Tube bundle heat exchanger

Abstract

The present invention relates to a tube bundle heat exchanger (1) having a tube sheet (3), the tube sheet (3) together defining the interior (4) of the tube bundle heat exchanger (1). The tube bundle heat exchanger includes a tube bundle having a plurality of heat exchanger tubes (5) located in the interior (4), and a first fluid flows through the plurality of heat exchanger tubes, which are optionally supported by an additional support plate (6). The heat exchanger tubes (5) have integral fins (51) formed on the outer side of the tube in a helical circumference, the integral fins having fin bottoms, fin side wings and fin tops, and channels having channel bottoms formed between the fins (51). The tube sheet (3) has recesses as passage points, each recess having an inner surface. The outer fins (51) of the heat exchanger tubes (5) protrude at least into the recesses of the tube sheet (3), thereby forming an engagement gap between the inner surface of the recess and the outer fins (51) of the heat exchanger tubes (5) located within the recess in each case. With the aid of a bonding material and taking into account the external fins (51), the heat exchanger tube (5) is integrally bonded to the tube sheet (3). This integral bonding is formed only in the first part of the recess, which extends axially from the end face of the heat exchanger tube (5) through a first part filled with bonding material in the bonding gap, such that the second part of the recess remains in which the bonding gap is not filled with bonding material. The heat exchanger tube (5) also has external fins (51) on the outside of the tube in the region of the second part.

Description

Technical Field

[0001] This invention relates to a tube bundle heat exchanger. Background Technology

[0002] Tube bundle heat exchangers are used to transfer heat from a first fluid to a second fluid. For this purpose, tube bundle heat exchangers typically have a hollow cylinder with multiple tubes arranged inside this hollow cylinder. One of the two fluids can be guided through the tubes, and the other fluid can be guided through the hollow cylinder, specifically around the tubes. The tubes are circumferentially fastened to one or more tube sheets of the tube bundle heat exchanger at their ends. In the manufacturing process of the tube bundle heat exchanger, the tubes are connected to the tube sheet through their ends by, for example, material bonding connections. It is generally desirable to provide a possible method for connecting the tubes of a tube bundle heat exchanger to the tube sheet of the tube bundle heat exchanger that involves minimal labor intensity, is inexpensive, and achieves high quality.

[0003] A method for connecting tubes of a tube bundle heat exchanger to a tube sheet is described in WO 2017 / 025 184 A1. Both the tubes and the tube sheet are made of aluminum or an aluminum alloy and are connected to the tube sheet by means of laser welding, through a material bonding connection. The intensity of the generated laser beam exceeds 1 MW / cm². 2 It is also envisioned that, prior to laser welding, the tubes of the tube bundle heat exchanger are connected to the tube sheet in a form-fit manner.

[0004] The tube bundle heat exchanger to be manufactured has multiple tubes arranged inside a hollow cylinder in its completed operating state. The tube sheet may be in the form of a plate and has holes whose diameter substantially corresponds to the outer diameter of the tubes. Each tube is fastened to one of these holes at one of its ends.

[0005] The tubes can travel straight within a hollow cylinder as a straight tube heat exchanger. In this case, two tube sheets are arranged at opposite ends of the straight tube heat exchanger. Each tube is fastened to one of the two tube sheets at one of its ends.

[0006] The tubes can also travel in a U-shape within a hollow cylinder, serving as a U-tube heat exchanger. Such a U-tube heat exchanger typically has only one tube sheet. This is because, in this case, the tubes are bent into a U-shape, and each can be fastened to the same tube sheet at both ends.

[0007] DE 10 2006 031 606 A1 discloses a method for laser welding a heat exchanger used for exhaust gas cooling, wherein an oscillating motion is additionally superimposed on the feed movement of the laser beam. This oscillating motion occurs substantially in a direction perpendicular to the feed direction. The oscillating motion is performed due to better bridging of the gap.

