U.S. patent application number 11/081397 was filed with the patent office on 2005-09-29 for indirect evaporative cooling of a gas using common product and working gas in a partial counterflow configuration.
Invention is credited to Gilan, Alan D., Gillan, Leland E., Gillan, Rick J., Maisotsenko, Valeriy.
Application Number | 20050210907 11/081397 |
Document ID | / |
Family ID | 34963462 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050210907 |
Kind Code |
A1 |
Gillan, Leland E. ; et
al. |
September 29, 2005 |
Indirect evaporative cooling of a gas using common product and
working gas in a partial counterflow configuration
Abstract
An indirect evaporative cooler includes a number of heat
transfer plates. Each plate has a wet side and a dry side, and the
dry sides of adjacent plates face each other. The plate dry sides
have low permeability to an evaporative liquid. Input air flows
over the dry sides from an input end to an output end. Part of the
input air becomes product air and exits at the output end. The rest
of the input air passes through perforations in the plates to the
other side of the plates to become working air. The other side of
each plate is a wet side, which is wet by an evaporative liquid.
Working gas flows over the wet side, evaporating the evaporative
liquid and cooling the evaporative liquid, the plate, and finally
the product gas by heat transfer. The perforations are formed both
toward the input end of the plate and toward the output end of the
plate. Part of the wet side of the plate, toward the output end of
the plate, has a plurality of barriers placed to cause the working
gas at that end of the plate to flow in a direction generally
counter to the input air.
Inventors: |
Gillan, Leland E.; (Denver,
CO) ; Maisotsenko, Valeriy; (Aurora, CO) ;
Gilan, 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
|
Family ID: |
34963462 |
Appl. No.: |
11/081397 |
Filed: |
March 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60553875 |
Mar 17, 2004 |
|
|
|
Current U.S.
Class: |
62/304 ;
62/314 |
Current CPC
Class: |
F24F 5/0035 20130101;
F24F 1/0059 20130101; F24F 1/0007 20130101; Y02B 30/54 20130101;
F28D 5/02 20130101; F28D 5/00 20130101 |
Class at
Publication: |
062/304 ;
062/314 |
International
Class: |
F25D 017/06; F28D
005/00 |
Claims
What is claimed is:
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 an input
fluid to flow over its surface from an input end to an output end;
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 perforations formed in the
plate to allow a portion of the input fluid to pass from the dry
side to the wet side, the perforations placed both toward the input
end of the plate and toward the output end of the plate; wherein a
portion of the wet side toward the input end of the plate forms
channels for guiding the working air which passes through the
input-end perforations in a direction generally transverse to the
product air flow; and wherein a portion of the wet side toward the
output end of the plate further includes a plurality of barriers
placed to cause the working air from the output-end perforations to
flow in a direction generally counter to the product air.
2. The plate of claim 1 wherein the channels are generally
perpendicular to the flow of input air.
3. The plate of claim 1, wherein the barriers are elongated.
4. The plate of claim 3 wherein the barriers are oriented generally
perpendicular to the input airflow.
5. The plate of claim 1 wherein the dry side further forms channels
to guide the input air from the input end toward the output
end.
6. The plate of claim 1 wherein the output-end perforations include
output-end side-perforations along a side parallel to product air
flow and output-end edge-perforations along an edge where the
product air exits.
7. The plate of claim 1 wherein the barriers cause the working gas
at the output end of the plate to flow in a circuitous route.
8. 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 an input gas to flow over its surface from an input
end to an output end, 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
perforations formed in the plate to allow a portion of the input
gas to pass from the dry side to the wet side, the perforations
placed both toward the input end of the plate and toward the output
end of the plate, wherein the dry sides of adjacent plates face
each other, and wherein a portion of the wet side toward the output
end of the plate further includes a plurality of barriers placed to
cause the working gas from the perforations toward the output end
of the plate to follow a counter flow path to the input gas; and
means for providing input gas at the input side of the plates and
exiting product gas at the output side of the plates; and means for
exiting working gas.
9. The evaporative cooler of claim 8, wherein the channels are
generally perpendicular to the flow of input air.
10. The plate of claim 8, wherein the barriers are elongated.
11. The plate of claim 10 wherein the barriers are oriented
generally perpendicular to the input airflow.
12. The plate of claim 8 wherein the dry side further forms
channels to guide the input air from the input end toward the
output end.
13. The plate of claim 8 wherein the output-end perforations
include output-end side-perforations along a side parallel to
product air flow and output-end edge-perforations along an edge
where the product air exits.
