U.S. patent application number 11/461271 was filed with the patent office on 2008-01-31 for adsorption heat exchanger.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to ALEXANDER M. BERSHITSKY, STEPHEN R. DUNNE.
Application Number | 20080023181 11/461271 |
Document ID | / |
Family ID | 38984978 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023181 |
Kind Code |
A1 |
DUNNE; STEPHEN R. ; et
al. |
January 31, 2008 |
ADSORPTION HEAT EXCHANGER
Abstract
An adsorption heat exchanger may comprise a stack of alternating
adsorption layers and heat transfer layers. Separator plates may
separate the adsorption layers from the heat transfer layers. The
adsorption layer may include a first corrugated sheet positioned
between and brazed to the adsorption zone facing side of two
separator sheets. The first corrugated sheet and the exposed
portions of the adsorption zone facing side of the separator sheets
may be coated with an adsorptive material. The heat transfer layer
may include a second corrugated sheet positioned between and brazed
to the heat transfer zone facing side of two separator sheets. The
second corrugated sheet may be oriented about 90.degree. to the
first corrugated sheet.
Inventors: |
DUNNE; STEPHEN R.;
(ALGONQUIN, IL) ; BERSHITSKY; ALEXANDER M.;
(GLENVIEW, IL) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD, P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
MORRISTOWN
NJ
|
Family ID: |
38984978 |
Appl. No.: |
11/461271 |
Filed: |
July 31, 2006 |
Current U.S.
Class: |
165/133 ; 62/271;
62/480 |
Current CPC
Class: |
F25B 35/04 20130101;
F25B 2500/01 20130101; F28D 9/0062 20130101; F28F 3/025
20130101 |
Class at
Publication: |
165/133 ; 62/480;
62/271 |
International
Class: |
F28F 13/18 20060101
F28F013/18; F25D 23/00 20060101 F25D023/00; F25B 17/08 20060101
F25B017/08 |
Claims
1. An apparatus comprising: at least one adsorption layer having an
adsorption zone corrugated sheet, at least a portion of said
adsorption zone corrugated sheet having an adsorptive material
coating; at least one heat transfer layer having a heat transfer
zone corrugated sheet, said heat transfer layer positioned parallel
to said adsorption layer; and a separator plate positioned between
and in contact with said adsorption zone corrugated sheet and said
heat transfer zone corrugated sheet.
2. The apparatus of claim 1, wherein said adsorption zone
corrugated sheet includes at least one adsorption zone fin, said
adsorption zone fin having an adsorption fin height of between
about 0.10 inches and about 0.5 inches.
3. The apparatus of claim 2, wherein said adsorption zone fin has
an adsorption fin thickness of between about 0.001 inches and about
0.01 inches.
4. The apparatus of claim 1, wherein said adsorption zone
corrugated sheet includes a plurality of adsorption zone fins, a
density of said adsorption zone fins is between about 7 fins/inch
and about 28 fins/inch.
5. The apparatus of claim 1, wherein said adsorption layer is
oriented in a direction 90.degree. of said heat transfer layer.
6. The apparatus of claim 1, wherein said adsorptive material
coating has an adsorptive coating thickness of between about 0.004
inches and about 0.040 inches.
7. The apparatus of claim 1, wherein said adsorption zone
corrugated sheet includes at least one adsorption zone contact
portion positioned parallel to and in contact with said separator
plate.
8. The apparatus of claim 1, wherein at least a portion of said
separator plate has an adsorptive material coating.
9. The apparatus of claim 1, wherein said separator plate has a
separator plate thickness between about 0.003 inches and about 0.1
inches.
10. The apparatus of claim 1, wherein said heat transfer zone
corrugated sheet includes at least one heat transfer zone fin, said
heat transfer zone fin having a heat transfer fin height of between
about 0.04 inches and about 0.2 inches.
11. An apparatus comprising: an adsorption zone corrugated sheet
having a plurality of adsorption zone fins and a plurality of
adsorption zone contact portions; a heat transfer zone corrugated
sheet positioned parallel to and oriented 90.degree. of said
adsorption zone corrugated sheet; a separator sheet having an
adsorption zone facing side and a heat transfer zone facing side,
said separator sheet positioned between and in contact with said
adsorption zone corrugated sheet and said heat transfer corrugated
sheet; and an adsorptive material coating in contact with at least
one adsorption zone fin.
12. The apparatus of claim 11, wherein said adsorptive material
coating is in contact with at least a portion of said adsorption
zone facing side.
13. The apparatus of claim 11, wherein said adsorptive material
coating is in contact with at least one adsorption zone contact
portion.
14. The apparatus of claim 11, wherein said adsorptive material
coating comprises at least one of silica gel, aluminas, silicas,
zeolites, activated carbon, metal chlorides, metal hydrides,
supported Na.sub.2SO4, synthetic polymers, or mixtures thereof.
