Abstrict An open-cycle air-conditioning apparatus including a rotatable
heat exchanger wheel, a rotatable moisture transfer wheel, evaporative
elements, and heating means disposed between the heat exchanger
wheel and the transfer wheel wherein both wheels are constructed
of spaced alternate layers of material mounted on a hub with means
for forming a plurality of axial passages in the area between the
layers. The moisture transfer wheel has an absorbent material alternating
with a rigid polymeric material and the heat exchanger has rigid
material of a low thermal conductivity, such as a rigid polymer
forming both layers. In each instance, axial passages exist between
the layers. Both wheels have outer semi-rigid rims and a plurality
of rigid spokes secured to and extending radially from the hub,
through the material and the rim for structurally strengthening
the wheels and terminating in a threaded end with a cooperating
nut for truing the wheel through adjustment of the nuts. Baffles
may be included between the two wheels on the air input side so
as to prevent undesirable intermingling of air having different
temperatures and humidities. A moisture impervious grid may be formed
through the absorbent material to prevent migration of the desiccant
material contained therein. Solar heat coils are used for the heating
requirements.
Claims What is claimed is:
1. In an open-cycle air-conditioning apparatus including a rotatable
heat exchanger wheel, a rotatable desiccant carrying moisture transfer
wheel, evaporator means, heating means disposed between said heat
exchanger wheel and moisture transfer wheel, and means for passing
air through said heat exchanger wheel and said moisture transfer
wheel in an intake/exhaust path, the improvement in said moisture
transfer wheel comprising
a hub and shaft assembly;
alternate layers of rigid material and absorbent material wound
about said hub and shaft so as to form a wheel of a predetermined
diameter and width;
means between said alternate layers for forming axial passages
across said wheel;
a semi-rigid rim secured about the circumference of said wheel;
a plurality of rigid spokes secured to said hub and passing radially
through said alternate layers and said rim for structurally strengthening
said wheel; and
adjustable means on said spokes bearing against the exterior of
said rim for truing said wheel.
2. In an open-cycle air-conditioning apparatus including a rotatable
heat exchanger wheel, a rotatable desiccant carrying moisture transfer
wheel, evaporator means, heating means disposed between said heat
exchanger wheel and moisture transfer wheel, and means for passing
air through said heat exchanger wheel and said moisture transfer
wheel in an intake/exhaust path, the improvement in said heat exchanger
wheel comprising
a hub and shaft;
first and second layers of rigid material alternately wound about
said hub and shaft so as to form a wheel of a predetermined width
and diameter;
means between said first and second layers for forming axial passages
across said wheel;
a semi-rigid rim secured about the circumference of said wheel;
a plurality of rigid spokes secured to said hub and passing radially
through said first and second layers of said film and said rim for
structurally strengthening said wheel; and
adjustable means on said spokes bearing against the exterior of
said rim for truing said wheel.
3. The apparatus of cliam 2 wherein said means for forming said
axial passage comprises
corrugations in one of said rigid layers.
4. The apparatus of claims 1 or 2 wherein said rigid spokes are
arranged in pairs on opposite sides of said wheel, with the spokes
of each pair being axially aligned across said wheel.
5. In an open-cycle air-conditioning apparatus including a rotatable
heat exchanger wheel, a rotatable moisture transfer wheel, evaporator
means, heating means disposed between said heat exchanger wheel
and moisture transfer wheel, and means for passing air through said
heat exchanger wheel and said moisture transfer wheel in an intake/exhaust
path, the improvement in said moisture transfer wheel comprising
a hub and shaft assembly having a predetermined width;
alternate layers of rigid material and absorbent material wound
about said hub and said shaft so as to form a wheel of a predetermined
diameter and width;
means between said alternate layers for forming axial passages
across said wheel;
a desiccant carried on and within said absorbent material; and
a moisture impervious grid impregnated in and extending to the
surface of said absorbent material so as to prevent migration of
said desiccant within said absorbent material during rotation of
said wheel and to inhibit spillage of said desiccant when said wheel
is at rest.
