DE8419338U1 - Cross-flow plate heat exchanger - Google Patents

Description

PB3283/1686 - 1 -

Cross-flow plate heat exchanger

The invention relates to a cross-flow plate heat exchanger in which heat can be transferred from a hot gaseous medium flowing through it to another gaseous medium to be heated.
5

The problem underlying the invention is explained below with reference to Fig.1. Fig.1 shows a schematic representation of a conventional plate heat exchanger 1,

which is blown in the direction of arrow 2 by a hot, heat-!

releasing gaseous medium in corresponding channels, ] and in the direction of arrow 3 is flowed through by a gaseous medium to be heated, j also in corresponding flow channels crossing with the aforementioned. The heat-emitting medium enters the cross-flow plate heat exchanger 1 at a temperature of about 900 ⁰ C to 1100 ⁰ C and exits it at the other end at a temperature of 200 ⁰ C to 250 ⁰ C. The medium to be heated is thereby brought from about room temperature to a temperature of about 800 ⁰ C to 950 ⁰ C. Due to this temperature ratio, this conventional cross-flow plate heat exchanger 1 in the area of the corner marked with 4 has a temperature gradient of over 1 000 ⁰ C; the latter because in this corner 4

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PB3283/1686 - 2 -

on the one hand a medium at 900 ⁰ C to 1100"C flows past and on the other hand a cold medium at only about room temperature flows past immediately adjacent to it. Previously known cross-flow plate heat exchanger designs could not withstand this strong temperature difference because the components adjacent to the area of corner 4 warped and developed such forces that the parts cracked at the soldering and welding points. Attempts were made to eliminate this problem by using particularly high-quality materials for the manufacture of the plate heat exchanger parts; however, even with plate heat exchanger parts made of highly heat-resistant and thermal shock-resistant superalloys (nickel or cobalt-based alloys) no success was achieved; although the service life of a cross-flow plate heat exchanger manufactured in this way could be extended, the warping of the plate exchanger parts and the cracking of the material-fit connections in the area of the critical corner 4 could not be prevented.

Based on this problem, the object of the invention is to create a cross-flow plate heat exchanger with which temperature differences of 600°C and more between the gaseous medium to be heated and the heat-emitting gaseous medium can be controlled in such a way that no disadvantageous deformation of the heat exchanger parts or even a break in the material connections between the individual heat exchanger parts at particularly critical points can occur.

This object is achieved according to the invention by a cross-flow plate heat exchanger with features as specified in claim 1. Advantageous embodiments and further developments of this solution

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* PB3283/1684 - 3 -

« are identified in the subclaims.

As a result of the two-stage design of the cross-flow plate heat exchanger according to the invention, only temperature differences between the media flowing through crosswise can occur in each stage of the same, which are considerably smaller than in a single-stage design. These smaller temperature differences resulting from the two-stage design of the cross-flow plate heat exchanger can then also be compensated for by the material, so that undesirable warping of the heat exchanger plates at the points with the greatest temperature difference or even tearing of the material-bonded connections at these points can no longer occur.

In addition, the division of the cross-flow plate heat exchanger into a preheating stage and a final heating stage allows a particularly simple and cost-effective construction of the same, namely as stated in the characterizing part of claim 1.

20

A cross-flow plate heat exchanger designed according to the invention is described in more detail below using the illustrations from Fig.2 to Fig.8 of the drawing. The drawing shows:

25

Fig.1 schematically shows a cross-flow

Plate heat exchanger of known design in connection with the temperatures effective in it when two gaseous media flow through it,

Fig.2 an embodiment of a

Cross-flow plate heat exchanger according to the invention in conjunction with

Ijj: 35 which in him by flowing through two

gaseous media effective temperatures,

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PB3283/1686 - 4 -

Fig.3 another embodiment of a

Cross-flow plate heat exchanger according to the invention in connection with temperatures acting in it when two gaseous media flow through it,

Fig.4 partially schematic in plan view

a heat exchanger plate used in a cross-flow plate heat exchanger according to the invention,

Fig.5 a section through the heat exchanger plate shown in Fig.4 along the section line VV,
15

Fig.6 a section through the heat exchangers

plate according to Fig.4 along the section line VI-VI shown there,

Fig.7 perspective and partially schematic

and not to scale the heat exchanger plates and edge strips as they are used in the heat exchanger construction according to the invention for each stage and together

be joined,

Fiij.8 in perspective, partly schematic and

not to scale the parts of Fig.7 after they have been assembled.