14. The plate of claim 8 wherein the barriers cause the working gas
at the output end of the plate to flow in a circuitous route.
Description
[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. patent
application Ser. No. 11/061,124, filed on Feb. 18, 2005, entitled
"Plate Exchanger Edge Extension" is incorporated herein by
reference. This application claims the benefit of U.S. Provisional
Patent Application No. 60/553,875, filed Mar. 17, 2004
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to indirect evaporative
coolers. In particular, the present invention relates to such
coolers configured to utilize common product and working gas, with
part of the working gas flowing in a counter-direction to the
product gas.
[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.
[0008] For purposes of the present application, we wish to define
certain terms:
[0009] 1. Heat transfer surface or heat exchange surface has many
configurations. All are encompassed within the subject of this
disclosed invention with appropriate adjustment to the wetting and
flows as are well known in the industry. For illustration we make
use of a plate configuration.
[0010] 2. Wet side or wet portion of the heat exchange surface
means that portion having evaporative liquid on or in its surface,
thus enabling evaporative cooling of the surface and the absorption
of latent heat from the surface.
[0011] 3. 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.
[0012] 4. Working stream or working gas stream is the gas flow that
flows along the heat exchange surface on the dry side, passes
through the passages 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.
[0013] 5. Product stream is the gas 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.
[0014] The plate also has passageways or perforations 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.
[0015] The method of the invention makes use of the separation of a
working gas flow (that is used to evaporate liquid in the wet
channels and thus to cool the wet surface of the heat exchanger
plate) from the product fluid flow, flowing through dry product
channels and dry working channels 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.
[0016] The working gas flow first enters the dry working channel
and then through perforations, pores or other suitable means of
transfer across the barrier of the plate to the wet side and thence
into the wet working channels where evaporation of liquid on the
wet channel surface, cools this plate.
[0017] The dry product channels 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.
[0018] The indirect evaporative cooler of U.S. Pat. No. 6,581,402,
in which the product and working air are kept separate works well.
However, in some applications, there is an advantage to using a
portion of the product gas as working gas to reduce the total
amount of working and product gas combined such as in desiccant
air-drying applications. When air is dried with a desiccant
moisture absorbing system, the desiccant must be regenerated or
have the moisture it absorbed removed generally by heating the
desiccant and driving the moisture off. Thus, desiccant-dried air
is expensive to be using to cool the product air.
[0019] A need remains in the art for a design using common product
and working gas, and allowing some of the cooler exhaust air to be
placed in counter flow with the product air.
SUMMARY OF THE INVENTION
[0020] It is an object of the present invention to provide
apparatus and methods for indirect evaporative cooling devices
which use a common product gas and working gas and provide for some
of the working gas to flow in a direction counter to the product
gas.
[0021] Counter flow increases the temperature of the working gas by
passing it in heat exchange first with the coldest product air then
with warmer product air. A higher exhaust temperature will allow
the air to hold much more evaporate increasing the latent heat load
of the working air considerably. The resulting higher enthalpy of
the exhaust air means that considerably less working air is needed
while maintaining low product air temperatures.
[0022] A heat exchanger plate for use in an indirect evaporative
cooling system has a dry side having low permeability to an
evaporative liquid and formed to allow an input fluid to flow over
its surface from an input end to an output end, 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. Perforations are formed in the plate to
allow a portion of the input fluid to pass from the dry side to the
wet side, the perforations placed both toward the input end of the
plate and toward the output end of the plate. A portion of the wet
side, toward the input end of the plate, forms channels for guiding
the working air which passes through the input-end perforations in
a direction generally transverse to the product air flow. Another
portion of the wet side, toward the output end of the plate,
includes a plurality of barriers placed to cause the working air
from the output-end perforations to flow in a direction generally
counter to the product air.
[0023] The channels are generally perpendicular to the flow of
input air. The barriers are elongated, and are oriented generally
perpendicular to the input airflow. Generally the barriers cause
the working gas at the output end of the plate to flow in a
circuitous route.
[0024] Preferably the dry side forms channels to guide the input
air from the input end toward the output end.
[0025] In a preferred embodiment, the output-end perforations
include output-end side-perforations (along a side parallel to
product air flow) and output-end edge-perforations (along the edge
where the product air exits).
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 (Prior Art) is an isometric illustrating a
conventional indirect evaporative cooler configuration.
[0027] FIG. 2 is a plan view of the dry side of a heat transfer
plate used in an evaporative cooler according to the present
invention.
[0028] FIG. 3 is a plan view of the wet side of a heat transfer
plate used in an evaporative cooler according to the present
invention.
