Abstract:
An invention proposes a solar radiation absorbing panel that serves preferably for air heating, 
     The solar radiation absorbing panel is constructed from two metal sheets. 
     The metal sheets are sealingly joined along their edges. 
     The metal sheets are provided with mechanical or magnetic means; the both metal sheets are interlocked by these means along some lines or at some spots. 
     This ensures diminishment of buckling these sheets under operating pressure and establishing of a certain distance between them with small deviations with respect to its average value. 
     The outer side of one metal sheet is coated with a black or selective paint absorbing solar radiation.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0001]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0002]    Usage of flat plate solar collectors for immediate air heating presents attractive solution for many applications: heating of dwellings; air conditioning systems, which operate with usage of liquid or solid desiccants; drying processes in industry and agriculture. 
         [0003]    These flat plate solar collectors can operate with low overpressure with respect to the ambient atmospheric pressure. 
         [0004]    It allows in turn constructing solar radiation an absorbing panel for these solar collectors as two metal sheets, which are positioned for the most part in parallel at a distance of few millimeters and sealingly mutually joined along their edges. Two terminal sections of one metal sheet are provided with openings, which are, in turn, in fluid communication with headers provided with inlet and outlet connections. In such a way, the internal space formed between the metal sheets and serving as a duct is in fluid communication with these inlet and outlet connections. 
         [0005]    The external side of the upper sheet is coated with black or selective paints absorbing solar radiation. 
         [0006]    These solar selective coatings are described, for example, in article: McDonald, G. E: “Spectral reflective properties of Black Chrome for use as a Solar Selective Coating”, Solar Energy Journal 17, 119 (1975). 
         [0007]    The solar radiation absorbing panel can be installed into a box with glazing its upper aperture and a thermal insulation of the box&#39;s bottom. 
         [0008]    Such solar radiation absorbing panel and its operation is described in the book: Frank Kreith and Jan Kreider PRINCIPLES OF SOLAR ENGINEERING, Hemispher Publishing Corporation, 1978, p. 231 and p. 446. 
         [0009]    However, this simple design of the solar radiation absorbing panel requires application of metal sheets with high rigidity in order to solve a problem of significant buckling of the metal sheets under internal operating pressure in the duct formed between these metal sheets. 
         [0010]    This buckling causes, in turn, diminishment of heat transfer coefficient for heat transfer from the air to the metal sheet absorbing solar radiation, and, as a result, it diminishes efficiency of the solar radiation absorbing panel. 
         [0011]    There are some US patents intended to solve this problem. 
         [0012]    U.S. Pat. No. 3,943,911 describes a solar heat exchanger, which comprises: A. a base and an extended surface thereon for facing frontward toward the sun, B. means communicating with said surface to conduct liquid to flow in dispersed condition adjacent said surface, and C. a sheet overlying said surface and spaced therefrom sufficiently closely to cooperate therewith for filming the flowing liquid, said sheet adapted to receive solar radiation for promoting heat transfer to the filmed and flowing liquid. 
         [0013]    U.S. Pat. No. 4,010,733 discloses a solar energy collector unit comprising: an expanded metal energy collector panel including an upper sheet and a lower sheet; a seam weld connecting said upper and lower sheets and defining a rectangular energy collecting area; a plurality of spaced spot welds within said rectangular energy collecting area, defining a plurality of fluid flow channels; fluid inflow means at one end of said rectangular energy collecting area, and fluid overflow means at the opposite end of said rectangular energy collecting area (Claim 7). 
         [0014]    U.S. Pat. No. 4,062,350 describes a solar water heating panel having a base sheet and a metallic absorber sheet affixed in close parallel relationship to one another. The water passes between the two sheets and is heated by solar heat transfer through the absorber sheet into the water. 
         [0015]    The spacing between the absorber sheet and the base sheet may be controlled by spacers which may be held externally or internally to the heater. For instance, a plurality of dimples may be formed in the absorber sheet and with the use of a metal base sheet the absorber sheet may be welded at each of these dimples to the base sheet. Likewise, the dimples may be located in the base sheet instead of the absorber sheet. Alternatively, a rubber or other corrosion resistant and flexible member may be placed between the absorber sheet and the base sheet at a plurality of locations and a rivet, nut and bolt or other fastening means passed through the assembly and tightened to prevent the leakage of water around the fastener. Still further, a plurality of polymeric or other corrosion resistant spacers may be adhered to the inner surfaces of the absorber sheet and base sheet to hold the two sheets in a spaced apart parallel relationship. 
