Double-tube heat exchanger, manufacturing method, use, and hydrogen fueling station

Abstract

The invention relates to a double-tube heat exchanger for heating a cryogenic fluid, in particular cryogenic hydrogen, said heat exchanger comprising an outer tube and an inner tube located inside the outer tube, the inner tube being designed to allow the flow of the cryogenic fluid, and a gap between the inner tube and the outer tube being designed to allow the flow of a heat exchange medium, the double-tube heat exchanger also comprising an intermediate piece (240) which surrounds the inner tube and is positioned in the gap, the intermediate piece (240) having an at least substantially cylindrical main body (242) with a longitudinal axis (L), the main body (242) having a through-opening (246) along the longitudinal axis (L), through which through-opening the inner tube is guided, the intermediate piece (240) having fins (244) on an outer side of the main body (242) which extend at least substantially parallel to the longitudinal axis (L) and are oriented radially with respect to the longitudinal axis (L), and the intermediate piece (240) being clamped onto the inner tube.

Description

[0001] Description

[0002] Double-pipe heat exchanger, manufacturing process, use and hydrogen filling station

[0003] The invention relates to a double-tube heat exchanger for heating a cryogenic fluid, in particular cryogenic hydrogen, a method for producing such a double-tube heat exchanger, a use of such a double-tube heat exchanger, and a hydrogen filling station with such a double-tube heat exchanger.

[0004] 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 refueling station, where hydrogen is initially in liquid form at approximately -253°C and then needs to be heated before refueling a vehicle.

[0005] Heat exchangers (or heat transfer devices) can be used to heat fluids in general. One type of heat exchanger is a double-tube heat exchanger, in which an inner tube is surrounded by an outer tube. For example, the fluid to be heated can be carried in the inner tube, while the heat exchange medium can be contained in a space between the inner and outer tubes.

[0006] However, the use of double-pipe heat exchangers in cryogenic applications, particularly cryogenic high-pressure applications, presents various problems. Due to the high pressure (up to PN 1000, i.e., 1000 bar at room temperature), the wall thickness of the inner pipe (in which, for example, the hydrogen is carried) must be very thick, which leads to high thermal resistance and high requirements and costs for production during manufacture and connection of the pipes (especially welds). Due to the very low cryogenic temperatures in the inner pipe (down to -253 °C for cryogenic hydrogen), severe icing of gaseous or liquid heat transfer fluids occurs in the annular space (interspace) of the double-pipe. This can or often will lead to pipe blockage and an increase in pressure drop, as well as a reduction in heat transfer between the media.

[0007] Another type of heat exchanger is a medium-to-air heat exchanger, or in this specific case, a hydrogen-to-air heat exchanger. However, various problems can arise here too. Due to the low heat transfer coefficient, very large dimensions are generally unacceptable for applications such as hydrogen filling stations. Continuous operation is generally not possible due to icing, which leads to the use of redundant heat exchangers for recuperative operation. Vapor clouds on the heat exchangers are generally also unacceptable for applications such as hydrogen filling stations. In addition, at low hydrogen temperatures, a significant amount of energy is lost to the air and cannot be used in the downstream filling station process. This leads to high electricity costs and thus reduces the overall efficiency of hydrogen filling stations.

[0008] Against this background, the task arises of heating a cryogenic fluid, especially cryogenic hydrogen, in the most cost- and energy-efficient way possible.

[0009] Disclosure of the invention

[0010] This object is achieved by a double-pipe heat exchanger, a method for producing a double-pipe heat exchanger, a use of a double-pipe heat exchanger, and a hydrogen refueling station having the features of the independent patent claims. Preferred embodiments are the subject of the dependent patent claims and the following description.

[0011] Advantages of the invention

[0012] The invention relates to the heating of a cryogenic fluid, in particular cryogenic hydrogen, using a heat exchanger, as well as the specific application thereof, in particular in hydrogen filling stations. 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 within the outer tube. Typically, the inner tube is arranged concentrically within the outer tube. The inner tube is configured for the flow of the cryogenic fluid, while a space between the inner tube and the outer tube is configured for the flow of a heat exchange medium.

[0013] As is typical for a double-tube heat exchanger, it can have an inlet for the cryogenic fluid, which is connected to the inner tube, and an outlet for the cryogenic fluid, which is also connected to the inner tube. Furthermore, the double-tube heat exchanger can have an inlet for the heat exchange medium, which is connected to the intermediate space, and an outlet for the heat exchange medium, which is also connected to the intermediate space.

[0014] Furthermore, the double-pipe heat exchanger has an intermediate piece (or a so-called inner part) that surrounds the inner pipe and is arranged in the intermediate space. The intermediate piece has an at least substantially cylindrical base body with a longitudinal axis, wherein the base body has a through-opening along the longitudinal axis through which the inner pipe is guided. On an outer side 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 aligned radially to the longitudinal axis. Furthermore, the intermediate piece is clamped onto the inner pipe.

