Flat tubes for use with heat exchanger and manufacturing method thereof

Information

  • Patent Grant
  • 6267177
  • Patent Number
    6,267,177
  • Date Filed
    Wednesday, January 19, 2000
    24 years ago
  • Date Issued
    Tuesday, July 31, 2001
    23 years ago
Abstract
The height of a bead opposing a joint where side edges of a plate are to be joined is set to be smaller than the height of a bead which does not oppose the joint by the thickness of the plate. Further, lands are provided between the beads and protrude from either the tube surface or the tube surface toward the inside of the main tube unit, and flow gaps are formed through which the heat-exchange medium flows over the lands.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a flat heat-exchange tube for use with a condenser, an evaporator, a heater core, and a radiator each of which is employed in an automotive air-conditioner for effecting a refrigerating operation, as well an to a method of manufacturing the flat heat-exchange tube. More specifically, the present invention relates to a heat-exchange tube in which a plurality of protuberances are formed so as to protrude inwardly.




The present application is based on Japanese Patent Applications No. Hei. 11-11113 and 11-22771, which are incorporated herein by reference.




2. Description of the Related Art




As shown in

FIGS. 15 and 16

, a known flat heat-exchange tube is formed from a plate


1


in which a plurality of beads


1


A are formed so as to protrude to one side of the plate and a plate


2


in which a plurality of beads


2


A are formed so as to protrude to one side of the plate. Specifically, the flat heat-exchange rube is formed by assembling the plates


1


and


2


such that the tops of the beads


1


A and the tops of the beads


2


A are connected together by means of brazing.




Another type of known flat heat-exchange tube is shown in FIG.


17


. As shown in the drawing, the heat-exchange tube is formed by folding a single plate


4


into a flat tube, bonding opposite ends


4


A,


4


A of the plate


4


, and inserting an inner fin


5


into the internal space of the flat tube.





FIG. 18

shows a still another type of a known flat heat-exchange tube. A flat heat-exchange tube A is described in Japanese Patent Publication No. Hei. 7-19774. The flat heat-exchange tube A comprises a flat main tube unit B through which a heat-exchange medium flows, and a plurality of cylindrical beads D which connect tube surfaces C, C, both mutually opposing within the main tube unit B, and cause turbulence in the flow of the heat-exchange medium. Reinforcement protuberances E are formed between a U-shaped bend portion B


1


or the heat-exchange tube A and the main tube unit B, to thereby connect the tube surfaces C, C to the bend B


1


in the longitudinal direction of the main tube unit B and to reinforce the bend B


1


.




In the flat tube A, a heat-exchange medium flowing through the main tube unit B is circulated while the plurality of beads D cause turbulence in the laminar flow of the heat-exchange medium, thereby improving a heat exchange efficiency.




Aforementioned known flat heat-exchange tubes have encountered the following problems.




In the flat heat-exchange tube shown in

FIG. 15

, when the plates


1


and


2


are brought into contact with each other, joints


3


which protrude from either side of the plates


1


and


2


in the widthwise direction thereof become deformed, as shown in

FIG. 16

, thus causing a brazing failure. Further, since the joints


3


protrude from the plates


1


and


2


in the widthwise direction thereof, the widthwise length of the heat-exchange tube becomes longer. The diameter of an unillustrated header pipe to which the flat heat-exchange tube is to be mounted becomes larger correspondingly.




In the flat heat-exchange tube shown in

FIG. 17

, the pressure applied to the joints of the plate


4


is made insufficient when the inner fin


5


is inserted into the internal space and becomes displaced, thus becoming more likely to cause a brazing failure.




In the flat heat-exchange tube A shown in

FIG. 18

, the plurality of beads D cause substantially two-dimensional turbulence in the laminar flow or the heat-exchange medium, and hence the thus-generated turbulence has a little affect of causing turbulence in a thermal boundary layer of hear-exchange medium developing in the vicinity of the tube surfaces C, C, thus limiting an improvement in heat exchange efficiency.




SUMMARY OF THE INVENTION




The present invention is aimed at providing a flat heat-exchange tube which can firmly fix joints and has a narrow width.




The present invention is also aimed at providing a flat heat-exchange tube which can improve heat exchange efficiency than does a known flat heat-exchange tube.




According to a first aspect of the present invention, there is provided a flat heat-exchange tube comprising: a plate of which opposite side edges are folded into a flat tube shape and joined together so as to constitute a flow space for a heat-exchange medium; and a plurality of beads being formed so as to protrude inwardly from one of or both of mutually-opposed flat surface portions of the plate, tops of the beads being joined to corresponding areas on the flat surface portion, wherein a first side edge of the opposite side edges is located on an inner side of a second side edge of the opposite Side edges, and joined to the top of the bead located opposite the first side edge.




