage that that bar 50 is
coupled to, most preferably, each bar 50 has multiple lines passing
thereinto with the lines coming from different stages and with the
nozzles 60 on the bar 50 coupled through tees 43 to different
stages within a single bar.
[0059] For instance, and with reference to FIG. 5, line 42A is
shown associated with stage one and line 42B is shown associated
with stage two, with line 42C and line 42D associated with stages
three and four, respectively. A tee 43A is formed in line 42A which
feeds one of the nozzles 60. A next adjacent nozzle 60 within the
same tube 50 has a tee 43B associated with line 42B coupled
thereto.
[0060] FIGS. 6-16 show various different states for the overall
array of nozzles 60. In FIG. 6 a state is shown where all of the
stages are closed and hence all of the nozzles 60 are off. In FIG.
7, a ten percent flow arrangement is illustrated where only stage
one is open and so the five nozzles 60 associated with stage one
are open. In FIG. 8 a state is illustrated for twenty percent flow
where only the nozzles 60 associated with stage two are open. Note
that twice as many nozzles 60 are associated with stage two as with
stage one (ten nozzles 60 rather than five nozzles 60). In FIG. 9 a
state is illustrated where only the nozzles 60 associated with
stage three are open, so that thirty percent of maximum flow is
provided. In FIG. 10 a state is illustrated where only nozzles 60
associated with stage four are open, so that forty percent of
maximum water flow is provided.
[0061] While the stages herein are shown as having different
amounts of water flow accommodated by having different numbers of
nozzles 60, a similar effect can be provided by having a common
number of nozzles 60 with each stage but having the nozzles 60
sized larger for some of the stages. Alternatively, each of the
stages could have a common number of nozzles 60 so that increasing
flow rate would involve opening multiple stages.
[0062] Most preferably, and as depicted in FIGS. 6-10, stages one,
two, three and four include different numbers of nozzles 60 of
similar sizes so that they provide respectively ten, twenty, thirty
and forty percent of maximum flow. To provide fifty percent of
maximum flow, multiple stages can be open at the same time, such as
stage one and stage four or stage two and stage three. To achieve
sixty percent flow, stage four and stage two can be open together
or stage one, stage two and stage three can each be open together.
To achieve seventy percent of flow, stage four and stage three can
be open or stage four, stage two and stage one can be open
together. To achieve eighty percent of flow, stage four would be
open along with stage three and stage one. To achieve ninety
percent of flow, stage four would be open along with stage three
and stage two. To have maximum flow provided, each of stages one,
two, three and four would be simultaneously open. Additionally,
pump pressure variation above a minimum necessary, can be used to
provide further adjustment of water flow rate through use of a
variable speed, variable pressure pump. In this way flow rates
between the percentages listed above could be provided.
[0063] These various states and the amount of flow provided are
sequentially illustrated in FIGS. 6-16. Each circle represents a
separate nozzle 60 and the nozzles 60 are arrayed upon bars 50 with
separate lines 42 located within each bar 50, as shown in the
detail of FIG. 5. In this preferred embodiment, each bar 50 has an
inlet 52 (FIGS. 2 and 3) at one end through which each of the lines
42 can enter the bar 50. An end 54 opposite the inlet 52 allows for
attachment of the bar 50 within the housing 20, preferably adjacent
the outlet and oriented with a long axis thereof extending
substantially vertically. A face 56 of each bar 50 includes the
nozzles 60 extending therefrom and faces toward the inlet 26 of the
housing 20.
[0064] Each nozzle 60 preferably has a small orifice 64 within a
cap 62 on a side of each nozzle 60 facing toward the inlet 26 of
the housing 20. The size of the orifice 64 is carefully selected
and shaped to maximize atomization of water spray passing
therethrough. Pressure within each stage is maintained sufficiently
high, and orifice 64 size is sufficiently small so that the nozzles
60 maintain their optimal performance providing a fine nebulized
spray from each nozzle 60.
