U.S. patent application number 14/212097 was filed with the patent office on 2014-09-18 for methods and systems for mini-split liquid desiccant air conditioning.
This patent application is currently assigned to 7AC Technologies, Inc.. The applicant listed for this patent is 7AC Technologies, Inc.. Invention is credited to Peter F. Vandermeulen.
Application Number | 20140260399 14/212097 |
Document ID | / |
Family ID | 51521130 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140260399 |
Kind Code |
A1 |
Vandermeulen; Peter F. |
September 18, 2014 |
METHODS AND SYSTEMS FOR MINI-SPLIT LIQUID DESICCANT AIR
CONDITIONING
Abstract
A split liquid desiccant air conditioning system is disclosed
for treating an air stream flowing into a space in a building. The
split liquid desiccant air-conditioning system is switchable
between operating in a warm weather operation mode and a cold
weather operation mode.
Inventors: |
Vandermeulen; Peter F.;
(Newburyport, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
7AC Technologies, Inc. |
Beverly |
MA |
US |
|
|
Assignee: |
7AC Technologies, Inc.
Beverly
MA
|
Family ID: |
51521130 |
Appl. No.: |
14/212097 |
Filed: |
March 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61783176 |
Mar 14, 2013 |
|
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Current U.S.
Class: |
62/271 |
Current CPC
Class: |
F24F 3/1411 20130101;
F24F 3/1417 20130101; F24F 1/00077 20190201 |
Class at
Publication: |
62/271 |
International
Class: |
F24F 3/14 20060101
F24F003/14 |
Claims
1. A split liquid desiccant air conditioning system for treating an
air stream flowing into a space in a building, said split liquid
desiccant air-conditioning system being switchable between
operating in a warm weather operation mode and a cold weather
operation mode, the split liquid desiccant air conditioning system
comprising: a conditioner located inside the building, said
conditioner including a plurality of structures arranged in a
substantially vertical orientation, each structure having at least
one surface across which a liquid desiccant can flow, each
structure also including a passage through which a heat transfer
fluid can flow, wherein the air stream to be treated flows between
the structures such that the liquid desiccant dehumidifies and
cools the air stream in the warm weather operation mode and
humidifies and heats the air stream in the cold weather operation
mode, the conditioner further comprising a sheet of material
positioned proximate to the at least one surface of each structure
between the liquid desiccant and the air stream, said sheet of
material permitting transfer of water vapor between the liquid
desiccant and the air stream; a regenerator located outside the
building connected to the conditioner by liquid desiccant pipes for
exchanging liquid desiccant with the conditioner, said regenerator
including a plurality of structures arranged in a substantially
vertical orientation, each structure having at least one surface
across which the liquid desiccant can flow, each structure also
including a passage through which a heat transfer fluid can flow,
said regenerator causing the liquid desiccant to desorb water in
the warm weather operation mode and to absorb water in the cold
weather operation mode to or from an air stream flowing through the
regenerator; a reversible heat pump located outside the building
coupled to the conditioner and to the regenerator by heat transfer
fluid pipes, wherein the heat pump pumps heat from the heat
transfer fluid flowing in the conditioner to the heat transfer
fluid flowing in the regenerator in the warm weather operation
mode, and wherein the heat pump pumps heat from the heat transfer
fluid flowing in the regenerator to the heat transfer fluid flowing
in the conditioner in the cold weather operation mode; an apparatus
for moving the air stream through the conditioner; an apparatus for
circulating the liquid desiccant through the conditioner and
regenerator; and an apparatus for circulating heat transfer fluid
through the conditioner and the reversible heat pump; and an
apparatus for circulating heat transfer fluid through the
regenerator and the reversible heat pump.
2. The system of claim 1, wherein the reversible heat pump
comprises a refrigerant evaporator heat exchanger.
3. The system of claim 1, wherein the liquid desiccant pipes
comprise a first pipe for transferring liquid desiccant from the
conditioner to the regenerator and a second pipe for transferring
liquid desiccant from the regenerator to the conditioner, wherein
the first and second pipes are in close thermal contact to
facilitate heat transfer from the liquid desiccant flowing in one
of the first and second pipes to the liquid desiccant flowing in
the other of the first and second pipes.
4. The system of claim 3, wherein the first and second pipes
comprise an integrally formed structure.
5. The system of claim 4, wherein the integrally formed structure
comprises a polymer material.
6. The system of claim 5, wherein at least a wall of the structure
between the first and second pipes comprises a thermally conductive
polymer.
7. The system of claim 1, wherein the conditioner is mounted on a
wall inside the building.
8. The system of claim 1, wherein the conditioner has a generally
flat configuration adapted to be hidden behind a computer display,
television, or painting.
9. The system of claim 1, further comprising one or more additional
conditioners in the building, each coupled to the regenerator and
the heat pump.
