Pipe-in-pipe heat exchanger

Abstract

The invention relates to a tube-in-tube heat exchanger (1) comprising an inner tube (10) with a first flow path (11) defined therein and an outer tube (20) arranged around the inner tube (10) and thus defining a second flow path (21) between the inner tube (10) and the outer tube (20). It is proposed that the inner tube (10) be designed, in particular, as a metallic corrugated tube.

Description

[0001] The present invention relates to a tube-in-tube heat exchanger having the features of claim 1 and a method for producing the same having the features of claim 7.

[0002] Heat exchangers of this type are known and used in a wide variety of applications. Examples of such heat exchangers are disclosed in DE 10 2021 212 182 A1 and DE 10 2021 214 149 A1.

[0003] A disadvantage of previously known heat exchangers is that their outer and inner tubes are made of metal, usually aluminum, and are therefore complex to manufacture. To thermally insulate the heat exchanger, which is a regular requirement, especially in the automotive sector, an additional layer, such as foam rubber, must be applied to the metal outer tube, which requires additional installation space. Furthermore, curved tube geometries can only be produced with the existing systems at considerable expense.

[0004] The object of the present invention is to provide a tube-in-tube heat exchanger that can be manufactured easily. In particular, a tube-in-tube heat exchanger is to be provided that allows even curved tube geometries to be realized without great effort. At the same time, the disadvantages of the prior art are to be at least partially avoided.

[0005] This object is achieved by a method with the features of claim 1. Preferred features are the subject of the dependent claims. Further advantages and features can be found in the general description and the exemplary embodiments. The present invention also relates to a manufacturing method with the features of claim 7.

[0006] The tube-in-tube heat exchanger according to the invention comprises an inner tube with a first flow path defined therein and an outer tube arranged around the inner tube, thus defining a second flow path between the inner tube and the outer tube. A first fluid having a first temperature can thus flow through the first flow path, while a second fluid having a second temperature can flow through the second flow path. In this way, heat can be exchanged between the fluids through the wall of the inner tube. The tube-in-tube heat exchanger is characterized in that the inner tube is designed, at least in sections, as a corrugated tube.

[0007] A "corrugated pipe" is a tubular structure containing a series of adjacent parallel corrugations or ribs. These corrugations give the pipe its characteristic shape, which resembles a series of connected semicircular or trapezoidal channels. The primary purpose of the corrugations is to provide the pipe with structural strength and flexibility.

[0008] Due to its shape, the corrugated pipe offers a wall with a large surface area for heat exchange. Furthermore, the corrugation crests can serve to support the corrugated pipe on the inside of the outer pipe. Furthermore, the cavities or circumferential grooves formed between each corrugation crest can form part of the second flow path. Its flexibility also allows for heat exchanger geometries featuring a curved tube-in-tube design. Such a corrugated pipe is very flexible and is also suitable as an inner mandrel for the downstream heat-setting process of the outer pipe. Particularly when the corrugated pipe is made of metal, its excellent thermal conductivity allows heat to be introduced to quickly and effectively heat the outer pipe. Its flexibility is similar to that of a spiral spring and can therefore be used as such in the heat-setting process.

[0009] In a preferred embodiment of the tube-in-tube heat exchanger according to the invention, the inner tube contains at least 50 vol.% of a metal (or a metal alloy), in particular stainless steel. This ensures high thermal conductivity of the inner tube, which leads to efficient heat exchange. Furthermore, the inner tube can thus be easily heated and used advantageously in the manufacture of the tube-in-tube heat exchanger.

[0010] In a preferred embodiment of the tube-in-tube heat exchanger according to the invention, the outer tube contains at least 50 vol.% of a polymer. In particular, the polymer is a thermoplastic, a thermoplastic elastomer, an elastomer, or a combination thereof. This allows the outer tube to be manufactured easily and also provides thermal insulation to the outside.

[0011] In a preferred embodiment of the tube-in-tube heat exchanger according to the invention, the outer tube has on its inner side a plurality of radially inwardly projecting webs extending along the longitudinal direction, which are arranged to support the inner tube, in particular on its corrugation crests. The cavities or longitudinal grooves formed between the webs communicate in a fluid-conducting manner with the cavities formed between two corrugation crests of the corrugated tube, thus forming the second flow path. The web contour or cross-sectional geometry can be designed as desired depending on requirements. By combining the longitudinal grooves defined by the outer tube with the circumferential grooves defined by the corrugated tube, which are in fluid-conducting communication with each other, turbulent flow behavior can be achieved, which can increase heat exchange and efficiency.Furthermore, such an outer tube can be manufactured in a simple manner, in particular by extrusion.

