A system for cooling and gases in which the process gas is dehumidified
in a desiccant module and subsequently treated in a heat exchanger.
Additional heat exchanger and gas washers may be included in the
system. The system is operable in either an open or closed system
to generate either cold gas or cold fluid or both. In a preferred
embodiment, the heat exchanger has a dry channel in which both sensible
and adiabatic gas cooling occurs and an adjacent counterflow wet
channel. The desiccant may be either a liquid or solid and is regenerated.
1. A closed loop process for treatment of a process air stream
for generation of both a chilled water supply and a chilled air
supply, said process comprising the steps of:
(a) initially contacting the process air stream with a desiccant
in a desiccant module to remove moisture from the process air stream
resulting in a dried process air stream;
(b) directing the dried process air stream to an initial air-to-water
heat exchanger to sensibly cool the process air stream, said initial
air-to-water heat exchanger being in communication with cooling
water from a cooling tower;
(c) directing the process air exiting the initial heat exchanger
through successive heat exchangers to further gradually cool the
process air stream, said successive heat exchangers being provided
cooling water from an air washer;
(d) directing the process air stream discharged from the said successive
heat exchangers to the said air washer to contact and chill the
fluid therein, said chilled fluid collecting in a sump in said air
(e) directing a part of the chilled fluid from the sump of the
air washer to said successive heat exchanges and a part to a secondary
heat exchanger for remote use in a closed loop; and
(f) redirecting at least a part of air from the air washer to said
desiccant module as part of the process air stream.
2. The process of claim 1 wherein the process is carried out as
an open system and wherein the air stream is ambient air and cool
air is generated.
3. The process of claim 1 wherein a part of the cooled air is returned
to the system and cool water is generated in said direct cooling
4. The process of claim 1 wherein said evaporative cooling stage
includes an evaporative media with a water supply for wetting the
5. The process of claim 1 wherein said cooled supply gas is air
and the air is subjected to treatment in a counter-flow air washer
having an upper water distribution manifold and a lower sump.
6. The process of claim 1 wherein said air washer has a water distributor.
The present invention relates to a gas treatment method and more
particularly to a unique system for fluid and gas cooling which
utilizes water as a refrigerant instead of conventional refrigerants
containing environmentally harmful CFC's or HCFC's.
Conditioning of air to cool the air to create a zone of increased
comfort or for maintaining the zone at a lower temperature is well
known. Refrigeration devices operating on the compression cycle
using a refrigerant such as freon are also widely used. Compression
cycle systems require considerable energy consumption and are expensive
in both initial cost and maintenance. More importantly, environmental
problems have been attributed to compression systems as these systems
utilize a great deal of energy and also are believed to contribute
to environmental pollution. CFC molecules, such as CFCl.sub.3 (freon
11) and CFCl.sub.2 (freon 12) released to the atmosphere from compression
cycle refrigeration systems may enter into photochemical reactions
with the ozone layer which may destroy this environmentally necessary
layer of protection.
Another method is direct evaporative air cooling which avoids the
use of CFC containing refrigerants. Direct evaporative cooling has
wide application particularly in drier climates and is widely practiced
and accepted since it is relatively simple approach requiring low
energy consumption. The principle of evaporative cooling to cool
air is based on the evaporation of water to absorb the latent heat
of vaporization from the air which reduces the air temperature and
increases the humidity of the air. However, direct evaporative cooling
has an inherent limitation due to the fact that when the humidity
of the air flow reaches saturation, the temperature and partial
pressure is equalized and the heat and mass exchange process ceases.
Other methods, in an attempt to avoid use of potentially harmful
refrigerants, employ indirect evaporative cooling methods which
utilize heat exchangers having a dry surface along which the air
flows, the opposite of which is cooled by evaporated water. A system
of this type is shown in my prior patent, U.S. Pat. No. 5050391.
Desiccant systems are also known and represent a viable alternative
to compression cycle systems. A desiccant system utilizes a composition
which removes moisture from the air or gas passing through the desiccant.
Various patents can be found in the prior art which employ both
solid and liquid desiccant components. For example, U.S. Pat. No.
4171620 discloses a cooling method and system in which a stream
of wet, warm air is passed in contact with a liquid hygroscopic
material in a water-cooled absorbent zone to produce a stream of
relatively cool, dry air. The cool, dry air is then passed through
an evaporative cooling zone in contact with water and the resulting
cooled air or water is used as a cooling and refrigerating media.