15. The apparatus of claim 11, wherein said heat transfer zone
corrugated sheet has a plurality of heat transfer zone fins, a
density of said heat transfer zone fins is between about 10
fins/inch and about 30 fins/inch.
16. The apparatus of claim 11, wherein said adsorptive material
coating has an adsorptive coating thickness of less than about 0.5
mm.
17. An apparatus comprising: a plurality of adsorption layers; a
plurality of heat transfer layers, said plurality of adsorption
layers and said plurality of heat transfer layers positioned such
that a stacked arrangement of alternating adsorption layers and
heat transfer layers is formed, said plurality of adsorption layers
and said plurality of heat transfer layers forming at least one
adsorption layer/heat transfer layer pair; and a separator plate
positioned between and in contact with said adsorption layer/heat
transfer layer pair.
18. The apparatus of claim 17, wherein at least one adsorption
layer includes two adsorption zone header bars positioned parallel
to an adsorption flow line of said adsorption layer and positioned
such that one adsorption zone header bar is at one side of said
adsorption layer and the other adsorption zone header bar is at the
opposing side of said adsorption layer.
19. The apparatus of claim 17, wherein at least one said adsorption
layer has an adsorptive coating thickness of between about 0.004
inches and about 0.04 inches.
20. The apparatus of claim 17, further comprising at least one side
plate positioned parallel to said plurality of adsorption layers
and positioned at a side of said stacked arrangement of alternating
adsorption layers and heat transfer layers.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to adsorbent coated
heat exchangers and, more particularly, to adsorption heat
exchangers as used in adsorption devices such as adsorbers and
adsorption heat pumps.
[0002] Heat exchangers can be used for transporting heat. The heat
exchanger can be operationally connected to a heat source and a
heat sink. In some systems, such as an air cycle pack of an
environmental control system, the heat exchanger can be connected
to the heat source via a heat transfer fluid loop and a flow of ram
air may serve as the heat sink. In some systems, such as vapor
cycle systems, both the heat source and the heat sink may be
connected to the heat exchanger via fluid loops.
[0003] A heat exchanger is conventionally used to transport heat
from one fluid to another. The adsorbent heat exchangers of the
present invention do not serve that general purpose. Instead the
present invention is an improvement in the field of adsorbers which
function efficiently to adsorb a working fluid when cooled and can
desorb that same working fluid efficiently when heated. Sensible
heat transfer from a heat transfer fluid takes place in an adsorber
heat exchanger and serves to efficiently change the temperature and
enthalpy, and working loading of the adsorbent material that coats
the adsorber heat exchanger.
[0004] A heat exchanger for use with two fluid loops is described
in U.S. Pat. No. 6,318,456. The disclosed heat exchanger is of the
cross current design and comprises a plurality of stacked plates
that form a first flow path and a second flow path. Heat transfer
occurs as fluid from one loop passes through the first flow path
and fluid from the other loop passes through the second flow path.
Generally, both fluid loops include a pump to pump the fluids
through the heat exchanger. Although such devices may be efficient
they utilize high quality shaft work as a high power input.
[0005] Heat exchangers that include an adsorptive material within
one flow path can provide a reduction in power input. An adsorption
heat exchanger is disclosed in U.S. Pat. No. 5,585,145. The
described adsorption heat exchanger comprises a tube and lamellas
(plates) design. The tube is positioned through holes in the
lamellas. The heat exchanger is designed such that one fluid (e.g.
a heat transfer fluid) can pass through the tube and a second fluid
(e.g. an adsorbate) can pass over the lamellas. After assembly the
lamellas and the outside surface of the tube (outside surface of
the heat transfer fluid flow path) are wash coated with an
adsorptive material. The adsorptive material desorbs the second
fluid when heated and adsorbs the second fluid when cooled.
Although the described adsorption heat exchanger can reduce power
input, the adsorptive material tends to build up at the tube-plate
interface during coating application. The uneven adsorptive coating
layer reduces efficiency. Additionally, a reduction in adsorption
heat exchanger dimensions is desired for some applications.
[0006] Adsorption heat exchangers having a more evenly applied
adsorptive material have been described. In U.S. Pat. No.
6,102,107, the plates are laminated with an adsorptive
material/fiber matrix paper prior to assembly of the tube-plate
heat exchanger. The described laminate paper design avoids the
tube-plate interface build up of the '145 patent. Although the
laminate paper can provide a more even layer of adsorptive
material, both heat and mass transfer are negatively affected by
the thickness of adsorptive material/fiber matrix paper.
[0007] As can be seen, there is a need for improved adsorption heat
exchangers. Adsorption heat exchangers having improved adsorption
coating thickness uniformity and increased adsorptive material
surface area are needed. Further, adsorption heat exchangers having
increased adsorption/desorption efficiency, higher heat transfer
efficiency and smaller size are needed.
