U.S. patent application number 10/247066 was filed with the patent office on 2003-01-23 for method and apparatus of indirect-evaporation cooling.
Invention is credited to Gillan, Alan D., Gillan, Leland E., Heaton, Timothy L., Maisotsenko, Valeriy.
Application Number | 20030014983 10/247066 |
Document ID | / |
Family ID | 26915637 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030014983 |
Kind Code |
A1 |
Maisotsenko, Valeriy ; et
al. |
January 23, 2003 |
Method and apparatus of indirect-evaporation cooling
Abstract
The within invention improves on the indirect evaporative
cooling method and apparatus by making use of a working fluid that
is pre-cooled with and without desiccants before it is passed
through a Wet Channel where evaporative fluid is on the walls to
take heat and store it in the working fluid as increased latent
heat. The heat transfer across the membrane between the Dry Channel
and the Wet Channel may have dry, solid desiccant or liquid
desiccant and may have perforations, pores or capillary pathways.
The evaporative fluid may be water, fuel, or any substance that has
the capacity to take heat as latent heat. The Wet Channel or excess
cooled fluid is in heat transfer contact with a Product Channel
where Product Fluid is cooled without adding any humidity. An
alternative embodiment for heat transfer between adjacent channels
is with heat pipes.
Inventors: |
Maisotsenko, Valeriy;
(Aurora, CO) ; Gillan, Leland E.; (Denver, CO)
; Heaton, Timothy L.; (Arvada, CO) ; Gillan, Alan
D.; (Denver, CO) |
Correspondence
Address: |
DORR CARSON SLOAN & BIRNEY, PC
3010 EAST 6TH AVENUE
DENVER
CO
80206
|
Family ID: |
26915637 |
Appl. No.: |
10/247066 |
Filed: |
September 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10247066 |
Sep 19, 2002 |
|
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|
09916800 |
Jul 27, 2001 |
|
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60221264 |
Jul 27, 2000 |
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Current U.S.
Class: |
62/121 ;
62/309 |
Current CPC
Class: |
F28D 5/02 20130101; Y02B
30/54 20130101; F24F 1/0059 20130101; F24F 5/0035 20130101; F24F
1/0007 20130101 |
Class at
Publication: |
62/121 ;
62/309 |
International
Class: |
F28C 001/00; F25D
017/04 |
Claims
1. A method of indirect-transpiration cooling, which comprises: a)
passing a Product Fluid in a product channel; b) Having a surface
with said product channel, having a wall created by a first side of
a first membrane, c) Having a Dry Channel with one of its walls
being a first side of a second membrane, d) Having a Wet Channel
comprised of at least two walls, one being the second side of the
first membrane and the second being the second side of the second
membrane, e) Having the walls of the Wet Channel being supplied
with evaporative liquid, f) Passing working fluid first through the
Dry Channel, and then in counter flow to this direction, through
the Wet Channels, g) Having a heat exchange mechanism between the
Working Fluid in the Wet Channel, and the Product Fluid in the
Product Channel, h) Having a heat exchange mechanism between the
working fluid in the Dry Channel and the Wet Channel.
2. A method according to claim 1, wherein the Working Air flow is
being induced from the Wet Channel.
3. A method according to claim 2, wherein a pressure drop is
created between the Dry and Wet Channels.
4. A method according to claim 1, wherein the Working Air path
along the Dry Channel wall is not equal to that along the Wet
Channel wall.
5. A method according to claims 1, a Product Heat Exchanger
exchanges heat between the Product and excess Evaporative fluid
from the Wet Channel.
6. A method according to claims 1, wherein a liquid desiccant flows
over the Dry Channel wall of the second membrane.
7. A method according to claim 6, wherein liquid desiccant, after
its passing over the Dry Channel, is directed outside the apparatus
for regeneration, and subsequent reuse.
8. A method according to claim 1, wherein the second membrane is
porous between the Dry and Wet Channels to allow working fluid to
pass.
9. A method according to claim 1, wherein some part of the Working
Air, after passing through tile Dry Channel, is withdrawn and used
as the Product Fluid being cooled.
10. A method according to claim 1, wherein the walls of the second
membrane of the Dry Channels has solid desiccant material.
11. A method according to claim 1 wherein at least one of the walls
of the Wet Channel are wetted by liquid desiccant.
12. A method according to claim 1, wherein the Evaporative Liquid
is a liquid fuel that wets the Wet Channel.
13. A method according to claim 13, wherein the Working Air passing
through the Wet Channel creates a fuel-air mixture which is
directed to an internal combustion engine.
14. A method according to claim 1, wherein exhaust gas from an
engine is used to heat the Working Air before it enters the Wet
Channel.
15. A method according to claim 7, the regenerator, uses heat of
exhaust gas of an engine.
16. A method according to claim 12 wherein water is added to fuel
and is used as the Evaporative Liquid in the Wet Channel.
17. A method according to claim 1, wherein the heat exchange
surfaces mechanism are one or more heat pipes, with evaporator
section located in the Dry Channel and condenser section in the Wet
Channel, and evaporation section in the Product Channel and the
condensation section in the Wet Channel.
18. A method according to claim 1, wherein the Evaporative Liquid
is a liquid desiccant which is on the Wet Channel walls.
19. A method according to claim 18, wherein the Working Air, before
passing along the Dry Channel, is exposed to the liquid desiccant,
and then this liquid is directed to the Wet Channel as the
Evaporative Liquid.
20. A method according to claim 18, wherein the liquid desiccant is
re-circulated to the Wet Channel.
21. A method according to claim 19, wherein at least some part of
the Working Air, after its contact with a desiccant is directed to
the Dry Channel, and the remainder is used for Product air.
22. A method according to claim 18, wherein at least some of the
liquid desiccant after its passing along the Wet Channel, is
directed to the Dry channel, and at least some of the liquid
desiccant after it's passing along the Dry Channel, is directed to
the Wet Channel.
23. A method according to claim 1, wherein the Product Fluid, after
cooling is transported to an apparatus for cooling of another
material.
24. A method according to claim 1, wherein the Evaporative Liquid
is heated.
25. A method according to claim 1, wherein the Working Air is
heated.
26. A method according to claim 1, wherein the direction of
movement of the fluids runs by a means other than counter flow
between the flow in the Wet Channel and the Dry Channel and the
Product Channel.
27. A method, according to claim 1 wherein Working Air is
redirected from the Dry Channel into and through the Wet Channel,
through a plurality of spaced perforations or pores formed in the
second membrane.
28. A heat exchange apparatus wherein: a) There is a means to cool
working fluid by evaporation of an evaporative liquid, b) A means
to conduct heat from a product fluid to the working fluid, c) A
means where Dry working fluid, before it starts evaporating the
evaporative fluid, is pre cooled by heat transfer with the working
fluid that is cooling by way of evaporating of an evaporative
liquid.
29. A heat exchange apparatus comprising: a) A jacket containing
separate passages for Working Fluid and Product Fluid, b) Inlet and
outlet for Working Fluid c) Inlet and outlet for Product Fluid, d)
Working fluid passes through a first passage, with a Dry Channel
first, and a second Wet Channel, e) The Product Fluid passage
shares a first membrane with the Wet Channel part of the Working
Fluid passage, the first side is one wall of the product passage
way, and the opposing second side is one wall of the Wet Channel,
f) A second membrane separates the Dry Channel from the Wet Channel
of the Working Fluid passageway, g) A communication passageway for
the Working Fluid from the Dry Channel to the Wet Channel, h) At
least one wall of the Wet Channel is supplied with an evaporative
liquid, i) The flow of the Working Fluid in tile Dry Channel is
counter to the flow of the Working Fluid in the Wet Channel, j) The
flow of the Product Fluid is counter to the flow of the Working
Fluid in the Wet Channel, k) Having a heat exchange mechanism
between the Dry Channel and the Wet Channel, l) Having a heat
exchange mechanism between the Product Channel and the Wet
Channel.
30. The apparatus of claim 29 wherein the heat transfer mechanisms
are the first and second membrane.
31. The apparatus of claim 29 wherein the heat transfer mechanisms
are heat pipes.
32. The apparatus of claim 29 wherein the evaporative liquid is
fuel.
33. The apparatus of claim 29 wherein the evaporative liquid is
liquid desiccant.
34. The apparatus of claim 29 wherein the second membrane is solid
desiccant.
35. The apparatus of claim 29 wherein the Product Channel is
separate and passes in heat transfer connection with an excess
evaporative liquid from the Wet Channel.
36. The apparatus of claim 29 wherein there are more than one set
of Dry, Wet and Product Channels.
37. The apparatus of claim 29 wherein the evaporative liquid is
fuel with water.
38. The apparatus of claim 29 wherein the evaporative liquid is
liquid desiccant which first flows over the Dry Channel side of the
second membrane.
39. The apparatus of claim 29 wherein the working fluid is heated
before it enters the Wet Channel.
40. The apparatus of claim 29 wherein the membranes have multiple
passageways for fluid to pass from the Dry Channel to the Wet
Channel.
Description
[0001] The applicant claims priority of Provisional patent
application Serial No. 60/221,264, filed Jul. 27, 2000, entitled
"METHOD OF INDIRECT-EVAPORATION COOLING", inventors, Valeriy
Maisotsenko, et al.
FIELD OF INVENTION
[0002] 1. The present invention relates to methods of
indirect-evaporation cooling of fluids and to heat exchange
apparatus for affecting these methods.
[0003] 2. The invention can be used for air conditioning, as well
as cooling liquids and gases in different technological processes.
It can be used to cool materials that can be conveyed along the
heat transfer surfaces of the apparatus by methods other than
fluidization.
BACKGROUND
[0004] The use of Evaporative methods to cool gases is well-known.
The use of adjacent channels or heat transfer services to allow an
evaporation in one channel to provide cooling for material in the
second channel is also well-known, see. Niehart U.S. Pat. No.
2,174,060.
[0005] The methods and apparatus to cool air through evaporation
have proved useful over many years. However they have certain
drawbacks and limitations due to their designs.
