EP1757887B1 - Heat exchanger block - Google Patents

Abstract

The heat exchange block has two plates (1a, 1b) with grooves (2a, 2b) bounded by ribs (3a, 3b) forming flow channels (2) for a gas. On the outer surfaces (4a, 4b) of the plates, there are cavities (5a, 5b) bounded by a hood (6a, 6b) for the cooling fluid. There are seals (7a, 7b) sealing the gaps between the plate surfaces and the hood edges.

Description

The present invention relates to a heat exchanger block.

In the Patent DE 508965 C For example, a heat exchanger block with fluids as heat exchanging media will be described. The design of the heat exchanger block with the same size channels for the heat-exchanging media can only expect overheating of the heat-absorbing medium, which leads to evaporation only outside the heat exchanger block in a relaxation space.

From the utility model DE 296 04 521 U1 is known a composed of plates made of graphite heat exchanger body. Within this heat exchanger body channel systems for two media are arranged.

The channels for the heat-releasing gaseous medium (hereinafter referred to as flue gas channels) are formed by recessed into the abutting surfaces of the plates grooves between which ribs remain. At least two such plates are combined so that the grooves in the abutting surfaces of both plates complement each other and thus form channels bounded by the abutting ribs of both plates.

The channels for the second, to be heated medium (hereinafter referred to as cooling medium) are formed as the plates penetrating holes. The thickness of the plates is chosen so that there is only a thin, the heat transfer little obstructing material barrier between the two channel systems, but their strength is sufficient to fluid-tightly separate the channel systems from each other and to ensure mechanical strength.

The outwardly facing surfaces of the panels are flat.

The plates are held together in a fluid-tight manner by adhesives or by means of seals and tension or tension anchors.

Several pairs of plates can be placed side by side and side by side. This modular design allows a targeted adaptation of the capacity of the heat exchanger for different requirements.

The channel systems can be arranged parallel or perpendicular to each other, depending on whether a media guide in the counter or DC or in the cross flow is intended. For the parallel guidance of the media, however, a significantly higher design and Processing effort needed to achieve the separation of the cooled and the current to be heated.

In parallel media guide the mouths of both channel systems are on the same end faces of the plates. That is to be provided on the relevant end faces respectively connection systems (headers) for two separate media streams.

In order to minimize the material barrier between the two channel systems, the bores extend between the grooves embedded in the plate surfaces, i. they lie on a plane near or above the bottoms of the grooves. The channel systems are, so to speak, interlocked. This leads to the fact that the mouths of the flue gas ducts and the mouths of the cooling channels at the end faces of the plates are very close to each other. Therefore, specially designed for the supply and distribution of the media to the respective channel system or for the collection of the partial streams from the channels and the Medienabtransport headers are necessary, which allow in a confined space a separate arrival or removal of various media.

As an alternative, in DE 296 04 521 proposed to close the holes at their front ends, for example, by glued-in plugs, and to provide tap holes from the plate surfaces to the holes forming the cooling channels, so that can be done from the plate surface and transport of the cooling medium. Although this variant solves the space problem at the end faces, but is even more expensive to manufacture, since the frontal orifices must be fluid-tightly sealed at each bore and additionally two tap holes must be attached.

Therefore, the cross-flow guidance is preferably used in practice, although more effective cooling can be achieved by means of counter-current guidance.

The flue gas channels are preferably designed so that on the one hand a high ratio of heat transfer surface (wall surface) is achieved to channel volume, on the other hand, the free flow cross section is sufficient to ensure the outflow of gases through natural convection. This is achieved by channels in the form of slots with a high ratio of depth to width. The production of the flue gas channels forming grooves is mainly by milling.

The channels for the cooling medium always have a circular cross-section, as they are drilled. However, the formation of these channels as holes is disadvantageous because of the high processing costs.

In addition, due to the drilling process down to circular channel cross-sections is unfavorable for the heat transfer. If the shape of the channels is fixed, the heat transfer coefficient alpha between the wall surface and the cooling medium, which in turn depends inter alia on the flow state of the cooling medium and on the geometric shape of the heat transfer surface, can be increased exclusively by increasing the flow velocity of the cooling medium in the bores.

