U.S. patent application number 12/506991 was filed with the patent office on 2010-01-28 for fabrication materials and techniques for plate heat and mass exchangers for indirect evaporative coolers.
This patent application is currently assigned to Idalex Technologies, Inc.. Invention is credited to Alan D. Gillan, Leland E. Gillan, Rick J. Gillan, Valeriy Maisotsenko.
Application Number | 20100018234 12/506991 |
Document ID | / |
Family ID | 41567411 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100018234 |
Kind Code |
A1 |
Gillan; Leland E. ; et
al. |
January 28, 2010 |
FABRICATION MATERIALS AND TECHNIQUES FOR PLATE HEAT AND MASS
EXCHANGERS FOR INDIRECT EVAPORATIVE COOLERS
Abstract
Heat exchanger plates for indirect evaporative coolers, of the
type having a dry side having low permeability to an evaporative
liquid and formed to allow a product fluid to flow over a heat
transfer area of its surface, a wet side designed to have its
surface wet by an evaporative liquid, and formed to allow a working
gas to flow over its surface to evaporate the evaporative liquid,
are formed such that the wet side comprises a hydrophobic fiber
sheet and the dry side comprises a non-permeable sealing layer on
the sheet. Heat seal strips are formed at the inlet and outlet of
the plates and air flow perforations are formed through the
plates.
Inventors: |
Gillan; Leland E.; (Denver,
CO) ; Maisotsenko; Valeriy; (Aurora, CO) ;
Gillan; Alan D.; (Denver, CO) ; Gillan; Rick J.;
(Golden, CO) |
Correspondence
Address: |
JENNIFER L. BALES
MOUNTAIN VIEW PLAZA, 1520 EUCLID CIRCLE
LAFAYETTE
CO
80026-1250
US
|
Assignee: |
Idalex Technologies, Inc.
Denver
CO
|
Family ID: |
41567411 |
Appl. No.: |
12/506991 |
Filed: |
July 21, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61135640 |
Jul 21, 2008 |
|
|
|
Current U.S.
Class: |
62/259.4 ;
165/133; 165/185; 29/890.03; 62/304 |
Current CPC
Class: |
Y02B 30/54 20130101;
F28F 2245/04 20130101; F28F 13/18 20130101; F28D 5/02 20130101;
F24F 1/0007 20130101; Y10T 29/4935 20150115 |
Class at
Publication: |
62/259.4 ;
165/185; 165/133; 62/304; 29/890.03 |
International
Class: |
F25D 23/00 20060101
F25D023/00; F28F 7/00 20060101 F28F007/00; F28F 13/18 20060101
F28F013/18; F28D 5/00 20060101 F28D005/00; B21D 53/02 20060101
B21D053/02 |
Claims
1. A heat exchanger plate for use in an indirect evaporative
cooling system, the plate comprising: a dry side having low
permeability to an evaporative liquid and formed to allow a product
fluid to flow over a heat transfer area of its surface; and a wet
side designed to have its surface wet by an evaporative liquid, and
formed to allow a working gas to flow over its surface to evaporate
the evaporative liquid; wherein the wet side comprises a
hydrophobic material formed to wick the evaporative fluid.
2. The plate of claim 1, further comprising heat seal strips formed
at an inlet edge and an outlet edge of the plate.
3. The plate of claim 1 wherein the wet side comprises a spun bond
material and the non-permable material comprises an extruded
layer.
4. The plate of claim 3 wherein the spun bond material is
polypropylene and the non-permeable material is
polypropylene/polyethylene.
5. The plate of claim 1, further comprising channel guides to
channel the working gas and the product fluid.
6. The plate of claim 1 wherein the dry side is hydrophilic.
7. An indirect evaporative cooler comprising: a plurality of
generally parallel, spaced apart plates wherein each plate has a
dry side having low permeability to an evaporative liquid and
formed to allow a product fluid to flow over a heat transfer area
of its surface; a wet side designed to have its surface wet by an
evaporative liquid, and formed to allow a working gas to flow over
its surface to evaporate the evaporative liquid; and; wherein the
wet side comprises a hydrophobic material configured to wick the
evaporative liquid; and wherein the plates alternate such that wet
sides face wet sides and dry sides face dry sides.
8. The indirect evaporative cooler of claim 7 wherein the plates
are oriented generally horizontally and further comprise heat seal
strips formed at an inlet edge and an outlet edge of the
plates.