[0006] There is known in the art a method of indirect-evaporation
cooling of air, comprising cooling the flow of outside air over a
heat exchange apparatus (USSR Patent No. 979796). The outside air
is pushed over a heat transfer surface, or moisture proof plates of
the Dry Channel. The apparatus is comprised of a number of vertical
moisture-proof plates which divides alternately Dry Channels and
Wet Channels. At the outlet from the Dry Channel the flow of air is
divided into two flows, namely, the cooled product flow and working
flow to the evaporation or wet channel. The cooled flow goes to the
consumer, and the evaporative flow is directed in counter flow of
the Dry Channel, in the Wet Channel. The flows are controlled by
the creation of aerodynamic resistance at the Dry Channel outlet.
The heat transfer between the dry and Wet Channels causes heat to
be drawn out of the outside air in the Dry Channel across the heat
transfer surface and into the evaporation of the water in the Wet
Channel. Cooling the air by the heat transfer surface occurs from
the inlet of the Dry Channel to the exit. This allows air
temperatures at the end of the Dry Channel to approach the dew
point temperature of the air entering the Dry Channel.
[0007] The essential disadvantages of the described method and the
apparatus for effecting same are: 1) the Product Fluid can not be
cooled even in an ideal case lower than the temperature of tile dew
point of outside air; 2) the impossibility of cooling materials
other than air or gas and; 3) difficult to realize cooling process
for use in vehicles.
[0008] In addition to the above indirect-evaporation cooler there
is a conceptual method and design apparatus for Evaporating and
Cooling Water disclosed in Maisotsenko patent USSR Patent No.
690271 and USSR Patent No. 641260 where by single pass of air is
used to cool water. In this method and apparatus the outside air
flow is pushed down a Dry Channel with a heat transfer surface
between the dry and wet channels and turned 180 degrees at the end
of the channel and pushed up in counter flow across the water
wetted heat transfer surface. Evaporation of water from the Wet
Channel then draws heat across the heat transfer surface cooling
the air in the Dry Channel and also cooling the water in the Wet
Channel. Enough water is drawn over the Wet Channel to allow
evaporation and collection of cooled water at the bottom of the
channel which becomes the cooled product. Cooling the air in the
Dry Channel allows for water temperatures at the bottom of the
channel to approach the dew point temperature of the outside
air.
[0009] The essential disadvantages of the described method and the
apparatus for effecting same are: 1) the water being cooled can not
be cooled even in an ideal case lower then the dew point
temperature of outside air; 2) The ability to cool only water; 3)
This process does not use an induced draft exhaust system and; 4)
The description of the materials and accessories needed to design
and make the cooler make for impractical application.; 5) Cooling
potential of this evaporation process is limited; 6) The heat
transfer rate in the channels, especially the Dry Channels is
low.
[0010] Rotenberg U.S. Pat. No. 5,187,946, which is copied from
Russian patent 2046257 Maisotsenko, there is disclosed a Wet-Dry
Channel heat exchange system with an evaporative cooler. This does
not address the issues of the limitation of ambient air, the
limited efficiency of this design or the separate product channel
being cooled by the wet channel.
[0011] The use of desiccants in evaporative coolers is common, see
Belding U.S. Pat. No. 6,050,100, where the desiccant dehumidifies
the air, both the air that goes to a dry side of an indirect
evaporative cooler and the air that is separated and sent to the
wet side to evaporate the water and cool the dry side air flow for
later use. The desiccant is by way of a desiccant wheel.
Additionally, the use of the desiccant and separately treating the
two air streams in Belding yields a primary stream for the dry side
that is more humid and cooler than the drier and warmer secondary
stream that is used for the wet side.
[0012] Unlike the disclosed invention herein, Belding does not use
the same flow for the dry and wet side flows. As a result, the
cooling is not great and there is no separation of product so only
air can be cooled. Finally, the method requires complex components
and separate treatment of the flows with added mechanics and energy
requirements.
[0013] Lowenstein in U.S. Pat. No. 5,351,497 and his paper on
"Seasonal Performance of a Liquid Desiccant Air Conditioner" ASHRAE
Symposia 1995 makes use of liquid desiccant on the dry side of an
indirect evaporative cooler. Similar to Belding, the dry side air
is separate and is the cooled product air.
[0014] Lowenstein uses the liquid desiccant to dehumidify the
desired air flow for a living area, and the evaporative cooling is
used to aid in absorbing the latent heat that is released by the
dehumidification.
[0015] Lowenstein's absorber, throughout makes use of liquid
desiccant for dehumidifying air, does not make use of the unique
feature of the within application. It does not give the advantages
of lower temperature and controlled humidity.
[0016] Separate absorbers, using liquid desiccants were also
discussed in Martinez and Khan, "Heat and Mass Transfer Performance
Analysis of a Compact, Hybrid Liquid Desiccant Absorber", 1996
IEEE. The discussion teaches a result contrary to the within
disclosure that such an absorber could not be used alone to
condition and cool air for living space.
[0017] The objectives of this invention is to make an improved
method and apparatus for evaporation of a liquid to provide cooling
for gases, liquids or other materials. The invention allows for
cooling to a lower temperature than other methods. Its further
objective is to make use of the cool product gas flow to cool other
materials in an improved way without adding vapor or humidity to
the product.
[0018] Further objectives of the invention is to make use of drying
agents or desiccants to enhance the efficiency of the invention and
its ability to cool. A further innovation is to male use of solid
desiccants on a membrane or substrate to allow transpiration of
vapor and fluid that is absorbed in the dry channel by the
desiccants and then released in the wet channel by evaporation
processes and thus cool the membrane and the dry channel.
[0019] The water vapor transpires through the solid desiccant and
membrane.
[0020] Additional objects of the invention are to allow the
desiccants to be concentrated and recycled to provide more
efficiency to the cycle. The invention uses the recycling of the
desiccant in combination with the use of the desiccant as part of
the wet channel to accomplish both objects.
SUMMARY OF INVENTION
[0021] The main object of the invention is to provide an economical
and environmentally safe method of cooling by indirect-evaporation
and heat exchange apparatus, wherein the Product Fluid can be
cooled to or lower than the dew point temperature of outside air.
The object set forth is solved in different ways by using a core
piece of heat and mass exchange apparatus in combination with the
cooling process or processes that are desired. This core piece of
apparatus can deliver cooling fluid by either producing cooled
liquid or cooled gas.
[0022] The core of the apparatus passes Working Air along a Dry
Channel with one side of a heat exchange membrane, then turns the
flow 180 degrees and passes this same flow along a Wet Channel in
counter flow with the same heat transfer membrane but on its
opposite side. Evaporation cooling in the Wet Channel cools the
Working Air in the Dry Channel. The Product to be cooled can be: 1.
By the passing of the Product to be cooled through a third channel
in heat transfer contact with the Wet Channel. 2. An excessive
amount of Evaporative Liquid, (being drained off after cooling and
passed through a Product Heat Exchanger like water, liquid
desiccant, or liquid fuel 3, or other volatile liquid under the
applicable pressures). A portion of the Working Air may be drawn
out of the apparatus and used directly as a Product.
[0023] The unit can be built in a bank of channels. When the
Product to be cooled is set in a channel along side the Wet
Channel, it may also be in heat transfer contact with tile Dry
Channels due to the succession of units.
[0024] The fluid exiting the Wet Channel surface is considered the
Exhaust. The difference in the total energy between the Working Air
entering the Dry Channel and leaving the Exhaust is the Product
cooling energy available. This is generally measured by the
difference in enthalpy and flow. The Exhaust enthalpy is ideally
limited by the Working Air temperature entering the Dry Channel at
its corresponding saturation enthalpy.
[0025] The importance of pre-cooling the air before turning it to
the Wet Channel and then obtaining lower temperatures can be
understood by realizing that the Wet Channel Working Air starts at
the lowest temperature attained in the Dry Channel, generally
approaching the dew point temperature of the outside air. Before
the Working Air enters the Dry Channel it's temperature is
generally at the outside air temperature. In all
indirect-evaporation cooling apparatus for cooling outside air,
other than described here, Working Air (used in evaporation) and
product air temperatures start at the same point, the outside air
temperature, forcing the temperature to approach the higher wet
bulb temperature rather than the dew point temperature. Much lower
temperatures can be realized with the use of desiccants to dry air
in the Dry Channel, or by pre-cooling before going to evaporation
as set out here, and lower the dew point temperature
attainable.
[0026] The main differences between this apparatus and method and
previous art are: 1. The means to create a workable method that
will function in industry that is both efficient and economical to
manufacture. 2. The wide use of fluid types in all channels. The
Evaporative Liquid used in the Wet Channel for transpiration
cooling can be any thing that will evaporate into the air under the
ambient pressure and temperature. The Dry Channel and or the
Product Channel of this method can also be a drying channel with
the use of a desiccant on the heat exchange surface, or on a
different surface within the Dry or Product channel, either liquid
or solid to dry the air out while being cooled at the same time.
This core design allows for many different types of fluids to be
used and effective cooling at low cost. 3. The core method allows
for a wider variety in design considerations for cooling different
types of products. 4. The heat transfer surfaces on the walls can
be varied from impermeable, to micro-sieve, or to perforated.
Perforations or capillary channels allows for transpiration
conductively from the Dry Channel to the Wet Channel. This has
advantages in heat transfer and in efficiencies.
[0027] There are many variations that can be used with this core
method of the invention that are described here after. Tile
variations fit the wide variety of applications the core method can
be used in.
[0028] It is always advantages to wet both surfaces of the Wet
Channel, both the Dry Channel-Wet Channel heat transfer membrane or
wall and the Wet Channel-Product heat transfer membrane or wall,
(when a Product Channel is used,) to improve the heat transfer
rate.
[0029] In high humidity climates it is sometimes advantages to heat
the outside air entering or moving through the Dry Channel. At a
higher heat, with no change in humidity, there is a greater latent
heat capacity due to the ability to take on more moisture before
saturation. It is approximately five times faster than the energy
spent to gain higher temperatures.
[0030] Drying the air could be with desiccants such as Lithium
chloride, bromide, calcium chloride, glycol, triethylene glycol
etc. This allows cooling below the dew point temperature of outside
air when combined with desiccants before or in the Dry Channel
because it reduces the moisture content and thus increases the
latent heat potential capacity.
