Patent Publication Number: US-2009223656-A1

Title: Heat exchanger tube

Description:
TECHNICAL FIELD 
     The present invention relates to a heat exchanger tube which exchanges heat between air flowing in an outer circumference and coolant flowing in an internal passage. 
     BACKGROUND ART 
     As a conventional heat exchanger tube of this kind, there is the one disclosed in the Patent Document 1. This heat exchanger tube includes an external wall portion having a flat elliptical shape in cross section, and a partition wall for partitioning a passage within the external wall portion into two. The partition wall is set to a location such that an upstream side passage and a downstream side passage have the same width dimension, and is provided with two partition pieces which face one another. The heat exchanger tube having this kind of structure is fabricated from a single plate material, for example, in the following way. Both ends of a thin and long plate material in the width direction are folded to form the partition pieces, the plate material is then bended into a flat elliptical shape, and the partition pieces on both ends are faced to each other. Thereafter, the fabrication completes as the surfaces faced to each other by the bending are joined together by brazing or the like. 
     A heat exchanger is fabricated using the heat exchanger tube formed as above. The heat exchanger is installed such that an air flow passes the outer circumference along the width direction of the heat exchanger tube, and heat is exchanged between an air flow passing along the outer circumference and the coolant flowing inside along the upstream side passage and downstream side passage. Since the passage is divided into two by the partition wall, the heat exchanger tube is robust against a pressing force in the direction of crushing the passages and is highly pressure resistant. 
     Patent Document 1: Japanese Patent Laid-Open Publication No. Heisei 10-305341 
     DISCLOSURE OF THE INVENTION 
     Incidentally, the heat exchanger efficiency of the coolant flowing in the passages is different depending on upstream and downstream positions of an air flow passing along the outer circumference. However, in the conventional heat exchanger tube described above, the partition wall was set without consideration of heat exchanger efficiency of the coolant, and therefore, in terms of heat exchanger efficiency, the conventional heat exchanger tube was less than the best as a heat exchanger tube having a partition wall. 
     Therefore, an objective of the present invention is to provide a heat exchanger which includes a partition wall and is able to achieve an improvement of heat exchanger efficiency. 
     In order to achieve the above-mentioned objective, a heat exchanger tube according to the present invention is arranged in a direction across an air flow such that air flows in an external circumference along with a width direction of the heat exchange tube, and comprises an upstream side passage located on an upstream side of the air flow, a downstream side passage located on a downstream side of the air flow, and a partition wall for partitioning the upstream side passage and the downstream side passage, wherein the partition wall is arranged such that a width of the upstream side passage is larger than a width of the downstream side passage. 
     According to the above-mentioned structure, heat exchanger efficiency of a coolant flowing in the passages shows a pattern where the heat exchanger efficiency becomes highest in an uppermost stream location of the air flow, decreases gradually towards the downstream side, and remains low in downstream locations past the center location. In addition, the partition wall does not exist in a location where the heat exchanger efficiency is high so that a coolant flows in the entire tube and is used for heat exchange, and the partition wall is located at a position where the heat exchanger efficiency is approximately lowest. Hence, an improvement of the heat exchanger efficiency of the heat exchanger tube as a whole is achieved. 
     In the heat exchanger tube described above, the upstream side passage may be provided with a projecting portion which projects from at least one side of an external wall portion. 
     According to this structure, although the upstream side passage has a larger width and is thus less resistant to pressure than the downstream side passage, the projecting portion enhances pressure resistance of the upstream side passage. Therefore, pressure resistance of the heat exchanger tube as a whole is improved. Moreover, the projecting portion increases the inner circumference area of the upstream side passage and the surface area of the external wall portion thereof, and, at the same time, a coolant flow is disturbed by the projecting portion, which contributes to an improvement of heat exchange efficiency. 
     In the heat exchanger tube described above, the projecting portions may be provided in a plurality of locations with intervals therebetween along a longitudinal direction. 
     According to the above structure, a coolant flowing in the upstream side passage is agitated by the projecting portions in the plurality of locations, and heat exchange is enhanced. Hence, an improvement of heat exchange efficiency is achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a first embodiment of the present invention, illustrating how a heat exchanger tube is arranged within an air flow passage. 
         FIG. 2  is a perspective view of the first embodiment of the present invention, illustrating the entire heat exchanger tube. 
         FIG. 3  is a cross-sectional view of the first embodiment of the present invention, taken along the line  3 - 3  in  FIG. 2 . 
         FIG. 4  is a view showing the first embodiment of the present invention, illustrating characteristics of heat exchanger efficiency of the heat exchanger tube. 
         FIG. 5  is a schematic view of the first embodiment of the present invention, illustrating a manufacturing apparatus of the heat exchanger tube. 
