Solderable fluid channel for a heat exchanger of aluminum

Abstract

The invention relates to a fluid channel for a heat exchanger, comprising a metal sheet, wherein the metal sheet has at least one core region of an aluminum base alloy and at least one structure arranged inside the fluid channel, wherein the structure lies against a surface of the metal sheet and can be soldered to the metal sheet in a flux-free manner by way of a first soldering location in a soldering operation, and wherein a soldering region of the metal sheet and a counterpart lie against one another and can be soldered to one another in the same soldering operation as a second soldering location while wetting with flux, wherein an open path between the two soldering locations exists before the soldering operation.

Claims

1. A fluid channel for a heat exchanger, comprising: a metal sheet forming a tube having a first surface and a second surface, wherein the metal sheet is bent such that the first surface bounds the fluid channel and the second surface in part faces an environment, wherein the metal sheet comprises at least one core region comprising an aluminum base alloy, wherein the tube has a first flat side and a second flat side; at least one first structure formed by a 180 bend in the metal sheet projecting from the first flat side toward the second flat side and arranged inside the fluid channel dividing the fluid channel into multiple chambers, wherein a portion of the at least one first structure lies against a flat portion of the first surface of the metal sheet having no projection on the second flat side and is joined to the first surface of the metal sheet by a first solder joint that does not contain a flux material; a second structure formed by a joining of a first edgefold and a second edgefold, wherein the second structure comprises a soldering region of the second surface of the metal sheet on the first edgefold and a counterpart region of the second surface of the metal sheet on the second edgefold, wherein the soldering region and the counterpart region lie against one another and are joined by a second solder joint containing a flux material, wherein the counterpart region comprises an at least one unilateral solder plating having the following composition: 7-11% Si, 0-0.8% Fe, 0-1% Cu, 0.03-2.5% Mg, 0-4% Zn, 0-0.2% Ti, 0-0.5% Bi, and 0-0.2% Sr, wherein a remainder of the composition is Al; and a capillary gap formed between the soldering region and the counterpart region, wherein the capillary gap comprises a contact surface, wherein at one end the capillary gap is connected to a flushing channel and at another end the capillary gap is connected to the environment, wherein the flushing channel is approximately of triangular shape having two side walls formed the second surface of the metal sheet which converge toward the capillary gap and one side wall formed by the first surface of the metal sheet, wherein the flushing channel permits discharging the flux material from the second solder joint.

2. The fluid channel as claimed in claim 1, wherein a core region of the metal sheet has a magnesium content of at least approximately 0.03%.

3. The fluid channel as claimed in claim 1, wherein the magnesium content of the at least one unilateral solder plating is between 0.03% and 0.8%.

4. The fluid channel as claimed in claim 1, further comprising turbulators made of an aluminum alloy where each turbulator is inserted into a chamber of the fluid channel.

5. The fluid channel as claimed in claim 4, wherein the aluminum alloy of the turbulator contains no more than 0.7% magnesium or wherein the at least one unilateral solder plating has a magnesium content between 0.03% and 0.8%, wherein the metal sheet contains magnesium for soldering to the turbulator without flux material.

6. The fluid channel as claimed in claim 4, wherein the aluminum alloy of the turbulator contains no more than 0.7% magnesium and/or contains an at least one unilateral solder plating having a magnesium content of between 0.03% and 0.8%.

7. The fluid channel as claimed in claim 1, wherein the fluid channel is in the form of a flat tube having a fold which runs in a longitudinal direction of the tube, wherein the fold is in the form of a soldering region of the metal sheet.

8. The fluid channel as claimed in claim 7, wherein the at least one first structure is in the form of at least one web which is shaped from the metal sheet and lies against the first surface of the metal sheet, forming and forms a multi-chamber flat tube.

9. The fluid channel as claimed in claim 7, wherein the soldering region of the metal sheet has a fold portion which is soldered areally with wetting by flux material and an adjoining edgefold bent through more than 90.

