Brazed heat exchanger and production method

Abstract

A brazed heat exchanger includes plates that are stacked or nested to define flow channels for multiple media. Inserts are arranged within at least some of the flow channels. Two different braze alloys having compositions based on different metals are used to form braze joints between the plates and the inserts. In some cases, a copper-based braze alloy is used for joints corresponding to flow channels for one of the media in order to provide high pressure-resisting strength to those flow channels, while an iron-based braze alloy is used for joints corresponding to flow channels for another of the media where dissolved copper is undesirable.

Claims

1. A brazed heat exchanger, comprising: stacked plates defining a plurality of ducts for two or more media to flow between the plates, the plurality of ducts including a first plurality of ducts for a first one of the media and a second plurality of ducts for a second one of the media, the first and second plurality of ducts being alternatingly arranged in the stack of plates; a first braze material providing braze joints within a first set of the plurality of ducts; and a second braze material different in composition from the first braze material providing braze joints within a second set of the plurality of ducts, the first braze material and the second braze material having matching melting temperature ranges, wherein some of the plurality of ducts are in either the first set or the second set but not both, wherein all of the first plurality of ducts belongs to the first set of ducts, wherein all of the second plurality of ducts belongs to the second set of ducts, and wherein at least one of the most distal ones with respect to a stack direction of the second plurality of ducts additionally belongs to the first set of ducts.

2. The brazed heat exchanger of claim 1, wherein the stacked plates are stacked together to form a plurality of pairs of the stacked plates, plates of each pair of the plurality of pairs being joined together along a periphery of the pair by one of the first and the second braze materials, and wherein successive pairs of the plurality of pairs are joined along the periphery by the first and the second braze materials in alternating sequence.

3. The brazed heat exchanger of claim 1, wherein adjacent ones of the stacked plates are joined along peripheries of the adjacent ones of the stacked plates, and wherein braze joints along all of the peripheries of the stacked plates are formed by one of the first and second braze materials.

4. The brazed heat exchanger of claim 1, further comprising inserts arranged in at least some of the plurality of ducts, wherein each of the inserts is joined to the plates between which the insert is arranged by at least one of the first and second braze materials.

5. The brazed heat exchanger of claim 1, wherein at least one of the ducts includes: a sealed periphery defined by edges of a first one of the plates and a second one of the plates, said edges being joined by one of the first and second braze materials; and an insert arranged within said duct and joined to both the first one of the plates and the second one of the plates by the other of the first and second braze materials.

6. The brazed heat exchanger of claim 1, wherein at least one of the ducts includes: a sealed periphery defined by edges of a first one of the plates and a second one of the plates; a first insert arranged within said duct and joined to both the first one of the plates and the second one of the plates by one of the first and second braze materials; and a second insert arranged within said duct and joined to both the first one of the plates and the second one of the plates by the other of the first and second braze materials.

7. A brazed heat exchanger for cooling oil, comprising: a brazed stack of plates defining alternating oil ducts and coolant ducts; oil inserts arranged within the oil ducts and joined to adjacent ones of the plates by way of a first braze material; first coolant inserts arranged within the coolant ducts and joined to adjacent ones of the plates by way of a second braze material that is different in composition from the first braze material; and second coolant inserts arranged within the coolant ducts and joined to adjacent ones of the plates by way of the first braze material.

8. The brazed heat exchanger of claim 7, wherein the first braze material is a copper-based braze material and the second braze material is an iron-based braze material.

9. The brazed heat exchanger of claim 7, further comprising a housing into which the brazed stack of plates is arranged, wherein the coolant ducts are open to the interior of the housing.

10. A method of making a brazed heat exchanger, comprising: providing a plurality of plates, each of the plates including a middle portion surrounded by a peripheral portion, the peripheral portion being oriented at at least one oblique angle to the middle portion; providing a first braze alloy having a first composition to a bottom surface of the middle portion of a first plate of the plurality of plates; providing a second braze alloy having a second composition different from the first composition to a bottom surface of the middle portion of a second plate of the plurality of plates; providing the first braze alloy to a top surface of the middle portion of the second plate; providing the first braze alloy to top surface of the peripheral portion of the second plate; arranging the plurality of plates into a stack in a stacking direction wherein each plate of the plurality of plates is arranged on either side of a duct to form a plurality of ducts within the stack, and wherein the first plate is arranged adjacent to the second plate; and heating the stack in a brazing furnace to a temperature that exceeds the melting temperature of both the first and the second braze alloys to at least form braze joints within each duct of the plurality of ducts and between adjacent plates of the plurality of plates.

