HEAT EXCHANGING ELEMENT FOR A HEAT EXCHANGER, METHOD OF MANUFACTURING A HEAT EXCHANGING ELEMENT FOR A HEAT EXCHANGER, HEAT EXCHANGER, AND RETROFITTING METHOD FOR A HEAT EXCHANGER

Abstract

A heat exchanging element for a heat exchanger is provided with a coating that prevents, or at least reduces, the amount of contaminating materials to be abrade from the heat exchanger and into the heat exchange media. A method for producing a heat exchanging element for a heat exchanger, a heat exchanger per se, and a method for retrofitting an existing heat exchanger, provide for the occurrence of impurities caused by abrasion in one or more heat exchanging media and/or corrosion to be prevented or at least reduced by providing the coating.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation, under 35 U.S.C. §120, of copending international application No. PCT/EP2011/059649, filed Jun. 10, 2011, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2010 030 780.7, filed Jun. 30, 2010; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a heat exchanging element for a heat exchanger, a method for manufacturing a heat exchanging element for a heat exchanger, a heat exchanger per se, specifically involving the use of the heat exchanging element according to the invention, as well as a retrofitting method for a heat exchanger. In particular, the present invention also relates to CVD-coated and impregnated graphite, which is used especially for a heat exchanging element or recuperator element, in particular in a core for a block heat exchanger.

In many areas of chemical and/or physical process engineering, quantities of heat must be exchanged between at least two fluid media, whether it be liquids, gases, gels, pasty media or the like, for example in order to cool or heat a provided process medium. The heat exchangers or recuperators used here exhibit at least one heat exchanging element or recuperating element, the corresponding contact surfaces or contact areas of which receive the flow of actual process medium to be heated or cooled, and of at least one additional medium, which supplies or removes the quantity of heat, and is often referred to as the service medium. The quantity of heat is introduced in one of the contact areas or in one of the contact surfaces, transferred by way of a heat conducting mechanism of the heat exchanging element to another contact surface or another contact area, and then released by the latter to the other medium.

In this context, use is often made of heat exchanging elements that consist essentially of a graphite material, which is impregnated with a resin material at the contact surface that comes into contact with a respective medium, for example to limit or even prevent the penetration of respective medium into the porous complex of the material that forms the basis of the heat exchanging element.

During the inflow of the receptive medium, in particular the process medium, particles from the resin impregnation and/or the material comprising the basis of the heat exchanging element, e.g., the graphite material, frequently become physically and/or chemically detached, remain in the actual process medium and thereby contaminate the latter. This is often unacceptable.

In addition, corrosion on the material of the heat exchanging element and/or a detachment of corroded material and contamination of the heat exchanging fluid(s) by corroded material of the heat exchanging element can in many instances not be tolerated.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a heat exchanging element for a heat exchanger, a manufacturing method for a heat exchanging element for a heat exchanger, a heat exchanger per se as well as a retrofitting method for a heat exchanger, which overcome the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which render it possible to easily and yet reliably reduce or even prevent contamination of the heat exchanging medium/media by material from the underlying heat exchanging element and corrosion to the material of the heat exchanging element(s) and contamination of the heat exchanging fluid(s) by corroded material.

With the foregoing and other objects in view there is provided, in accordance with the invention, a heat exchanging element for a heat exchanger, the heat exchanging element comprising:

a body containing or essentially consisting of one or more materials selected from the group consisting of graphitic materials, graphites, and open-pored, unsintered silicon carbide materials;

said body being formed with a first contact region and a second contact region for separate contact in terms of flow with a first heat exchanging medium forming a first process medium and with a second heat exchanging medium forming a second process medium, respectively, for effecting separate heat exchange; and

a coating with one or more materials selected from the group of materials consisting of silicon carbide materials, carbide oxide materials, silicide materials, tungsten titanate materials, oxide materials, pyrocarbon, diamond, and derivatives and combinations thereof;

said coating being disposed on at least one of said first and second contact regions and partially or completely coating the respective said contact region.

The objects underlying the invention are achieved according to the invention by way of the claimed heat exchanging element, by way of the claimed method for manufacturing a heat exchanging element, by of the claimed heat exchanger, and the claimed method of retrofitting a heat exchanger.

