U.S. patent application number 12/627245 was filed with the patent office on 2011-06-02 for absorption chiller and system incorporating the same.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to William Dwight Gerstler, AliciA Jillian Jackson Hardy, Helge Klockow, Sherif Hatem Abdulla Mohamed, Andrew Philip Shapiro, Ching-Jen Tang, Yogen Vishwas Utturkar, Todd Garrett Wetzel, Paul Brian Wickersham.
Application Number | 20110126563 12/627245 |
Document ID | / |
Family ID | 44067823 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110126563 |
Kind Code |
A1 |
Tang; Ching-Jen ; et
al. |
June 2, 2011 |
ABSORPTION CHILLER AND SYSTEM INCORPORATING THE SAME
Abstract
A device, such as an absorption chiller sub-system, is provided.
The absorption chiller sub-system can include an evaporator and an
absorber. The evaporator can be configured to receive a liquid
first working fluid and to produce first working fluid vapor. The
absorber can be configured to receive and combine first working
fluid vapor and a second working fluid, for example, so as to
release thermal energy. A divider having opposing first and second
sides in respective fluid communication with the evaporator and the
absorber can also be included. The divider can be configured to
allow first working fluid vapor to pass therethrough between the
first and second sides and to inhibit movement of liquid first
working fluid therethrough between the first and second sides.
Associated systems and methods are also provided.
Inventors: |
Tang; Ching-Jen;
(Watervliet, NY) ; Gerstler; William Dwight;
(Niskayuna, NY) ; Hardy; AliciA Jillian Jackson;
(Schenectady, NY) ; Klockow; Helge; (Niskayuna,
NY) ; Mohamed; Sherif Hatem Abdulla; (Niskayuna,
NY) ; Shapiro; Andrew Philip; (Schenectady, NY)
; Utturkar; Yogen Vishwas; (Niskayuna, NY) ;
Wetzel; Todd Garrett; (Niskayuna, NY) ; Wickersham;
Paul Brian; (Schenectady, NY) |
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
44067823 |
Appl. No.: |
12/627245 |
Filed: |
November 30, 2009 |
Current U.S.
Class: |
62/102 ; 165/45;
165/62; 62/112; 62/260; 62/478 |
Current CPC
Class: |
Y02B 30/62 20130101;
F24D 3/18 20130101; F25B 15/14 20130101; Y02A 30/27 20180101; F24D
3/02 20130101; Y02A 30/277 20180101; Y02B 30/12 20130101; F24H 4/02
20130101; F25B 15/02 20130101; Y02B 10/40 20130101; F24D 2200/11
20130101; F24D 2200/126 20130101 |
Class at
Publication: |
62/102 ; 62/478;
62/260; 165/45; 165/62; 62/112 |
International
Class: |
F25B 15/00 20060101
F25B015/00; F25B 17/02 20060101 F25B017/02; F25B 27/00 20060101
F25B027/00; F24J 3/08 20060101 F24J003/08; F25B 13/00 20060101
F25B013/00; F25B 15/06 20060101 F25B015/06 |
Claims
1. A device comprising: an evaporator configured to receive a
liquid first working fluid and to produce first working fluid
vapor; an absorber configured to receive and combine first working
fluid vapor and a second working fluid a divider having opposing
first and second sides in respective fluid communication with said
evaporator and said absorber, said divider being configured to
allow first working fluid vapor to pass therethrough between said
first and second sides and to inhibit movement of liquid first
working fluid therethrough between said first and second sides.
2. The device of claim 1, wherein said evaporator is coupled to
said first side of said divider and said absorber is coupled to
said second side of said divider.
3. The device of claim 1, wherein said absorber is configured to
combine at least some first working fluid vapor passing through
said divider and a second working fluid so as to cause at least
some first working fluid vapor passing through said divider to
become liquid.
4. The device of claim 1, wherein said divider includes a
membrane.
5. The device of claim 1, wherein said divider defines holes
therethrough.
6. The device of claim 1, wherein said absorber is configured to
combine at least some first working fluid vapor passing through
said divider and a second working fluid so as to release thermal
energy.
7. The device of claim 1, wherein said absorber is configured to
receive a second working fluid such that an equilibrium second
partial pressure of first working fluid vapor at said second side
is less than a first partial pressure of first working fluid vapor
at said first side.
8. The device of claim 1, wherein said evaporator is configured to
receive liquid NH.sub.3 as the liquid first working fluid.
9. The device of claim 8, wherein said absorber is configured to
receive at least one of water or a mixture of water and NH.sub.3 as
the second working fluid.
10. The device of claim 1, wherein said evaporator is configured
such that a total pressure therein is at least twice a partial
pressure of first working fluid vapor at said first side.
11. The device of claim 10, wherein said absorber is configured
such that a total pressure therein is at least twice a partial
pressure of first working fluid vapor at said second side.
12. The device of claim 1, wherein said evaporator is configured to
receive liquid water and to produce water vapor, and said absorber
is configured to combine water vapor passing through said divider
and a relatively concentrated solution containing lithium bromide
so to produce a relatively diluted solution containing lithium
bromide.
13. The device of claim 12, wherein each of said evaporator and
said absorber is configured such that a respective total pressure
therein is greater than or equal to about atmospheric pressure.
14. The device of claim 12, wherein said divider defines holes
therethrough having diameters less than or equal to about 100
nm.
15. The device of claim 12, wherein said divider is formed at least
partially of substantially hydrophobic material such that holes
defined by said divider are defined by said substantially
hydrophobic material.
16. The device of claim 15, wherein said substantially hydrophobic
material includes at least one of polytetrafluoroethylene,
polypropylene, or polyvinylidene fluoride.
17. The device of claim 12, further comprising: a generator
configured to receive the relatively diluted solution containing
lithium bromide from said absorber and to produce separate outputs
of water vapor and the relatively concentrated solution containing
lithium bromide; and a condenser configured to receive water vapor
from said generator and to provide liquid water to said
evaporator.
