CN110567309A

CN110567309A - flat tube for heat exchanger and heat exchanger

Info

Publication number: CN110567309A
Application number: CN201810584896.0A
Authority: CN
Inventors: C·M·卡利索; 张萍; 马伟增
Original assignee: Granges Aluminium Shanghai Co Ltd
Current assignee: Granges Aluminium Shanghai Co Ltd
Priority date: 2018-06-06
Filing date: 2018-06-06
Publication date: 2019-12-13

Abstract

The invention relates to a flat tube for a heat exchanger, comprising a tube wall which is formed by bending a first material strip and a fin which is inserted into the tube wall and is formed by a second material strip and has an undulating structure, wherein the tube wall comprises a first section and a second section which are flat and are arranged opposite to each other in a parallel manner, the first section and the second section are connected to each other by two connecting ends, one of the connecting ends is formed by a third section forming a bending transition, the other connecting end is formed by overlapping a fourth section and a fifth section of two free ends of the first material strip, the fin has a first end and a second end which are opposite to each other, the contour of the first end is positioned on the third section in a matching manner, and the contour of the second end is positioned between the fourth section and the fifth section in a matching manner. The invention also relates to a heat exchanger comprising such a flat tube. The flat pipe is easy to manufacture, low in cost and good in corrosion resistance and impact strength.

Description

Flat tube for heat exchanger and heat exchanger

Technical Field

the present invention relates to a flat tube for a heat exchanger, in particular a brazed condenser or evaporator, and to a heat exchanger comprising such a flat tube.

background

Flat tubes for heat exchangers have a number of different designs in the prior art.

The most common flat tubes used in heat exchangers, particularly condensers or evaporators, are typically multiport extruded tubes (MPE). However, the solution using a multi-port extruded tube is costly to manufacture and does not have sufficient corrosion resistance in some applications.

It is also known to use welded pipes (optionally with inserts) which are usually manufactured by means of high-frequency welding. However, such welded pipes have a limit to the minimum thickness of the pipe wall due to the welding process, are somewhat complicated to manufacture and are relatively expensive.

It is also known to use a single folded tube formed by the individual folding of an aluminium strip, which does not comprise intermediate fins, and therefore there are also limits to the minimum thickness of the tube wall, the use of more material and the size and number of ports.

Also known are folded tubes with internal fins made of multiple parts, such as flat tubes with "B" shaped external walls, shown by CN103080685A, and flat tubes with side double layer joints, shown by CN 104583703B. However, these flat tubes have the disadvantage of being generally sensitive to soldering and corrosion at the joint location, of being less stable and of not having sufficient corrosion resistance and impact strength.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a flat tube for a heat exchanger, which is easy to manufacture, low in cost and good in corrosion resistance and impact strength.

To this end, a first aspect of the invention provides a flat tube for a heat exchanger, comprising a tube wall which is formed by bending a first material strip and into which a fin which is formed by a second material strip and has an undulating structure is inserted, the tube wall comprising a first section and a second section which are arranged flat and opposite one another in a parallel manner and which are connected to one another by two connecting ends, one of which is formed by a third section which forms a bend transition and the other of which is formed by overlapping a fourth section and a fifth section of the two free ends of the first material strip, the fin having opposite first and second ends, the first end having a contour which is positioned fittingly on the third section and the second end having a contour which is positioned fittingly between the fourth and fifth sections, the peaks and troughs of the undulating structure are positioned on the inner wall of the first and second sections, respectively, inside the tube wall.

According to a preferred embodiment of the invention one of the surfaces of the tube wall is covered with a brazing layer or both surfaces of the tube wall are covered with brazing layers.

According to a preferred embodiment of the invention, the outer surface of the tube wall is clad with a brazing layer, and both surfaces of the fin are clad with brazing layers.

The braze layer is preferably an aluminium alloy preferably containing 2-15% by weight (more preferably 4-14% by weight) silicon.

According to a preferred embodiment of the invention the brazing layer on the outer surface of the tube wall contains 0.5-5.0% by weight zinc; more preferably, the brazing layer on the outer surface of the tube wall contains 0.5-3.0% by weight zinc.

According to a preferred embodiment of the invention, the second strip of material forming the fin is an aluminium alloy, preferably containing 0.1-1.2% by weight of copper; more preferably, the second strip of material forming the fin contains 0.2-1.0% copper by weight.