A first aspect of the present invention provides a novel heat exchanging element for a heat exchanger, which, in order to achieve a separate heat exchange in terms of flow between a first heat exchanging medium as the process medium and a second heat exchanging medium as the service medium, exhibits a first contact region and a second contact region for a separate contact in terms of flow with the first heat exchanging medium or the second heat exchanging medium, which essentially contains or consists of one or more materials from the group of materials that exhibits graphite materials, graphites and open-pored and unsintered SiC or silicon carbide materials, and in which at least one of the first and second contact regions is partially or completely coated with one or more materials from the group of materials as the coating, which exhibits SiC or silicon carbide materials, carbide oxide materials, silicide materials, tungsten titanate materials and their derivatives and combinations. The first and second heat exchanging media can here be fluids, e.g., liquids, gases, gels or pasty media, foams, slurries and their combinations and mixtures.

Therefore, one core idea of the present invention involves reducing or preventing the likelihood that material comprising the basis of the heat exchanging element will detach and/or corrode, by giving the material comprising the basis of the heat exchanging element an especially resistant or abrasion-proof coating, at least on one of the first and second contact regions or contact surfaces of the heat exchanging element, precisely when the material comprising the basis of the heat exchanging element is made out of a graphite material or an open-pored and/or unsintered SiC or silicon carbide material.

An impregnation can be composed of an impregnating material containing or consisting of one or more materials from the group exhibiting resin materials, phenol resin materials and their derivatives and combinations. In particular, impregnation with the impregnating material serves to prevent one of the heat exchanging media from advancing too deeply and in particular penetrating the material comprising the basis of the heat exchanging element, and remaining therein, so as to thereby reduce or prevent a material intermixing, even if this were only possible in the long term, and/or a contamination when exchanging media.

The impregnation with the impregnating material can be formed entirely or partially on and/or in the coating and/or entirely or partially on and/or in the first contact region and second contact region. Since the coating at least partially, if not completely, seals the material comprising the basis of the heat exchanging element anyway so as to prevent contamination, e.g., through abrasion or the like, i.e., closes pores at that location, it is especially advantageous for an impregnation to have been or be formed on or in the coating to prevent contamination. This also offers procedural advantages, since thermal boundary conditions for the impregnating material need not be taken into account when processing the coating on the material comprising the basis of the heat exchanging element. For example, high-temperature stages can be run through in the manufacturing process, without having to expect that the impregnating material will become damaged or degraded, since the latter can then be applied or introduced after the fact, i.e., following the high-temperature stage.

The coating with the coating material can conceivably have varying structures and methods involved in its manufacture.

The coating may be configured as a CVD coating (CVD, chemical vapor deposition).

Alternatively or additionally, the coating can be configured as a chemical and/or physical conversion area—in particular via a process involving the entire or partial chemical and/or physical conversion of the material comprising the first and/or second contact region.

Further, the coating can alternatively or additionally be formed by method of plasma spraying and/or flame spraying. In addition, successful tests have already been performed on the formation of a solid layer through so-called liquid silicidation, both in an immersion process and evaporation process, as well as in a wicking process.

Depending on the kind of material provided for coating purposes or the materials provided for coating purposes, use can be made of different coating mechanisms and corresponding manufacturing methods, but the coating formed as a chemical and/or physical conversion layer is especially elegant in particular when no or only a slight quantity of additional material components must be provided for coating purposes.

Different manufacturing methods and structures can have been or be combined with each other while building up the coating.

The heat exchanging element according to the invention can be designed as a heat exchanger plate or recuperator plate of a plate heat exchanger or plate recuperator.

The heat exchanging element according to the invention can also be designed as a heat exchanger core or block or as a recuperator core or block of a block heat exchanger or block recuperator.

Further, the heat exchanging element according to the invention can be designed as a heat exchanger tube or recuperator tube of a tubular heat exchanger or tubular recuperator.

