US20080000435A1

US20080000435A1 - Solar thermal tube plate heat exchanger

Info

Publication number: US20080000435A1
Application number: US11/756,434
Authority: US
Inventors: Stephen Baer; David Harrison; William Mingenbach
Original assignee: Zomeworks
Priority date: 2006-05-31
Filing date: 2007-05-31
Publication date: 2008-01-03

Abstract

A combination solar absorber and atmospheric radiator in multiple embodiments, a method for constructing these embodiments, and a method for using the combination solar absorber and atmospheric radiator, the absorber/radiator has a thermally conductive sheet which serves as a back plate, tubular fluid conduit or conduits, generally rectangular thermally conductive caps, and a means for fastening the caps to the sheet, covering one or more conduits and pressing them against the sheet. The side of the sheet with the caps and conduits is exposed to the sun and atmosphere, providing two thermal pathways to and from the conduit.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application No. 60/809,878, filed May 31, 2006, the teachings of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to solar thermal tube-plate heat exchangers.
The external surface of buildings receives solar energy. Most of the received solar energy is transferred passively to the building by heating up the walls, the roof and other exposed external surfaces of the building. Roofs and walls face the sky, protect against the sun, the cold and the rains, but roofs and walls make little use of the sun, the night's coolness or evaporative cooling. Some have taken advantage of the available solar energy by developing devices that actively harness the solar radiation. Solar flat-plate collectors are one example of such devices.
Flat plate thermal solar collectors have been developed to take advantage of the available solar radiation for heating purposes. Such collectors mostly include one or more fluid-filled tubes arranged on a heated plate. The tube-plate heat exchange surface is also usually placed in an enclosure. The enclosures have a clear glass, referred to as glazing, to allow solar radiation to reach the tube-plate arrangement within the collector's enclosure. While flat-plate collectors enjoy a rich history of use, they are none-the-less susceptible to certain shortcomings. One such shortcoming is the loss of solar energy due to losses of the incoming radiation to the glazing as well as other structures of the solar collectors. Another loss in efficiency in flat-plate collectors is due to the presence of sharp temperature gradients which afflict flat-plate collectors near the tubes. Another disadvantage of flat-plate collectors is that the tube-plate surface needs protection from wind and rain and other elements. As such flat-plate collectors have sturdy enclosures, which detract from their overall thermal efficiency and add to their mounting and fastening demands.
Therefore there still exists a need to more effectively harness the roofs and walls of buildings for heat exchange applications and also for a tube-plate type heat exchanger that can take advantage of the available solar energy while not suffering from the above-described shortcomings.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an apparatus having a generally flat thermally conductive sheet which serves as a back plate; tubular fluid conduit or conduits (rubber or plastic tubes or hoses, or metal pipes) generally as long as either the length or the width of the sheet, the tubular fluid conduit or conduits containing fluid (water or alternative fluid commonly used for such an apparatus, for example containing anti-freeze); and generally rectangular thermally conductive cap or caps, the cap or caps having lengths and widths appropriate for covering one or more of the tubular fluid conduit or conduits; and a means for fastening each cap to the sheet; the caps fastened to that side of the sheet which is exposed to the sun or atmosphere; thereby covering one or more of the tubular fluid conduit or conduits and pressing them against the sheet. The caps if used in plurality need not be contiguous to each other, but could be arranged on the sheet so as to leave space between them, exposing part of the sheet to the sun or atmosphere. The sheet and the cap or caps may be made of any metal such as copper or aluminum, as well as steel or any combination of these materials. For example, copper and/or aluminum caps may be used on a steel sheet. The tubular fluid conduit or conduits may be made of any heat resistant rubber such as santoprene, silicone or ethylene-propylene-diene monomer (epdm), or any heat resistant plastic such as polypropylene or polyethylene, or a metal such as copper or aluminum, or any combination of these materials. For example, both copper and santoprene tubular fluid conduit or conduits can be used on different parts of the embodiment of the apparatus.