10. A split liquid desiccant air conditioning system for cooling
and dehumidifying an air stream flowing into a space in a building,
the split liquid desiccant air conditioning system comprising: a
conditioner located inside the building, said conditioner including
a plurality of first structures arranged in a substantially
vertical orientation, each structure having at least one surface
across which a liquid desiccant can flow, each structure also
including a passage through which a heat transfer fluid can flow,
wherein the air stream flows between the structures such that the
liquid desiccant dehumidifies and cools the air stream, the
conditioner further comprising a sheet of material positioned
proximate to the at least one surface of each structure between the
liquid desiccant and the air stream, said sheet of material
permitting transfer of water vapor between the liquid desiccant and
the air stream; a regenerator located outside the building
connected to the conditioner by liquid desiccant pipes for
exchanging liquid desiccant with the conditioner, said regenerator
including a plurality of second structures arranged in a
substantially vertical orientation, each structure having at least
one surface across which the liquid desiccant can flow, each
structure also including a passage through which a heat transfer
fluid can flow, said regenerator causing the liquid desiccant to
desorb water to an air stream flowing through the regenerator; an
indirect evaporative cooling unit coupled to the conditioner for
receiving the heat transfer fluid that has flowed through the first
structures and a portion of the air stream that has been
dehumidified and cooled by the conditioner, said indirect
evaporative cooling unit including a plurality of third structures
arranged in a substantially vertical orientation, each structure
having at least one surface across which water is flowed, each
structure also including a passage through which the heat transfer
fluid from the conditioner is flowed, wherein the portion of the
air stream received from the conditioner flows between the
structures such that the water is evaporated by the air stream,
resulting in cooling of the heat transfer fluid which is returned
to the conditioner, and wherein the air stream treated by the
indirect evaporative cooling unit is exhausted to the atmosphere;
an apparatus for moving the air stream through the conditioner and
the indirect evaporative cooling unit; an apparatus for circulating
the liquid desiccant through the conditioner and regenerator; and
an apparatus for circulating heat transfer fluid through the
conditioner and the indirect evaporative cooling unit; and a heat
source for heating the heat transfer fluid in the regenerator.
11. The system of claim 10, wherein the liquid desiccant pipes
comprise a first pipe for transferring liquid desiccant from the
conditioner to the regenerator and a second pipe for transferring
liquid desiccant from the regenerator to the conditioner, wherein
the first and second pipes are in close contact to facilitate heat
transfer from the liquid desiccant flowing in one of the first and
second pipes to the liquid desiccant flowing in the other of the
first and second pipes.
12. The system of claim 11, wherein the first and second pipes
comprise an integrally formed structure.
13. The system of claim 12, wherein the integrally formed structure
comprises a polymer material.
14. The system of claim 13, wherein at least a wall of the
structure between the first and second pipes comprises a thermally
conductive polymer.
15. The system of claim 10, wherein the conditioner is mounted on a
wall inside the building.
16. The system of claim 10, wherein the conditioner has a generally
flat configuration adapted to be hidden behind a computer display,
television, or painting.
17. The system of claim 10, wherein the indirect evaporative
cooling unit is located inside the building.
18. The system of claim 10, wherein the indirect evaporative
cooling unit is located outside the building.
19. The system of claim 10, wherein the heat source for heating the
heat transfer fluid in the regenerator comprises a gas water
heater, a solar module, a solar thermal/photovoltaic module, or a
steam loop.
20. A split liquid desiccant air conditioning system for heating
and humidifying an air stream flowing into a space in a building,
the split liquid desiccant air conditioning system comprising: a
conditioner located inside the building, said conditioner including
a plurality of first structures arranged in a substantially
vertical orientation, each structure having at least one surface
across which a liquid desiccant can flow, each structure also
including a passage through which a heat transfer fluid can flow,
wherein the air stream flows between the structures such that the
liquid desiccant humidifies and heats the air stream, the
conditioner further comprising a sheet of material positioned
proximate to the at least one surface of each structure between the
liquid desiccant and the air stream, said sheet of material
permitting transfer of water vapor between the liquid desiccant and
the air stream; a regenerator located outside the building
connected to the conditioner by liquid desiccant pipes for
exchanging liquid desiccant with the conditioner, said regenerator
including a plurality of second structures arranged in a
substantially vertical orientation, each structure having at least
one surface across which the liquid desiccant can flow, each
structure also including a passage through which a heat transfer
fluid can flow, said regenerator causing the liquid desiccant to
absorb water from an air stream flowing through the regenerator; an
indirect evaporative cooling unit coupled to the conditioner for
receiving the heat transfer fluid that has flowed through the first
structures and a portion of the air stream that has been humidified
and heated by the conditioner, said indirect evaporative cooling
unit including a plurality of third structures arranged in a
substantially vertical orientation, each structure having at least
one surface across which water is flowed, each structure also
including a passage through which the heat transfer fluid from the
conditioner is flowed, wherein the portion of the air stream
received from the conditioner flows between the structures such
that the water vapor is evaporated from the water, resulting in
humidification of the air stream, and wherein the air stream
treated by the indirect evaporative cooling unit is exhausted
inside the building; an apparatus for moving the air stream through
the conditioner and the indirect evaporative cooling unit; an
apparatus for circulating the liquid desiccant through the
conditioner and regenerator; and an apparatus for circulating heat
transfer fluid through the conditioner and the indirect evaporative
cooling unit; and a heat source for heating the heat transfer fluid
in the conditioner and the indirect evaporative cooling unit.