Therefore, the concept according to the invention can basically be utilized in all heat exchangers or recuperators in which one or more heat exchanger elements or recuperator elements are used that follow the principle outlined in greater detail above, specifically that it receives a flow of heat exchanging medium, in particular a process medium, at least on one contact region or on one contact surface, thereby coming into mechanical contact with the latter, as a result of which the physical and/or chemical interaction conceivably leads to an abrasion on a surface of the contact area or the contact surface of the heat exchanging element.

Another aspect of the present invention provides a method for manufacturing a heat exchanging element for a heat exchanger, in which the heat exchanging element for a separate heat exchange in terms of flow between a first heat exchanging medium as the process medium and a second heat exchanging medium as the service medium is designed with a first contact region and with a second contact region for separately contacting the first heat exchanging medium or second heat exchanging medium in terms of flow, in which the heat exchanging element essentially contains or consists of one or more materials from the group of materials that exhibits graphite materials, graphites and open-pored and unsintered SiC or silicon carbide materials, and in which at least one of the first and second contact regions is entirely or partially coated with one or more materials from the group of materials as the coating, which exhibits SiC or silicon carbide materials, pyrocarbon, oxide ceramics, e.g., chromium oxides, diamond, carbide oxide materials, silicide materials, tungsten titanate materials and their derivatives and combinations.

An impregnation can be composed of an impregnating material containing or consisting of one or several materials from the group exhibiting resin materials, phenol resin materials and their derivatives and combinations.

The impregnation with the impregnating material can be formed entirely or partially on and/or in the coating and/or entirely or partially on and/or in the first contact region and second contact region.

The coating may be configured as a CVD coating (CVD, chemical vapor deposition).

The coating may also be configured as a CVI coating (CVI, chemical vapor infiltration).

Alternatively or additionally, the coating can be designed as a chemical and/or physical conversion area—in particular via a process involving the entire or partial chemical and/or physical conversion of the material comprising the first and/or second contact region.

Further, the coating can alternatively or additionally be formed by method of plasma spraying and/or flame spraying.

The heat exchanging element can be designed as a heat exchanger plate or recuperator plate of a plate heat exchanger or plate recuperator.

The heat exchanging element can also be designed as a heat exchanging core or block or as a recuperator core or block of a block heat exchanger or block recuperator.

The heat exchanging element according to the invention can also be designed as a heat exchanger tube or recuperator tube of a tubular heat exchanger or tubular recuperator.

Another aspect of the present invention also provides a heat exchanger, in which one or more heat exchanging elements according to the invention have been or will be formed.

In addition, another aspect of the present invention also indicates a method for retrofitting an already existing heat exchanger, in which one or more present and in particular conventional heat exchanging elements are replaced by one or more corresponding heat exchanging elements according to the invention and/or in which one or more present and in particular conventional heat exchanging elements are converted into heat exchanging elements according to the invention, wherein in particular the method according to the invention is used.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a heat exchanging element for a heat exchanger, a method for manufacturing a heat exchanging element for a heat exchanger, a heat exchanger, and a retrofitting method for a heat exchanger, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic and perspective exploded view of an embodiment of a heat exchanger according to the invention taking the form of a plate recuperator using an embodiment of the heat exchanging element according to the invention in the form of a recuperator plate.

FIG. 2 is a schematic and perspective side view of a single heat exchanging element from the assembly on FIG. 1.

FIGS. 3A and 3B show schematic sectional side views of two intermediate states attained in a manufacturing process according to the invention for a heat exchanging element according to the invention.

FIG. 4 is a schematic and perspective side view of another embodiment of a heat exchanger, specifically taking the form of a block recuperator.

FIGS. 5A and 5B show schematic sectional side views of two intermediate states that are attained in another embodiment of a manufacturing process according to the invention for a heat exchanging element according to the invention.

FIGS. 6A and 6B show schematic sectional side views of two intermediate states that are attained in another embodiment of a manufacturing process according to the invention for a heat exchanging element according to the invention.

FIGS. 7A and 7B show schematic sectional top views of two intermediate states that are attained in another embodiment of a manufacturing method according to the invention for a heat exchanging element according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A variety of embodiments and implementations of the present invention will be described below. It will be understood that the various embodiments of the invention along with their technical features and properties can be individually isolated or optionally combined with each other in any way desired and without limitation.

