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SUMMARY OF THE INVENTION
There are numerous concepts for the collection of solar radiation. These
concepts range from the most simple--a window--to those that are quite
complex and require advanced technology for their development, such as
solar cells, for instance.
Of the many heat collection concepts presently being developed, the
relatively simple flat-plate collector has found the widest application.
Its low fabrication, installation and maintenance cost, as compared to
higher temperature heat collection shapes, has been the primary reason for
its widespread use. Additionally, flat-plate collectors can be easily
incorporated into a building shape, provided the tilt and orientation are
properly calculated.
As is well known in the art, a flat-plate collector generally consists of a
solar radiation absorbing plate or panel, often metallic, which may be
flat, corrugated or grooved. The plate may be painted black, or provided
with other absorptivity increasing coatings, to increase absorption of the
sun's heat. In general, such collectors are covered with a solar radiation
transmissive cover sheet to trap heat within the collector and reduce
convective cooling of the absorber. The captured solar heat is removed
from the absorber by means of a working fluid, generally air or water,
which is heated as it passes through or near the radiation absorbing
plate. The heated working fluid is then transported to points of use or to
storage depending on energy demand.
It has been found that the collection efficiency of such solar collectors
can be significantly improved by providing the radiation absorbing panel
or plate with a plurality of continuous upstanding fins arranged in spaced
relationship so as to form fluid passageways extending between the solar
panel inlet and outlet. Generally, the continuous fins are positioned
normal to the absorbing plate such that solar rays reflected from a
particular absorptive surface area on the fins or the absorbing plate will
be absorbed by other surface areas, thereby preventing reflection of the
solar radiation through the solar radiation transmissive cover.
Furthermore, the fins tend to act as turbulators increasing turbulance of
the fluid and thereby increasing the effectiveness of heat transfer from
the panel surfaces to the working fluid. A novel arrangement for such
continuous fins is illustrated in my co-pending application Ser. No.
06/031,227, filed Apr. 18, 1979 and entitled Solar Heat Collecting Unit
For Forced Air Systems. In the preferred embodiment described therein, the
upstanding sinuous parallel spaced fins are provided with a number of tabs
projecting downwardly at spaced locations from the lower edge of the fins,
which cooperate with similarly spaced slots in the absorptive plate to
provide means for attaching the fins to the plate. In other embodiments,
the fins are resistance welded to the supporting absorptive plate. In
either event, these methods of construction require that the fins and
plate be separately fabricated, and that an additional fabrication step be
required to join the fins and plate together, significantly decreasing the
cost effectiveness of such flat-plate collectors.
The present invention is directed to a solar radiation absorbing panel for
use with a fluid heating solar collector of the type described above
including an absorbing plate having means projecting upwardly from the
upper surface of the panel to increase the collecting efficiency of the
solar collector and for forming air passageways for directing fluid from
the inlet to the outlet. The resulting panel is constructed in such a
manner as to eliminate the separate fabrication step of attaching the fins
to the underlying plate inherent in prior art solar radiation absorbing
panels. In a preferred embodiment, the panel comprises a substantially
flat plate-like rectangular sheet of solar radiation absorptive material,
which may be provided with additional solar radiation absorption enhancing
coatings, bounded by spaced side and end edges, the end edges forming the
fluid inlet and outlet, respectively, of the panel.
Means project upwardly from the upper surface of the panel for forming a
plurality of parallel sinuous air passageways for directing the working
fluid from the inlet to the outlet. In a preferred embodiment, these means
are formed by a plurality of individually formed tab members extending
upwardly from the upper surface of the panel. Each rectangular-shaped tab
member is formed by making a C-shaped cut in the panel, leaving one edge
of the tab member attached to the panel. The tab member is then bent
upwardly to a vertical position such that the tab member is directed
generally from the inlet edge of the panel toward one of the side edges at
a 45.degree. angle with respect to the inlet edge.
A second tab member is formed in a similar manner such that the adjacent
edges of the first and second tab members are substantially perpendicular.