In operation, the apparatus in accordance with one embodiment of the present invention is deployed by exposing to the sun or atmosphere the side of the sheet onto which the tubular fluid conduit or conduits are fastened by the cap or caps, providing two thermal pathways to and from the conduits. A first pathway is from the plate to the conduit, and a second pathway is from the cap to the conduit. As a solar absorber, any particular embodiment of the apparatus functions when solar energy heats the cap, the cap then conducts the heat to the portion of the tubular fluid conduit or conduits beneath the cap, where the heat warms the portion of the tubular fluid conduit or conduits beneath the cap, subsequently warming the fluid in the tubular fluid conduit or conduits; and when solar energy heats the exposed portion of the sheet, the sheet then conducts the heat to the area of the sheet underneath the tubular fluid conduit or conduits, where the heat warms the portion of the tubular fluid conduit or conduits adjacent to the sheet, subsequently warming the fluid in the tubular fluid conduit or conduits. As an atmospheric radiator, every embodiment of the apparatus functions when heat conducts from the fluid in the tubular fluid conduit or conduits to the portion of the tubular fluid conduit or conduits adjacent to the sheet and then to the unexposed portion of the sheet that is covered by the tubular fluid conduit or conduits and cap, the heat then migrating to the exposed portion of the sheet not covered by a cap, where the heat is then radiated to the atmosphere; and when heat conducts from the fluid in the tubular fluid conduit to that portion of the tubular fluid conduit or conduits adjacent to the cap and then to the cap, where the heat is then radiated to the atmosphere.
It is an unexpected advantage of the various embodiments of the apparatus that it is not necessary to use optimally thermally conductive materials for any particular embodiment of the apparatus to operate effectively. Fastening tubular fluid conduit or conduits and caps close together to a large area of a relatively poorly conductive sheet can often provide sufficient heat transfer to and from the sheet. By tightly enclosing the tubular fluid conduit or conduits and fastening them to the sheet, the contact of the tubular fluid conduit or conduits with the cap or caps and the sheet is optimized.
Although the apparatus in accordance with the embodiments of the present invention can collect or radiate the most heat from a given area of roof or wall, the demand may be less than what the building can supply. In many cases it is more economical to space the tubular fluid conduits far apart across the entire roof or wall than to place them close together on a part of it. Instead of investing in 1,000 feet of tubes or hoses or pipes which would then be spaced 6 inches apart across a roof or wall of 0.032 inch aluminum, it is more economical to use only 800 feet of tubes spaced 12 inches apart. Placement of tubular fluid conduit or conduits on metal roofs and walls is guided by getting the most energy with the least additional expense. The heat exchangers of radiator/absorbers that are described herein can use the roofs and walls of buildings and thus the investment in metal skin, back insulation and support structure has been made before using the roof or wall to give or take heat. The additional use of the wall or roof by adding metal caps, tubular fluid conduit or conduits and headers is much less expensive than the total cost of the usual solar absorbers or radiators.
The cap or caps provide numerous additional benefits to the embodiments of the apparatus. By mechanically constraining a tubular fluid conduit or conduits, they are prevented from runaway expansion if the fluid in them freezes, since a tubular fluid conduit is more prone to aneurysm if its radius has expanded; e.g., see U.S. Pat. No. 5,143,053 (Baer). Because the cap or caps can be fastened to the sheet with relative ease, such as by threaded fasteners, adhesives and epoxies, rivets, soldering, welding, nailing and snapping-on, the embodiments of the apparatus are very easy to construct or modify in the field as well as in the shop. The cap or caps improve the efficiency of the embodiments of the apparatus, for when the caps carry heat parallel to the plate below, they lessen the steep temperature gradient that afflicts other plate collectors near the tubular fluid conduit or conduits. It is not necessary for the cap or caps to be in thermal contact with the sheet; even without such thermal contact, a cap absorbs or dissipates heat that would otherwise have to be absorbed or dissipated by the area of the thermally conductive sheet in contact with the tubular fluid conduit or conduits.
A fastening means has been implemented by the cap or caps with C-shaped cross-sections transversely of the elongated direction, wherein the C-shaped cap or caps are snapped-on to ridges raised from or attached to the sheet. In addition to ease of attachment, the fastening means has the benefit in regard to heat transfer of approximating tapered fins even if the caps are not in thermal contact with the sheet. In embodiments where the ridges are not only raised or attached but also convex and undercut, upon fastening a C-shaped cap to the ridge, the ridge goes into compression, and the cap goes into tension and grips the ridge tighter.
