Double tube heat exchanger, manufacturing method, use and hydrogen filling station

Abstract

The invention relates to a double-tube heat exchanger for heating a cryogenic fluid, in particular cryogenic hydrogen, comprising an outer tube and an inner tube arranged inside the outer tube, wherein the inner tube is configured for the flow of the cryogenic fluid, and wherein an intermediate space between the inner tube and the outer tube is configured for the flow of a heat exchange medium, wherein the double-tube heat exchanger further comprises an intermediate piece (240) that surrounds the inner tube and is arranged in the intermediate space, wherein the intermediate piece (240) has a base body (242) that is at least substantially cylindrical and has a longitudinal axis (L), wherein the base body (242) has a through-opening (246) along the longitudinal axis (L) through which the inner tube is guided, and wherein the intermediate piece (240) has fins (244) on an outer side of the base body (242).which run at least substantially parallel to the longitudinal axis (L) and are radially aligned to the longitudinal axis (L), and wherein the intermediate piece (240) is clamped onto the inner tube.

Description

[0001] The invention relates to a double-pipe heat exchanger for heating a cryogenic fluid, in particular cryogenic hydrogen, a method for manufacturing such a double-pipe heat exchanger, a use of such a double-pipe heat exchanger, and a hydrogen filling station with such a double-pipe heat exchanger.

[0002] In applications or systems that use cryogenic fluids such as hydrogen, the cryogenic fluid often needs to be heated. An example of this is a hydrogen filling station, where hydrogen is initially in liquid form at approximately -253°C and then needs to be heated before refueling a vehicle.

[0003] Heat exchangers (or heat transfer units) can be used to heat fluids in general. One type of heat exchanger is the so-called double-tube heat exchanger, in which an inner tube is surrounded by an outer tube. The fluid to be heated can, for example, flow in the inner tube, while the heat exchange medium flows in a space between the inner and outer tubes.

[0004] However, the use of double-tube heat exchangers in cryogenic applications, especially high-pressure cryogenic applications, presents several challenges. Due to the high pressure (up to PN 1000, i.e., 1000 bar at room temperature), the wall thickness of the inner tube (in which, for example, the hydrogen is carried) must be very large. This results in high thermal resistance and significant demands and costs for the manufacturing and joining of the tubes (especially welds). Furthermore, the very low cryogenic temperatures in the inner tube (down to -253 °C for cryogenic hydrogen) lead to severe icing of gaseous or liquid heat transfer fluids in the annular space (intermediate space) of the double tube.

[0005] This can or often does lead to a blockage of the pipe and an increase in pressure loss, as well as a reduction in heat transfer between the media.

[0006] Another type of heat exchanger is the so-called medium-to-air heat exchanger, or in this specific case, a hydrogen-to-air heat exchanger. However, several problems can arise here as well. Due to the low heat transfer coefficient, very large dimensions are generally unacceptable for applications such as hydrogen refueling stations. Icing usually prevents continuous operation, necessitating the use of redundant heat exchangers for recuperative operation. Steam clouds at the heat exchangers are also generally unacceptable for applications such as hydrogen refueling stations. Furthermore, at low hydrogen temperatures, a significant amount of energy is lost to the air and cannot be utilized in the downstream refueling process, leading to high electricity costs and thus reducing the overall efficiency of hydrogen refueling stations.

[0007] Against this background, the task arises to make the heating of a cryogenic fluid, especially cryogenic hydrogen, as cost- and energy-efficient as possible. Disclosure of the invention

[0008] This problem is solved by a double-pipe heat exchanger, a method for manufacturing a double-pipe heat exchanger, an application of a double-pipe heat exchanger, and a hydrogen refueling station with the features of the independent claims. Preferred embodiments are the subject of the dependent claims and the following description. Advantages of the invention

[0009] The invention relates to the heating of a cryogenic fluid, in particular cryogenic hydrogen, using a heat exchanger, and the specific application thereof, especially at hydrogen filling stations.

[0010] In one embodiment, the invention relates to a double-tube heat exchanger for heating a cryogenic fluid, in particular cryogenic hydrogen. The double-tube heat exchanger has an outer tube and an inner tube arranged inside the outer tube. Typically, the inner tube is arranged concentrically inside the outer tube. The inner tube is configured for the flow of the cryogenic fluid, while a space between the inner and outer tubes is configured for the flow of a heat exchange medium.