The method and apparatus also facilitates mass exchange between
the gas and the liquid.
U.S. Pat. No. 4864830 discloses an air conditioning apparatus
and process with absorption of water vapor and a circulating absorption
liquid containing an aqueous salt solution. The absorption liquid
to be supplied to the absorber is cooled by indirect contact with
a circulating water stream in a heat exchanger.
U.S. Pat. No. 4786301 shows a desiccant air conditioning system
having a heat exchanging desiccant bed defining air passageways
and liquid circulating channels for circulating heat transfer of
liquid in heat exchange relationship with the desiccant bed.
U.S. Pat. No. 4982575 discloses a dehumidification and cooling
apparatus for air conditioning. Dehumidification of air and reactivation
of spent desiccant is achieved by the energy of the outdoor air.
As indicated above, there has been a renewed interest in alternate
cooling systems which are capable of achieving relatively low temperatures.
The present invention provides an efficient method and apparatus
in which air is treated with a desiccant.
Briefly, the method and apparatus of the present invention are
used for fluid or gas cooling and are based on the use of water
as a refrigerant instead of CFC's or HCFC's and which system operates
at atmospheric or near atmospheric pressures. The driving force
of the cycle is heat. The system may be an open or closed loop cycle
depending upon ambient conditions and the required temperature level
of the generated cooling media. In the closed system of operation,
the cooling unit may be filled with air, hydrogen, helium or other
mixtures of gases. Accordingly, although the term "air"
is used, it is understood to encompass other gases as indicated.
Similarly, the term "water" is used herein as being representative
of various fluids that may be chilled, such as water, brine solutions
and the like. The system is used to generate either cold fluid or
cold gas, or both.
In a preferred embodiment, process air is directed through a pre-cooling
air-to-water heat exchanger, a desiccant dehumidification module,
and a second air-to-water heat exchanger. Both heat exchangers receive
cooling water from a cold water source which may be a cooling tower
or other available source such as a body of cold water. The process
air stream is then directed to an indirect/direct evaporative air/water
cooler in which the air is first subjected to sensible cooling as
the air stream is passed through heat exchange tubes surrounded
by wetted evaporative media and a portion of the sensibly cooled
air is directed through the evaporative media surrounding the tubes
and is subjected to evaporative cooling. A secondary loop circulates
water from a sump in the heat exchanger to a liquid-to-liquid heat
exchanger for secondary cold water generation.
In other embodiments, the air stream may be directed through a
dehumidification module and a series of air-to-water heat exchangers.
The air is cooled in the air-to-water heat exchanger and the air
is then directed to an air washer to cool the water. A portion of
the cold water from the air washer is circulated via the water-to-water
heat exchanger directly to a remote use.
In still other alternate embodiments the air stream is first subjected
to desiccant dehumidification and subsequent treatment including
cooling in an indirect heat exchanger having adjacent wet and dry
channels in which a portion of the process air is redirected countercurrently
through the wet channel.
The above and other objects, advantages and features of the present
invention will become more apparent from the following description,
claims and drawings in which:
FIG. 1 is a schematic flow chart of a preferred embodiment of the
present invention employing air pre-cooling and a cooling tower.
The system will generate either cold water or cold air;
FIGS. 1A and 1B are psychrometric charts representative of both
the open and closed circuit process carried out by the apparatus
of the present invention as shown in FIG. 1;
FIG. 2 is a schematic flow chart of another embodiment of the present
invention employing a desiccant dehumidification module, air-to-liquid
heat exchangers, air washer, cooling tower and optional heat exchangers;
FIGS. 2A and 2B are psychrometric charts representative of open
and closed circuit process carried out by the system of FIG. 2;
FIG. 3 is a schematic illustrating still another embodiment of
the present invention employing a liquid desiccant; and
FIGS. 3A and 3B are psychrometric charts representative of both
open and closed circuits carried out by the system of FIG. 3.
The apparatus and method of the present invention are utilized
for cooling of fluid and gas and use water as a refrigerant in place
of refrigerants containing CFC's or HCFC's. The driving force in
the cycle is heat and the required energy to operate the processes
is less than that required with conventional heat absorption or
steam ejection systems of comparable capacity. The system of the
present invention is not limited in geographical or climatic application.
