HEAT EXCHANGER MODULE, METHOD FOR MANUFACTURING SUCH A MODULE AND TUBULAR HEAT EXCHANGER COMPRISING SUCH MODULES

Abstract

A heat exchanger module comprises several U-tubes for a first fluid flow, the U-tubes having two straight sections connected by a U-shaped portion. Inlet ends of the several U-tubes are connected with an inlet collector tube and outlet ends of the several U-tubes are connected with an outlet collector tube. The two straight sections of the U-tubes have a different length such that a longitudinal axis of the inlet collector tube and a longitudinal axis of the outlet collector tube are arranged at different heights with respect to a height of the heat exchanger module. Also provided is a method for manufacturing the heat exchanger modules and a tubular heat exchanger comprising a plurality of heat exchanger modules.

Claims

1. A heat exchanger module comprising several U-tubes for a first fluid flow, the U-tubes having two straight sections connected by a U-shaped portion, wherein inlet ends of the several U-tubes are connected with an inlet collector tube and outlet ends of the several U-tubes are connected with an outlet collector tube, wherein the two straight sections of the U-tubes have a different length such that a longitudinal axis of the inlet collector tube and a longitudinal axis of the outlet collector tube are arranged at different heights with respect to a height of the heat exchanger module.

2. The heat exchanger module according to claim 1, wherein the inlet ends or the outlet ends of the U-tubes are connected with the tube wall of the respective inlet or outlet collector tube over an entire wall thickness of the respective tube wall.

3. The heat exchanger module according to claim 1, wherein at least one of the inlet ends of the U-tubes or the outlet ends of the U-tubes comprise a brazed joint with the respective inlet or outlet collector tube.

4. The heat exchanger module according to claim 1, wherein an end of the inlet collector tube or an end of the outlet collector tube, preferably, an end of the inlet collector tube and an end of the outlet collector tube, is closed.

5. The heat exchanger module according to claim 1, wherein the several U-tubes are arranged in a regular array.

6. The heat exchanger module according to claim 5, wherein the inlet ends of the several U-tubes and the outlet ends of the several U-tubes are arranged in rows.

7. The heat exchanger module according to claim 6, wherein the inlet ends and the outlet ends of the several U-tubes are each arranged in two to eight rows, preferably, in four to six rows.

8. The heat exchanger module according to claim 1, further comprising fins arranged on an outside of the U-shaped tubes for guiding a second fluid flow in the direction of the fins along the outside of the heat exchanger module.

9. The heat exchanger module manufactured according to the method of claim 10.

10. A method for manufacturing a heat exchanger module according to claim 1, the method comprising: providing a plurality of U-tubes; providing an inlet collector tube and an outlet collector tube with through passages in a tube wall of the inlet collector tube and with through passages in a tube wall of the outlet collector tube; accommodating inlet ends and outlet ends of the U-tubes in the through passages in the respective tube walls of the inlet collector tube and the outlet collector tube; connecting the inlet ends of the U-tubes to the inlet collector tube and connecting the outlet ends of the U-tubes to the outlet collector tube in a fluid tight manner, thereby forming a heat exchanger module.

11. The method according to claim 10, further comprising applying brazing paste in the region of the through passages; heating the heat exchanger module above a melting temperature of the brazing paste, letting the brazing paste enter the through passages, thereby forming a brazed joint between the ends of the U-tubes and the respective collector tubes.

12. The method according to claim 11, therein using a nickel-based brazing paste.

13. The method according to claim 11, therein heating the heat exchanger module above 1000 degree C for forming the brazed joint.

14. The method according to claim 11, wherein the heating the heat exchanger module comprises heating the heat exchanger module in a vacuum furnace.

15. The method according to claim 10, comprising drilling or laser cutting the through passages in the tube walls of the inlet collector tube and the outlet collector tube.

16. A tubular heat exchanger comprising a housing with a first fluid inlet and a second fluid inlet and a first fluid outlet and a second fluid outlet, wherein a plurality of heat exchanger modules according to claim 1 are arranged in the housing, and wherein the plurality of heat exchanger modules are connected with each other.

17. The tubular heat exchanger according to claim 16, wherein the plurality of heat exchanger modules is arranged in the housing in two or more parallel rows, and wherein the first fluid inlet comprises a flow splitter, which flow splitter is connected with an inlet collector tube of a first heat exchanger module in each row of heat exchanger modules.

18. The tubular heat exchanger according to claim 16, wherein the housing is elongate having a longitudinal axis and wherein longitudinal axes of straight sections of U-tubes of the heat exchanger modules are arranged perpendicular to the longitudinal axis of the housing.

