DE2835371A1 - SUN HEATER WITH HEAT TRAP - Google Patents

Description

28353 ?!

L-11477-G

UNION CARBIDE CORPORATION 270 Park Avenue, New York, N.Y. 10017, 'V. St. A.

Solar heater with heat trap

The invention is concerned with solar heaters, the solar radiation convert into heat energy and the absorbed Transfer heat to either a gas, such as air, or a liquid, such as water. devices of the first-mentioned type are usually called solar air heaters and devices of the last-mentioned type referred to as solar water heaters. The invention relates in particular to solar heaters of the one and the other another type in which a heat trap is provided between the absorber and the translucent front wall is.

Various proposals have already been made, a heat trap between the absorber and the front wall of a Flat plate solar heater or a perspiration solar air heater to be provided. This is how Hollands describes the use of a transparent honeycomb heat trap a flat plate solar heater in an essay "Honeycomb Devices in Flat Plate Solar Collectors", Solar

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Energy, Volume 9, pages 159 to 169, Pergamon Press (1965). The purpose of the transparent honeycomb heat trap is to suppress the occurrence of natural convection currents j it also reduces heat loss through radiation

It has also been found that a transparent honeycomb heat trap de; n Overall efficiency of a transpiration air heater increases significantly if the heat trap is located between the porous absorber and the front wall (same priority Patent application P 28 23 449.3). If the honeycomb heat trap is at least in firm mechanical contact held with the front wall, it also provides an air buffer layer without creating additional surfaces by which incident sunlight is reflected away by the absorber and can thus be lost.

Transparent cell structure, for example honeycombs made of clear Plastic or glass, which are considered as heat traps in solar heaters of the above type have been made in a number of well known ways. According to a previously used procedure Tubes made of clear plastic or glass stacked together and over a suitable adhesive or with the help bound together by solvent. According to another method, several elongated, narrow strips of plastic film first

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stand apart points coated with an adhesive and then made to adhere to each other. This is followed by stretching to form a hexagonal honeycomb structure. The use of such a composite, stretched Honeycomb arrangement in a flat panel solar heater was described in an article entitled "Effect of a Mylar Honeycomb Layer on Solar Collector Performance "by Chun and Crandall, on the occasion of 1974 Winter Annual Meeting of the ASME (Paper No. 74-WA / HT-11) was presented.

A disadvantage that is common to all honeycomb structures corresponding to those discussed above or other similar ones Methods are established is the presence of adhesive bonds between adjacent cells. These adhesive bindings pose certain problems when the honeycomb arrangement is used as a heat trap in a solar heater will. One of these problems is that the adhesive bonds act as scattering points for incident light act and thus the resulting transmission of sun rays through the honeycomb arrangement in all of the vertical Reduce incidence at different angles of the sun. That means, at all times, with the exception of the highest point of the sun, becomes the proportion of the incident sunlight that the solar absorption surface in the solar heater achieved, reduced, which leads to a reduction in the conversion efficiency. A white

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Another problem associated with the application of any glue can be, is that the adhesive ages and that it cracks, embrittlement and as a result Discoloration is coming. The manufacture of honeycomb structures from clear plastic or glass using an adhesive is also complicated by the fact that adhesives require special handling, whereby the manufacturing process becomes time consuming and costly.

The present invention is directed to a novel and improved solar heater that is a flat panel solar heater or a perspiration solar heater can act for gaseous media and that the above-mentioned problems of known arrangements clears out. The aim is to create a solar heater with a heat trap that is different in comparison to known ones Heat traps are characterized by high permeability for incident sunlight. It's supposed to be a solar heater be created with a heat trap, which has a cell ge-Tugt with a plurality of cells and which easily and is economical to manufacture.