SUMMARY OF THE INVENTION
[0008] In one aspect of the present invention, an apparatus
comprises at least one adsorption layer having an adsorption zone
corrugated sheet, at least a portion of the adsorption zone
corrugated sheet having an adsorptive material coating; at least
one heat transfer layer having a heat transfer zone corrugated
sheet, the heat transfer layer positioned parallel to the
adsorption layer; and a separator plate positioned between and in
contact with the adsorption zone corrugated sheet and the heat
transfer zone corrugated sheet.
[0009] In another aspect of the present invention, an apparatus
comprises an adsorption zone corrugated sheet having a plurality of
adsorption zone fins and a plurality of adsorption zone contact
portions; a heat transfer zone corrugated sheet positioned parallel
to and oriented 90.degree. of the adsorption zone corrugated sheet;
a separator sheet having an adsorption zone facing side and a heat
transfer zone facing side, the separator sheet positioned between
and in contact with the adsorption zone corrugated sheet and the
heat transfer corrugated sheet; and an adsorptive material coating
in contact with at least one adsorption zone fin.
[0010] In a further aspect of the present invention, an apparatus
comprises a plurality of adsorption layers; a plurality of heat
transfer layers, the plurality of adsorption layers and the
plurality of heat transfer layers positioned such that a stacked
arrangement of alternating adsorption layers and heat transfer
layers is formed, the plurality of adsorption layers and the
plurality of heat transfer layers forming at least one adsorption
layer/heat transfer layer pair; and a separator plate positioned
between and in contact with the adsorption layer/heat transfer
layer pair.
[0011] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following drawings, description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram of a sorptive cooling system according
to one embodiment of the present invention;
[0013] FIG. 2a is a perspective view of an adsorption heat
exchanger according to one embodiment of the present invention;
[0014] FIG. 2b is a close-up view of a portion of FIG. 2a;
[0015] FIG. 2c is a close-up view of another portion of FIG.
2a;
[0016] FIG. 3 is a perspective view of a portion of an adsorption
heat exchanger according to one embodiment of the present
invention;
[0017] FIG. 4 is a rotated view of FIG. 3;
[0018] FIG. 5 is a flow chart of a method of transferring heat
between a flow of adsorbate and a flow of heat transfer fluid
according to an embodiment of the present invention;
[0019] FIG. 6 is a plot of specific power as a function of cycle
time according to one embodiment of the present invention;
[0020] FIG. 7 is a table of design parameters for an adsorption
heat exchanger according to one embodiment of the present
invention;
[0021] FIG. 8 is a diagram of the geometry of the adsorption heat
exchanger of FIG. 7;
[0022] FIG. 9 is a table of sensitivity results on coating
thickness variations for an adsorption heat exchanger according to
one embodiment of the present invention; and
[0023] FIG. 10 is a table of design and performance parameters for
an adsorption heat exchanger according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The following detailed description is of the best currently
contemplated modes of carrying out the invention. The description
is not to be taken in a limiting sense, but is made merely for the
purpose of illustrating the general principles of the invention,
since the scope of the invention is best defined by the appended
claims.
[0025] Broadly, the present invention provides adsorption heat
exchangers for adsorption heat pumps and adsorption applications.
Embodiments of these exchangers are not in themselves intended to
promote heat transfer in a general sense, rather they are intended
to enhance the transport of sensible heat from a heat transfer
fluid into the adsorbent coating applied to the plurality of
adsorbent layers, these exchangers are thus efficient at adsorbing
and desorbing a working fluid such as water, and methods for using
the same. Embodiments of the present invention may find beneficial
use in industries such as the automotive, electricity generation
and aerospace industries. Embodiments of the present invention may
be useful in applications including adsorption refrigeration
systems, adsorption based air conditioning systems and
environmental control systems. Embodiments of the present invention
may be useful in any heat transport application where in it is
desired to efficiently heat or cool an adsorbent mass to promote
adsorption or desorption of a working fluid. Such adsorbent heat
exchangers may find use in applications including, but not limited
to, heat transport for automobile air conditioning systems.
[0026] In one embodiment, the present invention provides an
adsorption heat exchanger having a stack of alternating adsorption
layers and heat transfer layers. The adsorption heat exchanger can
comprise a stack of alternating corrugated sheets and separator
plates. The corrugated sheets can be oriented in an alternating
manner to provide an adsorption flow path in one direction and a
heat transfer flow path in another direction (about 90.degree. to
the adsorption flow path). The surfaces defining the adsorption
flow path can be coated with an adsorptive material. Unlike the
prior art tube-lamellas design, the present invention can comprise
a plate-corrugated sheet-plate design. For some embodiments, the
plate-corrugated sheet-plate design allows for enhanced primary
surface area and more efficient heat and mass transfer.