A height of the bead opposing the first side edge may be set to be lower than a height of the bead located so as not to oppose the first side edge.




Preferably, the height of the bead opposing the first side edge is set to be lower than the height of the bead located so as not to oppose the first side edge by a thickness of the plate.




The beads can be formed in a plurality of rows in a longitudinal direction of the flat surface portion. An area where the opposite side edges are joined together may be located opposite over a plurality of rows of the beads.




According to a first aspect of the present invention, there is provided a method of manufacturing a flat heat-exchange tube comprising steps of: forming a plurality of beads in one surface portion of a plate so as to protrude from the surface portion; folding the plate into a flat tube shape such that the beads protrude to an inside of the flat tube; bringing side edges of the plate into contact with each other; bringing a joint where the side edges are contacted into contact with a top of the beads; and fixing the joint and a contacted portion of the beads.




The joint may be formed so as to be located within one of the two mutually-opposed flat surface portions of the plate.




The above manufacturing method preferably further comprises a step of forming a stepped portion having a height corresponding to a thickness of the plate on one side edge for fittingly receiving the other side edge at the step of bringing side edges, to thereby make an exterior peripheral surface of the plate including the joint plane, wherein a height of the bead opposing the joint is set to be lower than a height of the bead located so as not to oppose the joint by an amount smaller than the thickness of the plate prior to the fixing step.




According to a third aspect of the present invention, there is provided a flat heat-exchange tube comprising: a flat main tube body through which a heat-exchange medium flows; a plurality of beads for connecting tube surfaces both mutually opposing within the main tube body, to thereby cause turbulence in a flow of the heat-exchange medium within the main tube body; lands being provided between the beads and protruding from al least one tube surface toward an inside of the main tube body; and flow gaps through which the heat-exchange medium flows over the lands.




Preferably, the lands cross-link the beads.




Preferably, beads are intermittently arranged in the main tube body with a plurality of rows in a longitudinal direction of the main tube unit, and the beads of a certain row and the beads of another adjacent row are arranged in a staggered configuration, and the lands are formed between all the beads of the adjacent rows such that a bead of the certain row is linked to the beads of the adjacent rows located in upstream positions with respect to a flow of the heat-exchange medium as well as to the beads of the adjacent rows located in downstream positions with respect to the flow of the heat-exchange medium.




On the other hand, the lands can formed between all the beads of adjacent rows such that a bead of a certain row is linked to one of the beads of the adjacent rows located in upstream positions with respect to a flow of the heat-exchange medium as well as to one of the beads of the adjacent rows located in downstream positions with respect to the flow of the heat-exchange medium, to thereby linearly link the beads.




The beads can be arranged at uniform intervals in the longitudinal direction of the main tube body, and the beads of a certain row and the beads of another adjacent row can be arranged in a staggered configuration.




The lands may be formed so as to have a circular-arc cross section.




In the present invention, the height of a bead located opposite one side edge of a plate is set to be lower than the height of another bead located so as not to oppose the side edge. Therefore, a joint where both side edges of the plate meet and are joined can be prevented from raising outwardly from the exterior side surface of the plate. Further, the joint of the plate is formed in a flat surface portion of the plate opposing the beads, thereby preventing an undesired increase in the width of a flat heat-exchange tube.




The joint where the side edges of the plate meet and are joined can be made in flush with the exterior side surface of the plate, thus preventing the joint from raising from the exterior side surface of the flat heat-exchange tube. Further, beads located so as not to oppose the joint can be joined to corresponding areas on the flat surface portion of the plate unfailingly.




The joint where the side edges of the plate meet and are joined can be connected to the tops of the row of beads formed in the flat surface portion(s) in the longitudinal direction thereof, thus forming a firmly-connected joint over the plate in the longitudinal direction thereof and ensuring a joint strength.




The joint where the side edges of the plate meet and are joined are joined to a plurality of rows of beads, thus increasing the bonding strength of the joints to a much greater extent.




The joint where the side edges of the plate meet and are joined and the joint and the tops of the beads can be brought into contact with each other and fixed together by a single operation. The joint and the tops of the beads can be brought into contact with each other by pressing the joint formed between the side edges of the plate, thus facilitating manufacture of a flat heat-exchange tube.




The joint where the side edges of the plate meet and are joined is placed within the flat surface portion of the plate, thus preventing an increase in the width of the flat heat-exchange tube. Accordingly, there can be prevented an increase in the diameter of a pipe to which the flat heat-exchange pipe is to be mounted.




