Patent Publication Number: US-2012037151-A1

Title: Solar collector

Description:
The present invention relates to a solar collector for converting solar radiation into heat and to transfer the latter with the maximum possible efficiency to a fluid heat transferring means (e.g. water or air) whereby the heat can be utilised in a domestic or industrial application, for example to heat a domestic hot water or central heating system. 
     A solar collector typically comprises a number of elongate tubes containing a radiation absorbing plate for absorbing solar radiation in contact with a pipe through which the fluid to be heated can be passed or within which is contained a working fluid for transferring heat to the fluid to be heated. The radiation absorbing plate and at least a portion of the pipe are enclosed within an evacuated radiation transparent enclosure to prevent heat loss. 
     In one type of solar collector, known as the direct flow type, the fluid to be heated flows through the pipe in contact with the plate for direct conduction of heat between the plate and the fluid. In one type of direct flow collector, the fluid to be heated flows in a concentric manner through the elongate tube. The solar collector further comprises a heat collection manifold containing a fluid to be heated and having at least one solar tube receiving aperture therein for insertion of an end of each elongate tube to enable the fluid to be heated to pass into and out of the pipe of each elongate tube. The manifold is typically provided with inlet and outlet connections. In one case the input fluid to be heated passes along the outer concentric chamber to a distal end of the elongate tube and returns along the inner concentric flow path where it outputs into the manifold flow chamber. In another case, the input flow passes along the inner concentric chamber to a distal end where it returns along the outer concentric flow path where it outputs into the manifold flow chamber. 
     There is a need for a solar collector in which the separate elongate tubes and the heat collection manifold are readily assembled on site and capable of taking up the tolerances required without risk of damage or leakages. In addition, it is necessary that the component parts be easily replaceable. 
     STATEMENTS OF INVENTION 
     According to the invention there is provided a solar collector assembly comprising:
         a solar absorbing tube having an evacuated radiation-transparent enclosure;   a radiation absorber within the tube;   an elongate outer conduit for a heat transfer medium extending through the tube and being in thermal contact with the radiation absorber;   an inner conduit extending through the outer conduit and being positioned within the outer elongate conduit to define an elongate internal flow passage for the flow of heat transfer medium;   a manifold having a heated fluid passageway and a cold fluid passageway;   the outer conduit having an end region extending into the manifold so that the passageway defined between the outer conduit and the inner conduit is in fluid communication with the cold fluid passageway of the manifold;   the inner conduit extending beyond the end region of the outer conduit into the heated fluid passageway of the manifold; and   a clip for retaining the inner conduit in spaced-apart relation to the end region of the outer conduit, the clip comprising a generally circular base which engages with the inner surface of the end region of the outer conduit the base having a plurality of inwardly extending teeth which engage with the outer wall of the inner conduit, the teeth being at least partially resilient and being spaced-apart to allow heat exchange fluid to pass between the teeth.       

     The invention also provides a clip for retaining the inner conduit in spaced-apart relation to the end region of the outer conduit, the clip comprising a generally circular base which engages with the inner surface of the end region of the outer conduit the base having a plurality of inwardly extending teeth which engage with the outer wall of the inner conduit, the teeth being at least partially resilient and being spaced-apart to allow heat exchange fluid to pass between the teeth. 
     In one embodiment the teeth are inclined inwardly with respect to the circumference of the base. 
     In a preferred embodiment the base has a longitudinally extending outer wall. The outer wall is preferably of generally cylindrical shape. 
     In one embodiment the teeth extend inwardly at one end of the outer wall. 
     In one case there are three equi-spaced-apart teeth. In another case there are four equi-spaced-apart teeth. 
     In one embodiment the thickness of at least some of the teeth is reduced at the inner free end thereof. 
     The clip may be of stainless steel material. 
     In the invention, the inner concentric chamber is held in its concentric position within the outer concentric chamber by a resilient star-clip. The resilient star-clip is further provided with a plurality of retaining teeth or tags that are dimensioned such that they provide both a strong interference fit with the inner concentric chamber and occlusions such that the star-clip additionally provides a plurality of flow paths without restriction to the heat-transfer fluid. 
     Additionally, the resilient star-clip is provided with a peripheral wall that provides additional structural support to the softer bellow material into which the clip is inserted. 