6. The apparatus of claims 1 or 5 wherein said means for forming
said axial passages comprises
corrugations in said rigid layer.
7. The apparatus of claims 1 or 2 or 5 wherein said means for forming
said axial passages comprises
a plurality of substantially transverse walls extending between
said layers.
8. The apparatus of claims 1 or 2 or 5 wherein said means for forming
said axial passages comprises
a plurality of transverse abutting tubes secured between said layers.
9. The apparatus of claims 1 or 5 wherein said rigid material is
a polymer film.
10. The apparatus of claims 1 or 5 wherein said absorbent material
is paper.
11. The apparatus of claims 1 or 5 wherein said absorbent material
is a non-woven polymer.
12. The apparatus of claim 5 wherein said moisture impervious grid
is glue.
13. The apparatus of claim 15 wherein said absorbent material comprises
a non-woven polymer.
14. The apparatus of claim 5 wherein said absorbent material comprises
paper.
15. In an open-cycle air-conditioning apparatus including a rotatable
heat exchanger wheel, a rotatable desiccant carrying moisture transfer
wheel, evaporator means, heating means disposed between said heat
exchanger wheel and moisture transfer wheel, and means for passing
air through said heat exchanger wheel and said moisture transfer
wheel in an intake/exhaust path, the improvement in said apparatus
comprising
at least one baffle means extending between said moisture transfer
wheel and said heat exchanger wheel parallel to the air flow in
said air intake path, said baffle means extending between the axes
and outer periphery of said wheels, so as to prevent undesirable
intermingling of air having different temperatures and humidity
levels in said intake path between said wheels.
16. The apparatus of claims 1 2 5 or 15 wherein said desiccant
is lithium chloride.
17. The apparatus of claims 1 2 5 or 15 wherein said heating
means is a solar coil.
18. The apparatus of claim 15 wherein said baffle means is a rigid
plate extending radially from and adjacent to the axis of said wheels
to the outer portion of said wheel in said air intake path.
19. A rotary moisture transfer wheel for removal of moisture from
air passing therethrough in an intake/exhaust path comprising
a hub and shaft assembly;
alternate layers of rigid material and absorbent desiccant carrying
material wound about said hub and shaft so as to form a wheel of
a predetermined diameter and width;
means between said alternate layers for forming axial passages
across said wheel;
a semi-rigid rim secured about the circumference of said wheel;
a plurality of rigid spokes secured to said hub and passing through
said alternate layers and said rim for structurally strengthening
said wheel; and
adjustable means on said spokes bearing against the exterior of
said rim for truing said wheel.
20. The wheel of claim 19 wherein said means for forming said axial
passages comprises
corrugations in said rigid layer.
21. The wheel of claim 19 wherein said means for forming said axial
passages comprises
a plurality of substantially transverse walls extending between
said layers.
22. The wheel of claim 19 wherein said means for forming said axial
passages comprises
a plurality of transverse tubes secured between said layers.
23. The wheel of claim 19 wherein said absorbent material is paper.
24. The wheel of claim 19 wherein said absorbent material is a
non-woven polymer.
25. The wheel of claim 19 wherein said rigid material is a polymer
film.
26. The wheel of claim 19 wherein said desiccant is lithium chloride.
27. The wheel of claim 19 wherein said absorbent material is impregnated
with a moisture impervious grid.
28. The wheel of claim 27 wherein said moisture impervious grid
is glue.
29. A rotary counter flow heat exchanger wheel for changing the
temperature of air passing therethrough comprising
a hub and shaft;
first and second layers of rigid polymer material alternately wound
about said hub and shaft so as to form a wheel of a predetermined
width and diameter;
means between said first and second layers for forming axial passages
across said wheel;
a semi-rigid rim secured about the circumference of said wheel;
a plurality of rigid spokes secured to said hub and passing radially
through said first and second layers of said film and said rim for
structurally strengthening said wheel; and
adjustable means on said spokes bearing against the exterior of
said rim for truing said wheel.
