Abstract:
A heat exchanger having a pair of header pipes each of which includes a U-shaped wall and a front wall connected thereto to define a hollow portion. The front wall has a plurality of arc-shaped portions and plane portions each of which is disposed between adjacent arc-shaped portions in the longitudinal direction of the header pipe. Each of the plane portions are provided with an elongated hole therethrough. A plurality of fluid tubes are disposed between the header pipes in fluid communication therewith via the elongated holes. A plurality of corrugated fins are disposed between the opposed outer surfaces of the fluid tubes. Thus, the pressure loss of refrigerant in the heat exchanger is very low.

Description:
This application is a division of application Ser. No. 07/724,905, filed Jul. 2, 1991, now U.S. Pat. No. 5,251,694 granted Oct. 12, 1993. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to heat exchangers, and more particularly, to a heat exchanger including header pipes each provided with an arc-shaped portion to reduce pressure loss. 
     BACKGROUND OF THE INVENTION 
     One prior art embodiment of a heat exchanger as described in Japanese Patent Application Publication No. 63-112065 is shown in FIGS. 1-3. As shown in the figures, condenser 50 includes a plurality of adjacent, essentially flat tubes 51 having an oval cross-section and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units 52 are disposed between adjacent tubes 51. Flat tubes 51 and fin units 52 jointly form heat exchange region 100. Cylindrical header pipes 53 and 54 are disposed perpendicular to flat tubes 51 and may have, for example, a clad construction. The diameter and length of header pipes 53 and 54 are substantially equal to the thickness and height, respectively, of heat exchange region 100. Accordingly, header pipes 53 and 54 protrude only negligibly relative to heat exchange region 100 when the heat exchanger structure is assembled. 
     As shown in FIG. 3, each of header pipes 53 and 54 includes outer tube 60 and inner tube 61. Outer tube 60 is preferably made of aluminum. Inner tube 61, made of a metal material, is brazed to the inner surface of outer tube 60. Outer tube 60 has a plurality of slots 62 disposed therethrough. Flat tubes 51 are fixedly connected to header pipes 53 and 54 and are disposed in slots 62 so that the open ends of flat tubes 51 communicate with the hollow interiors of header pipes 53 and 54. Inner tube 61 includes a plurality of portions 63 which define openings corresponding to slots 62. Portions 63 are brazed to the ends of flat tubes 51 and ensure that tubes 51 are hermetically sealed within header pipes 53 and 54 when the tubes are inserted in slots 62. 
     In operation, compressed refrigerant gas from an external compressor coupled to inlet union joint assembly 531 flows through the joint and into the upper cavity of header pipe 53. In header pipe 53, the refrigerant is distributed so that a portion of the gas flows through each of flat tubes 51 which is disposed above the location of partition wall 532, and into an upper portion of the upper cavity of header pipe 54. Thereafter, the refrigerant in the upper portion of the upper cavity of header pipe 54 flows downwardly into a lower portion of the upper cavity of header pipe 54. The refrigerant is distributed therein so that a portion of the refrigerant flows through each of flat tubes 51 disposed below the location of partition wall 532 and above the location of partition wall 542, and into an upper portion of the lower cavity of header pipe 53. The refrigerant in the upper portion of the lower cavity of header pipe 53 then flows downwardly into a lower portion of the lower cavity. At this point, the refrigerant is again distributed so that a portion of the refrigerant flows through each of flat tubes 51 disposed below the location of partition wall 542, and into the lower cavity of header pipe 54. As the refrigerant gas sequentially flows through flat tubes 51, heat from the refrigerant gas is exchanged with the atmospheric air flowing through corrugated fin units 52. The condensed liquid refrigerant in the lower cavity of header pipe 54 flows out of the cavity through outlet union joint assembly 541 and into an external receiver coupled to the joint assembly. 