[0065] Because the flow rate is not controlled by a variable flow
rate valve, which inherently also effects pressure, but rather by
having separate stages which can be selectively added together or
subtracted therefrom to provide the desired flow rate, flow rate
adjustment is provided independent of pressure. Thus, the high
pressure required for optimal performance of the nozzles 60 is not
degraded as the flow rates are decreased by throttling a valve.
Rather, even flow rates as low as ten percent of maximum can be
achieved with the stage one valve 30 wide open and all of the other
valves 30 closed. No pressure-controlling valve is in a partially
open and pressure reducing state, but rather the nozzles 60 receive
full pressure at all times. Thus, the nozzles 60 which are
receiving water flow provide a fine nebulized mist of water (arrow
B of FIG. 2) which forms a cloud within the housing 20. The airflow
A entering the housing 20 readily evaporates this fine mist of
water, in turn reducing the temperature of the air and increasing
the humidity of the air before exiting the housing 20 along arrow
C.
[0066] Preferably, the housing 20 includes a drift eliminator 70
adjacent the outlet 28. Due to the relatively laminar flow nature
of the air entering each individual cell, some of the droplets can
become entrapped in a band of saturated air and not be able to
complete the evaporation process. For this reason, an absorptive
media drift eliminator 70 is provided in the air stream downstream
from the nozzles 60. The drift eliminator 70 causes the air to make
rapid turns before entering the conditioned device, such as the
heat exchanger HX (FIG. 1). Due to their greater mass, the water
droplets are not able to make those turns as rapidly, thus
resulting in impact with the drift eliminator 70. The drift
eliminator 70 is preferably formed of a material which is somewhat
absorbent and is readily thus wetted. This wetted surface can give
up additional moisture to drier portions of the airflow A. If the
wetted portions are over-saturated, gravity pulls the excess water
down through the drift eliminator 70 down to the floor 21 of the
housing 20 for excess water collection, as described in detail
below.
[0067] The drift eliminator 70 thus acts differently from a fully
irrigated media pre-cooler pad constructed of similar material.
First, as a drift eliminator 70, the amount of water that impacts
the drift eliminator 70 causes it to become damp, whereas a pad in
a traditional fully irrigated pre-cooler is typically completely
sodden, with rivulets of liquid water flowing down both faces. This
is important because typically completely sodden pads are much more
likely to have droplet carryover. When droplet carryover occurs,
these droplets of water usually containing levels of dissolved
solids, impinge upon the conditioned device. In most cases this
will result in significant scale buildup and has been the principle
barrier to market penetration of pre-coolers utilizing fully
irrigated evaporation pad technology.
[0068] Secondly, since the drift eliminator 70 is only being used
for drift elimination, the absorptive material used can be
significantly thinner. Typical absorptive media pads for fully
irrigated pre-cooler systems are from six inches to twelve inches
in thickness, whereas the drift eliminator 70 of this invention can
be from one to six inches in depth. The combination of reduced
thickness and reduced water loading substantially reduces both the
operational weight and airflow resistance of the described device
when compared to fully irrigated pre-coolers.
[0069] Finally, the surface area of the droplets is larger by an
order of magnitude or more than the surface area of the largest
fully irrigated evaporative pre-coolers. Greater surface area
results in superior cooling performance at a lower weight while the
reduced water load on the material largely eliminates carryover
based equipment degradation effects. Edges 74 of the drift
eliminator 70 reside against the sides 25, floor 21 and cap 22, so
that the airflow A passes through the cells 72 within the drift
eliminator 70. If the air A has water droplets entrained therein
they will be deposited upon the surfaces of the drift eliminator
70. If the air A is not yet fully saturated, the wet surfaces of
the drift eliminator 70 provide a source of water for further
evaporation towards saturation of the air A.