The working pressure in the system of the present invention is
nearly atmospheric and remains essentially constant. This enables
the components to be manufactured at relatively low cost. The system
may also function with various brine solutions or various other
low boiling point liquids. The gas cavity of the cooling unit may
contain air, hydrogen, helium or any other specially selected mixture
of gases although as indicated the term "air" is used
for convenience of the description set forth. The term "water"
is also used for convenience to denote various fluids. The system
may operate on an open or closed-loop cycle depending on outdoor
conditions and the required temperature level of the generated cooling
media. The system can be utilized to generate cold gas, cold fluid
or a combination of the two.
FIG. 1--General Description
Turning now to the drawings, particularly FIG. 1 a preferred form
of the invention is shown and is generally designated by the numeral
100 which includes an air mover 110 having an inlet 114 controlled
by an air damper 112A.
The air mover discharges an air stream into a housing 118 of heat
exchanger and desiccant module 120 which module contains a first
air-to-water heat exchanger 122 a dehumidification module 124 and
a second stage air-to-water heat exchanger 126. The housing 118
is shown as having divergent sections 120A, 120B and a converging
section 120C, although it will be appreciated that the housing may
be of any convenient shape or may consist of separate modular units
suitably interconnected. Similarly, the design and configuration
of the heat exchangers may be a conventional tube, radiator or other
type which are well known to those skilled in the arts.
Cooling water is introduced into air-to-water heat exchanger section
122 at inlet 122A and circulated through internal heat exchange
members as is well known. The water exits the heat exchanger at
122B. As will be explained hereafter, cooling water is supplied
to the heat exchanger from any available source such as cooling
tower 170 and the heated water exiting the heat exchanger at discharge
122B is returned to the cooling tower to be cooled. Other sources
of cooling water may be utilized if available such as lake water,
river water, ocean water or cool water resulting from a separate
Dehumidification module 124 is located downstream from the first
stage heat exchanger 122. The dehumidification module 124 contains
a suitable desiccant material selected from materials which are
well known and may consist of silica gel, a molecular sieve, zeolite
material, aluminum oxide or similar materials. The dehumidification
module is preferably regenerable including, as for example, an electric
heating element 125 to regenerate the desiccant material when saturated
as is well known. Heat for regeneration may also be provided by
other energy sources such as natural gas, solar radiation, steam,
hot water from another process of the like.
The second stage air-to-water heat exchanger 126 receives the dehumidified
air discharged from the dehumidification module 124. Heat exchanger
126 is similar in construction to heat exchanger 122 and receives
cooling water at inlet 126A which is circulated through the heat
exchanger elements and discharged at 126B. The inlet and outlet
of the heat exchanger 126 are suitably connected to cooling tower
170 or other source of cooling water.
The air discharged from the second stage heat exchanger 126 is
directed to evaporative air/water cooler 130 via duct 131. The cooler
130 includes an exterior housing 132 which has a sump or basin 133
having a horizontal floor 135. A plurality of heat exchange tubes
134 are vertically disposed within the housing and extend through
the floor 135 of the basin. The tubes are suitably sealed around
their exterior to prevent leakage from the sump. A body of porous
evaporative media 138 fills the area around the heat transfer tubes
134. The upper end of the heat transfer tubes 134 communicate with
upper plenum chamber 140 and the lower ends receive the air exiting
the heat exchanger 126 in duct 131. A lower plenum 136 is defined
between the basin and the bottom surface of the media 138. Air from
plenum may be directed to a point of use across damper 112P or returned
to air mover 110 via duct 196 and dampers 112B and 112C. Air from
plenum 136 may be directed to use at 190 across damper 112A or to
the air mover via duct 196 across damper 122L.
Pump 142 has an inlet which communicates with the water in sump
133 at conduit 144. The pump 142 discharges cold water into water-to-water
heat exchanger 150 which may be of known construction. The water
discharged from the heat exchanger 150 is directed by return conduit
154 to a water distribution system 152 located above the upper surface
of the porous evaporative media 138 but below the upper distal end
of the heat exchange tubes 134. Water to be chilled is delivered
to heat exchanger 150 via conduit 162 and indirectly contacted with
the fluid from the module 130 with the cold water supply being available
at heat exchanged discharge 164 from where it may be directed to
a point of use.