9. The indirect evaporative cooler of claim 7, wherein the plates
further form a trough containing the evaporative fluid between wet
sides.
10. The method of fabricating heat exchanger plates for use in an
indirect evaporative cooling system comprising the steps of: (a)
forming a sheet of material having a dry side of the sheet which
has low permeability to an evaporative liquid and is configured to
allow a product fluid to flow over a heat transfer area of its
surface; and a wet side of the sheet which is hydrophobic and is
configured to wick the evaporative fluid and to allow a working gas
to flow over its surface to evaporate the evaporative liquid; and
(b) cutting the sheets into plates wherein each plate has an inlet
edge opposite an outlet edge;
11. The method of claim 10, further comprising the steps of: (c)
forming wet channels on wet sides of plates generally parallel to
the inlet and outlet edges; and (d) forming dry channels on dry
sides of plates.
12. The method of claim 10 further comprising the step of forming
heat seal strips at the inlet and outlet edges.
13. The method of claim 12 wherein the step of forming wet channels
comprises forming wet channel guides, and wherein a wet channel
guide overlaps the heat seal strip at the inlet edge and a wet
channel guide overlaps the heat seal strip at the outlet edge.
14. The method of claim 10, further comprising the step of forming
perforations in the sheets.
15. The method of claim 14, wherein the step of forming dry
channels comprises forming channel guides generally perpendicular
to the inlet edge and the outlet edge, and where the step of
forming perforations forms perforations in a line perpendicular to
the inlet edge and outlet edge.
16. The method of claim 10 wherein the step of forming further
forms the dry side to be hydrophilic.
Description
BACKGROUND OF THE INVENTION
[0001] U.S. Pat. No. 6,581,402, issued Jun. 24, 2003 is
incorporated herein by reference. U.S. Pat. No. 6,705,096, issued
Mar. 16, 2004 is incorporated herein by reference. U.S. Pat. No.
7,228,699, issued Jun. 12, 2007 is incorporated herein by
reference. This application claims the benefit of U.S. Provisional
Patent Application No. 61/135,640, filed Jul. 21, 2008.
[0002] 1. Field of the Invention
[0003] The present invention relates to plate heat and mass
exchangers for indirect evaporative coolers. In particular, the
present invention relates to improved fabrication materials and
techniques for such plate heat and mass exchangers for indirect
evaporative coolers.
[0004] 2. Discussion of the Background Art
[0005] Indirect evaporative cooling is a method of cooling a fluid
stream; usually air, by evaporating a cooling liquid, usually
water, into a second air stream while transferring heat from the
first air stream to the second. The method has certain inherent
advantages compared to conventional air conditioning: low
electricity requirements, relatively high reliability, and the
ability to do away with the need for refrigerants such as R-134 and
all the disadvantages they entail.
[0006] U.S. Pat. No. 6,581,402 shows a number of embodiments for
indirect evaporative cooling using plate apparatus. FIG. 1 (Prior
art) shows a perspective and schematic representation of two plates
showing the wet side channels formed by the wet sides of a first
and a second plate opposing each other, with their passages
oriented in the same general area and illustrating the working gas
entering on the dry side, passing through the passages and into the
wet side channels. The product fluid is separated from the working
gas as they pass along the dry side of the first and second plates.
Additional plates form a stack, and adjacent plates have their dry
sides facing each other. Thus, the stack of plates would have every
odd plate oriented with its dry side facing the same direction and
opposite of all even plates.
[0007] The invention of U.S. Pat. No. 6,581,402 provides an
indirect evaporative cooler having cross flowing wet and dry
channels on opposite sides of a plurality of heat exchange plates
which allow heat transfer through the plates. The plates include
edge extensions to facilitate the removal of water (or similar
evaporative fluid) and dissolved minerals from the plates.
[0008] For purposes of both U.S. Pat. No. 6,581,402 and the present
application, we wish to define certain terms. Refer to FIG. 1,
(Prior Art).
