AU1479883A - Solar heating device - Google Patents

Description

SOLAR HEATING DEVICE

Field and Background of Invention This invention relates to solar heating devices and more particularly to a solar heating device wherein a flexible-walled container of reinforced thermoplastic material serves as a solar fluid heater. All solar heating devices that are known to be commercially available have a solar fluid heater formed of rigid pipes. Most commonly, the pipes are formed of copper to reduce corrosion and to better withstand various weather conditions in environments where solar heating devices are utilized. Under certain environmental conditions, rigid plastic pipes have been utilized in lieu of copper. However, it is recognized that such plastic pipes are not suitable in areas where there is intense sunlight and attendant high heat generated within the solar heating system. In this regard, it is known that, with a transparent cover overlying a solar fluid heater, the trapped heat between the cover and the solar fluid heater can be so high that the plastic pipes tend to soften and lose their s hape and cause leakage of fluid from the system.

Brief Description of Invention

With the foregoing in mind, It is the primary object of this invention to provide a solar fluid heater for use with a variety of different types of solar heating devices and which Is constructed of extremely lightweight reinforced thermoplastic material and yet exhibits very high tensile strength for readily being utilized in any environment wherein prior art devices have been utilized and irrespective of how extreme the temperature conditions might be. It Is an object of this invention to provide a solar fluid heater having a fIexibIe-waIIed container formed by opposing sheets of material bonded together to define a fluid flow passageway through the container and with an inlet and an outlet for a fluid to be heated to flow Into and out of said container, the heater being characterized in that said sheets are of fluoroplastic material, and further in that a reinforcing fabric is intimately bonded to each sheet to lend strength and dimensional stability thereto. It is a further object of this invention to provide a solar fluid heater wherein the cost of constructing the same including the materials thereof are only a small fraction of those solar fluid heaters formed of rigid piping material. Thus, it is contemplated that this invention would be an impetus for more widespread use of solar heating devices.

It is a more specific object of this invention to provide a solar fluid heater of flexible-walled construction and wherein the fluid heater is formed of fabric reinforced sheets of fluoroplastic material such as poIytetrafIuoroethyIene (such as is known under the trademark Teflon) fusibiy bonded together to provide fluid flow passages therebetween. Fluoroplastic materials are known to be unaffected by outdoor weathering and to have almost complete chemical inertness. Further, such fluoroplastic materials are known to be the slipperiest of all solids which is desirable in a solar fluid heater to provide low resistance to flow of fluid through the passages thereof.

It is a further more specific object of this invention to provide a solar heating device having an open top receptacle, substantially rigid thermal insulating means positioned in the bottom of the receptacle, and a flexible-walled container serving as a solar fluid heater and positioned to overlie and rest on the thermal insulation means. The walls of the fluid heater are formed of fabric reinforced sheets of fluoroplastic material fusibiy bonded together to define fluid flow passageways, and a transparent cover is positioned to overlie the fluid flow heater and serve as a top enclosure cover for the heating device and to also define a solar heating chamber overlying the solar fluid heater.

Brief Description of Drawings Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompanying drawings, in which:

Figure 1 is a perspective view of a preferred embodiment of the solar heating device of the present i nvent i on ;

Figure 2 is a partially exploded perspective view of the solar heating device;

Figure 3 Is a perspective view of a flexible-walled container removed from the open top receptacle of the solar heating device;

Figure 4 is an enlarged fragmentary view of one corner portion of the flexible-walled container of the area identified by the numeral 4 in Figure 3; Figure 5 is a greatly enlarged fragmentary view of the flexible material forming each wall of the container, taken from the area identified by the numeral 5 in Figure 4;

Figure 6 is a further enlarged fragmentary sectional view through one embodiment of the sheet of thermoplastic material of which a flexible wall of the container may be formed, and being taken substantially along the line 6-6 in Figure 5;

Figure 7 is an enlarged fragmentary sectional view, taken along line 7-7 In Figure 3, through the fIexibIe-walled container and illustrating one of the fluid flow passages or channels defined therein by fusibiy bonding the walls together;

Figure 8 is a sectional view similar to Figure 7, but showing a modified embodiment of the construction of the sheet of thermoplastic material of which the flexible walls of the container may be formed;

Figure 9 Is an enlarged longitudinal vertical sectional view through the solar heating device, with portions broken away, taken substantially along the line 9-9 i n Fi g u re 1 ;

Figure 10 is a further enlarged fragmentary view of the left hand end portion of Figure 9; and

Figure 11 is an enlarged, partially exploded view similar to the left hand portion of Figure 2, but

Illustrating how the fluid inlet for the container Is arranged relative to the other components of the solar heating device.