18. The device of claim 17, further comprising a second divider
configured to allow water vapor to pass therethrough and to inhibit
movement of liquid water therethrough, wherein said generator and
said condenser are in fluid communication with opposing sides of
said second divider such that water vapor from said generator can
pass through said second divider to said condenser while liquid
water in said generator is substantially prevented from reaching
said condenser.
19. The device of claim 17, further comprising: a geothermal well;
and a heat exchanger, wherein each of said condenser, absorber, and
evaporator are configured to selectively thermally communicate with
said geothermal well and said heat exchanger.
20. The device of claim 19, further comprising a water heater,
wherein said device is configured such that thermal energy is
transferred from said absorber and said condenser into a heated
fluid stream, and thermal energy is transferred from a cooled fluid
stream into the liquid first working fluid, the heated fluid stream
being in selective fluid communication with each of said water
heater, said heat exchanger, and said geothermal well, and the
cooled fluid stream being in selective fluid communication with
each of said heat exchanger and said geothermal well.
21. The device of claim 19, wherein said geothermal well and said
heat exchanger are configured to selectively exchange thermal
energy directly therebetween and to avoid exchanging thermal energy
with each of said generator, condenser, evaporator, and
absorber.
22. A method comprising: providing a device including an
evaporator, an absorber, and a divider having opposing first and
second sides in fluid communication with the evaporator and the
absorber, respectively, and configured to allow first working fluid
vapor to pass therethrough between the first and second sides and
to inhibit movement of liquid first working fluid therethrough
between the first and second sides; providing liquid first working
fluid to the evaporator so as to produce first working fluid vapor
that contacts the first side of the divider; receiving at the
absorber first working fluid vapor passing through the divider from
the first side to the second side and a second working fluid; and
combining in the absorber at least some first working fluid vapor
passing through the divider and the second working fluid.
23. The method of claim 22, wherein said combining at least some
first working fluid vapor passing through the divider and the
second working fluid includes combining at least some first working
fluid vapor passing through the divider and the second working
fluid so as to cause at least some of the first working fluid vapor
passing through the divider to become liquid.
24. The method of claim 22, wherein said combining at least some
first working fluid vapor passing through the divider and the
second working fluid includes combining at least some first working
fluid vapor passing through the divider and the second working
fluid so as to release thermal energy.
25. The method of claim 22, wherein said providing a liquid first
working fluid to the evaporator includes providing liquid water to
the evaporator so as to produce water vapor, and said combining in
the absorber at least some first working fluid vapor and the second
working fluid includes combining at least some water vapor and a
relatively concentrated solution containing lithium bromide.
26. The method of claim 25, wherein said providing liquid water to
the evaporator so as to produce water vapor includes providing
liquid water to the evaporator so as to produce water vapor with a
first partial pressure at the first side, and said receiving at the
absorber a relatively concentrated solution containing lithium
bromide includes receiving at the absorber a relatively
concentrated solution containing lithium bromide such that an
equilibrium second partial pressure of water vapor at the second
side is less than the first partial pressure at the first side.
27. The method of claim 25, wherein said providing a device
includes providing a device that includes a divider formed at least
partially of substantially hydrophobic material and defining holes
therethrough, the holes having diameters less than or equal to
about 100 nm.
28. The method of claim 25, further comprising supplying thermal
energy to a relatively diluted solution containing lithium bromide
so as to cause water to evaporate out and thereby produce the
relatively concentrated solution containing lithium bromide; and
removing thermal energy from the water vapor produced from the
relatively diluted solution containing lithium bromide so as to
produce liquid water to be provided to the evaporator.
29. The method of claim 28, further comprising: selectively
transferring the thermal energy removed from the water vapor
produced from the relatively diluted solution containing lithium
bromide and transferring thermal energy from the absorber to a
heated fluid stream; selectively transferring thermal energy from a
cooled fluid stream to the liquid water circulated to the
evaporator; selectively transferring thermal energy between the
heated fluid stream and at least one of a heat exchanger or a
geothermal well; and selectively transferring thermal energy
between the cooled fluid stream and at least one of the heat
exchanger and the geothermal well.
30. The method of claim 29, further comprising: selecting a target
temperature; and causing, when the target temperature is higher
than a ground temperature of the geothermal well, a geothermal
fluid stream to circulate between the geothermal well and the heat
exchanger without receiving the thermal energy removed from the
water vapor produced from the relatively diluted solution
containing lithium bromide and without exchanging thermal energy
with the absorber.
31. A device comprising: a first working fluid; a second working
fluid; a divider having opposing first and second sides in
respective fluid communication with said evaporator and said
absorber, said divider being configured such that first working
fluid vapor passes therethrough while movement of liquid first
working fluid therethrough is inhibited; an evaporator in fluid
communication with said first side, said evaporator receiving said
first working fluid as liquid first working fluid and producing
first working fluid vapor with a first partial pressure at said
first side; and an absorber that receives said second working fluid
under conditions such that an equilibrium second partial pressure
of first working fluid vapor at said second side is less than the
first partial pressure, such that said first working fluid vapor
moves from said first side to said second side and is combined with
said second working fluid in said absorber.
32. The device of claim 31, wherein said second working fluid is
received in said absorber as liquid second working fluid and
combined with first working fluid vapor passing through said
divider so as to cause at least some of said first working fluid
vapor passing through said divider to become liquid.
33. The device of claim 31, wherein a total pressure in said
evaporator is at least twice the first partial pressure.
Description
BACKGROUND
[0001] Currently, there are approximately one million ground source
geothermal (GSG) systems installed in the U.S., which GSG systems
are utilized in a range of government, commercial, and residential
contexts. Further, approximately 50,000 residential GSG systems are
added each year. The installation cost of GSG systems currently
varies with geographic region, but can be as much as $10,000 per
ton capacity or more. And, while energy savings are expected with
the use of GSG systems as compared to more conventional heating and
cooling systems, the payback period for typical GSG systems is
estimated to range from 5 to 10 years. It may therefore be
desirable to develop a less complex and/or more efficient GSG
system, such that the cost of installation and/or the payback
period can be reduced.