     Another prior art embodiment of a heat exchanger as described in U.S. Pat. No. 4,615,385 is shown in FIG. 4. Each header pipe 53 and 54 has a plurality of slots 62 along one of its surfaces for receiving open ends of flat tubes 51. The surface portions of the header pipe between the slots 62 are shaped as outwardly extending convex domes 70 as shown in the FIG. 4. 
     In both of the above embodiments, open ends of flat tubes 51 extend considerably into the interiors of header pipes 53 and 54. Since the refrigerant introduced through inlet union joint assembly 531 flows in the longitudinal direction of header pipes 53 and 54, (i.e., perpendicular to flat tubes 51) the flow direction of the refrigerant has to turn suddenly to the open ends of flat tubes 51 to travel therethrough. 
     Accordingly, vortexes as shown by arrows A occur adjacent to the open ends of flat tubes 51. As a result, the pressure loss of the condenser is increased. In addition, according to the occurrence of vortexes, the flow speed of the refrigerant is reduced thereby necessitating the use of an excess volume of the refrigerant in the condenser. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide a heat exchanger in which the pressure loss is very low. 
     It is another object of the present invention to provide a heat exchanger in which the flow volume of the refrigerant can be reduced. 
     It is still another object of the present invention to provide a heat exchanger in which the capacity to receive a high pressure refrigerant therein is improved. 
     It is still another object of the present invention to provide a heat exchanger in which the strength in resisting deformation can be improved. 
     A heat exchanger according to the present invention comprises a pair of header pipes each of which includes a U-shaped wall and a front wall connected thereto to define a hollow portion. The front wall has a plurality of integrally formed arc-shaped portions and plane portions. The plane portions are disposed between adjacent arc-shaped portions in the longitudinal direction of the header pipe. Each plane portion is provided with an elongated hole therethrough. A plurality of fluid tubes are disposed between the header pipes in fluid communication through the elongated holes. A plurality of corrugated fins are disposed between opposed outer surfaces of the fluid tubes. 
     Further objects, features and other aspects of this invention will be understood from the following detailed description of the preferred embodiment of this invention with reference to the annexed drawings. 
    
    
     BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is an elevational view of a condenser in accordance with the prior art. 
     FIG. 2 is a perspective view of certain elements of the condenser as shown in FIG. 1. 
     FIG. 3 is a partial cross-sectional view taken along line 4--4 of FIG. 1. 
     FIG. 4 is a partial cross-sectional view of another prior art condenser. 
     FIG. 5 is a perspective view of a condenser in accordance with one embodiment of this invention. 
     FIG. 6 is an exploded perspective view partially broken away of certain elements of the condenser as shown in FIG. 5. 
     FIG. 7 is a partial cross-sectional view of a condenser as shown in FIG. 5. 
     FIG. 8 is an exploded perspective view partially broken away of certain elements of the condenser in accordance with another embodiment of this invention. 
     FIG. 9 is a partially cut away perspective view taken along line A--A of FIG. 8. 
     FIG. 10 is a partial side view of a condenser including certain elements as shown in FIG. 8. 
     FIG. 11 is an exploded perspective view partially broken away of certain elements of the condenser in accordance with still another embodiment of this invention. 
     FIG. 12 is an exploded perspective view partially broken away of certain elements of the condenser in accordance with still another embodiment of this invention. 
     FIG. 13 is an exploded perspective view of certain elements of the condenser in accordance with still another embodiment of this invention. 
     FIG. 14 is a partial side view of a condenser including certain elements as shown in FIG. 13. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The construction of a heat exchanger, and in particular a condenser, in accordance with the first embodiment of the present invention is shown in FIGS. 5-7. 