21. The system of claim 20, wherein the liquid desiccant pipes
comprise a first pipe for transferring liquid desiccant from the
conditioner to the regenerator and a second pipe for transferring
liquid desiccant from the regenerator to the conditioner, wherein
the first and second pipes are in close contact to facilitate heat
transfer from the liquid desiccant flowing in one of the first and
second pipes to the liquid desiccant flowing in the other of the
first and second pipes.
22. The system of claim 21, wherein the first and second pipes
comprise an integrally formed structure.
23. The system of claim 22, wherein the integrally formed structure
comprises a polymer material.
24. The system of claim 23, wherein at least a wall of the
structure between the first and second pipes comprises a thermally
conductive polymer.
25. The system of claim 20, wherein the conditioner is mounted on a
wall inside the building.
26. The system of claim 20, wherein the conditioner has a generally
flat configuration adapted to be hidden behind a computer display,
television, or painting.
27. The system of claim 20, wherein the indirect evaporative
cooling unit is located inside the building.
28. The system of claim 20, wherein the indirect evaporative
cooling unit is located outside the building.
29. The system of claim 20, wherein the heat source for heating the
heat transfer fluid in the conditioner and the indirect evaporative
cooling unit comprises a gas water heater, a solar module, a solar
thermal/photovoltaic module, or a steam loop.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Patent Application No. 61/783,176 filed on Mar. 14, 2013 entitled
METHODS AND SYSTEMS FOR MINI-SPLIT LIQUID DESICCANT AIR
CONDITIONING, which is hereby incorporated by reference.
BACKGROUND
[0002] The present application relates generally to the use of
liquid desiccants to dehumidify and cool, or heat and humidify an
air stream entering a space. More specifically, the application
relates to the replacement of conventional mini-split air
conditioning units with (membrane based) liquid desiccant air
conditioning system to accomplish the same heating and cooling
capabilities as those conventional mini-split air conditioners.
[0003] Desiccant dehumidification systems--both liquid and solid
desiccants--have been used parallel to conventional vapor
compression HVAC equipment to help reduce humidity in spaces,
particularly in spaces that require large amounts of outdoor air or
that have large humidity loads inside the building space itself.
(ASHRAE 2012 Handbook of HVAC Systems and Equipment, Chapter 24, p.
24.10). Humid climates, such as for example Miami, Fla. require a
lot of energy to properly treat (dehumidify and cool) the fresh air
that is required for a space's occupant comfort. Desiccant
dehumidification systems--both solid and liquid--have been used for
many years and are generally quite efficient at removing moisture
from the air stream. However, liquid desiccant systems generally
use concentrated salt solutions such as ionic solutions of LiCl,
LiBr or CaCl.sub.2 and water. Such brines are strongly corrosive,
even in small quantities, so numerous attempts have been made over
the years to prevent desiccant carry-over to the air stream that is
to be treated. In recent years efforts have begun to eliminate the
risk of desiccant carry-over by employing micro-porous membranes to
contain the desiccant. These membrane based liquid desiccant
systems have been primarily applied to unitary rooftop units for
commercial buildings. However, residential and small commercial
buildings often use mini-split air conditioners wherein the
condenser is located outside and the evaporator cooling coil is
installed in the room or space than needs to be cooled, and unitary
rooftop units are not an appropriate choice for servicing those
spaces.
[0004] Liquid desiccant systems generally have two separate
functions. The conditioning side of the system provides
conditioning of air to the required conditions, which are typically
set using thermostats or humidistats. The regeneration side of the
system provides a reconditioning function of the liquid desiccant
so that it can be re-used on the conditioning side. Liquid
desiccant is typically pumped between the two sides, and a control
system helps to ensure that the liquid desiccant is properly
balanced between the two sides as conditions necessitate and that
excess heat and moisture are properly dealt with without leading to
over-concentrating or under-concentrating the desiccant.
[0005] In many smaller buildings a small evaporator coil is hung
high up on a wall or covered by a painting as for example the LG
LAN126HNP Art Cool Picture frame. A condenser is installed outside
and high pressure refrigerant lines connect the two components.
Furthermore a drain line for condensate is installed to remove
moisture that is condensed on the evaporator coil to the outside. A
liquid desiccant system can significantly reduce electricity
consumption and can be easier to install without the need for high
pressure refrigerant lines that need to be installed on site.
[0006] Mini-split systems typically take 100% room air through the
evaporator coil and fresh air only reaches the room through
ventilation and infiltration from other sources. This often can
result in high humidity and cool temperatures in the space since
the evaporator coil is not very efficient for removing moisture.
Rather, the evaporator coil is better suited for sensible cooling.
On days where only a small amount of cooling is required the
building can reach unacceptable levels of humidity since not enough
natural heat is available to balance the large amount of sensible
cooling.
[0007] There thus remains a need to provide a retrofitable cooling
system for small buildings with high humidity loads, wherein the
cooling and dehumidification of indoor air can be accommodated at
low capital and energy costs.