A step having a height corresponding to the thickness of the plate is formed in one of the side edges of the joint, thus preventing the joint from raising outwardly, which would otherwise be caused when the side edges are joined. The height of beads located opposite the joint is set beforehand to be lower than the height of beads located so as not to oppose the joint, by only the height of the plate. Accordingly, when the plate is folded, the joint where the side edges of the plate meet can be situated on and brought into pressing contact with the tops of the beads, thus forming contacts unfailingly. Further, the tops of the beads located so as not oppose the joint can also be brought into contact with the interior surface of the plate by means of the pressing force, thus achieving formation of contacts and firm brazing unfailingly.




Further, in the present invention, a heat-exchange medium flows over lands while the laminar flow of the heat-exchange medium is made turbulent by a plurality of beads. The heat-exchange medium flowing over the lands flows down from their tops toward a tube surface, thus causing turbulence in a thermal boundary layer of heat-exchange medium developing in the vicinity of the tube surface. The heat-exchange tube of the present invention can make the thermal boundary layer of the heat-exchange medium thinner than does the known flat heat-exchange tube having only a plurality of beads, thus enabling a further improvement in the heat exchange efficiency.




In the present invention, since the beads are cross-linked by the lands, the heat-exchange medium flowing between the beads can fall down from the tops of the lands toward the tube surface unfailingly. Accordingly, the thermal boundary layer of the heat-exchange medium developing in the vicinity of the tube surface can be made turbulent unfailingly.




In the present invention, all the beads are linked by the lands so as to intersect diagonally with respect to the longitudinal direction of a main tube unit. A plurality of substantially-rectangular regions, each having four sides which are diagonal with respect to the longitudinal direction or the main tube unit, are formed in either one or the tube surfaces In each of the rectangular regions, the thermally boundary layer can be made turbulent. Accordingly, the heat-exchange tube of the present invention can improve a heat exchange efficiency to a greater extent.




In the present invention, all the beads are linked by the lands so as to intersect diagonally with respect to the longitudinal direction of the main tube unit. Consequently, in at least one of the tube surfaces there can be formed alternately land regions—in which the beads are linked by the lands so as to extend diagonally with respect to the longitudinal direction of the main tube unit—and flow regions which extend along the land regions and do not have any lands.




The heat-exchange medium that has flowed over the lands provided in the land regions can cause turbulence in the thermal boundary layer of the heat-exchange medium. Further, the flow regions enable smooth flow of the heat-exchange medium, thus achieving both an improvement in heat exchange efficiency and a reduction in flow resistance.




In the present invention, the beads are arranged at uniform intervals in the longitudinal direction of the main tube unit. The beads of the adjacent rows a rear ranged in a staggered configuration, thus increasing the distribution density of the beads. Consequently, there can be achieved a further increase in heat exchange efficiency and an improvement in compressive strength of the main tube unit.




In the present invention, the land formed has a circular-arc cross section, thus enabling a decrease in the flow resistance which the heat-exchange medium encounters when flowing over the top of the land. Accordingly, the heat-exchange tube or the present invention can diminish flow resistance.











Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.




BRIEF DESCRIPTION OF THE DRAWINGS




In the accompanying drawings:





FIG. 1

is a perspective view showing the principal section of a flat heat-exchange tube according to a first embodiment of the invention;





FIG. 2

is a cross-sectional view showing the principal section of the flat heat-exchange tube of the first embodiment;





FIG. 3

is a perspective view of the principal section of a plate constituting the flat heat-exchange tube of the first embodiment;





FIG. 4

is an exploded perspective and descriptive view showing the flat heat-exchange tube of the first embodiment;





FIG. 5

is a cross-sectional descriptive view showing the principal section of the flat heat-exchange tube of the first embodiment;





FIG. 6

is a cross-sectional descriptive view showing the principal section of the flat heat-exchange tube of the first embodiment;





FIG. 7

is a cross-sectional descriptive view showing the principal section of a flat heat-exchange tube according to a second embodiment of the present invention;





FIG. 8

is a plan view showing a heat-exchange tube according to a third embodiment of the present invention;





FIG. 9

is a cross-sectional view of the heat-exchange tube taken along line V—V shown in FIG


8


;





FIG. 10

is a perspective view showing the principal section of the heat-exchange tube shown in

FIG. 8

;





FIG. 11

is a plan view showing a heat-exchange tube according to a fourth embodiment of the present invention;





FIG. 12

is a perspective view showing the principal section of the heat-exchange tube shown in

FIG. 11

;





FIG. 13

is a plan view showing a heat-exchange tube according to a fifth embodiment of the present invention;





FIG. 14

is a perspective view showing a heat-exchange tube according to a sixth embodiment of the present invention;





FIG. 15

is a descriptive view showing a process for manufacturing a known flat heat-exchange tube;





FIG. 16

is a cross-sectional view of the principal section of a known flat heat-exchange tube for describing a problem thereof;





FIG. 17

is an exploded perspective view showing another example of a known flat heat-exchange tube; and





FIG. 18

is a perspective view showing a still another example of a known heat-exchange tube.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




A flat heat-exchange tube according to the present invention will be described in detail hereinbelow by reference to embodiments illustrated in the accompanying drawings.