11. The method of claim 10, wherein at least one of the first and second braze alloys is provided in a form selected from the group consisting of a paste, a powder, a foil, and a plating.

12. The method of claim 10, wherein one of the first and second compositions is a copper-based composition and the other of the first and second compositions is an iron-based composition.

13. The brazed heat exchanger of claim 1, wherein one of the first and second braze materials is a-copper-based braze material and the other of the first and second braze materials is an iron-based braze material.

14. The method of claim 10, further comprising: providing a plurality of inserts, wherein the plurality of inserts includes a plurality of first inserts; providing each of the plurality of first inserts within each of a plurality of first ducts of the plurality of ducts; and providing one of the first ducts at an uppermost location and at a lowermost location relative to the stacking direction to define an uppermost first duct and a lowermost first duct, wherein the uppermost first duct and the lowermost first duct are each formed between said first plate and said second plate.

15. The method of claim 14, further comprising: providing the second braze alloy to a top surface of the middle portion of a third plate of the plurality of plates; providing the first braze alloy to a top surface of the peripheral portion of the third plate; and stacking the third plate adjacent to the second plate and on the opposite side of the second plate relative to the first plate, wherein the duct formed between the second plate and the third plate is one of a plurality of second ducts of the plurality of ducts.

16. The method of claim 15, further comprising: arranging one of the second ducts consecutively with another of the second ducts between the uppermost first duct and the lowermost first duct in the stacking direction.

17. The method of claim 16, further comprising: arranging at least one of the first ducts between two of the second ducts between the uppermost first duct and the lowermost first duct in the stacking direction.

18. The method of claim 17, further comprising: providing each of a plurality of second inserts within each of the second ducts.

19. The method of claim 18, further comprising: wherein each of the plurality of first inserts is a corrugated fin and wherein each of the second inserts is a undulating duct sheet.

20. The method of claim 10, further comprising: providing a base plate at a lowermost end of the stack in the stacking direction; providing a cover plate at a uppermost end of the stack in the stacking direction; providing a plurality of first ducts of the plurality of ducts, each of the first ducts being defined by a first pair of adjacent plates, the first pair of adjacent plates including said first plate and said second plate; providing the second braze alloy to a top surface of the middle portion of a third plate of the plurality of plates; providing the first braze alloy to a top surface of the peripheral portion of the third plate; providing a plurality of second ducts of the plurality of ducts, each of the second ducts being defined by a second pair of adjacent plates, the second pair of adjacent plates including said second plate and said third plate; arranging a first one of the plurality of second ducts adjacent to one of the cover plate and the base plate; arranging a second one of the plurality of second ducts adjacent to a third one of the plurality of ducts; arranging a first one of the plurality of first ducts between the first one of the plurality of second ducts and the second one of the plurality of second ducts; and arranging a second one of the plurality of first ducts on the opposite side of the second one of the plurality of second ducts relative to the first one of the plurality of first ducts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an elevation sectional view through a part of a brazed heat exchanger according to an embodiment of the invention.

(2) FIG. 2 is perspective view of the heat exchanger of FIG. 1.

(3) FIG. 3 is a detail of a repeating region of the heat exchanger of FIG. 1, exaggerated in scale to highlight certain aspects of the invention.

(4) FIG. 4 is a partial perspective view of the top side of a duct sheet used in the heat exchanger of FIG. 1.

(5) FIG. 5 is a partial perspective view of the bottom side of the duct sheet of FIG. 4.

(6) FIG. 6 is a partial perspective view of a fin used in the heat exchanger of FIG. 1.

(7) FIGS. 7a and 7b are simplified assembly views of select components of the heat exchanger of FIG. 1.

(8) FIG. 8 is an elevation sectional view through a part of a heat exchanger according to another embodiment of the invention.

(9) FIG. 9 is an elevation sectional view through a brazed stack of the heat exchanger of FIG. 8, at a perpendicular orientation to the sectional view of FIG. 8.

(10) FIG. 10 is a partially exploded perspective view of the brazed stack of FIG. 9.

(11) FIG. 11 is a plan view of a flow channel of a heat exchanger according to another embodiment of the invention.

(12) FIG. 12 is a perspective view of the heat exchanger of FIG. 11, with certain parts removed to show the flow channel of FIG. 11.

(13) FIG. 13 is a partial elevation view of a fin to be used in the heat exchanger of FIGS. 11-12.

(14) FIG. 14 is a partially exploded perspective view of a heat exchanger according to an embodiment of the invention.

