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 as 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 1A are formed so as to protrude to one side of the plate and a plate 2 in which a plurality of beads 2A are formed so as to protrude to one side of the plate. Specifically, the flat heat-exchange tube is formed by assembling the plates 1 and 2 such that the tops of the beads 1A and the tops of the beads 2A 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 4A, 4A 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 B1 of the heat-exchange tube A and the main tube unit B, to thereby connect the tube surfaces C, C to the bend B1 in the longitudinal direction of the main tube unit B and to reinforce the bend B1.
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 of the heat-exchange medium, and hence the thus-generated turbulence has a little effect of causing turbulence in a thermal boundary layer of heat-exchange medium developing in the vicinity of the tube surfaces C, C, thus limiting an improvement in heat exchange efficiency.
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 prevent ed 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 surf ace 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 of the main tube unit, are formed in either one of 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 regionsxe2x80x94in which the beads are linked by the lands so as to extend diagonally with respect to the longitudinal direction of the main tube unitxe2x80x94and 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 are arranged 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 of 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.