Abstract:
A flat evacuated-tube solar collector includes two parallel collecting tubes, a plurality of parallel evacuated tubes perpendicularly installed between two collecting tubes. Each evacuated tube includes two distal tube sections and a middle section situated between the two distal tube sections, and the middle section is in a flat shape, and has a cross-sectional area greater than that of the distal tube sections. The flat evacuated tubes substitute the conventional fins soldered onto a flat panel solar collector to receive sunlight, while the characteristic of two distal ends of the evacuated tube having a smaller cross-section than the middle section maintains an appropriate spacing between the collecting tube and a connecting point of the evacuated tube to assure the structural strength of the collecting tube.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a solar collector, in particular to a flat evacuated-tube solar collector having evacuated tubes with a cross-section at the middle section greater than the cross-section at distal sections. 
       BACKGROUND OF THE INVENTION 
       [0002]    With reference to  FIG. 1 , a solar collector is a device capable of heating a working fluid by sunlight, and the solar collector generally comprises a plurality of parallel evacuated tubes  10 , two collecting tubes  20 / 30  coupled perpendicular to both ends of each evacuated tube  10  respectively, and the evacuated tubes  10  are provided for receiving sunlight. In general, a metal fin  40  is soldered to each evacuated tube  20 / 30 , or a fin  40  is soldered between two evacuated tubes  20 / 30 , and a working fluid at room temperature is entered from one of collecting tubes  30  and then diverted to each of the evacuated tubes  10  for exchanging heat with the evacuated tubes  10 , and finally exited from another collecting tube  20 . 
         [0003]    However, the conventional flat panel solar collector still has the following drawbacks. The thermal resistance at a contact between the fin  40  and the evacuated tube  10  is very large, and thus affecting the thermal conductivity adversely. In addition, the fin  40  is very thin, so that a significant drop of thermal conducting efficiency of the fin  40  usually occurs at both linear ends of the fin  40  in contact with the evacuated tube  10 , so that the wider the fin  40 , the smaller is the heat transfer of the evacuated tube  10  per unit area of the fin  40 . In present existing structural designs, the only improvement that can be made is to increase the number of evacuated tubes  10  in order to decrease the spacing between the evacuated tubes  10 , and thus decreasing the width of the fin  40  to enhance the thermal conducting efficiency of the fin  40 . However, such improvement still cannot overcome the problem of a large heat resistance at the contact between the fin  40  and the evacuated tube  10 . 
       SUMMARY OF THE INVENTION 
       [0004]    Therefore, it is a primary objective of the present invention to overcome the aforementioned problem by providing a flat evacuated-tube solar collector, characterized in that the evacuated tube has a middle section substantially in a flat shape, and the middle section has a cross-section greater than the cross-section of the distal tube sections of the evacuated tube. The flat shaped middle section receives sunlight by a maximum heat receiving area. Since the two distal tube sections have a cross-section smaller than that of the middle section, the evacuated tubes arranged adjacent to one another will not increase the number of connecting points between a collecting tube and the evacuated tubes. On the other hand, the invention guarantees an appropriate spacing between the connecting points to assure the structural strength of the collecting tube. 
         [0005]    To achieve the aforementioned objective, the present invention provides a flat evacuated-tube solar collector, comprising two collecting tubes and a plurality of evacuated tubes. The two collecting tubes are arranged in parallel to each other, and each of the collecting tube includes a plurality of connecting portions arranged parallel to one another and installed between the two collecting tubes, and each evacuated tube includes two distal tube sections and a flat middle section situated between the two distal tube sections, and the two distal tube sections of each evacuated tube are interconnected to one of the connecting portions of each collecting tube. 
         [0006]    Preferably, the flat evacuated-tube solar collector further comprises a seal structure installed between the connecting portion and the distal tube section interconnected to the connecting portion. 
         [0007]    Preferably, the seal structure is formed between the connecting portion and the distal tube section interconnected to the connecting portion by soldering. 
         [0008]    Preferably, the seal structure of the flat evacuated-tube solar collector includes a locking device and a baffle plate disposed at the distal tube section, and the locking device is movably sheathed on the distal tube section, and the baffle plate is disposed between the locking device and the connecting portion and abutted against the locking device, and the connecting portion includes a screw thread formed on an inner side of the connecting portion, and the locking device is secured to the screw thread to compress the baffle plate to forcibly seal the distal tube section and the connecting portion. 
         [0009]    Preferably, the baffle plate of the flat evacuated-tube solar collector abuts an inner side of the connecting portion. 