As indicated, various sources of cooling water may be utilized
and a conventional cooling tower 170 is shown providing cooling
water to the heat exchanger sections 122 and 126. The cooling tower
has an exterior housing 172 containing evaporative media 175. Water
distribution manifold 176 discharges across the upper surface of
the evaporative media 175. As is conventional, an air mover or fan
178 at the upper end of the cooling tower induces a flow of air
upwardly through the evaporative media. A sump or water basin 180
is located at the lower end of the tower beneath the evaporative
media. Warm water discharged from heat exchangers 122 and 126 is
directed via conduits 182 and 184 to common conduit 186 supplying
the cooling tower water distribution system 176. The water is cooled
as it flows through the evaporative media 175 due to the well known
evaporative effect. The cooled water collects in sump 180 and from
there is supplied to the respective inlets 122A and 126A of the
air-to-water heat exchangers 122 and 126 by means of pump 188 connected
to the sump via conduit 190.
The cooling system of FIG. 1 operates to generate either cold water
or cold air. The operation of the system will be first described
with reference to cold water generation.
FIG. 1 and FIG. 1B--Cold Water Generation (Closed Cycle)
In operation in this mode, the inlet air stream supplied to air
mover or fan 110 is 100% recirculated, process air from plenum 136
and, in some cases, from plenum 140. The dampers 112A, 112G and
112P are closed. Damper 112L is open. Damper 112B may be closed
or partially open.
The process air fan 110 discharges recirculated air through the
first stage pre-cooling air-to-water heat exchanger 122 which transfers
heat to the circulating water stream flowing from the cooling tower
via conduit 190. The air stream then flows through the desiccant
humidification module 124 where the air is dehumidified and some
heating of the air occurs. It will be noted that various points
of entry and discharge in the system are indicated on FIG. 1 by
a circled number and letter. The appended letter "B" appearing
on FIG. 1B represents a closed system. The appended letter "A"
indicates the conditions of the air at various locations in an open
system as shown in FIG. 1A of the accompanying psychrometric chart.
As for example, the conditions of the air entering the fan 110 when
operating as a closed system are indicated by the designation .circle.
After dehumidification and heating in module 124 indicated by
point .circle. 2B on FIG. 1B, the air stream is directed to the
second air-to-water heat exchanger 126 where it is cooled to conditions
.circle. 3B due to heat transfer with the water circulating through
the heat exchanger. As indicated, cooling water is supplied to the
inlet 122A and 124A of both heat exchanger sections from the cooling
tower 170. The water discharged from the heat exchangers 122 and
124 which has been heated is returned via conduit 186 to the cooling
tower for cooling and recycling.
After exiting the heat exchanger and desiccant module, the process
air is directed into the evaporative air/water cooler 130 where
it passes through an array of heat transfer tubes 134. The heat
transfer tubes are surrounded by a porous evaporative media 138
which is wetted by water distributed from the manifold 152 at the
upper surface of the evaporative media. The water flows downwardly
through the evaporative media and is collected in the sump 133 at
the lower end of the cooling unit 130. Water is recirculated from
sump 133 by means of pump 142 through the heat exchanger 150 and
eventually is circulated back to the distribution manifold 152.
As indicated above, the tubes depend through the floor of the sump
into the plenum 131. The tubes are sealed around their exterior
where they penetrate the sump floor. The process air exiting the
heating exchanger 126 enters the lower end of the tubes below the
sump and flows through the heat transfer tubes. Sensible cooling
occurs as the air passes through the tubes as heat is transferred
through the tube walls to the wetted evaporative media and the water
within the sump.
The sensibly cooled air is discharged at the lowest temperature
at the upper end of the heat transfer tubes and is reversely directed
downwardly through the porous evaporative cooling media. The warmed
air exits the evaporative media in the lower plenum 136 located
beneath the porous media and above the water level in the sump.
The heat-mass transfer process occurs during contact between the
cold air and the water within the evaporative media resulting in
cooling of the water and warming of the air. The warmed and humid
air stream then exits the plenum 136 and via ducts 195 and 196 returns
to the air mover 110.
The cold water from the sump 133 flows through the heat exchanger
150 as indicated. This water is termed the "primary" cold
water. A secondary water loop supplies a fluid at inlet 162 from
a desired remote heat transfer application. As the secondary water
is pumped through the heat exchanger 150 the water or fluid is
chilled as heat is transferred into the cold generating system described.