[0031] In addition liquids, in the applicable pressure and
temperature, with dew point temperatures less than that of water in
air, such as gasoline, can be used in the Wet Channel. The fluid
may be any suitable fluid that has a high vapor pressure at the
ambient temperature and pressure so as to enhance the evaporation
and thus take the heat of transformation from the remaining
fluid.
[0032] The Working Air can be dried with a desiccant and then
passed through the Dry and Wet Channels. This has the dramatic
effect of reducing the temperature of the Working Air and therefore
the minimum temperatures that can be obtained. The Product cooling
available is the difference between the total energy, enthalpy and
flow rate, of the hot Working Air in the Dry Channel and the total
Exhaust energy leaving the Wet Channel.
[0033] The method can be effectively used to cool water for power
plants and other typical cooling applications with return water
temperatures closer to the dew point temperature of the outside air
rather than the wet bulb temperature. In this case the Working Air
is precooled in the Dry Channel and humidified in the Wet Channel.
In many uses the temperature of the water to be cooled is warmer
than the outside air. This added heat works to the coolers
advantage as the temperature of the Working air will be increased
which will also increase the available cooling energy. The use of
desiccants to dry the air would lower the temperatures of the
cooling water further as this is a greater capacity.
[0034] The liquid desiccant can be placed in the Dry Channel
increasing the heat transfer rate from air to desiccant and
desiccant to the heat transfer surface by five to ten times. This
allows: 1. The temperature of the exhaust air to more closely
approach the air temperature entering the apparatus. 2. The
relative humidity of the exhaust to approach the saturation point,
and, therefore, increases the energy available for cooling of the
product.
[0035] Heat pipes can be used between the Wet and Dry Channels, and
the Product Channel as well, if desired, creating the need for only
one channel for each. This allows for easier configuration of a
purely counter flow arrangement of the method.
[0036] In addition, using a desiccant in the Dry Channel provides
continuous cooling of the desiccant and therefore increasing its
absorption capacity and rate, drying the air faster and to a lower
temperature.
[0037] Regeneration of the desiccant can take place within the core
method with the use of a porous heat exchange panel between the Dry
and Wet Channels. This panel would be designed to allow water
absorbed by the desiccant to be drawn directly to the waterside
through the panel by means of: 1. The lower pressure on the
waterside. A pressure drop does need to be created between where
the Dry Channel ends and the Wet Channel begins. The dry side may
have forced draft fans and the exhaust may have an induced draft
fan to create a larger pressure drop. 2. By the lower density of
water on the waterside causing the water in the desiccant to want
to move to the Wet Channel. 3. By the direction of the heat flow to
the waterside. The porosity may be to water in liquid or vapor
phase.
[0038] Depending on the Product to be cooled the Product Channel
could have a desiccant used for drying and cooling the product as
well.
[0039] The regeneration process does have a small loss in energy
due to de-mixing of water moving from the desiccant to the Wet
Channel, from liquid to liquid, but not going through a phase
change. When the exhaust air absorbs this water a vapor change
would take place creating a positive energy flow for cooling. The
heat transfer rate will be larger due to the lack of a boundary
layer in the channel separation wall and the direct connection of
water to both sides of the membrane.
[0040] Solid desiccants can be used for the heat transfer surface
in the regeneration process. Dry desiccants have the advantage of
no heat loss from cooled desiccant flowing from the Dry Channel and
carrying off some of the cooling energy. However the heat transfer
rate from the Working Air to the desiccant is less with a dry
desiccant. This desiccant regeneration and drying system could also
be used in the Product Channel.
[0041] The core method can be efficiently used for air conditioning
and cooling systems where liquid fueled engines are used such as in
a vehicle. The Evaporative Liquid in the Wet Channel becomes fuel.
The Dry Channel takes in outside Working Air for pre-cooling and
passing through the Wet Channel. The Product Channel in heat
transfer contact with the Wet Channel is cooled. In addition, it is
possible to use a solid or a liquid desiccant in the Dry Channel,
and liquid fuel and water to the working air in the Wet Channel
simultaneously increasing the potential energy of cooling, due to
the increased vapor pressure. In addition the fluid in the Dry
Channel can be heated for the Dry Channel, before, during or at the
end, with exhaust gases from the engine to provide additional vapor
potential and thus, latent heat capacity of the working air and
cooling product when water is being added to the Wet Channel with
the liquid fuel. The desiccant can be re-concentrated with the heat
source being the exhaust gas of the engine.
[0042] The addition of water in the Wet Channel will produce water
vapor in the fuel-air mixture, which is directed to the engine, and
it helps to improve the combustion process in the engine of a
vehicle.
[0043] With vehicles that do not use enough fuel to cool a vehicle,
or electric vehicles, core method with water/desiccant system can
be used.
[0044] Creating a lower pressure in the Wet Channel will increase
the vapor drive from water to the air. Increasing the pressure in
the Dry Channel will increase the vapor drive to the desiccant.
Pressurizing the Dry Channel and pulling a partial vacuum on the
Wet Channel will require the insertion of a baffle between the
channels to regulate the Working Air flow rate.
[0045] Recycling can be accomplished by use of liquid desiccants.
Diluted liquid desiccants can be used in the Wet Channel with dry
air to remove the water from the desiccants. This concentrated
desiccant can then be used to dry the air either within the Dry
Channel or outside the apparatus. To create a larger vapor drive
difference between tile Wet and Dry Channels, a pressure drop must
be created between them. In addition the Dry Channel may need to
have heat added before, during or after entering it and the Wet
Channel may need to have water added to a surface both causing a
greater vapor drive potential between the channels.
[0046] The method may be used to create cool concentrated desiccant
for drying air and then using a more conventional cooling system in
another process.
[0047] The core method can be efficiently used when working air is
redirected from the Dry Channel into and through the Wet Channel,
for example, through a plurality of spaced perforations or
permeable pores formed in the heat exchange surface.
[0048] It can help to increase the coefficient of heat transfer
between flows of working air in the Dry and Wet Channels. Also, it
can help to transport absorbed water (when we use solid desiccant
material) from the Dry to the Wet Channel.
[0049] The working heat exchange apparatus for effecting the
above-described method will have: 1) A jacket with inlets and
outlets for the Product Fluid and the Working Air or other fluids
respectively. 2) The Product Channels for the Product Fluid. 3) The
communicable Dry and Wet Channels for the Working Air with a heat
exchange plate with or without perforations or pores. 4) The
Product and Dry and Wet Channels are alternated and separated with
plates. 5) A liquid distributor for channels with moisture on the
walls Such as a liquid desiccant or water. 6) Collecting trays for
this liquid. 7) Valves for proper regulation of fluids in the
channels. 8) Other components needed for specific function and
operation of the apparatus, if pressure regulation is needed.
[0050] Counter flow is theoretically the most efficient design,
however there are many designs that can be used to produce a more
economically viable units using cross flow or some other
combination of flow.
[0051] The plate or membrane, which is the heat exchange surface
between the channels, can be made of wick, plastic, metal or solid
desiccant materials or compositions of these materials.
[0052] While the description of this apparatus incorporates
vertical channels for liquid wetting of airflow throughout the
channel, there are various methods of moving liquids such as
wicking, high air or vapor velocity, enough partial vacuum to lift
the fluid, inclined slopes, etc. Depending on the application and
design, the apparatus can be used with panels turned from
horizontal to vertical.
DESCRIPTION OF THE DRAWINGS
[0053] The invention will now be described by way of preferred
exemplary embodiment thereof with reference to appended drawings,
wherein similar parts have tile same reference numerals and in
which:
[0054] FIG. 1 is a flow diagram of the present method for
indirect-evaporation cooling where by the Product 2 is cooled in
the Product Channel 1 along side the Wet Channel 5 and when
multiple channels are used, the Dry Channels 3 of the adjacent
cooling unit as well.
[0055] FIG. 2 is a flow diagram of the present method for
indirect-transpiration cooling where by the Product 2 is cooled
with the use of excess Evaporative Liquid 10 such as water that has
been cooled and is used to cool the Product 2 in a separate Product
Heat Exchanger 39.
[0056] FIG. 3 is a flow diagram where a desiccant, 47, is used in
the Dry Channel 3 for drying the air and a separate regeneration
apparatus, 56, is used to increase the concentration of the
desiccant. The Wet Channel 5 has water flowing down it and is
cooled through evaporation. Product Channel 1 is set along side and
in heat transfer contact with the Wet Channel 5 for Product cooling
of some other fluid.
[0057] FIG. 4 is a flow diagram like FIG. 3 where a desiccant, 47,
is used in the Dry Channel 3 for drying the air and a separate
regeneration apparatus, 56, is used to increase the concentration
of the desiccant 47. The Wet Channel 5 has water flowing down it 10
and is cooled through evaporation. Cool water 10 can be the Product
2.
[0058] FIG. 5 is a flow diagram like FIG. 3 but where the Product
72 becomes part of the Working Fluid 4, which in most cases is
air.
[0059] FIG. 6 is a flow diagram, where the heat exchange surface 9
of the Dry Channel is made of or covered with solid desiccant
material 46, for example, silica gel, lithium chloride and etc.
Regeneration of the desiccant is by passing water through the wall
of the heat transfer surface.
[0060] FIG. 7 is a flow diagram, where the heat exchange surfaces
of the Dry Channel 3 and also tile Product Channel 1 are made or
covered with the solid desiccant material 46.
[0061] FIG. 8 and FIG. 9 are flow diagrams, where the Dry Channel 3
or both the Dry 3 and Product 1 Channels are made of or covered
with solid desiccant material 46 and tile walls of the Wet Channel
5 are wetted by a Evaporative Liquid 10 such as water without the
formation of a moving liquid film.
[0062] FIGS. 1 to 9 contains: the Product Channel-1, the Product
Fluid-2, Dry Channel-3, the Working Air-4, the Wet Channel-5
membranes, or walls-6 and 7 have heat exchange surfaces-8 and 9,
moving film of Evaporative Liquid such as water or a wet surface
but non moving film such as with a wick-10, the induced draft
fan-11, a forced draft fan 74, pipes-41, 42, desiccant 46 and
baffle 73.