[0029] FIG. 4 is a side view of three heat transfer plates of FIGS.
3 and 4, in parallel configuration.
DETAILED DESCRIPTION OF THE INVENTION
[0030] FIGS. 2-4 illustrate one embodiment of an indirect
evaporative cooler wherein part of the product gas is used as
working gas. Note that while the term "air" is frequently used in
the following description, others types of gas may be used as well,
so long as the same kind of gas is used for the product gas and the
working gas. The following table lists reference numbers used in
this patent:
1 1 output product gas 2 output working gas 3 wet side paths 4 dry
side channels 5 wet side channels 6 plates 7 channel guides 8 wick
material 9 dry sides of plates 10 wet sides of plates 11 input end
side perforations 12 Input common product and working air 13 output
end side perforations 14 output end edge perforations 15 wet side
path barriers
[0031] FIG. 2 is a plan view of the dry side 9 of a heat transfer
plate 6 used in an evaporative cooler according to the present
invention. Combined product and working air 12 enters dry side
channels 4 from the left of the figure. Channels 4 are generally
formed with a series of parallel channel guides 7. A portion of
input gas 12 exits as cooled product gas 1, at the right of the
figure. Generally between 1/2 and 3/4 of input air 12 exits as
product air 1. The rest passes through perforations 11, 13, and 14
and operates as working air on the wet side 10 of the plate 6.
[0032] Perforations 11 are formed on the input side of the plates,
along the side of the plate between 1/4 to 1/2 the length of the
plate. Perforations 13 are formed on the product output side of the
plates in areas that best allow air flow distribution across and in
counter flow on the wet side. Perforations 14 are formed on the
product output edge of the plate.
[0033] FIG. 3 is a plan view of the wet side 10 of heat transfer
plate, working air 2 from the dry side of plate 6 comes through
perforations 11, 13, and 14. An evaporative fluid (not shown) is
evaporated into working air 2, cooling heat transfer plate 6. This,
in turn, cools product air 1. Often a wicking material 8 (see FIG.
4) is used to thoroughly distribute the evaporative fluid on wet
side 10.
[0034] The portion of working air 2 arriving through input-end
side-perforations 11 pass across plate 6 via parallel wet side
channels 5, generally perpendicular to input air 12. Channels 5 are
generally formed by channel guides 7. The portion of working air
coming through output-end side-perforations 13 and output-end
edge-perforations 15 follow more circuitous paths 3, but generally
move in a direction counter to the product flow. Barriers 15 are
short channel guides that provide airflow direction and separation
of plates. Barriers 15 are scattered on this portion of the plate
to force working air 2 to wind its way among them in a direction
generally counter to the product air flow and to provide structure
to the heat exchanger. Generally barriers 15 are elongated
generally parallel to wet side channel guides 7, as this provides
structural strength (because barriers 15 are then perpendicular to
dry side channel guides 7). However, the configuration and
orientation of the barriers may be varied.
[0035] FIG. 4 is a side view of three heat transfer plates 6, in
parallel configuration. FIG. 4 illustrates a very small evaporative
cooler, though generally many more plates will be used. In a more
practical embodiment of an indirect evaporative cooling system
(described here by way of an example), 80 plates are stacked in a
10 inch high stack. The dimensions of the plates are 20 inches by
18 inches. The plate material is polyethylene coating on cellulose
fiber paper (the paper acts as a wicking material). The spacing
between the plates is 0.125 inches.
[0036] Each plate 6 has a wet side 10 and a dry side 9. The dry
sides of adjacent plates face each other. Often a wicking material
8 is used to distribute the wet side evaporative fluid.
[0037] Input combined product and working air 12 enters between two
dry sides 9. The portion of input air 12 that comes out the other
end of the plates as product air 1 remains dry. The rest of input
air 12 passes through perforations 11, 13, 14 as shown in FIGS. 2
and 4 to become working air 2. The portion of working air 2 coming
through input-end side-perforations 11 is guided by channel guides
7 straight across plates 6. This portion of working air 2 in is
crossflow to the product air 1. The portion of working air 2 coming
though output-end side-perforations 13 and output-end
edge-perforations 14 passes among barriers 15. This portion of
working air 2 is in counterflow to product air 1.
[0038] This counterflow increases the temperature of working gas 2,
allowing it to hold more evaporate and therefore have a higher
enthalpy, thus using considerably less air while maintaining low
product air temperatures. The partial counterflow configuration of
the present invention requires a larger exhaust pressure drop than
a pure crossflow configuration, but less than a pure counterflow
configuration.
[0039] 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.
* * * * *