FIGS. 1 through 6

show a flat heat-exchange tube according to a first embodiment of the present invention

FIG. 1

is a perspective view showing the principal section of a flat heat-exchange tube


11


of a condenser which is employed as an automotive heat exchanger for effecting a refrigerating operation.




As shown in

FIG. 1

, side edges


12


A and


12


B of a single rectangular plate


12


are folded so as to overlap at the center of the plate


12


, thus forming the flat heat-exchange tube


11


. Channels for a heat-exchange medium serving as a coolant are formed within the flat heat-exchange tube


11


. A plate joint where the side edges


12


A and


12


B overlap is jointed to the top surface of a bead


13


protruding from a portion of the plate


12


opposing the plate joint (i.e., the underside portion of the plate


12


). The plate joint between the side edges


12


A and


12


B, the side edge


12


B located inside of the plate joint, and the top surface of the bead


13


are connected by means of brazing.




The beads


13


are intermittently and protruding formed in rows in the surface of the plate


12


along the longitudinal direction (i.e., the direction in parallel with the side edges


12


A and


12


A) of the flat heat-exchange tube


11


. The plate joint is set to be located on each of the rows of beads


13


. Beads


14


are intermittently formed in rows in the area of the underside portion of the plate


12


, which area does not face the plate joint in the longitudinal direction thereof. The row of bead


14


is higher than the row of bead


13


. In the present embodiments two rows of beads


14


are intermittently formed in the plate


12


in the longitudinal direction thereof The beads


13


and


14


are formed by means of dimpling, and the beads


14


are fixed to the portions of the plate


12


opposing the beads


14


by means of brazing.




As shown in

FIG. 2

, The height H


1


of the bead


13


formed in the flat heat-exchange tube


11


of the present embodiment is larger than the height H


2


of the bead


14


by the thickness “t” of the plate


12


. A step is formed in the side edge


12


B which will constitute a plate joint, to a height corresponding to the thickness “t” of the plate


12


. The side edge


12


A is fitted into the step, thus rendering the exterior surface of the plate joint plane. Each of the beads


13


and


14


is circular when viewed from the above and is trapezoidal when viewed in cross section. The beads


13


and


14


complicate and elongate the coolant flow channel and contribute to an increase in the surface area and rigidity of the flat heat-exchange tube


11


. Although not shown in the drawings, an inlet port for permitting inflow of a coolant is formed in one longitudinal end of the flat heat-exchange tube


11


, and an outlet port for permitting outflow of a coolant is formed in the other longitudinal end of the same.




A method of manufacturing the flat heat-exchange tube


11


of the present embodiment will now be described by reference to

FIGS. 3 through 6

. In the present embodiment, the plate


12


, which has already been machined as shown in

FIG. 3

, is folded and subjected to brazing. As shown in the drawing, in the present embodiment, the beads


13


and


14


are formed in an intermediate area of the plate


12


which has a predetermined width and extends in the longitudinal direction of the plate


12


. The side edge on either side of the intermediate area of the plate


12


is folded. A step for fittingly receive the side edge


12


A when the side edges


12


A and


12


B are folded is formed along the edge of the side edge


12


A The beads


13


are intermittently formed in a row along the longitudinal center of the plate


12


, and the beads


14


are formed in a predetermined layout on either side of the row of beads


13


. The number of rows of beads


13


and the number of rows of beads


14


may be changed, as required, according to the size of the flat heat-exchange tube


11


.




The side edges


12


A and


12


B of the plate


12


are folded such that the side edge


12


A is laid on the side edge


12


B, as shown in FIG.


4


.

FIG. 4

is an exploded perspective and descriptive view showing the flat heat-exchange tube


11


when the tube


11


is cut and exploded so as to make the underside portion of the plate


12


visible. In

FIG. 4

, the shaded area denotes the area where a plate joint is to be formed; that is, a position an the beads


13


.




Next will be described the height of the beads


13


and the height of the beads


14


, which are formed in the plate


12


beforehand. As shown in

FIG. 5

, the height H


2


′ of the bead


13


is set beforehand so as to be lower than the height of H


1


of the bead


14


by an amount smaller than the thickness “t” of the plate


12


. Thus, the height H


2


′ of the bead


13


is set slightly higher than a height which is obtained by subtracting the thickness “t” from the height of H


1


of the bead


14


(H


2


′+t>H


1


).