This results in the object of the present invention, a heat exchanger block composed of plates in such a way that the leadership of the cooling medium does not occur through holes.

In addition, the heat exchanger according to the invention should enable a countercurrent flow of cooled gas flow and cooling medium without high design complexity.

The object is achieved in that, in the heat exchanger block according to the invention, the heat transfer to the cooling medium proceeds via the outwardly facing surfaces of the two plates comprising the flue gas channels. For this purpose, chambers through which a cooling medium flows are provided in the heat exchanger block according to the invention, which spaces directly adjoin the outwardly facing surfaces of the plates comprising the flue gas channels.

• zwei zusammenwirkende Platten 1a, 1b, deren aneinander grenzende Oberflächen mit Nuten 2a, 2b versehen sind, die von Rippen 3a, 3b begrenzt werden, wobei die Nuten 2a, 2b in den beiden Plattenoberflächen einander ergänzen und auf diese Weise Strömungskanäle 2 für ein gasförmiges Medium bilden, welche durch die aneinander stoßenden Rippen 3a, 3b beider Platten 1a, 1b begrenzt werden, wobei die Platten aus Graphit, einem keramischen Werkstoff oder einem Verbundwerkstoff aus einer Polymermatrix mit einem hohen Anteil darin verteilter wärmeleitfähiger Partikel bestehen,
• an die nach außen weisenden, als Wärmeübergangsflächen wirkenden Oberflächen 4a, 4b der Platten 1a, 1b anschließende, von einem Kühlmedium durchströmte Räume 5a, 5b, die jeweils von einer auf die Platte 1a bzw. 1b aufgesetzten Haube 6a bzw. 6b aus einem metallischen Werkstoff begrenzt werden
• umlaufende Dichtungen 7a, 7b zur Abdichtung der Spalten zwischen den Plattenoberflächen 4a, 4b und den Rändern der Hauben 6a, 6b
• Mittel zur Abdichtung des Spaltes zwischen den Platten 1a und 1b
• Mittel 8 zum Zusammenhalten des Blocks und
• Rauchgasanschlüssen (9, 9') besitzt, wobei jeder Rauchgasanschluss (9, 9) mittels Schrauben und einem Haltering (10, 10') an den beiden Hauben (6a, 6b) befestigt ist.

A heat exchanger block according to the invention ( FIG. 1 ) comprises:

• two cooperating plates 1a, 1b, whose adjacent surfaces are provided with grooves 2a, 2b bounded by ribs 3a, 3b, the grooves 2a, 2b in the two plate surfaces complementing each other and thus flow channels 2 for a gaseous medium form, which are bounded by the abutting ribs 3a, 3b of both plates 1a, 1b, wherein the plates of graphite, a ceramic material or a composite material of a polymer matrix with a high proportion of heat-conductive particles distributed therein,
• to the outwardly facing, acting as heat transfer surfaces surfaces 4a, 4b of the plates 1a, 1b, followed by a cooling medium spaces 5a, 5b, each of a mounted on the plate 1a and 1b hood 6a and 6b of a metallic material be limited
• circumferential seals 7a, 7b for sealing the gaps between the plate surfaces 4a, 4b and the edges of the hoods 6a, 6b
• Means for sealing the gap between the plates 1a and 1b
• Means 8 for holding the block and
• Flue gas connections (9, 9 ') has, each flue gas connection (9, 9) by means of screws and a retaining ring (10, 10') to the two hoods (6a, 6b) is attached.

Further advantages, details and variants of the invention can be taken from the figures and the following detailed description.

Figur 1

schematischer Aufbau eines erfindungsgemäßen Wärnnetauscherblocks

Figur 2

erfindungsgemäßer Wärmetauscherblock mit Rauchgasanschlüssen

Figur 3

perspektivische Ansicht einer vorteilhaften Ausgestaltung des erfindungs- gemäßen Wärmetauscherblocks

Figur 4

Querschnitt einer weiteren vorteilhaften Ausgestaltung des erfindungs- gemäßen Wärmetauscherblocks

Figur 5

Wärmetauscherblock gemäß dem Stand der Technik (Vergleichsbeispiel)

The figures show:

FIG. 1

schematic structure of a heat exchanger block according to the invention

FIG. 2

inventive heat exchanger block with flue gas connections

FIG. 3

perspective view of an advantageous embodiment of the inventive heat exchanger block

FIG. 4

Cross section of a further advantageous embodiment of the inventive heat exchanger block

FIG. 5

Heat exchanger block according to the prior art (comparative example)

In the FIGS. 1 to 5 the heat exchanger block according to the invention for the sake of simplicity is always lying, that is, the flue gas channels 2 extend in the horizontal direction. However, this is not intended to mean a specific type of installation or installation, the heat exchanger block according to the invention can of course also in a standing position (flue gas ducts 2 extend vertically) are operated. The specialist decides on the type of installation based on the particular application.

The plates 1a, 1b, which surround the flue gas channels 2, as can DE 296 04 521 U1 made of synthetic graphite whose pores have been sealed by impregnation, or from a composite material made of a polymer matrix with a high proportion of distributed therein conductive particles, such as particles of graphite or silicon carbide.
However, the present invention is not bound to these materials. The plates 1a, 1b could in principle also be made of metallic materials. When choosing the material for the plates 1a, 1b, temperature and corrosivity of the gaseous medium to be cooled must be taken into account.

With regard to the design of the flue gas ducts 2, the already in DE 296 04 521 U1 considerations set out above. In order to obtain a channel cross-section which is both favorable in terms of flow and also provides a large heat transfer surface, grooves 2a, 2b are preferred with a depth which is great in relation to their width. The ratio of groove width to groove depth can be up to about 1:50, with a ratio of about 1: 1 to 1:10 being particularly favorable for production and procedural considerations for graphite apparatuses. When combining the plates 1a, 1b, the narrow deep grooves 2a, 2b complement each other to slot-shaped channels 2.
The thickness of the plates 1a, 1b is designed so that the distance between the bottoms of the flue gas channels 2 forming grooves 2a, 2b and as the heat transfer surfaces 4a, 4b acting surfaces of the plates 1a, 1b is as small as possible, but a sufficient to ensure the mechanical stability and fluid tightness material layer stops. For graphite materials, the minimum layer thickness required for stability is approximately 10 to 15 mm.

The ribs 3a, 3b are used in addition to the limitation of the flue gas ducts 2 and the support of the plates 1a, 1b, which are loaded by the adjacent flowed through by the cooling medium spaces 5a, 5b and these spaces final caps 6a, 6b.

Suitable materials for the hoods 6a, 6b are metallic materials, such as cast iron. The hoods 6a, 6b, which close off the spaces 5a, 5b through which a cooling medium flows, do not come into contact with the hot and corrosive flue gas. Therefore, the materials for the hoods 6a, 6b do not have to be so demanding in terms of corrosion resistance. Thus, in the heat exchanger block according to the invention, the use of corrosion-resistant but expensive and difficult-to-machine materials such as graphite or ceramic can be limited to those areas in which such materials are absolutely necessary because of contact with hot corrosive media.

The delimitation of the space flowed through by the cooling medium 5a, 5b by hoods 6a, 6b also allows almost any design of the flow guidance of the cooling medium.

The edges of the hoods 6a, 6b are sealed with circumferential flat or O-ring seals 7a, 7b against the plate surfaces 4a, 4b.

The flexible seals 7a, 7b compensate for the differences in thermal expansion between the plates 1a, 1b through which the hot flue gas flows and the relatively cold hoods 6a, 6b.

Also, the gap between the plates 1a, 1b must be sealed.

This can be done by an adhesive, for example, consisting of graphite plates 1a, 1b could be cemented together. However, such a permanent connection of the flue gas channels 2 enclosing plates 1a, 1b by an adhesive has the disadvantage that the plates 1a, 1b can then no longer be detached from each other without destroying each other.

Therefore, it is preferable to hold together the block comprising the hoods 6a, 6b and the plates 1a, 1b by means of releasable tensioning devices 8, for example tension anchors, whereby the gap between the plates 1a, 1b is sealed by means of a soft seal. This structure allows a complete disassembly including the separation of the plates 1a and 1b from each other. This facilitates maintenance work such as the cleaning of the flue gas ducts.