DETAILED DESCRIPTION

(15) Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of including, comprising, or having and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms mounted, connected, supported, and coupled and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, connected and coupled are not restricted to physical or mechanical connections or couplings.

(16) FIGS. 1 to 7a and 7b show exemplary embodiments according to the invention of heat exchangers, said exemplary embodiments relating to the type often designated as housingless heat exchangers.

(17) The illustrations of FIGS. 8 to 10 show different exemplary embodiments of another heat exchanger type, in which the stack is arranged in a housing 30.

(18) FIG. 1 can be regarded as a section through a part of a brazed heat exchanger according to the invention.

(19) FIG. 2 shows a perspective view of the heat exchanger from FIG. 1. The plates 1 have four plate openings 12.

(20) FIG. 3 is a highly abstract sketch showing only two of the ducts 2a, 2b of the heat exchanger and three of the plates 1. For this illustration, it can be assumed that the braze materials 3a, 3b are in the form of braze foils. The braze foils can be cut out over a large area such that the braze material 3a, 3b is present only at the contact surfaces (not shown). The contact surfaces are for example those marked by lines in FIGS. 4-6. In this illustration, however, it may alternatively also be assumed that the braze material 3a, 3b is provided in the form of plating.

(21) FIGS. 4 and 5 show an insert in the form of an undulating duct sheet 4b which is situated in one set of ducts 2b. One illustration shows the top side of the duct sheet 4b and the other illustration shows the underside thereof. The braze material 3b, which in this case is applied as braze paste, has been indicatednot in full but predominantlyby the thick lines.

(22) FIG. 6 shows a detail of an insert in the form of an undulating fin 4a that is situated in the other set of ducts 2a. Here, the other braze material 3a, which is likewise applied in the form of a braze paste, has been indicated by straight thick linesdashed lines on the underside (not visible in FIG. 6) of the undulation troughs 4t and solid lines on the visible top side of the undulation peaks 4bg.

(23) FIG. 7a shows a further abstract sketch of a possible embodiment on the basis of a duct 2b formed from two plates 1 (still illustrated with a spacing to one another), in which duct there is situated an undulating duct sheet 4b. On the plate edges 10 there is arranged a braze material identical to the respective duct 2a, 2b. Only one of the oil ducts 2a is shown in FIG. 7a, in a somewhat more abstract fashion, above the coolant duct 2b.

(24) In an embodiment as per FIG. 7b, the braze on the plate edges 10 isby contrast to that shown in FIG. 7aidentical for all of the plates 1 or for all of the ducts 2a, 2b. On the bent edges 10 of the plates 1 that extend around the entire plate periphery, there is provided a Cu-based braze material 3a. By contrast, a Fe-based braze material 3b is provided on the duct sheet 4b. It is self-evident that all of the ducts 2b that are assigned, in an oil cooler, to a cooling liquid have been designed in the manner of the duct 2b that is shown. By contrast, in the oil ducts 2a of said embodiment that is not shown, the Cu-based braze material 3a is provided both in the oil ducts 2a and also on the associated plate edges 10. It has been found that the relatively small amount of copper on the edges 10 does not result in copper dissolution phenomena.

(25) The undulating duct sheets 4b and the undulating fins 4a are, in an exemplary embodiment that is not shown, of physically identical form, for example designed as shown in FIG. 6.

(26) Other embodiments (not shown) of the housingless heat exchanger type have fins or duct sheets only in one set of ducts. In the other set of ducts, protuberances (studs 11) have been stamped into the plates 1, which protuberances bear against and are brazed to one another. Such embodiments will be presented and described further below on the basis of the above-mentioned other heat exchanger type as per FIGS. 8-10.

(27) In embodiments that are not shown, a mix of fins 4a and duct sheets 4b is provided in the ducts 2a and/or 2b. In such cases, the fins 4a and the duct sheets 4b which are situated jointly in one duct should be provided with an identical braze material 3a or 3b. It is also possible for a mix of fins and studs 11 to be provided in each duct 2a and 2b, or else a mix of duct sheets 4b and studs 11.

(28) Further embodiments that are not shown, and which are less preferable, have only protuberances (studs 11) in the plates 1, and therefore no fins 4a or similar inserts whatsoever in the ducts 2a, 2b. In this case, too, the braze materials 3a, 3b are provided only at the said contact surfaces, which of the surfaces on the butting protuberances. The contact surfaces likewise correspond to the brazed connection seams

(29) The application of the braze materials 3a, 3b in the form of braze paste may be realized by means of rotating drums W or by means other devices in order that said process can be carried out in an effective manner, that is to say in a manner suitable for mass production. Screen printing methods are also known and suitable for braze application. Owing to the at least two different braze materials 3a, 3b, separate production lines are expedient. Contact between the braze materials should at least be prevented.