The solar heater according to the invention has a housing with a transparent front wall and a radiation-absorbing one Collector element which is arranged such that it is conspicuous, passing through the front wall Absorbs solar radiation. The solar heating

advises is further provided with a heat trap equipped ,, -: daee least partially aas an open Zeil close-rage is that ays integrally thermally verfformbaran material is made "The 'the Wäinmefalle forming, open cell array is composed of' a plurality of adjacent en cells ., each of which raises the walls together with others of the Ge, whereby the walls are formed in one piece with the walls of cells in continuous pieces. In the case of the one obtained in this way, there are no adhesive bonds connecting the wall © of neighboring cells to one another. As a result, the thermal film has a high level of permeability for solar rays in comparison with the known honeycomb arrangements which are ziässuumero-joined. With the warmth ^for all, there is also no deterioration due to the cd: as -aging of an adhesive. As will be explained in more detail below, the open cell structure can easily be produced from the product of an expanded core process or by injection molding,

The invention is described below on the basis of preferred exemplary embodiments in conjunction with the drawings explained in more detail. Show it:

Fig. 1 is a schematic, sectional. Aufrißansicht a typical flat panel solar heater according to the invention,

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Figure 2 is a similar view for a typical one

Transpiration solar heater for gaseous media,

Fig. 3 on a larger scale a perspective

Schematic representation of part of the transpiration solar heater according to Fig. 2,

Figures 4a to 4c are schematic sectional elevation views the punch that is used in the expansion stretching process to form molded parts are used, from which heat traps of the type provided herein can be made, the Stamps are illustrated in their relative positions during different phases of the process,

Figure 5 is a top plan view of individual film strips

fen prior to their connection to a honeycomb arrangement according to the known Manufacturing process,

6 is a similar view of the honeycomb assembly

voltage obtained by connecting the film strips together as shown in FIG

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became,

Figure 7 is a similar view of another

Type of honeycomb arrangement made of interconnected in a known manner Pipes,

Fig. 8 is a schematic representation of a

a connected honeycomb cell wall of incident sunbeam and the resulting Distribution of transmitted, reflected and scattered rays,

Fig. 9 is a schematic representation of a

a honeycomb cell wall of the type provided in the present case of incident sunbeams and the resulting distribution of the transmitted and reflected rays, as

Fig. 10 is a graphical representation of the versus

lateral relationship between the angle of incidence and the solar radiation transmittance of different heat traps.

The principles of the present invention are at both

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Flat-plate solar heaters as well as transpiration solar heaters Applicable for gaseous media, although the heat trap in these two types of solar heating devices fulfills slightly different functions. The invention is therefore independent in the following both types of solar heaters explained.

Fig. 1 shows a flat-plate solar heater constructed according to the invention. The solar heater has a housing with a translucent front wall 12, the incident Allows solar radiation to pass through. The housing is also equipped with a rear wall 14. The front wall 12 is preferably made of a clear or transparent material that has a relatively low reflectivity has, is not porous and is impermeable to gas, for example made of a clear plastic or glass. One flat, radiation-absorbing collector plate 16 is inside the housing 10 at a distance from the front wall and the rear wall 14 mounted. The collector plate 16 is arranged in the housing 1O so that it passes through the front wall Catches 12 sun rays passing through. A coil 18 or other passage arrangement for a Fluid, for example air or water, is in contact with the flat collector plate 16. Preferably located As illustrated, the pipe run 18 is in the space below the collector plate 16. The remaining space between the flat collector plate 16 and the rear wall

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14 can be provided with an appropriate insulation 20, for example Glass wool to be filled. The housing 10 can advantageously be made of a rigid metal, for example aluminum or steel, or another rigid material, such as plastic or glass fibers (Fiberglass panels).

The housing 10 also has a heat trap 22 which sits directly under the front wall and the cell arrangement, for example honeycomb arrangement, is constructed from one piece. The heat trap consists of a multitude of cells 24 with cell walls 26 that lead to the front wall 12 run essentially perpendicular.

During the operation of the solar heater, incident sun rays pass through the front wall 12 and the heat trap 22; they are absorbed by the flat collector plate 16 and converted into heat. This heat is in turn transferred to a fluid through heat conduction and convection, for example air or water, transmitted through the coil 18 in contact with the collector plate 16 circulates.