FIG. 5

shows the plate joint (where the side edges


12


A and


12


B overlap) is in contact with the top surface of the bead


13


. At this time, the top surface of the bead


14


is spaced apart from a corresponding portion of the interior surface of the plate


12


.




The plate joint is forcefully pressed against the top surface of the bead


13


by means of predetermined force, thereby bringing the side edge


12


A into contact with the side edge


12


B and bringing the side edge


12


B into contact with the top surface of the bead


13


unfailingly At this time, the height of the bead


13


is reduced to H


2


by means of pressing force. As shown in

FIG. 6

, the interior surface of the plate


12


is also brought into contact with the top surfaces of the beads


14


by means of the pressing force while the side edges


12


A and


12


B, the side edge


12


B and the beads


13


, the beads


14


and the interior surface of the plate


12


are remaining in contact with each other respectively, these portions are fixed by means of brazing, thereby forming the flat heat-exchange tube


11


of the present embodiment.




In the present embodiment, formation of firm joints and reliable brazing can be achieved by setting the height of the beads


13


and the height of the beads


14


in the manner as mentioned previously. The beads


13


and


14


, which have been formed in a layout such as that mentioned above, cause turbulence in the flow of a coolant circulating between the beads


13


and


14


, thus improving heat exchange efficiency.




The plate joint may be formed so as to extend across two rows of beads


13


according to a second embodiment as shown in

FIG. 7

In this case, the pressing force to be applied for bringing the side edges into contact with each other can be made to a greater extent In the above embodiments, the beads are formed to protrude from one flat portion of the plate (i.e, the underside portion of the plate)- Needless to say, beads may be formed so as to protrude from both flat portions of the plate (i.e., both the upper portion and the lower portion of the plate).





FIG. 8

is a plan view showing a third embodiment according to the present invention.

FIG. 9

is a cross-sectional view taken along line V—V shown in FIG.


8


. As shown in

FIGS. 8 and 9

, the heat exchange flat tube


1


comprises a flat main tube unit


22


through which a heat-exchange medium flows, and a plurality of beads


25


which connect tube surfaces


23


,


24


, both mutually opposing within the main tube unit


22


, and cause turbulence in the flow of a heat-exchange medium within the main tube unit


22


.




The bead


25


has an oval and cylindrical shape, whose major axis extends in the longitudinal direction X of the main tube unit


22


. A land


26


and a flow gap


27


are formed between the adjacent beads


25


. The land


26


protrudes from the tube surface


23


and extends to the inside of the main tube unit


22


together with the bead


25


, thereby cross-linking the beads


25


. The heat-exchange medium flows over the lands


26


through the flow gaps


27


.




An unillustrated inlet port which permits inflow of a heat-exchange medium into the main tube unit


22


is formed in one end of the main tube unit


22


in its longitudinal direction X. Further, an outlet port which permits outflow of the heat-exchange medium to the outside of the main tube unit


22


is formed in the other end of the main tube unit


22


in its longitudinal direction X.




The flat tube


21


is formed by folding the opposite sides of a single rectangular plate P, which are located in the widthwise direction thereof, and brazing the edges of the thus-folded sides of the plate P at the center thereof.




A plurality of protuberances T which will be formed into the beads


25


are formed, beforehand and by means of dimpling, at predetermined positions in the surface of the plate P where the tube surfaces


23


and


24


will be formed after processing. The top surfaces of the protuberances T is brazed to the tube surface


24


when the plate P is folded, thus constituting the beads


25


. Further, a plurality of lands


26


are formed, beforehand and by means of dimpling, between the adjacent beads


25


in the surface of the plate P where the tube surfaces


23


and


24


will be formed after processing.




As shown in

FIG. 8

, in the flat tube


21


there are formed a plurality of equally-spaced rows of beads


25


in the longitudinal direction X of the main tube unit


22


. The beads


25


of the adjacent rows are arranged in a staggered configuration.




All the beads


25


are linked by the respective lands


26


such that a bead


25


of the certain row is linked to the beads


25


of adjacent rows located in upstream positions with respect to the direction of flow of the heat-exchange medium as well as to the beads


25


of the adjacent rows located in downstream positions with respect to the direction of flow of the heat-exchange medium.




In the flat tube


21


, the beads


25


are linked by the lands


26


so as to diagonally intersect with respect to the longitudinal direction X of the main tube unit


22


. In

FIG. 8

, reference symbol H designates the distance between the tube surfaces


23


and


24


, and reference symbol “h” designates the height of the land


26


protruding from the tube surface


23


.




FIG


10


Is a perspective view showing the principal section of the flat heat-exchange tube shown in FIG.


8


. As shown in

FIG. 10

, in the flat tube


21


, the heat-exchange medium flows over the lands


26


while the laminar flow of the heat-exchange medium is made turbulent by the plurality of beads


25


.