         [0016]    It should be noted that U.S. Pat. No. 1,250,260 describes application of rivets as spacers for two parallel metal sheets of a solar radiation absorbing panel. 
         [0017]    U.S. Pat. No. 4,327,707 describes a flat plate collector that employs high performance thin films. In the preferred form, the apparatus features a substantially rigid planar frame. A thin film window is bonded to one planar side of the frame. An absorber of laminate construction is comprised of two thin film layers that are sealed perimetrically. The layers define a fluid-tight planar envelope of large surface area to volume through which a heat transfer fluid flows. Absorber is bonded to the other planar side of the frame. The thin film construction of the absorber assures substantially full envelope wetting and thus good efficiency. The window and absorber films stress the frame adding to the overall strength of the collector. 
         [0018]    The films comprising the absorber are further bonded together at a plurality of locations across their surface so as to maintain a high degree of parallelism between said films as said heat transfer fluid flows through the envelope, thereby assuring that a substantial portion of the surface of the films is wetted (Claim 3). 
         [0019]    However, this patent does not disclose means for such bonding “at the plurality of locations”. 
         [0020]    U.S. Pat. No. 4,396,007 discloses a solar heat exchanger having a mesh sandwiched between two thin films for transfer of radiant solar energy to a fluid drawn through the mesh by suction. 
         [0021]    U.S. Pat. No. 4,474,172 discloses a solar water heating panel and method of constructing such a solar panel from a pair of thin sheets bonded together around their peripheral edges and having at least one of the sheets formed with resiliently flexible areas defined by a plurality of abutting concave hexagonal areas or zones. The center of each hexagonal zone is formed as a dimple, concave with respect to the opposite sheet, whose radius of curvature is greater than the radius of an inscribed circle within said zone. The abutting zones between each hexagonal zone are formed convex relative to the opposite sheet and have a radius less than that of an inscribed circle. In a preferred form, the sheets are joined together at the center of alternate spaced-apart hexagonal areas. In this way, except for the centers bonded near the panel edges, each joined hexagonal center is surrounded by six unjoined areas to form both transverse and longitudinal flow passages through the panel. 
         [0022]    U.S. Pat. No. 8,985,097 describes a device and method of its production for a micro-channel thermal absorber to be used as a solar thermal collector, heat collector, or heat dissipater, extruded or continuously cast in one piece or in modular segments from a metal, plastic, or glass and assembled into panels of different structures seamlessly integrated into the envelope of a building as covering layers or structural elements. The micro-channel thermal absorber comprises an active plate, a back plate adjacent to the active plate, and a plurality of micro-channel walls arranged substantially perpendicular to the active plate and the back plate to define a plurality of fluid transport micro-channels configured to allow fluid flow there-along, wherein the micro-channel walls constitute supporting elements between the active plate and the back plate to provide structure. 
         [0023]    U.S. Pat. No. 9,267,710 discloses solar thermal collectors, solar heating systems, and thin plate heat exchangers and absorbers. The thin plate heat exchangers and absorbers may be used for solar applications and/or non-solar applications. In an exemplary embodiment, a solar thermal collector generally includes a first layer comprising polymer and configured to allow sunlight to pass therethrough. A second layer comprises polymer and is configured to absorb thermal energy from sunlight. The second layer includes edges heat sealed to edges of the first layer. A permeable core is disposed between the first and second layers. In operation, a heat transfer fluid may flow through the permeable core and directly contact the second layer, whereby thermal energy is transferrable from the permeable core and the second layer to the heat transfer fluid. 
         [0024]    In addition, there are U.S. Pat. Nos. 4,140,103, 4,205,658, 4,205,662, 4,211,213, 42,865,823, 4,292,955, 4,455,999, 4,473,066, 6,526,965 and 9,127,860, which solve the problem of buckling by application of corrugated sheets or application of sheets provided with sets of ribs. 