Some of the benefits of using plastic or rubber tubes or hoses are that they are inexpensive, they readily conform to the cap or caps, and they can be rapidly cut to proper length on site. Polyethylene is inexpensive and thermally conductive. Because plastic and rubber tubes are sold in rolls of flat tube, they do not take up space at the work place. Rubber tubes in particular are freeze tolerant, but the tubular fluid conduit or conduits utilized generally do not need to be freeze tolerant. The inventors herein have found that the flexing of the metal or steel sheet and cap provides freeze protection where the metal is 26 gauge steel.
Some embodiments, such as those deployed on roofs, can avoid freezing, due to the drain back of the fluid; whenever a freeze threatens, the water drains out of the absorber and into storage.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front and side elevation view of an embodiment of the apparatus wherein the caps have outwardly curving flanges on the cross-section, which caps are attached by either screws or adhesive, and the side of the sheet on which the caps are attached is exposed to the sun.
FIG. 2A shows a front and side elevation view in detail of an embodiment of the apparatus using two different designs of caps, which are fastened to the sheet with screws or adhesive.
FIG. 2B shows a front and side elevation view in detail of the cross-section of an embodiment of the apparatus using two different designs of caps, both of which are fastened to the sheet with screws or adhesive.
FIG. 3A shows a side elevation view in detail of an embodiment of the apparatus using a cap having a single bend and outwardly curving flanges on the cross-section, fastened to a sheet using screws.
FIG. 3B shows a side elevation view in detail of an embodiment of the apparatus using a cap having a single bend and outwardly curving flanges on the cross-section, fastened to a sheet using adhesive.
FIG. 3C shows a side elevation view in detail of an embodiment of the apparatus using a cap having two bends and outwardly curving flanges on the cross-section, fastened to a sheet using screws.
FIG. 3D shows a side elevation view in detail of an embodiment of the apparatus using a cap having two bends and outwardly curving flanges on the cross-section, fastened to a sheet using adhesive.
FIG. 3E shows a side elevation view in detail of an embodiment of the apparatus using a cap having a C-shaped cross-section transversely of the elongated direction with inwardly curving flanges, fastened to a sheet having raised and undercut ridges.
FIG. 3F shows a side elevation view in detail of an embodiment of the apparatus using a cap having a C-shaped cross-section transversely of the elongated direction with inwardly curving flanges, fastened to a sheet having raised, undercut and convex ridges.
FIG. 3G shows a side elevation view in detail of an embodiment of the apparatus using a cap having two bends and inwardly curving flanges on the cross-section, fastened to a sheet having raised and undercut ridges.
FIG. 4A shows a front elevation view of a sheet having raised, undercut ridges.
FIG. 4B shows a side elevation view of a sheet having raised, undercut ridges.
FIG. 4C shows a front elevation view of a sheet having raised, undercut and convex ridges.
FIG. 4D shows a side elevation view of a sheet having raised, undercut and convex ridges.
FIG. 5A shows a front and side elevation view of an embodiment of the apparatus as an integral part of a roof.
FIG. 5B shows a side elevation view of an embodiment of the apparatus as an integral part of a roof.
FIG. 5C shows a front and side elevation view of an embodiment of the apparatus as an integral part of a roof wherein the headers are concealed in the eaves.
FIG. 6A shows a front and side elevation view of an embodiment of the apparatus deployed as a panel on a roof.
FIG. 6B shows a side elevation view of an embodiment of the apparatus deployed as a panel on a roof.
FIG. 7A shows a front and side elevation view of an embodiment of the apparatus as an integral part of a wall.
FIG. 7B shows a side elevation view of an embodiment of the apparatus as an integral part of a wall.
FIG. 7C shows a side elevation view of the hot and cold fluid lines as they enter the fluid reservoir.
FIG. 8A shows a front and side elevation view of an embodiment of the apparatus as a panel that is attached to a wall.
FIG. 8B shows a side elevation view of an embodiment of the apparatus as a panel that is attached to a wall.
FIG. 9A shows a front elevation view of an embodiment of the apparatus as a panel that does not need to lie on a roof or wall.
FIG. 9B shows a side elevation view of an embodiment of the apparatus as a panel that does not need to lie on a roof or wall.
FIG. 9C shows a front elevation view of an embodiment of the apparatus deployed horizontally in three short rows.
FIG. 9D shows a front elevation view of an embodiment of the apparatus deployed vertically in two short rows.