[0027] Unlike the prior art that includes adsorptive paper
laminates, the adsorptive material of the present invention can be
applied directly to a brazed heat exchanger assembly, reducing
production time. Additionally, the adsorptive material coating of
the present invention can provide a reduction in coating thickness
and attendant enhancement of both heat and mass transfer. Also
unlike the prior art paper laminate designs, the outside surface of
the heat transfer fluid flow path of the present invention can be
coated with adsorptive material, which may further increase
adsorptive material surface area.
[0028] Moreover, unlike the prior art wherein the heat transfer
fluid flow path comprises a tube, the heat transfer fluid flow path
of the present invention can include a corrugated sheet that
extends between and in contact with two separator plates. The
corrugated sheet can form a plurality of fins running parallel to
the flow of heat transfer fluid. The fins can increase heat
transfer to the adsorption layer without adversely affecting the
flow of the heat transfer fluid.
[0029] Embodiments of the present invention may include an
adsorption heat exchanger 40 designed to thermally connect with a
sorptive cooling system 41, as depicted in FIG. 1. The sorptive
cooling system 41 can include the adsorption heat exchanger 40, a
condenser 42 and an evaporator 43. The adsorption heat exchanger 40
can be operationally connected to a heat transfer fluid loop 44 and
an adsorption loop 45.
[0030] During operation of the sorptive cooling system 41, heat
from a flow of heat transfer fluid 69 (see FIG. 2a) flowing through
the heat transfer fluid loop 44 can heat exchange with an
adsorptive material coating 46 (see FIG. 3) and drive a flow of
adsorbate 60 (e.g. a refrigerant) (see FIG. 2a) flowing through the
adsorption loop 45. As the adsorptive material coating 46 is heated
the flow of adsorbate 60 is caused to move toward the condenser 42.
The flow of adsorbate 60 is desorbed from the adsorptive material
coating 46 within the adsorption heat exchanger 40, driving
adsorbate vapor to the condenser 42. In the condenser 42, the
adsorbate vapor can be cooled and condensed. The adsorbate
condensate can then pass to the evaporator 43 where the adsorbate
condensate can be heat exchanged with a process stream 47 or space
to be conditioned to revaporize the adsorbate condensate.
[0031] When further heating of the adsorptive material coating 46
no longer produces desorbed adsorbate from the adsorptive material
coating 46, the adsorption heat exchanger 40 can be isolated and
allowed to return to the adsorption conditions. When the adsorption
conditions are established in the adsorptive material coating 46,
the adsorbate vapor from the evaporator 43 can be reintroduced to
the adsorption heat exchanger 40 to complete the cycle. Generally
two or more adsorption heat exchangers 40 may be employed in a
typical cycle wherein one adsorption heat exchanger 40 is heated
during the desorption stroke and a second adsorption heat exchanger
40b is cooled during the adsorption stroke. The time for the
completion of a full cycle of adsorption and desorption is known as
the "cycle time."
[0032] The adsorption heat exchanger 40, according to an embodiment
of the present invention is shown in FIGS. 2a-c. The adsorption
heat exchanger 40 can comprise at least one adsorption layer 50, at
least one heat transfer layer 51 and a separator plate 52
positioned between and in contact with the adsorption layer 50 and
the heat transfer layer 51. The adsorption heat exchanger 40 can
comprise a plurality of adsorption layers 50 and a plurality of
heat transfer layers 51. The adsorption layers 50 and heat transfer
layers 51 may be positioned in a stacked arrangement of alternating
adsorption layers 50 and heat transfer layers 51. In other words,
one adsorption layer 50 may be positioned between two heat transfer
layers 51; and one heat transfer layer 51 may be positioned between
two adsorption layers 50. The adsorption heat exchanger 40 can
comprise a plurality of separator plates 52 positioned such that
one separator plate 52 is between and in contact with each
adsorption layer/heat transfer layer pair. In other words, the
separator plate 52 may be positioned between the adsorption layer
50 and the heat transfer layer 51. As defined herein, an adsorption
layer/heat transfer layer pair may comprise an adsorption layer 50
and a heat transfer layer 51 positioned adjacent to one
another.
[0033] The adsorption layer 50 may provide an adsorption flow
passage 53 through the adsorption heat exchanger 40. The adsorption
flow passage 53 may be in a direction parallel to an adsorption
flow line 54. The heat transfer layer 51 may define a heat transfer
flow passage 55 through the adsorption heat exchanger 40. The heat
transfer flow passage 55 may be in a direction parallel to a heat
transfer flow line 56. The adsorption flow line 54 may be about
90.degree. from the heat transfer flow line 56.