According to a preferred embodiment of the present invention, at least one of the third section, the fourth section, and the fifth section is provided in a circular arc shape, an angular shape, or a planar shape.

according to a preferred embodiment of the invention, the flat tubes have a height of between 0.5 and 3mm and a width of between 8mm and 50 mm.

According to a preferred embodiment of the invention, the crests and troughs of the wave-like structure form surface or point contacts with the inner walls of the first and second segments, respectively.

According to a preferred embodiment of the invention, both the first strip of material and the second strip of material are made of an aluminium alloy.

A second aspect of the invention provides a heat exchanger comprising flat tubes according to the first aspect of the invention.

According to a preferred embodiment of the invention, the heat exchanger is a condenser or an evaporator.

Compared to the prior art (mainly MPE), the flat tube for a heat exchanger according to the invention has at least the following advantages:

Less material is consumed and therefore less weight and lower cost;

Easy to manufacture;

-forming a stable and strong structure before brazing;

-has good brazing properties;

-the corrosion resistance at the braze joint formed by the overlapping of the two ends of the first material strip with each other is increased by the choice of material;

The impact strength is increased by the double-walled structure of the air inlet end.

Drawings

Other features and advantages of the present invention will be better understood by the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts.

Fig. 1 is a schematic cross-sectional view of a preferred embodiment of a flat tube for a heat exchanger according to the invention;

Fig. 2 is a schematic cross-sectional view of a first variant of a flat tube for a heat exchanger according to the invention;

fig. 3 is a schematic sectional view of a second variant of a flat tube for a heat exchanger according to the invention;

Fig. 4 is a schematic sectional view of a third variant of a flat tube for a heat exchanger according to the invention;

Detailed Description

The practice and use of the embodiments are discussed in detail below. It should be understood, however, that the specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

with reference to fig. 1, a flat tube for a heat exchanger, in particular a brazed condenser or evaporator, according to the invention comprises a tube wall 1 which is formed by bending a first strip of material, which is usually made of an aluminum alloy and has a thickness d1 of typically between 0.15mm and 0.35 mm. The tube wall 1 comprises a first section 11 and a second section 12 which are flat and are arranged opposite one another in a parallel manner so as to form two flat side walls in the width direction of the flat tube. The first section 11 and the second section 12 are connected to each other by two connecting ends, one of which is formed by a third section 13 constituting a bend transition, and the other of which is formed by a fourth section 14 and a fifth section 15 of the two free ends of the first material strip overlapping each other to constitute an overlapping joint.

In the preferred embodiment shown in fig. 1, the two connecting ends of the pipe wall 1 have the shape of a circular arc. This is not limitative, however, and in fact at least one of the third section 13, the fourth section 14 and the fifth section 15 of the pipe wall 1 is provided in the shape of a circular arc, an elbow (variant shown in fig. 3) or a flat surface (variant shown in fig. 4).

Advantageously, the first strip of material (tube wall 1) is produced by semi-continuous direct-chill casting, continuous casting, twin-roll casting or strip casting of an aluminium alloy preferably containing silicon (0-1.5% by weight), iron (0-1.5% by weight), copper (0-1.5% by weight), manganese (0.5-2.0% by weight), magnesium (0-0.5% by weight), zinc (0-1.0% by weight), nickel (0-1.5% by weight), zirconium (0-0.3% by weight), titanium (0-0.3% by weight), chromium (0-0.3% by weight), vanadium (0-0.3% by weight) and others (0-0.2% by weight) (more preferably, silicon (0-1.2% by weight), iron (0-1.2% by weight), and then by rolling, Copper (0-1.2% by weight), manganese (0.6-1.8% by weight), magnesium (0-0.3% by weight), zinc (0-0.5% by weight), nickel (0-1.0% by weight), zirconium (0-0.2% by weight), titanium (0-0.2% by weight), chromium (0-0.2% by weight), vanadium (0-0.2% by weight), and others (0-0.1% by weight each, 0-0.5% by weight in total).

Fins 2, formed by a second strip of material, generally made of aluminium alloy and having a thickness d2 of generally less than 0.15mm and having a corrugated structure, are inserted inside the tube wall 1. Each peak and each valley of said undulated structure is positioned on the inner wall of the first section 11 and the second section 12, respectively, inside the tube wall 1. The corrugated fin 2 has opposite first and second ends 21 and 22, the first end 21 having a profile fittingly positioned over the third section 13 and the second end 22 having a profile fittingly positioned between the fourth and fifth sections 14 and 15.