REFERENCE NUMERALS FOR DRAWINGS

10 Generally flat thermally conductive sheet;
12 Fastening means consisting of screws;
14 Fastening means consisting of adhesives;
20 Tubular fluid conduit or conduits;
30 Cap or caps having outwardly curving flanges on the cross-section;
31 Cap or caps having inwardly curving flanges on the cross-section;
32 Caps having a C-shaped cross-section transversely of the elongated direction with inwardly curving flanges;
35 Bend in the cap;
40 Undercut ridge raised from or attached to the sheet;
50 Undercut, convex ridge raised from or attached to the sheet;
60 Roof;
64 Silicone tube;
68 Eaves;
70 Wall;
80 Embodiment of the apparatus as a panel;
90 Fluid reservoir;
100 Shutters;
120 Hot fluid line;
125 Cold fluid line;
130 Top of an embodiment of the apparatus 140;
140 An embodiment of the apparatus;
150 Top of the fluid reservoir 90;
160 Bottom of the fluid reservoir 90;
170 Bottom of an embodiment of the apparatus 140;
180 Rise in the cold fluid line 125;
190 Vacuum breaker riser;
200 Upper header;
210 Lower header;
220 Fin;
230 Mullion; and
240 Horizontal slat.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the apparatus uses flexible thin wall plastic or rubber tubes or hoses (which more generally are types of “tubular fluid conduit or conduits”) pressed against the metal roof or walls of a building to gain heat from the sun in the day or dispose of heat to the atmosphere at night. A heat exchange fluid, such as water flows through the tubes by convection, or is pumped, to pick up solar heat during the day or to give out heat at night. Metal caps flatten, squash or otherwise securely fasten the tubes against the metal of the building. For an existing metal roof or metal sidewall, the caps can be held against the flattened tubes by adhesive such as silicone sealant. For a new metal roof or metal sidewall, the metal of the building can be formed in a series of raised sections with undercuts along the sides so that a cap may mechanically snap in place.
The skins of most metal buildings are poor heat conductors. Most metal buildings are actually made of steel, typically painted 26 gauge (0.0179 inch thick) steel or 29 gauge (0.0135 inch thick) steel. For such skins to serve well as collectors or radiators, the tubes with flowing water should ideally be within an inch or two of where the sun strikes. One inch tubes, when flattened, become 1⅜ inches wide. This is a significant advance in the design of flat plate collectors of the unglazed variety, which are particularly sensitive to poor thermal conduction of steel. It is fortunate that flattening or squashing the tubes makes them wider and the spaces between narrower.
The caps transfer heat to or from the flowing water in the tubes. The cap presses against the top or outside of the tube, while the metal roof or wall touches the underside of the tube. Sun striking the cap passes heat through the top of the tube. Sun striking the spaces between caps passes heat a longer distance to the bottom of the tube. In all flat plate collectors, the hottest point is about half way between tubes. If made of the same material, the sections of metal roof exposed between caps are hotter than the caps. These parts of the roof would be hotter and less efficient without the caps. The caps carry much of the heat that the roof would otherwise have to carry. The caps which were introduced to flatten the tubes against the roof act as thermal conductors as well. In one implementation, for the caps and underlying metal to work, the caps could intercept approximately half the sun and occupy half the space between it and the adjacent cap. Caps and roof even of the same metal can stress adhesive bonds as temperatures change. For this reason, if attached by adhesives, caps should be of relatively short lengths overlapping each other. Any heat transfer directly from cap to the building, and vice versa, through an adhesive on actual contact is welcome and increases efficiency, but it is unnecessary for good performance.
A dramatic demonstration of the efficiency of the cap and roof was made by flipping an assembly frontside-back, so a roof panel must transfer all the heat to the tube and the cap merely clings in the shade below. Efficiency dropped dramatically.
Other advantages of the cap and roof arrangement include variable flow cross section and freeze tolerance. When the caps, which are either glued or snapped, are made shallow, they squash the rubber or plastic tube almost flat, making the tube wide but also reducing its cross sections. This is an advantage, provided sufficient flow can occur.
Another feature of the cap is the potentially large contact area between flowing water and tube in direct contact with a metal heat conductor. When the space between cap and roof is 0.1875 inch, then a 1 inch diameter, 3.14 inch circumference tube has 2.55 inches of its circumference in contact with metal. If the tubes are 3 inches on center, there is a wet area in direct contact with metal comprising 85% of the area struck by the sun. If the tubes are 4 inches on center, then the sun strikes 69% of this area. This large area reduces the temperature differential between flowing water and tube, and is especially critical where sluggish thermosyphon flow restricts heat transfer at the interface.