In this embodiment of the invention, the heat trap is used 22 the dual purpose of reducing the radiant heat loss from the solar heater and the training natural convection in the air space between the

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flat collector plate 16 and the front wall 12 to suppress. So that the heat trap can effectively reduce heat loss through radiation, the cells must 24 have a sufficiently high aspect ratio, as described in detail in patent application P 28 23 449.3 is depicted. In the case of honeycomb arrangements, this ratio should be in the range from 2 to 10. As illustrated in FIG. 1 is, the cell walls 26 subdivide the air space between the flat collector plate 16 and the front wall 12; they prevent the formation of natural convection currents. In order to allow different thermal expansions of the elements of the solar heater, above or a gap may be provided below the heat trap.

Fig. 2 shows a transpiration solar heater constructed according to the invention for gaseous media. As illustrated, the device has a housing 28 with a transparent front wall 30, made for example of plastic or glass, and a rear wall 32. The housing 28 is further provided with an inlet 34 in one side wall and an outlet 36 in the opposite side wall. The inlet 34 and the outlet 36 provide for the formation of a flow path leading through the housing 28 for a gas to be heated, for example air, as indicated by the arrows. A porous, radiation- absorbing Kollektorplat 38 sits within the housing 28 parallel to and in

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Distance from the front wall 3O and the rear wall 32 in the Flow path between inlet 34 and outlet 36. The porous collector plate 38 can, for example, consist of a porous, dark or black fiber mat, woven or punched screen material or reticulated foam. While at the illustrated Embodiment the porous collector plate 38 runs parallel to the rear wall, the collector plate can also be arranged in non-parallel relation to the rear wall, as disclosed in patent application P 28 23 449.3 is. If desired, an insulation layer 40 may be adjacent the back wall 32 and spaced from the porous Collector plate 38 are arranged. The housing 28 can also in this case made of a rigid metal, for example Aluminum or steel, or another rigid material, for example plastic or a fiberglass material, be made.

A heat trap 42 sits immediately below the front wall 3O. The heat trap consists of a cell arrangement, for example a honeycomb arrangement; it is also "■ constructed in one piece, as will be explained in more detail below. In this embodiment, the heat trap basically has the same structure as in FIG. 1. You has cells 44 which are delimited by cell walls 46, which are essentially perpendicular to the front wall 3O. In this case, however, the heat trap 42 is in the

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house 28 mounted in such a way that an expanded room 48 is created. This space 48 is used for the passage of the gas to be heated, for example air, between the underside the heat trap and the porous collector plate 38.

The mode of operation of the transpiration solar heater for gaseous media is similar in that it is striking Sun rays pass through the transparent front wall 30 and the heat trap 42 and from the porous collector plate 38 can be absorbed and converted into heat. In this case, however, the gas to be heated occurs, for example Air, via inlet 34 to then follow the flow path in the manner indicated by the arrows. The gas, for example air, penetrates the entire porous collector plate 38 and is heated. That heated Gas then exits via space 50 under porous collector plate 38 and through outlet 36. at In this embodiment, the heat trap 42 is twice that Task to reduce the radiant heat loss from the solar heater and an air buffer layer with To form partitions that create a forced convection flow of the gas to be heated adjacent to the front wall prevent where heat loss can occur. In the manner described in patent application P 28 23 449.3 the heat trap is preferably held at least in firm mechanical contact with the front wall 30; she can be connected to the front wall. In this way

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the effect as an air buffer is improved. With this one Construction, it is not necessary to provide an additional, gas-impermeable layer to allow the gas flow through to prevent the honeycomb assembly through and in contact with the front wall. The length ratio of the heat trap is basically the same in this embodiment as described above; that is, in the case of honeycomb arrangements, it is in the range between approximately 2 and 10.

In the embodiment according to FIG. 2, the heat trap is seated directly under the front wall 30 of the transpiration solar heater, where it acts as an air buffer and radiation trap. It should be understood, however, that the invention is not limited to such an arrangement of the heat trap. As explained in patent application P 28 23 449.3 it can also be advantageous to place the heat trap or the heat trap on the porous collector plate to be mounted between the collector plate and the front wall.