[0012] In a preferred embodiment of the tube-in-tube heat exchanger according to the invention, the heat exchanger has a connecting element with a third flow path defined therein, which communicates with the second flow path in a fluid-conducting manner, wherein the connecting element is sealed with respect to the inner tube by means of a sealing element, in particular an O-ring seal.

[0013] In this way, a tight and, in particular, detachable connection can be created between the inner tube and the connecting element, especially when the inner tube is made of metal and the connecting element is made of plastic. Preferably, the connecting element contains at least 50 vol.% of a polymer. In particular, the polymer is a thermoplastic, a thermoplastic elastomer, an elastomer, or a combination thereof.

[0014] Preferably, the connecting element is sealed against the outer tube by means of a sealing element, in particular an O-ring seal. This creates a tight and, in particular, detachable connection between the outer tube and the connecting element.

[0015] In a preferred embodiment of the tube-in-tube heat exchanger according to the invention, the inner tube and / or the outer tube are inserted into the connecting element and secured thereto without a material connection. This creates a detachable and, particularly in combination with the previously described sealing elements, sufficiently tight connection that can be manufactured particularly easily. Furthermore, the heat exchanger is easier to recycle because the inner tube and / or the outer tube can be easily separated from the connecting element.

[0016] According to what has already been described above and what has been described below, the problem set out at the outset is also solved by a method having the features of claim 8. The method according to the invention for producing a tube-in-tube heat exchanger comprises the following steps: - Providing an inner pipe designed as a corrugated pipe; - Arranging an outer tube around the inner tube; - Bending the structure consisting of the outer and inner tubes into a curved shape.

[0017] This allows for curved geometries for the heat exchanger. Due to its flexibility, the corrugated pipe is ideally suited to being bent while providing sufficient support for the outer pipe.

[0018] Preferably, the inner tube is heated before bending to heat the outer tube, and then passively or actively cooled after bending to form a curved structure consisting of the outer and inner tubes. Heating the outer tube via the inner tube can be achieved particularly easily if the inner tube has high thermal conductivity, e.g., if it is made primarily of metal. The interior of the inner tube can be filled with hot steam or hot air.

[0019] In a preferred embodiment of the method according to the invention, the outer tube is arranged by extruding the outer tube onto the inner tube, which serves as a mandrel. The structure consisting of the outer and inner tubes can thus be manufactured continuously, for example, using a cross-head extrusion die, in which the corrugated tube is coated with a compound as it passes through the extrusion die, which compound may harden after the structure is bent into the outer tube.

[0020] It is expressly pointed out that the embodiments of the invention explained above can be combined individually or in any technically reasonable combination with each other with the subject matter of the independent claims.

[0021] Modifications and embodiments of the invention, as well as further advantages and details of the invention, can be found in the following description and the drawings. The schematic figures show: Fig. 1 shows a first embodiment of a tube-in-tube heat exchanger according to the invention in a sectional view; and Fig. 2 a cross-sectional view of the tube-in-tube heat exchanger from Fig. 1 to line AA.

[0022] Parts that have the same or similar functions are provided with identical reference numbers where appropriate.

[0023] Individual technical features of the embodiments described below can also be combined with previously described embodiments as well as the features of the independent claims and any further claims to form subject matter according to the invention.

[0024] The Fig. 1 and Fig. 2 show a first embodiment of a tube-in-tube heat exchanger 1 according to the invention with an inner tube 10 containing a first flow path 11 defined therein and an outer tube 20 arranged coaxially around the inner tube 10 with respect to a longitudinal center axis L of the heat exchanger 1 and thus defining a second flow path 21, separate from the first flow path 11, between the inner tube 10 and the outer tube 20. In this way, a first fluid with a first temperature can flow along a first flow direction F1 through the first flow path 11, while a second fluid with a second temperature can flow along a second flow direction F2 through the second flow path 21.

[0025] The inner tube 10 is designed as a corrugated tube containing a series of adjacent parallel ribs or waves with wave crests 12 and wave troughs 13. Between the wave crests 12, a series of adjacent parallel circumferential grooves 15 are formed. As shown in Fig. 2, the outer tube 20 has on its inner side 22 a plurality of webs 23 which protrude radially inward and extend along the longitudinal direction and are arranged to support the corrugation crests 12 of the inner tube 10. Longitudinal grooves 25 are formed between the webs 23. The circumferential grooves 15 defined by the inner tube 10 and the longitudinal grooves 25 defined by the outer tube 20 communicate with one another in a fluid-conducting manner and form the second flow path 21.