In the figures, identical or corresponding components are designated by identical reference symbols.

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PB3283/1686 - 5 -

A cross-flow plate heat exchanger designed according to the invention is designed in two stages and consists, as can be clearly seen from Figures 2 and 3, of two plate packs 5, 6 connected in series in the flow direction of each of the two gaseous media flowing through, of which the first (5) forms a preheating stage and the second (6) a final heating stage for the gaseous medium to be heated flowing through in the direction of arrow 7. The hot, gaseous medium giving off heat to the medium to be heated flows through these two plate packs 5 and 6 in cross-flow in the direction of arrow 8. The gaseous medium to be heated can be, for example, air required for combustion and the hot, gaseous medium giving off heat can be the exhaust gases or flue gases arising from a combustion process. The plate pack 5 forming the preheating stage is spatially spaced from the plate pack 6 forming the final heating stage and is connected to the latter via two transfer channels, namely a transfer channel 9 for transferring the medium to be heated and a transfer channel for transferring the heat-emitting medium. The connection of the transfer channels 9, 10 to the two plate packs 5 and 6 is such that the medium entering at one end face 11 of the plate pack 6 forming the preheating stage, flowing through it to absorb heat and exiting at the other end face 12 can be fed via the first transfer channel 9 to the inlet formed by the end face 13 of the plate pack 6 forming the final heating stage. After flowing through the plate pack 6, the medium to be heated exits again at the end face 14 of the same. The heat-emitting gaseous medium enters the transverse side 15 of the plate package 6 forming the final heat stage, flows through it, then exits from it at its other transverse side 16 and

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PB3283/1686 - 6 -

into the second transfer channel 10, then enters the transverse side 17 of the plate pack 5 forming the preheating stage and, after flowing through, exits again at the opposite transverse side 18. The temperature conditions are such that the heat-emitting gaseous medium enters the plate pack 6 forming the final heating stage at a temperature of about 600 ⁰ C to 1100 ⁰ C, gives off heat as it flows through it and still has a temperature of about 350 ⁰ C to 550 ⁰ C at the exit of the plate pack 6 and in the area of the transfer channel 10 and at the inlet of the plate pack 5 forming the preheating stage, then continues to give off heat in the plate pack 5 as it flows through it and, after

[ let it reach a temperature of about 200 ⁰ C

to 250 ⁰ C. With a medium flowing through at such temperatures and releasing heat, heat can be transferred to the medium to be heated, which is flowing through crosswise and is to be heated, in such a way that the medium enters the plate pack 5 forming the preheating stage at room temperature, i.e. at a temperature of up to about 50 ⁰ C, and is preheated therein to a temperature of about 250 "C to 450 ⁰ C, which it still has at the exit and in the first transfer channel 9 and at the entrance of the plate pack 6 forming the final heating stage. When it then flows through the plate pack 6, the medium to be heated is further heated to a temperature of about 500 ⁰ C to 950 ⁰ C, which it then has at the exit. Due to this two-stage design of the cross-flow plate heat exchanger, only temperature differences can occur at the critical end areas of the two plate packs 5 and 6, which are tightened with or 20.

occur which are lower than 650 ⁰ C and are therefore controllable by the material.