Detailed Description of the Invention While the present Invention will be described more fuIIy hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the present invention is shown, it is to be understood at the outset of the description which follows that persons of skill in the appropriate arts may modify the invention here described while still achieving the favorable results of this invention. Accordingly, the description which follows is to be understood as being a broad, teaching disclosure directed to persons of skill in the appropriate arts, and not as limiting upon the present invention.

Referring now more speclfϊcaly to the drawings, the solar heating device of this invention comprises an open top receptacle or tray 20 (Figures 1, 2, 9, 10, and

11) preferably formed of a relatively thin material of plastic or aluminum and which may be generally rectangular in plan, and on the bottom of which a thermal insulating means 21, such as a panel or layer of relatively rigid expanded foam, is positioned. A solar heater, In the form of a fIexibIe-waIled container or envelope for a fluid, overlies and rests upon the thermal insulating means 21 and is provided with an inlet a and an outlet b for a fluid to be solar heated to flow into and out of the flexible-walled container 22. As will later be described in more detail, the container 22 is constructed to provide means defining fluid flow passages or channels c therein communicatively connecting the inlet a and outlet b for the flow therethrough of a fluid to be solar heated. Accordingly, respective nipple means or couplings d, e are connected to the inlet a and outlet b and extend downwardly through the thermal Insulating means 21 and the receptacle 20 so as to be readily accessible from the exterior of the receptacle 20 for facilitating the connection thereto of tubing a', b' for fluid flow therethrough.

Transparent cover means 23 Is spaced above and overlies the fIexibIe-waIIed container 22 so as to define, with side and end walls 20a of the receptacle 20, a solar heating chamber 24 (Figures 9 and 10) overlying the flexible-walled container 22. In this regard, it is apparent that the upper wall of the container 22 defines the bottom of the solar heating chamber 24. The transparent cover means 23 may take the form of one or more panels of transparent material, such as glass or plastic, through which the rays of the sun will readily penetrate for heating the chamber 24, the container 22, and the fluid flowing In the passages of the container.

As best illustrated in Figures 9 and 10, the transparent cover means 23 there shown comprises a pair of superposed, planar, upper and lower transparent panels 23a, 23b which may rest upon respective peripheral shoulder means 20b, 20c formed in or otherwise provided on the upper portions of the side and end walls 20a of the receptacle 20. The shoulder means 20b, 20c may be arranged in a stepwise manner so as to facilitate installation and removal of the panels 23a, 23b with respect to the receptacle 20. The shoulder means 20b, 20c are vertically spaced apart so as to maintain the transparent panels 23a, 23b in spaced relationship for defining a shallow thermal insulating air space therebetween to minimize loss of solar heat from chamber 24 through panels 23a, 23b to the ambient atmosphere.

The upper and lower walls of the flexible-walled container 22 are designated at 22a, 22b and are formed of respective relatively thin sheets of reinforced thermoplastic material joined together, preferably by being fusibiy bonded as at 22c, to define the aforementioned fluid flow passages c therebetween. As s hown i n F ig ures 1 through 3, the container walls or reinforced sheets 22a, 22b of thermoplastic material are fusibiy bonded together along a series of substantially parallel and relatively narrow transverse lines preferably arranged so that the fluid flow passages c. defined thereby collectively define a sinuous fluid flow passageway extending from end-to-end of the flexible-walled container 22. Fusible bonding may be accomplished, for example, by applying heat and pressure. The characteristics of the sheets or walls 22a, 22b as described hereinafter contribute important strength to such bonding.