Thus, cold fluid exits the heat exchanger at discharge 164 for remote
As indicated, FIG. 1B illustrates the cold water generation process
described in connection with a psychrometric chart with the selected
process points indicated by the corresponding indicia which appear
on FIG. 1.
FIGS. 1 and 1A--Cold Air Generation (Open Cycle)
The system described in FIG. 1 may also be used to generate cold
air and this mode of operation is represented on psychrometric chart
FIG. 1A. In referring to FIG. 1A, various corresponding process
points are shown on FIG. 1 and indicated by a circled number and
letter, i.e. .circle. 1A . In the cold air mode of operation, the
process air stream to be treated is 100% outside air at conditions
as indicated by point .circle. 1A . Liquid-to-liquid heat exchanger
150 remains inactive with pump 142 off. Dampers 112A, 112G and 112P
are open and damper 112L is closed. Damper 112B is either closed
or partially open.
The process air flow and heat exchange through the system is basically
the same as has been described above with reference to cold water
generation. The primary difference is that the air stream is split
after the air exits the heat transfer tubes 134 in the cooler 130
with cold air being discharged across both damper 112P from plenum
140 and also discharges across damper 112G from plenum 136 below
the lower surface of the evaporative media. No return air is directed
to the fan 110 and the primary liquid-to-liquid heat exchanger 150
is off. Cold air is directed to a point of use across dampers 112P
FIG. 2--Closed/Open Cycle W/Air-Liquid Heat Exchanger
FIG. 2 is a schematic view of another embodiment of the system.
FIGS. 2A and 2B are a psychrometric chart showing various process
conditions at open and closed circuit modes of operation, respectively.
The system of FIG. 2 is a closed or open cycle air or water cooler
utilizing a solid desiccant and air-to-water and water-to-water
heat exchangers with an air washer.
FIGS. 2 & 2B Cold Water Generation (Closed Cycle)
The closed cycle of operation for cold water generation will be
initially described. In the closed cycle dampers 250A, 250B and
250C are closed and 250D is open. Fan 202 circulates the air stream
to be treated through desiccant dehumidification module 201. The
conditions of the air entering the fan or air mover corresponds
to .circle. 1A on the accompanying psychrometric chart, FIG. 2B.
The air leaving the module 201 is at conditions indicated at .circle.
2B . The air exiting the dehumidification module 201 enters the
initial air-to-water heat exchanger 204 where the-air is sensibly-cooled
due to heat exchange with the water circulating from the cooling
tower 212. The air exits heat exchanger 204 at conditions indicated
as point .circle. 3B on the accompanying psychrometric chart.
The air stream then flows successively through heat exchanger units
205 206 207 where the air stream temperature is gradually lowered
as indicated on the psychrometric chart. Cooling water for heat
exchangers 205 206 and 207 is provided by cold water generated
in the air washer 220. The air washer has a distribution manifold
222 located in the upper end of housing 224. An evaporative media
228 is contained in the housing beneath the distribution system
and a sump 226 is located at the bottom of the housing and circulates
water to heat exchanger 207 via pump 230. Water exiting heat exchanger
207 is split and is directed to secondary heat exchanger 260 which
may be a water-to-water heat exchanger or water-to-air heat exchanger.
The air flow is split in washer 220 as supply air is discharged
across damper 250B and recirculating air is directed across damper
250D. Damper 250C is closed. In the closed cycle water from sump
226 is split and is directed to both heat exchanger 207 and t secondary
heat exchanger 292. A secondary fluid from a remote source is introduced
into secondary heat exchanger 260 at 262 and returned at 264 for
use at a remote location. The primary water loop of heat exchanger
260 is connected to air-to-water heat exchanger 206 by conduit 266.
Conduit 268 interconnects air-to-water heat exchangers 206 and 205.
The loop is completed by conduit 270 which returns water from second
stage air-to-water heat exchanger 205 to the distribution manifold
222 of the air washer 220.
Cooling tower 212 is a conventional design having a housing 280
which contains an evaporative media 282 and defines a sump 284 in
the bottom of the housing. A fan 285 in a fan housing at the upper
end of the tower induces upward flow of air through the unit. The
cooled water in the sump 284 is directed via pump 288 to first stage
air-to-water heat exchanger 204. The return from heat exchanger
204 flows through conduit 290 to the distribution manifold 292 located
above the upper surface of the media 282.