BRIEF SUMMARY
[0008] Provided herein are methods and systems used for the
efficient cooling and dehumidification of an air stream especially
in small commercial or residential buildings using a mini-split
liquid desiccant air conditioning system. In accordance with one or
more embodiments, the liquid desiccant flows down the face of a
support plate as a falling film. In accordance with one or more
embodiments, the desiccant is contained by a microporous membrane
and the air stream is directed in a primarily vertical orientation
over the surface of the membrane and whereby both latent and
sensible heat are absorbed from the air stream into the liquid
desiccant. In accordance with one or more embodiments, the support
plate is filled with a heat transfer fluid that ideally is flowing
in a direction counter to the air stream. In accordance with one or
more embodiments, the system comprises a conditioner that removes
latent and sensible heat through the liquid desiccant into the heat
transfer fluid and a regenerator that rejects the latent and
sensible heat from the heat transfer fluid to the environment. In
accordance with one or more embodiments, the heat transfer fluid in
the conditioner is cooled by a refrigerant compressor or an
external source of cold heat transfer fluid. In accordance with one
or more embodiments, the regenerator is heated by a refrigerant
compressor or an external source of hot heat transfer fluid. In
accordance with one or more embodiments, the refrigerant compressor
is reversible to provide heated heat transfer fluid to the
conditioner and cold heat transfer fluid to the regenerator and the
conditioned air is heat and humidified and the regenerated air is
cooled and dehumidified. In accordance with one or more
embodiments, the conditioner is mounted against a wall in a space
and the regenerator is mounted outside of the building. In
accordance with one or more embodiments, the regenerator supplies
liquid desiccant to the conditioner through a heat exchanger. In
one or more embodiments, the heat exchanger comprises two desiccant
lines that are bonded together to provide a thermal contact. In one
or more embodiments, the conditioner receives 100% room air. In one
or more embodiments, the regenerator receives 100% outside air. In
one or more embodiments, the conditioner and evaporator are mounted
behind a flat screen TV or flat screen monitor or some similar
device.
[0009] In accordance with one or more embodiments a liquid
desiccant membrane system employs an indirect evaporator to
generate a cold heat transfer fluid wherein the cold heat transfer
fluid is used to cool a liquid desiccant conditioner. Furthermore
in one or more embodiments, the indirect evaporator receives a
portion of the air stream that was earlier treated by the
conditioner. In accordance with one or more embodiments, the air
stream between the conditioner and indirect evaporator is
adjustable through some convenient means, e.g., through a set of
adjustable louvers or through a fan with adjustable fan speed. In
one or more embodiments, the water supplied to the indirect
evaporator is potable water. In one or more embodiments, the water
is seawater. In one or more embodiments, the water is waste water.
In one or more embodiments, the indirect evaporator uses a membrane
to prevent carry-over of non-desirable elements from the seawater
or waste water. In one or more embodiments, the water in the
indirect evaporator is not cycled back to the top of the indirect
evaporator such as would happen in a cooling tower, but between 20%
and 80% of the water is evaporated and the remainder is discarded.
In one or more embodiments, the indirect evaporator is mounted
directly behind or directly next to the conditioner. In one or more
embodiments, the conditioner and evaporator are mounted behind a
flat screen TV or flat screen monitor or some similar device. In
one or more embodiments, the exhaust air from the indirect
evaporator is exhausted out of the building space. In one or more
embodiments, the liquid desiccant is pumped to a regenerator
mounted outside the space through a heat exchanger. In one or more
embodiments, the heat exchanger comprises two lines that are
thermally bonded together to provide a heat exchange function. In
one or more embodiments, the regenerator receives heat from a heat
source. In one or more embodiments, the heat source is a solar heat
source. In one or more embodiments, the heat source is a gas-fired
water heater. In one or more embodiments, the heat source is a
steam pipe. In one or more embodiments, the heat source is waste
heat from an industrial process or some other convenient heat
source. In one or more embodiments, the heat source can be switched
to provide heat to the conditioner for winter heating operation. In
one or more embodiments, the heat source also provides heat to the
indirect evaporator. In one or more embodiments, the indirect
evaporator can be directed to provide humid warm air to the space
rather than exhausting the air to the outside.
[0010] In accordance with one or more embodiments, the indirect
evaporator is used to provide heated, humidified air to a supply
air stream to a space while a conditioner is simultaneously used to
provide heated, humidified air to the same space. This allows the
system to provide heated, humidified air to a space in winter
conditions. The conditioner is heated and is desorbing water vapor
from a desiccant and the indirect evaporator can be heated as well
and is desorbing water vapor from liquid water. In combination the
indirect evaporator and conditioner provide heated humidified air
to the building space for winter heating conditions.
[0011] In no way is the description of the applications intended to
limit the disclosure to these applications. Many construction
variations can be envisioned to combine the various elements
mentioned above each with its own advantages and disadvantages. The
present disclosure in no way is limited to a particular set or
combination of such elements.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 illustrates an exemplary 3-way liquid desiccant air
conditioning system using a chiller or external heating or cooling
sources.
[0013] FIG. 2 shows an exemplary flexibly configurable membrane
module that incorporates 3-way liquid desiccant plates.
[0014] FIG. 3 illustrates an exemplary single membrane plate in the
liquid desiccant membrane module of FIG. 2.