In the preferred embodiment shown in fig. 1, the peaks 23 and valleys 24 of the undulating structure each have a planar shape so as to make surface contact with the inner walls of the first section 11 and the second section 12, respectively. This is not limitative, however, as in the variant shown in fig. 2, the peaks 23 and valleys 24 of the wavy structure form point contacts with the inner walls of the first 11 and second 12 segments, respectively.

Advantageously, the second strip of material (fin 2) is produced by semi-continuous direct chill casting, continuous casting, twin roll casting or strip casting of an aluminium alloy preferably containing silicon (0-1.5% by weight), iron (0-1.5% by weight), copper (0-1.2% by weight), manganese (0.5-2.0% by weight), magnesium (0-0.25% by weight), zinc (0-2.0% by weight), nickel (0-1.5% by weight), zirconium (0-0.3% by weight), titanium (0-0.3% by weight), chromium (0-0.3% by weight), vanadium (0-0.3% by weight) and others (0-0.2% by weight) (more preferably, silicon (0-1.2% by weight), iron (0-1.2% by weight), and then by rolling, Copper (0-1.0% by weight), manganese (0.6-1.8% by weight), magnesium (0-0.1% by weight), zinc (0-1.5% by weight), nickel (0-1.0% by weight), zirconium (0-0.2% by weight), titanium (0-0.2% by weight), chromium (0-0.2% by weight), vanadium (0-0.2% by weight), and others (0-0.1% by weight each, 0-0.3% by weight in total).

In the cross section shown in fig. 1, the width of the flat tubes corresponds to the overall dimension of the flat tubes in the direction of the undulation extension of the undulated structure (including the wall thickness), while the height of the flat tubes corresponds to the overall dimension of the flat tubes in the direction perpendicular to the direction of the undulation extension (including the wall thickness). For example, the flat tubes have a height d3 of between 0.5 and 3mm, preferably between 1 and 2mm, and a width d4 of between 8mm and 50mm, preferably between 10mm and 30 mm. The number of undulations of the fin 2 is at least equal to the number of millimetres of the width d4 of the flat tube, for example, the number of undulations of the fin 2 is equal to or greater than 20 when the width d4 of the flat tube is equal to 20 mm.

one or both surfaces of the tube wall 1 are covered with a brazing layer, preferably the outer surface of the tube wall 1 is covered with a brazing layer; the second strip of material forming the fin 2 may or may not be clad with a brazing layer, preferably on both surfaces of the fin 2.

Advantageously, the brazing layer on the tube wall 1 consists of an aluminium alloy preferably containing silicon (2.0-15.0% by weight), iron (0-1.0% by weight), copper (0-1.0% by weight), manganese (0-1.0% by weight), magnesium (0-0.25% by weight), zinc (0-5.0% by weight) and others (0-0.2% by weight) (more preferably, silicon (4.0-14.0% by weight), iron (0-0.7% by weight), copper (0-0.7% by weight), manganese (0-0.7% by weight), magnesium (0-0.1% by weight), zinc (0-3.0% by weight) and others (0-0.1% by weight).

Also advantageously, the brazing layer on the fin 2 is composed of an aluminum alloy preferably containing silicon (2.0-15.0% by weight), iron (0-1.0% by weight), copper (0-1.0% by weight), manganese (0-1.0% by weight), magnesium (0-0.25% by weight), zinc (0-2.0% by weight) and others (0-0.2% by weight) (more preferably, silicon (4.0-14.0% by weight), iron (0-0.7% by weight), copper (0-0.7% by weight), manganese (0-0.7% by weight), magnesium (0-0.1% by weight), zinc (0-1.5% by weight) and others (0-0.1% by weight).

Preferably, the brazing layer on the outer surface of the pipe wall 1 needs to contain zinc (0.5-5.0% by weight, more preferably 0.5-3.0% by weight). After brazing, the brazing layer containing zinc increases the corrosion potential difference between the outer surface and the central part of the pipe wall 1, in other words, the brazing layer containing zinc establishes a corrosion potential gradient from the outer surface to the central part. The corrosion potential difference/corrosion potential gradient improves the surface transverse corrosivity of the flat tube, and prolongs the local corrosion time of the flat tube, thereby prolonging the service life of the flat tube. The following table provides an example of the corrosion potential difference for a particular flat tube material.