According to another criterion of the invention

Both plate chains 5 and 6 consist of

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PB3283/1686 - 7 -

a plurality of thin plates 21, which are provided within a flat, circumferential edge region 22 to increase the surface area with straight and parallel beads on both sides, inclined to the flow direction of the medium, with a height of half the height h. of a

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flow channel corresponding height h^, and

narrow edge strips 23 with a thickness h _R corresponding to the height h" of the 1Γ flow channels.

Details of the plates 21 can be seen in Figures 4 to 6. In Figure 4, the beads formed within the edge area 22 in the plates 21 are shown only by dot-dash lines, while in Figures 5 and 6 the actual design of the plates 21, including the formation of the beads 24, are clearly visible.

In Figures 5 and 6, the height of the beads 24 is indicated between arrows with h&rdquor;. The height h_ of the edge strips 23 indicated between arrows in Fig. 7

is, like the height h _v of a flow channel 25 or 26 shown in Fig. 8 but exaggerated there, twice as large as the height h" of the beads (h = h =2 h"). As can also be clearly seen from Figures 7 and 8, the plates 21 of a plate package 5 or 6 are stacked alternately on top of one another to form flow channels 26 with heating channels 27 through which heat-emitting medium flows, and to form flow channels with heat absorption channels 28 through which medium to be heated flows, in such a way that a plate 21 rotated by 180° rests with its top side 29 on the top side 29 of a plate 21 and the next plate 21 rests with its bottom side 30 on its top side 30, and immediately afterwards.

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so that the beads 24 of two superimposed
Plates 21 cross and rest against each other at certain points in the intersection area. For lateral limitation
of each flow channel 25 and 26, which is limited at the top and bottom by a plate 21, is between

two stacked plates 21 into each other -,

opposite flat strips of the edge areas 22 | one edge strip 23 is inserted. The pre-assembled, I

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are at the overlapping areas of the strips 23, i.e. §

the corner areas of the plate packages 5 and 6, I

which is welded, and also along the strips 23 |

soldered together. |

Below are various design options, | details, of the two plate packages 5 and 6 1

A plate package can be higher,
thus composed of several plates 21 , i stacked on top of each other as the other plate package, '

In particular, the plate pack 6 forming the final heating stage can be composed of several plates 21 stacked on top of each other, as the preheating stage
forming plate package 5.

Furthermore, the one plate package can be composed of plates 21 which are different in length and width, and thus in
their effective surface, are larger than the plates 21 from which the other plate package is formed.
In particular, the plate heat exchanger forming the final heat stage

package 6 in its length and width, hence its

effective surface, larger plates 21 than the plate package forming the preheating stage 5. j

In addition, the beads 24 on the plates 21 and
the edge strips 23 of one plate package a
other height than the corrugations 24 type the plates 21 And the

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PB3283/1686 - 9 -

edge strips 23 used in the other plate pack. In particular, the beads 24 on the plates 21 and the edge strips 23 used in the plate pack 5 forming the preheating stage have a smaller height than the beads 24 on the plates 21 and the edge strips 23 used in the plate pack 6 forming the final heating stage.

Furthermore, one plate package can be composed of edge strips 23 ^and plates 21 which are made of better quality material than the plates 21 and edge strips 23 of the other plate package. This measure is particularly suitable for the plate package 6 forming the final heating stage, which can be composed of edge strips 23 and plates 21 which are made of material which is significantly more heat-resistant than the plates 21 and edge strips 23 of the plate package 5 forming the preheating stage.

In the case where the two plate packages 5 and have flow channels 25 and 26 of different heights, the plates 21 for the plate package with the lower height flow channels can be easily produced by using the same embossing tool to make the beads 24 less pronounced, i.e. less high; the edge strips 23 adapted to the lower bead height must be used accordingly.

The plate packs 5 and 6 shown in the drawing are composed of rectangular plates 21. The plates 21 can, however, also have a different shape than rectangular at any time, which together with corresponding edge strips 23 enables the formation of intersecting flow channels 25, 26.