[0034] The adsorption layer 50, as depicted in FIG. 3, may include
an adsorption zone corrugated sheet 57 and the adsorptive material
coating 46. The adsorption zone corrugated sheet 57 may be in
contact with and extend between two separator plates 52. The
adsorption zone corrugated sheet 57 may comprise a plurality of
adsorption zone fins 58 and a plurality of adsorption zone contact
portions 59. The adsorption zone fin 58 may be the portion of the
adsorption zone corrugated sheet 57 that is perpendicular to and
extends between the separator plates 52. The adsorption zone
contact portion 59 may be the portion of the adsorption zone
corrugated sheet 57 that is parallel to and in contact with the
separator plate 52.
[0035] The adsorption zone fins 58 may be positioned about
perpendicular to the separator plates 52 and may extend about
parallel to the adsorption flow line 54. The adsorption zone fins
58 may direct the flow of adsorbate 60 (see FIG. 2a) through the
adsorption heat exchanger 40 and may provide a support for at least
a portion of the adsorptive material coating 46. The adsorption
zone fin 58 may be in contact with and extend between two separator
plates 52. For some applications the adsorption zone fin 58 may
have an adsorption fin height 61 of between about 0.10 inches and
about 0.5 inches. The adsorption fin height 61 may vary with
application and may depend on factors including the composition of
the adsorption zone fin 58 and the application. For example, for an
automotive cooling system having adsorption zone fins 58 comprising
aluminum, the adsorption fin height 61 may be about 0.250 inches.
For some applications the adsorption zone fin 58 may have an
adsorption fin thickness 64 of between about 0.001 inches and about
0.01 inches. The adsorption fin thickness 64 may vary with
application and may depend on factors including the composition of
the adsorptive material coating 46 and the application.
[0036] The density of adsorption zone fins (fins/inch) may vary
with application and may depend on factors including the thickness
of the adsorptive material coating 46 and the desired volume of the
adsorption flow passage 53. The density of the adsorption zone fins
58 may be defined as the number of fins per inch of adsorption
layer width as measured perpendicular to the adsorption flow line
54 and parallel to the separator plate 52. For some applications,
the density of the adsorption zone fins 58 may be between about 7
fins/inch and about 28 fins/inch.
[0037] The adsorption zone contact portions 59 may be positioned
about parallel to and in contact with the separator plates 52. The
adsorption zone contact portions 59 may be brazed to an adsorption
zone facing side 62 of the separator plates 52. The adsorption zone
contact portions 59 may provide a support for at least a portion of
the adsorptive material coating 46, as depicted in FIG. 3. In other
words, one side of the adsorption zone contact portion 59 may be
brazed to the separator plate 52 and the other side may be coated
with the adsorptive material coating 46. For some applications the
adsorption zone contact portions 59 may have an adsorption contact
portion width 63 of between about 0.035 inches and about 0.15
inches. The adsorption contact width 63 is not an independent
parameter. Once the density of the adsorption zone fins 58 and the
adsorption fin thickness 64 have been specified the adsorption
contact width 63 is a determinate value. The adsorption contact
portion width 63 may vary and may depend on the desired density of
the adsorption zone fins 58. The adsorption contact portion width
63 may be inversely proportion to the density of the adsorption
zone fins 58.
[0038] For some applications, in lieu of the adsorption zone
corrugated sheet 57, the adsorption layer 50 may comprise a
plurality of adsorption zone fins 58 brazed directly to the
separator plates 52. The adsorption zone fins 58 of the adsorption
layer 50 may increase the surface area available for adsorptive
material coating 46, thereby enhancing the adsorption/desorption
efficiency of the adsorption heat exchanger 40.
[0039] The adsorption layer 50 may include two adsorption zone
header bars 65, as depicted in FIG. 2a. The adsorption zone header
bars 65 may be positioned parallel to the adsorption flow line 54.
One adsorption zone header bar 65 may be positioned at one side of
the adsorption layer 50 and the other adsorption zone header bar 65
may be positioned at the opposing side of the adsorption layer 50.
The adsorption zone header bars 65 may be brazed to the separator
plates 52 and may provide structural support to the adsorption heat
exchanger 40.
[0040] The adsorption zone corrugated sheet 57, the adsorption zone
fin 58, the adsorption zone contact portion 59 and adsorption zone
header bar 65 each may comprise a material, such as but not limited
to, aluminized mylar, a polymer composite, or a metal. Useful
metals may include aluminum, copper, titanium, brass, stainless
steel, other light metals and alloys with high conductivity, and
graphite fiber composite materials. Components of the adsorption
layer 50 may provide support for the adsorptive material coating
46.
[0041] The adsorptive material coating 46 of the adsorption layer
50 may define the adsorption flow passage 53, as depicted in FIG.
3. For some embodiments of the present invention, the adsorptive
material coating 46 may define at least a portion of the adsorption
flow passage 53. The adsorptive material coating 46 may be
positioned on and in contact with the adsorption zone fins 58.
Additionally, the adsorptive material coating 46 may be positioned
on and in contact with the adsorption zone contact portions 59.