(30) FIG. 8 shows a stack of heat exchanger plates 1 arranged in the housing 30. The plates 1 have only two plate openings 12, for example for oil. A flange 5 is situated on the opening 12 of the uppermost plate 1. The housing 30 has an inlet 31 and an outlet 32, for example for a cooling liquid CL. FIG. 9 shows a stack of said type on its own. FIG. 10 shows a stack illustrated in a partially exploded view. The uppermost duct 2b in the stack for the cooling liquid CL has been illustrated in exploded form. Furthermore, in uppermost duct 2a in the stack for oil has been illustrated a plate pair. The braze material 3b in the ducts 2b is, in this example embodiment, inserted in the form of a braze foil. In the other ducts 2a, a braze powder may be applied to the fins 4a situated therein. As shown in the figures, the ducts 2b are predominantly formed with studs 11 which are stamped into the plates 1. Opposite studs 11 are brazed to one another. It is sufficient here for the expensive braze material 3a or 3b to be applied only to the tips of the studs.

(31) FIGS. 11-13 show another exemplary embodiment using a caseless heat exchanger which has exclusively closed channels, similar to the embodiment of FIGS. 1-7. FIG. 14 shows another exemplary embodiment using a heat exchanger in a housing which has closed and open channels, similar to the embodiment of FIGS. 8-10.

(32) FIG. 11 shows a view into an uppermost channel 2a which is preferably a cooling liquid channel. A heat exchanger part 1, in particular a heat exchanger plate 1 with an obliquely raised edge 10a can be seen. The edges 10a of the plates 1 are connected in order to form the closed channels. Four holes are situated in said heat exchanger plates 1. A further heat exchanger plate 1 is laid on top in order to form the liquid channel which is shown. Said further heat exchanger plate (not shown) might also be a cover plate which normally has somewhat thicker walls than a heat exchanger plate 1. The upper left-hand and the upper right-hand hole is a part of an inlet channel and an outlet channel 14, 15, respectively. By means of said inlet and outlet channel 14, 15, the channel 2b (not shown) which is adjacent toward the bottom, preferably an oil channel, is fed. The channels 2a and 2b alternate in the vertical plate stack direction, as is usually customary at any rate. The inlet and outlet channels 12, 13, 14, 15 which are formed in this way are otherwise clearly visible in FIG. 12 which shows a perspective view of the plate stack. The lower right-hand and the lower left-hand hole and the inlet and outlet channels 12, 13 which are formed from them in the plate stack are correspondingly provided for the cooling liquid. It can accordingly be assumed that the cooling liquid flows into the cooling liquid channel 2a which is shown at the bottom right and leaves said channel 2a again at the bottom left (FIG. 11).

(33) Furthermore, as is apparent from FIGS. 11 and 12, in each case one corrugated duct sheet 4b is situated in the upper liquid channel which is shown and preferably also in all other liquid channels of the heat exchanger, on the left and right in the inlet region and in the outlet region of the liquid channel. The corrugated duct sheets 4b have two openings, each of which corresponds with one of the abovementioned holes in the plates 1. The openings are therefore slightly larger than the holes. Furthermore, the duct sheets 4b have arcuate corrugations which firstly lead from the inlet channel to a middle plate region and secondly lead from the middle plate region to the outlet channel. To this end, apertures are arranged in the duct sheets 4b at the ends of the corrugations. Where the corrugations are formed, the liquid can flow between the duct sheet 4b and the lower heat exchanger plate 1. Where the duct sheets 4b are configured without corrugations, that is to say are of planar configuration, the liquid flows between the duct sheet 4b and the upper heat exchanger plate 1. In order to further improve the stability, individual lobes 11 are also present in the corrugated duct sheets 4b.

(34) In the abovementioned middle plate or channel region, a corrugated fin 4a is situated between the two duct sheets 4b, the details of which corrugated fin 4a are shown in FIG. 13. As is known, the corrugations of the duct sheets 4a4b and the fins 4a have corresponding corrugation peaks 4bg and corrugation troughs 4t. The fin 4a has cuts in the corrugation flanks 42.

(35) All the liquid channels can be of identical configuration with regard to the above-described embodiment.