A wall that thermosphyons to a water reservoir above it can have shallow caps and thus flattened tubes. There are large elevation differences and relatively large temperature differences to drive circulation with solar heating. Shallow caps can also be used with pumped flow. Where thermosyphon flow through almost horizontal roofs is used to cool water at night, larger flow channels are required. Here, the caps must be deeper, and the tubes have larger cross-sections. Another reason to have well flattened tubes for winter solar heating on walls is the freezing of water. The less ice that forms, the less heat is required the next day to melt it. Walls may be used to cool at night. This requires pumping if the thermal mass is above the wall.
Another advantage of using metal caps is that metal can flex when the water in the tubes freezes. Ice breaks water pipes because it expands 8%. Flexible tubes flattened between metal caps and a metal roof expand when ice forms. The metal flexes allowing the ice to expand but returns to the original volume when the ice melts. A 26 gauge, 1.5 inch wide, ⅛ inch deep cap, attached to a 26 gauge metal roof, flexes enough to allow the freeze thaw cycle at 10 psi. A cap only 3/32 inch deep would handle still greater pressure because the less the volume to freeze, the less the stress on the metal and its means of attachment.
Absorbers that freeze need to be able to expand, and then contract on thawing. Elasticity can be provided by rubber waterways such as silicone, santoprene or ethylene-propylene-diene monomer (epdm), by the metal cap and roof flexing or by a combination. Thin wall polyethylene is well suited as a waterway since a thickness such as 0.015 inch imposes only a small temperature change through the tube wall. To facilitate installation of the tubes, the tubes can be evacuated of air and thereby flattened.
The absorber/radiator in accordance with the embodiments of the present invention, which may have deep caps and large cross section tubes when used in roof radiators, does not need to withstand freezing for it can be drained the entire winter or at least during winter nights. During freeze thaw cycles an absorber need not necessarily withstand an entire 8% increase in volume if excess water can retreat from the freezing zone as freezing occurs. A roof collector used for passive summer cooling and drain back heating such as that described in U.S. Pat. No. 6,357,512 need not be freeze tolerant. In practice, care should be taken during freezing to allow some liquid to escape from the freezing zone as ice forms.
FIG. 1 shows a front and side elevation view of an embodiment of the apparatus wherein the caps have outwardly curving flanges on the cross-section, which caps are attached by either screws or adhesive, and the side of the sheet on which the caps are attached is exposed to the sun. The embodiment of the apparatus shown in FIG. 1 includes a generally flat thermally conductive sheet 10, tubular fluid conduit or conduits 20 fastened to the sheet 10 by a thermally conductive cap or caps 30. The thermally conductive sheet 10 and the thermally conductive cap or caps 30 can be made of any metal such as copper or aluminum, or of steel. The tubular fluid conduit or conduits can be made of rubber, plastic or metal, such as santoprene, silicone, polypropylene, polyethylene, ethylene-propylene-diene monomer, aluminum or copper. The tubular fluid conduit or conduits 20 are fastened to the sheet 10 by thermally conductive caps 40. As disclosed in the summary, the cap or caps can be fastened to the sheet by threaded fasteners such as screws 12 and nuts and bolts, adhesives 14 and epoxies, rivets, soldering, welding, nailing and snapping-on. A snapping-on fastening means is disclosed in FIGS. 3E and 3F below.
The cap or caps 30 have been made each with as few as one bend and typically with two bends, not counting the bends used to form outwardly- and inwardly-curving flanges. Embodiments where the cap 30 is a shallow V-shape cannot generally be walked on without disturbing or destroying the embodiment of the apparatus, since a force as would be exerted by walking on the embodiment might snap the cap loose or break it loose if fastened by adhesive. A flat cap, in contrast, would not move sideways under such a force. Such V-shaped embodiments, however, are functional, and may be used on walls 70.