         [0025]    It causes, in turn, a complicated problem of fluid communication between ducts formed by such corrugated sheets with headers arranged at the terminal sections of the duct and makes these solar radiation absorbing panels very expensive. 
         [0026]    On the other hand, these patents do not allow to apply plates from cheap thin tin or galvanized steel plates for manufacturing of solar radiation absorbing panels, which can be used in construction of solar collectors. 
       BRIEF SUMMARY OF THE INVENTION 
       [0027]    An invention proposes a solar radiation absorbing panel that serves preferably for air heating. However, the proposed solar radiation absorbing panel can serve for water heating. 
         [0028]    The solar radiation absorbing panel is constructed from two metal sheets. 
         [0029]    One of these metal sheets is provided with two sets of openings at its opposite terminal sections. The opposite terminal sections are joined sealingly with two headers provided with inlet and outlet connections. In the case of application of the solar radiation absorbing panel for air heating, it is possible to substitute the header with its inlet connection by a fan installed immediately on the metal sheet in such a manner that the aperture of the fan overlaps completely the openings serving for ingress of the air. 
         [0030]    The metal sheets are sealingly mutually joined along their edges by soldering or roll seaming. 
         [0031]    The distance between the metal sheets is ensured by pairs of profiles, which are arranged on the inner sides of the metal sheets longitudinally or transversely to direction of fluid motion in the duct formed between these sheets; these profiles are fastened on the metal sheets by soldering or gluing and the opposite profiles of each pair of the profiles are brought in their interlocking; it diminishes significantly buckling of the metal sheets under operating pressure of the fluid. 
         [0032]    There are several versions of different profiles, which provide interlocking of the opposite metal sheets along lines or in some spots. 
         [0033]    In a first embodiment the both profiles in one interlocking pair are V-shaped profiles. 
         [0034]    After placement of two sheets in parallel at closest distance, when the parallel profiles are turned inward, the sheets are shifted in parallel with following interlocking the V-shaped profiles of each pair. 
         [0035]    In a similar technical solution, the both metal sheets are provided with louvers protruding inward the space between these metal sheets and the openings of these louvers are closed sealingly from the outsides by metal strips by soldering or gluing. 
         [0036]    In another version, the both profiles of one pair of the profiles to be interlocked are U-shaped. 
         [0037]    In an additional version, the both profiles are Z-shaped profiles (Zee beams) with webs, which are situated perpendicularly to their lower and upper shelves. 
         [0038]    In the case, when the profiles described above are oriented transversely to direction of fluid flow in the duct between the metal sheets, the protruded shelves of the profiles are toothed and placed in such a manner on the metal sheets, that in the shifted state and their interlocking, their teeth are mutually overlapped and do not prevent fluid motion via these protruded shelves. Analogically, the protruded shelves of each pair of the profiles described above can be provided with perforations. 
         [0039]    There are two additional versions of pairs of profiles fastened on the opposite metal sheets longitudinally or transversally to direction of fluid (gas or liquid) flowing in the duct formed between these metal sheets. One profile of a pair, which is intended to be interlocked, is an angle section with its protruded shelf provided with longitudinal rectangular perforations and the second one is an angle section with a blunt angle between its shelves, wherein the protruded shelf is toothed. 
         [0040]    In such a way, in the state of interlocking of the profiles of one pair, the teeth of the protruded shelf of the second profile are introduced into the rectangular perforations of the first profile. 
         [0041]    In this case, the angle section with the rectangular perforations may be substituted by a corrugated strip with rectangular corrugations. 
         [0042]    It should be noted that it is possible to apply some other combinations of the profiles described above as pairs with ability of their interlocking. 
         [0043]    In another version, there are two metal sheets from a ferromagnetic metal; one of these metal sheets is provided with cylindrical dimples, which are protruded outwards relatively to the internal duct formed between the metal sheets. 
         [0044]    Cylindrical permanent magnets are disposed in the cylindrical dimples and partly protrude from them (the height of these cylindrical permanent magnets is larger than the depth of the cylindrical dimples, and their edges, which are inserted into the cylindrical dimples, are chamfered). 
         [0045]    In such a way, these cylindrical permanent magnets attract the opposite ferromagnetic metal sheet ensuring diminishment of buckling these metal sheets under operating pressure and provide small deviations regarding a certain average distance between them. 