19. (canceled)

Description

[0063] The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein:

[0064] FIG. 1 shows a perspective view of a heat exchanger module;

[0065] FIG. 2 a partial view of the heat exchanger module of FIG. 1;

[0066] FIG. 3 two combined heat exchanger modules;

[0067] FIG. 4 shows a perspective view of a tubular heat exchanger;

[0068] FIGS. 5,6 are a longitudinal cross-sectional view (FIG. 5) and a transverse cross-sectional view (FIG. 6) of the tubular heat exchanger of FIG. 4;

[0069] FIG. 7 shows a series of heat exchanger modules.

[0070] In the drawings, the same reference signs are used for the same or similar elements.

[0071] FIG. 1 shows a heat exchanger module 1 comprising an inlet collector tube 20 and an outlet collector tube 21. Both collector tubes 20, 21 have a circular cross section and an exemplary tube wall 25 thickness of about 8 mm to 20 mm. In a preferred embodiment, an outer diameter of the collector tubes is 125 mm and an inner diameter is 100 mm inner diameter, thus the tube wall thickness amounts to 12.5 mm.

[0072] The inlet collector tube 20 and outlet collector tube 21 comprise an open end 23 facing to the front in FIG. 1. The inlet and outlet collector tubes 20,21 may comprise a closed opposite end 22 (not shown) if used as single module or possibly in serial arrangement with other heat exchanger modules. In other embodiments, the opposite end 22 may be open and for example attached to, in particular welded, to another inlet collector tube of another heat exchanger module. A pressurized first fluid may then transfer into the adjacent inlet collector tube and adjacent module.

[0073] As may be seen in more detail in FIG. 2 showing a partial view of the heat exchanger module of FIG. 1, four times 40 U-tubes 30 are fluidly connected with the interior of the collector tubes 20,21 via the tube walls 25 of the collector tubes 20,21.

[0074] The collector tubes 20,21 each comprise four rows of 40 through holes 24 in their tube walls 25. All four rows are arranged in a lower half of the collector tubes. The four rows are arranged parallel to each other and along the length of the collector tubes 20,21 parallel to the longitudinal axis of the collector tubes. Through holes 24 in neighbouring rows are displaced by half the distance between through holes in a same row. This positioning allows for a nested arrangement of U-tubes with a distance between through holes of a few millimeter, for example 0.5 millimeter to 10 millimeter, and thus a very compact U-tube arrangement. An exemplary diameter of a through hole is 13 millimeter having a shortest distance to neighbouring through holes of 2 millimeter.

[0075] The U-tubes 30 comprise two straight sections 31,35 and a U-shaped portion 32 connecting the two straight sections to form the U-tubes 30. The inlet ends 33 of the U-tubes and the outlet ends 34 of the U-tubes are arranged in the through holes 24 and are brazed to the tube walls 25.

[0076] The through holes 24 are preferably drill holes or laser-cut holes, and drilled or cut into the tube walls 25 before inserting the ends 33,34 of the U-tubes 30 into the through holes 24.

[0077] Preferably, the inlet ends and outlet ends 33,34 of the U-tubes form a brazed joint with the tube walls 25 of the inlet and outlet collectors 20,21. This is preferably realized by vacuum brazing or diffusion bonding.

[0078] A length of a joint extends over an entire wall thickness of the collector tubes 20,21, for example if the inlet ends 33 or outlet ends 34 are arranged exactly perpendicular to the circumference of the tube walls 25. In more externally arranged U-tubes 30 and more internally arranged U-tubes 30 joints may be manufactured that ere even longer than the tube wall thickness.

[0079] The straight sections 31,35 of a U-tube have a different length. In FIG. 1 all inlet straight sections 31 of all U-tubes are longer than their respective outlet straight sections 35. By this, the inlet collector tube 20 in FIG. 1 may be arranged at a different height than the outlet collector tube 21 when seen over a height of the heat exchanger module 1. This allows to place inlet and outlet collector tubes 20,21 closer together in a width direction of the module and make the heat exchanger module 1 very compact. In the embodiment shown in FIG. 1 a length of the inlet straight sections 31 is, for example, between 80 cm to 90 cm, while a length of the outlet straight sections 35 is, for example, between 70 cm to 80 cm with an outer diameter of the U-tubes in a range between 10 mm and 15 mm. In another embodiment, a length of the inlet straight sections 31 is, for example, between 2 m and 2.5 m, while a length of the outlet straight sections 35 is, for example, between 1.8 m and 2.3 m with an outer diameter of the U-tubes in a range between 20 mm and 30 mm.

[0080] In FIG. 1 it may be seen that U-tubes in an interior portion of the heat exchanger module 1 are smaller in height and width than U-tubes in an exterior outer portion of the heat exchanger module 1. The height of a U-tube is mainly defined by a length of the straight sections 31,35 of a U-tube. A width of a U-tube is defined by the size of the U-shaped portion.