(36) The following is provided with regard to the brazing materials which are present in FIGS. 11, 12 and 13: a copper brazing material 3b, indicated in FIG. 11 merely by way of some thick, arcuate lines which lie on the corrugation peaks 4bg, is situated on the visible upper side on the corrugations of the duct sheets 4b. By way of this, the brazed connection is produced with the plate 1 (not shown) which lies on the channel 2a. The copper brazing material 3b for connecting to a bottom of the heat exchanger plate 1 which is shown is also situated on the non-visible underside of the duct sheets 4b. The copper brazing material 3b on the underside is situated on the planar areas which lie on the bottom of the heat exchanger plate 1 and which can also be understood to be corrugation troughs 4t.

(37) In contrast, an iron brazing material 3a, indicated merely by way of a single oval in FIG. 11 and by way of some lines in FIG. 13, is situated on the upper side and on the underside of the fin 4a and on its corrugation peaks 4bg and corrugation troughs 4t. Said embodiment applies to the upper channel 2a which is shown and to the lower channel 2a which is not shown.

(38) In contrast, exclusively the iron brazing material 3a is situated in all remaining channels 2a which are assigned to the cooling liquid.

(39) In one exemplary embodiment which is not shown, not only is the uppermost channel 2a configured as described with regard to the brazing materials 3a, 3b, but rather also the following liquid channel 2a.

(40) FIGS. 11 to 13 have not shown the oil channels in detail. The oil channels might be provided completely with a fin 4a (shown in FIG. 13) or might also be of some other configuration. Exclusively the copper brazing material 3b is situated therein in said exemplary embodiment, in order to withstand the high pressure on the oil side.

(41) In FIG. 11, two first part regions A have also been marked which are arranged to the left and the right of a second part region B which corresponds to the abovementioned middle plate or channel region. The part regions A correspond to the likewise abovementioned inlet and outlet regions. In contrast to the above-described embodiment, according to which merely the upper or else also the next following liquid channel is configured with both brazing materials 3a, 3b, all the liquid channels of the heat exchanger are configured with the one and with the other brazing material 3a, 3b in the alternative embodiment. The copper brazing material 3b is therefore situated in the two part regions A and the iron brazing material 3a is situated in the second part region B. Exclusively the copper brazing material 3b is also situated in all the oil channels here.

(42) FIG. 14 shows the oil channels there in somewhat greater detail. They are situated within tubes which are formed in this exemplary embodiment from pairs of plates 1 which are connected at their plate edges 10b and which therefore produce in each case one closed channel (first channel 2a). In contrast to the previous exemplary embodiment, said plates 1 have merely two openings. In each case one open channel (second channel 2b) is situated between the tubes. The housing G which is present in said exemplary embodiment and in which the stack according to FIG. 4 is situated has been indicated as a dashed-line frame, but can in general be similar to the housing 30 of FIG. 8. The open channels are flowed through by a cooling liquid which enters into the housing G and leaves the housing G again after having flowed through the open channels. The cooling liquid has been symbolized by way of block arrows and the oil by way of line arrows in FIG. 14.

(43) Exclusively a copper brazing material 3b is also situated within the oil channels in said exemplary embodiment.

(44) In each case in this embodiment, two other duct sheets 4c are situated in the open channels. In contrast to the previous exemplary embodiment, the said other duct sheets 4c have merely a single opening. They are also of corrugated configuration, however, in order that they can be flowed through just like the duct sheets 4b of the previous exemplary embodiment. The opening corresponds with one of the abovementioned two plate openings. A copper brazing material 3b is situated in the upper, open channel which is shown, whereas an iron brazing material 3a is situated in the remaining other open channels which are not shown in detail. In FIG. 14, the copper brazing material 3b has been shown as a brazing film, without being restricted hereto. It might also be, for example, a brazing paste or a brazing coating. The brazing film has been provided with cutouts, in order that the brazing material 3b is present only where it is required, for example in order to connect two lobes 11 which lie opposite one another and are configured in the plates 1, and which in each case protrude into the open channels.

(45) The basic material of those parts of the heat exchangers which are shown in the exemplary embodiments is a stainless steel. In other exemplary embodiments which are not shown, it can be, for example, an aluminum alloy or another metal which can be brazed with correspondingly different brazing materials.

(46) The heat exchangers according to the invention may, aside from being used as oil coolers, be advantageous for all possible applications, in particular for applications in which it is sought to eliminate certain metallic elements, such as in this case copper, for example.

(47) Various alternatives to the certain features and elements of the present invention are described with reference to specific embodiments of the present invention. With the exception of features, elements, and manners of operation that are mutually exclusive of or are inconsistent with each embodiment described above, it should be noted that the alternative features, elements, and manners of operation described with reference to one particular embodiment are applicable to the other embodiments.

(48) The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.