1. The wet side or wet portion of the heat exchange surface means
that portion having evaporative liquid 22 on or in its surface,
thus enabling evaporative cooling of the surface and the absorption
of latent heat from the surface. 3. The dry side or dry portion of
the heat exchanger means that portion of the heat exchanger surface
where there is little or no evaporation into the adjacent gas or
fluid. Thus, there is no transfer of vapor and latent heat into
adjacent gases. In fact, the surface may be wet but not with
evaporative fluid or wet by condensation, and no substantial
evaporation occurs. 4. The working stream or working gas 2 is the
gas flow that flows along the heat exchange surface on the dry
side, passes through the passages 11 in the surface to the wet side
and picks up vapor and by evaporation, taking latent heat from the
heat exchange surface and transporting it out into the exhaust. In
some embodiments, the working stream may be disposed of as waste
and in others it may be used for special purposes, such as adding
humidity or scavenging heat. 5. The product stream or product fluid
stream 1 is the fluid (gas, liquid or mixture) flow that passes
along the heat exchange surface on the dry side and is cooled by
the absorption of heat by the working gas stream on the wet side
absorbing latent heat by the evaporation in the wet area.
[0009] The plate also has passageways or perforations 11 or similar
transfer means between the dry side of the plate and the wet side
in defined areas providing flow from the dry working channels to
the working wet channels in which direct evaporative cooling takes
place.
[0010] The method makes use of the separation of a working gas flow
2 (that is used to evaporate liquid 22 in the wet channels and thus
to cool the wet surface of the heat exchanger plate) from the
product fluid flow 1, flowing through dry product channels 3 and
dry working channels 4 respectively on the same side of the heat
exchange plate. Both give up heat to the heat exchange plate that
on its obverse surface is being cooled by evaporation in the
working wet channels 5.
[0011] The working gas flow first enters the dry working channel 4
and then through perforations 11, pores or other suitable means of
transfer across the barrier of the plate to the wet side and thence
into the wet working channels 5 where evaporation of liquid on the
wet channel surface cools the plate.
[0012] The dry product channels 3 are on the dry side of this
plate. The plate is of a thin material to allow easy heat transfer
across the plate and thus to readily allow heat to transfer from
the dry product channel to the wet working channel. This is one
basic unit or element of the invention illustrating the method of
the separation of working gas flows to indirectly cool the separate
product fluid by evaporative cooling.
[0013] Many evaporative cooling embodiments include a wicking
material 25 for distributing the water or other evaporative liquid
over the plate wet side. See, for example, FIG. 7 of U.S. Pat. No.
6,581,402, wherein a wicking material 7 distributes the evaporative
liquid along wet side channels 5. Plates 6 form a "V-shape" in the
embodiment of FIG. 7. Water also evaporates better from a wicking
surface than from a water surface, as the wick material breaks down
the surface tension of the water.
[0014] Wicking up a vertical surface will insure no excess water on
the plate surface but also limits the height of the plate that can
be used. Wicking water down a surface aided by gravity may be good
from a wetting perspective if the amount of water does not exceed
what the wick can transport. Wicking in a more horizontal direction
can allow a vertical reservoir wetting system such as shown in U.S.
Pat. No. 6,705,096. There are some plate heat and mass exchanger
applications that require a more innovative geometry that
corresponds to a more complicated thermodynamic design that again
require a more horizontal application such as U.S. Pat. No.
6,581,402. In most cases creating a means to insure that the wick
will not be over run by water is desired.
[0015] U.S. Pat. No. 7,228,699 teaches apparatus and methods for
drawing excess liquid and minerals away from the heat exchanging
portion of the plate, and removing them from the plate. Edge
extensions are added to the plates of indirect evaporative coolers
to allow excess evaporative liquid to migrate to the edges of the
plates and drip off, taking dissolved minerals with it. Better
evaporation and heat transfer are also accomplished.
[0016] The indirect evaporative coolers of U.S. Pat. Nos. 6,581,402
and 7,228,699 work well. But improvements to fabrication techniques
and materials can make the devices work better in some
environments. For example, improved materials properly fabricated
can resist mold and provide better wicking and evaporation.
Therefore, a need remains in the art for to improved fabrication
materials and techniques for plate heat and mass exchangers for
indirect evaporative coolers.
SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to provide improved
fabrication materials and techniques for such plate heat and mass
exchangers for indirect evaporative coolers. An improved process
for fabricating a Dew Point Evaporative Air Conditioner uses the
thermo forming properties of a plastic polymer to create a seal
edge on the inlet and outlet faces of a heat and mass exchanger
plate and optionally around the air passageways between the dry
side of the plate and a wet side. The plastic polymer material
allows the edges to be sealed by melting the fiber material
together eliminating the need for a second sealing material such as
epoxy, as is used in previous manufacturing processes.
[0018] In addition, the improved material uses a hydrophobic
plastic polymer such as polypropylene or a combination of plastic
polymer hydrophobic material bonded to the top of a hydrophilic
material such as a polypropylene spun bond intermingled or on top
of a nylon naturally wicking material, with the hydrophobic
material on the evaporative surface to improve wicking and
evaporation, and retard mold.