Further, the adsorptive material coating 46 may be positioned on
and in contact with at least a portion of the adsorption zone
facing side 62 of the separator plates 52, as depicted in FIG. 3.
The composition of the adsorptive material coating 46 may vary with
application and may include an adsorbent, such as but not limited
to silica gel, aluminas, silicas, zeolites, activated carbon, metal
hydrides, metal chlorides, deliquescent salts such as Na.sub.2SO4,
Ca SO4, synthetic polymers, and mixtures thereof.
[0042] For some embodiments of the present invention, the
adsorptive material coating 46 may include a zeolite. Zeolites may
comprise microporous aluminosilicate compounds and may be commonly
referred to as molecular sieves. Molecular sieves may have the
ability to selectively adsorb molecules based primarily on a size
exclusion process. This may be due their very uniform pore
structure and molecular dimensions. The maximum size of the
molecular or ionic species that can enter the pores of a zeolite
may be controlled by the diameter of the pores. Zeolites have been
widely used in industrial processes due to their structural
stability and inherent exothermic reaction during adsorb/desorb
cycles.
[0043] Useful adsorptive material coating compositions and methods
for application may include the compositions and methods described
in U.S. Pat. Nos. 5,120,694 and 5,518,977, both of which are
incorporated herein by reference. Useful adsorptive coating
application methods may comprise a step of heating a component to
be coated, a step of contacting the surface of the component with a
slurry comprising an adsorbent and a binder to form an adsorptive
material coating 46, and a step of hardening the adsorptive
material coating 46. For some applications, the step of contacting
may comprise dipping the surface into the slurry or spraying the
surface with the slurry.
[0044] The adsorptive material coating 46 may have an adsorptive
coating thickness 77 (see FIG. 3) of between about 0.004 inches and
about 0.040 inches. The adsorptive coating thickness 77 may be
measured through the adsorptive material coating 46 and about
perpendicular to the adsorption zone fin 67. For some applications,
the adsorptive coating thickness 77 may be less than about 0.5 mm.
The adsorptive coating thickness 77 may vary with application and
may depend on factors including the dimensions of the adsorption
zone fins 58, the desired dimensions of the adsorption flow passage
55 and the application. For some embodiments of the present
invention a thin adsorptive coating (less than about 0.4 mm) may
allow for a greater density of adsorption zone fins 58, increasing
adsorptive material coating surface area.
[0045] The adsorptive material coating surface area (external or
face area of the coating) may not affect the adsorptive surface
area (surface area available for adsorption). Due to the
micro-porous structure of the adsorptive material coating 46 the
adsorptive surface area may be a function of the mass of adsorptive
material coating applied as opposed to the external or face area of
the coating. For a given mass of adsorptive material coating 46,
increasing the external or face area of the coating may increase
heat transfer efficiency because an increased face area may allow
for a reduction in adsorptive coating thickness 77. The coating
surface area (both the face area and the adsorptive surface area)
may be increased further by the application of adsorptive material
coating 46 to the adsorption zone facing side 62 of the separator
plates 52 and to the adsorption zone contact portions 59.
[0046] The heat transfer layer 51 may include a heat transfer zone
corrugated sheet 66, as depicted in FIG. 4. The heat transfer zone
corrugated sheet 66 may be in contact with and extend between two
separator plates 52. The heat transfer zone corrugated sheet 66 may
comprise a plurality of heat transfer zone fins 67 and a plurality
of heat transfer zone contact portions 68. The heat transfer zone
fin 67 may be the portion of the heat transfer zone corrugated
sheet 66 that is perpendicular to and extends between the separator
plates 52. The heat transfer zone contact portion 68 may be the
portion of the heat transfer corrugated sheet 66 that is parallel
to and in contact with the separator plate 52.
[0047] The heat transfer zone fins 67 may be positioned about
perpendicular to the separator plates 52 and may extend about
parallel to the heat transfer flow line 56. The heat transfer zone
fins 67 may direct the flow of heat transfer fluid 69 (see FIG. 2a)
through the adsorption heat exchanger 40. The heat transfer zone
fins 67 may increase the heat transfer efficiency of the adsorption
heat exchanger 40. The heat transfer zone fin 67 may be in contact
with and extend between two separator plates 52. For some
applications the heat transfer zone fin 67 may have a heat transfer
fin height 70 of between about 0.04 inches and about 0.2 inches.
The heat transfer fin height 70 may vary with application and may
depend on factors including the composition of the heat transfer
zone fin 67 and the application. For example, for an automotive
cooling system having heat transfer zone fins 67 comprising
aluminum, the heat transfer fin height 70 may be about 0.050
inches. For some applications the heat transfer zone fin 67 may
have a heat transfer fin thickness 71 of between about 0.003 inches
and about 0.01 inches. The heat transfer fin thickness 71 may vary
with application and may depend on factors including the
composition of the heat transfer fluid 69 and the application.