30. The wheel of claim 29 wherein said means for forming said axial
passages comprises
corrugations in said first layer.
31. The wheel of claim 29 wherein said means for forming said axial
passages comprises
a plurality of substantially transverse walls extending between
said first and second layers.
32. The wheel of claim 29 wherein said means for forming said axial
passages comprises
a plurality of transverse tubes secured between said first and
second layers.
33. The wheel of claim 29 wherein said layers of polymer film have
a thermal conductivity less than 3.00 BTU/Hr Ft.sup.2 .degree. F./in.
34. The wheel of claim 29 wherein said layers of polymer film have
a specific heat greater than 0.25 BTU/Lb..degree. F.
35. The wheel of claim 29 wherein said layers of polymer film have
a density greater than 70 lb/ft.sup.3.
36. The wheel of claim 19 or 29 wherein said rigid spokes are arranged
in pairs on opposite sides of said wheel with the spokes of each
pair being axially aligned across said wheel.
Description This invention relates generally to air-conditioning systems and
more particularly to open cycle desiccant air-conditioning systems
and to the moisture transfer wheel and the heat exchangers wheel
used therein.
BACKGROUND OF THE INVENTION
Open cycle air-conditioners are known in the art and have been
based primarily on one system, known as the Munters Environmental
Control system (MEC) unit as described in U.S. Pat. No. 2926502.
As set forth in this patent, the basic open-cycle air-conditioner
operates by dehumidification and subsequent cooling of air wherein
moist hot air is conditioned by basically a multi-stage process
to produce cool air.
In open-cycle air-conditioning systems, a basic multi-step approach
is used. Outside air is subjected to removal of moisture through
a moisture transfer wheel, with the dried air being cooled by means
of a heat exchanger wheel with the subsequent addition of moisture
by an evaporative element so as to further cool the air before it
enters the area to be conditioned. In the return cycle, the air
passes through an exhaust path which includes a further evaporative
element, the heat exchanger wheel, a heating element and through
the moisture transfer wheel for driving moisture therefrom so as
to regenerate the wheel, and is exhausted to the atmosphere.
One of the major advantages of this type of system is that a constant
supply of fresh, filtered air is delivered to the space to be conditioned
as opposed to the recirculation of air as is found in standard heating
and cooling systems.
Known units which have been subject to experimental use provide
gas or electrical units in the heating portion of the cycle prior
to exhaust through the moisture transfer wheel. Additionally, during
the colder winter months, a gas or electrical heating unit may be
used in the intake path after the heat exchange wheel for heating
the air passing into the area to be conditioned. In this latter
mode, the moisture transfer wheel is substantially non-operative.
During recent years, a number of concepts have been proposed for
using solar equipment for cooling systems. Among such proposals
has been investigations of desiccant air-conditioning systems. However,
to applicants' knowledge, no system has been developed which attains
a coefficient of performance which would make such systems economically
feasible.
The basic principle of the MEC system is that dry warm air can
be simultaneously cooled and humidified by contacting it with water
vapor. However, in geographic areas where the air is both warm and
humid, it must be dried before it can be cooled by evaporation.
The efficiency and the effectiveness of an open-cycle air-conditioning
system depends upon the ability of the unit to dehumidify the warm
moist air input, and upon the effectiveness of the heat exchanger
wheel or unit.
Many types of water removal system have been proposed, among which
are the rotating moisture transfer wheel which is regenerated in
a manner as discussed above. Various desiccants have been proposed
for use in this type of wheel. Conventional desiccants used with
these wheels are salts, such as lithium chloride, which is used
as the drying agent and which is impregnated or sprayed upon the
wheel material. Some of the problems involved with the moisture
transfer wheels are structural strength, proper balancing and truing
and the prevention of "weep". Weep is the condition wherein
the salts have a tendency to deliquesce or form aqueous solutions
that drip from the wheel. This causes the solutions to either flow
out of the unit or to be stripped by the flowing air. When this
condition occurs, it leaches the wheel of its absorbent material,
substantially reducing its efficiency. With known wheels, this also
has a tendency to cause channel collapse or plugging within the
wheel. As a result, the amount of the salt used has necessarily
been limited to a low level which results in a major reduction in
the efficiency of a wheel of given size relative to the removal
of moisture from the air.