[0008] Furthermore, WO 2017 / 125 253A1 discloses a method for connecting tubes of a tube bundle heat exchanger to a tube sheet. The tubes are connected to the tube sheet by a material bonding connection using laser welding. For this connection, a laser beam is generated and focused onto the point to be welded in the connection region between the tube and the tube sheet. The laser beam is moved in such a way that it performs a first movement in the connection region, and a second movement superimposed on the first movement and different from the first movement. Through the second movement, the melt bath kinetics are purposefully influenced, and the formed vapor capillaries are advantageously modified. Summary of the Invention

[0009] The fundamental objective of this invention is to reliably connect the tubes of a tube bundle heat exchanger to the tube sheet in a manner that involves minimal labor intensity and achieves high quality.

[0010] The present invention includes a tube bundle heat exchanger having an enclosed housing and at least one tube sheet, the enclosed housing and at least one tube sheet together defining the interior of the tube bundle heat exchanger. The tube bundle heat exchanger includes a tube bundle having a plurality of heat exchanger tubes arranged inside, through which a first fluid can flow, and the plurality of heat exchanger tubes are optionally supported by an additional support plate. The heat exchanger tubes have integral fins formed helically around their outer sides, and the integral fins have fin bottoms, fin sidewalls, and fin tops, and channels with channel bottoms are formed between the fins. The tube bundle heat exchanger includes at least one inlet located at the housing through which a second fluid can be introduced into the interior, and at least one outlet through which the second fluid can be discharged from the interior. The tube bundle heat exchanger optionally includes at least one air chamber arranged at at least one tube sheet for distributing, redirecting, or collecting the first fluid. At least one tube sheet has an opening as a passage point, wherein each opening has an inner surface. The heat exchanger tube protrudes at least with its outer fins into the opening of the tube sheet, thereby forming a joint gap between the inner surface of the opening and the outer fins of the heat exchanger tube located inside the opening in each case. The heat exchanger tube has a material bond with the tube sheet by means of a bonding material and the outer fins, which is formed only in a first portion of the opening extending axially from the end face of the heat exchanger tube, in which the joint gap is filled with the bonding material, such that a second portion of the opening is retained, in which the joint gap is not filled with the bonding material, and in the region of the second portion, the heat exchanger tube continues to have outer fins on the outside of the tube.

[0011] In other words, heat exchanger tubes have external fins on the inside of their entry points into or through the tube sheet. These external fins are used to surround the material of the material-bonded connections, thus providing an airtight seal to prevent the passage of gases or liquids. For purely material-bonded connections, a combination of force-based and interlocking connections can also be advantageously used.

[0012] The bonding material penetrates axially from the end face into the bonding gap, only to a certain extent in the first part, because the outer fins act as an obstacle to free passage, for example, in the case of a flat tube. Therefore, the outer fins form a barrier around which the material must flow or must be melted. The flow of material around the fins is particularly important, especially in the case of welding and adhesive bonding methods. In the case of welding, the outer fins of the heat exchanger tube also partially melt at the end face. Once the temperature of the melt is no longer sufficient to melt the fins located further inward, the melt flow is preferably stopped at one of the outer fins. This barrier prevents further penetration of the melt into the bonding gap. In this way, there is a defined flow process of the bonding material during the bonding operation, which completely seals the bond at or near the end face of the tube.

[0013] In addition to the external fins, the heat exchanger tube may optionally have an internal structure. The internal structure can be in the form of an internal circumferential spiral with a given twist angle. When the heat exchanger tube has spiral circumferential external fins on its outer side, the spacing of the external fins can be the same as, less than, or greater than the spacing given by the twist angle of the circumferential spiral. Therefore, these two structures can differ from each other because, for the connection of the material bond between the outer side of the heat exchanger tube and the container wall, the forms of the external fins and the internal structure can be constructed independently of each other and thus optimized.

[0014] However, certain limitations are imposed on both structures to optimize heat exchange. Therefore, the ratio of the maximum structural height of the external fins to the maximum structural height of the internal structure is preferably in the range of 1.25 to 5 for condenser tubes and preferably in the range of 0.5 to 2 for evaporator tubes.

[0015] First, investment costs are saved because the tube bundle heat exchanger according to the invention can have a substantially more compact construction. These external fins continue into the tube sheet, thereby significantly reducing the number of heat exchanger tubes per unit. Depending on requirements, the finned tubes allow for more efficient energy use or allow for reduced packing, which lowers operating costs.