         FIG. 6  is a perspective view of the first embodiment of the present invention, illustrating a main portion of the manufacturing apparatus. 
         FIGS. 7(   a ) to  7 ( f ) are perspective views of the first embodiment of the present invention, illustrating respective steps of forming the heat exchanger tube. 
         FIG. 8  is the perspective view of a second embodiment of the present invention, illustrating a main portion of a heat exchanger tube. 
         FIG. 9  is the perspective view of a third embodiment of the present invention, illustrating a main portion of the heat exchanger tube. 
         FIG. 10  is the perspective view of a fourth embodiment of the present invention, illustrating a main portion of the heat exchanger tube. 
         FIG. 11  is the perspective view of a fifth embodiment of the present invention, illustrating a main portion of the heat exchanger tube. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinbelow, details of a heat exchanger tube according to embodiments of the present invention will be described based on the drawings. 
     As shown in  FIG. 1 , a heat exchanger  1  is arranged in an air flow passage  3  of an air conditioning unit  2 . The heat exchanger  1  is provided with a plurality of heat exchanger tubes  10  arranged in parallel with one another with an interval therebetween, and a pair of headers  11  fixed to both ends of each of the plurality of the heat exchanger tubes  10 . The coolant flowed into the headers  11  is to be discharged from the headers  11  via the heat exchanger tube  10  along a predetermined path. Each of the heat exchanger tubes  10  is arranged along with the direction across the air flow such that the air flow within the air flow passage  3  passes the external circumference along the width direction of the heat exchange tube  10 . 
     As illustrated in  FIGS. 2 and 3 , the heat exchanger tube  10  includes an external wall portion  12  of which cross section has a flat elliptical shape, and a partition wall  14  which partitions a passage  13  within the external wall portion  12  into two. The passage  13  is partitioned by the partition wall  14  into an upstream side passage  13   a  located on the upstream side of the air flow, and a downstream side passage  13   b  located on the downstream side of the air flow. The partitioning position by the partition wall  14  is set to a location so that a width W 1  of the upstream side passage  13   a  is wider, and a width W 2  (&lt;W 1 ) of the downstream side passage  13   b  is narrower. Moreover, the partition wall  14  includes a pair of partition pieces  14   a  and  14   a  which are integrally connected to both ends of the external wall portion  12  in the width direction thereof, respectively, and brazing is performed between both partition pieces  14   a  and  14   a , and between the end surface of each of the partition pieces  14   a  and  14   a  and the inner surface of the external wall portion  12 . 
     A projecting portion  15  is provided in approximately the center of the upstream side passage  13   a  in the width direction thereof. The projecting portion  15  includes a pair of projecting pieces  15   a  provided at positions facing each other from both sides in the external wall  12 , the end surfaces of both projecting pieces  15   a  and  15   a  are brought into contact with each other, and the contact portion is brazed. The projecting portion  15  is continuously provided in an approximately entire area in the longitudinal direction of the heat exchanger tube  10 . 
     Next, manufacturing steps of the heat exchanger tube  10  are described. As shown in  FIG. 5 , a manufacturing apparatus  20  is provided with a first bending roller portion  12 , a coating roller portion  22 , a drying portion  23 , and a second bending roller portion  24 . The first bending roller  21  bends both end portions of, for example, a long aluminum material (see  FIG. 7(   a ))  25  wrapped into a roller shape, in order to form the partition pieces  14   a  and  14   a , and bend two locations in the center to form the projecting pieces (beads)  15   a  and  15   a  (see  FIGS. 7(   b ) and  7 ( c )). As shown in  FIG. 6 , the coating roller portion  22  includes a material accommodating portion  26  for accommodating a mixture of flux, a brazing filler metal, and binder, a first transfer roller  27 , a second transfer roller  28 , and a transfer sheet  29 . Thereafter, a mixed coating material  1  of flux, a brazing filler metal, and binder is applied to the end surfaces of the partition pieces  14   a  and  14   a  on both sides and two projecting portions  15   a  and  15   a  formed by the first bending roller portion  21  (see  FIGS. 6 and 7(   d )). The drying portion  23  volatizes the binder contained in the mixed coating material a which has been coated on the material  25 . The second bending roller portion  24  bends the material  25  bent into a predetermined shape into a shape of the heat exchanger tube  10  (see  FIGS. 7(   e ) and  7 ( f )). The heat exchanger tube  10  provisionally assembled as a constituent of the heat exchanger  1  is heat-treated in a heating furnace, thus brazing the portions where the mixed coating material a has been applied. 