[0011] As is typical for a double-tube heat exchanger, this one can have an inlet opening for the cryogenic fluid connected to the inner tube, as well as an outlet opening for the cryogenic fluid, also connected to the inner tube. Furthermore, the double-tube heat exchanger can have an inlet opening for the heat exchange medium connected to the space between the tubes, as well as an outlet opening for the heat exchange medium, also connected to the space between the tubes.

[0012] Furthermore, the double-pipe heat exchanger has an intermediate piece (or so-called inner part) that surrounds the inner pipe and is located in the space between them. The intermediate piece has a base body that is at least substantially cylindrical with a longitudinal axis, the base body having a through-opening along this longitudinal axis through which the inner pipe passes. On one outer surface of the base body, the intermediate piece has fins (or ribs) that run at least substantially parallel to the longitudinal axis (of the base body) and are oriented radially to this longitudinal axis. The intermediate piece is also clamped onto the inner pipe.

[0013] The intermediate piece enables efficient and cost-effective heating of a cryogenic fluid using a double-tube heat exchanger, as it facilitates efficient heat transfer between the cryogenic fluid being heated and the heat exchange medium. Because the intermediate piece is clamped onto the inner tube, rather than welded to it, the double-tube heat exchanger can also be used to heat cryogenic fluids at high pressures, such as pressures exceeding 500 bar or even 900 bar (calculated at room temperature). The double-tube heat exchanger, or at least the inner tube, can therefore be designed for PN 500, PN 900, or even PN 1000 (pressure ratings of 500 bar, 900 bar, or 1000 bar, respectively, at room temperature). The clamping mechanism ensures a secure and reliable thermal connection between the inner tube and the intermediate piece.

[0014] The fins or ribs of the intermediate piece allow for even more efficient heat transfer while maintaining a compact design. The number of fins can be selected depending on the situation or application and the required or desired heat transfer.

[0015] It is advantageous for the fins to be formed as a single piece with the base. This allows for a stable and robust intermediate section and efficient heat transfer between the fins and the base. Stainless steel is particularly well-suited as a material for the fins and / or the base; that is, the fins and / or the base can be made of stainless steel or even entirely of stainless steel. Stainless steel allows for sufficiently simple processing, has adequate thermal conductivity and heat capacity, and is also suitable for cryogenic temperatures down to -253°C.

[0016] In one embodiment, the base body has a gap that runs at least substantially parallel to the longitudinal axis and is radially oriented to the longitudinal axis, extending radially outward through the base body from the through-opening. Thus, the base body is not a solid cylinder, but has a C-shaped cross-section. This allows, on the one hand, the inner tube to be easily inserted into the through-opening and, on the other hand, the base body or the intermediate piece to then be firmly clamped onto the inner tube. Preferably, the intermediate piece has one or more clamping means, in particular screws, by means of which the base body is clamped in the area of ​​the gap, so that the intermediate piece is clamped onto the inner tube. For this purpose, the base body can, for example, have one or more through-holes for the clamping means.The screws have one or more through-holes extending across the gap. In the case of screws, the gap can be reduced when clamped, thus securely clamping the base body to the inner tube.

[0017] In one embodiment, the base body has a further gap that runs at least substantially parallel to the longitudinal axis and is radially oriented to the longitudinal axis, and which extends radially outwards from the through-opening through only a portion of the base body. This further gap is oriented at least substantially parallel to the (previously mentioned) gap. This allows for simpler and better clamping of the intermediate piece or base body to the inner tube, thus increasing heat transfer even at high pressures of the cryogenic fluid in the inner tube.

[0018] In one embodiment, the ratio of the diameter of the base body to the diameter of the through-opening, in each direction perpendicular to the longitudinal axis, is between 1.5 and 10, particularly between 2 and 5. In another embodiment, the ratio of the diameter of the intermediate piece, including the fins, to the diameter of the base body, in each direction perpendicular to the longitudinal axis, is between 1.1 and 2, particularly between 1.1 and 1.5. The specific values ​​to be selected for these ratios (particularly for the first ratio), i.e., the thickness of the base body, may depend on the required thermal resistance to prevent freezing. The number of fins or ribs and their dimensions (i.e., the second ratio) may depend on the required heating surface.However, with the aforementioned values ​​of the ratios, good efficiency can be achieved even at high pressures, especially for cryogenic fluids such as hydrogen, which need to be heated.