[0063] FIG. 9(a) is similar to FIG. 9, except it has the working
membrane made of or covered with solid desiccant.
[0064] FIG. 10 is a flow diagram, where liquid fuel 10 flows down
along the walls of the Wet Channel 5: vehicle-61, fuel tank-62,
internal combustion engine-63, vehicle cab-64, exhaust gas-65,
pipe-66, ducts-67 and 68.
[0065] FIG. 11 is the same flow diagram like FIG. 10, where the
Product 2, such as air, being cooled is in a heat exchanger 39
using the Evaporative Liquid 10 after it's cooled.
[0066] FIG. 12 is a flow diagram, where liquid desiccant 47 flows
down along the heat exchange surface 9 of the Dry Channel 3 and
simultaneously liquid fuel 10 flows down along the walls of the Wet
Channel 5 and the product is cooled in the Product Heat Exchanger
39.
[0067] FIG. 13 is the same flow diagram like FIG. 12, where the
Product 2, such as air, being cooled is in the Product Channel
1.
[0068] FIG. 14 is a flow diagram where the wall 7 is crossed with a
bank of heat pipes 69, evaporator sections 70 that are located in
the Dry Channels 3 and condenser sections 71 in the moist channel
5; the Product 2 cooling takes place in the Product Heat Exchanger
39.
[0069] FIG. 15 is a flow diagram like FIG. 14 where a bank of heat
pipes 69 is used to span between the Wet Channel 5 and the in the
Product Channel 1.
[0070] FIG. 16 is a flow diagram where cooled desiccant 10 is
concentrated in the Wet Channels 5 and used for cooling. The
concentrated desiccant is used for pre-drying the incoming air 4,
and re-circulated in the Wet Channel 5.
[0071] FIG. 17 is a flow diagram similar to FIG. 16 where a Product
Channel 1 has been added.
[0072] FIG. 18 is a flow diagram similar to FIG. 16 where cold
desiccant 10 is used to dry and cool air or Product 2.
[0073] FIG. 19 is a flow diagram similar to FIG. 18 except dried
air 2 is directed to an apparatus for direct or indirect cooling
40.
[0074] FIG. 20 is a flow diagram with the same general concept as
FIG. 16 but where the desiccant dries the air in the Dry Channel 3
and then is directed to the Wet Channel, desiccant from the Wet
Channel is returned to tile Dry Channel. The Product 2 is cooled in
the Product Heat Exchanger 39.
[0075] FIG. 21 is a flow diagram with the same general concept as
FIG. 17 but where the desiccant dries the air in the Dry Channel 3
and then is directed to the Wet Channel, desiccant from the Wet
Channel is returned to the Dry Channel. The Product 2 is cooled in
the Product Channel 1.
[0076] FIG. 22 is a flow diagram similar to FIG. 21, where the
Product Fluid 2, for example, outside air, is transported to any
kind of an apparatus for direct or indirect evaporative cooling
54.
[0077] FIGS. 16-22 contain: the Product Channel 1, the Product
Fluid 2, Dry Channel 3, the Working Air 4, the Wet Channel 5
membrane, or walls 6 and 7 have heat exchange surfaces 8 and 9,
moving film of liquid such as desiccant 10, the induced draft fan
11 and forced draft fan 74, the mass and heat exchange apparatus 33
or air dryer 33, valves 34, 35, 36, 37 and 38, the heat exchange
apparatus 39, the apparatus for direct or indirect cooling 40 and
54, pipes 41, 42, 43, 44, 48 and 50, duct 45, pump 49 and 51, Dry
Channel tray 52, Wet Channel tray 53, and baffle 73.
[0078] FIG. 23 shows cross flow direction of motion between the
Working Air 4 in the Dry Channel 3 and the Working Air 4 in the Wet
Channel 5.
[0079] FIG. 24 illustrates an example of a flow diagram, where
working air 4 is redirected from the Dry Channel 3 into and through
the Wet Channel 5.
[0080] FIG. 25 is a schematic view of the heat exchange apparatus
for effecting the method in accordance with the present invention
(FIGS. 1, 4, 5, 6, 7, 8, 9, 11), where: a jacket 12, inlet and
outlet connections for the Product Fluid 13 and 15, inlet and
outlet connections for the Working Air 14 and 17, adjustable
dampers-16 and 21, tray for liquid from the Wet Channel 18, liquid
distributor for the Wet Channel 19, valve for selection of liquid
from the Wet Channel 20, the Wet Channels 22, the Product Channels
for the Product Fluid 23, the Dry Channels for the Working Air 24,
baffle-boards 25, 27 and 28, blind chamber 26, chambers 29 and 30,
fan for the Product Fluid 31, induced draft fan for the Working Air
32, forced draft fan 33, baffle 34.
[0081] FIG. 26 is a schematic view similar to FIG. 24 heat exchange
apparatus wherein the Dry Channels is equipped with a liquid
distribution system-58 for the Dry Channels-24, tray for this
liquid-60, valve-59.
DETAILED DESCRIPTION OF THE INVENTION
[0082] FIG. 1 illustrates a flow diagram with a Product Channel 1
used for cooling a Product 2. The Product Fluid 2 is fed along the
Product Channel 1 of the heat exchange apparatus, and the Working
Air 4, for example, outside air is fed along the Dry Channel 3. The
Wet Channel 5 is arranged in heat transfer contact with Dry
Channels 3 via membrane 7. The membrane 7 has heat exchange surface
9, limiting the corresponding Dry Channel 3. The reverse sides of
this membrane 7 are wetted with a moving film of the Evaporative
Liquid, for example, water 10 using any available method. The
membranes 6 and 7 can be made of wick, plastic, metal, solid
desiccants, micro sieve, etc. materials or composition of these
materials. It is understood that the term membrane is used, but any
structure that performs the function of separating Channel 3 from
Channel 5 or the working air from the product channel is suitable.
The Working Air 4 is drawn to the induced draft fan 11 mounted at
the outlet of the Wet Channel 5 or in some cases the air is pushed
through by forced draft fan 74. The Product Fluid 2 is directed
along the Product Channel 1, where it is cooled without changing
its moisture content. At the same time the Working Air 4, is
directed concurrently with respect to the Dry Channel 3 in contact
with a heat exchange surface 9. In so doing, the Working Air 4 is
cooled, due to the heat absorption due to evaporation occurring in
the Wet Channel, without any change to the moisture content of the
Dry Channel air and then it is turned to the Wet Channel 5, where
it flows counter currently in contact with the moist surfaces, for
example, with wick or capillary-porous material being wetted by
Evaporative Liquid 10. As the Working Air 4 passes along the Wet
Channel 5 it is heated, moistened and is preferably drawn by the
induced draft fan 11 to the atmosphere or as in some cases forced
by fan 74. As the Working Air 4 passes along the heat exchange
surface 9, it is cooled as a result of the heat exchange by the
same flow passing along the surfaces of a Wet Channel 5 that are
wetted by the moving Evaporative Liquid 10. In the Wet Channel 5,
latent heat of evaporation is removed which results in the cooling
of Working Air 4 on the wet surface and eventually owing to heat
transfer via the membrane 7 giving pre-cooling of Working Air 4 in
the Dry Channel. Should outside air taken directly from the
atmosphere be used as the Working Air 4, passing through the Dry
Channel 3, then by the time it has passed through the Dry Channels
and contacts the moisture in Wet Channel 5 it will have cooled down
to near the dew point temperature of the Working Air. In so doing,
the Product Fluid 2 can be cooled in an ideal case to the dew point
temperature by the evaporative action in the Wet Channel taking
latent heat from the heat exchange membrane between the product and
the Wet Channel. In actual fact, this temperature will be still
higher due to the Product Channel membrane 6 thermal
resistances.
[0083] It follows from FIG. 1 that the length of the Dry Channel 3
is equal to that of the Wet Channel 5, although alteration and
various relations of these channels' lengths are possible.
[0084] To increase the cooling potential, the Working Air 4 can be
heated before, during or after it's passing along the Dry Channel
3, (FIG. 1). Increasing temperatures of the Working Air 4, before,
during and after passing along the Dry Channel 3, gives the
possibility to increase latent heat capacity, and thus, the
efficiency of the exhausted Working Air 4 into the Wet Channel 5.
This is due to the latent heat having a larger effect on the
enthalpy than sensible heat with a greater effect as the
temperature rises.
[0085] As the airflow passes along any surfaces, aerodynamic losses
of the head always occur due to resistance. Therefore, in the
within embodiments, the value of the head of the Working Air 4 will
decline as it moves along the heat exchange surface 9 in the Dry
Channel 3, particularly when it turns 180 degrees and then as it
travels over the wetted surfaces of the Wet Channel 5. This
pressure drop will cause a lowering of the vapor partial pressure
of the air and in turn will reduce the dew point temperature of the
air. Sometimes it is attained through the use of resistance in the
channels such as with corrugated panels oil small channel width,
with baffles, valves, liquid flow etc. This, in turn, will
facilitate more effective evaporation of water vapor into this air
to increase the cold production process of transpiration
cooling.
[0086] In the method according to the invention it is expedient
that additional aerodynamic resistance be created in order to
enhance the evaporation cooling efficiency. Additional power
consumption for the fan will be much lower in many cases than the
value of the positive effect obtained with an increased evaporation
of water into Working Air 4. It is possible to provide additional
aerodynamic resistance and disruption of stagnant surface layers of
working fluids, for example, using various perforations or pores or
by heat exchange surfaces, by placing them in the flow path. It is
also possible to provide aerodynamic resistance by narrowing this
flow path, placing dampers in its path or restricted pathways.
[0087] This yields a double advantage of a lower pressure in the
Wet channel 5 increasing the evaporation rate, and increasing the
heat transfer rate in the Dry channel 3 where there is a lower heat
transfer rate as compared to the Wet Channel between the dry
Working Air 4 and heat transfer surface 9. In addition to the
alteration of the vapor pressure, the partial vacuum which is
created by the induced draft fan 11 can be used to increase the
capillary action or passage through perforations or pores, in some
designs where wicking is used between the Dry and Wet Channels or
in the distribution of the liquid desiccant.