         [0046]    In an additional version, the cylindrical dimples of one ferromagnetic sheet are turned inward the internal duct between the two ferromagnetic sheets and the ring permanent magnets are placed around of these cylindrical dimples. The internal edges of the ring permanent magnets facing the metal sheet, which is provided with the dimples, are preferably chamfered. The dimples may be shaped in this case as spherical dimples. 
         [0047]    These ring permanent magnets are protruding regarding the bottoms of the cylindrical dimples and they attract the opposite ferromagnetic metal sheet. 
         [0048]    In the third version of application of permanent magnets for interlocking of two opposite ferromagnetic sheets, there is a frame with a set of parallel metal strips installed in it; the metal strips are fabricated from a spring metal and each metal strip is provided with some omega-shaped sections of the same orientation. 
         [0049]    We determine a diameter of the omega-shaped section as the diameter of a maximum circle, which can be inscribed into the planar cross-section of the omega-shaped section in such a way that the center of this circle is found on the same side as the omega-shaped section itself relatively to the embouchure of the omega-shaped section. 
         [0050]    The cylindrical permanent magnets have diameter somewhat higher than the diameter of the omega-sections; in such a way these cylindrical permanent magnets are installed in the omega-sections and held in them by forces of elastic deformation of these omega-sections. 
         [0051]    At the same time the height of the cylindrical permanent magnets is larger than the width of the strips (the strips are installed in the frame in such a manner than their planes are perpendicular to the frame&#39;s plane). 
         [0052]    In this case, the frame with these strips and with the cylindrical permanent magnets is placed between two metal ferromagnetic sheets with following fabrication of the solar radiation absorbing panel as it was described above; i.e., sealingly joining of the both metal ferromagnetic sheets along their edges, when one of the metal ferromagnetic sheet is provided with openings at its opposite terminal sections, and following installations of headers provided with inlet and outlet connections. 
         [0053]    In such a way, the cylindrical or ring permanent magnets serve in these versions as spacers and, on the other hand, they diminish the buckling phenomena for the metal ferromagnetic sheets under operation pressure. 
         [0054]    The outer side of one metal sheet is coated with a black or solar selective paint absorbing solar radiation. 
         [0055]    In order to diminish buckling of the solar radiation absorbing panel as the result of the temperature difference between the upper and lower metal sheets, their internal sides may be coated with a black paint with high emission/absorption ability in the infrared range of the electromagnetic spectrum. 
         [0056]    There are hook-and-loop fasteners “Velcro”, which reminds some technical solutions proposed in this invention. In addition, there are 3M Dual Lock™ fasteners. 
         [0057]    However, the proposed pairs of profiles or permanent magnets in combination with dimples have substantial rigidity and interlocking of these profiles or permanent magnets with both opposite metal sheets is ensured additionally by joining the metal sheets along their edges; this prevents possibility of disengagement of these metal sheets. 
         [0058]    Such solar radiation absorbing panels can be used in flat plate solar collectors with or without glazing. In addition, such panels may be used for heat dissipation. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0059]      FIG. 1   a,    FIG. 1 b    and  FIG. 1 c    demonstrate correspondingly: an isometric view of an angle; one shelf of this angle is toothed and forms a blunt angle with the plane of the other shelf; an isometric view of an angle with rectangular perforations of its protruded shelf (with respect to plane of the metal sheet on which this angle is installed); an isometric view of a corrugated strip with rectangular corrugations. 
           [0060]      FIG. 2   a,    FIG. 2 b    and  FIG. 2 c    demonstrate isometric views of a V-shaped angle, a V-shaped toothed angle and a V-shaped angle with rectangular perforation of its one shelf. 
           [0061]      FIG. 2   d,    FIG. 2 e    and  FIG. 2 f    demonstrate isometric views of: an U-shaped profile ( FIG. 2 d   ), an U-shaped profile with rectangular perforations of its upper shelf ( FIG. 2 e   ) and an U-shaped profile ( FIG. 2 f   ), when one shelf of this U-shaped profile is toothed. 