10. The fluid channel as claimed in claim 9, wherein the following equation applies for a length L of the adjoining edgefold and a thickness D of the metal sheet:
L>2*D; wherein, for the case of an edgefold bent through 180, the following equation further applies:
L<(B2.5*D), with a width B of the flat tube.

11. The fluid channel for a heat exchanger as claimed in claim 1, wherein the flushing channel is bounded by the counterpart region and the soldering region, wherein a width of the flushing channel is greater than that of the capillary gap and is sufficient to permit discharging of flux material.

12. The fluid channel for a heat exchanger according to claim 1, wherein the metal sheet has a core region having the following composition: 0-0.7% Fe, 0.3-1.2% Cu, 0-0.5% Cr, 0-0.3% Ti, 0-1.2% Si, 0-2.0% Mn, 0.1-1.0% Mg, 0-0.2% Zr, wherein a remainder of the composition is Al.

13. The fluid channel for a heat exchanger according to claim 12, wherein the metal sheet comprises three layers having the following structure: solder plating/core region/solder plating.

14. The fluid channel for a heat exchanger according to claim 12, wherein the metal sheet comprises five layers having the following structure: top layer/solder plating/core region/solder plating/top layer.

15. A fluid channel for a heat exchanger, comprising: a metal sheet having a first surface and a second surface, wherein the metal sheet is bent such that the first surface bounds the fluid channel and the second surface in part faces an environment, wherein the metal sheet comprises at least one core region comprising an aluminum base alloy; at least one structure formed by a 180 bend in the metal sheet and arranged inside the fluid channel dividing the fluid channel into multiple chambers, wherein a portion of the at least one structure lies against a flat portion of the first surface of the metal sheet and is joined to the first surface of the metal sheet by a first solder joint that does not contain a flux material, wherein a soldering region of the second surface of the metal sheet and a counterpart region of the second surface of the metal sheet lie against one another and are joined by a second solder joint containing a flux material, wherein the counterpart region comprises an at least one unilateral solder plating having the following composition: 7-11% Si, 0-0.8% Fe, 0-1% Cu, 0.03-2.5% Mg, 0-4% Zn, 0-0.2% Ti, 0-0.5% Bi, and 0-0.2% Sr, wherein a remainder of the composition is Al, wherein the metal sheet has a core region having the following composition: 0-0.7% Fe, 0.3-1.2% Cu, 0-0.5% Cr, 0-0.3% Ti, 0-1.2% Si, 0-2.0% Mn, 0.1-1.0% Mg, 0-0.2% Zr, wherein a remainder of the composition is Al, wherein the metal sheet comprises three layers having the following structure: solder plating/core region/solder plating; and a capillary gap formed between the soldering region and the counterpart region, wherein the capillary gap comprises a contact surface, wherein at one end the capillary gap is connected to a flushing channel and at another end the capillary gap is connected to the environment, wherein the flushing channel is approximately of triangular shape having two side walls formed the second surface of the metal sheet which converge toward the capillary gap and one side wall formed by the first surface of the metal sheet, wherein the flushing channel is bounded by the counterpart region and the soldering region, wherein the flushing channel permits discharging the flux material from the second solder joint.

Description

(1) A plurality of preferred exemplary embodiments of the invention will be described and explained in further detail with reference to the accompanying drawings hereinbelow.

(2) FIG. 1 shows a first embodiment of a fluid channel according to the invention.

(3) FIG. 2 shows a second embodiment of a fluid channel according to the invention.

(4) FIG. 3 shows a third embodiment of a fluid channel according to the invention.

(5) FIG. 4 shows a fourth embodiment of a fluid channel according to the invention.

(6) FIG. 5 shows a fifth embodiment of a fluid channel according to the invention.

(7) FIG. 6 shows a fifth embodiment of a fluid channel according to the invention.

(8) FIG. 7 shows a detailed section of a fold of one of the embodiments shown in FIG. 1 to FIG. 6.

(9) FIG. 8 shows a first modification of the fold shown in FIG. 7.

(10) FIG. 9 shows a second modification of the fold shown in FIG. 7.