[0088] The invention makes use of a heat transfer membrane that
separates two portions of a working gas flow channel. As seen in
FIG. 1 the gas depicted as 4 flows down channel 3 which we
designate the dry channel and up channel 5 which we designate to be
the wet channel. The heat transfer membrane 7 is comprised of a
thin material that allows the transmission of heat across its
horizontal width because of its thin construction. The heat
transfer membrane 7 generally, through a given thickness does not
have good heat transfer ability relative to materials such as
metal. However, due to its thin construction of the wall thickness
between channel 3 and channel 5, heat is able to transfer easily
and quickly from channel 3 to channel 5. The heat at any given
location on the membrane does not readily move along the surface of
the membrane because of the materials' high resistance to heat
transfer, in a direction other than across the thin membrane.
[0089] The result of this is that temperatures will vary along the
height or vertical distance shown in FIG. 1 and depicted in
reference levels AA, BB, CC, DD, EE, FF, and GG. The choice of the
wall material, whether it is relatively impermeable to moisture or
able to transmit water or vapor as a micro-pore or perforated
membrane, requires this heat transferability parameter. The
particular material may be paper, plastic such as Tyvek, sieve
webbing or any common matter meeting these parameters.
[0090] Within wet channel 5, water or other fluid is on the walls
of the wet channel 5. The passage of the gas or working fluid 4
from its source 74 through the dry channel 3 and into channel 5 and
is shown as counterflow. The wet channel 5, which has fluid on its
walls, allows for the use of evaporation and the heat of
transformation or evaporation to be transferred from the fluid,
thus cooling the fluid. The exhaust gases of the working fluid
exits at 75. The gases in the wet channel 5 due to evaporation will
cool the fluid and in turn the membrane 7 which will in turn cool
the working gas in channel 3, the dry channel.
[0091] The working gas 4 in the wet channel will continue taking
the vapor of the evaporation of the fluid until it reaches or nears
its saturation point. FIG. 1 at AA would be one temperature in the
exhaust or wet channel side. That temperature would be transmitted
through the membrane 7 to its counterpart in the dry channel side.
Similarly this occurs at points BB and CC and through the various
levels of FIG. 1. At AA the working fluid at that point has had the
least amount of time to pickup evaporative vapor and thus the least
opportunity to cool the fluid that would be instantaneously located
at AA.
[0092] As you proceed further up the wet channel from BB to CC and
on, tile temperature due to evaporation, will continue to be cooled
at each location.
[0093] Simultaneous with the continued evaporation which will cool
the fluid at the level that the evaporation occurred, the fluid
that has been cooled at a given level will be moving downward as it
moves. The additional effects of the fluid which has been cooled by
evaporation and is moving downward is that fluid that had been at
GG and cooled by evaporation through time will move downward to DD
where further evaporation will occur and onward to AA and if any
excess fluid is left it exits the system. This flow allows the
fluid at the level where it is cooled by evaporation through heat
transfer to take heat from the dry channel 3 at that point and
provide the fluid latent heat and additional vapor pressure for
further evaporation. Then further evaporation will cool the liquid
more. Thus, the fluid continues to provide evaporation and take off
heat of transformation. Further the lower temperature that had been
created at FF by evaporation will be transmitted by heat transfer
to the dry channel and by flow downward to the lower levels of the
membrane 7 where further evaporation will occur which, in turn,
will further cool the concurrent side of the dry channel across the
thin membrane 7. Thus the cumulative impact at AA will be from
evaporation that has occurred above it and the transmission of that
cooled fluid down to the point AA as well as the evaporation that
occurs at point AA. At GG the temperature or cooling will occur at
GG solely by way of evaporation. But by the working fluid being
cooled, the stable temperature at GG will be lower than outside
ambient temperature.
[0094] The effect on the dry channel portion of the working fluid
flow 4 is that the working fluid in the dry channel will be cooled
at GG because of the cooler temperature across the membrane 7.
Similarly this cooling will continue to occur to the working flow 4
as it progresses downward from level GG, FF, DD, CC, BB and AA.
Thus the dry channel flow will be precooled before it turns at the
bottom of FIG. 1 and proceeds upward through the wet channel. Due
to the fall of the cool fluid in the wet channel along that side of
the membrane 7 the lowest temperature will occur at the AA
position. The total system will cool until it reaches a stable
temperature. Likewise because of the heat transfer and the
pre-cooling that has occurred from levels GG through the dry
channel, flow of the working fluid 4 will also be at its lowest
temperature at level AA.
[0095] Also shown on FIG. 1 is a third channel 1 that has a flow of
product gas or fluid. There is a heat transfer membrane 6 that
separates the wet channel from tile product channel 1. Similar to
the membrane 7 this membrane is also of a material that does not
provide good heat conductivity normally but because of the thin
construction of the wall separating channel 1 from channel 5 heat
transfer readily occurs. This material, aside from meeting the
environmental consideration of the Wet Channel and the Product
Channel, can be of any material, just like membrane 7. The
temperature transfer vertically or along the surface of the
membrane 6 does readily occur. The flow of the product air is again
counter to the flow of the working gas in the wet channel, but it
can be of any orientation. Again this provides the maximum amount
of cooling to the product gases. At point GG gases and the wet
walls in the wet channel have been cooled by the evaporation. This
cools the liquid on the surface of the membrane 7 and 6. The
membrane 6 in turn cools the product in channel 1. At point AA the
product is being cooled to its maximum similar to the cooling that
occurred in the dry channel because of the combination of the
evaporation at point AA, the pre-cooling of the Dry Channel air and
the movement of cooled fluid down from positions above. It is
understood that the orientation of the FIG. 1 and the use of the
terms vertical and up and down are descriptive and not limiting. It
is understood that the flow of the fluids in the wet channel may be
accomplished by means other than gravity.
[0096] FIG. 2 illustrates a flow diagram of the present method,
where excess Evaporative Liquid such as water 10 flows down along
the walls 6 and 7 of the Wet Channel 5 to the Product Heat
Exchanger 39 and cools Product Fluid 2 flowing through it.
[0097] In applications where the method of cooling the product does
not use excess evaporative liquid, the flow of fluid will be just
equal to the maximum evaporation occurring during the wet channel
phase. Wicking to the entire extent of the wet channel would be
ideal.
[0098] FIGS. 3 and 4 add a concentrated desiccant in the Dry
Channel 3 with a desiccant regeneration process out side the
apparatus. This has the direct effect of lowering the humidity in
the air allowing for lower temperatures and added cooling capacity.
The desiccant 47 on surface 9 in Dry Channel 3 absorbs water vapor
from the Working Air 4 and transmits heat through the wall 7 to the
water 10 of the wet channel 5 evaporating into the Working Air 4.
The continual cooling of the desiccant 47 in channel 3 increases
tile Working Air 4 drying capabilities.
[0099] The flow rate ratio with the working gas is described in
Lowenstein, U.S. Pat. No. 5,351,497 and is ideal at 1.0
gpm/ft.sup.z in a counter flow design.
[0100] In higher humidity climates it is rational, FIG. 4, to
establish the process, wherein liquid desiccant 47 flows down along
the heat exchange surface 9 of Dry Channel 3, and water 10 also
flows down along the walls 6 and 7 of the Wet Channel 5
simultaneously. In addition, liquid desiccant 47, after its passing
along Dry Channel 3 and the tray 52, is directed by the pump 51
(via the pipe 55) to the regenerator 56, where moisture is
vaporized from liquid desiccant and then it is brought back (via
the pipe 57) into Dry Channel 3. Herewith, liquid desiccant, before
it's directing to regenerator 56, beforehand is heated. And water
10, after it's passing along the Wet Channel 5 and the tray 53, is
directed back by the pump 49 (via the pipe 41) to the Wet Channel
5.
[0101] When liquid simultaneously flows down in Dry Channel 3 and
the Wet Channel 5 in the manner of moving fluid film 47 and
Evaporative Liquid 10 (see FIGS. 3-5), it significantly improves
heat and mass transfer performances in each channel. This creates a
more compact and effective apparatus.
[0102] FIG. 5 illustrates the apparatus where a portion of the
Working Air 4 is drawn off as the Product 72 and the rest of tile
Working Air 4 continues on in Wet Channel 5. This has the advantage
of better heat transfer between the Product/Working Air than would
there be in a Product Channel 1 or Product Heat Exchanger 39 when
dry cold air is needed as a product.
[0103] FIG. 6 illustrates, an internal desiccant regeneration
process in conjunction with a drying process wherein the heat
exchange surface 9 of Dry Channel 3 is made or covered with any
available solid desiccant material 46, for example, silica gel,
lithium chloride and etc. When the Working Air 4 is passing through
Dry Channel 3 in contact with a heat exchange surface 9, it reduces
not only the temperature but also humidity of the Working Air 4,
because solid desiccant material adsorbs the moisture from this
air. The cold and drier Working Air 4 is passed to the Wet Channel
5 through pressure reduction baffle 73, if needed, where it
evaporates the water 10 creating lower temperatures than outside
air dew point temperatures because the Working Air 4 has less
humidity. In addition the heat of adsorption, which transports from
Dry Channel 3 via tile wall 7 to the Wet Channel 5, is increased
due to the direct contact of fluids through the wall 7. Herewith,
this action increases heat and mass performances as in Dry Channel
3, as well as in the Wet Channel 5
[0104] In some cases it is necessary to create a larger Pressure
drop between the Dry 3 and Wet 5 Channels to realize the process
with the fluids being used as the Working Fluid 4, Evaporative
Liquid 10 and drying liquid or solid 47. In this case a pressure
reduction baffle 73 must be placed between the Dry and Wet Channel
and possible a forced draft fan 74 at the inlet of Dry Channel
3.