Fig. 3 shows in detail the worm trap 42, which in the Transpiration solar heater for gaseous media according to FIG. 2 is provided. The heat trap can basically consist of a plurality of cell arrays; preferably, as shown, a hexagonal honeycomb arrangement is used used. As illustrated, the honeycomb arrangement consists of a plurality of hexagonal cells 44,

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which are arranged adjacent to one another and bounded by the walls 46, common to the other cells of the arrangement are. The walls are with the walls of other cells integrally and in one piece connected. The cell walls 46 are essentially perpendicular to the plane of the front wall. The heat trap of the flat panel solar heater according to Fig. 1 can basically have the same hexagonal structure.

The heat trap can be made in one piece using conventional molding, pressing, casting or injection molding processes getting produced. The heat trap can advantageously be made of glass or a clear plastic made of polyvinyl fluoride, Polycarbonate, fluorinated ethylene propylene, polymethyl methacrylate, aromatic polysulfones, polyethylene terephthalate, aromatic polyester, polyvinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene and tetra · fluoroethylene copolymers comprehensive group .

In the embodiments schematically illustrated in FIGS. 1 to 3, the cells are equipped with relatively thick walls for the sake of illustration only. It is understood that the walls to serve as an efficient heat traps, be relatively thin, that is, a thickness of between about O, 002 and ₁ O 5 must mm.

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The heat trap can be created with the help of conventional shape, Pressing, casting or spraying processes are produced. For example the heat traps can be opened in a particularly advantageous manner in accordance with US Pat. No. 3,919,446 known expanded core process. Modifications and improvements to this method and the device Its implementation is known from U.S. Patents 3,765,810, 3,919,379, 3,919,380 and 3,919,445.

FIGS. 4a to 4c show different phases of the expanded core process. In the first phase of the process, a blank 52 made of thermally deformable material is between two heated punches 54, 56 brought, corresponding to FIG. 4a with a group of vent holes 58 are provided. In the next phase, the heated punches 54, 56 according to FIG. 4b are in contact with the blank 52 brought. Then, under the force of compressed pretensioning springs 60, 62, the punches are moved apart, whereby the cross section of the blank 52 is stretched in such a way that cavities, for example cells 64 of hexagonal shape, are formed from the surfaces of the blank. As can be seen from Fig. 4c, the Cell arrangement formed in this way manufactured in one continuous piece, with cell walls 66 adjacent cells 64 in common are. These walls are integral with other cell walls of the cell array, such as this in particular from the perspective view of

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Fig. 3 shows. Usually they are made this way Molded parts are provided with a perforated skin on one or both sides, as indicated at 68 in FIG. 4c is. The skin or skins must be removed before the molding can be used as a heat trap suitable is. The perforated skins, if not removed, would be oriented so that Striking rays of the sun, which are reflected by the skins, would be directed away from the absorber and would be lost. The perforated skins can be removed by inserting an electrically heated wire through the cell walls directly adjacent to the skins is passed through or by a counter-cutting, with a knife edge equipped band saw blade is used as it is for the cutting of metallic honeycombs is provided. For a better understanding of the process, refer to the above referenced patents. By the way, understands it is that the heat trap can also be manufactured with the help of other processes, for example in Injection molding process in which a material that can be deformed under heat is injected under pressure into a mold, which has the desired cell shape.

Heat traps for known solar heaters have been made using connected, elongated honeycomb assemblies manufactured. Such honeycomb structures can be made possible by the in

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Establish the connection method shown in Figs. In this case, a plurality of strips, for example of at 7Oa ₁ 70b and 70c-indicated type, which consist of a plastic film, folded or wave-shaped in a different way and laid side by side such that the flat sides 72a, 72b and 72c aligned with each other. A suitable adhesive is then applied to at least one of the flat sides, whereupon the flat sides are made to adhere to the respective opposite flat sides, forming a hexagonal honeycomb arrangement as shown in FIG. The aligned sides 72a, 72b and 72c, after they are brought together for adherence, form a plurality of adhesive bonds which are distributed over the entire honeycomb arrangement.

A similar honeycomb arrangement for solar heaters can 7 can be made from a plurality of transparent tubes 76 in accordance with FIG. The tubes 76 are similar Placed adjacent to each other and then along their longitudinal surfaces with an adhesive coated. The tubes 76 are then made to adhere to one another, a plurality of Adhesive bonds 78 is formed.