Structurally and/or functionally identical, similar or equivalent features or elements will be identified with common reference numerals throughout the figures. A detailed description of these features or elements will not be repeated in each instance.

Referring now to the figures of the drawing in general, the present invention relates to a heat exchanging element 10, 20 for a heat exchanger 100, 200, a method for manufacturing a heat exchanging element 10, 20 for a heat exchanger 100, 200, a heat exchanger 100, 200 per se, as well as a method for retrofitting an existing heat exchanger, in which contaminants generated via abrasion and/or corrosion in one or more heat exchanging media M1, M2 and/or corrosion have been or will be prevented or at least reduced by providing a coating 30.

In addition to the general principle described above, the present invention also relates to CVD-coated and impregnated graphite, and in particular to its use for configuring heat exchanging or recuperator elements 10, 20.

In particular in the fine chemical and pharmaceutical industry, heat exchangers 100, 200 and recuperators 100, 200 made out of graphite impregnated with synthetic resin are frequently used for cooling or heating media M1, M2. In the context, it happens that graphite particles or particles stemming from impregnation, i.e., resin particles, are detached and/or corroded from the surfaces 20v or walls 20v of the product boreholes 22 by the process medium M1 flowing through the heat exchanger 100, 200. The latter may, in particular, take the form of a block recuperator 200. These particles must be understood as foreign particles, because they contaminate the end product, so that the entire production lot must be discarded in the worst-case scenario.

In order to avoid or circumvent this problem, for example, consideration can be given to using recuperators 100, 200, whose heat exchanging elements 10, or recuperator elements 10, 20 are made completely out of silicon carbide (SiC). The advantage to silicon carbide by comparison to recuperator elements or heat exchanging elements consisting of graphite is that the abrasion and/or corrosion resistance is clearly higher, so that practically no silicon carbide particles are encountered in the heat exchanging medium M1, M2, in particular in the product medium M1 or product solution M1.

The disadvantage to a heat exchanging element or recuperator element made completely out of silicon carbide is that the material and manufacturing costs are several times higher by comparison to pure graphite, so that this option can as a rule be used only in exceptional cases. In addition, the extremely brittle behavior of SiC ceramics is often disadvantageous owing to the application.

The present invention also makes use of the understanding that in particular graphite surfaces can be coated with silicon carbide or SiC in a CVD process, especially one carried out at temperatures exceeding 1000° C., so as to thereby raise the abrasion and/or corrosion resistance of the material 10′, 20′ comprising the basis of a heat exchanging element 10, 20, meaning in particular of the underlying graphite material. This also holds true for substrates, e.g., CSiC material. The diminished corrosion resistance of the free carbon is problematical in this context, and poses an obstacle to an application of the kind described above.

The advantage here is that the use of silicon carbide, for example, as the coating material 30′ yields a higher abrasion resistance on the one hand, while not inordinately increasing the manufacturing costs on the other, since the underlying material 10′, 20′ can still continue to be a low-cost material, in particular a graphite material, which then is quasi refined on its surface via the coating 30.

In particular in the case of so-called block recuperators 200, it might also be possible for the recuperator block 20, especially in terms of the product boreholes 22, to have situated upstream from it a block element made completely out of an abrasion-resistant material, e.g., silicon carbide, but containing no service boreholes 24 for the second heat exchanging medium M2. This ensures that an abrasion-resistant component will handle first contact with the process medium M1.

While this makes it possible to lower the extent of contamination, providing such a preliminary block made completely out of abrasion-resistant material in this way is also cost-intensive, and associated with the technical drawback that a dead volume is introduced prior to the actual recuperator process, thereby diminishing the overall effectiveness of such an installation.

By contrast, the invention proposes a simplified approach, namely coating one or more heat exchanging elements 10, 20 of a heat exchanger 100, 200 with an abrasion and/or corrosion-resistant material 30′, specifically at least in the areas or partial areas where contact takes place with the process medium M1.