Desirably, the thermoplastic material of which the opposing sheets or walls 22a, 22b are made is a fluoroplastic material, preferably poIytetrafIuoroethyIene or polychIortrϊfIuoroethylene, and which maintains flexibility over a temperature range which is far broader than other materials, is substantially unaffected by exposure to outside weather, and has almost complete chemical Inertness. Further, fIuoroplastics are the slipperiest of all solids to reduce the coefficient of friction of the flow of fluid through the fluid flow passages c. Also, it is desirable that the reinforced flexible sheets 22a, 22b of the container 22 be thin, i.e., within the range of from about 3 mils to about 6 mils thick, and no more than 20 mils thick. It has been determined that a number of very important advantages are obtained by using thin sheets within the 3 mils to 6 mils thickness range. For example, the flexibility of the sheets is such as to facilitate handling for rolling up the sheets Into a compact package for shipment. Further, the thin sheets permit higher heat transfer therethrough from the fluid flowing within the channels of the container to thus enhance the overall effeciency of the solar device. Additional advantages have appeared in the manufacturing of the container in that less costly sheets of material are involved and less time is taken to effect fusion bonding of the sheets for forming the container since a quicker heat transfer Is effected through thinner material.

In order to lend strength and dimensional stability to each sheet 22a, 22b of thermoplastic material while In use, and to also aid in maintaining the integrity and stability of the sheet material so as to prevent "creep" during manufacture of the flexible-walled containers 22 by the use of production machinery and during which the thermoplastic material is taut or placed under substantial tension and compression during bonding, in accordance with this Invention each sheet 22a, 22b comprises a reinforcing fabric which is Intimately bonded to or embedded in the thermoplastic material. The reinforced sheet may be formed by the reinforcing fabric being coated with the thermoplastic material as by well known vaporization/condensation techniques for fluoroplastic types of thermoplastic. By way of illustration, portions of a flexible wall of the container 22. are shown in Figures 5 and 6 wherein the reinforcing fabric is indicated at f and the thermoplastic material Is Indicated at g. There it will be observed that the reinforcing fabric f comprises a sheet of woven fibers or strands, preferably glass or aramϊd fibers for high tensile strength, which are embedded in or coated with the thermoplastic material g. As a suitable example, it has been determined that a 3 mil thick glass fiber reinforced fluoroplastic sheet of one inch width had a tensile strength of 70 pounds.

As earlier indicated, there are a number of reasons including economy, ease of handling, and flexibility, for having the reinforced sheets 22a, 22b formed of thin material preferably within the range of from 3 mils to 6 mils thick. With such thin material, it is important that zero moisture absorption be present to provide a fluid tight non-leaking container. Tests have indicated that more than 40% of the overall weight of such sheets, and preferably about 60% of the weight of the sheets, should be thermoplastic material. In this regard, tests have indicated that reinforced sheets of 3 mils thickness having 40% thermoplastic material would not provide a suitable container since there was insufficient thermoplastic material to effect a fusible bond and provide zero water absorption in the reinforced sheet material.

The woven reinforcing fabric f has been described above as being embedded within the thermoplastic material g. with reference to Figures 5 and 6 and as further illustrated in Figure 7. Since it is contemplated that the reinforcing fabric need not be embedded in the thermoplastic material, in the modification of Figure 8 it will be observed that the thermoplastic material g' Is bonded to one side of the fabric f ' . As illustrated, the thermoplastic material g' is bonded to the inner side of the reinforcing fabric f ' with the reinforcing fabric f ' thus being exposed exteriorly of the container 22'. Desirably, a heat absorbing coating h is aplied to the exposed reinforcing fabric to Increase the heat absorption from sunlight. In other respects, the modified form of the reinforced fabric in Figure 8 may be of the same construction as that shown In Figures 5, 6, and 8. Accordingly, a further description of the reinforced sheet of material shown in Figure 7 is deemed unnecessary.

As hereinbefore described, nipple means d, e are connected to the inlet a and outlet b for the flow of fluid into, through and out of the passages c in the container 22. To this end, each nipple means d, e is positioned adjacent a respective inlet a and outlet b . Since both nipple means d, e may be mounted in essentially the same manner, only the arangement at the nipple means d will be described in detail.

Accordingly, as shown in Figures 4, 9, 10 and 11, the stem or shank of nipple means d penetrates the lower flexible wall 22b of the container 22 and has a flange h on its upper end which Is fusibiy bonded in sealing engagement with the lower flexible wall 22b of the container 22. To shieldlngly protect and to anchor the nipple means d, the bottom of the receptacle 20 has an inverted substantially cupshaped portion projecting upwardly therefrom and terminating substantially flush with the upper surface of the thermal Insulation means 21 upon which rests the bottom wall 22b of the container 22.