Cooling liquid for heat exchangers 205 206 and 207 is provided
by the cold water generated in the air washer 220. A portion of
the cold water from the air washer 220 may be also circulated via
conduit 295 to remote heat exchanger 292 from which the warm primary
water enters heat exchanger 205 and then returns to the air washer.
A remote source of fluid to be cooled is introduced to the heat
exchanger 292 at 296 and cooled fluid discharged at 298.
The number of heat exchangers 205 206 and 207 may vary with process
requirements. Similarly, the location of heat exchangers 260 and
292 may vary and may be used to provide a cooled secondary source
of either air or water to the user. Heat exchangers 260 and 292
may be any conventional type of heat exchanger such as a plate or
tube type or other configuration. In the closed system, cold water
is generated for use as a cooling fluid in heat exchangers 260 and
FIGS. 2 and 2A (Open Cycle)
In the open cycle of operation, cold air is generated. The conditions
of the system of FIG. 2 as an open cycle system are shown in FIG.
2A. The various process conditions are represented by points 1B
to 8B on these figures. The process air is entirely outside air
with initial dehumidification occurring across module 201 and successive
incremental cooling occurring across exchangers 204 205 206 and
207. Treated and cooled air is discharged across damper 250C at
conditions .circle. 8B as indicated on FIG. 2B. Damper 250A is open
as are dampers 250C and 250C. Damper 250D is closed and water valve
275 may be open or partially closed.
FIGS. 3 & 3A--Closed/Open Cycle Gas/Liquid Cooler General Description
With Air/Air Heat Exchange & Liquid Desiccant
Referring to FIG. 3 an alternate system according to the invention
is shown which system is generally designated by the numeral 300.
The system of FIG. 3 is capable of generating cold water in the
closed circuit mode and cold air in the open circuit mode of operation.
In the open circuit mode, both cold air and cold water can be simultaneously
In the open circuit mode, the apparatus may use either 100% ambient
air or a mixture of ambient and return air. When 100% ambient air
is supplied to the system, a portion of the conditioned air is supplied
to the user and the other part having been utilized as a heat transfer
medium is exhausted to the outside at 305Y. The system of FIG. 3
includes a process air fan 302 having discharge conduit 304. The
discharge conduit 304 connects with conduit 306 supplying air washer/dryer
308. Air washer/dryer 308 has a water collecting sump 310 located
in its bottom and an intermediate section containing an extended
surface inert media 312. Distributor 314 is located at the upper
end of the housing for distribution and directing a liquid desiccant
downwardly through media 312.
The air exiting the upper end of the washer is directed via conduit
320 to a heat exchanger 330 having a dry channel 324 defined by
a nonporous moistureimpervious barrier or walls 326. A portion of
the sensibly cooled air stream flowing through the dry channel may
be redirected at outlet 328 via conduit 331 to the inlet or fan
302 across dampers 305A and 305L. A channel termed a "wet"
channel 336 is located downstream the dry channel 324. The wet channel
336 is provided on its interior surfaces with a hydrophilic porous
material 334. Dry or sensible cooling occurs along dry channel 324
and adiabatic evaporative cooling occurs through channel 336. The
air discharged from channel 336 is directed either to discharge
across damper 305Y or to air washer 342 through conduit 340 and
across damper 305C. Some air may be directed to channel 370 across
Washer 342 has a housing which defines a sump 344 in its lower
end and an intermediate washing zone 346 which, as is conventional,
contains an extended surface evaporative media. A distributor 348
extends across the upper end of the housing of the washer and cooled
water is supplied from the washer via return line 350 back to the
distributor 348 or to remote water-to-desiccant heat exchanger 352.
Recirculation pump 354 is provided and along with valves 360 362
364 controls the recirculation flow path. Additional make-up water
may be provided from a remote source across valve 362.
The air exiting the upper end of the air washer is delivered via
conduit 366 to the inlet of wet channel 370 of heat exchanger 330.
Wet channel 370 is arranged on the opposite side of a common barrier
or wall parallel with channels 324 and 336. The interior surface
of channel 370 is coated with a hydrophilic, porous media 372.
Auxiliary fan 380 has its inlet connected to an ambient air source
across damper 305K. As indicated in FIG. 3 the inlet also selectively
communicates across dampers 305A and 305M with the air flow exiting
the dry channel 324. A portion or all of the flow through wet channel
370 may be directed to the inlet of primary fan 302 by means of
conduit 384 across damper 305P. Damper 305N is closed. The condenser
390 is part of the desiccant regeneration system.