As a result, the invention creates a variant that is cost-effective and potentially mechanically more tolerant to brittle fractures by comparison to recuperator elements 10, 20, e.g., block recuperators, which are made completely out of an abrasion and/or corrosion-resistant material. Therefore, a cost-effective and previously conventional material 10′, 20′ can be used for the heat exchanging elements 10, 20, in which all surfaces that come into contact with the abrasive and/or corrosive medium M1, M2, e.g., the two end surfaces 20e and the product boreholes 22 in the block recuperator 200, are then protected by a layer 30 of abrasion and/or corrosion-resistant material 30′, e.g., silicon carbide, and their pores are then completely impregnated with a synthetic resin 40′, so as to ensure the tightness of the heat exchanging element 10, 20, in particular of the recuperator block 20.

An impregnation 40 based on synthetic resin 40′ or some other type of impregnation 40 is often necessary, since it can frequently not be ensured that each surface of the heat exchanging element 10, 20, in particular of the block recuperator 200, coming into contact with the process medium M1 is completely sealed by the used abrasion and/or corrosion-resistant material 30′, in particular by the silicon carbide.

An impregnation 40, in particular with synthetic resin 40′, must take place after the process of coating with the abrasion and/or corrosion-resistant material, since temperatures in excess of 1000° C. during the coating process can destroy the material 40′ for the impregnation 40.

An embodiment of a manufacturing method according to the invention for a heat exchanging element 10, 20, in particular for a recuperator block 200 or the like, can have the following structure:

A finished block 20, e.g., consisting of graphite 20′ or the like, is coated with a silicon carbide coating 30 based on a CVD process, wherein, for example, the lateral surfaces 20m of the block can be covered with a graphite film, for example, so that no coating takes place there.

Alternatively, the service boreholes 24 can be introduced into the block 20 after coating with the silicon carbide material 30′ is complete.

The block 20 coated with silicon carbide 30′ is then given an impregnation 40 analogously to the manufacture of recuperator blocks, e.g., impregnated with a synthetic resin 40′. Prior to impregnation 40, the two end surfaces 20e of the block 20 can be covered with two correspondingly large metal disks, wherein a seal between each block end face 20e and the metal disk prevents contact between the impregnating resin 40′ and the block end surfaces 20e and product boreholes 22. The resin 40′ for impregnation 40 can penetrate into the block 20 via the lateral surfaces 20m and the service boreholes 24. For example, the jacket disks are fixed in place and made taut by several tension rods, which are guided through the product boreholes 22. After impregnation 40, the block 20 with the braced metal plates is placed in an annealing oven. The synthetic resin 40′ is hardened in a standard procedure. Obtained as the end product is a block 20 coated with silicon carbide on the product side, and free of resin film in the product boreholes 22.

These and similar types of manufacturing methods according to the invention and heat exchanging elements 10, 20 according to the invention have a variety of advantages relative to prior art procedures:

The heat exchanger 100, 200 or recuperator 100, 200, in particular block recuperator 200, manufactured according to the invention is resistant to abrasive and/or corrosive media, and just like a conventional heat exchanger, facilitates a complete heat exchange between a process medium M1 and service medium M2, i.e., without the formation of dead volumes.

In addition, the abrasion-resistant layer 30 or coating 30, in particular the SiC layer, prevents both the adsorption of media M1, M2 and their subsequent desorption when changing out a product or the service medium M2. In addition, the abrasion and/or corrosion-resistant layer 30 or the SiC layer 30 can prevent any graphite particles or resin particles from abrading or accumulating in the process medium M1, and hence in the product solution, and/or corrosion.

The substrate material 10′, 20′—e.g., the graphite 10′, 20′—and coating material 30′ can advantageously be coordinated in terms of their thermal expansion coefficients.

This is because, in another aspect of the present invention, the ratio between the thermal expansion coefficients for the substrate material 10′, 20′, in particular the graphite substrate 10′, 20′, and the coating material 30′ and/or impregnating material 40′—in particular the CVD-SiC—can be selected and set in such a way, for example, as to exhibit values which, if at all possible, range between about 1.2 and about 0.8, preferably between about 1.1 and about 0.9, and especially preferably between about 1.05 and 0.95, in particular at the highest process temperature. Ideally, the thermal expansion coefficients of the material pairings are identical.