Additional tab members are similarly formed to create a zig-zag-shaped
series of tab members extending generally between the inlet and outlet of
the panel.
A similar series of tab members is formed in staggered spaced parallel
relationship with the first set of tab members to form a zig-zag-shape or
sinuous air passageway extending between the inlet and outlet of the
panel. Additional parallel air passageways may be formed in a similar
manner, as required, by merely forming additional series of adjacent tab
members.
A substantially flat rectangular plate-like sheet of solar radiation
absorptive material may be positioned beneath the panel containing the
upstanding tab members to block or cover the rectangular-shaped openings
formed by the upstanding tab members. The entire unit may be positioned
within a box-like enclosure and covered with a solar radiation
transmissive sheet to form the completed solar collector, as it is well
understood in the art.
It will be observed that this method of manufacture eliminates the separate
fabrication steps required by conventional solar radiation absorbing
panels where individual sinuously-snaped continuous fins must be
individually attached by welding, soldering or other means to the
underlying base sheet. In the present invention, the upstanding tab
members may be rapidly and easily formed by a single stamping and bending
operation, or by consecutive stamping and bending operations.
Further features of the invention will become apparent from the detailed
description which follows:
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a solar collector utilizing the solar
radiation absorbing panel of the present invention.
FIG. 2 is a top elevation view of a partially completed panel of the
present invention.
FIG. 3 is a fragmentary cross sectional view taken along section line 3--3
of FIG. 2.
FIG. 4 is a fragmentary cross sectional view taken through the panel of the
present invention illustrating angularly disposed tab members.
FIG. 5 is another embodiment illustrating an alternate tab member
configuration.
FIG. 6 is a top plan view of another embodiment illustrating an alternate
tab member configuration.
FIG. 7 is a top plan view of another embodiment illustrating an alternate
tab member configuration.
FIG. 8 is a top plan view of another embodiment illustrating an alternate
tab member configuration.
FIG. 9 is a top plan view of another embodiment illustrating an alternate
tab member configuration.
DETAILED DESCRIPTION
The solar radiation absorbing panel of the present invention, shown
generally at 1, is illustrated in FIG. 1 in connection with a typical flat
plate solar collector shown generally at 2. As is well known in the art,
such flat-plate solar collectors generally include a box-like housing 3
having spaced parallel side walls 4 and spaced parallel end walls 5 and 6.
End wall 5 generally forms a fluid inlet for admitting a working fluid,
such as air, water or the like, into collector 2 in the direction
illustrated by directional arrow 7. Similarly, end wall 6 forms an outlet
for exhausting heated working fluid from the collector. A sheet 8 of solar
radiation transmissive material such as glass, plastic or the like, is
positioned on the upper surface of collector 2 overlying panel 1 to admit
solar radiation into the collector.
In the embodiment of the invention illustrated in FIG. 1-FIG. 3, panel 1
comprises a substantially flat plate-like base sheet 9 having a
substantially planar upper surface 10 bounded by spaced side edges 11 and
12, and spaced end edges 13 and 14. End edge 13 forms the fluid inlet end
of panel 1 as illustrated diagrammatically by direction arrow 7a, while
end edge 14 forms the fluid outlet end of panel 1. In the preferred
embodiment illustrated, base sheet 9 may be rectangular in shape, and
constructed of a solar radiation absorptive material such as aluminum,
steel or the like, and may also be provided with solar radiation
absorption enhancing coating as will be described in more detail
hereinafter. It is preferred that relatively light gauge material be
utilized for panel 1 in order to provide faster response to direct or
diffuse sunlight, and consequently higher heat absorption, especially on
cloudy days.
Panel 1 is provided with means projecting away from surface 10 of base
sheet 9 for forming one or more fluid passageways for directing fluid from
inlet edge 13 to outlet edge 14. These means include a plurality of
individual rectangular tab members 15 extending perpendicularly away from
surface 10 of base sheet 9. In a preferred embodiment, tab members 15 are
of substantially the same size and shape, and dimensioned to extend from
surface 10 of base sheet 9 to slightly beneath the lower surface of
collector cover 8. This construction limits the amount of fluid passing
between the upper edges of tab members 15 and the lower surface of the
cover, and restricts the flow of fluid through collector 2 to the fluid
passageways formed between the sinuous-shaped series of tab members 15
placed in end-to-end relationship.