The supply and discharge of the gaseous medium into and out of the flue gas ducts 2 via connection hoods 9, 9 '. FIG. 2 shows a heat exchanger block according to the invention with the attached connection hoods 9, 9 'for the inlet and outlet of a gaseous medium, eg flue gas from an incinerator. The construction of such connection hoods is known and will therefore not be described in detail. It should only be mentioned that the hood 9 'is optionally provided with a Kondensatabflussvorrichtung for the exit of the cooled gaseous medium, when the gaseous medium to be cooled contains condensable constituents.

From the prior art it is known to clamp the gas connection hoods 9, 9 'with tie rods which extend over the outer sides of the heat exchanger block. However, this has the disadvantage that the flue gas connection hoods can not be removed separately because of the common tension by the tie rods.

The structure of the heat exchanger according to the invention opens up the possibility of releasably securing the flue gas connections 9, 9 'independently of each other on the hoods 6a and 6b by means of screws and one retaining ring 10, 10'. Thus, assembly and maintenance of the flue gas connections 9, 9 'independently possible.

For the supply of the cooling medium in the flow spaces 5a, 5b ports 12a, 12b and for the removal of the heated cooling medium connections 12a ', 12b' on the hoods 6a, 6b are provided.

To increase the heat transfer surface, a plurality of inventive heat exchanger blocks can be arranged next to or in succession.

Due to the simplified shape of the plates 1a, 1b, which in contrast to the prior art have no holes, such manufacturing techniques can be used for their production, which do not work material removal. Especially advantageous are techniques such as compression molding, extrusion, and the like, as the processing effort and the material losses associated with a machining are avoided.

In an advantageous development of the heat exchanger block according to the invention ( FIG. 3 ), the surfaces 4 a, 4 b of the plates 1 a, 1 b acting as heat transfer surfaces are provided with profile structures 11 which increase the area available for the heat transfer and / or increase the turbulence of the flow of the cooling medium. Such structures 11 may, for example, grooves, beads, ribs, webs, protrusions, eg knobs or the like. Contain structural elements or combinations thereof. Advantageously, for example, mutually offset ribs or ribs with mutually offset openings, because thereby the turbulence of the cooling medium is increased. Particularly advantageous are such profile structures, as used in plate heat exchangers (plate heat exchangers) and for example from the patent EP 0 203 213 are known.

When the space 5a, 5b through which the cooling medium flows, as in FIG FIG. 3 shown, in the surface 4a, 4b of the plate 1a, 1b is inserted, the hood 6a, 6b can be performed as a flat plate, which rests on the provided with a circumferential seal 7a, 7b raised edge of the structured plate surface 4a, 4b and through the out of the plate surface 4a, 4b protruding structural elements 11 is supported.

However, such a support by the structural elements is not absolutely necessary, as well as a small gap between structural elements 11 hoods 6a and 6b can be procedurally tolerated, and does not affect the function.

Alternatively or additionally, the inner sides of the hoods 6a, 6b, which in each case close the space 5a, 5b through which a cooling medium flows, may be provided with profile structures 11 'suitable for generating turbulence ( FIG. 4 ).

The variant off FIG. 4 with structured inner sides of the hoods 6a, 6b is opposite to the variant FIG. 3 with structured heat transfer surfaces 4a, 4b of the plates 1a, 1b, because the hoods 6a, 6b are made of metallic materials which are easier to machine than graphite or ceramic materials.

The structures 11 and 11 'are also adapted to guide the flow of the cooling medium purposefully, almost regardless of the placement and type of connections 12a', 12b 'for the supply and 12a', 12b 'the discharge of the cooling medium. The problem known from the state of the art that, in the case of a parallel media guide, connections for two different media streams to be kept separate from one another must be accommodated in the narrowest space on the same front or side surfaces of the block, is thus avoided in the heat exchanger block according to the invention.

Thus, by appropriate structuring of the heat transfer surfaces 4a, 4b and / or the insides of the hoods 6a, 6b in the heat exchanger according to the invention achieve a pure countercurrent flow of flue gas and coolant, which is particularly effective for heat transfer.

Embodiment:

Three heat exchangers have been designed which must perform the same cooling task.