     A plurality of corrugated fin units 3 are disposed between adjacent tubes 2. Flat tubes 2 and fin units 3 jointly form the heat exchange region. Header pipes 10 are disposed perpendicular to flat tubes 2 and may have, for example, a clad construction. Each part of the condenser in the other embodiments discussed herein is made of the same materials as described inregard to this embodiment. Header pipe 10 includes U-shaped wall 11 and front wall 12. U-shaped wall 11 is preferably formed by bending an aluminum plate into a U-shape and clading brazing materials on both surfaces thereof. As bent, the plate defines rear plate portion 11a and side plate portions 11b. Front wall 12 is preferably formed by bending thesame type of aluminum plate as U-shaped wall 11 to define a plurality of arc-shaped portions 12a. plate portions 12b disposed between adjacent arc-shaped portions 12a, and edge portions 12c at both ends thereof. Plateportions 12b are formed integrally with arc-shaped portions 12a and edge portions 12c. Further, each plate portion 12b is provided with elongated hole 13 to receive an open end of flat tube 2. The outer width of front wall 12 corresponds to the width between the inner surfaces of side plate portions 11b of U-shaped wall 11. The height of edge portions 12c of frontwall 12 corresponds to the depth of U-shaped wall 11. The height of arc-shaped portions 12a is lower than the depth of U-shaped wall 11 to thereby define a certain gap between the top surfaces of arc-shaped portions 12a and the inner surface of rear plate portion 11a. Partition wall 14 is disposed in the gap and connects arc-shaped portion 12a with the inner surface of rear plate portion 11a. The contact surfaces between front wall 12 and U-shaped wall 11 including partition walls 14 are preferably fixed by brazing. 
     In operation, compressed refrigerant gas from an external compressor coupled to inlet tube 5 flows into the interior of header pipe 10 through inlet tube 5. The refrigerant is distributed so that a portion of the gas adjacent rear plate portion 11a flows directly along the plane surface of rear plate portion 11a and another portion of the gas adjacent front wall 12 flows toward the open end of flat tube 2 along the curved surface of arc-shaped portion 12a, as shown by arrows in FIG. 7. The gas which flows out of the open end of flat tube 2 also flows toward the flat surface of rear plate portion 11a along the curved surface of arc-shaped portion 12a. 
     Since the refrigerant gas flows along the curved surfaces of arc-shaped portion 12a as described above (i.e., the direction of the flow of the refrigerant gas adjacent the open end of flat tube 2 is similar to that ofthe refrigerant gas in flat tube 2) the occurrence of vortexes adjacent theopen end of flat tube 2 is reduced. As a result, the pressure loss of the refrigerant in the heat exchanger is also decreased. 
     The construction of a part of a condenser in accordance with a second embodiment of the present invention is shown in FIGS. 8-10. Header pipe 16includes U-shaped wall 11 and front wall 12. U-shaped wall 11 has rear plate portion 11a, side plate portions 11b and projecting portion 17 extending in the longitudinal direction thereof at its inner end surface. Projecting portion 17 has cut portions 17a spaced out in the longitudinal direction of U-shaped wall 11. Partition walls 18 are respectively fitted into cut portions 17a. Front wall 12 has a plurality of arc-shaped portions 12a, plate portions 12b disposed between each arc-shaped portions12a, edge portions 12c at both ends thereof, and cut portions 12d formed atthe top ends of edge portions 12c. U-shaped wall 11 also has a plurality ofstep-like portions 19 spaced out along both side plate portions 11b in the longitudinal direction thereof at the positions corresponding to arc-shaped portions 12a of front wall 12. Step-like portions 19 are preferably formed by an embossing process so that inner peripheral surfaces 19a of step-like portions 19 contact the outer peripheral surfaces of arc-shaped portions 12a along both of its sides, respectively,and project inwardly of U-shaped wall 11 as shown in FIG. 9. 
     In the preferred assembly of header pipes 16, the top ends of both side plate portions 11b are first enlarged. Front wall 12 is then inserted intothe interior of U-shaped wall 11 until the top end surfaces of arc-shaped portions 12a contact the outer end surface of projecting portion 17 and projecting portion 17 is fit into cut portions 12d of front wall 12. Thereafter, the heat exchanger including header pipes 16 is made by brazing the parts together. 