As to the heat exchanger wheel, operation depends upon the opposite
faces remaining at different temperatures. This means that there
must be a significant temperature gradient across the wheel in the
axial direction. Proposed use of highly thermally conductive material
such as metal results in the temperature gradient through the wheel
being substantially less, with poor heat exchange and low effectiveness.
In the open-cycle air-conditioner system, the heat created by the
drying of the air by the moisture transfer wheel must be removed
by the heat exchanger wheel. However, migration of the heat axially
in the direction of flow of the air through the wheel must be kept
to a minimum. If the heat does so migrate, the air stream to be
treated exiting from the heat exchanger wheel will not be sufficiently
cooled to render the system practical for air-conditioning reasons
because the evaporator would not be capable of reducing the higher
temperature to an acceptable level of temperature and humidity.
Non-thermally conductive wheel materials such as wax coated asbestos
have been previously proposed since they avoid this problem. However,
in addition to health hazards, such material presents structural
problems relative to balance and truing of the wheel.
Although the thermal gradient across a metallic heat exchanger
might be partially counteracted by making the heat exchanger thicker,
the increased thickness causes a proportionally increased pressure
drop which increases the energy requirement for movement of the
required air volume. Additionally, it adds to the weight and bulk
of the wheel. To obtain comparable heat exchange in an aluminum
wheel of the same design as a wheel which is non-thermally conductive
the thickness of the metal wheel would have to be increased due
to the difference in thermal conductivity. It has been determined
that the maintenance of a suitable temperature gradient across the
heat exchanger wheel of an open-cycle air-conditioner is extremely
important since the wheel must operate at above 90% effectiveness
to provide satisfactory cooling of the treatment stream. A thorough
discussion of heat exchangers and the problems inherent therein
as relate to the process under consideration is discussed in Compact
Heat Exchangers, Kays and London, McGraw Hill Book Company.
Various structural configurations have been proposed for improving
the effectiveness of metallic heat exchangers, one such proposal
being disclosed in U.S. Pat. No. 3965695 issued June 29 1976
wherein a honeycomb type of construction is proposed. This type
of construction requires a considerable amount of metallic material
and inherently includes particular manufacturing problems as well
as creating a wheel of substantial bulk and weight.
A further problem involved in the open-cycle desiccant air-conditioning
system is the problem of temperature transfers due to carry over
between the cooling half of the cycle and the heating half of the
cycle, that is, the intake air path and the exhaust air path. Also,
in the known systems, the amount of heat energy required to regenerate
the absorbent material has often resulted in a high heat input rate
which leads to a poor thermal coefficient of performance (COP) for
the system.
Another problem encountered in known systems is that desiccants
such as lithium chloride and lithium bromide become chemically unstable
and will deteriorate in the presence of products of combustion such
as an open gas flame introduced as the heating element preceding
the desiccant wheel in the exhaust path. This is due to the mixture
of the combustion products of the gas with the desiccant itself.
Accordingly, it is an object of the invention to provide an improved
open-cycle air-conditioning systems with increased coefficient of
performance.
A further object of the present invention is to provide an improved
system operation of an open-cycle desiccant air-conditioning system.
A still further object of the invention is to provide an improved
desiccant wheel for more effectively drying the air intake to the
system.
A further object of the invention is to provide an improved heat
exchanger wheel so as to substantially increase the effectiveness
thereof and, thus, the coefficient performance of the entire system.
A still further object of the invention is to more effectively
control the mixture of the air transferred between the desiccant
wheel and the heat exchanger wheel in the intake air path.