FIG. 2A shows a front and side elevation view in detail of an embodiment of the apparatus using two different designs of caps, which are fastened to the sheet with screws or adhesive. FIG. 2B shows a front and side elevation view in detail of the cross-section of an embodiment of the apparatus using two different designs of caps, both of which are fastened to the sheet with screws or adhesive. FIGS. 2A and 2B show several types of caps 30 and fasteners. FIG. 2A shows a cap 30 with a single bend not counting the bends is used to form outwardly- and inwardly-curving flanges, and caps 30 with two bends. The caps 30 are fastened to the sheet 10 with either adhesive 14 or screws 12. FIG. 2B shows cross-sections of two types of caps 30, including those with both a single bend 35 and those with two bends 35. Both types of caps 30 in FIGS. 2A and 2B have outwardly curving flanges 31 on the cross-section.
FIG. 3A shows a cap 30 having a single bend 35 not counting the bends used to form outwardly- and inwardly-curving flanges, wherein the cap 30 is fastened to the sheet 10 using screws 12. FIG. 3B shows a cap 30 having a single bend 35, wherein the cap 30 is fastened to the sheet 10 using adhesive 14. FIG. 3C shows a cap 30 having two bends 35, wherein the cap 30 is fastened to the sheet 10 using screws 12. FIG. 3D shows a cap 30 having two bends 35, wherein the cap 30 is fastened to the sheet 10 using adhesive 14. FIG. 3E shows a cap having a C-shaped cross-section transversely of the elongated direction 32, attached to a ridge 40 that is undercut and raised from the sheet 10. As shown in FIG. 3F, with a raised and undercut ridge that is also convex 50, then when the ridge or ridges 50 go into compression, the cap or caps 32 more tightly grip the ridge or ridges 50 than with a non-convex ridge. FIG. 3G shows a flat-topped cap 30 and a flat-topped ridge 50; in such a configuration, the flexing is most comfortable.
FIG. 4A shows an undercut ridge 40 raised from the sheet 10. FIG. 4B shows a sheet 10 having an undercut, convex ridge 50 raised from or attached to the sheet 10.
FIG. 5 shows that the sheet 10 is a metal roof 60 over a house or other structure, providing to the inside of the structure a thermally controlled environment. For an existing metal or steel roof 60, the caps 30 and tubes are fastened in a pattern that conforms to the existing ridges of the corrugation. For a new 0.0179 inch (26 gauge) steel roof 60, the roof 60 is roll formed with 0.125 inch deep raised, undercut ridges 40 spaced every 4 inches, pressing a ⅞ inch inner diameter 0.015 inch wall polyethylene tube 20 between a 2 inch wide cap 30 and the roof 60. For a new 0.032 inch aluminum roof 60, the roof 60 is roll formed with 0.1875 inch deep raised, undercut ridges 40 spaced every 6 inches, pressing a ⅞ inch inner diameter 0.015 inch wall polyethylene tube 20 between a 3 inch wide cap 30 and the roof 60. When using caps having at least ¼ inch outwardly curving flanges, the caps 30 are glued on to the steel or aluminum below. When using caps having a C-shaped cross-section transversely of the elongated direction with inwardly curving flanges 32, the caps 32 are snapped on to the raised, undercut ridges.
The sheet 10 and the caps 30 are made with 0.0179 inch (26 gauge) steel (with a thermal conductivity of 26 BTUs per degrees F. per foot per hour), because a human can generally walk on it without damaging the roof 60 or the embodiment of the apparatus 140 and because the materials are relatively inexpensive. Steel has relatively poor thermal conductivity, but the embodiment of the apparatus will work despite poor thermal conductivity. Other embodiments are constructed with an aluminum (with a thermal conductivity of 128 BTUs per degrees F. per foot per hour) sheet 10 and caps 30. The tubular fluid conduit or conduits 20 consist of ⅞ inch inner diameter, 0.015 inch wall polyethylene (with a thermal conductivity of 0.20 BTUs per degrees F. per foot per hour). A thinner walled plastic tubing is preferred, because the heat transfer is better due to a smaller temperature drop across the tube wall.
The cross-section of the tubular fluid conduit 20 varies by the pitch of the roof 60. Shallow roofs 60 require larger flow channels, therefore larger cross-section tubes 20, for easier flow.
An example of this embodiment is as the radiator/absorber for U.S. Pat. No. 6,357,512 (Baer and Mingenbach), which is a passive solar thermal control system that utilizes a roof 60. Such embodiment utilizes upper 200 and lower 210 headers, one at each of the terminal ends of the tubular fluid conduit or conduits 20. The most cost effective method of connecting the silicone tube 64 to the header 200, 210 is by simple mechanical puncture of the header 200, 210 by the silicone tube 64. Because fluid will be lost though the silicone tubes 64, extra large headers 200, 210 are used so that they also serve as expansion tanks. Because of this fluid loss, the system needs annual refilling.