     In the above construction, several parts are brazed together. Specifically,the end surface of projecting portion 17 is brazed to the top end surfaces of arc-shaped portions 12a. Further, the outer peripheral surfaces of arc-shaped portions 12a are brazed to inner peripheral surfaces 19a of step-like portions 19. This construction enhances the strength of header pipe 16 and improves its capacity to receive a high pressure gas therein. 
     The construction of a part of a condenser in accordance with a third embodiment of the present invention is shown in FIG. 11. Header pipe 30 includes U-shaped wall 11 and front wall 12. U-shaped wall 11 includes allthe elements of the second embodiment as well as ribs 20 extending inwardlyand in the longitudinal direction of U-shaped wall 11 from the ends of sideplate portions 11b. The gap between the end surface of projecting portion 17 and the inner surface of rib 20 is the same as the height of arc-shapedportions 12a to enable the insertion of arc-shaped portions 12a. Front wall12 has the same portions as described in the second embodiment. In addition, one of both edge portions 12c is formed separately from front wall 12. After front wall 12 is fitted into U-shaped wall 11, the edge portion 12c is fixed to the end of front wall 12. 
     In the preferred assembly of header pipes 30, front wall 12 is fitted between the inner surfaces of rids 20 and the end surface of projecting portion 17 through one end thereof which has no edge portion 12c. Edge portion 12c is then fixed to the end of front wall 12. Thereafter, the heat exchanger including header pipes 16, is made by brazing the parts together. 
     In the above construction, front wall 12 is easily positioned between ribs 20 and projecting portion 17. As a result, the assembly is easily accomplished. The strength of header pipe 30 is also reinforced. 
     The construction of a part of a condenser in accordance with a fourth embodiment of the present invention is shown in FIG. 12. Header pipe 31 includes U-shaped wall 11 and front wall 12. U-shaped wall 11 includes allthe elements of the third embodiment as well as reinforcing ribs 21, excluding step-like portions 19. Ribs 21 extend outwardly and in the longitudinal direction of U-shaped wall 11 from the sides of side plate portions 11b. In the above construction, U-shaped wall 11 has reinforcing ribs 21 extending outwardly and in the longitudinal direction of U-shaped wall 11 from both side surfaces of side plate portions 11b. This construction further improves the strength of header pipe 31. 
     The construction of a part of a condenser in accordance with a fifth embodiment of the present invention is shown in FIGS. 13 and 14. Header pipe 32 includes U-shaped wall 11 and a plurality of front walls segments 12. U-shaped wall 11 has rear plate portion 11a and side plate portions 11b which are integrally formed by bending an aluminum plate into a U-shape with an arcuate configuration. Each front wall segment 33 has a plurality of convex portions 331 projecting toward rear plate portion 11a and concave portions 332 disposed between convex portions 331. Elongated holes 333 are formed on the peaks of the concave portions 332, to enable the insertion of the open ends of flat tubes 2 therein. Front wall segments 33 are formed so that both of the side surfaces of front walls 33can sealingly contact the inner side surfaces of the side plate portions 11b. A plurality of partition walls 34 are disposed between front wall segments 33 to define the flow of the refrigerant. End plates 35 include step-like portions 35a extending toward the interior of header pipe 32 andengaging the inner surface of rear plate portion 11a and convex portions 331. The end plates are fitted into the top and bottom ends of header pipe32 to sealingly close the interior thereof. 
     In the above construction, front wall 33 and U-shaped wall 11 are connectedat both side surfaces. The construction enhances the strength of header pipe 31 to increase the capacity for higher inner pressures and decrease the risk of deformation. 
     The present invention has been described in accordance with preferred embodiments. These embodiments, however, are merely for example only, and the invention should not be construed as limited thereto. It should be apparent to those skilled in the art that other variations or modifications can be made within the scope of this invention.