Yet another object of the invention is to provide a means for substantially
reducing the transfer of acqeous solutions within the absorbent
material of the desiccant wheel.
Still another object of this invention is the use of a solar energy
system integrated into desiccant cooling apparatus.
These and other objects of the invention will be obvious from the
following description when taken with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic showing of the basic system of the present
invention;
FIG. 2 is a plan view of the wheel construction having the rod
supports secured therein;
FIG. 3 is a sectional view taken generally along the lines 3--3
of FIG. 2;
FIG. 4 is a partial sectional view taken along the lines 4--4 of
FIG. 3;
FIG. 5 is a partial break-away view of the moisture transfer wheel
of FIG. 1;
FIG. 6 is a partial break-away view of the heat exchanger wheel
of FIG. 1;
FIG. 7 is a partial view of a section of the moisture absorbent
material used in the moisture transfer wheel;
FIG. 8 is a perspective view of one of the wheels of FIG. 1 mounted
within a housing;
FIG. 9 is a partial perspective view showing a means for rotating
the wheels of FIG. 1;
FIG. 10 is a perspective schematic showing the use of baffles within
the system of FIG. 1.
FIG. 11 is a partial break-away view of a modification of the heat
exchanger wheel of FIG. 1; and
FIG. 12 is a partial break-away view of a further modification
of the heat exchanger of FIG. 1.
SUMMARY OF THE INVENTION
The present invention discloses an open cycle air-conditioning
apparatus including a rotatable heat exchanger wheel, a rotatable
desiccant carrying moisture transfer wheel, evaporative elements,
and heating means disposed between the heat exchanger wheel and
the transfer wheel on the exhaust air path. Both wheel are constructed
of spaced layers of material mounted on a hub with means for forming
a plurality of axial passages in the area between the layers. The
moisture transfer wheel has absorbent material alternating with
a rigid material and the heat transfer wheel has rigid layers of
material having a very low thermal conductivity with the passages
formed therebetween. Both wheels have outer semi-rigid rims and
rigid spokes for structurally strengthening the wheels, said spokes
extending radially from the hub, through the material and the rim
and terminating in a threaded end with a cooperating nut for truing
the wheel through adjustment of the nuts. Baffles may be included
between the two wheels on the air intake side so as to prevent undesirable
intermingling of air having different temperatures and humidity
levels within the intake air path between the moisture transfer
wheel and the heat exchanger wheel. A moisture impervious grid may
be formed through the absorbent materials so as to prevent migration
of the desiccant material contained therein.
DETAILED DESCRIPTION
Turning now to the drawings, FIG. 1 illustrates a schematic of
the basic open-cycle air-conditioning system of the present invention.
A moisture transfer wheel 11 constitutes the exterior or outside
element of the system. As will be noted and discussed later it is
separated into two sections so as to provide an intake path and
an exhaust path as indicated by the arrows. A heat exchanger wheel
13 also partitioned so as to provide intake and exhaust paths is
located substantially adjacent to wheel 11 separated only by the
solar heat regeneration coil 19. Auxiliary solar heating coil 21
may be placed in the system for use in cold months when it is desirable
to heat the interior of the area rather than to cool it. The solar
coils include fluid pipes which are interconnected with standard
solar heating units (not shown). The basic unit terminates in evaporator
elements 15 and 17 separated by partition 16 with the arrows indicating
the intake air into the building and the air exhausting therefrom.
Supply blower 23 and exhaust blower 25 are provided so as to implement
the necessary air movement within the system.
As is well known, this type of system provides removal of the moisture
from the intake air by the moisture transfer wheel which, because
of the moisture removal, increases the temperature of the air which
then passes through heat exchanger wheel 13 so as to lower the temperature
of the warm dry air. Evaporator element 15 adds moisture to the
air, thus reducing the temperature further and supplying cool air
to the conditioned area. The exhaust air passes through evaporator
element 17 and through heat exchanger wheel 13 so as to remove heat
from the heat exchanger and raise the temperature of the exhaust
air. The temperature of the exhaust air is further raised by means
of solar heating element 19 so as to provide high temperature air
in the exhaust path resulting in regeneration of the moisture transfer
wheel. The air from the moisture transfer wheel is exhausted into
the atmosphere.