           [0062]      FIG. 2   g,    FIG. 2 h    and  FIG. 2 i    demonstrate: a Z-shaped profile (Zee beam) with a web, which is situated perpendicularly to its lower and upper shelves ( FIG. 2 g   ); a Z-shaped profile (Zee beam), when its web and the upper shelf has rectangular perforations ( FIG. 2 h   ); a toothed strip with the L-shaped teeth ( FIG. 2 i   ). 
           [0063]      FIG. 3 a    and  FIG. 3 b    demonstrate the internal sides of the metal sheets with V-shaped toothed angles installed transversely to flow direction in a duct to be constructed from these metal sheets. 
           [0064]      FIG. 3 c    and  FIG. 3 d    demonstrate the internal side of the metal sheets with V-shaped angles installed longitudinally to flow direction in a duct, which is to be constructed from these metal sheets. 
           [0065]      FIG. 3 e    and  FIG. 3 f    demonstrate: the internal side of the lower metal sheet, which provided with louvers fabricated by slitting ( FIG. 3 e   ) and the transverse cross-section A-A ( FIG. 3 f   ) of this lower metal sheet, when the openings of these louvers are sealingly closed by metal strips. 
           [0066]      FIG. 3 g    and  FIG. 3 h    demonstrate: the internal side of the upper metal sheet, which provided with louvers fabricated by slitting ( FIG. 3 g   ) and the transverse cross-section B-B ( FIG. 3 h   ) of this lower metal sheet, when the openings of these louvers are sealingly closed by metal strips. 
           [0067]      FIG. 4  is an underside view of the assembled solar radiation absorbing panel. 
           [0068]      FIG. 5 a    and  FIG. 5 b    show transverse cross-sections of two opposite metal sheets with sets of V-shaped angles installed on their internal sides; these V-shaped angles are shown before and after their interlocking. 
           [0069]      FIG. 5 c    and  FIG. 5 d    show transverse cross-sections of two opposite metal sheets; one metal sheet is provided with a set of profiled toothed strips; their teeth form blunt angle with the strip plane just as it is shown in  FIG. 1   a;  a set of the perforated angles just as it shown in  FIG. 1 b    is installed on the other metal sheet; these metal sheets with their toothed strips and perforated angles are shown before and after their interlocking. 
           [0070]      FIG. 5 e    and  FIG. 5 f    show transverse cross-sections of two opposite metal sheets with two sets of Z-shaped profiles (Zee beams) just as it is shown in  FIG. 2   g;  these Z-shaped profiles are installed on both metal sheets with opposite direction of their lower and upper shelves; these Z-shaped profiles are shown before and after interlocking of their pairs. 
           [0071]      FIG. 5 g    and  FIG. 5 h    show transverse cross-sections of two opposite metal sheets; a set of profiled toothed strips just as it is shown in  FIG. 1 a    is installed on one metal sheet, and a set of corrugated strips just as it shown in  FIG. 1 c    is installed on the other metal sheet; these profiled toothed strips and corrugated strips are shown before and after their interlocking. 
           [0072]      FIG. 5 i    and  FIG. 5 j    show transverse cross-sections of two opposite metal sheets with two sets of U-profiled strips just as it is shown in  FIG. 2   g;  these U-profiled strips are installed on both metal sheets with opposite direction of their longitudinal shelves; these U-profiled strips are shown before and after their interlocking. 
           [0073]      FIG. 6  demonstrates a transverse cross-section A-A ( FIG. 4 ) of an assembled solar radiation absorbing panel, when the V-shaped angles are installed longitudinally to direction of a medium flow. 
           [0074]      FIG. 7   a,    FIG. 7   b,    FIG. 7 c    and  FIG. 7 d    demonstrate cross-sections and views from above of two opposite metal sheets, which serve for constructing a duct of a solar radiation absorbing panel; one of these metal sheets is provided with a set of cylindrical dimples. 
           [0075]      FIG. 8 a    and  FIG. 8 b    show longitudinal cross-sections of assembled solar radiation absorbing panels, as it is shown in  FIG. 4 , with cylindrical ( FIG. 8 a   ) or ring ( FIG. 8 b   ) permanent magnets serving as spacers and for interlocking two metal ferromagnetic sheets. 
           [0076]      FIG. 9 a    shows a planar view of a frame with a set of strips installed in it, when each of the strips is provided with omega-shaped sections. 