The system further includes a desiccant-to-desiccant heat exchanger
392 condensate tank 394 generator 396 and steam-to-liquid heat
exchanger 398. Generator 396 is heated by heat source 399 which
may be fueled by any convenient heat source.
In operation, the auxiliary fan 380 supplies air to condenser 390
and/or to wet channel 370. Depending on conditions, dampers 305K
and 305A will be adjusted to provide either 100% outside air or
100% air from dry channel 324 or a mixture of these streams. At
some conditions fan 380 is not operational and main fan 302 supplies
air to the condenser 390 by means of conduits 304 and 385. In this
case, the dampers 305K and 305M are closed and dampers 305J and
305F are open.
FIGS. 3 & 3B (Closed Cycle)
The closed cycle operation of the system of FIG. 3 is represented
on FIGS. 3B. The process conditions are indicated by points .circle.
1B to .circle. 8B . In operation primary fan 302 and auxiliary fan
380 are both energized. Pumps 354 383 391 and 395 are operating
and the generator 396 is energized and supplied with heat at heat
source 399. Air dampers 305C, 305F, 305P, 305K and 305Z are open.
Dampers 305N, 305M, 305G, 305J and 305Y are closed. Dampers 305A,
305D and 305L may be either open, closed or partially open.
The concentrated, cold liquid desiccant solution is sprayed downwardly
in the air washer/dryer 308 by means of distributor 314. The desiccant
solution contacts the air stream flowing countercurrently upwardly
through the desiccant. The interaction between the desiccant solution
and the air stream will result in dehumidification of the air. The
air conditions entering and leaving the washer/dryer 308 are illustrated
in the accompanying psychrometric chart of FIG. 3B by points .circle.
1B and .circle. 2B , respectively. The water enriched desiccant
solution is circulated from the sump at 310 of the washer/dryer
by pump 383 to the heat exchanger 392 and then to the generator
396. Generator 396 is heated by input 399 by an energy source such
as natural gas, solar energy or electricity to maintain the desiccant
solution at boiling conditions. The boiling condition will result
in evaporation of the water from the desiccant solution and increase
the desiccant concentration within the solution. The concentrated
desiccant solution at high heat is circulated from generator 396
by pump 391 through heat exchanger 392 and returns to heat exchanger
352. The heat exchangers 392 and 352 extract excessive heat from
the solution prior to introduction into the air washer/dryer at
The saturated water vapor (steam) at approximately atmospheric
pressure exits heat generator 398 and is directed into air-cooled
condenser 390 where it is condensed. The condensate from the condenser
is collected in tank 394 for use as a water source supplied by pump
395 to wet channels 370 and to the wet media 334 in the adiabatic
evaporization stage 336.
FIGS. 3 & 3A (Open Circuit)
The open cycle operation is similar to the closed circuit and is
represented on FIG. 3A. In the open cycle, ambient air at conditions
typified by conditions 1A is successively treated to provide cold
supply air at conditions .circle. 5A exiting the channel 336. In
the open cycle the dampers are positioned as follow: 305P, 305C
are closed and 305G, 305Y, 305D, 305N, 305Z and 305F are open. Dampers
305J, 305A, 305L, 305M and 305K may be open or closed.
The main air flow is directed primarily through the dry channel
324 of heat exchanger 330. Part of the air exiting the dry channel
may be directed to a point of use across damper 305Y. The air is
dehumidified in washer/dryer 308 prior to cooling the heat exchanger
330. The water from sump 344 of the air washer may be directed to
a point of use via conduit 345. All of the water from the air washer
sump 334 or a mixture of this water with return water from the user
at 362 is supplied by pump 354 may be recirculated to distributor
348 or to the heat exchanger 352.
From the foregoing, it will be seen that the present invention
provides an efficient and versatile system for generating cold gas,
cold fluid or a mixture and which avoids use of conventional, potentially
harmful refrigerants. The system has various operating modes. Accordingly,
various changes and modifications can be made to the system as apparent
to those skilled in the art. The heat exchanger described may be
of various types but counterflow types are preferred as having the
best efficiency. Similarly, counterflow type air washers are preferred.
It will be obvious to those skilled in the art to make various
changes, alterations and modifications to the system described herein.
To the extent such changes, alterations and modifications do not
depart from the spirit and scope of the appended claims, they are
intended to be encompassed therein.