         [0010]    Preferably, the seal structure of the flat evacuated-tube solar collector includes a gasket installed between the distal tube section and the connecting portion. 
         [0011]    Preferably, the baffle plate of the flat evacuated-tube solar collector abuts the gasket. 
         [0012]    Preferably, the middle section of each evacuated tube of the flat evacuated-tube solar collector has a cross-section substantially in a flat shape. 
         [0013]    Preferably, the evacuated tube of the flat evacuated-tube solar collector is installed perpendicular to the collecting tube. 
         [0014]    Compared with the conventional flat panel water heater, the flat evacuated-tube solar collector of the present invention adopts a structural design with a flat middle section of the evacuated tube and a greater cross-section of the middle section than the cross-section of the distal tube section to overcome the problems of a high resistance of the soldered structure of the fin and the evacuated tubes, a decreasing thermal conducting effect as the distance between the fin and the evacuated tube increases, and an substantial increase of the weight of the flat evacuated-tube solar collector 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic view of a conventional solar collector; 
           [0016]      FIG. 2  is a perspective view of a flat evacuated-tube solar collector in accordance with a first preferred embodiment of the present invention; 
           [0017]      FIG. 3  is a schematic view of an operation state of a flat evacuated-tube solar collector in accordance with the first preferred embodiment of the present invention; 
           [0018]      FIG. 4  is a schematic view of an evacuated tube in accordance with the first preferred embodiment of the present invention; 
           [0019]      FIG. 5  is a schematic view of a distal tube section of an evacuated tube and a connecting portion of a collecting tube in accordance with the first preferred embodiment of the present invention; 
           [0020]      FIG. 6  is a perspective view of a flat evacuated-tube solar collector, showing the internal structure and appearance of the solar collector in accordance with a second preferred embodiment of the present invention; 
           [0021]      FIG. 7  is a schematic view of an evacuated tube in accordance with the second preferred embodiment of the present invention; 
           [0022]      FIG. 8  is a schematic view of a seal structure in accordance with the second preferred embodiment of the present invention; 
           [0023]      FIG. 9  is a cross-sectional view of a seal structure in accordance with the second preferred embodiment of the present invention; and 
           [0024]      FIG. 10  is a cross-sectional view of a seal structure in accordance with the second preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The details and technical contents of the present invention will become apparent with the description of the following preferred embodiments accompanied with the illustration of the related drawings as follows. However, the drawings are provided for the purpose of illustrating the present invention only, but not intended for limiting the scope of the invention. 
         [0026]    With reference to  FIG. 2  for a perspective view of a flat evacuated-tube solar collector in accordance with the first preferred embodiment of the present invention, the flat evacuated-tube solar collector comprises two collecting tubes  100 ,  200  and a plurality of evacuated tubes  300 . 
         [0027]    With reference to  FIGS. 2 and 3 , the collecting tubes  100 ,  200  are preferably made of metal and hollow, and the two collecting tubes  100 ,  200  are installed parallel to each other, and each collecting tube  100 ,  200  has an opening  120 ,  220  and a plurality of connecting portions  110 ,  210 , wherein the opening  120 ,  220  is provided for filling a working fluid into the flat evacuated-tube solar collector of the present invention. In this preferred embodiment, the working fluid is entered from the opening  220  of one of the collecting tubes  200  into the flat evacuated-tube solar collector of the present invention, and then heated, and finally discharged from the opening  120  of another collecting tube  100  to a liquid container. The connecting portions  110 ,  210  are arranged in a central-axis direction of the collecting tubes  100 ,  200  and disposed on a tube wall of each collecting tube  100 ,  200 , and preferably disposed opposite to each other and on the connecting portions  110 / 210  of two collecting tubes  100 ,  200  respectively. 