[0015] The intermediate piece allows for efficient and cost-effective heating of a cryogenic fluid using a double-pipe heat exchanger, as the intermediate piece enables efficient heat transfer between the cryogenic fluid to be heated and the heat exchange medium. Because the intermediate piece is clamped onto the inner pipe and not welded to it, the double-pipe heat exchanger can also be used to heat a cryogenic fluid at high pressures, e.g., pressures of more than 500 bar or even more than 900 bar (each calculated at room temperature). The double-pipe heat exchanger, or at least the inner pipe, can therefore be designed for PN 500 or PN 900 or even PN 1000 (a pressure resistance of 500 bar, 900 bar, or 1000 bar, respectively, each at room temperature). The clamping ensures a secure and good thermal connection between the inner pipe and the intermediate piece.

[0016] 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.

[0017] It is advisable for the fins to be formed integrally with the base body. This allows for a stable and robust intermediate piece and efficient and good heat transfer between the fins and the base body. Stainless steel is particularly suitable as a material for the fins and / or the base body, meaning the fins and / or the base body can be made of stainless steel or even be made of stainless steel. Stainless steel allows for sufficiently easy processing, has sufficiently good thermal conductivity and heat capacity, and is also suitable for cryogenic temperatures down to -253°C.

[0018] In one embodiment, the base body has a gap 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. The base body is therefore not a full cylindrical shell, but has a cross-section in the shape of a C. 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. The intermediate piece preferably has one or more clamping means, in particular screws, by means of which the base body is clamped in the region of the gap, such 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 orScrews, wherein the one or more through-holes extend across the gap. In the case of screws, the gap can therefore be reduced during clamping, as a result of which the base body is securely clamped to the inner tube. In one embodiment, the base body has a further gap 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. The further gap is aligned at least substantially parallel to the (above-mentioned) gap. This allows for easier and better clamping of the intermediate piece or base body to the inner tube, and thus increases heat transfer even at high pressures of the cryogenic fluid in the inner tube.

[0019] In one embodiment, a ratio of a diameter of the base body to a diameter 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. In one embodiment, a ratio of a diameter of the intermediate piece including the slats to a diameter 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. The concrete values ​​to be selected for these ratios (in particular for the first-mentioned ratio), i.e. a thickness of the base body, can depend on the required thermal resistance in order to prevent freezing. The number of slats or fins as well as the dimensions (i.e. the second-mentioned ratio) can depend on the required heating surface.However, with the ratios mentioned, good efficiency can be achieved even at high pressures, especially for cryogenic fluids such as hydrogen, which need to be heated.

[0020] Longitudinally finned tubes are typically used in applications with viscous fluids. The fins were added to achieve a more compact design. Because the inner part is clamped, it can be used in high-pressure systems.

[0021] The proposed design allows freezing of the heat exchange medium, allowing fluids such as potassium formate and / or glycol to be used as heat exchange media, making the heating process using the double-pipe heat exchanger safer compared to systems using oil as the heat exchange medium. 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 subsequent process step, e.g., to cool hydrogen elsewhere, such as at a hydrogen refueling station. This increases the overall efficiency of the entire system, e.g., the hydrogen refueling station.

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

[0023] Short description of the drawing

[0024] Figure 1 shows schematically a double-pipe heat exchanger according to the invention in a preferred embodiment.

[0025] Figure 2a shows schematically a part of a double-pipe heat exchanger according to the invention in a further preferred embodiment.

[0026] Figure 2b shows schematically the part of the double-pipe heat exchanger according to the invention from Figure 2a in another view.

[0027] Figure 3 shows schematically a hydrogen filling station according to the invention in a preferred embodiment.

[0028] Detailed description of the drawing

[0029] Figure 1 schematically shows a sectional view of a double-pipe heat exchanger 100 according to the invention in a preferred embodiment, which 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 a conventional double-pipe heat exchanger,

[0030] The double-pipe heat exchanger 100 has an inner pipe 110 through which the cryogenic fluid a to be heated is guided or passed. For this purpose, the cryogenic fluid a is supplied via an inlet opening 112 and then guided through the inner pipe 110 to an outlet opening 114, through which the cryogenic fluid a is guided out of the double-pipe heat exchanger 100. The inlet opening 112 and the outlet opening 114 can each be formed, for example, as a flange or as part of a flange.

[0031] The double-pipe heat exchanger 100 further comprises an outer pipe 120, wherein the inner pipe 110 is arranged, in particular concentrically, within the outer pipe 120. By way of example, a longitudinal axis L is shown, with the inner pipe 110 and the outer pipe 120 being arranged concentrically. The outer pipe 120 can, for example, have a flange 126 or 128 at each end, through which the inner pipe 110 is guided.