As best shown in FIG. 1, each tab member includes a pair of substantially
vertical spaced edges 15a and 15b, extending away from the upper surface
10 of base sheet 9. The panel further includes a first series of tab
members, shown generally at 16, consisting of a plurality of individual
tab members 15 arranged in end-to-end relationship, which extends
generally between inlet edge 13 and outlet edge 14 of panel 1. In other
words, the individual tab members 14 are arranged to form the
sinuously-shaped series of tab members by positioning the tab members
perpendicularly to each other such that adjacent vertical edges are
substantially parallel but not contiguous, thereby forming a zig-zag-shape
of adjoining tab elements extending between the inlet and outlet of
collector 2. A second series of tab members 17 is similarly formed by
individual tab members 15 arranged in end-to-end relationship, such that
the spacing between the first series of tab members 16 and the second
series of tab members 17 is substantially constant, with the space between
the parallel series of tab members forming a fluid passageway extending
between the collector inlet and outlet. If desired, a third series of tab
members 18 may also be formed of individual tab members 15 placed in
end-to-end realtionship, with the third series being positioned in spaced
relationship with the second series of tab members 17, thereby forming
spaced parallel fluid passageways formed by the spaced parallel
sinuously-shaped series of tab members.
It will be observed in this arrangement that each tab member 15 is arranged
at an angle of approximately 45.degree. with respect to inlet edge 13, and
is oriented generally to lie along a line extending between inlet edge 13
and outlet edge 14, or in other words along a line extending between inlet
edge 13 and one or the other of side edges 11 or 12. It will further be
observed that the opposing tab elements 15 of each series are arranged in
staggered relationship by approximately one half their length. In other
words, a tab element 15 begins at approximately the midpoint of the
opposing tab element.
As best shown in FIG. 3, tab members 15 are substantially perpendicular to
the upper surface 10 of base sheet 9. However, it is also considered to be
within the scope of the present invention to angularly dispose tab members
15 with respect to surface 10 of base sheet 9 as illustrated in FIG. 4. In
either event, the tab members provide additional collector surface area
for collecting solar radiation reflected within the collector and prevent
reflection of solar radiation through the collector cover, as well as act
as turbulators to introduce turbulance into the fluid stream passing among
the tab members to effectively remove heat from the tab members or surface
10 of base sheet 9. It will also be observed that the series of tab
members may be arranged in different configurations to impart various
types of flow patterns to the fluid passing through the collector. For
example, in the embodiment of FIG. 5, the individual tab members 15 are
arranged in end-to-end relationship to form a first sinuously shaped
series of tab elements 16 in the manner described hereinabove. There is
also provided a second series 19 of individual tab members 15 arranged in
end-to-end relationship, with adjacent tab members being perpendicular to
each other, such that series 19 is positioned in opposing relationship so
that the spacing between the first and second series of tab members is
non-constant. In other words, opposing tab elements 15 are substantially
perpendicular to each other so that the spacing between these tab members
varies from a maximum as the inlet edge 13 of panel 9 to a minimum at
outlet edge 14 of panel 9. In this arrangement, as in the embodiment of
FIG. 1-FIG. 3, adjacent tab members of each series are perpendicular to
each other and non-contiguous, with the tab members being perpendicular to
the base sheet 9 and arranged at angles of approximately 45.degree. with
respect to inlet edge 13.
If desired, a third series 20 of individual tab members 15 arranged in
end-to-end relationship may be positioned in spaced relationship with
second series 19 to form another air passageway between the
sinuously-shaped series of tab members. In the embodiment of FIG. 5,
series 20 is positioned such that the spacing between series 19 and 20 is
non-constant. Additional series of tab elements may be added as required
to form the necessary number of fluid passageways.