Any connected honeycomb arrangement such as the

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embodiments explained above, has the disadvantage that the connection points cause a scattering of incident light. Fig. 8 shows a typical sunbeams falling on a connected honeycomb cell wall as well as the resulting distribution of transmitted, reflected and scattered rays. The incident one Beam 80 is partially transmitted at 80a and partially reflected at 80b. Part of the incident Beam 80 is also scattered in the form of a plurality of diffuse beams 80c. The diffuse rays 8Oc are due to the light scattering at the adhesive bonds 74 of the connected, stretched honeycomb arrangement, as shown in FIG. 6, for example. A similar scattering of incident sun rays it comes to the adhesive bonds 78 of the tubular honeycomb arrangement according to FIG. 7. The presence of adhesive bonds in honeycomb arrangements, the total permeability of the honeycomb arrangement for solar rays can therefore be considerable Reduce. This reduction in light transmission occurs at all angles of incidence of the sun's rays, with the exception of a perpendicular incidence. With the exception of the highest point of the sun, it therefore happens all the time to reduced conversion efficiencies.

FIG. 9 shows a typical sunbeam which strikes a cell wall of a honeycomb arrangement, such as that used as a heat trap is provided according to the invention. the

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The honeycomb arrangement is constructed in one piece and provided with integrally formed cell walls 82, see above that there are no joints that could scatter incident light. The incident ray 84 is partly transmitted and partly reflected, like this is indicated at 84a or 84b. Because in the honeycomb cell walls If there are no scattering points, no scattered, diffuse rays are illustrated in FIG. 8. Regardless of the type of honeycomb arrangement used the transmitted and the reflected rays run in a one passing through the heat trap Direction continues while at least part of the scattered rays are directed out of the heat trap and away from the absorber so that they are lost.

A number of attempts have been made to find the Total solar radiation transmission of honeycomb heat traps of the type described here to be compared with the permeability, as is the case with known connected honeycomb traps is to be found. In the course of the tests, two types of connected honeycomb structures were compared. at One type was a honeycomb made of connected, stretched strips, essentially as shown in Fig. This honeycomb arrangement was made of clear Mylar (trademark of the Dupont company) and had hexagonal cells a length of 51 mm and an effective diameter

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of 9.5 mm. The other type of joined honeycomb used in the experiments was made of tubes joined together in the manner shown in FIG. These connected honeycombs were made of a clear polycarbonate; they had circular cells 51 mm long and 4.8 mm in diameter. The honeycomb traps constructed according to the invention were made from honeycomb arrangements which were produced in accordance with the expanded core method explained above. The honeycombs were made in one continuous piece from polycarbonate and had hexagonal cells with a length of 25.5 mm and an effective diameter of 6.35 mm. The exact composition of the adhesive used to make the honeycomb assemblies from interconnected elongated strips or interconnected tubes was not known.

The experiments were carried out in the following manner: Two calibrated pyranometers were mounted on the same flat surface which could be adjusted to change their orientation with respect to the sun. The honeycomb structure to be tested was then placed in a plane parallel to the flat surface and above one of the pyranometers. The radiant flux incident on each pyranometer was then measured for angles of incidence of sunlight between approximately 0 and 50 degrees. The ratio of the flow under the honeycomb to that without

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The flow measured by the honeycomb arrangement was determined. This relationship represents the total solar radiation permeability of the honeycomb arrangement,

Fig. 10 shows the results of these investigations. At From curve A it can be seen that in the case of the honeycomb arrangement of connected, stretched 51 mm strips, a rapid one Decrease in total solar radiation transmission occurs with increasing angle of incidence. The permeability falls from a value above 0.9O at normal incidence to a value less than 0.70 at an angle of incidence from 50. This area for the angle of the incident Sun rays correspond to an operation of the sun heater between approximately 3 hours before and after Highest level of the sun, if the solar heating device is aligned so that it faces the sun when the sun is high is. The permeability of the 51 mm honeycomb arrangement out of each other connected pipes shows, as can be seen from curve B, a similar dependence on the angle of incidence. the Permeability increases from a value above 0.85 normal incidence to a value less than 0.70 at an angle of incidence of about 50. In comparison, the integrally formed 25.5 mm honeycomb assembly has high transmittance over a wide range of angles of incidence, as curve C shows. because a 51 mm expanded core honeycomb arrangement at the time the test was carried out for comparison with the affiliated