[0081] Five longitudinal fins 4 in the form of strips are arranged on the outside of the U-tubes. The fins 4 extend parallel to the longitudinal axis of the collector tubes 20,21 and are provided for guiding a second fluid flow, which second fluid flow flows around the heat exchanger module 1. The second fluid flow absorbs heat from a first highly pressurized fluid flow flowing in and through the collector tubes 20,21 and U-tubes 30. The preferably equidistantly arranged fins 4 separate the outsides of the U-tubes into four to five sections, each section intended to guide about 25 percent or 12.5 percent of the total flow of the second fluid passing that side of the heat exchanger module 1.

[0082] In the example of FIG. 1 and FIG. 2, the fins on each of the four sides of the heat exchanger module 1 are embodied as plate of a sheet material, for example steel plate. One plate forms guiding fins on the outside and in the inside of the heat exchanger module 1, wherein these fins are connected and preferably made in one piece. The plate extends in between the straight sections 31,35 of the U-tubes 30.

[0083] The module as shown in FIGS. 1 and 2 may be vacuum brazed in a vacuum furnace. Exemplary sizes of a vacuum furnace are from 250 mm up to 2000 mm (diameter or extension), for example 700×650×300, 600×900×600, 1200×2000×1200, or (diameter)250×340, (diameter)1500×1500. Preferred materials of a vacuum furnace are graphite or molybdenum. Preferred materials for brazing are Nickel or Chromium-Nickel containing brazing pastes, which require furnace temperatures above 1000° C., for example 1100 to 1200° C. Typical vacuum in a vacuum furnace is 10.sup.-3 to 10.sup.-4 mbar.

[0084] FIG. 3 shows two heat exchanger modules 1 of FIG. 1 aligned and connected together. The inlet and outlet collector tubes 20,21 are fixed to each other, for example by welding.

[0085] A first fluid flow 90 is indicated by arrows 900 for the first fluid flow within the heat exchanger modules 1. The first fluid flow 90 is guided into the inlet collector tubes 20 from both sides. There, the first fluid flow flows perpendicular to the longitudinal axis of the inlet collector tubes 20 through the U-tubes 30 of the heat exchanger modules 1. Arrows 900 in dotted bold indicate an inlet flow in the U-tubes and in bold indicate an outlet flow in the U-tubes 30.

[0086] It is also possible to guide the fluid from one side only into the inlet collector tubes 20 and to collect all first fluid from one outlet collector tube 21 only.

[0087] The collector tubes and U-tubes are made from a suitable metal, preferably, steel, more preferably stainless steel.

[0088] FIG. 4 shows a tubular heat exchanger 8. In the housing 5 two rows of 12 heat exchanger modules 1, for example the heat exchanger modules according to FIG. 1 are arranged in parallel (only front row visible), for example in a coupled arrangement as shown in FIG. 3. The open ends 23 of the collector tubes 20,21 are connected with open ends of neighbouring collector tubes. Therein, an outlet collector tube 21 is connected with an inlet collector tube 20 of the neighbouring heat exchanger module 1 via connectors (not shown).

[0089] The housing 5 comprises a first inlet 51 and a first outlet 52 for a first high pressurized fluid 90 to enter the housing at the first inlet 51, pass the heat exchanger modules 1 through the collector tubes 20,21 and U-tubes 30 and leave the housing via first outlet 52.

[0090] The housing 5 comprises a second inlet 53 and a second outlet 54 for a second not or only low pressurized fluid 91 to enter the housing at the second inlet 53, pass the heat exchanger modules 1 on their outside and leave the housing via second outlet 52.

[0091] The housing 5 has a tubular shape with a tubular side wall 56 having a circular cross section and slightly convex shaped end walls 57. The first inlet 51 and second outlet 54 are arranged in one of the side walls 57 and the second inlet 53 and first outlet 52 are arranged in the opposite side wall 56. By this the first fluid flow 90 and the second fluid flow 91 pass the tubular heat exchanger in a main co-flow manner but in counter direction.

[0092] The second inlet and second outlet 53,54 are arranged in the center of the side walls 57. The first inlet and first outlet 51,52 are arranged displaced to a lateral side of the housing 5.

[0093] The fluid flow within the housing 5 is indicated by arrows 910 for the second fluid flow 91. The second fluid flow 91 flows parallel to the longitudinal axis of the housing 5 essentially in a linear manner from the second inlet 53 to the second outlet 54 of the housing 5.

[0094] The fluid flow within the housing 5 is indicated by arrows 900 for the first fluid flow 90. The first fluid flow 90 is guided into the inlet collector tube 20 of a first heat exchanger module in a row. There, the first fluid flow flows perpendicular to the longitudinal axis of the housing 5 through the U-tubes 30 of the heat exchanger modules 1. In the last heat exchanger module 1 in a row, the first fluid flow 90 is collected in the outlet collector tube 21 and leaves the heat exchanger via first outlet 52. Again, arrows 900 in dotted bold indicate an inlet flow in the U-tubes and in bold indicate an outlet flow in the U-tubes 30.