     In the heat exchanger tube  10  having the above structure, heat is exchanged between an air flow passing along the air flow passage  3  and the coolant flowing along the internal passage  13 . As shown in  FIG. 4 , the heat exchanger efficiency shows a pattern where it is highest in the uppermost stream position of the air flow, gradually declines towards the downstream side, and remains low at a downstream location or after past the center location. In the above-described heat exchanger tube  10 , the partition wall  14  does not exist in the location where heat exchanger efficiency is high and the coolant flows in the entire tube for heat exchange, while the partition wall  14  is positioned in the location where the heat exchanger efficiency is reduced to approximately the lowest level. Therefore, an improvement of heat exchanger efficiency of the heat exchanger tube  10  as a whole is achieved. 
     In the first embodiment, since the projecting portion  15  is provided in the upstream side passage  13   a , the upstream side passage  13   a  having a larger width than that of the downstream side passage  13   b  has a structure which is highly pressure resistant. Hence, pressure resistance of the heat exchanger tube as a whole can be maintained. In addition, providing the projecting portion  15  increases the internal circumference area of the upstream side passage  13   a  and the surface area of the outer wall portion  12  of the upstream side passage  13   a , which thus contributes to an improvement of heat exchanger efficiency. 
       FIG. 8  shows a second embodiment of the present invention, and is a partial perspective view of a heat exchanger tube  30 . As shown in  FIG. 8 , in the heat exchanger tube  30  according to the second embodiment of the present invention, provided is projecting portions  31  in a plurality of locations separated from each other with an interval therebetween, instead of a projecting portion provided continuously in the longitudinal direction of the heat exchanger tube as described in the first embodiment. 
     According to the second embodiment, a coolant flowing in an upstream side passage  13   a  is agitated and disturbed by the projecting portions  31  in a plurality of locations, thus enhancing heat exchange. Accordingly, heat exchange efficiency is improved. 
       FIG. 9  shows a third embodiment of the present invention, and is a partial perspective view of a heat exchanger tube  32 . As shown in  FIG. 9 , the heat exchanger tube  32  according to the third embodiment is common to the heat exchanger tube of the second embodiment in terms of having a plurality of projecting portions  33  with an interval therebetween, but is different in that the projecting portions  33  of the heat exchanger tube  32  have an elliptic shape instead of the long and thin rectangular shape as described in the second embodiment. 
     In the third embodiment, a coolant flowing in an upstream side passage  13   a  is also agitated by the projecting portions  33  in the plurality of locations and heat exchange efficiency is enhanced. 
       FIG. 10  shows a fourth embodiment of the present invention, and is a partial perspective view of a heat exchanger tube  34 . As shown in  FIG. 10 , projecting portions  35  of the heat exchanger tube  34  according to the fourth embodiment are elliptic similarly to those of the third embodiment, but the projecting portions  35  are provided so that the orientations of the elliptic shape thereof are angled with regard to the longitudinal direction of the heat exchanger tube  34 . 
     In the fourth embodiment, a coolant flowing in an upstream side passage  13   a  is agitated by the projecting portions  35  in a plurality of locations and heat exchange is enhanced. Therefore, heat exchanger efficiency is improved. 
       FIG. 11  shows the fifth embodiment of the present invention, and is a partial perspective view of a heat exchanger tube  36 . As shown in  FIG. 11 , projecting portions  37  of the heat exchanger tube  36  according to the fifth embodiment of the present invention have an elliptic shape similarly to those of the third and fourth embodiments described above, but are different in that the elliptic shapes in different orientations are provided alternately, in which the long diameter of the elliptic shape is oriented in the same direction to the longitudinal direction of the heat exchanger tube  36 , or the long diameter of the same is oriented in an angled direction against the longitudinal direction of the heat exchanger tube  36 . 
     In the fifth embodiment, a coolant flowing in an upstream side passage  13   a  is agitated by the projecting portions  37  in the plurality of locations and heat exchange is enhanced. Hence, heat exchanger efficiency is improved. 
     In each of the above embodiments, although each of the projecting portions  15 ,  31 ,  33 ,  35  and  37  is formed of the pair of projecting pieces  15   a  (or those not shown) provided in the opposite locations in the external wall portion  12  which form the upstream side passage  13   a , it may be formed of only a projection piece projecting towards the inside from either one of the locations in the external wall portion  12 . In addition, in each of the embodiment, the projecting pieces  15   a  and  15   a  (or those not shown) on both sides are formed to have the same height which is approximately a half of the width of the upstream side passage  13   a , but the projecting pieces may be formed so that one of the projecting pieces may be higher than the half of the width and the other may be shorter than the half of the width. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, heat exchanger efficiency is highest in the uppermost stream location of an air flow, gradually decreases towards the downstream side, and remains low in downstream locations past a center location. In addition, a partition wall does not exist in a location where the heat exchanger efficiency is high so that a coolant flows in the entire tube and is used for heat exchange, and the partition wall is located at a position where the heat exchanger efficiency is approximately lowest. Hence, an improvement of the heat exchanger efficiency of the heat exchanger tube as a whole is achieved.