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PB3283/1686 - 10 -

In the embodiment shown in the drawing, the rectangular plates 21 have long sides with a length that corresponds to approximately 1.5 times the length of the wide sides; the edge strips 23, each delimiting a flow channel 26, extend along the wide sides of the plates 21, and the edge strips 23, each delimiting a flow channel, extend along the long sides of the plates 21 in the flat edge area 22 of the plates 21. The edge strips 23 are preferably so long and so wide that they are arranged between two plates 21, set back by approximately 0.5 mm from the edge of the plate; this creates a channel due to the slight overhang of the plates 21 over the outside of each edge strip 23, which ensures a favorable solder flow and also prevents solder material from running away in an uncontrolled manner during soldering and reaching undesirable places.

The rectangular plates 21 shown in the drawing have beads 24 which form an angle of approximately 30° with the long sides of the plates - see the corresponding angle entry in Figure 4 -; in addition, these plates 21 are arranged in the respective plate package 5 or 6 primarily in such a way that the beads 24, as can be clearly seen in Figure 7, form an angle of 60° to the flow direction of the heat-emitting medium in a flow channel 26 through which a heat-emitting medium flows, and the beads in a flow channel 25 through which a heat-absorbing medium flows form an angle of 30° to the flow direction of the heat-absorbing medium.

A particularly compact and thus space-saving design is achieved when the two plate packages 5 and are arranged as shown in Fig.2, i.e. the

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PB3283/1686 - 11 -

the outlet for the medium to be heated is located at the plate pack 5 forming the preheating stage on the same side as the outlet for the medium to be heated is located at the plate pack 6 forming the final heating stage; in this case, the transfer channel 9 must be designed in such a way that the heat-absorbing medium to be passed through can be deflected twice by 90 " in it. A particularly favorable arrangement, which enables simple transfer channels 9, 10, is provided when the two plate packs 5 and 6 are at least parallel to one another with their long sides; however, the front side 12 of the plate pack 5 forming the preheating stage, from which the medium to be preheated emerges after flowing through the latter, and the front side 13 of the plate pack 6 forming the final heating stage, into which the medium to be heated subsequently enters, can also be arranged in one plane, so that a simple, box-shaped transfer channel 9 can be used for this flow path. Likewise, the transfer channel 10, which is located between the front side 16 of the plate pack 6 forming the final heating stage, from which the heat-emitting medium emerges after flowing through the latter, and the front side 17 on which the plate pack 5 forming the preheating stage, into which the heat-emitting medium subsequently enters, extends, be box-shaped.

The two plate packs 5 and 6 can alternatively be offset from each other, as shown for example in Fig.3, and arranged in such a way that each medium, after leaving the plate pack 5 or 6 through which it first flows in the direction of flow, is diverted in the respective transfer channel 9 or 10 and then flows through the downstream plate pack 5 or 6 in a direction that is at an angle of less than 180° to the previous flow direction. In the case of the embodiment according to Fig _{. 4} i, this is

90°, that is, the two plate packages 5 and 6

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PB3283/1686 - 12 -

are arranged offset by 90° from each other and are connected to each other by appropriately designed transfer channels 9 and 10.

In general, i.e. regardless of the respective arrangement of the two plate packages 5 and 6, the two necessary transfer channels 9 and 10 are limited either by rigid walls or by walls that are movable in themselves or by at least partially rigid but movably connected wall parts.

In a specific case, the plate packages 5 and 6 each consist of approximately 150 plates 21 stacked on top of one another, these plates having an O hole of 0.2 mm and beads with a pronounced height h _g of approximately 2 mm.