[0048] The density of heat transfer zone fins (fins/inch) may vary
with application and may depend on factors including the
composition of the heat transfer fluid 69 and the desired volume of
the heat transfer flow passage 55. The density of the heat transfer
zone fins 67 may be defined as the number of fins per inch of the
heat transfer layer width as measured perpendicular to the heat
transfer flow line 56 and parallel to the separator plate 52. For
some applications, the density of the heat transfer zone fins 67
may be between about 10 fins/inch and about 30 fins/inch.
[0049] The heat transfer zone contact portions 68 may be positioned
about parallel to and in contact with the separator plates 52. The
heat transfer zone contact portions 68 may be brazed to a heat
transfer zone facing side 72 of the separator plates 52. For some
applications the heat transfer zone contact portions 68 may have a
heat transfer contact portion width 73 of between about 0.03 inches
and about 0.1 inches. The heat transfer contact portion width 73
may vary and may depend on the desired density of the heat transfer
zone fins 67. The heat transfer contact portion width 73 may be
inversely proportion to the density of the heat transfer zone fins
67.
[0050] For some applications, in lieu of the heat transfer zone
corrugated sheet 66, the heat transfer layer 51 may comprise a
plurality of heat transfer zone fins 67 brazed directly to the
separator plates 52.
[0051] The heat transfer layer 51 may include two heat transfer
zone header bars 74, as depicted in FIG. 2a. The heat transfer zone
header bars 74 may be positioned parallel to the heat transfer flow
line 56. One heat transfer zone header bar 74 may be positioned at
one side of the heat transfer layer 51 and the other heat transfer
zone header bar 74 may be positioned at the opposing side of the
heat transfer layer 51. The heat transfer zone header bars 74 may
be brazed to the separator plates 52 and may provide structural
support to the adsorption heat exchanger 40.
[0052] The heat transfer zone corrugated sheet 66, the heat
transfer zone fin 67, the heat transfer zone contact portion 68 and
heat transfer zone header bar 74 each may comprise a material, such
as but not limited to, aluminized mylar, a polymer composite, or a
metal. Useful metals may include aluminum, copper, titanium, brass,
stainless steel, other light metals and alloys with high
conductivity, and graphite fiber composite materials.
[0053] The separator plate 52 of the adsorption heat exchanger 40
may comprise a sheet material structure, as depicted in FIGS. 2a-c.
The separator plate 52 may be positioned parallel to the layers 50,
51 (see FIGS. 3 and 4). One separator plate 52 may be positioned
between and in contact with each adsorption layer/heat transfer
layer pair. The separator plate 52 may prevent the flow of
adsorbate 60 from entering the heat transfer layer 51 and prevent
the flow of heat transfer fluid 69 from entering the adsorption
layer 50. The separator plate 52 may comprise a material, such as
but not limited to, aluminized mylar, a polymer composite, or a
metal. Useful metals may include aluminum, copper, titanium, brass,
stainless steel, other light metals and alloys with high
conductivity, and graphite fiber composite materials. The width and
length of the separator plate 52 may vary and may be about equal to
the width and length of the layers 50, 51. For some applications, a
separator plate thickness 75 may be between about 0.003 inches and
about 0.1 inches. For example, for some applications the separator
plate thickness 75 may be about 0.016 inches.
[0054] The adsorption heat exchanger 40 further may comprise two
side plates 76, as depicted in FIG. 2a. The side plates 76 may be
positioned parallel to the layers 50, 51. One side plate 76 may be
positioned at one side of the adsorption heat exchanger 40 and the
other side plate 76 may be positioned at the opposing side of the
adsorption heat exchanger 40. The side plates 76 may comprise a
material, such as but not limited to, aluminized mylar, a polymer
composite, or a metal. For some applications, the side plates 76
may be brazed to and provide structural support for the adsorption
heat exchanger 40.
[0055] A method 200 of generating a flow of adsorbate 60 is
depicted in FIG. 5. The method 200 may comprise a step 210 of
passing a flow of heat transfer fluid 69 through at least one heat
transfer layer 51 of an adsorption heat exchanger 40 and a step 220
of transferring heat from the flow of heat transfer fluid 69 to an
absorptive material coating 46 positioned within an adsorption
layer 50 of the adsorption heat exchanger 40 such that an adsorbate
vapor is desorbed from the adsorptive material coating 46. For some
embodiments, as the adsorptive material coating 46 is heated the
adsorbate vapor is desorbed from the adsorptive material coating 46
driving the flow of adsorbate 60 to move toward a condenser 42. For
some applications, the flow of adsorbate 60 must comprise an
adsorbable vapor such as but limited to, water, alcohols, ammonia,
hydrocarbons, chloroflorocarbons, and mixtures thereof.