     The base of the clip engages with the inner surface of the end region of the outer conduit to ensure that any movement of the inner pipe in the longitudinal direction is prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective sectional view of a tubular solar collector; 
         FIG. 2  is a cross-section on the line II-II of  FIG. 1  of a solar collector tube of the direct flow type; 
         FIG. 3  is an exploded perspective view showing a retaining clip and an inner conduit (flow pipe); 
         FIG. 4  is a perspective view showing the clip attached to the inner flow pipe; 
         FIGS. 5 to 8  are enlarged perspective views of the clip; 
         FIG. 9  is an end-on planar view of the clip; 
         FIG. 10  is an end-on planar view of the clip and inner flow pipe assembly highlighting the fluid flow conduits through the assembly; 
         FIG. 11  is an exploded perspective view of the end-fitting of a solar collector tube of the direct flow type utilising the clip; 
         FIG. 12  is an exploded perspective view of the end-fitting of a solar collector tube of the direct flow type showing the clip attached to the inner chamber elongate tube; 
         FIG. 13  is a perspective view of the end-fitting of a solar collector tube of the direct flow type utilising the clip; 
         FIG. 14  is a planar cross-sectional view of the clip and the inner flow pipe prior to assembly; 
         FIG. 15  is a planar cross-sectional view of the clip and the inner flow pipe after assembly; 
         FIG. 16  is a planar cross-sectional view of the clip and the inner flow pipe assembly prior to insertion into the solar tube end fitting; 
         FIG. 17  is a planar cross-sectional view of the clip and the inner flow pipe assembly after insertion into the solar tube end fitting; 
         FIG. 18  is an exploded view of the clip and the end region of the outer flow pipe; 
         FIG. 19  is a view of the end region of the outer flow pipe with the clip in place; and 
         FIG. 20  is an enlarged view of a corner detail of the assembly of  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     As illustrated in  FIG. 1  a solar collector assembly of the direct flow type comprises a solar absorbing tube  1  comprising an evacuated radiation transparent enclosure  8  enclosing an absorbing section  9 , comprising a radiation absorbing plate  10  for absorbing solar radiation and an elongate tube  11 , containing a working fluid (heat transfer medium), in thermal contact with the radiation absorbing plate  10 . The elongate tube  11  contains a concentrically positioned inner pipe  12  thereby forming two concentric internal flow passageways  13 ,  14  for the flow of a fluid to be heated. The elongate tube  11  extends out of one end of the solar absorbing tube  1  and into an end fitting  5  wherein an annular outer passageway  13  of the elongate tube  11  communicates with a cold water inlet stream within a manifold chamber  3  of a manifold  2  and the inner passageway  14  of the elongate tube  11  communicates with a hot water outlet stream within the manifold chamber  3 , the water passing from the annular outer passageway  13  to the inner passageway  14  via a flow path provided at a distal end of the elongate tube  11 . The end fitting  5  is inserted into a manifold flange  7  in order to facilitate the communication of the annular outer passageway  13  and the inner passageway  14  with the cold water inlet stream and the hot water outlet stream respectively, within the manifold chamber  3  of a manifold  2 . A resilient clip  6  is used to secure the tube into its fitted position and to maintain the tube in its fitted position under operational conditions. 
     The inner conduit  12  extends beyond the end fitting  5  of the outer conduit  11  into the heated fluid passageway of the manifold  2 . A clip  20  for retaining the inner conduit  12  in spaced-apart relation to the end fitting  5  of the outer conduit  11  comprises a generally circular base  24  which engages with the inner surface of the end fitting  5  of the outer conduit  11 . The base  24  has a plurality of inwardly extending equi-spaced teeth  23  which engage with the outer wall of the inner conduit  12 . The equi-spaced teeth  23  are at least partially resilient and are spaced-apart to allow heat exchange fluid to pass between the equi-spaced teeth  23 . The equi-spaced teeth  23  are inclined inwardly with respect to circumference of the base  24 . 
     In a particularly preferred embodiment the circular base  24  has a longitudinally extending outer wall  22 . The outer wall  22  is preferably of generally cylindrical shape. The equi-spaced teeth  23  extend inwardly at one end of the outer wall  22 . 
     Preferably there are at least three equi-spaced teeth  23 . In this case there are four equi-spaced-apart teeth  23 . The thickness of at least some of the equi-spaced teeth  23  is reduced at the inner free end thereof. The clip may be of stainless steel material. 
     The clip  20  is attached onto the inner conduit  12  and held in position by an interference fit between the equi-spaced teeth  23  and the outer surface of the inner conduit  12 . The equi-spaced teeth  23  of the clip  20  are angled in a preferred direction to facilitate easy assembly in a preferred direction but resistance against removal in either direction. 