           [0077]      FIG. 9 b    and  FIG. 9 c    show the planar view and a cross-section A-A of the frame with the strips and cylindrical permanent magnets fastened in their omega-shaped sections. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0078]      FIG. 1   a,    FIG. 1 b    and  FIG. 1 c    demonstrate correspondingly: an isometric view of a strip provided with teeth forming a blunt angle with the strip plane; an isometric view an angle with rectangular perforations of its one angle section; an isometric view of a corrugated strip with rectangular corrugations. 
         [0079]      FIG. 1 a    comprises strip  101  and teeth  102  forming the blunt angle with the strip plane. 
         [0080]      FIG. 1 b    comprises an angle section  103 , an angle section  104  and rectangular perforations  105 . 
         [0081]      FIG. 1 c    comprises a corrugated strip  106  with rectangular corrugations  107 . 
         [0082]      FIG. 2   a,    FIG. 2 b    and  FIG. 2 c    demonstrate isometric views of a V-shaped angle, a V-shaped toothed angle and a V-shaped angle with rectangular perforation of its one shelf. 
         [0083]      FIG. 2 a    shows the isometric view of the V-shaped angle  200  with an angle shelf  201  and an angle shelf  202 . 
         [0084]      FIG. 2 b    shows an isometric view of the V-shaped toothed angle  208  with an angle shelf  203  and teeth  204 . 
         [0085]      FIG. 2 c    shows an isometric view of the V-shaped angle  209  with an angle shelf  205 , an angle shelf  206  and rectangular perforation  207 . 
         [0086]      FIG. 2   d,    FIG. 2 e    and  FIG. 2 f    demonstrate isometric views of: an U-shaped profile ( FIG. 2 d   ), an U-shaped profile with rectangular perforations of its upper shelf ( FIG. 2 e   ) and an U-shaped profile ( FIG. 2 f   ), where one shelf of this U-shaped profile is toothed. 
         [0087]      FIG. 2 d    shows U-shaped profile  210 , which comprises a lower shelf  211 , an upper shelf  212  and web  213 . 
         [0088]      FIG. 2 e    shows the U-shaped profile  214 , which comprises a lower shelf  215 , an upper shelf  216  and rectangular perforations  217 . 
         [0089]      FIG. 2 f    shows the U-shaped profile  218 , which comprises a lower shelf  219 , an upper teeth  220  and webs  221 . 
         [0090]      FIG. 2   g,    FIG. 2 h    and  FIG. 2 i    demonstrate: a Z-shaped profile (Zee beam) with a web, which is situated perpendicularly to its lower and upper shelves ( FIG. 2 g   ); a Z-shaped profile, when its web and the upper shelf have rectangular perforations ( FIG. 2 h   ); a toothed strip with the L-shaped teeth ( FIG. 2 i   ). 
         [0091]      FIG. 2 g    shows the Z-shaped profile  222  comprising a lower shelf  223 , an upper shelf  224  and web  225 , which is situated perpendicularly to the lower and upper shelves  223  and  224 . 
         [0092]      FIG. 2 h    shows the Z-shaped profile  226  comprising a lower shelf  227 , an upper shelf  228 , web  229  and perforations  230 . 
         [0093]      FIG. 2 i    shows the Z-shaped profile  231  comprising a lower shelf  232  and L-shaped teeth  233 . 
         [0094]      FIG. 3 a    and  FIG. 3 b    demonstrate the internal sides of metal sheets  301  and  306  with V-shaped toothed angles installed transversely to flow direction in a duct, which is to be constructed from these metal sheets. 
         [0095]      FIG. 3 a    shows the metal sheet  301 , V-shaped toothed angles  302  with teeth  303 ; these V-shaped toothed angles  302  are installed on the metal sheet  301 ; openings  304  and  305  are situated at the terminal sections of the metal sheet  301 . 
         [0096]      FIG. 3 b    shows the metal sheets  306  and V-shaped toothed angles  307  with teeth  308 . 
         [0097]      FIG. 3 c    and  FIG. 3 d    demonstrate the internal side of the metal sheets  309  and  313  with V-shaped angles installed longitudinally to flow direction in a duct to be constructed from these metal sheets. 