BRIEF DESCRIPTION
[0002] In a first aspect, a device, such as an absorption chiller
sub-system, is provided. The absorption chiller sub-system can
include an evaporator and an absorber. The evaporator can be
configured to receive a liquid first working fluid and to produce
first working fluid vapor. The absorber can be configured to
receive and combine first working fluid vapor and a second working
fluid, for example, so as to release thermal energy.
[0003] A divider having opposing first and second sides in
respective fluid communication with the evaporator and the absorber
can also be included. For example, the evaporator and the absorber
can be respectively coupled to the first side and second sides of
the divider. The divider can be configured to allow first working
fluid vapor to pass therethrough between the first and second sides
and to inhibit movement of liquid first working fluid therethrough
between the first and second sides. For example, the divider may
define holes therethrough having diameters, say, less than or equal
to about 100 nm. In some embodiments, the divider can include a
membrane.
[0004] The absorber can be configured to combine at least some
first working fluid vapor passing through the divider and a second
working fluid so as to cause at least some first working fluid
vapor passing through the divider to become liquid. In some cases,
the absorber can be configured to receive the second working fluid
such that an equilibrium second partial pressure of first working
fluid vapor at the second side of the divider is less than a first
partial pressure of first working fluid vapor at the first side.
For example, the evaporator can be configured to receive liquid
NH.sub.3 as the liquid first working fluid, and the absorber is
configured to receive water or a mixture of water and NH.sub.3 as
the second working fluid.
[0005] In some embodiments, the evaporator can be configured such
that a total pressure therein is at least twice a partial pressure
of first working fluid vapor at the first side of the divider. The
absorber can be configured such that a total pressure therein is at
least twice a partial pressure of first working fluid vapor at the
second side of the divider. Each of the evaporator and the absorber
may be configured such that a respective total pressure therein is
greater than or equal to about atmospheric pressure.
[0006] The evaporator can be configured to receive liquid water and
to produce water vapor, and the absorber can be configured to
combine water vapor passing through the divider and a relatively
concentrated solution containing lithium bromide so to produce a
relatively diluted solution containing lithium bromide. The divider
can be formed at least partially of substantially hydrophobic
material (e.g., polytetrafluoroethylene, polypropylene, or
polyvinylidene fluoride) such that holes defined by the divider are
defined by the substantially hydrophobic material.
[0007] A generator may be included and configured to receive the
relatively diluted solution containing lithium bromide from the
absorber and to produce separate outputs of water vapor and the
relatively concentrated solution containing lithium bromide. A
condenser can also be included and configured to receive water
vapor from the generator and to provide liquid water to the
evaporator. The generator and condenser can be in fluid
communication with opposing sides of a second divider that is
configured to allow water vapor to pass therethrough and to inhibit
movement of liquid water therethrough, such that water vapor from
the generator can pass through to the condenser while liquid water
in the generator is substantially prevented from reaching the
condenser.
[0008] A geothermal well, a heat exchanger, and a water heater can
also be included. Each of the condenser, absorber, and evaporator
can be configured to selectively thermally communicate with the
geothermal well and the heat exchanger. In some embodiments,
thermal energy may be transferred from the absorber and the
condenser into a heated fluid stream, and thermal energy may be
transferred from a cooled fluid stream into the liquid first
working fluid, with the heated fluid stream being in selective
fluid communication with each of the water heater, the heat
exchanger, and the geothermal well, and the cooled fluid stream
being in selective fluid communication with each of the heat
exchanger and the geothermal well. The geothermal well and the heat
exchanger may also be configured to selectively exchange thermal
energy directly therebetween and to avoid exchanging thermal energy
with each of the generator, condenser, evaporator, and
absorber.
[0009] In another aspect, a method is provided, which includes
providing a device including an evaporator, an absorber, and a
divider having opposing first and second sides in fluid
communication with the evaporator and the absorber, respectively.
The divider can be configured to allow first working fluid vapor to
pass therethrough between the first and second sides and to inhibit
movement of liquid first working fluid therethrough between the
first and second sides. Liquid first working fluid (e.g., liquid
water) can be provided to the evaporator so as to produce first
working fluid vapor (e.g., water vapor) that contacts the first
side of the divider. First working fluid vapor passing through the
divider from the first side to the second side and a second working
fluid (e.g., a relatively concentrated solution containing lithium
bromide) can be received at the absorber, and at least some first
working fluid vapor passing through the divider can be combined in
the absorber with the second working fluid, for example, so as to
cause at least some of the first working fluid vapor passing
through the divider to become liquid and/or release thermal energy
(say, producing a relatively diluted solution containing lithium
bromide).
[0010] In some embodiments, thermal energy can be supplied to the
relatively diluted solution containing lithium bromide so as to
cause water to evaporate out and thereby produce the relatively
concentrated solution containing lithium bromide. Further, thermal
energy can be removed from the water vapor produced from the
relatively diluted solution containing lithium bromide so as to
produce liquid water to be provided to the evaporator.
[0011] In some embodiments, the thermal energy removed from the
water vapor produced from the relatively diluted solution
containing lithium bromide can be selectively transferred to a
heated fluid stream along with thermal energy from the absorber.
Thermal energy can also be selectively transferred from a cooled
fluid stream to the liquid water circulated to the evaporator.
Further, thermal energy can be selectively transferred between the
heated fluid stream and at least one of a heat exchanger or a
geothermal well, and also between the cooled fluid stream and at
least one of the heat exchanger and the geothermal well. In some
cases, a target temperature can be selected, and, when the target
temperature is higher than a ground temperature of the geothermal
well, a geothermal fluid stream can be circulated between the
geothermal well and the heat exchanger without receiving the
thermal energy removed from the water vapor produced from the
relatively diluted solution containing lithium bromide and without
exchanging thermal energy with the absorber.