FIG. 5C shows an embodiment wherein the upper headers 200 are concealed under the roof 60 and lower headers 210 are concealed in the eaves 68. The upper headers 200 are concealed from view by connecting the tubular fluid conduit or conduits 20 at their lower ends to silicone tubes 64 in which a ninety degree bend is formed such that the silicone tube 64 may pass through a hole 66 in the roof 60 and connect to an upper header 200. The lower headers 210 are concealed from view by connecting the tubes 20 at their lower ends to silicone tubes 64 in which a ninety degree bend is formed such that the silicone tube 64 may pass under the eaves 68 and connect to a lower header 210.
As shown in FIG. 6, an embodiment of apparatus 140 is alternatively built as a panel 80 on a roof 60, rather than as an integral part of the roof 60 as in FIGS. 5A-C.
As shown in FIG. 7, it is possible to deploy an embodiment of the apparatus as an integral part of a wall 70 rather than a roof 60. The wall 70 will work better for heating, rather than cooling. South-facing walls 70 are preferred, due to their solar exposure. Because of the steep elevation gradients and temperature gradients that will occur within a vertical configuration, wall deployments of embodiments of the apparatus should have smaller cross-section tubes 20 to reduce the volume of fluid. The smaller cross-section tubular fluid conduit or conduits 20 also lessens the thaw-out time in the morning. Because walls 70 will not be walked on, the shallow V-shaped cap 30 with a single bend may be used; generally, less robust materials and configurations can be used on walls 70.
One embodiment of the wall 70 is similar to that as disclosed in U.S. Pat. No. 6,357,512 (Baer and Mingenbach), for which an embodiment of the apparatus serves as the radiator/absorber that is named in the patent, but which radiator/absorber is deployed in a vertical position in a manner described below. A fluid reservoir 90 is situated near the ceiling 100 above the space to be cooled or heated 110. A hot fluid line 120 runs from the top 130 of the embodiment of the apparatus 140, which embodiment of the apparatus 140 is deployed as a vertical panel on the wall 70, to the top 150 of the fluid reservoir 90. A cold fluid line 125 runs from the bottom 160 of the fluid reservoir 90 to the bottom 170 of the embodiment of the apparatus 140. To prevent siphoning the water back out of the fluid reservoir 90 if the fluid pressure is lost, the well-known technique is used that involves raising 180 the cold fluid line 125 as it leaves the fluid reservoir 90 to the level of the top of the fluid reservoir 90, that is, above the water line, and adding an anti-siphon hole 190 at the raised point 170.
As shown in FIG. 8, an embodiment of the apparatus 140 is built as a panel 80 that is then deployed on a wall 70, rather than building the apparatus 140 into the wall 70 itself as in FIG. 7.
FIG. 9 shows an embodiment of the apparatus 140 in the form of a heat collecting fin 220 used in flat plate collectors. Such a fin 220 does not need to lie on a roof or wall. There is a saving of approximately twenty-five percent in fin material with no loss in efficiency as compared to fins with constant cross sections. FIG. 9 shows an eight inch wide, 0.040 inch aluminum sheet as a back plate 10, with a five inch wide, 0.040 inch aluminum cap 30 fastened around a three-quarter inch copper pipe as the fluid conduit 20. This system had the same performance as an eight inch wide snap-on 0.070 inch thick aluminum extrusion which weighed twenty-five percent more.
FIG. 9 shows two ways in which this embodiment is deployed, namely in one or two long lines or many short rows, either horizontally (FIG. 9C) or vertically (FIG. 9D). This flexibility allows the collector to be designed to suit the space available to it. In the horizontal configuration the heat collecting fins can be cut to fit between mullions 230 or (their equivalents if windows are not used, e.g., vertical slats) with pipes strapped into place. With sufficient mullion 230 depth they can be rotated on the tubes to provide seasonal light adjustment as well as optimum collection angle. They can also be mounted directly to the mullions 230. In the vertical configuration they can be cut to fit horizontal slats 240.
Some advantages of the embodiments of the apparatus were previously enumerated above. Every advantageous feature does not need to be incorporated into every embodiment of the apparatus and/or methods.
All publications and descriptions mentioned above are herein incorporated by reference in their entirety for all purposes. None is admitted to be prior art.
The above description is illustrative and is not restrictive, and as it will become apparent to those skilled in the art upon review of the disclosure, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. These other embodiments are intended to be included within the scope of the present invention. For example, the cap or caps could be fastened to the thermally conductive sheet by pierce tags or by buckles, and the tubes and caps and ridges could run diagonally or at other angles across the roof or wall. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the following and pending claims along with their full scope or equivalents.