         [0098]      FIG. 3 c    shows metal sheet  309  and V-shaped angles  310 ; these V-shaped angles  310  are installed on the metal sheet  309 ; openings  311  and  312  are perforated in the terminal sections of the metal sheet  309 . 
         [0099]      FIG. 3 d    shows metal sheets  313  and V-shaped angles  314 ; these V-shaped angles  314  are installed on the metal sheet  313 . 
         [0100]      FIG. 3 e    and  FIG. 3 f    demonstrate: the internal side of a lower metal sheet, which provided with louvers fabricated by slitting ( FIG. 3 e   ), and the transverse cross-section A-A ( FIG. 3 f   ) of this lower metal sheet, when the openings of these louvers are sealingly closed by metal strips. 
         [0101]      FIG. 3 e    comprises: a metal sheet  315 ; openings  316  and  317 ; louvers  318 . 
         [0102]      FIG. 3 f    comprises: the metal sheet  315 ; louvers  318 ; strips  319 . 
         [0103]      FIG. 3 g    and  FIG. 3 h    demonstrate: the internal side of the upper metal sheet, which provided with louvers fabricated by slitting ( FIG. 3 g   ), and the transverse cross-section B-B ( FIG. 3 h   ) of this lower metal sheet, when the openings of these louvers are sealingly closed by metal strips. 
         [0104]      FIG. 3 g    comprises: a metal sheet  320 ; louvers  321 . 
         [0105]      FIG. 3 h    comprises: the metal sheet  320 ; louvers  321 ; strips  322 . 
         [0106]      FIG. 4  is the underside view of an assembled solar radiation absorbing panel. 
         [0107]    It comprises: an upper sheet  401 ; a lower sheet  402 ; a soldering seam  403 ; header  404 ; openings  405 ; an inlet connection  406 ; flange  407 ; header  408 ; openings  409 ; an outlet connection  410 ; flange  411 . 
         [0108]      FIG. 5 a    and  FIG. 5 b    show a transverse cross-section of two opposite metal sheets with sets of V-shaped angles installed on their internal surfaces longitudinally to direction of a medium flow; these V-shaped angles are shown before and after their interlocking. 
         [0109]      FIG. 5 a    and  FIG. 5 b    comprise: an upper metal sheet  501 ; a lower metal sheet  502 ; V-shaped angles  503  installed on the upper metal sheet  501 ; V-shaped angles  504  installed on the lower metal sheet  502 . 
         [0110]    It should be noted that in the case of application of the V-shaped toothed angles and/or the V-shaped angles with the rectangular perforations, as it was described above, drawings of transverse cross-sections of two opposite metal sheets have similar views. 
         [0111]      FIG. 5 c    and  FIG. 5 d    show a transverse cross-section two opposite metal sheets; one metal sheet is provided with a set of profiled toothed strips; their teeth form blunt angle with the strip plane just as it is shown in  FIG. 1   a;  a set of the perforated angles just as it shown in  FIG. 1 b    is installed on the other metal sheet; these metal sheets with their profiled strips are shown before and after their interlocking. 
         [0112]      FIG. 5 c    and  FIG. 5 d    comprise: the upper metal sheet  505  with the set of the profiled toothed strips  506  fastened on it; the lower metal sheet  507  with the set of the perforated angles  508  fastened on it. 
         [0113]      FIG. 5 e    and  FIG. 5 f    show transverse cross-section of two opposite metal sheets with two sets of Z-shaped profiles (Zee beams) just as it is shown in  FIG. 2   g;  these Z-shaped profiles are installed on the both metal sheets with opposite direction of their upper and lower shelves; the Z-shaped profiles are shown before and after their interlocking. 
         [0114]      FIG. 5 e    and  FIG. 5 f    comprise: the upper metal sheet  510  with the set of the Z-shaped profiles  511  fastened on it; the lower metal sheet  512  with the set of Z-shaped profiles  513  fastened on it. 
         [0115]      FIG. 5 g    and  FIG. 5 h    show transverse cross-sections of two opposite metal sheets; a set of profiled toothed strips just as it is shown in  FIG. 1 a    is installed on one metal sheet; a set of corrugated strips just as it shown in  FIG. 1 c    is installed on the other metal sheet; the profiled toothed strips and the corrugated strips are shown before and after their interlocking. 