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Claims (23)

PB 3283/1686 - 1 - affiisprüche: 1. Cross-flow plate heat exchanger in which heat from 1 a hot, gaseous medium flowing through another gaseous medium to be heated is transferable, characterized in that - that it is two-stage and consists of two plate packs (5, 6) connected in series in the flow direction of each of the two media flowing through, one (5) of which forms a preheating stage and the other (6) a final heating stage, furthermore the plate pack (5) is spatially spaced from the other plate pack (6) and is connected to the latter by two transfer channels (9, 10) - one for each medium - in such a way that the heat-absorbing medium, after flowing through the plate pack (5), flows via the first transfer channel (9) can be fed to the inlet of the plate pack (6), while the heat-emitting medium can be fed to the inlet of the plate pack (5) after flowing through the plate pack (6) via the second transfer channel (10), and - that both plate packages (5, 6) are composed of a) a plurality of thin plates (.21) which, within a flat, peripheral edge region (22), are provided with beads (24) which are formed on both sides obliquely to the flow direction, run straight and parallel to one another and have a height (h _g ) corresponding to half the height (h&rdquor;) of a flow channel (25, 25) in order to increase the surface area, and b) narrow edge strips with a thickness (h&rdquor; ) corresponding to the height (h&rdquor;) of the flow channel (25 or 26), &bull; · «ft 1 · &Tgr;· «&diams;· PB3283 /1686-2~ wherein the plates (21) are stacked alternately on top of one another to form flow channels (26) with heating channels (27) through which heat-emitting medium flows and to form flow channels (25) with heat absorption channels (28) through which medium to be heated flows, such that a plate (21) rotated by 180° rests with its top side (29) on the top side (29) of a plate (21) and the next plate (21) rests with its bottom side (30) on the top side (29) of the next plate (21) and the bottom side (30) of the next plate (21) rests immediately on the top side (29) of the plate (21) and thus the beads (24) of two plates (21) lying on top of one another cross and rest against one another at certain points in the crossing area, and wherein for the lateral delimitation of each flow channel (25, 26) delimited at the top and bottom, a Edge strip (23) is inserted, which pre-assembled, stacked plates (21) and edge strips (23) are welded together at the overlapping areas of the edge strips (23) and soldered together along the edge strips (23). 2. Cross-flow plate heat exchanger according to claim 1, characterized in that the two plate packs (5 and 6) are identical. 3. Cross-flow plate heat exchanger according to claim 1, characterized in that the two plate packs (5, 6) are different from one another. 4* Cross-flow plate heat exchanger according to claim 3, characterized in that one plate package is higher, i.e. consists of several stacked ■«*«««· ·44 4 «« «*»4 4«44 PB3283/1686-3- plates than the other plate package * 5. Kfeuzström plate heat exchanger according to claim 4, characterized in that the plate pack (6) forming the final heating stage is higher, i.e. has several plates (21) stacked on top of one another, than the plate pack (5) forming the preheating stage. 6. Cross-flow plate heat exchanger according to one of claims 3 to 5, characterized in that one plate pack is composed of plates which are larger in length and width, and thus in their effective surface, than the plates (21) from which the other plate pack is formed. 7. Cross-flow plate heat exchanger according to claim 6, characterized in that the plate pack (6) forming the final heating stage is composed of plates (21) which are larger in their effective surface than the plates (21) from which the plate pack (5) forming the preheating stage is formed. 8. Cross-flow plate heat exchanger according to one of the Claims 3 to 7, characterized in that one panel package is composed of edge strips (23) and panels (21) which are made of better quality material than the panels (21) and edge strips (23) of the other panel package. 9. Cross-flow plate heat exchanger according to claim 8, characterized in that the plate pack (6) forming the final heating stage is composed of edge strips (23) and plates (21) which are made of a material that is considerably more heat-resistant than the plates (21) and edge strips (23) of the plate pack (5) forming the preheating stage. PB 3283/1686 - 4 - &iacgr; 10, Cross-flow plate heat exchanger according to one of claims 3 to 9, characterized in that the beads (24) from the plates (21) and the edge strips (23) which are used in one plate package have a different height than those beads (24) on the plates (21) and the edge strips (2:3) which are used in the other plate package. 