[0016] This invention is based on the consideration of achieving, in particular, a reliable and high-quality material bond connection between the heat exchanger tubes and the tube sheet with minimal labor intensity. According to the invention, the heat exchanger tubes enter the tube sheet or pass through the tube sheet with their external fins. The external fins are then retained in the material bond connection immediately adjacent to the tube-to-tube sheet. This has a particular advantage: inside the tube bundle heat exchanger, the heat exchanger tubes have continuous external fins for efficient heat transfer.

[0017] In an advantageous embodiment of the invention, the first portion filled with the bonding material may occupy less than 70% of the entire length of the joint gap in the axial direction. Advantageously, the first portion filling the joint gap comprises only less than 50% of the total length. In particular, in the case of welded connections, a filling degree of only 20% of the first portion may be sufficient to produce a liquid-sealed material bond.

[0018] Advantageously, the net width between the fin tips and the inner surface of the opening of the heat exchanger tube can be no greater than 30% of the fin height measured from the bottom of the channel to the fin tips. The barrier effect of the outer fins varies with this net width. In particular, in the case of welding and adhesive bonding methods, the bonding material can be purposefully introduced through this net width of the joint gap to form a first filling portion. The channel formed by the additionally formed helical circumference of the integral fin constitutes another flow channel for the bonding material. However, the channel cross-section is given by the fin height and the spacing between adjacent fins, and this channel cross-section is generally less significant compared to the selected net width.

[0019] Advantageously, the joints formed by the materials can be designed to be airtight and pressure-resistant. In addition to the mechanical stability function that combines effective heat transfer, airtight seals are important in any operating mode to prevent fluid exchange with the surrounding environment.

[0020] In an advantageous embodiment of the invention, the heat exchanger tube has an inner diameter D2 at the passage point, which is larger than the inner diameter D1 of the heat exchanger tube outside the passage point.

[0021] If the heat exchanger tubes also have external fins at their entry points into or through the tube sheet, this is because, in this method, the heat exchanger tubes are widened, resulting in an increase in the inner diameter D2. Due to this widening, the external fins at the entry points are then flattened. However, the material bonding ensures a stable hermetic seal.

[0022] In an advantageous embodiment of the invention, the heat exchanger tubes can be brazed, bonded together, or welded to the tube sheet.

[0023] In addition to the preferred connection types mentioned, other connection types that reliably connect heat exchanger tubes to tube sheets through material bonding can be used.

[0024] In principle, the external fins on the outer side of the heat exchanger tube can preferably travel in a circumferential direction or in an axial direction parallel to the tube axis. In an advantageous embodiment of the invention, the outer side of the heat exchanger tube can have helically circumferential external fins. In the case of helical external fins, only the residual gaps and the circumferential channels extending helically with the external fins must be reliably sealed by a material-bonded connection.

[0025] While suitable homogeneous materials are generally preferred for heat exchanger tubes, in an advantageous embodiment of the invention, it is possible for at least one first heat exchanger tube to be made of a first material and at least one second heat exchanger tube to be made of a second material different from the first material. Regarding mechanical stability, steel tubes, with their exceptionally high strength, can provide particular advantages. On the other hand, copper tubes offer optimization in terms of efficient heat transfer. Other materials, such as titanium, aluminum, aluminum alloys, and copper-nickel alloys, can also be considered. Attached Figure Description

[0026] Exemplary embodiments of the invention will be explained in more detail with reference to the accompanying drawings:

[0027] Figure 1 schematically shows a side view of a tube bundle heat exchanger, with a detailed view of the heat exchanger tubes having external fins.

[0028] Figure 2 schematically shows a front view of the tube sheet with details of the passing points.

[0029] Figure 3 schematically shows the vertical cross-section of the tube sheet in the plane at the point where the heat exchanger tubes pass through, and

[0030] Figure 4 schematically shows a detailed cross-sectional view of the connection between the tube sheet and the heat exchanger tubes, representing the material bonding.