The two elements of the system which primarily govern the coefficient
performance (COP) of the system are moisture transfer wheel 11 and
heat exchanger wheel 13. With the exception of the specific material
used in these wheels, they may be constructed in substantially the
same manner and may use the same structural support and truing system
of the present invention.
FIG. 2 is a plan view illustrating the basic construction of both
wheel 11 and wheel 13. The basic wheel matrix 29 is indicated with
a subsequent discussion of the materials used therein for the moisture
transfer wheel and the heat exchanger wheel. In both wheels, dual
continuous rolls of material are slit to the proper width and are
tension wound onto hub and shaft assembly 27 until the desired overall
diameter is obtained. A plurality of axial passages are formed between
the continuous rolls in a manner to be subsequently discussed. Outer
rim 40 of semi-rigid material, such as metal rolled to the appropriate
curvature, is then installed about the wheel. In a preferred construction
method, both faces of the wheel are then routed or grooved so as
to provide for the installation of a plurality of rigid spokes 35.
Holes are bored through rim 40 and spokes 35 which are threaded
at both ends, are passed through the holes in the rim and through
the routed slots in the matrix and screwed into pretapped holes
in the hub. Referring to FIG. 3 it can be seen that pairs of spokes
are disposed on opposite sides of the wheel with the spokes of each
pair being axially aligned. The outermost inch of the wheel is also
routed about its periphery so as to provide channel 32 as a working
area while inserting and adjusting spokes 35. The outer end of rods
35 and 36 are threaded so as to receive nuts 37 and 38. When the
rods are in place, they are bonded to the matrix with heat set flexible
compound and the routed slots are filled with polyester compound
39 as shown in FIG. 4. Channel 32 on the outer circumference of
the wheel is also filled with a polyester compound and the entire
wheel is then smoothed so as to meet with the circumferential seals
and with the face of the matrix. It is preferred that spokes on
opposite sides of the wheel be axially aligned so that the least
possible resistance is provided relative to the air passing through
the wheel.
FIG. 5 illustrates a preferred internal matrix structure of the
moisture transfer wheel 11. A continuous role of polymer film 31
alternates with moisture absorbent material 33 such as paper or
non-woven polymer. The polymer film is formed so as to provide a
plurality of axial passaes 35. In the illustration of
FIG. 5 these passages are formed by a corrugated polymer film.
Other possible configurations will be discussed in connection with
FIGS. 11 and 12. The wheel is charged with a desiccant solution
preferrably lithium chloride, either by a spray application to the
wheel bases or by submersion of the wheel in a bath.
FIG. 6 shows the construction of the heat exchange wheel. It is
composed of alternating layers of rigid material such as polymer
film, each having a low thermal conductivity of less than 3.0 BTU
hr./Ft..sup.2 .degree. F./in. and high specific heat of at least
0.25 BTU/lb..degree. F. and having a high density. As discussed
above, one of the layers may be formed so as to provide axial passages
44. The particular configuration illustrated in FIG. 6 is corrugated
sheet 42. Alternate configurations are discussed in connection with
FIGS. 11 and 12. A lower thermal conductivity increases the temperature
gradient across the wheel. A high specific heat and density minimizes
the required total volume of the ultimate matrix, thereby minimizing
not only the weight of the device but the resistance to fluid flows.
Tests have shown that the rotary heat exchanger constructed in this
fashion with this material has a performance which very closely
matches the theoretical predictions of Kays and London in the above
mentioned text.
The spoke assembly of both of the wheels provides structural strength
for the exchanger which is substantially equivalent to metal wheel
as well as a means of adjustment for minimizing axial play while
the wheel is rotating. Additionally, using this construction, the
wheel can be "trued up" to close tolerances by adjustment
of the nuts allowing a highly effective sealing system to prevent
loss or entrance of air with the enclosed system.