It has surprisingly been discovered that layer thicknesses of below 5 μm are already abrasion and corrosion-proof. Particles are successfully retained, substrate corrosion is prevented, and an extreme increase is achieved in surface hardness. Therefore, layer thicknesses of between 5 and 1000 μm, preferably of between 20 and 400 μm, and especially preferably of between 50 and 200 μm are ideally applied.

Preferred process temperatures here range in particular between about 1200° C. and 2400° C., depending on the used coating process, in particular the CVD procedure.

Amazingly, absolutely tear-free coatings can be obtained by carefully selecting material pairings in this way in terms of their thermal expansion, thereby potentially eliminating the need for a seal, for instance with resins.

Aside from a high wear resistance, surfaces fabricated in this way exhibit a high corrosion resistance, which in particular matches that of a SiC, alpha-SiC or a-SiC.

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a schematic and perspective exploded view of an embodiment for a heat exchanger 100 according to the invention in the form of a so-called plate heat exchanger 100′ or plate recuperator 100′. The latter is formed of an assembly 110 resembling a stack comprised of a plurality of heat exchanger elements 10 or recuperator elements 10 configured as heat exchanger plates 10 or recuperator plates 10.

The arrows denote the inflows and outflows of the first and second heat exchanging media M1 and M2, which alternately flow in the gaps R1, . . . , Rn as flow spaces, wherein corresponding sealing devices are provided between the sequential heat exchanger elements 10 (not explicitly shown here), so as to prevent the first and second heat exchanging media M1 and M2 from mixing together.

FIG. 2 presents a schematic and perspective side view of a single heat exchanging element 10 in the form of a heat exchanger plate 10 from the arrangement on FIG. 1. This heat exchanging element 10 in the form of plates essentially consists of a base material 10′, e.g., a graphite material, and exhibits an upper side 10o or front side 10o and a rear side 10u or lower side 10u. The front side 10o and rear side 10u can be made out of corresponding flow channels in the surface of the underlying material 10′ of the plate 10, so as to intensify the mechanical contact, and hence exchange of heat, between the two sides 10o and 10u of the plate 10. These flow or streaming channels are not explicitly shown here, and form a kind of relief on the upper side 10o or lower side 10u of the plate 10.

FIGS. 3A and 3B present various manufacturing stages for the heat exchanging element 10 depicted on FIG. 2 in plate form.

FIG. 3A practically denotes the blank for the heat exchanging element 10 in plate form. This means that the plate 10 essentially consists of a conventional material 10′, e.g., a graphite material, as the plate substrate 10′. Also denoted are the upper side 10o and lower side 10u of the plate 10.

In the transition to the depiction on FIG. 3B, a coating 30 consisting of an abrasion-resistant material 30′ is formed at least on the upper side 10o and lower side 10u.

It is often sufficient for the respective side—i.e., either the upper side 10o or the lower side 10u—with the abrasion-resistant material 30′ to be designed as the coating 30 that comes into contact with the actual process medium, e.g., the heat exchanging medium M1, which as the product must not be contaminated. Whether the service medium, meaning the second heat exchanging medium M2, for example, becomes contaminated or not is frequently of secondary importance. Therefore, the side—the lower side 10u on FIGS. 3A and 3B—must often only be provided with the coating 30 as an option, as denoted on FIG. 3B with a dashed line.

FIG. 4 presents a schematic and perspective side view of another embodiment of a heat exchanger 200 or recuperator 200 according to the invention, specifically in the form of a perfectly cylindrical block recuperator 200′ with a heat exchanger core or recuperator core 20 consisting of a material 20′ that exhibits first, perpendicular or vertical boreholes 22 or process boreholes 22 for the first heat exchanging medium M1 or process medium M1 parallel to the symmetry axis, i.e., in the Z direction, as well as second or horizontal boreholes 24 or service boreholes 24 perpendicular thereto for the second heat exchanging medium M2 or service medium M2.