[0031] In all the accompanying drawings, corresponding parts are given the same reference numerals. Detailed Implementation

[0032] Figure 1 schematically shows a side view of a tube bundle heat exchanger 1 having an enclosed housing 2 and two tube sheets 3, which together define an interior 4 of the tube bundle heat exchanger 1. The tube bundle heat exchanger 1 comprises a tube bundle having a plurality of heat exchanger tubes 5 arranged within the interior 4, through which a first fluid for heat transfer can flow, and the heat exchanger tubes are supported by additional support plates 6. Such support plates 6 often also additionally serve as guide plates for fluid flow. The tube bundle heat exchanger 1 additionally includes an air chamber 7 that, as needed, distributes, directs, or collects the first fluid within the interior of the heat exchanger tubes. At least one inlet 8 and at least one outlet 9 are provided at the housing 2, through which a second fluid for heat transfer can be introduced into the interior, and through which the second fluid can be discharged from the interior. In the detailed view, the heat exchanger tubes 5 with external fins 51 are enlarged. Using another known rolling process, integral fins are formed on the outside of the tube and spiral around the tube axis A.

[0033] Figure 2 schematically shows a front view of the tube sheet 3 with the passage point. At the passage point, the opening in the tube sheet 3 preferably has a size such that the heat exchanger tube 5, together with its external fins 51, can be introduced into the opening and connected thereby by a material-bonded connection. The welded, adhesively bonded, and welded connection, as a material-bonded connection 20, can be made at the passage point from the end face, on a first portion of the wall thickness of the tube sheet 3, and enters a fluid-tight connection. In the second portion extending into the depth, the remaining unfilled joint gap, not visible in Figure 2, is retained in the wall of the tube sheet 3.

[0034] Figure 3 schematically shows a vertical cross-section of the tube sheet 3 in the plane of the passage point of the heat exchanger tube 5. The heat exchanger tube 5 shown has external fins 51 on its outer side. In the exemplary embodiment shown, the heat exchanger tube 5 passes through the tube sheet 3 at the opening 31, which serves as the passage point. At this passage point, the heat exchanger tube 5 has continuous external fins 51. The material bonding connection 20, which has not yet been performed in Figure 3, for example, in the form of a continuous weld around the circumference of the tube sheet 3, is located in a portion of the bonding gap 10 after the bonding operation. Depending on the material combination of the tube sheet 3 and the heat exchanger tube 5, favorable intermetallic phase formation in the melt bath can occur at the weld point. A suitable method for producing a material bonding connection with locally confined melt flow is, in particular, laser welding.

[0035] Figure 4 schematically shows a detailed cross-sectional view of the connection 20, which is a material bond between the tube sheet 3 and the heat exchanger tube 5. In the illustrated embodiment, the heat exchanger tube 5 has been inserted into the opening 31 formed in the tube sheet 3 along the tube axis A and is flush with the outer surface of the tube sheet at its end face 53.

[0036] The heat exchanger tube 5 has integral fins formed on the outer side of the tube in a spiral circumference, the integral fins having a fin bottom 511, fin side wings 512, and fin top 513. Channels 52 with channel bottoms 521 are formed between adjacent outer fins 51. Figure 4 shows a weld as a material-bonded connection 20, formed, for example, during laser welding. Suitable welding additives can optionally be used during the bonding process. In this way, the material flow and quantity can also be precisely matched to the desired bonded connection. In the case of the material-bonded connection shown, certain areas of the tube sheet 3 and some of the outer fins 51 on the heat exchanger tube 5 are also at least partially melted due to the heat input of the laser and integrated into the bonding material due to process considerations. During bonding, the melt enters the bonding gap 10 from the end face 53 but is blocked after a certain penetration depth, such that only the first portion 101 of the bonding gap 10 at the end face is filled together with the outer fins 51. Further passage of the melt is blocked by the external fins 51, which prevent it from melting or flowing to the surrounding area due to the reduced temperature at the front of the melt, thus acting as a barrier. In this way, a defined flow process of the bonding material exists during the bonding operation, which can completely seal the bonding point at or near the tube end face 53.