[0056] The step 210 may comprise passing the flow of heat transfer
fluid 69 such that the flow of heat transfer fluid 69 is in contact
with at least one heat transfer zone fin 67 of the absorption heat
exchanger 40 and in contact with at least a portion of a heat
transfer zone facing side 72 of the separator sheet 52. For some
applications, the flow of heat transfer fluid 69 may comprise a
liquid, such as but limited to, water, alcohols, ammonia,
hydrocarbons, chloroflorocarbons, and mixtures thereof.
[0057] For some applications, the method 200 can use the adsorptive
material coating 46 to reduce the partial pressure of the flow of
adsorbate 60 (e.g. water or other working compound) in an
adsorption loop 45 and thereby cause the adsorbate 60 to be
evaporated from an evaporator 43. The liquid adsorbate 60 inside
the evaporator 43 becomes cooler as it loses the corresponding heat
of vaporization, while the adsorptive material coating 46 becomes
hotter from the heat of adsorption. For some applications, the
regeneration cycle may use a supply of hot water or air heated by
waste heat from an engine exhaust to remove adsorbate 60 and
regenerate the adsorptive material coating 46. Two adsorption heat
exchangers 40 may be used in alternating cycles for some
applications.
EXAMPLE 1
[0058] A plot of specific power (kW/kg) as a function of cycle time
(sec.) is shown in FIG. 6. As it can be seen, high specific power
can be achieved at a much shorter cycle time in comparison with
current tube-plate design. Several fin densities (fpi) for the
adsorption layer were considered. Wash coating process calls for
optimum fpi number. An fpi number of more then 11 may not be
suitable for some applications due to poor drainage of extra wash
coat after its application onto the fin-plate structure.
EXAMPLE 2
[0059] The design parameters for one embodiment of the present
invention are shown FIG. 7. In this example, the components (fins,
plates, etc.) comprise aluminum. Dynamic simulation results of h
for adsorption side (h=553/BTU/hr.ft.sup.2.R) and fpi=11 were used
for the adsorption heat exchanger design. The calculated design
parameters for adsorption side (adsorption layer 50) and HT side
(Ethylene Glycol/Water, (EGW) (heat transfer layer 51) are shown in
FIG. 7. During the sorptive cooling process, adsorption/desorption
side of adsorption heat exchanger was under a total pressure of
5-80 torr depending on the mode (i.e. adsorption or desorption).
The geometry of an embodiment of the adsorption heat exchanger is
shown on FIG. 8. The estimated adsorption heat exchanger core dry
weight is 6.7 lb. As can be seen, embodiments of the present
invention can increase adsorptive material surface area while
reducing adsorption heat exchanger overall dimensions.
EXAMPLE 3
[0060] The sensitivity results on adsorption material coating
thickness variations are shown in FIG. 9. The results show that
specific power decreases when adsorption material coating thickness
increases. Absolute cooling power increases with the increased
adsorption material coating thickness. It should be noted here that
adsorption side heat transfer coefficient would be slightly changed
due to different adsorption material coating thickness, which was
not considered in the sensitivity study.
EXAMPLE 4
[0061] The design and performance parameters for an adsorption heat
exchanger according to nine embodiments of the present invention
are shown in FIG. 10. For comparison, the design and performance
parameters for a prior art plate-tube AHE are also shown. As can be
seen, embodiments of the present invention can provide improved
adsorption heat exchangers. When compared to the prior art
plate-tube AHE, the adsorption heat exchangers of the present
invention have higher specific power and lower cycle times.
[0062] For the prior art tube-plate AHE, heat transfer to
adsorptive material occurs mainly by conductance in a chain of
tube-tube/plate contact-plate-adsorptive material. The quality of
tube-plate and adsorbent-plate contacts is extremely important in
achieving high heat and mass transfer efficiency during
adsorption/desorption cycles and, consequently, for their duration.
Heat and mass transfer efficiency affect the specific power of heat
exchanger.
[0063] The fin-plate design of the present invention can provide
high surface area and enhance heat and mass transfer from the heat
transfer fluid to the adsorbent material. This along with a thinner
adsorbent layer (adsorptive material coating 46) can significantly
reduce adsorption/desorption cycle time and increase the specific
power of the adsorption heat exchanger 40 for some
applications.
[0064] As can be appreciated by those skilled in the art, the
present invention provides improved adsorption heat exchangers.
Embodiments of the present invention provide heat exchangers having
enhanced adsorption/desorption efficiency and high heat transfer
efficiency. The increased adsorptive material surface area and
improved heat transfer efficiency of the present invention can
provide heat exchangers with reduced cycle time.
[0065] It should be understood, of course, that the foregoing
relates to exemplary embodiments of the invention and that
modifications may be made without departing from the spirit and
scope of the invention as set forth in the following claims.
* * * * *