Another arrangement is illustrated in FIG. 6, where the sinuously shaped
series 21 and 22 of adjoining individual tab elements 15 are of
substantially constant spacing, and the outermost sinuously shaped series
23 and 24 of individual adjoining tab members 15 are arranged in constant
spaced relationship. However, series 22 and 23 are so arranged that the
spacing between these tab elements is non-constant, thereby forming three
non-parallel fluid passageways extending between the inlet and outlet of
the panel.
A further embodiment is illustrated in FIG. 7 where the outermost adjacent
series 25 and 26, and 27 and 28, respectively, are arranged in
non-constant spaced relationship, while the innermost adjoining series 26
and 27 are positioned in constant spaced relationship, thereby forming
three non-parallel fluid passageways extending between the inlet and
outlet of the panel.
In the embodiment of FIG. 8, all of the tab members 15 are parallel to each
other and formed in four parallel series 29-32 of adjoining tab members to
form three parallel spaced fluid passageways extending between the inlet
and outlet of the panel. It will be observed that this arrangement lacks
the sinuous shape of the previous embodiments, and may be used in
constructions where minimal impedence to fluid flow is desired.
Finally, in the embodiment of FIG. 9, the individual tab members 15 are
arranged randomly to provide a plurality of randomly positioned air
passageways among the tab members.
As described above, solar radiation absorbing panels are known which
require that continuously constructed vertically positioned fins be
separately attached to the underlying base sheet in one or more separate
fabrication steps to complete the panel. However, the solar radiation
absorbing panel 1 of the present invention is constructed in such a way as
to eliminate the separate fabrication steps required by conventional solar
radiation absorbing panels.
In the present invention, the substantially flat plate-like base sheet 9 is
severed along a plurality of C-shaped non-contiguous continuous lines 30
as illustrated in FIG. 2, leaving a portion 31 of the base sheet attached
between the ends of each of the lines of severence 30 to form a fold or
bend line. If desired, the fold line 31 may be scored or grooved to
facilitate bending of the tab member. Each attached portion is then bent
away from surface 10 of sheet 9 to form the plurality of upstanding
rectangular-shaped tab members 15 and openings 32 of substantially the
same size and shape as the tab members. It will be understood that members
of different shapes such as semicircular, square, trapezoidal, etc., may
be formed by properly arranged severence and bend lines. Furthermore, it
will be observed that the tab members 15 may be rapidly and easily formed
in this manner by a single stamping and bending operation where the tab
members are formed simultaneously, or by separate or consecutive stamping
and bending operations where some of the tab members are formed at one
time and some of the tab members are formed at a different time.
As observed above, tab members 15 may be bent perpendicularly to surface 10
of sheet 9 as illustrated in FIG. 3, or may be bent to form angular
relationships with the base sheet surface. It will be observed that this
method of fabrication produces tab members 15 and openings 32 which are
non-contiguous, thereby furnishing connecting areas or lands 33 between
adjacent openings and tab members, as shown in FIG. 2. In order to provide
sufficient structural rigidity to panel 1, it is preferred that the lands
33 between adjacent openings 32 and between adjacent tab members 15 is at
least one eighth of the shortest dimension of the tab member or opening.
In order to enhance the absorptivity of panel 1, the surface 10, as well as
the surfaces of tab members 15 may be provided with a coating 34 of black
paint or other solar radiation absorption enhancing material.
In a preferred embodiment, means are provided in the form of a
substantially flat plate-like support sheet 35 underlying base sheet 9 to
cover openings 32 and prevent fluid flow therethrough. In addition, the
portions of support sheet 35 coextensive with openings 32 may be provided
with a solar radiation absorption enhancing coating 36 the same or
different from coating 34. Alternatively, base sheet 9 or support sheet
35, or both, may themselves by constructed of a solar radiation absorbing
material.
It will be understood that various changes in the details, materials, steps
and arrangements of parts, which have been described and illustrated in
order to explain the nature of the invention, may be made by those skilled
in the art within the principle and scope of the invention as expressed in
the appended claims.
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