[0105] In this method of indirect-evaporation cooling the walls 7
and 6 can be made of wick, plastic, metal or solid desiccant
materials or compositions of these materials, with tile physical
capability of heat transfer being less along the surface of the
wall or membrane as compared to the heat transfer rate across the
thickness of the wall between the adjacent pathways. If the walls
have some capacity of transferring vapor or liquid across the
thickness, a bias will be created, by pressure or other means
commonly known or developed in the future to bias this ability to
be on a selected direction such as from the Dry Channel to the Wet
Channel, or from the Product Channel to the Wet Channel. This
method gives unique possibility to organize the very effective heat
and mass exchange processes between the Dry 3 and Product 1
Channels and the Wet Channel 5, using the wick or solid desiccant
materials for the walls 7 and 6, without presence of the waterproof
partition. First of all, it improves heat and mass transfer
performances in channels because wetted wick or solid desiccant
materials have more conductivity than other materials, due to the
moisture passage into the material on tile Dry side and out of the
material on the wet side. Also less heat resistance on the
interface between airflow and the wall or the liquid film or moving
liquid film and a wall. Second, wick or solid desiccant materials
for the wall enables effective transport of adsorbed moisture from
Dry Channel 3 to Wet Channel 5 via the membrane. The differences of
the pressures between Dry Channel 3 and Wet Channel 5, aid this
movement. Opposite direction of movement of liquid from the Wet
Channel 5 to the Dry Channel 3 and 1 is not possible, because
pressure in the Wet Channel 5 is always less than pressure in the
Dry Channels 3 and 1.
[0106] FIG. 7 shows the same scheme like FIG. 6, wherein there is
only one distinction, namely, the heat exchange surface 8 of the
Product Channel 1 also is made or covered with the solid desiccant
material 46, for example, silica gel, lithium chloride and etc.
When the Product Fluid 2, for example, outside air is passing
through tile Product Channel, solid desiccant 46 adsorbs the
moisture from this air. This creates not only cold (about the dew
point temperature of dried air 4) but dryer air 2. The process of
adsorption in Dry Channels 1 and 3 is continuous. Adsorbed moisture
transports from Dry Channels 1 and 3 via the walls 6 and 7 to the
Wet Channel 5, because the pressure of air is always less in the
Wet Channel 5 than in the Dry Channels 1 and 3. In addition the
density difference between the desiccant 46 and the water 10, and
the heat flux direction from desiccant 46 to water 10 will help
pull the water from the desiccant to the Wet Channel 5.
[0107] FIG. 8 and FIG. 9 illustrate the flow diagrams of the
present method; wherein the walls 7 and 6 of the Wet Channel 5 are
wetted by water 10 without the formation of a moving liquid film
with for instance the use of a wick. Herewith, the heat exchange
surface 9 of Dry Channel 3 (FIG. 8) or the heat exchange surfaces 9
and 8 of both Dry 3 and Product 1 Channels (FIG. 9) are made or
covered with the solid desiccant material 46, for example, silica
gel, lithium chloride and etc. In this case the Product Fluid 2,
for example, outside air can be cooled lower then the dew point
temperature of the outside air. The advantage of not having a
moving water film 10 is that there is no energy losses do to
cooling water that is not directly evaporated allowing for
additional product cooling.
[0108] FIG. 9a is similar to FIG. 9 illustrating the flow diagram
of the present method wherein the sides of the walls 7, which are
located in the Dry Channels 3 and/or the Product Channels 1 are
made or covered with a solid desiccant material 46, such as silica
gel, lithium chloride, etc. The use of a solid desiccant sheet or
membrane is disclosed in U.S. Pat. No. 5,653,115. Similar materials
are available from manufacturers. The other side of these walls 7
are located in the Wet Channel 5, but are not wetted by the
Evaporative Liquid. Only Wet Channel 5 side of walls 6 are wetted
with Evaporative Liquid 10 such as water, liquid desiccant or fuel.
The advantage of this design is that it adsorbs water vapor from
the Working Air 4 in the Dry Channels 3 and/or the Product Air 2 in
the Product Channels 1 via the walls 7 and 6 to the Wet Channels
5.
[0109] The present method can be efficiently used also for air
conditioning and cooling systems for vehicles, wherein the
Evaporative Liquid in the Wet Channel 5 is liquid fuel (see FIGS.
10-13).
[0110] FIG. 10 illustrates the same apparatus as in FIG. 1, wherein
Evaporative Liquid 10 is a fuel, which is drawn from the fuel tank
62 of a vehicle 61 and it is transported via a pipe 66 to the Wet
Channel 5. Herein, liquid fuel 10 flows down along the walls 7 and
6 of the Wet Channel 5. At the same time, the Working Air 4, for
example, outside air is directed along Dry Channel 3 in contact
with a heat exchange surface 9. In so doing, the Working Air 4 is
cooled without change in its moisture content and then it is turned
to the Wet Channel 5, where it moves counter currently in contact
with the moving film 10 of liquid fuel. In the Wet Channel 5 the
vapor evaporates from liquid fuel 10 into the Working Air 4. As a
result this contact, latent heat of evaporation is removed. As the
Working Air 4 passes along the Wet Channel 5, it is heated through
the heat exchange wall 7, and saturated by the vapor of liquid fuel
and an induced draft fan 11 pulls it through channel 5. Forced
draft fan 74 is an optional but less desirable arrangement needed
to accommodate actual apparatus physical design restraints. Hereon,
this fuel-air-mixture is directed via duct 67 to the internal
combustion engine 63 of a vehicle 61. At the same time the Product
Fluid 2, for example, outside air is directed along the Dry Channel
1 in contact with the heat exchange surface 8. Herein, outside air
2 is cooled ideally to the temperature reached of the fuel/air
mixture temperature created when the fuel evaporates in air, that
the engine 63 requires.
[0111] After passing along tile Dry Channel 1, the Product Fluid 2
is directed via the duct 68 to the cab 64 of a vehicle 61. The heat
exchange surfaces 9 and/or 8 of Dry Channel 3 and/or the Product
Channel 1 can be made or covered by a solid desiccant material, for
example, silica gel, lithium chloride and etc. (as this is seen
from FIGS. 7-9). In additional, the walls 6 and 7 of the Wet
Channel 5 can be wetted by liquid fuel 10 without formation of a
liquid moving film (as this is seen from FIGS. 8 and 9).
[0112] FIG. 11 is the same flow diagram like FIG. 10, where the
Product Fluid 2, for example, outside air is directed to heat
exchange apparatus 39 for heat exchange contact with cold liquid
fuel 10, after its passing through the Wet Channel 5. Hereon, the
cold air 2 is directed via the duct 68 to the cab 64 of a vehicle
61. In additional, the Working Air 4 as the fuel-air mixture, after
it's passing along the Wet Channel 5, is directed via the duct 67
to the internal combustion engine 63 of a vehicle 61.
[0113] FIG. 13 illustrates the same scheme like in FIG. 10, but
wherein as the Evaporative Liquid is a mixture of water and fuel
10, which is selected from the fuel tank 62 of a vehicle 61, and it
is transported via a pipe 66 to the Wet Channel 5. Herein, water
and liquid fuel 10 flows down along the walls 6 and 7 of the Wet
Channel 5 or they are wetted by liquid fuel 10 without formation of
a liquid moving film. Simultaneity liquid desiccant 47 flows down
along the heat exchange surface 9 of Dry Channel 3 and then it is
directed to the regenerator 56. Herein, moisture is vaporized from
liquid desiccant 47 by heat of exhaust gas 65 of a vehicle 61, and
it is brought back into Dry Channel 3. This drying of the Working
Air 4 prior to passing through the Wet Channel 5 increases the
product cooling quantity and quality as it allows additional
evaporation of water as well as fuel. Working Air 4 passes along
the Wet Channel 5 creating the fuel-air mixture and is directed via
the duct 67 to the internal combustion engine 63 of a vehicle 61.
Simultaneously the Product Fluid 2, for example, outside air, after
it's passing along the Dry Channel 1 is directed to the cab 64 of a
vehicle 61.
[0114] FIG. 12 is the same flow diagram like FIG. 13, where the
Product Fluid 2, for example, outside air is directed to the heat
exchange apparatus 39 for heat exchange contact with cold water
and/or liquid fuel 10, after its passing through the Wet Channel 5.
Hereon, the cold product air 2 is directed via the duct 68 to the
cab 64 of a vehicle 61. In additional, the Working Air 4 as the
fuel-air-mixture, after it's passing along the Wet Channel 5, is
directed via the duct 67 to the internal combustion engine 63 of a
vehicle 61.
[0115] In FIGS. 10-13 water can be added along with liquid fuel,
and for certain in FIGS. 12 and 13 before it's passing along the
Wet Channel 5 increases the evaporative cooling by a combined water
and liquid fuel 10 in the Wet Channel 5. In addition it increases
the water vapor in the fuel-air mixture, which is directed via the
duct 67 to the engine 63, and it helps to improve the combustion
process in the engine 63 of a vehicle 61. As a result the exhaust
gases from the engine have less toxicity.
[0116] In vehicles that do not use enough fuel to adequately cool
the interior, in electrical vehicles or other types of vehicles,
water can be evaporated 10 in Wet Channel 5 of FIGS. 12 and 13.
This system will need to be combined with a desiccant 46 in the Dry
Channel 3, (FIG. 9) or another variation of the apparatus that
dries the air.
[0117] Using the exhaust from the engine to preheat the air 4
entering channel 3 can effectively use waste heat to create a
greater potential energy for cooler production.
[0118] Heat pipes can make an effective design within this method,
see for example FIGS. 14 and 15 where the walls 6 and 7 separate
the channels and a bank of heat pipes 69. Heat pipes such as those
comprised of a sealed vessel with a heat carrier inside. On one
end, heat is taken into the vessel by heat transfer boiling the
heat carrier into vapor. The vapor moves to the cool section of the
vessel where it condenses, giving up the latent heat and converting
the vapor back to the liquid state. The evaporator section 70 being
located in the Dry 3 or Product 1 Channels and condenser sections
71 are located in the Wet Channel 5. This effectively eliminates
the need for a plethora of channels as the heat pipes transfer the
heat. Additionally, the sections operate as surface irregularities
to break up the boundary layers of the fluid. In conventional units
heat pipes are used for thermal heat recovery units. In the present
invention desiccant 47 is sprayed on the evaporator section (or
evaporator section of the heat pipes are covered by a solid
desiccant) of the heat pipes 70 of the bank of heat pipes 69 in the
Dry Channel 3 with Working Air 4 flowing over the pipes and giving
up the heat of absorption as the air is dried. This heat travels
through the heat pipes to the Wet Channel 5 and the condensing side
of the heat pipes 71, where water 10 is sprayed on them with the
Working Air 4 traveling over the pipes and absorbing the water
evaporation. The evaporation liquid desiccant 47 is used more
efficiently because the heat of absorption is dynamically
transferred away from the Dry Channel 3 to the Wet Channel 5, thus,
reducing the absorption temperature and positioning tile operation
in a more favorable portion of the desiccant and moisture
equilibrium map.