[0019] Longitudinal finned tubes are typically used in applications involving viscous fluids. The fins were added to achieve a more compact design. Because the inner section is clamped, it can be used in high-pressure systems.

[0020] The proposed design allows the heat exchange medium to freeze, so that fluids such as potassium formate and / or glycol can be used as the heat exchange medium, making the heating process using the double-tube heat exchanger safer compared to systems using oil as the heat exchange medium.

[0021] Cryogenic fluids can be heated using such heat exchange media. Once the heat exchange medium has cooled, it can be stored and used in a further process stage, for example, to cool hydrogen elsewhere, such as at another point in a hydrogen filling station. This increases the overall efficiency of the entire system, i.e., the hydrogen filling station.

[0022] The invention is schematically illustrated in the drawing using exemplary embodiments and is described below with reference to the drawing. Brief description of the drawing

[0023] Figure 1 schematically shows a double-pipe heat exchanger according to the invention in a preferred embodiment. Figure 2a schematically shows a part of a double-pipe heat exchanger according to the invention in a further preferred embodiment. Figure 2b schematically shows the part of the double-pipe heat exchanger according to the invention made of Figure 2aIn another view. Figure 3 schematically shows a hydrogen filling station according to the invention in a preferred embodiment. Detailed description of the drawing

[0024] In Figure 1 A schematic representation of a double-pipe heat exchanger 100 according to the invention, in a preferred embodiment, is shown in a sectional view. This heat exchanger can be used to heat a cryogenic fluid a, such as cryogenic hydrogen, which is supplied to the double-pipe heat exchanger 100. The basic principle of the double-pipe heat exchanger 100 corresponds to that of a conventional double-pipe heat exchanger.

[0025] The double-tube heat exchanger 100 has an inner tube 110 through which the cryogenic fluid a to be heated is guided. For this purpose, the cryogenic fluid a is supplied via an inlet opening 112 and then guided through the inner tube 110 to an outlet opening 114, through which the cryogenic fluid a is discharged from the double-tube heat exchanger 100. The inlet opening 112 and the outlet opening 114 can each be designed, for example, as a flange or as part of a flange.

[0026] The double-pipe heat exchanger 100 further comprises an outer pipe 120, wherein the inner pipe 110 is arranged inside the outer pipe 120, in particular concentrically. An example of a longitudinal axis L is shown, with the inner pipe 110 and the outer pipe 120 arranged concentrically around it. The outer pipe 120 can, for example, have a flange 126 or 128 at each end, through which the inner pipe 110 is guided.

[0027] A space 130 between the inner tube 110 and the outer tube 120 is designed for the flow of a heat exchange medium b. For this purpose, the outer tube 120 can have an inlet opening 122 through which the heat exchange medium b can be introduced into the space 130, and an outlet opening 124 through which the heat exchange medium b can be discharged from the space 130. For example, the inlet opening 122 and the outlet opening 124 are arranged radially (with respect to the longitudinal axis L). Likewise, the inlet opening 122 and / or the outlet opening 124 can each be arranged in one of the flanges 126, 128, and thus, in particular, also in the longitudinal direction.

[0028] An intermediate piece 140 is now arranged in the space 130. The intermediate piece 140 surrounds the inner tube 110 and has a base body that is at least substantially cylindrical with a longitudinal axis, the longitudinal axis of which can correspond to the longitudinal axis L of the double-tube heat exchanger 100.

[0029] The double-pipe heat exchanger 100 shown here is intended only as an example to illustrate the invention; a double-pipe heat exchanger can be designed differently, for example, it can have several separate outer pipes that surround a longer inner pipe, thus forming several spaces, each containing an intermediate section. The heat exchange medium b can then be guided, for example, from one space to the next. The longer inner pipe can also be bent several times, although sections where it is surrounded by an outer pipe should be straight.

[0030] In the Figure 2a and 2b A further preferred embodiment of a double-pipe heat exchanger according to the invention is shown, namely an intermediate part 240. The intermediate part 240 can in particular correspond to the intermediate part 140 according to Figure 1 correspond. This shows Figure 2a a cross-sectional view perpendicular to the longitudinal axis L and Figure 2b shows a perspective view.