[0015] FIG. 4 shows a schematic of a conventional mini-split air
conditioning system.
[0016] FIG. 5A shows a schematic of an exemplary chiller assisted
mini-split liquid desiccant air conditioning system in a summer
cooling mode in accordance with one or more embodiments.
[0017] FIG. 5B shows a schematic of an exemplary chiller assisted
mini-split liquid desiccant air conditioning system in a winter
heating mode in accordance with one or more embodiments.
[0018] FIG. 6 shows an alternate embodiment of a mini-split liquid
desiccant air conditioning system using an indirect evaporative
cooler and an external heat source in accordance with one or more
embodiments.
[0019] FIG. 7 shows the liquid desiccant mini-split system of FIG.
6 configured for operation in a winter heating mode in accordance
with one or more embodiments.
[0020] FIG. 8 is a perspective view of an exemplary liquid
desiccant mini-split system similar to FIG. 5A.
[0021] FIG. 9A illustrates a cut-away rear-view of the system of
FIG. 8.
[0022] FIG. 9B illustrates a cut-away front-view of the system of
FIG. 8.
[0023] FIG. 10 shows a three dimensional view of a liquid desiccant
mini-split system of FIG. 6 in accordance with one or more
embodiments.
[0024] FIG. 11 shows a cut-away view of the system of FIG. 10 in
accordance with one or more embodiments.
[0025] FIG. 12 illustrates an exemplary liquid desiccant supply and
return structure comprising two bonded plastic tubes creating a
heat exchange effect in accordance with one or more
embodiments.
DETAILED DESCRIPTION
[0026] FIG. 1 depicts a new type of liquid desiccant system as
described in more detail in U.S. Patent Application Publication No.
US 20120125020, which is incorporated by reference herein. A
conditioner 101 comprises a set of plate structures that are
internally hollow. A cold heat transfer fluid is generated in cold
source 107 and entered into the plates. Liquid desiccant solution
at 114 is brought onto the outer surface of the plates and runs
down the outer surface of each of the plates. The liquid desiccant
runs behind a thin membrane that is located between the air flow
and the surface of the plates. Outside air 103 is now blown through
the set of wavy plates. The liquid desiccant on the surface of the
plates attracts the water vapor in the air flow and the cooling
water inside the plates helps to inhibit the air temperature from
rising. The treated air 104 is put into a building space.
[0027] The liquid desiccant is collected at the bottom of the wavy
plates at 111 and is transported through a heat exchanger 113 to
the top of the regenerator 102 to point 115 where the liquid
desiccant is distributed across the wavy plates of the regenerator.
Return air or optionally outside air 105 is blown across the
regenerator plate and water vapor is transported from the liquid
desiccant into the leaving air stream 106. An optional heat source
108 provides the driving force for the regeneration. The hot
transfer fluid 110 from the heat source can be put inside the wavy
plates of the regenerator similar to the cold heat transfer fluid
on the conditioner. Again, the liquid desiccant is collected at the
bottom of the wavy plates 102 without the need for either a
collection pan or bath so that also on the regenerator the air flow
can be horizontal or vertical. An optional heat pump 116 can be
used to provide cooling and heating of the liquid desiccant. It is
also possible to connect a heat pump between the cold source 107
and the hot source 108, which is thus pumping heat from the cooling
fluids rather than the desiccant.
[0028] FIG. 2 describes a 3-way heat exchanger as described in
further detail in U.S. patent application Ser. No. 13/915,199 filed
on Jun. 11, 2013, Ser. No. 13/915,222 filed on Jun. 11, 2013, and
Ser. No. 13/915,262 filed on Jun. 11, 2013, which are all
incorporated by reference herein. A liquid desiccant enters the
structure through ports 304 and is directed behind a series of
membranes as described in FIG. 1. The liquid desiccant is collected
and removed through ports 305. A cooling or heating fluid is
provided through ports 306 and runs counter to the air stream 301
inside the hollow plate structures, again as described in FIG. 1
and in more detail in FIG. 3. The cooling or heating fluids exit
through ports 307. The treated air 302 is directed to a space in a
building or is exhausted as the case may be.
[0029] FIG. 3 describes a 3-way heat exchanger as described in more
detail in U.S. Provisional Patent Application Ser. No. 61/771,340
filed on Mar. 1, 2013, which is incorporated by reference herein.
The air stream 251 flows counter to a cooling fluid stream 254.
Membranes 252 contain a liquid desiccant 253 that is falling along
the wall 255 that contain a heat transfer fluid 254. Water vapor
256 entrained in the air stream is able to transition the membrane
252 and is absorbed into the liquid desiccant 253. The heat of
condensation of water 258 that is released during the absorption is
conducted through the wall 255 into the heat transfer fluid 254.
Sensible heat 257 from the air stream is also conducted through the
membrane 252, liquid desiccant 253 and wall 255 into the heat
transfer fluid 254.