The boreholes 22 and 24 do not communicate with each other, so that the first and second heat exchanging media M1 and M2 cannot become mixed together. A guiding disk frame 50, 60 with an array of several guiding disks 50 is provided to laterally and vertically limit and control the flows of the first and second heat exchanging media M1 and M2. The guiding disks 50 are clamped in corresponding brackets 60. Additionally depicted are the lateral surface 20m and end surfaces 20e of the heat exchanging element 20 designed as a block, as well as the surfaces 20v, 20h or inner surfaces 20v, 20h of the vertical or horizontal channels of boreholes 22, or 24.

In the present invention, a block-shaped heat exchanging element 20 according to FIG. 4 can have not just end surfaces 20e and a lateral surface 20m, but also precisely the inner surfaces 20v and 20h, of the first or second boreholes 22 or 24 for the process medium M1 or service medium M2 that consist of a corresponding coating 30 made of an abrasion-resistant coating material 30′.

This is illustrated once again on FIG. 5A to 7B within the framework of two sequential procedural steps in a schematic and cut side view or a schematic top view.

FIGS. 5A and 5B present a section of the arrangement from FIG. 4 for a block-shaped heat exchanging element 20, depicting exclusively those vertical boreholes 22 parallel to the Z-direction that serve to transport the process medium M1 or first heat exchanging medium M1 and exhibit inner surfaces 20v, for example.

The base material 20′ of this heat exchanging element 20 can be a conventional material 20′. In the transition to the intermediate state shown on FIG. 5B, the end surfaces 20e of the block-shaped heat exchanging element 20 and the inner surfaces 20v or inner sides 20v of the vertical boreholes 22 or vertical flow channels 22 are then provided with a coating 30 that contains or consists of the coating material 30′. If necessary, a corresponding coating 30 also arises on the end surface 20e.

The cross section of the vertical boreholes 22 is possibly slightly restricted, in which case the representation on FIG. 5A to 7B is not to scale; the actual reduction in the clear width of the boreholes 22 and 24 with the inner surfaces 20v and 20h is only minimally curtailed.

The same holds true for a coating that relates to the lateral surface 20m and inner surfaces 20h or inner sides 20h of the horizontal boreholes 24, as illustrated on FIGS. 6A and 6B analogously to FIGS. 5A and 5B.

FIGS. 7A and 7B present a top view depicting the arrangement of the block recuperator 200′ on FIGS. 4 to 6B opposite the Z-direction, i.e., directly on the upper end surface 20e of the underlying cylinder.

In the case of tubular heat exchangers not graphically depicted here, such a coating 30 on the inside and/or outside of a respective heat exchanger tube is also conceivable.

Claims

1. A heat exchanging element for a heat exchanger, the heat exchanging element comprising:

a body containing or essentially consisting of one or more materials selected from the group consisting of graphitic materials, graphites, and open-pored, unsintered silicon carbide materials;

said body being formed with a first contact region and a second contact region for separate contact in terms of flow with a first heat exchanging medium forming a first process medium and with a second heat exchanging medium forming a second process medium, respectively, for effecting separate heat exchange; and

a coating with one or more materials selected from the group of materials consisting of silicon carbide materials, carbide oxide materials, silicide materials, tungsten titanate materials, oxide materials, pyrocarbon, diamond, and derivatives and combinations thereof;

said coating being disposed on at least one of said first and second contact regions and partially or completely coating the respective said contact region.

2. The heat exchanging element according to claim 1, which comprises an impregnation composed of an impregnating material containing or consisting of one or more materials selected from the group consisting of resin materials, phenol resin materials, and derivatives and combinations thereof.

3. The heat exchanging element according to claim 2, wherein said impregnation with the impregnating material is formed entirely or partially on and/or in said coating and/or entirely or partially on and/or in said first contact region and said second contact region.

4. The heat exchanging element according to claim 1, wherein said coating is a CVD coating.

5. The heat exchanging element according to claim 1, wherein said coating is a chemical and/or physical conversion area.

6. The heat exchanging element according to claim 5, wherein said conversion area is formed by a process involving an entire or partial chemical and/or physical conversion of a material forming said first contact region and/or said second contact region.

7. The heat exchanging element according to claim 1, wherein said coating is a plasma-sprayed coating or a flame-sprayed coating.