[0031] The intermediate part 240 has a base body 242 which has a through-opening 246, e.g. a bore, along the longitudinal axis L through which the inner tube is guided, as e.g. in Figure 1As shown, the intermediate piece 240 also has lamellae 244 on an outer surface of the base body 242, which run at least substantially parallel to the longitudinal axis L and are radially oriented to the longitudinal axis. The lamellae 244 can, for example, be arranged evenly distributed around the circumference. The thickness or width b of the lamellae 244 in the circumferential direction can be selected as required.

[0032] The number of lamellae in this example is 24, but this can also be chosen according to requirements. The lamellae can be formed integrally with the base body. For this purpose, suitable areas can be milled out of a solid cylinder, for example, to form the lamellae. However, it is also conceivable to attach the lamellae to the base body, for example, by welding.

[0033] Furthermore, the base body 242 has a gap 248 that runs at least substantially parallel to the longitudinal axis L and is radially oriented to the longitudinal axis L, and that extends radially outward from the through-opening 246 through the base body 242. By way of example, the base body 242 has another gap 248 that runs at least substantially parallel to the longitudinal axis L and is radially oriented to the longitudinal axis L, and that extends radially outward from the through-opening 242 through only a portion, e.g., half the thickness, of the base body, and that is oriented at least substantially parallel to the gap 248. The further gap 250 can, for example, be considered a continuation of the gap 248.

[0034] When manufacturing the intermediate piece, the through opening 246 can be created, for example, as a bore in the base body 242, the gap 248 and the further gap 250 can then be introduced, for example, by a cut in the radial direction into the base body 242.

[0035] Furthermore, the base body 242 has, for example, three through holes 252 for screws 260 as clamping means. The through holes 252 extend, as shown in particular in Figure 2 a can be seen across the gap 248. The screws 260 can be inserted into the respective through holes 252 and, after the inner tube has been inserted into the through hole 246, screwed in to clamp the base body 242 or the intermediate piece 240 to the inner tube. Screws with nuts can be used, for example; it is also conceivable that some of the through holes have a corresponding thread.

[0036] As in the Figure 2a , 2bAs can also be seen, the base body 242 can be shaped accordingly in the area of ​​the through holes, e.g. by suitable recesses, in order to be able to attach or insert the screws or clamping devices in a suitable manner. An example of such a recess 254 is shown in Figure 2a shown.

[0037] In Figure 2a The figures show a diameter d1 of the through-opening 246, a diameter d2 of the base body 242, and a diameter d3 of the intermediate piece 240 including the fins 244. The ratio of d2 to d1 can be, for example, between 1.5 and 10, particularly between 2 and 5. The ratio of d3 to d2 can be, for example, between 1.1 and 2, particularly between 1.1 and 1.5. However, specific values ​​can be chosen depending on requirements and desired heat transfer, as already mentioned.

[0038] The length of the intermediate piece along the longitudinal axis L can also be chosen as required, but, for example, a length that is slightly shorter than the gap 130 formed by the outer tube (see below) is recommended. Figure 1 ) may be expedient. The inventive system 100 is shown in a preferred embodiment, by means of which a method according to the invention can also be carried out. This is a simplified process scheme. In particular, a specific example of a system 100 designed as a hydrogen filling station with an ionic compressor as a compression device 130 and a filling system 140 is shown. The system 100 serves for the simultaneous refueling of a large number of vehicles with hydrogen, although only one vehicle 150 is shown by way of example.

[0039] In Figure 3A hydrogen filling station 300 according to the invention is schematically depicted in a preferred embodiment. The hydrogen filling station 300 includes, by way of example, a storage system 310 for cryogenic hydrogen, as well as a dispenser or dispensing device 330 to which a vehicle 340 can be connected. The cryogenic hydrogen a is to be conveyed from the storage system 310 to the dispenser 330 and from there to the vehicle 340 or its tank.

[0040] This typically requires heating the cryogenic hydrogen a, for which the hydrogen filling station 300 can, for example, have a double-pipe heat exchanger 320 through which the cryogenic hydrogen a is passed to heat it. The double-pipe heat exchanger 320 can be, for example, the one described in Figure 1 The double-pipe heat exchanger shown is being considered. This allows for efficient and cost-effective operation of the hydrogen filling station 300.