(11) FIG. 10 shows a further embodiment of a fluid channel according to the invention in the manner of a clip tube.

(12) FIG. 11 shows a modification of the fluid channel shown in FIG. 10 with an inserted turbulator.

(13) FIG. 12 shows a block diagram depicting one embodiment of the application. The block diagram shows connection only and is not intended to show structural features such as relative size, orientation, and spacing.

(14) FIG. 13 shows a block diagram depicting one embodiment of the application. The block diagram shows connection only and is not intended to show structural features such as relative size, orientation, and spacing.

(15) The fluid channel shown in FIG. 1 is in the form of a flat tube shaped from a single metal sheet 1. The metal sheet 1 consists of an aluminum alloy, which in the present case has a magnesium content. In the present case, although not generally necessary, it is possible for a solder plating to be applied to a core region of the metal sheet at least on the outer surface 2. For the present exemplary embodiment, and all further exemplary embodiments, the following alloys are preferred for the core region, which corresponds to the entire metal sheet if there are no solder platings, and for the solder platings (all figures in % by weight):

(16) Core Region/Base Material of the Metal Sheet:

(17) TABLE-US-00001 Minimum Preferred Maximum Al Remainder Remainder Remainder Si 0 1.2 Fe 0 0-0.4 0.7 Cu 0.1 0.3-0.8 1.2 Mn 0 2.0 Mg 0.03 0.1-0.3 1.0 Cr 0 0-0.2 0.5 Zn 0 2.5 Ti 0 0-0.10 0.3 Sn 0 0.05 Zr 0 0.2 Bi 0 0.05 Sr 0 0.05
Solder Plating:

(18) TABLE-US-00002 Minimum Preferred Maximum Al Remainder Remainder Remainder Si 5 to 6 7-11 20 Fe 0 0-0.2 0.8 Cu 0 0-0.3 1 Mn 0 0.15 Mg 0 0.03-0.8 2.5 Cr 0 0.05 Zn 0 0-2.0 4 Ti 0 0-0.10 0.2 Sn 0 0.05 Zr 0 0.05 Bi 0 0-0.20 0.5 Sr 0 0-0.05 0.2

(19) In the present case, the flat tube is in the form of a multi-chamber flat tube having two folded webs 4 and a fold 5 for closing the tube along a longitudinal direction.

(20) In the present case, the fold 5 is arranged on a broad side of the flat tube. It comprises a first fold portion 5a and a second fold portion 5b, which are each formed by bending opposing edge regions of the metal sheet 1 through 90. A respective edgefold 6 adjoins the fold portions 5a, 5b through 180. In the region of the edgefolds 6, the fold portions 5a, 5b lie against an abutment region 7 of the inner sheet metal surface 3 or inner side of the flat tube. Alongside the abutment region 7, each of the fold portions 5a, 5b forms a soldering region or a counterpart within the context of the invention.

(21) The fold portions 5a, 5b lying against one another by way of a contact surface between them form a capillary gap 8. A flushing channel 9 is shaped at the fold between the soldering region 7 and the edgefolds 6, into which flushing channel the capillary gap 8 issues and which has a greater diameter than the capillary gap 8.

(22) The webs 4 have a height which corresponds to the inside diameter of the flat tube, and lie against the surface 3 on the inside of the metal sheet 1 in an abutment region 10. The abutment region 10 is located on that side of the flat tube which lies opposite the soldering region 7, and therefore there is a particularly large distance between the abutment region 10 and the abutment region 7.

(23) The webs 4 form a structure arranged in the interior of the fluid channel within the context of the invention, which lies against the inner surface 3 of the metal sheet in the abutment region 10 in order to form a first, flux-free solder joint there.

(24) The fold 5 forms, with the fold portions 5a, 6a thereof and also the abutment region 7, a second solder joint, which is wetted with flux in a soldering operation. To this end, in the first exemplary embodiment, the entire outer broad side of the flat tube is provided with flux 11 on the side of the fold 5. The flux 11 is NOCOLOK (trade name), which has been applied by means of a paintflux process.