[0030] FIG. 4 illustrates a schematic diagram of a conventional
mini-split air conditioning system as is frequently installed on
buildings. The unit comprises a set of indoor components that
generate cool, dehumidified air and a set of outdoor components
that release heat to the environment. The indoor components
comprise a cooling (evaporator) coil 401 through which a fan 407
blows air 408 from the room. The cooling coil cools the air and
condenses water vapor on the coil which is collected in drain pan
418 and ducted to the outside 419. The resulting cooler, drier air
409 is circulated into the space and provides occupant comfort. The
cooling coil 401 receives liquid refrigerant at pressures of
typically 50-200 psi through line 412, which has already been
expanded to a low temperature and pressure by expansion valve 406.
The pressure of the refrigerant in line 412 is typically 300-600
psi. The cold liquid refrigerant 410 enters the cooling coil 401
where it picks up heat from the air stream 408. The heat from the
air stream evaporates the liquid refrigerant in the coil and the
resulting gas is transported through line 404 to the outdoor
components and more specifically to the compressor 402 where it is
re-compressed to a high pressure of typically 300-600 psi. In some
instances the system can have multiple cooling coils 410, fans 407
and expansion valves 406, for example a cooling coil assembly could
be located in various rooms that need to be cooled.
[0031] Besides the compressor 402, the outdoor components comprise
a condenser coil 403 and a condenser fan 417. The fan 417 blows
outside air 415 through the condenser coil 403 where it picks up
heat from the compressor 402 which is rejected by air stream 416.
The compressor 402 creates hot compressed refrigerant in line 411.
The heat of compression is rejected in the condenser coil 403. In
some instances the system can have multiple compressors or multiple
condenser coils and fans. The primary electrical energy consuming
components are the compressor through electrical line 413, the
condenser fan electrical motor through supply line 414 and the
evaporator fan motor through line 405. In general the compressor
uses close to 80% of the electricity required to operate the
system, with the condenser and evaporator fans taking about 10% of
the electricity each.
[0032] FIG. 5A illustrates a schematic representation of a liquid
desiccant air conditioner system. A 3-way conditioner 503 (which is
similar to the conditioner 101 of FIG. 1) receives an air stream
501 from a room ("RA"). Fan 502 moves the air 501 through the
conditioner 503 wherein the air is cooled and dehumidified. The
resulting cool, dry air 504 ("SA") is supplied to the room for
occupant comfort. The 3-way conditioner 503 receives a concentrated
desiccant 527 in the manner explained under FIGS. 1-3. It is
preferable to use a membrane on the 3-way conditioner 503 to ensure
that the desiccant is generally fully contained and is unable to
get distributed into the air stream 504. The diluted desiccant 528,
which contains the captured water vapor is transported to the
outside regenerator 522. Furthermore the chilled water 509 is
provided by pump 508, enters the conditioner module 503 where it
picks up heat from the air as well as latent heat released by the
capture of water vapor in the desiccant 527. The warmer water 506
is also brought outside to the heat exchanger 507 on the chiller
system 530. It is worth noting that unlike the mini-split system of
FIG. 4, which has high pressure between 50 and 600 psi, the lines
between the indoor and outdoor system of FIG. 5A are all low
pressure water and liquid desiccant lines. This allows the lines to
be inexpensive plastics rather than refrigerant lines in FIG. 4,
which are typically copper and need to be braised in order to
withstand the high refrigerant pressures. It is also worth noting
that the system of FIG. 5A does not require a condensate drain line
like line 419 in FIG. 4. Rather, any moisture that is condensed
into the desiccant is removed as part of the desiccant itself. This
also eliminates problems with mold growth in standing water that
can occur in the conventional mini-split systems of FIG. 4.
[0033] The liquid desiccant 528 leaves the conditioner 503 and is
moved through the optional heat exchanger 526 to the regenerator
522 by pump 525. If the desiccant lines 527 and 528 are relatively
long they can be thermally connected to each other, which
eliminates the need for heat exchanger 526.
[0034] The chiller system 530 comprises a water to refrigerant
evaporator heat exchanger 507 which cools the circulating cooling
fluid 506. The liquid, cold refrigerant 517 evaporates in the heat
exchanger 507 thereby absorbing the thermal energy from the cooling
fluid 506. The gaseous refrigerant 510 is now re-compressed by
compressor 511. The compressor 511 ejects hot refrigerant gas 513,
which is liquefied in the condenser heat exchanger 515. The liquid
refrigerant 514 then enters expansion valve 516, where it rapidly
cools and exits at a lower pressure. It is worth noting that the
chiller system 530 can be made very compact since the high pressure
lines with refrigerant (510, 513, 514 and 517) only have to run
very short distances. Furthermore, since the entire refrigerant
system is located outside of the space that is to be conditioned,
it is possible to utilize refrigerants that normally cannot be used
in indoor environments such as by way of example, CO.sub.2, Ammonia
and Propane. These refrigerants are sometimes preferable over the
commonly used R410A, R407A, R134A or R1234YF refrigerants, but they
are undesirable indoor because of flammability or suffocation or
inhaling risks. By keeping all of the refrigerants outside, these
risks are essentially eliminated. The condenser heat exchanger 515
now releases heat to another cooling fluid loop 519 which brings
hot heat transfer fluid 518 to the regenerator 522. Circulating
pump 520 brings the heat transfer fluid back to the condenser 515.