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51 mm honeycomb arrays were not available built a 51 mm expanded core hybrid honeycomb arrangement. This hybrid honeycomb arrangement was obtained in that two 25.5 mm honeycomb arrays above the test pyranometer were stacked on top of each other. However, it was to be expected from the outset that this hybrid honeycomb arrangement would not the same performance as a 51mm expanded core honeycomb assembly would show because there are additional light scattering points at the upper end of the lower honeycomb arrangement are. The test data were recorded for this hybrid honeycomb arrangement; they are in Fig. 10 as a curve D shown. The results that are to be expected with a one-piece 51 mm expanded core honeycomb arrangement are unsatisfactory extrapolate from the above results by adding the losses at the end of the second honeycomb be taken out. This is shown in curve E. The light transmission begins in the case of extrapolated results for the 51 mm expanded core honeycomb assembly with the same high value as for the 25.5 mm expanded core honeycomb assembly at normal incidence. The light transmission drops for the extrapolated results somewhat faster with increasing angle of incidence, but remains above 0.8 ° for angles of incidence up to about 50 °. This more rapid drop in permeability is due to the additional thickness of the honeycomb structure, which is desirable in view of the effective use of the honeycomb arrangement as a heat trap. Even in the case of

stacked 51mm hybrid honeycomb with additional The total light transmission is far from that of both known connected honeycomb assemblies think.

In the illustrated embodiments of the heat trap, the walls are perpendicular to the plane of the front wall. However, the invention is not limited to such a design. The cell walls can also be other Take angles as long as only reflected from the cell walls Sun rays are not reflected back towards the front wall during normal operating periods will. The term "essentially perpendicular to the front wall" used in the present case is consequently also intended to include such other angles with respect to the alignment of the cell walls include. It was found that the cell walls in Angles with respect to the normal of up to about 22.5 can be arranged without incident sun rays are reflected away by the solar absorber if a period of time is selected as the normal operating time that is from about 3 hours before to 3 hours after the highest level of the sun is enough. For a more detailed explanation of the cell wall angle and its derivation, see referred to the patent application P 28 23 449.3.

The invention is also not limited to heat traps that are completely made of one piece ^ Bl

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(SS) PWi

ZI3MHDS (SS)

ORIGINAL INSPECTED

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Rather, metals can also consist of two or more integral parts Cellular structures should be constructed in a more appropriate manner Way, for example by means of an adhesive, are connected to one another. This glue would then be the only glue that is inside the entire heat trap assembly is available.

The heat trap according to the invention can also be provided with a transparent one Front wall or glazing be integrally connected, as in the patent application filed on the same day assigned to the applicant "Solar Heater" (U.S. Priority Aug. 12, 1977, USSN 824,103) is explained.

The present invention thus becomes a solar heater created with a heat trap which, compared to known heat traps, is characterized by high permeability for incident sunlight. In particular becomes a heat trap for a solar heater obtained, which is made of a cell structure with a large number of neighboring cells, their common Walls are formed in one piece from the same clear or transparent, thermally deformable material. The heat trap constructed according to the invention does not contain any Adhesive bonds or seams that are used to scatter, collapsing Sunlight and which can discolour or otherwise suffer damage over time.

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with the exception of connections that are necessary can be to unite large sections of the integral cellular structure.