The heat-exchange medium flowing over the lands


26


flows down from their tops toward the tube surface


23


, thus causing turbulence in the thermal boundary layer of the heat-exchange medium developing in the vicinity of the tube surface


23


. Therefore, the heat-exchange tube of the present invention can make the thermal boundary layer of the heat-exchange medium thinner than does the known flat heat-exchange tube which has only the plurality of beads D and is shown in

FIG. 18

, thus enabling a further improvement in the heat exchange efficiency.




Since in the flat tube


1


all the beads


25


are cross-linked by the lands


26


, the heat-exchange medium flowing between the beads


25


can fall down from the tops of the lands


26


toward the tube surface


23


unfailingly. Accordingly, the thermal boundary layer of the heat-exchange medium developing in the vicinity of the tube surface


23


can be made turbulent unfailingly.




In the flat tube


21


, the beads


25


are linked so as to intersect diagonally by the lands


26


with respect to the longitudinal direction X of the main tube unit


22


A plurality of substantially-rhomboid regions R, each having four sides which are diagonal with respect to the longitudinal direction X of the main tube unit


22


, are formed in the tube surface


23


. In each of the rhomboid regions R, the thermally boundary layer can be made turbulent. Accordingly, the heat-exchange tube of the present invention can unfailingly improve a heat exchange efficiency than does the known heat-exchange tube shown in FIG.


18


.




In the flat tube


21


, the beads


25


are arranged at uniform intervals in the longitudinal direction X of the main tube unit


22


. The beads


25


of the adjacent rows are arranged in a staggered configuration, thus increasing the distribution density of the beads


25


, enabling an increase heat exchange efficiency and an improvement in the compressive strength of the main tube unit


22


.




As shown in

FIG. 10

, the land


26


formed in the flat tube


21


has a circular-arc cross section, thus enabling a decrease in the flow resistance which the heat-exchange medium encounters when flowing over the top of the land


26


. Further, the bead


25


has an oval and cylindrical shape whose major axis extends in the longitudinal direction X of the main tube unit


22


, thereby diminishing the flow resistance which the heat-exchange medium encounters when flowing along the outer circumferential surface of the bead


25


. Accordingly, the heat-exchange tube of the present invention can diminish flow resistance.




The height “h” of the land


26


shown in

FIG. 9

preferably assumes a value of 10 to 60% of the distance H between the tube surfaces


23


and


24


. If the height “h” of the land


26


is under 10% of the distance H between the tube surfaces


23


and


24


, the effect of causing turbulence in the thermal boundary layer of the heat-exchange medium, which would be caused when the heat-exchange medium flows from the top of the land


6


down toward the tube surface


23


, becomes substantially lost. In contrast, if the height “h” of the land


26


exceeds 60% of the distance H between the tube surfaces


23


and


24


, the flow resistance becomes excessively great.





FIG. 11

is a plan view showing a fourth embodiment embodying the inventions described in the appended claims.

FIG. 12

is a perspective view showing the principal section of a heat-exchange tube shown in FIG.


11


. In the following description about the fourth embodiment, those constituent elements which are the same as those described in the third embodiment are assigned the same reference numerals, and repetition of their explanations is omitted.




As shown in

FIGS. 11 and 12

, in a flat tube


210


, the beads


25


are connected by the land


26


such that one bead


25


of a certain row is connected to a bead


25


of the right-side adjacent row located in an upstream position relative to the one bead


25


when viewed in the flowing direction of the heat-exchange medium.




Further, the beads


25


are connected by the land


26


such that one bead


25


of a certain row is connected to a bead


25


of the left-side adjacent row located in a downstream position relative to the one bead


25


when viewed in the flowing direction of the heat-exchange medium.




In the flat tube


210


, there can be formed alternately land regions L—in which the beads


25


are linked by the lands


26


so as to extend diagonally with respect to the longitudinal direction X of the main tube unit


22


—and flow regions M which extend along the land regions L and do not have any lands


26


. Consequently, the heat-exchange medium flows through the main tube unit


22


while flowing over the lands


26


in the land regions L as well as through the flow regions M not having the lands


26


.




The heat-exchange medium that has flowed over the lands


26


can cause turbulence in the thermal boundary layer of the heat-exchange medium developing in the vicinity of the tube surface


23


. Further, the heat-exchange medium can smoothly flow through the flow regions M, because the flow regions M do not have any lands


26


, which would otherwise hinder smooth flow of the heat-exchange medium. Thus, the flat tube


210


of the present embodiment can achieve both an improvement in the heat exchange efficiency and a reduction in the flow resistance.