The first heat exchanger has according to the DE 296 04 521 U1 known prior art cooling channels, which are formed by holes 13 in the plates 1a, 1b ( FIG. 5 ).

In the second, inventive heat exchanger, the transfer of the heat emitted by the flue gases heat to the cooling medium via the flat outer surfaces 4a, 4b of the plates 1a, 1b, which are covered by the cooling medium ( FIG. 1 ).

In the third heat exchanger according to a further development of the present invention, the outwardly facing surfaces 4a, 4b of the plates 1a, 1b are provided with such a flow structure 11 as the plates of a plate heat exchanger ( FIG. 3 ).

The flow rate of the cooling medium in the bores of the first heat exchanger is assumed to be a constant size for all three heat exchangers, i. The cooling medium flows through the heat transfer surfaces of all three heat exchangers at the same speed.

The heat transfer coefficient alpha is 50% higher in the heat exchanger according to the invention with a flat heat transfer surface overflowed by the cooling medium compared with the bores through which the cooling medium flows according to the prior art. In which heat exchanger according to the invention with a structured heat transfer surface is the increase of the heat transfer coefficient alpha compared to the prior art even 3.5 times.

The improvement of the heat transfer to the cooling water made possible by the design according to the invention of the heat exchanger is particularly advantageous if the gas-side heat transfer coefficient is also high. This is the case when the gas to be cooled contains condensable fractions.

Because the heat transfer coefficient alpha on the heat transfer coefficient k, in addition to the heat transfer surface and the temperature difference determines the transmittable heat output, the heat transfer surface can be reduced in the inventive design of the heat exchanger thanks to the increased heat transfer coefficient at the same cooling capacity. Thus, with otherwise identical boundary conditions, the heat exchanger can be made more compact than, for example, with the in DE 296 04 521 U1 described prior art is possible.

Claims (7)

1. Heat exchanger block, comprising

   • two plates (1a, 1b), the mutually continuous surfaces of which are provided with grooves (2a, 2b) which are delimited by ribs (3a, 3b), the grooves (2a, 2b) in the two plate surfaces completing one another and thereby forming flow ducts (2) for a gaseous medium which are delimited by the mutually abutting ribs (3a, 3b) of the two plates (1a, 1b), the plates consisting of graphite, a ceramic material or a composite material composed of a polymer matrix with a high fraction of heat-conductive particles distributed therein,

   • spaces (5a, 5b) which are adjacent to the outwardly pointing surfaces (4a, 4b), acting as heat transfer surfaces, of the horizontal plates (1a, 1b) and through which a cooling medium flows and which are delimited in each case by a cowl (6a, 6b) placed onto the plate (1a, 1b) and composed of a metallic material,

   • peripheral seals (7a, 7b) for sealing off the gaps between the plate surfaces (4a, 4b) and the margins of the cowls (6a, 6b),

   • means for sealing off the gap between the plates (1a, 1b),

   • means (8) for holding the block together, and

   • flue gas connections (9, 9'), each flue gas connection (9, 9') being fastened to the two cowls (6a, 6b) by means of screws and a holding ring (10, 10').
2. Heat exchanger block according to Claim 1, characterized in that the gaps between the plate surfaces (4a, 4b) and the margins of the cowls (6a, 6b) are sealed off by means of O-ring seals (7a, 7b).
3. Heat exchanger block according to Claim 1, characterized in that the block is held together by means of releasable tension devices (8), the gap between the plates (1a, 1b) being sealed off by means of a soft seal.
4. Heat exchanger block according to Claim 1, characterized in that the plate surfaces (4a, 4b) and/or the insides of the cowls (6a, 6b) are provided with profile structures (11, 11').
5. Heat exchanger block according to Claim 4, characterized in that the profile structures (11, 11') contain at least one of the following structure elements: flutes, beads, ribs, webs, projections, knobs.
6. Heat exchanger block according to Claim 4, characterized in that the profile structures (11, 11') contain ribs offset with respect to one another or ribs with perforations arranged so as to be offset with respect to one another.
7. Heat exchanger block according to Claim 1, characterized in that the cooling medium is routed in the spaces (5a, 5b) in countercurrent to the medium to be cooled in the flue gas ducts (2).

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