[0070] With particular reference to FIGS. 17 and 18, the operation
of the cells 10 within an overall system 100 for pre-cooling with
water reclamation are described. The system 100 includes a series
of pre-coolers 10 fed by the high pressure water line 32. This
water line 32 is in turn fed from a pump package 106 if necessary
to raise the pressure to the required level. Most preferably, at
least two separate feed valves 104 or a single valve which can
switch from different sources is provided upstream of the pump
package 106 or otherwise upstream of the high pressure main line
32. The main line 32 can thus be fed either from a primary source
of water, such as a municipal water supply 102, or from a secondary
source of water such as a collection tank and associated booster
pump 110 which receives recycled water from drains of the
pre-coolers 10, along a drain line 108.
[0071] An ambient calculator 120 receives as input information
related to humidity of the surrounding air, such as wet bulb and
dry bulb temperatures. Air flow rates can also be part of the
ambient calculator 120, such as through use of the anemometer 90.
This anemometer is shown as a fan blade impeller that rotates about
an axis aligned with the direction of flow. Alternatively, the
anemometer could have an impeller mounted to an axis transverse to
the air flow. As another alternative, an air flow rate signal can
be provided from a fan associated with the heat exchanger HX (FIG.
1) or other equipment adjacent the cell 10. The signal could be a
variable fan speed control signal or a master controller signal
that correlates to the speed desired for the fan, or could be a
tachometer coupled to the fan itself. With these sensor readings,
desired flow rates can be calculated and in turn specific controls
for the valves 30 (FIGS. 1, 3 and 4) can be chosen for operation of
the system 100.
[0072] In particular, the calculator or other controller can
receive the dry bulb temperature, ambient relative humidity, wet
bulb temperature, either calculated or measured, to calculate
absolute humidity in grains per pound of dry air. This absolute
humidity is defined as one hundred percent relative humidity at
ambient wet bulb temperature in grains per pound of dry air. The
absolute humidity in grains per pound of dry air can then be
subtracted from the relative humidity in grains per pound of dry
air to determine how much water in terms of grains per pound of dry
air can be added to the air.
[0073] This amount is then divided by the maximum mass of water
that can be delivered to a pound of dry air, measured in grains.
Ten percent of this amount (rounded down), equals a flow rate for
stage one. Twenty percent of this amount (rounded down), equals a
flow rate for stage two. Third and fourth stages can in turn be
twenty and thirty percent of this amount (rounded down). This
criteria can then be used for sizing of the nozzles 60 when
initially configuring the system. Thereafter, upon sensing airflow
in ambient conditions, the local controller can set the proper mass
of water flow actuating one or more of the several valves 30 either
individually or in concert to achieve the percentage desired of
maximum airflow.
[0074] While this preferred algorithm can be executed by this
invention, other algorithms could similarly be utilized. For
instance, taking into account known typical environmental
conditions and the typical availability of air to receive
additional humidity, before saturation, a typical maximum rate can
be identified. This maximum amount can then be divided into
subparts to be provided by each of the stages in the initial
design.
[0075] In an embodiment typical for this invention, four stages are
provided, but different numbers of stages could be provided in the
alternative. In one embodiment, stage one is provided which is
controlled by a valve which feeds eight separate nozzles 60 which
total 0.1 gallons per minute in flow rate. Stage two includes
sixteen nozzles 60 totaling 0.2 gallons per minute. Stage three has
twenty-four nozzles 60 totaling 0.3 gallons per minute and stage
four has thirty-two nozzles 60 totaling 0.4 gallons per minute.
Different combinations of the stages yield to different mass of
water as is needed to saturate the air down to wet bulb
temperature. For example, if the controls calculate that 0.7
gallons per minute are needed to achieve saturation, then stages
three and four can be operated in conjunction. In this way, a
variable mass of water can be admitted to the air stream (0.1
gallons per minute, 0.2 gallons per minute, etc.) without dropping
below the minimum operating pressure at the nozzle 60.