[0095] On, the front side of the heat exchanger module assembly five fins 4 may be seen extending in the longitudinal direction of the housing 5 and parallel to the second flow direction 910. The fins 4 divide the space along the height of the U-tubes 30 in sections 40. The second flow 91 remains in these sections 40 and a flow deviation into the direction of the collector tubes 20,21 or the U-shaped portions 32 of the U-tubes may be limited or prevented.

[0096] FIG. 5 and FIG. 6 show a longitudinal and a transversal cross-sectional view of the heat exchanger 8 of FIG. 4.

[0097] Two times twelve modules, for example as in FIGS. 1, or 12 combined modules as shown in FIG. 3, are arranged in series in the housing 8. The housing 5 has a length 800 of about 3040 mm (3640 mm including first inlet 51 and outlet 52) and a diameter of about 1700 mm.

[0098] The first inlet 52 and first outlet 51 are arranged in one line and on a same height with respect to a height of the heat exchanger and parallel and distanced to the second inlet and outlet 53,54. The second inlet 53 and second outlet 54 are arranged on the central axis of the housing 5.

[0099] The first inlet flow 90 entering the heat each exchanger 8 by the first inlet 51 is distributed via flow splitter 55 to the inlet collector tube 20 of the first heat exchanger modules 1 of each of the two rows of modules or to the two opposite ends of combined inlet collector tubes, respectively.

[0100] An inner diameter 510 of first inlet and outlet 51,52 is about 100 mm.

[0101] An outer diameter 540 of second inlet and outlet 53,54 is about 300 mm.

[0102] In the transverse view in FIG. 6, the two rows of modules 1 are depicted one above the other. Neighbouring inlet collector tubes 20 and outlet collector tubes 21 are connected with each other by respective end connectors 7 connecting their open ends 23.

[0103] In FIG. 7 a series of four heat exchanger modules 1 is shown. The modules 1 have a similar set-up as the modules of FIG. 1. However, in the example of FIG. 7 adjacent modules 1 are flipped such that neighbouring straight sections 31, 35 of adjacently arranged modules 1 have a same length.

[0104] Accordingly, adjacent modules 1 have a long and a short inlet straight section 31 and a long and a short outlet straight section 35.

[0105] In FIG. 7, an inlet collector 20 is not connected with its adjacent outlet collector 21 through an end connector 7 as shown in FIG. 6. The collector tubes 20,21 comprise four radially, in the example shown in FIG. 6 horizontally, arranged interface tubes 28. Each interface tube 28 of a collector 20,21 is connected to an interface tube 28 of an adjacent collector 21,20. The connection of interface tubes 28 to each other may be performed by welding or brazing, preferably by welding.

[0106] The interface tubes 28 may be connected with the respective collector tube 20,21 in a same manner as the U-tubes are connected to the collectors 20,21. Thus, preferably, through holes are provided in the tube walls of the collector tubes 20,21 and the interface tubes 28 are inserted into the through holes. A brazing joint between interface tube 28 and collector tube wall is preferably, realized in a same manufacturing step than the brazing of the ends of the U-tubes with the collector walls.

[0107] The modules 1 preferably comprise inlet collectors 20 and outlet collectors 21 having both ends closed.

[0108] The modules in the embodiment shown in FIG. 7 use longer or shorter inlet sections of the U-tubes in alternating succession. The modules 1 are identical, but every-other module of the series is flipped.

[0109] With radially arranged connector tubes 28, equidistantly arranged over a length of a collector tube 20,21, a fluid flow is homogeneously distributed over the length of the collector tubes 20,21 and thus over the length of the heat exchanger module 1.

[0110] An example of a tubular heat exchanger comprises 24 heat exchanger modules arranged in two rows à 12 heat exchanger modules, with four times 40 U-tubes per heat exchanger module, preferably carbon dioxide (CO.sub.2) as pressurized fluid with a pressure between 85 bar and 280 bar and a mass flow of 22.5 kg/s.

[0111] In an example, a first fluid is supercritical CO.sub.2 a pressure between 73 to 90 bar and a temperature between 31 degree and 70 degree Celsius.

[0112] Examples of U-tubes are: [0113] a total U-tube length of 1.55 meter, with each straight section extending over 0.75 meter and a diameter between 10 mm to 15 mm; [0114] Shortest distance between passages in collector tube wall for ends of U-tubes: 2 mm with a diameter of a U-tube of 13 mm; [0115] Outer diameter of U-tube 25 mm; inlet straight sections between 2 m and 2.5 m and between 1.8 m and 2.3 m for the outlet straight sections.