DRAWINGS
[0012] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0013] FIG. 1 is a schematic view of an absorption chiller
sub-system configured in accordance with an example embodiment;
[0014] FIG. 2 is a cross sectional view of the absorption chiller
sub-system of FIG. 1;
[0015] FIG. 3 is a perspective exploded view of the absorption
chiller sub-system of FIG. 1;
[0016] FIG. 4 is a magnified view of the area labeled 4 in FIG.
2;
[0017] FIG. 5 is a magnified view of the area labeled 5 in FIG.
4;
[0018] FIG. 6 is a schematic side view of another example
embodiment of the absorption chiller sub-system of FIG. 1;
[0019] FIG. 7 is a magnified view of the area labeled 7 in FIG.
6;
[0020] FIG. 8 is a schematic view of the absorption chiller
sub-system of FIG. 1 in thermal communication with a source and a
sink of thermal energy;
[0021] FIG. 9 is a schematic view of an absorption refrigeration
system configured in accordance with an example embodiment;
[0022] FIG. 10 is a schematic view of a heating and cooling system
configured in accordance with an example embodiment;
[0023] FIG. 11 is a schematic view of an absorption refrigeration
system configured in accordance with another example
embodiment;
[0024] FIG. 12 is a schematic cross-sectional view of an absorption
chiller system configured in accordance with another example
embodiment;
[0025] FIG. 13 is a magnified view of the area labeled 13 in FIG.
12;
[0026] FIG. 14 is a schematic cross-sectional view of an absorption
chiller system configured in accordance with yet another example
embodiment;
[0027] FIG. 15 is a magnified view of the area labeled 15 in FIG.
14;
[0028] FIG. 16 is a schematic cross-sectional view of an absorption
chiller system configured in accordance with still another example
embodiment; and
[0029] FIG. 17 is a magnified view of the area labeled 17 in FIG.
16.
DETAILED DESCRIPTION
[0030] Example embodiments of the present invention are described
below in detail with reference to the accompanying drawings, where
the same reference numerals denote the same parts throughout the
drawings. Some of these embodiments may address the above and other
needs.
[0031] Referring to FIGS. 1-4, therein is shown a device, such as
an absorption chiller sub-system 100, configured in accordance with
an example embodiment. The absorption chiller sub-system 100 can
include an evaporator 102 and an absorber 104. A divider, such as a
membrane 106, can be disposed between the evaporator 102 and the
absorber 104. The membrane 106 can have opposing first and second
sides 108, 110, with the evaporator 102 being in fluid
communication with the first side and the absorber 104 being in
fluid communication with the second side. For example, in one
embodiment, the evaporator 102 can be coupled to the first side 108
and the absorber 104 can be coupled to the second side 110. In
other embodiments, the evaporator 102 and absorber 104 may not be
directly coupled to the first and second sides 108, 110,
respectively, but may still be configured to allow fluid to pass
thereto, for example, through an intermediate conduit.
[0032] The evaporator 102 can be configured to receive a liquid
first working fluid 112a and to produce first working fluid vapor
112b. For example, in one embodiment, the first working fluid 112
may be water, and the evaporator 102 may receive liquid water (for
example, through a liquid inlet port 114) and may produce water
vapor. Other candidate first working fluids are discussed below.
Liquid first working fluid 112a may circulate through the
evaporator 102, such that unevaporated portions are outputted from
the evaporator, say, at a liquid outlet port 116.
[0033] The absorber 104 can be configured to receive first working
fluid vapor 112b and to combine at least some of that first working
fluid vapor with a second working fluid 118. The second working
fluid 118 may circulate through the absorber 104, such that the
second working fluid is received, say, at an inlet port 120,
travels through the absorber, and exits at an outlet port 122.
Given that the second working fluid 118 enters the absorber 104 and
then is combined therein with first working fluid vapor 112b, the
second working fluid 118a entering the absorber has a relatively
lesser concentration therein of first working fluid than does the
second working fluid 118b inside and exiting the absorber. The
second working fluid 118a entering the absorber 104 at the inlet
port 120 is therefore referred to herein as "relatively
concentrated second working fluid," and the second working fluid
118b inside the absorber and exiting at the outlet port 122 is
referred to herein as "relatively diluted second working
fluid."
[0034] The first and second working fluids 112, 118 may be chosen
such that the act of combining first working fluid vapor 112b and
the second working fluid causes a release of thermal energy. For
example, the absorber 104 can be configured to combine first
working fluid vapor 112b and the second working fluid 118 so as to
cause at least some first working fluid vapor 112b to become
liquid, thereby causing a release of the latent heat of evaporation
associated with the vapor. In some embodiments, the second working
fluid 118 may include at least one component (an "absorbent") that
tends to form a liquid solution with the first working fluid vapor
112b, such that when the first working fluid vapor comes into
contact with the second working fluid, the first working fluid
vapor tends to transform into a liquid component of the liquid
solution with the absorbent, thereby causing a release of the heat
of absorption. In other embodiments, a chemical reaction may occur
between the first working fluid vapor 112b and a component of the
second working fluid 118, which reaction may be exothermic and/or
may induce a transformation of the first working fluid vapor 112b
to a liquid, thereby releasing heat of reaction and/or latent
heat.
[0035] Referring to FIGS. 1-7, as mentioned, the membrane 106 can
be disposed between, and in fluid communication with, the
evaporator 102 and the absorber 104. The first side 108 of the
membrane 106 may therefore be contacted by liquid first working
fluid 112a and first working fluid vapor 112b, and the second side
110 may be contacted by the second working fluid 118 and first
working fluid vapor that may be disposed in the absorber 104. In
some embodiments, virtually all of the volume within the evaporator
102 may be occupied by liquid first working fluid 112a and/or all
of the volume within the absorber 104 may be occupied by the second
working fluid 118 (as depicted in FIGS. 4 and 5). In such cases,
first working fluid vapor 112b in the evaporator 102 would be found
mainly at the first side 108 of the membrane 106, and first working
fluid vapor 112b in the absorber 104 would be found mainly at the
second side 110. In other embodiments (depicted by FIGS. 6 and 7),
the volumes of the evaporator 102 and absorber 104 may be only
partially occupied by liquid first working fluid 112a and (liquid)
second working fluid 118, such that first working fluid vapor 112b
may be found not only at the first and second sides 108, 110, but
throughout the volumes of the evaporator and absorber that are not
otherwise occupied by liquids.