[0119] FIGS. 16-19 illustrates a flow diagram of the present method
of indirect-evaporation cooling where evaporative liquid 10 is a
liquid desiccant which flows down the Wet Channel 5 of walls 6 and
7. The Working Air 4 is first directed for dehumidifying by contact
with a concentrated liquid desiccant in a mass and heat exchange
apparatus 33 or Air Dryer 33 (FIGS. 16 and 17).
[0120] In this case, the Evaporative Liquid 10 is the desiccant
used in Air Dryer 33 and is being regenerated to a higher
concentration for use in the Wet Channel 5. The concentrated
desiccant is then directed via the pipes 41 and 43 (the valve 38 is
opened and the valve 37 is closed) back to the mass and heat
exchange apparatus 33. The hot but dry Working Air 4 coining out of
Air Dryer 33 is transported via the duct 45 (the damper 35 is
opened and the damper 34 is closed) to Dry Channel 3. The hot and
weak desiccant 10 coming out of Air Dryer 33 is directed via the
pipes 44 and 42 (tile valve 36 is opened) to the inlet of tile Wet
Channel 5. The valves 36, 37 and 38 are dedicated for regulation of
ratio of quantity of liquid desiccant 10 coming to the inlet of the
Wet Channel 5 directly from of the outlet of the Wet Channel 5 (via
the pipes 41 and 42) and from Air Dryer 33. The dampers 34 and 35
are dedicated for regulation of ratio of quantity of the Working
Air 4 coining to the inlet of Dry Channel 3 from outside air (via
the damper 34) and from tile apparatus 33 (via the duct 45 and
damper 35). This ratio depends from regimes of working all system
and the parameters (especially humidity) of outside air because
outside air is energy resource for realizing of this method of
direct-transpiration cooling.
[0121] To create the right conditions for tile regeneration of
desiccant in the Wet Channel 5, heat may need to be added to the
Working Air 4. The specific heat input is readily known by one
familiar with regeneration of desiccants. With added heat in the
Working air there will be added potential energy for evaporation in
the Wet Channel 5 allowing additional water to be added to the
desiccant 10.
[0122] FIGS. 16-19 represent the apparatus being used to cool and
regenerate or re-concentrate the desiccant.
[0123] FIG. 16 illustrates a flow diagram of the present method,
where the Product Fluid 2, is directed for heat exchange contact
with liquid 10, Product heat Exchanger 39. FIG. 17 uses a Product
Channel 1 rather then a Product Heat Exchanger 39
[0124] FIG. 18 illustrates a flow diagram, where the desiccant 10,
(like on FIG. 16) but without the apparatus 39, is directed to Air
Dryer 33. The Product Fluid 2 is passed through Air Dryer 33 where
it is dried and cooled with cold desiccant. In this use the Wet
Channel 5 becomes the desiccant regenerator and may require heat to
be added to the Working Air 4 for the process to work and/or a
large pressure difference between the Dry Channel 3 and the Wet
Channel 5 caused by a pressure reduction baffle 73 a forced draft
fan 74 and a induced draft fan 11.
[0125] FIG. 19 illustrates a flow diagram of the present method,
where the Product 2 is outside air after its mass and heat exchange
contact with liquid desiccant 10 in apparatus 33, is transported to
any kind of an apparatus 40 for direct or indirect evaporative
cooling.
[0126] The present invention has the essential advantages, which
are shown in FIG. 22. Herein, the liquid desiccant 10, which flows
down along not only the walls 7 and 6 of the Wet Channel 5, but
also liquid desiccant 47 flows down along the heat exchange surface
9 of Dry Channel 3 simultaneously. As is clear from FIG. 20 Working
Air 4, for example, outside air is directed along Dry Channel 3 in
contact with liquid desiccant 47. As the desiccant 47 dries the
Working Air 4 the heat of absorption is transferred to heat
exchange wall 7. In so doing, the Working Air 4 is cooled, reduced
in moisture content and then it is turned to the Wet Channel 5. In
Wet Channel 5 it flows counter currently in contact with the
regenerating liquid desiccant 10 that absorbs this heat. To create
the needed vapor pressure difference between the Dry Channel 3 and
the Wet Channel 5 a large pressure difference between the Dry
Channel 3 and the Wet Channel 5 is caused by a pressure reduction
baffle 73, a forced draft fan 74, and a induced draft fan 11 Liquid
desiccant 47, after it's passing along Dry Channel 3, (see FIG. 20)
increases its temperature and moisture, and it is drained into tray
52. Hereafter, it is directed by the pump 51 (via the pipe 50) to
the Wet Channel 5, where this liquid desiccant flows down in the
manner of the moving film 10 Liquid desiccant 10, after it's
passing along the Wet Channel 5, reduces its temperature and
moisture and it is selected to the tray 53 for the Wet Channel 5.
Hereafter, it is directed by the pump 49 (via the pipe 48) to Dry
Channel 3, where this liquid desiccant flows down in the manner of
the moving film 47. The parameters of tile incoming desiccant 47 to
Dry Channel 3 (low temperature and moisture) help to improve the
absorption process. Product Fluid 2 is directed to the Product Heat
Exchanger 39 for heat exchange contact with liquid desiccant 10.
Liquid desiccant 10 is directed from the heat exchange apparatus 39
by the pump 49 (via the pipe 48) to Dry Channel 3. FIG. 21 is like
FIG. 20 except a Product Channel 1 is used in lieu of a Product
Heat Exchanger 39, (see FIG. 20.
[0127] To increase the Product cooling capacity tile Working Air 4
can be heated prior to entering or moving through Dry Channel 3 and
water added to desiccant 10 before Wet Channel 5.
[0128] Product 2 air may need to be further cooled in a separate
evaporative cooling apparatus 54 as shown in FIG. 22.
[0129] FIGS. 1-22 illustrate the direction of movement of the
Working Air 4 in Dry Channel 3 or the Product Fluid 2 in the
Product Channel 1 is parallel and in counter flow of the direction
of movement of the Working Air 4 in tile Wet Channel 5. The
channels must be parallel however they can be in cross flow or some
mix between cross and counter flow. For example, FIG. 23 shows
cross flow directions between flows of the Working Air 4 in Dry
Channel 3 and the Wet Channels 5. From a strict thermodynamic
standpoint counter flow is more efficient however, there are many
designs that are more economical to fabricate and the geometry more
easily to work with when using cross flow.
[0130] FIG. 24 illustrates an example of a flow diagram of the
present method, where Working Air 4 is redirected from the Dry
Channel 3 into and through the Wet Channel 5, for example, through
a plurality of spaced perforations or permeable pores formed in the
heat exchange surface 9 of the working membrane 7.
[0131] This action can help to increase the coefficient of heat
transfer between flows of the Working Air 4 in the Dry 3 and Wet 5
Channels. Also, it can better help to transport absorbed water by
solid desiccant material 46 (see FIGS. 6-9 and 9a) from tile Dry 3
to the Wet 5 Channels.
[0132] The heat exchange apparatus with multiple channels for
effecting the method, according to the invention (see FIGS. 1, 2,
6-11 and 17-19), where the moving liquid film 10 flows down only
along the Wet Channel 5), is shown in FIG. 25. This apparatus
comprises a jacket 12 with an inlet connection 13 for the Product
Fluid and an inlet connection 14 with an adjustable damper 21 for
Working Air provided at one end of a jacket 12. At tile other end
of a jacket 12 provisions are made for an outlet connection 15 for
the Product Fluid supplied to tile consumer.
[0133] The outlet connection 15 is fitted with an adjustable damper
16. Close to the inlet connection 13 of tile Product Fluid
provision is made for an outlet connection 17 for exhaust Working
Air. The connection 17 is made in tile upper portion of a jacket
12, which will become clear from subsequent description. In a
jacket 12 are placed through Wet Channels 22 for Working Air with a
wetted capillary-porous material on surfaces, which flows down
liquid, for example, liquid desiccant. The liquid desiccant is
served in Wet Channels 22 from a liquid distributor 19. Thereto as
well in a jacket 12 are placed through Product Channels 23 and
through Dry Channels 24 limited by a moisture-proof material.
[0134] In the exemplary embodiment of the invention shown in FIG.
25 tile Wet Channels 22 and also the Product Channels 23 and Dry
Channel 24 are made in the form, for example, of plates or
corrugated plates.
[0135] It follows from FIG. 25, that Working Air passes through Dry
Channel 24 and then Wet Channel 22 with the Product Channel 23
between them and in heat transfer contact with both. The Product
Channels 23 project with one end outside the limits of the Wet
Channels 22 and are fixed by these ends in a baffle-board 25 to
form a blind chamber 26 limited by the baffle-board 25 and the
walls of a jacket 12. The blind chamber 26 provides a tray 18 for
liquid, for example, water after its passing through the Wet
Channels 22. The valve 20 uses for output of this liquid.
[0136] Further consideration of FIG. 25 shows that the Dry Channels
24 for Working Air and the Product Channels 23 also project beyond
the Wet Channels 22 on the side of the inlet connection 13 of the
Product Fluid and these projecting ends at the channels 23 and 24
are secured in the baffle-boards 27, 28. Herewith a chamber 29 for
removing waste Working Air is formed between the end surface of the
Wet Channels 22 and the baffle-board 27 and a chamber 29
communicates with the outlet connection 17. Moreover, a chamber 30
is formed between the baffle-boards 27 and 28, which communicate
with the inlet 14 for introducing Working Air, for example, the
atmospheric air, although this chamber is optional and in the
present exemplary embodiment of the invention is dictated only by
the convenience of arranging the apparatus components.
[0137] Mounted in the inlet connection 13 is a fan or pump 31 (FIG.