     The assembly consisting of the clip  20  attached to the inner conduit  12  is inserted into the outer conduit  11  and the resilient clip  20  rests upon an internal circumferential protrusion  41  on the internal surface of a one-piece flexible bellow assembly  31 . The clip  20  holds the inner conduit  12  in a concentric position and ensures that the distal end of the inner conduit  12  does not come into contact with the distal end of the outer conduit  11  thereby ensuring a flow of the heating fluid. 
     The cyclindrical wall  22  of the clip  20  provides a strengthening circumferential base that forms a support structure around the outer diameter of the clip  20 . The clip  20  is further provided with a plurality of engagement tags or teeth  23  that create an interference fit with the inner conduit  12  when it is pressed over the inner conduit  12 . 
     The equi-spaced teeth  23  are designed such that they are folded to generate an inner circular clearance whose dimensional size is less in diameter that the outer diameter of the inner conduit  12  onto which the clip  20  is attached. The clip  20  is secured on to the inner conduit  12  by an interference between the equi-spaced teeth  23  and the inner conduit  12 . When the clip  20  is attached to the inner conduit  12  the occlusions  25  in the clip  20  provide fluid conduits to allow the passage of the thermal fluid and facilitates communication with the annular outer passageway  13  with the cold fluid passageway of the manifold chamber  3 . The concentrically positioned inner conduit  12  facilitates communication of the annular inner passageway  14  with the hot fluid passageway of the manifold chamber  3 . 
     The clip  20  is positioned at a defined distance from the end of the inner conduit  12  to ensure that the annular inner passageway  14  communicates with an inner annular flow conduit in the manifold chamber  3  and the annular outer passageway  13  communicates with an outer flow conduit in the manifold chamber  3 . 
       FIG. 11  to  FIG. 13  are perspective views of the end fitting of a solar absorbing tube  1  of the direct flow type illustrating a preferred method of assembly using the resilient clip  20 . 
     The end fitting  5  of a solar absorbing tube  1  if the direct flow type in a preferred embodiment comprises a one-piece flexible bellow assembly  31 , a resilient retaining clip  30  and a plurality of o-ring seals  29  located in the convolutions of the flexible bellow assembly  31 . 
       FIG. 11  is an exploded perspective view of the clip  20  and the solar tube end fitting  5  prior to assembly.  FIG. 12  shows the clip  20  attached to the inner conduit  12 .  FIG. 13  shows the assembly of the clip  20  and the inner conduit  12  when fully assembled into the solar tube end fitting  5 . 
       FIG. 14  to  FIG. 17  illustrate the assembly of the clip  20  to the inner conduit  12  and insertion into the solar tube end fitting  5  in cross-sectional planar view.  FIG. 14  shows the clip  20  and the inner conduit  12  prior to assembly. The equi-spaced teeth  23  of the clip  20  are angled to facilitate easy attachment to the inner conduit  12 . 
       FIG. 15  illustrates the engagement of the clip  20  to the inner conduit  12 . The equi-spaced teeth  23  generate an interference fit between the clip  20  and the inner conduit  12 , and the angled equi-spaced teeth  23  serve to ensure a firm engagement between the clip  20  and the inner conduit  12 . 
       FIG. 16  illustrates the clip  20  and inner conduit  12  assembly prior to insertion into the solar tube end fitting  5 . The solar tube end fitting  5  is provided with a flexible bellow assembly  31  that has an internal circumferential protrusion  41  upon which the clip  20  engages when in its fully home position as illustrated in  FIG. 17 . 
     The clip  20  and inner conduit  12  assembly are inserted concentrically into the flexible bellow assembly  31  on the solar tube end fitting  5 . 
       FIGS. 18 to 20  illustrate the assembly without the conduit  12  in place.  FIG. 18  illustrates the clip  20  prior to insertion into the end fitting  5 . 
       FIGS. 19 and 20  illustrates the finished assembly and the clip  20  resting in its final position by engaging with the internal circumferential protrusion  41  of the flexible bellow assembly  31 . The circumferential edge  42  engages circumferentially with the internal circumferential protrusion  41  of the flexible bellow assembly  31 . Additionally the extended side wall of the clip  20  circumferentially engage with the inner wall of the flexible bellow assembly  31  to provide additional rigidity and robustness to the flexible bellow assembly  31  in order to minimise damages to the flexible bellow assembly  31  during system installation. 
     The base of the clip engages with the inner surface of the end region of the outer conduit to ensure that any movement of the inner pipe in the longitudinal direction is prevented. 
     Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. 
     The invention is not limited to the embodiment hereinbefore described, with reference to the accompanying drawings, which may be varied in construction and detail.