8. The heat exchanging element according to claim 1, wherein said body is formed as a heat exchanger plate or a recuperator plate of a plate heat exchanger or a plate recuperator.

9. The heat exchanging element according to claim 1, wherein said body is formed as a heat exchanger core or recuperator core of a block heat exchanger or block recuperator.

10. The heat exchanging element according to claim 1, wherein said body is formed as a heat exchanger tube or recuperator tube of a tubular heat exchanger or tubular recuperator.

11. The heat exchanging element according to claim 1, wherein:

a material of said heat exchanging element body and the material of said coating are coordinated with each other in such a way that

a ratio between a thermal expansion coefficient for the material of the heat exchanging element body and a thermal expansion coefficient for the material of said coating and/or an impregnating material exhibits a value ranging between about 1.2 and about 0.8.

12. The heat exchanging element according to claim 11, wherein the ratio between the thermal expansion coefficients lies within a range of approximately 1.05 and 0.95 in a temperature range from about 1200° C. to about 2400° C. or a partial range thereof.

13. The heat exchanging element according to claim 11, wherein the heat exchanging element body is a graphite substrate and the material of said coating is a CVD-SiC material.

14. A method of manufacturing a heat exchanging element for a heat exchanger, the method which comprises:

providing a heat exchanging element body for a separate heat exchange in terms of flow between a first heat exchanging medium as a process medium and a second heat exchanging medium as a service medium with a first contact region and with a second contact region for separately contacting the first heat exchanging medium or second heat exchanging medium in terms of flow;

the heat exchanging element body containing or consisting of one or more materials selected from the group of materials consisting of graphite materials, graphites and open-pored and unsintered silicon carbide materials; and

coating at least one of the first and second contact regions entirely or partially with one or more materials selected from the group consisting of silicon carbide, silicon carbide materials, carbide oxide materials, silicide materials, tungsten titanate materials, and derivatives and combinations thereof.

15. The method according to claim 14, which comprises impregnating the heat exchanging body with an impregnation composed of an impregnating material containing or consisting of one or more materials from the group consisting of resin materials, phenol resin materials and derivatives and combinations thereof.

16. The method according to claim 15, which comprises forming the impregnation with the impregnating material entirely or partially on and/or in the coating and/or entirely or partially on and/or in the first contact region and second contact region.

17. The method according to claim 14, which comprises coating by chemical vapor deposition.

18. The method according to claim 14, wherein the coating step comprises chemically and/or physically converting a material of the first and/or second contact region.

19. The method according to claim 14, wherein the coating step comprises plasma spraying and/or flame spraying.

20. The method according to claim 14, which comprises configuring the heat exchanging element as a heat exchanger plate of a plate heat exchanger, as a recuperator plate of a plate recuperator, as a heat exchanger core of a block heat exchanger, as a recuperator core of a block recuperator, as a heat exchanger tube of a tubular heat exchanger, or as a recuperator tube of a tubular recuperator.

21. The method according to claim 14, which comprises:

coordinating a material of the heat exchanging element and the material of the coating with each other in such a way that

a ratio between a thermal expansion coefficient for the material of the heat exchanging element body and a thermal expansion coefficient of the material of said coating and/or an impregnating material exhibits a value ranging between about 1.05 and about 0.95 within a temperature range from about 1200° C. to about 2400° C. or a partial range thereof.

22. The method according to claim 21, which comprises forming the heat exchanging element body as a graphite substrate and coating the contact surfaces with a CVD-SiC material coating.

23. A heat exchanger, comprising: one or more heat exchanging elements according to claim 1.

24. A method of retrofitting a heat exchanger, the method which comprises:

replacing one or more heat exchanging elements with one or more heat exchanging elements according to claim 1; and/or

converting one or more conventional heat exchanging elements into one or more heat exchanging elements by

providing one or more heat exchanging element bodies containing or consisting of one or more materials selected from the group of materials consisting of graphite materials, graphites and open-pored and unsintered silicon carbide materials, and

coating at least one of the first and second contact regions entirely or partially with one or more materials selected from the group consisting of silicon carbide, silicon carbide materials, carbide oxide materials, silicide materials, tungsten titanate materials, and derivatives and combinations thereof.