When zinc is contained in the brazing layer, a large amount of zinc accumulates at the joint of the pipe wall 1 after brazing, which results in a lower corrosion potential at the joint than in other areas of the periphery, thus causing faster corrosion. As a result, the joints of the flat tubes are prematurely corroded. The brazing layer containing zinc improves the surface cross-corrosion of the flat tubes, but is detrimental to the corrosion resistance of the joint.

It is therefore also preferred that the second strip of material forming the fins 2 itself contains copper (0.1-1.2% by weight, more preferably 0.2-1.0% by weight). When the second end 22 of the fin 2 is positioned between the fourth section 14 and the fifth section 15 of the tube wall 1, copper in the second end 22 diffuses into the brazed joint during brazing to increase the corrosion potential at the joint (i.e., neutralizes the effects of zinc), thereby overcoming the problem of premature corrosion at the joint and increasing the corrosion resistance at the joint.

In the manufacture of flat tubes according to the invention, a first strip of material forming the tube wall 1 is first folded into the overall shape shown in fig. 1, and then the corrugated fins 2 formed from a second strip of material are inserted before the overlapping joints of the tube wall 1 are folded.

Thereafter, in the manufacture of the heat exchanger according to the present invention, brazing the fin 2 to the tube wall 1 in the heat exchanger integral brazing process includes brazing the first end 21 of the fin 2 to the third section 13, brazing the second end 22 between the fourth and fifth sections 14 and 15, and brazing each of the crests 23 and each of the troughs 24 of the undulating structure to the first and second sections 11 and 12, respectively.

while the technical content and the technical features of the invention have been disclosed, it is understood that various changes and modifications of the disclosed concept can be made by those skilled in the art within the spirit of the invention, and the invention is not limited thereto.

the above description of embodiments is intended to be illustrative, and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. flat tube for a heat exchanger, comprising a tube wall (1) which is formed by bending a first material strip and a fin (2) which is inserted into the tube wall (1) and is formed from a second material strip and has an undulating structure, characterized in that the tube wall (1) comprises a first section (11) and a second section (12) which are flat and are arranged opposite one another in a parallel manner, the first section (11) and the second section (12) being connected to one another by two connecting ends, one of which is formed by a third section (13) which forms a bending transition and the other by a fourth section (14) and a fifth section (15) which are two free ends of the first material strip overlapping one another, the fin (2) having a first end (21) and a second end (22) which are opposite one another, the first end (21) being positioned with a contour adapted on the third section (13), the second end (22) is profiled to be positioned between the fourth section (14) and the fifth section (15), and the wave crests (23) and wave troughs (24) of the wave structure are positioned on the inner wall of the first section (11) and the second section (12), respectively, inside the tube wall (1).

2. Flat tube according to claim 1, characterised in that one of the surfaces of the tube wall (1) is coated with a brazing layer or both surfaces of the tube wall (1) are coated with a brazing layer.

3. Flat tube according to claim 2, characterised in that the outer surface of the tube wall (1) is coated with a brazing layer and that both surfaces of the fin (2) are coated with brazing layers.

4. Flat tube according to claim 3, characterised in that the brazing layer on the outer surface of the tube wall (1) contains 0.5-5.0% by weight of zinc.

5. Flat tube according to claim 4, characterised in that the brazing layer on the outer surface of the tube wall (1) contains 0.5-3.0% by weight of zinc.

6. Flat tube according to claim 3, characterised in that the second strip of material forming the fin (2) contains 0.1-1.2% by weight of copper.

7. Flat tube according to claim 6, characterised in that the second material strip forming the fin (2) contains 0.2-1.0% by weight of copper.

8. Flat tube according to one of claims 1 to 7, characterised in that at least one of the third section (13), the fourth section (14) and the fifth section (15) is provided in the shape of a circular arc, an elbow or a plane.

9. Flat tube according to one of claims 1 to 7, characterized in that the flat tube has a height (d3) of between 0.5 and 3mm and a width (d4) of between 8mm and 50 mm.

10. Flat tube according to one of claims 1 to 7, characterised in that the peaks (23) and valleys (24) of the undulated structure form a surface or point contact with the inner wall of the first section (11) and the second section (12), respectively.

11. Flat tube according to one of claims 1 to 7, characterized in that the first material strip and the second material strip are both made of an aluminum alloy.

12. A heat exchanger comprising a flat tube according to any of claims 1 to 11.

13. The heat exchanger of claim 12, wherein the heat exchanger is a condenser or an evaporator.