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Description  |
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BACKGROUND OF THE INVENTION
The invention relates generally to heat exchangers and more particularly to
solar heat absorber units for heating by solar heat energy a fluid
circulated through the units.
Diverse structures have been proposed and used in the past for the purpose
of heating a fluid, preferably a liquid fluid such as water, by way of
exposure of the structure to sun rays while the liquid is circulated
through the structure from an inlet manifold or header to an outlet
manifold or header, the liquid being progressively heated in the course of
its flow progression from one header to the other. Examples of prior art
methods and apparatus are disclosed in U.S. Pat. Nos. 679,451, 1,250,260,
2,358,476, 2,553,302, 3,076,450, 3,077,190, 3,145,707, 3,190,816,
3,387,602, 3,239,000, 3,273,227, 3,980,071, and Australian Patent
specifications Nos. 53,407 and 257,425.
Many inconveniences are present in prior art devices, which are due to many
reasons, such as the type of materials used for making the solar heat
absorber unit, the small volume of liquid flowing through the unit, the
complication of many designs, the difficulty of manufacturing and the
resultant high cost of production, to name a few. Solar energy absorbers
most practical under the present state of the art, as far as relative
simplicity of structure and relatively low cost, seem to belong generally
to two types. The first type takes the form of a plurality of parallel,
spaced apart metallic tubes interconnecting an inlet header to an outlet
header, soldered or welded to a heat absorbing flat or corrugated panel
made of thin metallic sheet or foil. The second type of solar energy
absorber panels generally used today are based on a structure, as
disclosed in U.S. Pat. No. 3,273,227, made of a pair of superimposed
metallic sheets provided at their adjoining areas with a pattern of weld
inhibiting material coating, welded together at the areas not provided
with the welding inhibiting material, and subsequently inflated under
pressure along the unwelded areas to form interconnecting tubular
portions. Such structures have in common the disadvantage that the area of
the absorber panel through which the liquid is caused to flow, or wetted
area, is a relatively small portion of the total area of the panel, with
the result that the efficiency, or BTU capability per area unit of such
panels, is relatively poor.
SUMMARY OF THE INVENTION
The present invention provides a structure for solar energy absorber panels
which results into an almost 100% wetted" area, which permits a high
liquid flow rate through a plurality of elongated flat tubular members
disposed across the panel from the inlet manifold or cold header to the
outlet manifold or hot header supplying heated liquid fluid. The present
invention accomplishes its objects and results by way of a relatively
simple structure utilizing components readily available on the market, and
therefore requiring no special method of manufacture, no expensive tooling
or fixtures, and requiring only a very small assortment of diverse
identical components. The diverse objects and advantages of the present
invention will become apparent to those skilled in the art when the
following description of some of the best modes contemplated for
practicing the invention is read in conjunction with the accompanying
drawing wherein like reference numerals refer to like or equivalent parts
and in which:
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic perspective view of a solar energy absorber panel
according to the present invention;
FIG. 2 is a partial transverse section along line 2--2 of FIG. 1;
FIG. 3 is a longitudinal section as seen from line 3--3 of FIG. 1;
FIG. 4 is a schematic perspective exploded view of the structure of FIGS.
1-3;
FIG. 5 is a schematic plan view showing a plurality of solar energy
absorber panels according to the present invention interconnected in an
array providing increased capacity;
FIG. 6 is an example of a header assembly forming part of the solar energy
absorber panel according to the present invention, shown in perspective
exploded view;
FIG. 7 is a view similar to FIG. 6 but showing another example of structure
for a header assembly;
FIGS. 8 and 9 are respectively a partial perspective view and a plan view
of an absorber panel provided with the header assemblies of either FIG. 6
or FIG. 7;
FIG. 10 is an exploded perspective view of another example of header
assembly according to the present invention; and
FIG. 11 is a partial perspective view of an absorber panel according to the
present invention utilizing the header assembly of FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, and more particularly to FIGS. 1-4, a solar
energy absorber panel 10 for solar heat collector array comprises
essentially a plurality of flat tubular members 12 disposed parallel to
each other and adjoining one another. Each of the flat tubular members 12,
as best shown at FIG. 2, has a pair of opposite, parallel, substantially
flat, wide sidewalls 14 and a pair of opposite relatively narrow
curvilinear sidewalls 16. The flat tubular members 12 are disposed side by
side with each curvilinear sidewall 16 of a tubular member 12 adjoining
and touching the corresponding curvilinear sidewall 16 of the adjacent
tubular members. The flat tubular members 12 are disposed such that their
wide sidewalls 14 disposed on each side of the panel 10 are substantially
coplanar, so as to present a large area adapted to be impinged upon by the
sun rays when a panel 10 is installed at an appropriate location to act as
an absorber and collector of solar heat. The tubular members 12 are
collectively fitted at each of their open ends through a slot 18, FIG.
3-4, formed longitudinally through the wall of a manifold or header 20 in
the form of a metallic tube or pipe. Each header 20 is open at both ends
as shown at 22. The flat tubular members are soldered to the outer surface
and also preferably to the inner surface of the wall of the header 20, at
the edge of the slot 18, where they project at their ends through the slot
18, as shown at 24 at FIGS. 1-3. One, or more, cross-member 12',
preferably made of a length of the same flat tube as the tubular members
12, extends laterally on one side of the panel 10 and is soldered, as
shown at 24', to the exterior surface of the sidewalls 14 of the tubular
members 12, such as to increase the rigidity of the assembled panel 10.