FIG. 13

is a plan view showing a fifth embodiment. As shown in

FIG. 13

, reinforcement protuberances


221


are formed along the opposite edges of a flat tube


220


, which are located in the widthwise direction thereof, so as to protrude from the tube surface


23


and to be attached to the tube surface


24


. The reinforcement protuberances


221


extend in the longitudinal direction X of the main tube unit


22


.




In the flat tube


220


, the reinforcement protuberances


221


can reinforce U-shaped bends


222


formed along the opposite edges of the main tube unit


22


, the opposite edges being provided in the widthwise direction of the main tube unit


22


The reinforcement protuberances


221


may be provided in, for example, the center of the main tube unit


22


or in the flat tube


21


of the third embodiment.




In the flat tubes


21


,


210


, and


220


, which have been described above, the bead


25


has an oval and cylindrical shape. The shape of the bead


25


is not limited to an oval and cylindrical shape. The bead


25


may assumes any one of the shapes comprising a circular and cylindrical shape, a prismatic shape, a two-step shape, a multi-step shape, and an elongated shape extending in the longitudinal direction X of the main tube unit


22


. Alternatively, the beads


25


of any shapes may be used in combination. Here, the bead


25


desirably assumes a cylindrical shape, because the cylindrical shape diminishes the resistance which the heat-exchange medium encounters during flow.




The lands


26


formed on the surface of the respective flat tubes


21


,


210


, and


220


assume a circular-arc cross section. However, the cross-section of the land


26


is not limited to a circular-arc shape. For example, the land


26


may assume a dihedral shape or a polyhedral shape. However, since a circular-arc cross section diminishes the flow resistance, the land


6


desirably assumes a circular-arc cross section.




In the flat tubes


21


,


210


, and


220


, the beads


25


and the lands


6


are formed so as to protrude from the tube surface


23


. However, the beads


25


and the lands


26


may be formed so as to protrude from both the tube surfaces


23


and


24


or from the tube surface


24


. Alternatively, the beads


5


may be, fixedly sandwiched between the tube surfaces


23


and


24


, and the lands


26


may be fixed on either the tube surface


23


or


24


.




In the flat tubes


21


,


210


, and


220


, the lands


26


cross-link the adjacent beads


25


. However, according to a sixth embodiment as shown in

FIG. 14

, the lands


26


may be formed between the adjacent beads


25


without cross-linking them. The beads


25


to be cross-linked by the lands


26


or the beads


25


having the lands


6


formed therebetween may not necessarily be adjacent to each other. In terms of an improvement in heat exchange efficiency, the beads


25


are desirably adjacent to each other.




Further, each of the flat tubes


21


,


210


, and


220


is formed by folding a single plate P. However, the flat tube may be formed by overlaying one plate on another plate, for example. It goes without saying that the flat tubes


21


,


210


, and


220


may be used for a tube of a known drawn-cup-type heat exchanger or a like heat exchanger. Hereupon, the drawn-cup-type heat exchanger means such a type of heat exchanger in which tanks are integrally formed with tubes.




Further, the present invention can be applied to a flat heat-exchange tube, such as an evaporator, a heater, or a radiator, as well as to a condenser employed in an automotive refrigeration system.




Although the present invention has been described by reference to the above embodiments, the present invention is not limited solely to the embodiments.