[0026] Furthermore, the tube-in-tube heat exchanger 1 has two end-side connection elements 30a, 30b on both sides of the tube-in-tube construction 10, 20, each of which contains a third flow path 31 defined therein, which communicates fluidically with the second flow path 21. Each of the connection elements 30a, 30b is sealed from the inner tube 10, more precisely from its non-corrugated end pieces or end nozzles 14, by means of an O-ring seal 32. Furthermore, each of the connection elements 30a, 30b is sealed from the outer tube 20 by means of a further O-ring seal 33.

[0027] In the present case, the inner tube 10 and outer tube 20 are inserted into and secured to the connecting element 30a, 30b without a material connection, such as a welded joint. Such a tube-in-tube heat exchanger 1 can be easily assembled and disassembled, and its components are easily recycled individually.

[0028] The heat exchanger 1 described here is ideally suited for the realization of curved geometries. In particular, curved geometry or curved shape is understood to mean a structure consisting of inner and outer tubes 10, 20, which, compared to the Fig.1, has at least one bend or curvature in both the inner tube 10 and the outer tube 20. Due to its good flexibility and thermal conductivity, the inner tube 10, designed as a corrugated tube, is ideally suited as a mandrel for the outer tube 20 during the bending process. For example, the outer tube 20 can be extruded onto the inner tube and bent into the desired shape before the extrusion mass cools. Alternatively, the inner tube 10 itself can be used to bring the outer tube 20 arranged thereon to a bendable temperature, for example by filling the first flow path 11 with hot steam or hot air.

[0029] It should also be noted that “having” does not exclude other elements or steps, and “a” or “an” does not exclude a plurality.

[0030] The scope of protection of the present invention is given by the claims and is not limited by the features explained in the description or shown in the figures. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 212 182 A1

[0002] DE 10 2021 214 149 A1

[0002]

Claims

[1] Tube-in-tube heat exchanger (1), comprising: - an inner tube (10) having a first flow path (11) defined therein; and - an outer tube (20) arranged around the inner tube (10) and thus defining a second flow path (21) between the inner tube (10) and the outer tube (20), characterized by that the inner pipe (10) is designed as a corrugated pipe. [2] Tube-in-tube heat exchanger (1) according to claim 1, wherein the inner tube (10) contains at least 50 vol.% of a metal (metal alloy), in particular stainless steel. [3] Tube-in-tube heat exchanger (1) according to claim 1 or 2, wherein the outer tube (20) contains at least 50 vol.% of a polymer, in particular a thermoplastic, a thermoplastic elastomer and / or an elastomer. [4] Tube-in-tube heat exchanger (1) according to one of the preceding claims, wherein the outer tube (20) has on its inner side (22) a plurality of webs (23) projecting radially inwards and extending along the longitudinal direction, which are arranged in a supporting manner on the inner tube (10), in particular on its corrugation crests (12). [5] Tube-in-tube heat exchanger (1) according to one of the preceding claims, comprising a connecting element (30a, 30b) with a third flow path (31) defined therein, which communicates with the second flow path (21) in a fluid-conducting manner, wherein the connecting element (30a, 30b) is sealed off from the inner tube (10) by means of a sealing element, in particular an O-ring seal (32). [6] Tube-in-tube heat exchanger (1) according to claim 5, wherein the connecting element (30a, 30b) is sealed with respect to the outer tube (20) by means of a sealing element, in particular an O-ring seal (33). [7] Tube-in-tube heat exchanger (1) according to claim 5 or 6, wherein the inner tube (10) and / or outer tube (20) is inserted into the connecting element (30a, 30b) and fastened thereto without a material connection. [8] Method for producing a tube-in-tube heat exchanger (1) according to one of the preceding claims, comprising the following steps: - providing an inner pipe (10) designed as a corrugated pipe; - arranging an outer tube (20) around the inner tube (10); - Bending the structure consisting of the outer and inner tubes (10, 20) into a curved shape. [9] Method according to claim 8, wherein before bending, the inner tube (10) is heated to heat the outer tube (20) and after bending, it is cooled passively or actively to form a curved structure of outer and inner tube (10, 20). [10] A method according to any one of claims 8 or 9, wherein the arranging of the outer tube (20) comprises extruding the outer tube (20) onto the inner tube (10) serving as a mandrel.

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