[0036] The membrane 106 may be configured to allow first working
fluid vapor 112b to pass therethrough between the first and second
sides 108, 110 and to inhibit movement of liquid first working
fluid 112a, and the second working fluid 118, therethrough between
said first and second sides. For example, the membrane 106 may
define holes 124 therethrough. The holes 124 may be sized in
accordance with the properties of the first and second working
fluids 112, 118 and those of the material making up the membrane
106 in order to assure that the interfacial energies of liquid
first and second working fluids and the membrane are such that the
liquid first and second working fluids are energetically prevented
from assuming a configuration necessary to pass through the holes
in the membrane. Further details regarding the sizing of the holes
124, as well as the selection of the working fluids 112, 118 and
material for the membrane 106, are provided below. A general
discussion of the use of porous membranes in fluid separation
applications is provided in Marcel Mulder, Basic Principles of
Membrane Technology (Kluwer Academic Publishers, 1996), which is
incorporated herein by reference in its entirety, and also in K. W.
Lawson and D. R. Lloyd, "Review Membrane Distillation," Journal of
Membrane Science, 124 (1997), pp. 1-25, which is also incorporated
herein by reference in its entirety.
[0037] The second working fluid 118 can be chosen such that, when
received at the absorber 104 (under appropriate conditions), an
equilibrium partial pressure P2 of first working fluid vapor 112b
at the second side 110 (and possibly throughout the absorber) is
less than a partial pressure P1 of first working fluid vapor at the
first side 108 (and possibly throughout the evaporator 102). For
example, the first and second working fluids 112, 118 can be chosen
such that the second working fluid includes as a component thereof
a liquid that has a strong affinity for the first working fluid. In
such a case, the equilibrium partial pressure P2 of the first
working fluid vapor 112b in the vicinity of the second working
fluid 118 will tend to be low relative, say, to the partial
pressure P1 expected in the vicinity of liquid first working fluid
112a. Examples of pairs of first and second working fluids 112, 118
that may be utilized in conjunction with embodiments of the above
described absorption chiller sub-system 100 include, but are not
limited to, water and lithium bromide; NH.sub.3 and water (or a
mixture of water and NH.sub.3); water and LiClO.sub.3; water and
CaCl.sub.2, water and ZnCl.sub.2; water and HnBr; water and
H.sub.2SO.sub.4; and SO.sub.2 and organic solvents.
[0038] The difference in partial pressures P1 and P2 of first
working fluid vapor 112b across the membrane 106 results in a
driving force for diffusion of first working fluid vapor from the
first side 108 to the second side 110. Once first working fluid
vapor 112b reaches the second side 110, it can be combined in the
absorber 104 with the second working fluid 118, with this
combination being made more likely by the proper choice of a second
working fluid having an affinity for first working fluid. Mass
(i.e., first working fluid 112) will therefore be transferred from
the evaporator 102 to the absorber 104. In addition, as mass is
transferred from the evaporator 102 to the absorber 104, the
balance in the evaporator between liquid first working fluid 112a
and first working fluid vapor 112b will be disrupted, driving
further evaporation of liquid first working fluid. It is noted that
continued evaporation of liquid first working fluid 112a in the
evaporator 102 does not necessarily require the input of energy,
but instead may proceed simply due to the affinity of the second
working fluid 118 for first working fluid.
[0039] As liquid first working fluid 112a evaporates in the
evaporator 102 to form first working fluid vapor 112b, thermal
energy is absorbed from the liquid first working fluid and used to
overcome the latent heat of evaporation of the first working fluid
112. As the first working fluid vapor 112b moves through the
membrane 106 and is combined in the absorber 104 with the second
working fluid 118 to form a liquid, thermal energy in the form of
latent heat of evaporation and/or absorption can be released (as
well as heat produced by any exothermic chemical reactions that may
take place between the first and second working fluids). The
overall result is a thermal energy transfer, associated with the
mass transfer, from the liquid first working fluid 112a in the
evaporator 102 to the second working fluid 118 in the absorber 104.
The membrane 106 can be configured such that the surface area
presented to the first working fluid 112 at the first side 108 and
to the second working fluid 118 at the second side 110 is
sufficient to facilitate a desired level of thermal energy
transfer.
[0040] With the evaporator 102 and the absorber 104 separated by
the membrane 106 as discussed above, it may not be required that
the total pressure within either of the evaporator or the absorber
is approximately the same as the respective partial pressure
therein of first working fluid vapor 112b, as may have been the
case for previous absorption chiller sub-systems. Rather, the
evaporator 102 may be configured such that the total pressure
therein is at least twice the partial pressure P1 of first working
fluid vapor 112b. Further, the absorber 104 may be configured such
that the total pressure therein is at least twice the partial
pressure P2 of first working fluid vapor 112b. As such, embodiments
of the absorption chiller sub-system 100 may have a total size and
weight that is significantly reduced with respect to previous
absorption chiller sub-systems.
[0041] For the first working fluid vapor 112b to be driven from one
side of the membrane 106 to the other, particular temperatures and
pressures are needed. As mentioned above, the evaporation of liquid
first working fluid 112a in the evaporator 102, the diffusion of
first working fluid vapor 112b from the first side 108 of the
membrane 106 to the second side 110, and the absorption of first
working fluid vapor (or other energy-releasing event) in the
absorber 104 can proceed spontaneously, acting to transfer thermal
energy from the evaporator to the absorber. However, as thermal
energy is transferred, the temperature of the liquid first working
fluid 112a (in the absence of any other energy transfers) will
drop, thereby reducing (and eventually eliminating) the tendency
for further evaporation. At the same time, the temperature of the
second working fluid 118 (again, in the absence of any other energy
transfers) will rise, thereby decreasing (and eventually
eliminating) the tendency of first working fluid vapor 112b therein
to be absorbed. It is noted that, in some embodiments, the membrane
106 may include a thermally insulating material, thereby preventing
the transfer of heat therethrough from the absorber 104 to the
evaporator 102.