11. Cross-flow plate heat exchanger according to claim 10, characterized in that the beads (24) on the plates (21) and the edge strips (23) used in the plate pack (5) forming the preheating stage have a smaller height than those beads (24) on the plates (21) and the edge strips (23) used in the plate pack (6) forming the final heating stage. 12. Cross-flow plate heat exchanger according to claim 11, characterized in that the beads (24) in the plates (21) are generally embossed with the same embossing tool, but those beads (24) in plates (21) which have a lower height than the beads (24) on other plates (21) are realized in that these beads (24) are less pronounced, i.e. less high, by the embossing tool. 13. Cross-flow plate heat exchanger according to one or more of the preceding claims, characterized in that the two plate packs (5, 6) are composed of rectangular plates (21). 14. Cross-flow plate heat exchanger according to claim 13, characterized in that the long sides of the rectangular plates (21) have a length which corresponds to approximately 1.5 times the length of the wide sides of the rectangular plates (21). PB3283/1686-5- 15. Cross-flow plate heat exchanger according to one of claims 13 and 14, characterized in that < Strips (23) which form a heat-emitting medium flow channel (26) through which the heat-absorbing medium flows, extend along the broad sides of the plates (21), and that the strips (23) which delimit a flow channel (25) through which the heat-absorbing medium flows, extend along the long sides of the plates (21).
10 16. Cross-flow plate heat exchanger according to one or more of the preceding claims, characterized in that the strips (23) have such a length and width that, in order to ensure a favorable solder flow during soldering, they are designed to have a low Dimension, approximately 0.5 mm set back from the edge of the plates (21). 17. Cross-flow plate heat exchanger according to one or more of the preceding claims, characterized in that the beads (24) on the plates (21) are shaped in such a way that they enclose an angle of about 30° with the long sides, and that the plates (21) in the respective plate pack (5, 6) are arranged in such a way that the beads are in a Heat-emitting medium flows through a flow channel (26) at an angle of 60° to the flow direction of the heat-emitting medium and the beads in a flow _channel (25) flowed through by heat-absorbing medium at an angle of 30° to the flow direction of the heat-absorbing medium. 18. Cross-flow plate heat exchanger according to one or more of the preceding claims, characterized in that the inlet for the heat-absorbing medium at the plate pack (5) forming the preheating stage is on the same side as the outlet. PB3283/1686 - 6 - occurs for the heat-absorbing medium on the plate pack (6) forming the final heat stage. 19. Cross-flow plate heat exchanger according to claim 18, 5 characterized in that both plate packages (5 and 6) with their long sides parallel to each other. 20. Cross-flow plate heat exchanger according to claim 19, 1Ö characterized in that at least the front side (12) of the plate pack (5) forming the preheating stage, from which the medium to be preheated emerges after flowing through the latter, and that front side (13) of the plate pack (5) forming the final heating stage I 15 plate pack (6) into which the medium to be heated i subsequently enters, are arranged in one plane ₄ |. 21 . Cross-flow plate heat exchanger after one or more \ reren of claims 1 to 17, characterized I 20 net that the two plate packages (5 and 6) are offset from each other and arranged so that each jj Medium after leaving the in flow direction first h flowing plate pack (5 or 6) in the respective \ gen transfer channel (9 or 10) is diverted \- 25 and then the downstream plate package \ (5 or 6) in a direction that leads to fe previous flow direction at an angle of is less than 180°. 30 22. Cross-flow plate heat exchanger according to one or more of the preceding claims, characterized in that each of the two transfer channels (9, 10) consists of flat wall parts. 35 ■"jggas^jartässj^-SB^^jssa^^ a ■ PB3282/1686 - 7 - 23. Cross-flow plate heat exchanger according to one or several of the preceding claims, characterized in that both transfer channels (9, 1U)
are limited either by rigid walls or by walls that are movable within themselves or by wall sections that are at least partially rigid but movably connected to one another, ·· « &igr;&igr; &bull; « · i· I « I IMI t Ii ₁