[0019] In a preferred embodiment, a surfactant is used to start the
wicking on the hydrophobic layer. The sealing process may be
accomplished using an automated die stamper that heats the sealed
area to the effective temperature and also cuts the sheets to the
desired configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 (prior art) is a perspective and schematic
representation of a plate heat and mass exchanger for indirect
evaporative cooling.
[0021] FIGS. 2A-D illustrate an embodiment of the invention. FIG.
2A is a plan view of a plate according to the present invention.
FIG. 2B is a plan view of a "wet" plate with wet side channels.
FIG. 2C is a plan view of a "dry" plate with dry side channels.
FIG. 2D is a side view of the plates of 2B and 2C.
[0022] FIG. 3 is a flow diagram illustrating a possible fabrication
process for a heat exchange plate according to the present
invention.
[0023] FIG. 4 is a perspective and schematic representation of
another embodiment of the present invention, having slanted edge
extensions.
DETAILED DESCRIPTION OF THE INVENTION
[0024] FIGS. 2 and 4A-D show embodiments of improved fabrication
materials and techniques for heat transfer plates in indirect
evaporative coolers. FIG. 3 shows an example of a fabrication
process according to the present invention. While several
embodiments are shown and discussed, it will be apparent to those
skilled in the art that many other indirect evaporative cooler
plate configurations are possible. U.S. Pat. Nos. 6,581,402,
6,705,096, and 7,228,699, incorporated herein by reference, show a
variety of plate configurations, and others are known as well.
[0025] The following table lists reference numbers used in this
patent:
TABLE-US-00001 1 dry side product fluid (e.g. air) 2 working gas
(e.g. air) 3 dry side product channels 4 dry side working channels
5 wet side channels 6A wet plates 6B dry plates 7A wet channel
guides 7B dry channel guides 9 dry sides of plates 10 wet sides of
plates 11 perforations 18 seals 22 evaporative fluid (e.g. water)
23 trough for wetting plates 24 non-permeable side 25 wicking side
26 trough
[0026] FIGS. 2A-D illustrate an embodiment of the invention. FIG.
2A is a plan view of a plate 6 according to the present invention.
Plate 6 of FIG. 2A does not have channel guides applied, and can be
used as a wet plate or a dry plate. It does have perforations 11
and end seals 18 which are formed at the inlet and outlet ends of
plate 6 (perpendicular to the lines of perforations 11). Note that
perforations 11 are not required in wet plates 6A if they are
provided in dry plates 6B (or vice versa) but may be used in both.
Note also that the term "wet plate" is used to indicate the plates
having channels guides 7A on the wet side of the plate, and the
term "dry plate" is used to indicate the plates having channels
guides 7B on the dry side of the plate. Naturally each plate has a
wet side and a dry side in use. Refer to FIG. 3 and the discussion
of FIG. 3 for a description of how the plates might be
fabricated.
[0027] In one preferred embodiment, plate 6 is formed of a sheet of
hydrophobic polypropylene spun bond material forming a fiber
surface, with a hydrophilic polypropylene/polyethylene extruded
seal layer on the other side. The sheet is about 20''.times.19.5'',
and 0.01'' thick. The spun bond acts as a wicking material 25. The
evaporative rate off of a hydrophobic woven or spun bond material
is higher than for a hydrophilic material, resulting in about the
same temperatures but with 1/3 higher air flow rates than previous
indirect evaporative coolers. The polypropylene/polyethylene
extruded seal layer forms the non-permeable side 24 of the sheet.
Seals 18 are formed by heat staking, or applying heat to melt the
fibers.
[0028] FIG. 2B is a plan view of a wet plate 6A with wet side
channels 5. Seals 18 were formed at the inlet and outlet ends of
plate 6A. Channel guides 7A run perpendicular to the seals 18, and
the channel guide at each end is formed on top of the seal at that
end. In this embodiment, the wet channel spacing (between plates)
is about 0.09'', and the distance between the channel guides is
about 1''. Since the hydrophobic wicking material 25 will not hold
or absorb water naturally, the wet channel spacing can be less than
half that of previous indirect evaporative coolers without the wet
channels filling up with water and preventing air flow. Wet channel
spacing can also be larger if desired for air flow.