25) for forcing the product, for example air or some other gas or
liquid through the Product Channels 23. It is obvious that a pump
or any other means known to those familiar with transporting other
media can be used to inject or convey liquid. It is clear from FIG.
25 that in the outlet connection 17 there is mounted an induced
draft fan 32 for transporting Working Air.
[0138] The above-described heat exchange apparatus operates as
follows. A fan 31 injects the Product Fluid, for example, air, thus
conveying the air along the Product Channels 23. As the air passes
along these channels, it is cooled without a change in its moisture
content and then via the outlet connection 15 is supplied to the
consumer. The adjustable damper 16 regulates the flow rate of the
Product Fluid.
[0139] Working Air is simultaneously fed via the inlet connection
14 where the forced draft fan 33 can be mounted, in the given case
it is the atmospheric air, flowing along the Dry Channels 24. At
the section of the Dry Channels 24 being in the chamber 29 this air
is previously cooled do to the heat exchange with the air being fed
to the chamber 29 from the Wet Channels 22. Here, the air moves in
cross-flow with respect to the channels 24 and is pulled off by a
fan 32 to the atmosphere via the outlet connection 17.
[0140] Having previously cooled in the channels 24 at their
sections arranged in the chamber 29, the flow of Working Air is
further cooled as it moves along the channels 24 to account for the
evaporation of water, in the Wet Channels 22.
[0141] In the blind chamber 26 the Working Air is turned 180
degrees, as is shown by arrows in FIG. 25, to head for the Wet
Channels 22.
[0142] As the Working Air flows in the Wet Channels 22, heat
exchange occurs with the Product Fluid moving in countercurrent in
the Dry Channels 24 and the Product Channels 23 via the walls of
these channels. As a result of such processes the flow of the
product and Working Air is cooled to the dew point of the air
entering without a change in its moisture content. The Working Air
in the Wet Channels 22 is heated (as a result of heat extraction
from Product fluid (air) being cooled in the Product Channels 23
and from itself after passing through the Dry Channels 24,) and is
moistened (as a result of water evaporation in the Wet Channels
22.) Thereupon, the Working Air, coming out of the Wet Channels 22,
enters the chamber 29, where it cross-currently comes into a heat
exchange with both fluid (air) being cooled in the channels 23 and
the incoming flow of the Working Air in the channels 24. A result
of this heat exchange contact such that the both flows (in Product
Channels 23 and Dry Channels 24) are precooled, while the Working
Air (being removed from the Wet Channels 22) is heated about to
temperatures of incoming flows and in this condition is pulled off
into the atmosphere by means of a fan 32 via the outlet connection
17.
[0143] In the heat exchange apparatus, according to the invention,
the product fluid and the Working Air are separated from each
other. This makes it possible to transport the Working Air with the
aid of an induced draft fan 32, which enables one to use the head
loss in the cooling flow to intensity evaporation cooling.
[0144] Because during the passage of the Working Air first along
the dry 24 and after the wet 22 channels as a result of the effect
of different aerodynamic resistance, its head will decline
(particularly, after the turn 180 degrees into the Wet Channels 22)
the pressure drop in the flow core results, respectively, in a
decline of partial pressure of water vapor. This, in turn, enhances
the effect of moisture evaporation into tile flow, which leads to
greater efficiency of cooling the fluid.
[0145] In the above-described heat exchange apparatus it is
expedient that the Dry Channels 24 for Working Air be restricted to
a developed heat exchange surface. This brings about a more
substantial decline in the head of the Working Airflow increasing
the efficiency of cooling, and simultaneously increases the
specific value of the heat exchange surface, which reduces the
overall dimensions of the apparatus and enhances the efficiency of
cooling.
[0146] FIG. 26, is like FIG. 25, (see also FIGS. 3-5, 12-15,
20-22,) where the moving liquid film 10 flows down not only along
the Wet Channels 5 but also along the Dry Channels 3 simultaneously
but with the added ability to wet the Dry Channels with a liquid
such as a desiccant. In the same way the Product Channel and could
have this wetting system added also. The dry channels have had
wetting system 58 added with liquid collection system added 60 with
piping and valve 59 to be used for redistribution.
[0147] There are several designs where the increase in pressure
drop between the Dry and Wet Channels is desirable and to that end
a pressure reduction baffle 34 is shown. The most obvious uses for
this baffle are when the regeneration of the desiccant is used in
tile Wet Channels 22 and a drying desiccant is used in the Dry
Channels. The combination of pressure reduction baffle 34 and
forced draft fan 33 cause a large difference in pressure and
therefore large difference in vapor pressure between the Wet and
Dry Channels allowing the drying of air in the Dry Channel 24 and
evaporation of water from the air in the Wet Channel 22. This same
pressure difference may also be needed when a solid desiccant is
used in the Dry Channel and water is used in the Wet Channel as
pressure difference will create a vapor drive from the Dry to Wet
Channel forcing moisture through the porous walls from the solid
desiccant to be evaporated in the Wet Channel.
[0148] Sometimes, it is expedient when the plates of the heat
exchange apparatus between the Dry 24 and Wet 22 Channels for
Working Air comprise the perforations or permeable pores.
[0149] The present heat exchange apparatuses can work alone and
together with conventional heat and mass exchange equipment
depending on the claims of the present method would like to be
realized.
[0150] In the present method of indirect-evaporation cooling this
heat exchange apparatus, according to the invention, it is possible
to cool air, gas, refrigerant, steam, liquid, and any material,
which can be transported along channels. The different variations
of this apparatus are useful because they permit cooling gaseous,
liquid and dispersed materials without high-energy cost for
cooling. In additional all these materials can be cooled lower then
the dew point temperature of outside air without using high energy
cost of complex refrigeration machines. This process of cooling in
the present method of indirect-evaporation cooling and a heat
exchange apparatus uses significantly less energy due to the use of
natural psychometric difference of temperature and moisture of
outside air.
COMPARATIVE EXAMPLE
[0151] For purposes of illustrating the advantages of the apparatus
and method disclosed herein, the applicants take the results using
the apparatus disclosed in Russian patent No. 2046257 (Maisotsenko)
[copied in U.S. Pat. No. 5,187,946]. We compare the results using
the apparatus shown in FIG. 3 in Table #1.
[0152] The materials as used in the test of FIG. 3 are a wicking
material on the wet surfaces made of cellulose blended fiber sold
by Ahistrom Paper Group, Grade 1278 (0.2969 mm thickness), backed,
for the dry side of the membrane, with 5 mil Mylar callendered with
an adhesive (appropriate for the material).
[0153] This material is the best readily available product, though
other materials may be used, such as an absorbent material, such as
polypropylene with a polyethylene coating which was available from
Ahistrom as Grade 4002. Another combination, using polyethylene
coating on the Grade 1278, would have additional advantages.
[0154] The advantage of Grade 1278 is that it is specifically a
wicking material with a high klein test of approximately 55,
compared to polypropylene whose klem test is 26.
[0155] If the working air 4 enters the apparatus at 122
M.sup.3/hour having a dry-bulb temperature (tdb) of 35.4.degree. C.
and a wet-bulb temperature (twb) of 22.8.degree. C. The stream of
the working air 4 flows through the dry channel 3 where the
desiccant 47 (aqueous lithium chloride solution with concentration
43.4%) absorbs water vapor from the working air 4 and transmits
heat through the wall 7 to the water 10 of the wet channel 5
evaporating into the working air 4.
[0156] The continual cooling of the desiccant 47 in channel 3
increases the working air 4 drying capabilities.
[0157] Simultaneously the product air 2 (outside air) enters the
product channel 1 at 125 M.sup.3/hour having the same temperature
parameters like working air 4. The stream of the product air 2
after its passing through product channel 1 having a dry-bulb
temperature (tdb) of 10.1.degree. C. and wet-bulb temperature (twb)
of 8.2.degree. C. The aerodynamic losses of the total air streams
from inlet (for this test was used one fan) to discharge is 127 Pa.
A 25 watt fan propels the air. The total surface area of tile heat
transfer surface is 0.672 M.sup.2.
[0158] For purposes of comparison, the apparatus disclosed in
Russian patent No. 2046257 ( and the same U.S. Pat. No. 5,187,946)
was used to cool a stream of ambient air (working air) having the
same approximate thermal characteristics. An incoming working air
flow of 240 M.sup.3/hour having a dry-bulb temperature 35.1.degree.
C. and a wet-bulb temperature of 22.6.degree. C. was directed to an
equal surface area of 0.672 M.sup.2. After the dry channel pass the
incoming flow is split with the redirected secondary air stream of
119 M.sup.3/hour going to the wet channel resulting in 121
M.sup.3/hour (as a product air) directed to the user. When this
apparatus was employed as taught, aerodynamic losses of 105 Pa
resulted and necessitated a 22 watt fan. The product air directed
to the user had a dry-bulb temperature of 19.1.degree. C. and a
wet-bulb temperature of 17.6.degree. C. By comparing the claimed
and known methods we can see that we can get much less temperature
of the product air (10.1.degree. C.) compare with 19.1.degree. C.
using known method. The following Table #1 summarizes the above
comparison and additional regime with another parameters of outside
air wherein the initial air is drier. Likewise, the method as
claimed here results in lower temperature of the product air.
1 TABLE #1 Air Flow Temperature, degree .degree.C. M.sup.e/hour
Working Air Product Air Pressure Working Product Inlet Outlet Drop,
Energy for Air Air tdb twb tdb twb Pa Fan, watt 1. Claimed Method
122 125 35.4 22.8 10.1 8.2 127 25 (see FIG. 3) Known (*) Method 240
121 35.1 22.6 19.1 17.6 105 22 U.S. Pat. No. 5,187,946 Or Russian
Pat. No. 2046257 2. Claimed Method 125 127 26.5 16.7 7.7 4.0 127 25
(see FIG. 3) Known (*) Method 239 120 26.1 16.3 14.8 11.9 105 22
U.S. Pat. No. 5,187,946 Or Russian Pat. No. 2046257
[0159] The Comparison illustrates the benefits of indirect cooling
and by a single flow, first pre-cooled in the dry channel, and
dehumidified, and then used in the wet channel to remove heat into
latent heat in the vapor. The product is indirectly cooled by the
wet channel flow.
* * * * *