(25) The fold which is open before the soldering creates an open path between the two solder joints. In particular, it is possible in geometrical terms for molten flux to flow from the second solder joint directly to the first solder joint, but in actual fact this is prevented according to the invention.

(26) A fin or other structure of a stack of components which overall form a heat exchanger may be positioned on the outer side (not shown). The thus preassembled structure is placed in a soldering furnace and heated. In this case, both the first, flux-free solder joint and the second solder joint wetted with flux are soldered at the same time in the same soldering operation.

(27) At an appropriate temperature, firstly the flux applied on the outside liquefies and flows into the capillary gap 8. In the present example, the flux is present in excess. After it has flowed through the gap 8 driven by a capillary action, the flux collects in the flushing channel 9. Depending on the detail design, it may also be provided in addition, but not necessarily, that the flux is discharged from the flushing channel by way of formations at the end of the flat tube (not shown).

(28) On account of the flushing channel with a separating action, in the present case there is no wetting of the flux-free, first solder joint 4, 10. There, on account of the materials selected, flux-free soldering is effected, such that the web 4 is soldered as the structure to the opposing surface of the metal sheet. As a result of this, mechanical consolidation of the fluid channel is achieved and a plurality of separated chambers are formed.

(29) The exemplary embodiments shown in FIG. 2 to FIG. 4 differ from the first example only in that the application of flux to the outside is not effected over the whole surface area.

(30) In the example shown in FIG. 2, only selective application is effected only in parts in a wide strip over the region of the fold 5.

(31) In the example shown in FIG. 3, the flux is applied only as a streak directly in the fold capillary, the edge of the capillary being filled in.

(32) In the example shown in FIG. 4, the flux is applied in two narrow strips to each side of the fold 5. After the readily wetting flux has liquefied, it also flows into the capillary gap.

(33) In each of the examples shown in FIG. 1 to FIG. 4, the flux is applied in excess.

(34) The example shown in FIG. 5 shows an application directly to the fold portions 5a, 5b, the flux being applied during the folding of the tube or before the tube is completely folded together.

(35) FIG. 6 shows an example in which the flux has been applied to the soldering region 7 against which the edgefolds 6 lie before the tube is folded together. In this example, at least some of the applied solder is not reliably received by the flushing channel, and can, in principle, flow to the side to the webs to be soldered without flux. To avoid such undesirable wetting, in the example shown in FIG. 6 the amount of flux applied is not excessive, but rather defined. Such defined dimensioning also lends itself as a possible improvement for the example shown in FIG. 5.

(36) FIG. 7 to FIG. 9 show various variants of the edgefolds 6, which can be combined with any of the above examples. In particular, if a core region of the metal sheet contains a large amount of magnesium and is plated with solder which likewise contains magnesium, the open end face of the edge of the metal sheet can release a large amount of magnesium upon heating. The emerging magnesium could lead to an intolerable consumption of flux, with magnesium fluoride being formed in the soldered joint.

(37) The following relationship therefore preferably applies for a metal sheet thickness D, a length of the edgefold L and a tube width B:
L>2*D.

(38) The edgefold here can be bent through any angle of significantly greater than 90 (see for instance FIG. 9), in particular through 180 (see FIG. 7, FIG. 8).

(39) If the edgefold amounts to 180, the following relationship should wherever possible also be observed, in order to prevent the end edge and the opposing side of the metal sheet from being too close (see FIG. 8):
L<B2.5*D.

(40) In general, it is to be ensured expediently that the end edges of the edgefolds 6 also do not make contact with the walls of the fold portions 5a, 6a. It is preferable here to observe a safety distance of at least approximately the metal sheet thickness D. It is advantageous if the distance between a region provided with flux (coated with flux) and a region not provided with flux (not coated with flux), which are each also soldered, is approximately 2 to 4 mm, or 3 to 5.

(41) It is also advantageous if the web 4 or the webs 4 lie against the opposing inner side of the tube wall.