Claims

1. Double-tube heat exchanger (100, 320) for heating a cryogenic fluid (a), in particular cryogenic hydrogen, comprising an outer tube (120) and an inner tube (110) arranged within the outer tube (120), wherein the inner tube (110) is designed for a flow of the cryogenic fluid (a), and wherein an intermediate space (130) between the inner tube (110) and the outer tube (120) is designed for a flow of a heat exchange medium (b), wherein the double-tube heat exchanger (100) further comprises an intermediate piece (140, 240) which surrounds the inner tube (110) and is arranged in the intermediate space (130), wherein the intermediate piece (140, 240) has an at least substantially cylindrical base body (242) with a longitudinal axis (L), wherein the base body (242) along the longitudinal axis (L) has a through-opening (246) through which the inner tube (110) is guided, wherein the intermediate piece (140,240) has on an outer side of the base body (242) slats (244) which run at least substantially parallel to the longitudinal axis (L) and are aligned radially to the longitudinal axis (L), and wherein the intermediate piece (140, 240) is clamped onto the inner tube (110).

2. Double-pipe heat exchanger (100, 320) according to claim 1, wherein the base body (242) has a gap (248) which runs at least substantially parallel to the longitudinal axis and is aligned radially to the longitudinal axis, and which extends in the radial direction from the through-opening outwards through the base body.

3. Double-pipe heat exchanger (100, 320) according to claim 2, wherein the intermediate piece (140, 240) has one or more clamping means (260), in particular screws, by means of which the base body is clamped in the region of the gap, so that the intermediate piece is clamped onto the inner pipe.

4. Double-pipe heat exchanger (100, 320) according to claim 3, wherein the base body (242) has one or more through-holes (252) for the clamping means, wherein the one or more through-holes extend across the gap.

5. Double-pipe heat exchanger (100, 320) according to one of claims 2 to 4, wherein the base body (242) has a further gap (250) which runs at least substantially parallel to the longitudinal axis and is aligned radially to the longitudinal axis, and which extends in the radial direction from the through-opening outwards through only a part of the base body, and which is aligned at least substantially parallel to the gap.

6. Double-pipe heat exchanger (100, 320) according to one of the preceding claims, wherein the fins (244) are formed integrally with the base body (242).

7. Double-pipe heat exchanger (100, 320) according to one of the preceding claims, wherein a ratio of a diameter (d2) of the base body to a diameter (d1) of the through-opening, in each case in a direction perpendicular to the longitudinal axis, is between 1.5 and 10, in particular between 2 and 5.

8. Double-pipe heat exchanger (100, 320) according to one of the preceding claims, wherein a ratio of a diameter (d3) of the intermediate piece including the fins to a diameter (d2) of the base body, in each case in a direction perpendicular to the longitudinal axis, is between 1.1 and 2, in particular between 1.1 and 1.

5.

9. Double-pipe heat exchanger (100, 320) according to one of the preceding claims, wherein the inner pipe (110) is designed for at least PN 500, in particular at least PN 900.

10. Double-pipe heat exchanger (100) according to one of the preceding claims, wherein the fins and / or the base body comprise stainless steel, in particular are made of stainless steel 11. A method for producing a double-tube heat exchanger (100, 320) for heating a cryogenic fluid (a), in particular cryogenic hydrogen, wherein the double-tube heat exchanger has an outer tube (120) and an inner tube (110) arranged within the outer tube, wherein the inner tube is provided for a flow of the cryogenic fluid, and wherein a gap is provided between the inner tube and the outer tube for a flow of a heat exchange medium, wherein an intermediate piece (140, 240) is provided which surrounds the inner tube and is arranged in the gap, wherein the intermediate piece (140, 240) has an at least substantially tubular base body with a longitudinal axis, wherein the base body has a through-opening along the longitudinal axis through which the inner tube is guided, wherein the intermediate piece has fins on an outer side of the base body,which run at least substantially parallel to the longitudinal axis and are aligned radially to the longitudinal axis, and wherein the intermediate piece is clamped onto the inner tube., 12. Method according to claim 11, for producing a double-pipe heat exchanger (100, 320) according to one of claims 1 to 10.

13. Use of a double-pipe heat exchanger (100, 320) according to one of claims 1 to 10 for or in a hydrogen filling station.

14. Hydrogen filling station (300) for refueling a vehicle (340) with hydrogen (a), comprising a double-pipe heat exchanger (100, 320) according to one of claims 1 to 10 for heating the hydrogen.

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