[0076] Maintaining minimum operating pressure at the nozzle 60 is
critical for flash evaporative cooling operation. Evaporative
performance is linked to droplet size, and droplet size is in turn
linked to pressure at the nozzle. However, a need for variable mass
water flow conflicts with this need for constant pressure at the
nozzle. A staged nozzle 60 system as described herein avoids the
problems inherent with current control methodologies as the
pressure remains constant and flexibility of flow rate is still
provided. The addition of a variable speed/pressure pump allows a
virtually limitless number of flow rates, all in pursuit of
providing a proper mass of water to saturate the air without
producing carryover. For instance, in addition to the stages, some
small amount of pressure regulation and/or speed of an associated
pump can be controlled to fine tune the system while still
maintaining minimum pressure required for nozzle 60 performance.
Such a staged system is thus able to provide variable and precise
flow control without the problems associated with previous examples
of pressure variation.
[0077] While the vast majority of water emitted from the nozzle 60
within the pre-coolers 10 immediately convert to vapor, nozzle type
cells 10 also may have a small amount of unevaporated water that
collects on surfaces of the housing 20 due to impact with walls of
the housing 20 itself. In the preferred embodiment of the system
100, such non-evaporated excess water is conducted away by way of
collection drains along drain line 108 and routed to a collection
tank 110. Condensate drains from evaporator coils can also be
routed to a common collection tank or to a separate condensate only
collection tank.
[0078] When the collection tank 110 is full, controllers shut the
valve coming from a primary water source, such as the municipal
water supply 102 and open valves from the collection tank system
110. When the high pressure pumps are next engaged, an optional
booster pump associated with the collection tank 110 goes into
operation to supply inlet water to the high pressure pump package
106. When the collection tank empties, controls close the valve
from the outlet of the booster pump associated with the collection
tank 110 and turn off the booster pump. The valve from the primary
water source is simultaneously opened.
[0079] Use of a collection tank 110 in conjunction with the flash
evaporative system delivers many benefits. First, condensate from
evaporator coils (alone or mixed with the non-evaporated excess
water from the drain line 108) can be utilized as feed water for
the pre-coolers 10. Use of condensate in this matter not only
reduces overall water consumption by the system, but also reduces
the volume of water which is discharged to waste water treatment
plants. Additionally, because of the extremely low levels of
dissolved solids in condensate drain water, a periodic flushing of
the pump and pre-cooler condensate acts as a solvent removing any
potential buildup of dissolved solids before they can form
performance degrading scale. While a small amount of water will be
returned to the cells 10 for reutilization, the binary nature of
water that is admitted to the pump system either the primary water
source such as the municipal water supply 102, or water from the
collector tank 110 in the form of excess non-evaporated water
and/or condensate water, means that the system as a whole remains
essentially single pass in nature. A single pass system has several
benefits. First, a single pass system will not increase the
concentration of dissolved solids in the recirculating water in the
way that a recirculator system would. This reduces the opportunity
for scale formation that has proven to be such a challenge for
previous evaporative pre-cooler technologies. Additionally, a
single pass system does not need to periodically discharge
saturated water solutions into the waste water treatment
system.
[0080] An alternative embodiment of the cells 10 disclosed herein
is to utilize ultrasonic nebulizers in place of the nozzles 60 for
the injection of water vapor into the air stream A. Multiple
nebulizers can be used in a cell 10, with the same type of
proportional flow control as in the preferred embodiment through
multiple separate stages. Thus, the precise amount of water is
provided as directed by the controller and as indicated by ambient
conditions to provide saturated water without excess condensing
water flow leaving the cells 10.
[0081] This disclosure is provided to reveal a preferred embodiment
of the invention and a best mode for practicing the invention.
Having thus described the invention in this way, it should be
apparent that various different modifications can be made to the
preferred embodiment without departing from the scope and spirit of
this invention disclosure. When structures are identified as a
means to perform a function, the identification is intended to
include all structures which can perform the function specified.
When structures of this invention are identified as being coupled
together, such language should be interpreted broadly to include
the structures being coupled directly together or coupled together
through intervening structures. Such coupling could be permanent or
temporary and either in a rigid fashion or in a fashion which
allows pivoting, sliding or other relative motion while still
providing some form of attachment, unless specifically
restricted.
* * * * *