Claims

1. An apparatus for absorbing heat from the sun and dissipating heat to the atmosphere at night; said apparatus comprising:

a generally flat thermally conductive sheet which serves as a back plate;

one or more tubular fluid conduit or conduits;

a generally rectangular thermally conductive cap for covering and pressing said conduit or conduits against said sheet; said cap having a length and a width generally covering the one or more of said conduit or conduits; said cap not covering the entire sheet if used in plurality; said cap not contiguous to each other in the parallel if used in plurality; and

a means for fastening the thermally conductive cap to said thermally conductive sheet; thereby covering said one or more conduit or conduits and pressing them against said sheet; said cap fastened to that side of said sheet which is exposed to the sun and atmosphere.

2. The apparatus of claim 1 wherein said thermally conductive sheet or thermally conductive cap are made of steel.

3. The apparatus of claim 1 wherein said thermally conductive sheet or thermally conductive cap are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

4. The apparatus of claim 1 wherein said tubular fluid conduit or conduits are made of a plastic material selected from the group consisting of polyethylene and polypropylene.

5. The apparatus of claim 1 wherein said tubular fluid conduit or conduits are made of a rubber material selected from the group consisting of silicone, santoprene, ethylene-propylene-diene monomer (epdm), and combinations thereof.

6. The apparatus of claim 1 wherein said tubular fluid conduit or conduits are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

7. The apparatus of claim 1 wherein said cap has an outwardly or inwardly curved flange on the cross-section transversely of the elongated direction.

8. The apparatus of claim 7 wherein said thermally conductive sheet or thermally conductive cap are made of steel.

9. The apparatus of claim 7 wherein said thermally conductive sheet or thermally conductive cap are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

10. The apparatus of claim 7 wherein said tubular fluid conduit or conduits are made of a plastic selected from the group consisting of polyethylene and polypropylene.

11. The apparatus of claim 7 wherein said tubular fluid conduit or conduits are made of a rubber selected from the group consisting of silicone, santoprene, ethylene-propylene-diene monomer (epdm), and combinations thereof.

12. The apparatus of claim 7 wherein said tubular fluid conduit or conduits are made of a metal selected from the group consisting of aluminum and copper.

13. The apparatus of claim 7 wherein said means for fastening comprises a generally rectangular thermally conductive cap having a C-shaped cross-section transversely of the elongated direction; and ridge or ridges raised from or attached to said thermally conductive sheet; said ridge or ridges undercut transversely of the elongated direction.

14. The apparatus of claim 13 wherein said raised and undercut ridge or ridges are convex.

15. The apparatus of claim 13 wherein said thermally conductive sheet or thermally conductive cap are made of steel.

16. The apparatus of claim 13 wherein said thermally conductive sheet or thermally conductive cap are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

17. The apparatus of claim 13 wherein said tubular fluid conduit or conduits are made of a plastic selected from the group consisting of polyethylene and polypropylene.

18. The apparatus of claim 13 wherein said tubular fluid conduit or conduits are made of a rubber selected from the group consisting of silicone, santoprene or ethylene-propylene-diene monomer (epdm).

19. The apparatus of claim 13 wherein said tubular fluid conduit or conduits are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

20. A method for using a thermally conductive sheet to gain heat from the sun in the day or to dispose of heat at night; said method comprising:

utilizing a cap or caps to press a tubular fluid conduit or conduits containing fluid against said thermally conductive sheet;

exposing to the sun or atmosphere that side of the sheet onto which the tubular fluid conduit or conduits are fastened by said cap or caps; and

allowing said fluid to flow through said tubular fluid conduit or conduits by convection; or pumping said fluid to pick up solar heat or to give out heat during the night.

21. The method of claim 20 wherein said thermally conductive sheet or thermally conductive cap or caps are made of steel.

22. The method of claim 20 wherein said thermally conductive sheet or thermally conductive cap or caps are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.

23. The method of claim 20 wherein said tubular fluid conduit or conduits are made of a plastic selected from the group consisting of polyethylene and polypropylene.

24. The method of claim 20 wherein said tubular fluid conduit or conduits are made of a rubber selected from the group consisting of silicone, santoprene or ethylene-propylene-diene monomer (epdm).

25. The method of claim 20 wherein said tubular fluid conduit or conduits are made of a metal selected from the group consisting of aluminum, copper, and combinations thereof.