[0042] Referring to FIG. 8, in order to allow the transfer of
thermal energy from the evaporator 102 to the absorber 104 to
continue, the evaporator can be brought into thermal contact with a
thermal energy source 126, while the absorber can be brought into
thermal contact with a thermal energy sink 128. For example, a
cooled fluid stream 130 (e.g., air or water) can be circulated
between the thermal energy source 126 and the evaporator 102 by a
pump 132, and a heated fluid stream 134 (e.g., air or water) can be
circulated between the absorber 104 and the thermal energy sink 128
by a pump 136. The absorption chiller sub-system 100 can therefore
be used to extract thermal energy from the thermal energy source
126 and to deposit thermal energy at a thermal energy sink 128. In
some embodiments, the temperature T.sub.source at the thermal
energy source 126 may be lower than the temperature T.sub.sink at
the thermal energy sink 128, in which case the absorption chiller
sub-system 100 operates as a heat pump. Any barriers separating the
first working fluid 112a in the evaporator 102 and the cooled fluid
stream 130 (e.g., an outer wall defining the evaporator), and/or
any barriers separating the second working fluid 118a in the
absorber 104 and the heated fluid stream 134 (e.g., an outer wall
defining the absorber), can be configured to have a relatively low
thermal resistance, thereby facilitating thermal energy transfer
thereacross.
[0043] Referring to FIG. 9, therein is shown an absorption
refrigeration system 140 (also referred to as an absorption chiller
system) that incorporates the absorption chiller sub-system 100. A
generator 142 may receive the relatively diluted second working
fluid 118b that is outputted at the outlet port 122 of the absorber
104. As mentioned above, the second working fluid 118b that is
outputted from the absorber 104 has been combined therein with
first working fluid vapor 112b passing through the membrane 106. A
pump 144 can be used to urge the relatively diluted second working
fluid 118b towards the generator 142. The generator 142 can be
configured to receive the relatively diluted second working fluid
118b and to produce separate outputs of first working fluid vapor
112b and a relatively concentrated second working fluid 118a. For
example, thermal energy 146 can be added at the generator 142 in
order to raise the temperature of the relatively diluted second
working fluid 118b, thereby driving some of the first working fluid
dissolved therein out of the solution as first working fluid vapor
112b. The remaining second working fluid, now being relatively
concentrated second working fluid 118a, can be directed back to the
inlet port 120 of the absorber 104.
[0044] The first working fluid vapor 112b outputted from the
generator 142 can be directed to a condenser 148. The condenser 148
can receive the first working fluid vapor 112b and to provide
liquid first working fluid 112a to the evaporator 102. For example,
thermal energy 150 can be removed at the condenser 148, say,
through the use of a heat exchanger, in order to cause the first
working fluid vapor 112b to condense.
[0045] Overall, the evaporator 102, absorber 104, generator 142,
and condenser 148 may operate so as to form a continuous cycle in
which the second working fluid 118 is combined with first working
fluid 112 at the absorber and separated from first working fluid at
the generator, and first working fluid is converted from gas to
liquid at the condenser and from liquid to gas at the evaporator.
The system 140 acts to affect the transfer of thermal energy from a
source 126 to a sink 128. The only input of energy that may be
required to sustain the operation of the system 140 is the thermal
energy 146 that is directed to the generator 142 (and a small
amount of energy required to circulate the second working fluid
118, for example, through the operation of the pump 144), which
thermal energy may be supplied by, for example, the exhaust of an
internal combustion engine, engine fluid such as water/glycol or
oil, a burner, a solar collector, and/or the exhaust of a gas
turbine.
[0046] Referring to FIG. 10, therein is shown a heating and cooling
system 260 configured in accordance with an example embodiment. The
heating and cooling system 260 can include an absorption
refrigeration system 240 that incorporates an absorption chiller
sub-system 200 as described above with an evaporator 202 and an
absorber 204 separated by a membrane 206. The absorption chiller
sub-system 200 can employ water as the first working fluid 212,
such that the evaporator 202 is configured to receive liquid water
212a and to produce water vapor 212b.
[0047] The membrane 206 can define holes 224 that extend between
the evaporator 202 and the absorber 204. The membrane 206, or at
least the portions through which the holes 224 are defined, may be
formed of substantially hydrophobic material (e.g.,
polytetrafluoroethylene, polypropylene, and/or polyvinylidene
fluoride). By forming the holes 224 with a maximum diameter of
about 100 nm from a substantially hydrophobic material, the
movement of liquid water 212a through the membrane 206 is
substantially prevented, due to the surface energy effects
discussed above, while water vapor 212b is permitted to pass
through the holes between the evaporator 202 and absorber 204. As
mentioned earlier, in some embodiments, the membrane 206 may be
formed of thermally insulating material, with examples being the
hydrophobic materials listed above.
[0048] The absorption chiller sub-system 200 can also employ a
solution of lithium bromide and water 218 as the second working
fluid. The absorber 204 can be configured to combine water vapor
212b passing through the membrane 206 with the lithium
bromide-water solution 218a entering at an inlet port 220, thereby
forming in the absorber a lithium bromide-water solution 218b that
is relatively diluted with respect to lithium bromide content (the
solution previously being relatively concentrated with respect to
lithium bromide content prior to being combined with water vapor
passing through the membrane 206). Lithium bromide tends to have a
strong affinity for water, such that the partial pressure of water
vapor in the vicinity of lithium bromide tends to be relatively low
and the diffusion of water vapor through the membrane 206 is
facilitated.