[0029] FIG. 2C is a plan view of a dry plate 6B with dry side
(non-permeable side 24) product channels 2 and dry side working
channels 3. Dry channels 2, 3 run parallel to the lines of
perforations 11, and perpendicular to end seals 18. In this
embodiment, dry channel spacing is about 0.14'' and the distance
between channel guides 7B is about 1''.
[0030] FIG. 2D is a side view of a plate 6A of FIG. 2B and a plate
6B of FIG. 2C, shown in a stacked configuration as they would be
used in an indirect evaporative cooler, but exploded to show
detail. Wet plate 7A includes perforations 11 aligned with working
channels 4. Plates 6A and 6B have been formed into V-shaped troughs
to provide evaporative fluid 22 to wet the wet sides of the
plates.
[0031] FIG. 3 is a flow diagram illustrating a possible fabrication
process for a heat exchange plate according to the present
invention. In step 302, sheets of the material for plate 6 are
formed. As discussed with respect to FIG. 2A, plate 6 may be formed
of a sheet of hydrophilic polypropylene spun bond material forming
a fiber surface, with a hydrophobic polypropylene/polyethylene
extruded seal layer on the other side. The spun bond acts as a
wicking material 25. The polypropylene/polyethylene extruded seal
layer forms the non-permeable side 24 of the sheet. In this case,
the material is formed in two steps. First the spun bond fiber
(wicking material 25) is formed. Second, a poly film is extruded on
one side to form non-permable side 24.
[0032] The evaporation rate off of hydrophobic woven or spun bond
material where water has been impregnated in between the fibers is
higher then from a hydrophilic material where water has been
absorbed into the material and between the fibers. This means that
a much smaller temperature difference across the plate is required
to achieve the same evaporation rate to take place, which therefore
increases the heat transfer rate. Practically this means the
indirect evaporative cooler of the present invention can realize
the same temperature output with 1/3 higher air flow rates when
using a hydrophilic polymer material. At the same time this
hydrophobic material has the benefit of being able to wick water at
a much faster rate as it does not absorb the water or hold onto the
water; rather it allow it to quickly pass through the fibers.
[0033] Note that because the material is hydrophilic it will not
naturally start the wicking process or absorb water, which may
create the need for a wetting agent such as a surfactant to start
the wicking. Air flow may also be used to help drive the water into
the fibers. After the wicking is started it will continue to wick
long after the surfactant has washed out, as long as the polymer
wicking material is not allowed to run out of water to wick. To
restart wicking after the wicking material has dried out,
surfactant may be added to the evaporative fluid 22 for a brief
period. The surfactant may be a detergent or hand soap or dish
washing soap such as Dawn Ultra.TM..
[0034] Using this hydrophobic polymer material in a dew point
evaporative cooler allows for thinner or less weight of material,
lower product temperatures and higher air flow rates to be derived
with the same surface area and air properties when compared to
previous dew point evaporative coolers.
[0035] In step 304 plates 6 are cut from the material. In step 306,
perforations are formed. In step 308, seal are added at the inlet
and outlet ends of plates 6. In a preferred embodiment, an auto die
cutter is used for steps 304-308. The die cutter uses a hot cutting
surface, meaning that a narrow seal is formed on all of the edges
and around the perforations as the plates are cut out. Seal strips
18 are also formed by the die cutter, by pressing the material
between two plates, one of which is heated to about 320.degree. F.
The seal strips are about 1/4'' wide.
[0036] In steps 310 and 312, channel guides are added to the plates
6B and 6A as showns in FIGS. 2B and 2C. The channel guides are
formed by laying down hot melt glue with an automated machine for
consistency to get the desired location, channel height and
attachment between plates. In step 314, the plates are stacked,
alternating between dry plates and wet plates as shown in FIG. 2D.
In the embodiment of FIGS. 4A-D, in step 316 a trough is formed in
the centers of the plates for example by fitting the plates into a
shaped cassette
[0037] FIG. 4 is a perspective and schematic representation of
another embodiment of the present invention, having slanted edge
extensions. This embodiment is very similar to that of FIGS. 2A-2D,
and much of the description is applicable here. Again seal strips
18 are formed at the inlet and outlet of the plates 6. Wet channel
guides 7A are formed parallel to the seals, with the end guides
overlapping the seals. Dry side channel guides 7B are formed
perpendicular to the wet side channel guides.
[0038] Those skilled in the art of indirect evaporative cooling
systems will recognize various changes and modifications which can
be made to the exemplary embodiments shown and described above,
which are still within the spirit and scope of the invention.
* * * * *