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Claims (22)

Expectations / i .iSun heater, characterized by a housing (1O, 28) with a conspicuous solar radiation transmitting, transparent front wall (12, 30), a radiation-absorbing collector element (16, 38), which is housed in the housing and arranged to receive incident solar radiation passing through the front wall, a device (18, 34, 36) for passing a fluid medium to be heated through the housing in heat exchange with the collector element, and one in the housing between the collector element and the front wall arranged heat trap (24, 42) of cellular Structure with a large number of adjacent cells. len (22, 44), the walls of which are in a continuous Piece made of a translucent, thermally deformable, emitted opposite from the collector element Infrared radiation opaque material are integrally formed with the walls of other cells. 2. Sun heater according to claim 1, characterized in that that as a thermally deformable material glass 909807/1051 TELEPHONE: 089/6012039 CABLE: ELECTRICPATENT MUNICH ORIGINAL INSPECTED or a clear plastic made of polyvinyl fluoride, Polycarbonate, fluorinated ethylene propylene, polymethyl methacrylate, aromatic polysulfones, polyethylene terephthalate, aromatic polyesters, polyvinylideniluoride, Hexafluoropropylene, chlorotrifluoroethylene and Tetrafluorodethylene copolymers comprehensive group provided is. 3. Sonnenheizgerat according to claim 1 or 2, characterized in that that the cellular structure has transparent honeycombs. 4. Sonnenheizgerat according to claim 3, characterized in that that the transparent honeycombs consist of a plurality of cells with a hexagonal cross-section. 5. Sonnenheizgerat according to claim 3 or 4, characterized in that that the transparent honeycombs consist of a plurality of cells that have a length / diameter ratio between about 2 and 10. 6. Sonnenheizgerat according to one of claims 3 to 5, characterized characterized in that the transparent honeycomb consists of a plurality of cells with a wall thickness in the range from about 0.002 to about 0.5 mm. 909807 / 1QS 2B35371 7. Sun heater according to one of the preceding claims, characterized in that the device for passing a fluid medium to be heated has a closed passage (18) for circulating the fluid through the housing (1O) and the passage at least in close proximity to the radiation-absorbing collector element (16) is arranged. 8. Sun heater according to claim 7, characterized in that that the heat trap (22) is adjacent to the front wall (12) and is arranged at a distance from the radiation-absorbing collector element (16). 9. Sun heater according to one of claims 1 to 6, characterized characterized in that the device for passing a fluid medium to be heated through has an inlet (34) and an outlet (36) in the housing (28) to form a flow path for the fluid are arranged, and that the radiation-absorbing Collector element (38) is gas-permeable and sits in the flow path. 1O. Sun heater according to claim 9, characterized in that that the heat trap (42) is arranged above the radiation-absorbing collector element (38). 909807/1051 11. Sun heater according to claim 9, characterized in that that the heat trap at a distance from the radiation-absorbing Collector element and the front wall is arranged. 12. Sun heater according to claim 9, characterized in that that the heat trap (42) sits adjacent to the front wall (30). 13. Sun heater according to one of the preceding claims, characterized in that the walls (26, 46)
of the cells (24, 44) substantially perpendicular to the
Front wall (12, 3O) run. 14. Sun heater according to one of the preceding claims, characterized in that the heat trap (22,
42) is held in at least firm mechanical contact with the front wall (12, 30). 15. Sun heater according to one of the preceding claims, characterized in that the heat trap (22,
42) is connected to the front wall (12, 3O). 16. Sun heater according to one of claims 1 to 14, characterized characterized in that the heat trap (22, 42) and the front wall (12, 3O) are integrally formed. S09807 / 10S1 17. Sun heater according to one of the preceding claims, characterized in that the radiation-absorbing collector element (16, 38) is essentially is arranged parallel to and at a distance from the front wall (12, 30). 18. Sun heater according to one of claims 1 to 16, characterized in that the radiation-absorbing Collector element is arranged in non-parallel relationship to the front wall. 19. Sun heater according to one of claims 9 to 18, characterized in that the radiation-absorbing Collector element (38) a porous, opaque mat made of pressed fibers, screen fabric, punched screen material and / or reticulated foam. 20. Sun heater according to one of the preceding claims, characterized in that the housing (1O, 28) a bottom wall (14, 32) and opposing side walls made of metal are. " 21. Sun heater according to one of the preceding claims, characterized in that an insulation layer (20, 40) is provided adjacent to the bottom wall (14, 32) is. 909807/1051 22. Sonnenheizgerat according to one of claims 1 to 19, characterized in that the housing (10, 28) has a bottom wall (14, 32) and opposite one another Has side walls which are made of a rigid insulating material.