The 3-way regenerator 522 thus receives a dilute liquid desiccant
528 and hot heat transfer fluid 518. A fan 524 brings outside air
523 ("OA") through the regenerator 522. The outside air picks up
heat and moisture from the heat transfer fluid 518 and desiccant
528 which results in hot humid exhaust air ("EA") 521.
[0035] The compressor 511 receives electrical power 512 and
typically accounts for 80% of electrical power consumption of the
system. The fan 502 and fan 524 also receive electrical power 505
and 529 respectively and account for most of the remaining power
consumption. Pumps 508, 520 and 525 have relatively low power
consumption. The compressor 511 will operate more efficiently than
the compressor 402 in FIG. 4 for several reasons: the evaporator
507 in FIG. 5A will typically operate at higher temperature than
the evaporator 401 in FIG. 4 because the liquid desiccant will
condense water at much higher temperature without needing to reach
saturation levels in the air stream. Furthermore the condenser 515
in FIG. 5A will operate at lower temperatures than the condenser
403 in FIG. 4 because of the evaporation occurring on the
regenerator 522 which effectively keeps the condenser 515 cooler.
As a result the system of FIG. 5A will use less electricity than
the system of FIG. 4 for similar compressor isoentropic
efficiencies.
[0036] FIG. 5B shows essentially the same system as FIG. 5A except
that the compressor 511's refrigerant direction has been reversed
as indicated by the arrows on refrigerant lines 514 and 510.
Reversing the direction of refrigerant flow can be achieved by a
4-way reversing valve (not shown) or other convenient means. It is
also possible to instead of reversing the refrigerant flow to
direct the hot heat transfer fluid 518 to the conditioner 503 and
the cold heat transfer fluid 506 to the regenerator 522. This will
in effect provide heat to the conditioner which will now create
hot, humid air 504 for the space for operation in winter mode. In
effect the system is now working as a heat pump, pumping heat from
the outside air 523 to the space supply air 504. However unlike the
system of FIG. 4, which is oftentimes also reversible, there is
much less of a risk of the coil freezing because the desiccant 525
usually has much lower crystallization limit than water vapor. In
the system of FIG. 4, the air stream 523 contains water vapor and
if the condenser coil 403 gets too cold, this moisture will
condense on the surfaces and create ice formation on those
surfaces. The same moisture in the regenerator of FIG. 5B will
condense in the liquid desiccant which--when managed properly will
not crystallize until -60.degree. C. for some desiccants such as
LiCl and water.
[0037] FIG. 6 illustrates an alternate embodiment of a mini-split
liquid desiccant system. Similar to FIG. 5A, a 3-way liquid
desiccant conditioner 503 receives an air stream 501 ("RA") moved
by fan 502 through the conditioner 503. However unlike the case of
FIG. 5A, a portion 601 of the supply air stream 504 ("SA") is
directed towards an indirect evaporative cooling module 602 through
sets of louvers 610 and 611. Air stream 601 is usually between 0
and 40% of the flow of air stream 504. The dry air stream 601 is
now directed through the 3-way indirect evaporative cooling module
602 which is constructed similarly to the 3-way conditioner module
503, except that instead of using a desiccant behind a membrane,
the module now has a water film behind such membrane supplied by
water source 607. This water film can be potable water, non-potable
water, seawater or waste water or any other convenient water
containing substance that is mostly water. The water film
evaporates in the dry air stream 601 creating a cooling effect in
the heat transfer fluid 604 which is then circulated to the
conditioner module as cold heat transfer fluid 605 by pump 603. The
cold water 605 then cools the conditioner module 503, which in turn
creates cooler drier air 504, which then results in an even
stronger cooling effect in the indirect evaporative module 602. As
a result the supply air 504 will ultimately be both dry and cold
and is supplied to the space for occupant comfort. Conditioner
module 503 also receives a concentrated liquid desiccant 527 that
absorbs moisture from the air stream 501. Dilute liquid desiccant
528 is then returned to the regenerator 522 similar to FIG. 5A. It
is of course possible to locate the indirect evaporative cooler 602
outside of the space rather than inside, but for thermal reasons it
is probably better to mount the indirect evaporator 602 in close
proximity to the conditioner 503. The indirect evaporative cooling
module 602 does not evaporate all of the water (typically 50 to
80%) and thus a drain 608 is employed. The exhaust air stream 606
("EA1") from the module evaporative cooling module 602 is brought
to the outside since it is warm and very humid.
[0038] As in FIG. 5A, the concentrated liquid desiccant 527 and
dilute liquid desiccant 528 pass through a heat exchanger 526 by
pump 525. As before one can thermally connect the lines 527 and 528
which eliminates the need for heat exchanger 526. The 3-way
regenerator 522 as before receives an outdoor air stream 523
through fan 524. And as before a hot heat transfer fluid 518 is
applied to the 3-way regenerator module 522 by pump 520. However
unlike the system of FIG. 5A, there is no heat from a compressor to
use in the regenerator 522, so an external heat source 609 needs to
be provided. This heat source can be a gas water heater, a solar
module, a solar thermal/PV hybrid module (a PVT module), it can be
heat from a steam loop or other convenient source of heat or hot
water. In order to prevent over-concentration of the desiccant 528,
a supplemental heat dump 614 can be employed which can temporarily
absorb heat from the heat source 609. An additional fan 613 and air
stream 612 are then necessary as well. Of course other forms of
heat dumps can be devised and may not always be required. The heat
source 609 ensures that the excess water is evaporated from the
desiccant 528 so that it can be re-used on the conditioner 503. As
a result the exhaust stream 521 ("EA2") comprises hot, humid air.