The insulation means 21 has suitable openings 21a therethrough for accomodating the respective inverted cupshaped portions 20d on the bottom of the receptacle 20. Thus, it can be seen in Figure 10 that the nipple means d communicates with the interior of the flexible-walled container 22 at the fluid inlet a and extends downwardly through the thermal Insulating means 21 so as to be readily accessible from the exterior of the receptacle 20. Also, the receptacle 20 and the Insulating means 21 have cooperating side passages 20e, 21b (Figure 11) opening to the adjacent side or end wall 20a of the receptacle 20 and communicating with the respective inverted cupshaped portion 20d and opening 21a, respectively, so that the tubing a', b' in each instance, may extend laterally outwardly through the latter side passages without projecting below the bottom of the receptacle 20. It Is apparent that the side passage 21b in the Insulation accomodates the side passage 20e of the receptacle therethrough when the thermal insulation means 21 is positioned upon the bottom of the receptacle 20.

In order to connect the various components together, upper and lower surfaces of the thermal Insulation means 21 are provided with adhesive. The adhesive on the lower surface of the insulation means connects the same to the receptacle 20, while the adhesive on the upper surface connects the insulation means to the bottom wall of the flexible-walled container 22. Normally the adhesive used for connecting the thermal insulation means to the bottom wall of the flexible-walled container will differ from the adhesive used for connecting the thermal insulation means to the receptacle. In this regard, and as well recognized by those versed In fluoroplastic materials, It is extremely difficult to effect an adhesive bond thereto. Typically, and as is contemplated by this invention, the reinforced fluoroplastic sheet forming the bottom wall of the container 22 wil be etched or chemically treated by known techniques before adhesive is applied.

If deemed desirable, carbon black, black chrome or some other darkening material may be incorporated in either the upper or lower or both of the fluoroplastic sheets to increase the absorption of heat. If the reinforcing fabric is formed of aramid fibers instead of glass fibers, for example, then a darkening agent should be added to avoid the breakdown of the aramid fibers from exposure to sunlight.

In the drawings and specifications there has been set forth a preferred embodiment of the invention and, although specific terms are used, the description thus given uses terminology in a generic and descriptive sense only and not for purposes of limitation.

Claims (8)

That which is claimed is:

1. A solar fluid heater having a flexible-walled container formed by opposing sheets of material bonded together to define a fluid flow passageway through the container and with an inlet and an outlet for a fluid to be heated to flow Into and out of said container, the heater being characterized in that said sheets are of fluoroplastic material, and further in that a reinforcing fabric is intimately bonded to each sheet to lend strength and dimensional stability thereto.

2. A solar heater according to Claim 1 further characterized In that each of said sheets has a thickness in the range of from about 3 mils to about 20 mils.

3. A solar heater according to Claim 1 or Claim 2 further characterized in that said fluoroplastic material constitutes more than 40% by weight of said sheets.

4. A solar heater according to any preceding claim further characterized In that said fluoroplastic material is poIytetrafIuoroethyIene and said fabric is formed of fibers selected from the group consisting of glass fibers and aramid fibers.

5. A solar heater according to any preceding claim further characterized in that said sheets are fusibly bonded together, and further in that said fabric is embedded within each sheet of fluoroplastic material.

6. A solar heater according to any preceding claim further characterized in that an open top receptacle encloses said container, a body of thermal insulating material positioned in said receptacle underlies said container, and a transparent cover on said receptacle overlies said container in spaced relation thereto for defining therewith a solar heating chamber.

7. A solar heater according to Claim 6 further characterized in that a coating of heat absorbing material is present on the upper surface of the sheet of fluoroplastic material defining the upper wall of the container for enhancing the transfer of solar heat to the container and to a fluid flowing therethrough.

8. A solar heater according to any preceding claim further characterized In that said sheets have a thickness in the range of from 3 mils to 6 mils, and further that said fabric is woven of glass and embedded within said sheets, and further in that said fluoroplastic material comprises about 60% by weight of said sheets.