         [0028]    With reference to  FIGS. 2 ,  4  and  5 , each evacuated tube  300  is a hollow tube, preferably made of metal, and both ends of the evacuated tube  300  are connected perpendicular to the two collecting tubes  100 ,  200  respectively, and the plurality of evacuated tubes  300  are parallel to each other and disposed between the two collecting tubes  100 ,  200 . Each evacuated tube  300  has two distal tube sections  310 ,  320  and a middle section  330 , and the two distal tube sections  310 ,  320  are situated at both ends of each evacuated tube  300  respectively, and the middle section  330  is situated between the two distal tube sections  310 ,  320 . The middle section  330  has a cross-section substantially in a flat shape, and the distal tube section  310 ,  320  has a cross-section smaller than that of the middle section. Preferably, the distal tube section  310 ,  320  has a circular cross-section in a central-axis direction perpendicular to the evacuated tube, and the middle section  330  has a flat shaped (or elliptical shaped) cross-section perpendicular to the central-axis direction of the evacuated tube, and the long-axis direction of the elliptical shape is parallel to an aligning direction of the evacuated tube  300  (which is the central-axis direction of the collecting tube  100 ,  200 ). The structure of the evacuated tube  300  can be a metal tube which is a shrink tube disposed at a distal tube section  310 ,  320 , and the middle section  330  has a cross-section greater than that of the distal tube section  310 ,  320 , and the middle section  330  is compressed flatly to form the flat evacuated tube  300 . One of the distal tube sections  310  of each evacuated tube  300  is interconnected to a connecting portion  110  of one of the collecting tubes  100 , and another distal tube section  320  is interconnected to another connecting portion  210  of another collecting tube  200 , such that both ends of the evacuated tube  300  are interconnected perpendicular to the two collecting tubes  100 ,  200  respectively, and the plurality of evacuated tubes  300  are arranged in parallel to each other to achieve a maximum sunlight receiving area. 
         [0029]    In this preferred embodiment, a seal structure is formed between the distal tube section  310  and the connecting portion  110  preferably by soldering to maintain the tightness between the distal tube section  310  and the connecting portion  110 . 
         [0030]    With reference to  FIGS. 6 and 7  for a flat evacuated-tube solar collector in accordance with the second preferred embodiment of the present invention, the flat evacuated-tube solar collector comprises two collecting tubes  100 ,  200 , a plurality of evacuated tubes  300 , a plurality of seal structures and a gasket  500 . The structure and connecting relation of the collecting tube  100 ,  200  and the evacuated tube  300  are the same as those of the first preferred embodiment, and thus will not be repeated. The difference between the second preferred embodiment and the first preferred embodiment resides on that the seal structure is installed between the connecting portion  110 ,  210  and the distal tube section  310 ,  320 , and the seal structure includes a locking device  400  and a baffle plate  311 ,  321  installed at the distal tube section  310 ,  320 . 
         [0031]    With reference to  FIG. 7 , each distal tube section  310 ,  320  has a baffle plate  311 ,  321  installed thereon. Preferably, the baffle plate  311 ,  321  is integrally formed at an opening at an end of the distal tube section  310 ,  320 , but the present invention is not limited such arrangement only. In this preferred embodiment, the baffle plate  311 ,  321  is extended axially outward from the opening at an end of the distal tube section  310 ,  320  and installed around the opening at an end of the distal tube section  310 ,  320 . 
         [0032]    With reference to  FIGS. 8 to 10 , the locking device  400  is preferably in the shape of a hollow screw, and the locking device  400  has a sheathing hole  410  axially formed and penetrated through the locking device  400 . Preferably, the sheathing hole  410  is slightly greater than the external diameter of the distal tube section  310  and smaller than the external periphery of the baffle plate  311 , and the distal tube section  310  is passed through the sheathing hole  410 , such that the locking device  400  can be movably sheathed on the distal tube section  310  and abutted against the baffle plate  311 . The connecting portion  110  of the collecting tube  100  has a screw thread  111  formed on an inner side of the connecting portion  110 , and the locking device  400  is secured to the screw thread  111 . The baffle plate  311  is installed between the locking device  400  and the connecting portion  110 , so that when the locking device  400  is secured to the screw thread  111 , the baffle plate  311  is compressed to forcibly seal the distal tube section  310  and the connecting portion  110 . The gasket  500  is installed between the distal tube section  310  and the connecting portion  110 . In this preferred embodiment, the baffle plate  311  is situated at an opening at an end of the distal tube section  310  and abutted against the gasket  500 , such that when the locking device  400  compresses the baffle plate  311 , the opening at an end of the distal tube section  310  and the baffle plate  311  will compress the gasket  500  to enhance the tightness between the distal tube section  310  and the connecting portion  110 . 
         [0033]    In the flat evacuated-tube solar collector of the present invention, the flat shaped middle section  330  of the evacuated tube  300  and the cross-section of the middle section  330  being greater than the cross-section of the distal tube section  310 ,  320  assure that a reasonable spacing is maintained at each connecting point between each evacuated tube  300  and the collecting tube, and a maximum light receiving area can be obtained without requiring the structure of the fin. In addition, the evacuated tube  300  of the present invention adopts the conventional soldering method to connect the collecting tube  100 ,  200 , or a locking method to seal the collecting tube  100 ,  200  and the evacuated tube  300  or interconnect the evacuated tube with the collecting tube  100 ,  200 . 
         [0034]    While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.