The cylindrical tubular members forming the headers 20 are preferably
lengths of readily available copper or stainless steel tubing, and the
flat tubular members 12 are preferably made of equal lengths of copper or
stainless steel seamless or seamed flat tubing, also readily available at
relatively low cost in the market. Soldering of the ends of the flat
tubular members 12 to the headers 20 may be effected manually,
automatically or by dipping. If it is desired to enlarge the cross area of
each tubular member 12 for the passage of liquid from one header 20 to the
other, the tubular members 12 may be conveniently expanded by plugging the
two open ends 22 of one header 20 and one open end 22 of the other header,
and applying pressure through the header remaining open end, for example
up to 130-150 psi, which results in expanding slightly the thin walled
tubular members 12 and in testing under pressure the structural integrity
of the assembly, including the soldering of the tubular members 12 into
the headers 20.
The absorber panel 10 thus forms an integral unit made of a plurality of
adjacent juxtaposed thin walled flat tubular members 12 interconnected at
their ends by the headers 20 such as to present a large "wetted" area
exposed to solar heat energy and amounting, for all practical purposes, to
the sum of the areas of the wide flat sidewalls 14 and of a portion of the
curvilinear sidewalls 16 of the tubular members 12. The exposed surface of
the panel 10 is preferably provided with a dark heat-absorbing layer or
coating.
The absorber panels 10 according to the present invention which are
individually, for all practical purposes, full flow high efficiency heat
collector and transfer units, may be interconnected, for a large liquid
flow rate, in parallel as illustrated at FIG. 5. A collector array may
thus be formed by disposing a plurality of absorber panels 10 side by side
and interconnecting in series all the headers 20 at each end by means of
flexible couplings 26 held in position by circular clamps 28. One of the
resulting common headers, for example the lower common header as seen at
FIG. 5, is connected to an inlet for cold water, for example, and the
other common header, for example the upper line of headers 20 as seen in
FIG. 5, is connected to a hot water utilization unit, such as a hot water
heating system for a building, a heat exchanger disposed in a swimming
pool or in the water circulation and filtration system of the swimming
pool, to a hot water main supply for a building, or the like.
Single absorber collector units, such as illustrated at FIG. 9, are made by
providing each slotted header 20, FIG. 6, with a plug 30 provided with a
solid end wall 32 fitted over one open end 22, and with a connector 34
provided with a short length of pipe 36 fitted over the other open end 22,
both soldered or brazed in position, as illustrated at FIG. 8, such that
the complete assembly, FIG. 9, provides an absorber unit 10 having an
inlet consisting of one of the pipes 36 connected through the
corresponding header 20 to the opposite header outlet pipe 36 via the
plurality of heat collecting flat tubular members 12. Several such
absorber units 10, as shown at FIG. 9, can be connected to form a
collector array, with the individual absorber units connected in series,
in parallel, or in series-parallel according to the requirements for
heated fluid.
Instead of utilizing a length of pipe to form the headers 20, which require
machining the slot 18 conventionally by a milling operation, the slot may
be made so as to extend from one open end 22 to the other open end 22 of a
length of pipe such as to form a continuous slot 38 as illustrated at
FIGS. 7 and 10. The continuous slot 38 may be cut by a saw, such as a
circular high speed steel or carbide saw, or, preferably, a length of
tubing or pipe, from which the headers 20 are cut, may be made by means of
the conventional pipe roll forming machinery used for making welded-seam
pipes, after adjusting the operation of the pipe forming rolls such that
instead of providing for longitudinally abutting rolled sidewalls at the
lateral welded seam, the longitudinal edges 40 and 42 of the sidewall
remain spaced apart, as illustrated. Once the ends of the tubular members
12 are introduced into the slot 38, the plug 30 is fastened over one open
end 22 of the header 20 and the other open end 22 of the header is
provided with the tubular fitting 34, and after the diverse elements have
been soldered in position, there is no practical difference between the
alternative structures, whether the slot 18 is machined through the wall
of a length of pipe, FIG. 6, or whether the slot is a continuous slot 38,
FIG. 7.
When the headers 20 are provided with the continuous slot 38 for soldered
assembly therein of the ends of the flat tubular members 12, the ends of
the slot 38 proximate the open ends 22 of the header may be closed by
filling with solder or, alternatively and as shown at FIGS. 10-11, they
may be provided with short lengths 44 of a larger diameter pipe soldered
over the ends of the header. The resulting absorber panel unit is similar
in structure and operation to the absorber units 10 of FIGS. 1-4, and is
adapted for interconnection with other identical absorber units into an
array as illustrated at FIG. 5.
It will be appreciated that brazing or welding may be used for assembling
the absorber units of the invention, and that elements made of molded or
extruded plastic resins may be substituted for all the elements forming
the absorber units. However, it will be readily apparent that a metallic
structure is preferable, especially for the heat collecting portion of the
panels, namely the flat thin walled tubular members 12, and that
substantial mismatch of the coefficients of expansion of the materials
utilized for making the components should be avoided.
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