[0037] Therefore, the heat exchanger tube 5 has a connection 20 that is materially bonded to the tube sheet 3, and this connection is formed only in a first portion 101 of the opening 31 extending axially from the end face 53 of the heat exchanger tube 5. The second portion 102 of the opening 31 is not filled with bonding material. In the second portion 102, the heat exchanger tube 5 continues to have external fins 51 on the outer side of the tube.

[0038] List of reference numerals

[0039] 1. Tube bundle heat exchanger

[0040] 2. Outer shell

[0041] 3 Tube Sheets

[0042] 31 Opening

[0043] 311 The inner surface of the opening

[0044] 4. Internal

[0045] 5 heat exchanger tubes

[0046] 51 External fins

[0047] 511 Fin bottom

[0048] 512 Fin Side Wings

[0049] 513 Fin tip

[0050] 52 channels

[0051] 521 bottom of channel

[0052] 53 End face

[0053] 6 Support plates

[0054] 7. Inflation box

[0055] 8 entrances

[0056] 9 Exports

[0057] 10 Joint gap

[0058] 101 Part 1

[0059] 102 Part Two

[0060] 20. Material bonding connection

[0061] A. Pipe axis, axial direction

[0062] D1, D2 pipe inner diameter

[0063] Arrow fluid flow

Claims

1. A tube bundle heat exchanger having an enclosed housing (2) and at least one tube sheet (3), the housing and the at least one tube sheet together defining the interior (4) of the tube bundle heat exchanger (1), comprising: - A tube bundle having a plurality of heat exchanger tubes (5) arranged inside (4) and through which a first fluid can flow, and wherein the plurality of heat exchanger tubes are optionally supported by an additional support plate (6), wherein the heat exchanger tubes (5) have integral fins that are spirally circumferentially formed on the outer side of the tube and have fin bottoms (511), fin side wings (512) and fin tops (513), and channels (52) with channel bottoms (521) are formed between the fins. - At least one inlet located at the outer casing (2), by means of which the second fluid can be introduced into the interior (4); and at least one outlet (9), by means of which the second fluid can be discharged from the interior (4). - Optionally, at least one air-filled box (7) is arranged at at least one tube sheet (3) for dispensing, redirecting, or collecting the first fluid. At least one tube sheet (3) has an opening (31) as a passage point, wherein each opening (31) has an inner surface (311). Its features are, - The heat exchanger tube (5) protrudes at least with its outer fins (51) into the opening (31) of the tube sheet (3), thereby forming a joint gap (10) between the inner surface (311) of the opening (31) and the outer fins (51) of the heat exchanger tube (5) located inside the opening (31) in each case. - With the aid of bonding material and external fins (51), the heat exchanger tube (5) has a material-bonded connection (20) with the tube sheet (3), which is formed only in a first portion (101) of the opening (31), which extends axially (A) from the end face (53) of the heat exchanger tube (5), wherein the joint gap (10) in the first portion (101) is filled with bonding material, such that a second portion (102) of the opening (31) is retained, wherein the joint gap (10) is not filled with bonding material, wherein the heat exchanger tube (5) continues in the region of the second portion (102) with external fins (51) on the outside of the tube.

2. The tube bundle heat exchanger according to claim 1, characterized in that, The first portion (101) filled with bonding material occupies less than 70% of the length of the entire joint gap (10) in the axial direction (A).

3. The tube bundle heat exchanger according to claim 1 or 2, characterized in that, The net width between the top fin tip (513) of the heat exchanger tube (5) and the inner surface (311) of the opening (31) is no more than 30% of the fin height measured from the bottom of the channel (521) to the top fin tip (513).

4. The tube bundle heat exchanger according to claim 1, characterized in that, The material bonding connection (20) is designed to be airtight and pressure resistant.

5. The tube bundle heat exchanger according to claim 1, characterized in that, The inner diameter D2 of the heat exchanger tube (5) in the opening (31) which is the passage point is greater than the inner diameter D1 of the heat exchanger tube (5) outside the passage point.

6. The tube bundle heat exchanger according to claim 1, characterized in that, The heat exchanger tubes (5) are brazed, bonded together, or welded to the tube sheet (3).

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