[0032] An intermediate space 130 between the inner tube 110 and the outer tube 120 is configured 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 intermediate space 130, and an outlet opening 124 through which the heat exchange medium b can be discharged from the intermediate space 130. For example, the inlet opening 122 and the outlet opening 124 are arranged in the radial direction (relative to the longitudinal axis L); likewise, the inlet opening 122 and / or the outlet opening 124 can be arranged in one of the flanges 126, 128, and thus in particular also in the longitudinal direction.

[0033] An intermediate piece 140 is now arranged in the intermediate space 130. The intermediate piece 140 surrounds the inner tube 110 and has an at least substantially cylindrical base body with a longitudinal axis, wherein the longitudinal axis can correspond to the longitudinal axis L of the double-pipe heat exchanger 100.

[0034] The double-pipe heat exchanger 100 shown here is intended only as an example to explain the invention. A double-pipe heat exchanger can also be designed differently. For example, there can be several separate outer pipes that surround a—then longer—inner pipe at a distance from one another, thus forming several intermediate spaces, each of which has an intermediate piece arranged therein. The heat exchange medium b can then, for example, be conducted from one intermediate space to the next. The longer inner pipe can then also be bent several times, although sections where it is surrounded by an outer pipe should be straight.

[0035] Figures 2a and 2b show a part of a double-pipe heat exchanger according to the invention in a further preferred embodiment, namely an intermediate part 240. The intermediate part 240 can in particular correspond to the intermediate part 140 according to Figure 1. Figure 2a shows a cross-sectional view perpendicular to the longitudinal axis L, and Figure 2b shows a perspective view.

[0036] 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 shown, for example, in Figure 1. Furthermore, 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 aligned radially to the longitudinal axis. The fins 244 can, for example, be arranged evenly distributed around the circumference. A thickness or width b of the fins 244 in the circumferential direction can be selected as required.

[0037] The number of slats 244 is 24 here, for example, but can also be selected as needed. The slats 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 slats. However, it is also conceivable to attach the slats to the base body, e.g., by welding.

[0038] In addition, the base body 242 has a gap 248 which runs at least substantially parallel to the longitudinal axis L and is aligned radially to the longitudinal axis L, and which extends in the radial direction from the through-opening 246 outwards through the base body 242. By way of example, the base body 242 has a further gap 248 which runs at least substantially parallel to the longitudinal axis L and is aligned radially to the longitudinal axis L, and which extends in the radial direction from the through-opening 242 outwards through only a part, e.g. half the thickness, of the base body, and which is aligned at least substantially parallel to the gap 248. The further gap 250 can, for example, be regarded as a continuation of the gap 248. During the production of the intermediate piece, the through-opening 246 can, for example, be created as a bore in the base body 242, the gap 248 and the further gap 250 can then, for example,by a cut in the radial direction into the base body 242.

[0039] Furthermore, the base body 242 has, for example, three through-holes 252 for screws 260 as clamping means. The through-holes 252 extend, as can be seen particularly in Figure 2a, beyond 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. For example, screws with nuts can be used; it is also conceivable for some of the through-holes to each have a corresponding thread.

[0040] As can also be seen in Figures 2a and 2b, the base body 242 can be shaped accordingly in the area of ​​the through holes, e.g., by means of suitable recesses, in order to be able to attach or insert the screws or clamping means in a suitable manner. An example of such a recess 254 is shown in Figure 2a.

[0041] Figure 2a shows 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, in particular between 2 and 5. The ratio of d3 to d2 can be, for example, between 1.1 and 2, in particular between 1.1 and 1.5. Specific values ​​can, however, be selected depending on requirements and the desired heat transfer, as already mentioned.

[0042] The length of the intermediate piece along the longitudinal axis L can also be selected as required, although a length that is somewhat shorter than the intermediate space 130 formed by the outer tube (cf. Figure 1) can be expedient, for example. The figure shows a preferred embodiment of the system 100 according to the invention, by means of which a method according to the invention can also be carried out. This is a simplified process diagram. In particular, a concrete example of a system 100 designed as a hydrogen filling station with an ionic compressor as compression device 130 and a filling system 140 is shown. The system 100 serves to simultaneously fill a large number of vehicles with hydrogen, although only one vehicle 150 is shown as an example.

[0043] Figure 3 schematically illustrates a hydrogen filling station 300 according to the invention in a preferred embodiment. The hydrogen filling station 300 comprises, for example, a storage system 310 for cryogenic hydrogen, as well as a dispenser or supply device 330 to which a vehicle 340 can be connected. The cryogenic hydrogen a is to be transported from the storage system 310 to the dispenser 330 and from there to the vehicle 340 or its tank.

[0044] This typically requires heating of the cryogenic hydrogen a, for which purpose the hydrogen filling station 300 may, for example, have a double-pipe heat exchanger 320 through which the cryogenic hydrogen a is passed in order to heat it. The double-pipe heat exchanger shown in Figure 1, for example, can be considered as the double-pipe heat exchanger 320. This allows for efficient and cost-effective operation of the hydrogen filling station 300.

Claims

Patent 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 an intermediate space 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 intermediate space, 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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