         [0116]      FIG. 5 g    and  FIG. 5 h    comprise: the upper metal sheet  514  with the set of the profiled toothed strips  515  installed on it; the lower metal sheet  516  with the set of the corrugated strips  517 . 
         [0117]      FIG. 5 i    and  FIG. 5 j    show transverse cross-sections of two opposite metal sheets with two sets of U-shaped profiles just as it is shown in  FIG. 2   g;  these U-shaped profiles are installed on the both metal sheets with opposite directions of their upper and lower sections; these U-shaped profiles are shown before and after their interlocking. 
         [0118]      FIG. 5 i    and  FIG. 5 j    comprise: the upper metal sheet  518  with the set of the U-shaped profiles  519  installed on it; the lower metal sheet  520  with the set of the U-shaped profiles  521  installed on it. 
         [0119]      FIG. 6  demonstrates a transverse cross-section A-A (see  FIG. 4 ) of an assembled solar radiation absorbing panel, when the V-shaped angles are installed longitudinally to direction of a medium flow. 
         [0120]      FIG. 6  comprises: an upper metal sheet  601 ; a lower metal sheet  602 ; flange  603  of the lower metal sheet  602 ; V-shaped angles  604  installed on the upper metal sheet  601 ; V-shaped angles  605  installed on the lower metal sheet  602 ; header  606 , its flange  607  and a inlet connection  608 ; a solar radiation absorbing coating  609 . 
         [0121]      FIG. 7   a,    FIG. 7   b,    FIG. 7 c    and  FIG. 7 d    demonstrate cross-sections and views from above of two opposite metal sheets, which serve for constructing a duct of a solar radiation absorbing panel; one of these metal sheets is provided with a set of cylindrical dimples. 
         [0122]      FIG. 7 a    and  FIG. 7 b    show the cross-section and the view from above of a metal sheet  701 . 
         [0123]      FIG. 7 c    and  FIG. 7 d    show the cross-section and the view from above of a metal sheet  702  with cylindrical dimples  703 . 
         [0124]      FIG. 8 a    and  FIG. 8 b    show longitudinal cross-sections of two assembled solar radiation absorbing panels, as it is shown in  FIG. 4 , with cylindrical ( FIG. 8 a   ) or ring ( FIG. 8 b   ) magnets serving as spacers and for interlocking of two metal ferromagnetic sheets. 
         [0125]      FIG. 8 a    comprises: an upper sheet  801  from ferromagnetic metal with its external surface covered by a solar radiation absorbing coating  802 ; a lower sheet  803  from ferromagnetic metal; this lower sheet is provided with a set of cylindrical dimples  804  directed outwards; a set of cylindrical magnets  805 , which are situated in the cylindrical dimples  804  in such a way that the upper sections of the cylindrical magnets  805  are protruded from the plane of the lower sheet  803 ; header  806  with its flange  807 ; an inlet connection  808 ; header  809  with its flange  810 ; an outlet connection  811 ; openings  812  and  813  in the terminal sections of the lower sheet  803 . 
         [0126]      FIG. 8 b    comprises: an upper sheet  823  from ferromagnetic metal with its external side covered by a solar radiation absorbing coating  824 ; a lower sheet  814  from ferromagnetic metal; this lower sheet  814  is provided with a set of cylindrical dimples  815  directed inwards; a set of ring magnets  816 , which are situated around the cylindrical dimples  815  in such a way that the upper sections of the ring magnets  816  are protruded from the plane of the tops of dimples  815 ; header  817  with its flange  818 ; an inlet connection  819 ; header  820  with its flange  821 ; an outlet connection  822 ; openings  825  and  826  in the terminal sections of the lower sheet  814 . 
         [0127]      FIG. 9 a    shows a planar view of a frame with a set of strips installed in it, when each of the strips is provided with omega-shaped sections. 
         [0128]    It comprises: frame  901 ; strips  902  with omega-shaped sections  903 . 
         [0129]      FIG. 9 b    and  FIG. 9 c    show the planar view and a cross-section A-A of the frame with the strips and cylindrical permanent magnets fastened in their omega-shaped sections. 
         [0130]    It comprises: frame  901 ; strips  902  with omega-shaped sections  903 ; the cylindrical permanent magnets  904 .