[0049] As mentioned above, the use of a membrane 206 between the
evaporator 202 and absorber 204 may alleviate the need to maintain
the total pressure in either of the evaporator or the absorber at a
level that is about equal to the partial pressure of water vapor in
either one. Specifically, each of the evaporator 202 and the
absorber 204 may be configured such that a respective total
pressure therein is greater than or equal to about atmospheric
pressure. This may reduce the size, cost, and/or complexity of the
evaporator 202 and absorber 204. In other embodiments either the
evaporator 202 or the absorber 204 may be configured to operate
either above or below atmospheric pressure.
[0050] The absorption refrigeration system 240 can also include a
generator 242, which can receive the relatively diluted lithium
bromide-water solution 218b from the absorber 204 (e.g., the
relatively diluted lithium bromide-water solution exiting the
absorber at the outlet port 222) and thermal energy 246 from an
external source (not shown) to heat the diluted lithium
bromide-water solution so as to produce separate outputs of water
vapor 212b and the relatively concentrated containing lithium
bromide-water solution 218a that is ultimately received at the
inlet port 220. The lithium bromide-water solution 218 can be
circulated between the absorber 204 and the generator 242, say,
through the use of a pump 244.
[0051] As the absorption refrigeration system 240 operates, thermal
energy can be transferred from the evaporator 202 to the absorber
204. The thermal energy deposited at the absorber 204 can then be
rejected, say, to the ambient environment or some other energy
sink. A cooled water stream 230 can be disposed in thermal contact
with the evaporator 202, and thermal energy can be transferred from
the cooled water stream to the evaporator (e.g., to the water 212a
therein), thereby affecting (in the absence of other thermal
transfers) a temperature decrease in the cooled water stream.
[0052] The water vapor 212b outputted by the generator 242 can be
directed to a condenser 248, at which thermal energy can be removed
from the water vapor in order to produce liquid water 212a. The
liquid water 212b can then be directed to the evaporator 202 to
repeat the cycle. A heated water stream 262 can be disposed in
thermal contact with the condenser 248 such that the thermal energy
extracted from the water vapor 212b is transferred (at least in
part) to the heated water stream, thereby affecting (in the absence
of other thermal transfers) a temperature increase in the heated
water stream.
[0053] The heated water stream 262 can be circulated to each of a
geothermal well 264, a water heater 266, and a heat exchanger 268
(the last of which may be used, for example, as a space
heater/cooler) via manifolds 270. Thermal energy in the heated
water stream 262 (received, for example, at the condenser 248) can
then used to produce heat and hot water for residential or
commercial use via the heat exchanger 268 and water heater 266,
respectively, and/or can be rejected at the geothermal well 264.
The heated water stream 262 can be connected to the geothermal well
264 and the heat exchanger 268 with valves 272 that allow the
heated water stream to be selectively directed to or away from each
of the geothermal well and the heat exchanger. In this way, heat
can be provided via the heat exchanger only when desired (e.g., in
the winter). In some embodiments, the heated water stream 262 may
also be disposed in thermal communication with the absorber 204,
such that thermal energy rejected at the absorber may be used to
heat the heated water stream.
[0054] The cooled water stream 230 can be circulated to each of the
geothermal well 264 and a heat exchanger 268 (the last of which may
be used, for example, as a space heater/cooler) via manifolds 274.
Thermal energy can then be transferred to the cooled water stream
230 at the heat exchanger 268 in order to provide ambient cooling
or at the geothermal well 264 (with the thermal energy ultimately
being rejected, for example, at the evaporator 202). The cooled
water stream 230 can be connected to the geothermal well 264 and
the heat exchanger 268 with valves 272 that allow the cooled water
stream to be selectively directed to or away from each of the
geothermal well and the heat exchanger. In this way, cooling can be
provided via the heat exchanger only when desired (e.g., in the
summer).
[0055] Valves 276 may be included that function so as to
selectively create a geothermal fluid circulation loop 278 that
allows fluid (a "geothermal fluid stream") to circulate directly
between the geothermal well 264 and the heat exchanger 268, this
loop being otherwise isolated from the absorption refrigeration
system 240. When the valves 276 are so positioned to isolate the
fluid circulation loop 278 from the absorption refrigeration system
240, the geothermal well 264 and heat exchanger 268 may exchange
thermal energy directly therebetween (via the geothermal fluid
stream in the geothermal fluid circulation loop) without exchanging
thermal energy with any of the generator 242, condenser 248,
evaporator 202, and/or absorber 204.
[0056] The valves 276 may allow the heating and cooling system 260
to be operated more efficiently, under certain conditions, by
foregoing the use of the absorption refrigeration system 240, the
use of which requires some energy input at the generator 242. For
example, considering the use of the heat exchanger 268 as a
residential air conditioning unit for cooling a home, during summer
months, the temperature of the ground surrounding the geothermal
well 264 may be lower than a desired air temperature (a "target"
temperature) for the home. In that case, the valves 276 can be
adjusted to cause the geothermal fluid stream to circulate (say,
with the help of a pump 279) directly between the geothermal well
264 and the heat exchanger 268, without interacting with the
absorption refrigeration system 240. At these times, operation of
the absorption refrigeration system 240 can be ceased entirely,
avoiding the expenditure of energy otherwise required to operate
that system. The heating and cooling system 260 can be configured
to automatically switch between this "direct geothermal mode" of
operation and the absorption refrigeration mode of operation in
response to the ground temperature of the geothermal well 264 and a
user-selected target temperature.
[0057] Referring to FIG. 11, therein is shown an absorption
refrigeration system 340 configured in accordance with another
example embodiment. As with the embodiment depicted in FIG. 9 and
described above, the absorption refrigeration system 340 includes
an absorption chiller sub-system 300. The absorption chiller
sub-system 300 has an evaporator 302 and an absorber 304 separated
by a first divider, such as a first membrane 306a, that is
configured, for selected working fluids (including a first working
fluid), to allow vapor to pass therethrough and to substantially
prevent the passage of liquid. Liquid first working fluid 312a can
be received by the evaporator 302 so as to produce first working
fluid vapor 312b that passes through the first membrane 306a and to
the absorber 304, where it is combined with relatively concentrated
second working fluid 318a in order to produce relatively diluted
second working fluid 318b. As mentioned earlier, this process can
result in the transfer of thermal energy 380 into the evaporator
302 and across the first membrane 306a and into the absorber 304,
with thermal energy 382 ultimately being rejected at the
absorber.