It is worth noting that again no high pressure lines are needed
between the indoor and outside components of the system. A single
water line for water supply is needed and a drain line for the
removal of excess water. However a compressor and heat exchanger
are no longer required in this embodiment. As a result this system
will use significantly less electricity than the system of FIG. 4
and the system of FIG. 5A. The major consumption of electricity are
now the fans 502 and 524 through electrical supply lines 505 and
529 respectively and the liquid pumps 603, 520 and 525. However
these devices consume considerably less power than the compressor
402 in FIG. 4.
[0039] FIG. 7 illustrates the system of FIG. 6 reconfigured
slightly to allow for operation in winter heating mode. The heat
source 609 now provides hot heat transfer fluid to the conditioner
module 503 through lines 701. As a result the supply air to the
space 504 will be warm and humid. It is also possible to provide
hot heat transfer fluid 703 to the indirect evaporative cooler 602
and to direct the hot, humid exhaust air 702 to the space rather
than to the outside. This increases the available heating and
humidification capacity of the system since both the conditioner
503 and the indirect evaporative "cooler" 602 (or "heater" may be a
better moniker) are operating to provide the same hot humid air and
this can be handy since heating capacity in winter typically needs
to be larger than cooling capacity in summer.
[0040] FIG. 8 shows an embodiment of the system of FIG. 5A. The air
intake 801 allows for air from space 805 to enter the conditioner
unit 503 (not shown). The air supply exits from roster 803 into the
space. A flat screen television 802 or painting, or monitor or any
other suitable device can be used to visually hide the conditioner
503. An external wall 804 would be a logical place to mount the
conditioner system. A regenerator and chiller system 807 can be
mounted in a convenient outside location 806. Desiccant supply and
return lines 809 and cold heat transfer fluid supply and return
lines 808 connect the two sides of the system.
[0041] FIG. 9A shows a cut-away view of the rear side of the system
in FIG. 8. The regenerator module 522 receives liquid desiccant
from lines 809. A compressor 511 an expansion valve 516 and two
refrigerant to liquid heat exchangers 507 and 515 are also shown.
Other components have not been shown for convenience.
[0042] FIG. 9B shows a cut-away view of the front side of the
system in FIG. 8. The flat screen TV 802 has been omitted to allow
a view of the conditioner module 503.
[0043] FIG. 10 shows an aspect of an embodiment of the system of
FIG. 6. The system has an air intake 801 and a supply roster 803
similar to the system of FIG. 8. As in FIG. 8, a TV 802 or
something similar can be used to cover the conditioner module 503.
The unit can be mounted to wall 804 and provide conditioning of the
space 805. The system also has an exhaust 606 that penetrates the
wall 804. On the outside 806, the regenerator module 902 provides
concentrated liquid desiccant to the conditioner section (not
shown) through desiccant supply and return lines 809. A water
supply line 901 is also shown. A source of hot heat transfer fluid
can be the solar PVT module 903 which provides hot water through
line 905 which after being cooled through the regenerator returns
heat transfer fluid to the PVT module 903 through line 904. An
integrated hot water storage tank 906 can provide both a hot water
buffer as well as a ballast for the PVT module 903.
[0044] FIG. 11 shows a cut-away view of the system of FIG. 10. The
conditioner module 503 can be clearly seen as can the indirect
evaporator module 602. Inside the regenerator module 902 one can
see the regenerator module 522 as well as the optional heat dump
614 and fan 612.
[0045] FIG. 12 illustrates a structure 809 for the supply and
return of the liquid desiccant to the indoor conditioning unit. The
structure comprises a polymer material such as for example an
extruded High Density Polypropylene or High Density Polyethylene
material the comprises two passages 1201 and 1202 for the supply
and return of desiccant respectively. The wall 1203 between the two
passages could be manufactured from a thermally conductive polymer,
but in many cases that may not be necessary because the length of
the structure 809 is by itself sufficient to provide adequate heat
exchange capacity between the supply and return liquids.
[0046] Having thus described several illustrative embodiments, it
is to be appreciated that various alterations, modifications, and
improvements will readily occur to those skilled in the art. Such
alterations, modifications, and improvements are intended to form a
part of this disclosure, and are intended to be within the spirit
and scope of this disclosure. While some examples presented herein
involve specific combinations of functions or structural elements,
it should be understood that those functions and elements may be
combined in other ways according to the present disclosure to
accomplish the same or different objectives. In particular, acts,
elements, and features discussed in connection with one embodiment
are not intended to be excluded from similar or other roles in
other embodiments. Additionally, elements and components described
herein may be further divided into additional components or joined
together to form fewer components for performing the same
functions. Accordingly, the foregoing description and attached
drawings are by way of example only, and are not intended to be
limiting.
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