(42) Overall, this particularly effectively prevents magnesium from evaporating or diffusing towards undesirable regions or flux from flowing into the region of the end edges of the edgefolds 6.

(43) In the example shown in FIG. 10, the fold is not provided on the broad side of the flat tube, as in the preceding examples, but rather on the narrow side. Two opposing edges of the metal sheet 1 have a respectively part-circular bend 12, 13, such that they engage into one another in a form-fitting manner in the closed state. In this way, the flat tube is formed as a clip tube. The outer face of the bend 12 lying on the inside and the inner face of the bend 13 lying on the outside lie against one another, such that a capillary gap 8 is formed therebetween. A flushing channel with an action analogous to that in the preceding examples is formed by a void between the end of the bend 13 lying on the outside and a graduation 12a of the bend 12 lying on the inside.

(44) Flux can be applied in a manner analogous to the preceding examples to the outer face of the tube or in a targeted manner to one or both of the faces of the bends 12, 13 which are soldered to one another.

(45) Analogously to the preceding examples, the flat tube has at least two webs 4 soldered without flux in the interior thereof, such that it is constructed in the manner of a multi-chamber flat tube.

(46) FIG. 11 shows a further example, in which the fold is formed as in FIG. 10. In contrast to FIG. 10, a structure in the form of a turbulator 14 is inserted into the tube and is soldered without flux to the surface on the inside of the metal sheet 1. In the present case, the turbulator 14 is formed as a corrugated fin. It is self-evident that, depending on requirements, turbulators can also be inserted into multi-chamber flat tubes as in FIG. 10.

(47) The following alloys are preferred for a turbulator:

(48) TABLE-US-00003 Minimum Preferred Maximum Al Remainder Remainder Remainder Si 0 0.2-0.6 1.2 Fe 0 0-0.4 0.7 Cu 0 0.7 Mn 0 2.0 Mg 0 0-0.7 3.0 Cr 0 0-0.2 0.5 Zn 0 3.5 Ti 0 0.3 Sn 0 0.2 Zr 0 0.2 Bi 0 0.05 Sr 0 0.05

(49) In a very preferred configuration, the turbulator is free from magnesium (<0.03% magnesium content). This avoids evaporation of magnesium which is undesirably high on account of the often large surface of turbulators. In such a configuration, the magnesium desired for the flux-free soldering is provided entirely by the metal sheet material and/or a solder plating of the metal sheet. In principle, the turbulator may also have a solder plating.

(50) The following generally holds true: the combination of flux-free web soldering on the inner side of the tube or flux-free soldering of the inner turbulator to the inner side of the tube and flux-containing fold soldering requires suitable materials for the base material of the tube and solder plating, or, in the case of an inner turbulator, for the base material of the turbulator and turbulator solder plating.

(51) The following variants of plated and unplated joining partners are preferred: tube metal sheet solder-plated on the inside and outside, only webs and fold, no turbulator; tube metal sheet solder-plated on the inside and outside, only fold, no webs, bare turbulator; tube metal sheet solder-plated only on the outside and turbulator solder-plated on both sides.

(52) The following material concepts for the flux-free inner soldering are preferred: Material concepts in a normal 3-layer structure (100, 101) (consisting of solder/base material of the tube/solder and/or solder/turbulator material/solder), which contain certain minimum proportions of magnesium. In addition, the use of magnesium-containing alloys for the tube and the inserted turbulator constitutes a possibility to improve the strength properties of the aluminum materials used. Multi-layer concepts with a 4-layer or 5-layer structure (100, 101, 102) (consisting of solder/tube material/solder/top layer or top layer/solder/tube material/solder/top layer and analogously for the turbulator), which, on account of the mechanisms which occur in flux-free soldering, have to contain only small proportions of magnesium only in the solder (<0.10%). The base material of the tube may also contain small proportions of magnesium, but may also be selected to be completely free from Mg (<0.03%).

(53) It is self-evident that the individual features of the various exemplary embodiments can be combined with one another, depending on requirements.