[0058] The absorption refrigeration system 340 can also include a
generator 342 and a condenser 348 each in fluid communication with
opposing sides of a second membrane 306b. The second membrane 306b,
like the first membrane 306a, can be configured to allow first
working fluid vapor to pass therethrough and to inhibit movement of
liquid first working fluid therethrough. The generator 342 can
receive the relatively diluted second working fluid 318b being
outputted from the absorber 304. Thermal energy 346 can be provided
to the relatively diluted second working fluid 318b so as to cause
first working fluid vapor 312b to be released from the second
working fluid, thereby producing relatively concentrated second
working fluid 318a that can be directed to the absorber 304. The
first working fluid vapor 312b released from the second working
fluid 318 can then pass through the second membrane 306b to the
condenser 348, where thermal energy 350 can be removed to transform
the vapor to liquid first working fluid 312a.
[0059] Referring to FIGS. 12 and 13, therein is shown an absorption
chiller sub-system 400 configured in accordance with another
example embodiment. The absorption chiller sub-system 400 can
include an evaporator 402 and an absorber 404. A membrane 406 can
be disposed between the evaporator 402 and the absorber 404. The
membrane 406 can have opposing first and second sides 408, 410, and
second working fluid 418 in the absorber 404 can be in direct
contact with the second side. A barrier 490 can be included between
the evaporator 402 and the membrane 406, being separated from the
membrane by spacers 492. The barrier 490 can be configured such
that liquid first working fluid 412a in the evaporator 402 is
substantially prevented from contacting the first side 408 of the
membrane, while first working fluid vapor 412b is allowed to pass
through the barrier to the membrane and, ultimately, the absorber
404. The barrier 490 therefore results in the establishment of a
vapor gap 494 between liquid first working fluid 412a in the
evaporator 402 and the membrane 406.
[0060] The barrier 490 can be a relatively simple structure, such
as a mesh, that is relatively permeable to liquids. Penetration of
liquid first working fluid 412a from the evaporator 402 through the
barrier 490 can be substantially prevented by configuring the
absorption chiller sub-system 400 such that the liquid first
working fluid entering the evaporator at the inlet port 414 has a
relatively low hydrostatic pressure and a velocity V directed
substantially parallel to the barrier. In this way, the liquid
first working fluid 412a in the evaporator 402 would be expected to
have a small (nearly zero) velocity component directed toward the
barrier 490.
[0061] The vapor gap 494 may affect a decrease in the rate at which
thermal energy is transmitted from the (potentially hotter)
absorber 404 to the (potentially colder) evaporator 402. Conduction
across the vapor gap 494 will be substantially limited to the
energy transferred between colliding gaseous molecules, which
process is expected to be substantially less efficient than
conduction through a solid body. The vapor gap 494 may also result
in a reduction in the mass transfer rate between the evaporator 402
and the absorber 404, causing a corresponding loss in thermal
transfer efficiency from the evaporator to the absorber.
[0062] Referring to FIGS. 14 and 15, in another embodiment, a vapor
gap can be established on the absorber side of the membrane rather
than on the evaporator side, as in the previous embodiment. That
is, an absorption chiller sub-system 500 can include a membrane 506
can have opposing first and second sides 508, 510, with liquid
first working fluid 512a in the evaporator 502 being in direct
contact with the first side. A barrier 590 can be included between
the absorber 504 and the membrane 506, being separated from the
membrane by spacers 592. The barrier 590 can be configured such
that second working fluid 518 in the absorber is substantially
prevented from passing through the barrier, while first working
fluid vapor 412b is allowed to pass through the barrier to the
absorber 404. The barrier 590 therefore results in the
establishment of a vapor gap 594 between the membrane 506 and
second working fluid 518 in the absorber 504.
[0063] As mentioned above, in order to assure that the liquid does
not penetrate the barrier 490, 590, the hydrostatic pressure of the
fluid contacting the barrier should be relatively small. Referring
to FIGS. 16 and 17, in another embodiment, an absorption chiller
sub-system 600 can include an evaporator 602 and an absorber 604
separated by a pair of membranes 606a, 606b. The membranes 606a,
606b can be configured as discussed earlier so as to allow passage
therethrough of first working fluid vapor 612b but not liquid first
or second working fluids 612a, 618. The pair of membranes 606a,
606b (which may be integrated into a unitary structure) can be
separated by a vapor gap 694, thereby limiting thermal conduction
across the membranes from the absorber 604 to the evaporator 602.
In some embodiments, the hydrostatic pressure of either of liquid
first working fluid 612a in the evaporator 602 or second working
fluid 618 in the absorber 604 can be relatively high, which aspect
may simplify the overall design of the absorption chiller
sub-system 600.
[0064] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. For example, while
absorption refrigeration systems have been described that
incorporate an evaporator and absorber coupled across a porous
membrane and utilized in conjunction with either a conventional
generator and condenser or a generator-condenser combination in
which the generator and condenser are coupled across a porous
membrane, it is also possible to utilize a
generator-membrane-condenser combination with a conventional
evaporator and absorber. Finally, while single stage or "single
effect" absorption refrigeration systems have been described above,
the concepts disclosed herein are also amenable to use in "multiple
effect" or cascaded systems, in which the thermal energy that is
outputted from one thermal cycling system (say, at the absorber
and/or condenser) acts as the driving force for another thermal
cycle (say, being the input to the generator). It is, therefore, to
be understood that the appended claims are intended to cover all
such modifications and changes as fall within the true spirit of
the invention.
* * * * *