Claims
  • 1. A flat heat-exchange tube comprising:a plate of which opposite side edges are folded into a flat tube shape and joined together to form a lap joint so as to constitute a flow space for a heat-exchange medium; and a plurality of beads being formed so as to protrude inwardly from one of or both of mutually-opposed flat surface portions of said plate, tops of said beads being joined to corresponding areas on said flat surface portion, wherein a first side edge of said opposite side edges is located on an Inner side of a second side edge of said opposite side edges, and joined to the top of said bead located opposite said first side edge said lap joint being substantially coextensive with the top of the beads.
  • 2. A flat heat-exchange tube according to claim 1, wherein a height of said bead opposing said first side edge is set to be lower than a height of said bead located so as not to oppose said first side edge.
  • 3. A flat heat-exchange tube according to claim 2, wherein the height of said bead opposing said first side edge is set to be lower than the height of said bead located so as not to oppose said first side edge by a thickness of said plate.
  • 4. A flat heat-exchange tube according to claim 1, wherein said beads are formed in a plurality of rows in a longitudinal direction of said flat surface portion.
  • 5. A flat heat-exchange tube according to claim 4, wherein an area where said opposite side edges are joined together is joined to the tops of a plurality of rows of said beads.
  • 6. A flat heat-exchange tube according to claim 1, wherein said beads have a substantially cylindrical shaped surface.
  • 7. A flat heat-exchange tube according to claim 1, further comprising at least one reinforcement protuberance inwardly protruding from one of said mutually-opposed flat surfaces and in contact with said other mutually-opposed flat surface.
  • 8. A method of manufacturing a flat heat-exchange tube comprising steps of:forming a plurality of beads in one surface portion of a plate so as to protrude from the surface portion; folding the plate into a flat tube shape such that the beads protrude to an inside of the flat tube; bringing first and second side edges of the plate into contact with each other to from a lap joint; forming a joint wherein said first side edge contacts with an inner side of said second side edge and is joined with a top of the beads; said lap joint being substantially coextensive with the top of the beads and fixing the joint and a contacted portion of the beads.
  • 9. A manufacturing method according to claim 8, wherein the joint is formed so as to be located within one of the two mutually-opposed flat surface portions of the plate.
  • 10. A manufacturing method according to claim 8, further comprising a step of forming a stepped portion having a height corresponding to a thickness of the plate on one side edge for fittingly receiving the other side edge at the step of bringing side edges, to thereby make an exterior peripheral surface of the plate including the joint plane,wherein a height of the bead opposing the joint is set to be lower than a height of the bead located so as not to oppose the joint by an amount smaller than the thickness of the plate prior to the fixing step.
  • 11. A method of manufacturing a flat heat-exchange tube according to claim 8, wherein said beads have a substantially cylindrical shaped surface.
  • 12. A flat heat-exchange tube comprising:a flat main tube body through which a heat-exchange medium flows, said tube body having opposing inner tube surfaces; a plurality of beads protruding inwardly from at least one of said inner tube surfaces and abutting to said opposite inner tube surface, to thereby cause turbulence in a flow of the heat-exchange medium within said main tube body; and lands positioned between said beads and protruding inwardly from at least one of said inner tube surfaces and spaced from said opposite inner tube surface, to thereby form flow gaps through which the heat-exchange medium flows over said lands.
  • 13. A flat heat-exchange tube according to claim 9, wherein said lands cross-link the beads.
  • 14. A flat heat-exchange tube according to claim 12, wherein said beads are intermittently arranged in said main tube body with a plurality of rows in a longitudinal direction of said main tube unit, and said beads of a certain row and said beads of another adjacent row are arranged in a staggered configuration, andsaid lands are formed between all said beads of the adjacent rows such that a bead of the certain row is linked to said beads of the adjacent rows located in upstream positions with respect to a flow of the heat-exchange medium as well as to said beads of the adjacent rows located in downstream positions with respect to the flow of the heat-exchange medium.
  • 15. A flat heat-exchange tube according to claim 12, wherein said beads are intermittently arranged in said main tube body with a plurality of rows in a longitudinal direction of said main tube unit, and said beads of a certain row and said beads of another adjacent row are arranged in a staggered configuration, andsaid lands are formed between all said beads of adjacent rows such that a bead of a certain row is linked to one of said beads of the adjacent rows located in upstream positions with respect to a flow of the heat-exchange medium as well as to one of said beads of the adjacent rows located in downstream positions with respect to the flow of the heat-exchange medium, to thereby linearly link said beads.
  • 16. A flat heat-exchange tube according to claim 14, wherein said beads are arranged at uniform intervals in the longitudinal direction of said main tube body, and said beads of a certain row and said beads of another adjacent row are arranged in a staggered configuration.
  • 17. A flat heat-exchange tube according to claim 15, wherein said beads are arranged at uniform intervals in the longitudinal direction of said main tube body, and said beads of a certain row and said beads of another adjacent row are arranged in a staggered configuration.
  • 18. A flat heat-exchange tube according to claim 12, wherein said lands have a circular-arc cross section.
  • 19. A flat heat-exchange tube according to claim 12, wherein said beads have a substantially cylindrical shaped surface.
  • 20. A flat heat-exchange tube according to claim 9, further comprising at least one reinforcement protuberance inwardly protruding from one of said inner tube surfaces and in contact with said opposite inner tube surface.
  • 21. A flat heat-exchange tube according to claim 9, wherein a height h of said lands is between 10 and 60 percent of a distance H between said inner tube surfaces.
Priority Claims (2)
Number Date Country Kind
11-011113 Jan 1999 JP
11-022771 Jan 1999 JP
US Referenced Citations (8)
Number Name Date Kind
3783090 Andersson et al. Jan 1974
4024619 Jonason May 1977
4781248 Pfeiffer Nov 1988
5186250 Ouchi et al. Feb 1993
5398751 Blomgren Mar 1995
5697433 Kato Dec 1997
5765634 Martins Jun 1998
6016865 Blomgren Jan 2000
Foreign Referenced Citations (6)
Number Date Country
195 48 495 A1 Jun 1997 DE
0 854 342 A2 Jul 1998 EP
0 859 209 A1 Aug 1998 EP
2 261 819 Sep 1975 FR
2 757 615 Jun 1998 FR
303 120 Aug 1968 SE