Since lithium chloride liquifies as it absorbs moisture from the
air, it is preferred to treat the moisture absorbent material in
such a manner such as to prevent migration of this liquid. FIG.
7 shows a preferred method of accomplishing this purpose. Before
paper 33 is wound on the hub, it is provided with grid 34 which
extends through the material itself. One of the preferred means
for obtaining this grid is to soak it with a glue in the grid pattern
in thin lines as shown. After the glue dries, solution within one
of the square grids will not migrate into an adjacent grid.
FIG. 8 discloses a structure for enclosing and supporting either
the wheel 11 or the wheel 13. The wheel is shown as supported in
housing 45 having a circumferential opening 47 on both sides thereof.
The opening is divided into two separate air passages, intake air
passage 48 and the exhaust air passage 50 by means of partition
53. The wheel is mounted on axle 54 so as to be freely rotatable
within housing 45.
As discussed above, it is essential to assure that the smallest
amount of air may pass between intake air passage 48 and exhaust
air passage 50 within the system itself. When the system is assembled,
all units abut so as to effectively form an air intake duct and
an exhaust duct. However, in order to prevent leakage of air between
the ducts, sealing strips 55 and 57 of a semi-flexible material
such as rubber covered with a low friction surface are secured about
the circumference of each of the hemispherical air passages by means
such as screws or rivets 59.
FIG. 9 discloses one means for rotating the wheel which includes
a belt 61 driven by a motor 63 with associated pulley 62. It will
be appreciated that this is a continuous belt that extends about
the drum making contact therewith with the exception of the area
adjacent the pulley.
Turning now to FIG. 10 there is shown schematically the moisture
transfer wheel 11 and heat exchanger wheel 13 as separated by the
various partitions within the system together with the use of a
baffle 71 between the two wheels. It is to be understood that a
number of baffles could be used as indicated by the phantom lines.
The baffles are preferably composed of a rigid polymer or other
rigid material such as metal, and are oriented parallel to the duct
air flow in the intake air passage. The baffles are mounted so as
to extend radially from between the axes of the wheels to the outer
wall of the duct. As indicated, the baffles extend between the moisture
transfer wheel and the rotary heat exchanger and are mounted so
as to be in close proximity with the wheel faces at each end of
the baffle.
The purpose of the baffles is to prevent mixing of the air exiting
from the moisture transfer wheel, which exhibits a marked gradient
in temperature and humidity with increasing rotation angle. As indicated,
the moisture transfer wheel and the rotary heat exchanger wheel
rotate in opposite directions. The air leaving the matrix of wheel
11 in the area which has first entered the supply air stream is
the hottest and most humid air in the supply stream, while air leaving
from the matrix of wheel 11 in the area which is about to pass beyond
the intake air stream will generally be the coolest and least humid.
As an example, the temperatures can range from 170.degree. F. for
the air in the area which has just entered the supply air stream,
to 110.degree. F. for the air in the area which is about to leave
the supply air stream as the wheel rotates. The prevention of mixing
of these various temperature gradients in the air through the use
of baffles improves performance of the air conditioner in two ways.
First, it assures that the lowest quality of air in the supply stream
is the air which reaches the rotary heat exchanger in the area which
is carried over inside the matrix of the rotary heat exchanger 13
to the regeneration air stream. Secondly, maintaining temperature
stratification of the air stream results in a radial counter flow
effect in the rotary heat exchanger, thus improving its performance.
As will be obvious, the matrix of the rotary heat exchanger encounters
the coolest air in the area where it first enters the air stream
and the hottest air in the area where it leaves the supply air stream.
Thus, the air that is carried over into the exhaust stream as the
heat exchanger wheel 13 rotates is the hottest air presented into
the exhaust path between wheel 13 and wheel 11. As stated, a plurality
of baffles may be used as indicated by the dotted lines in FIG.
10 so as to further enhance the separation of the intake air stream.
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