WO2006010435A1

WO2006010435A1 - Heat exchanger, especially a condenser

Info

Publication number: WO2006010435A1
Application number: PCT/EP2005/007182
Authority: WO
Inventors: Herbert Damsohn; Conrad Pfender
Original assignee: Behr Gmbh & Co. Kg
Priority date: 2004-07-23
Filing date: 2005-07-04
Publication date: 2006-02-02
Also published as: DE102004036020A1; EP1774237A1

Abstract

The invention relates to a heat exchanger, especially a condenser (1), for a first vaporous and/or gaseous fluid. Said heat exchanger comprises an inlet-side collecting tank, an outlet-side collecting tank (2, 3), and pipes which connect the two collecting tanks and comprise pipe ends. The first fluid can flow through said pipes and a second gaseous fluid, especially air, can circulate around the same. According to the invention, the pipes are embodied as flat pipes (10) and are produced from a corrosion-resistant material with a high heat conductivity, especially special steel, the collecting tanks (2, 3) are produced from a corrosion-resistant material, especially plastic, and comprise a cover and a pipe bottom, and the pipe ends (11, 12) are held in the pipe bottom (7, 9) in a fixed and tight manner.

Description

Heat exchanger, in particular condenser

The invention relates to a heat exchanger, in particular a Konden¬ capacitor according to the preamble of claim 1.

In fuel cell systems, moist process exhaust air is produced, which is cooled down, producing condensate, inter alia, water and methanol. The cooled process air and the condensate are fed back into the process. The cooling is preferably carried out by ambient air. The process air is corrosive due to the constituents contained in it and is under a relatively low pressure.

Conventional heat exchangers, in particular for motor vehicles, are generally designed for higher pressures and a greater pressure drop on the cooling air side, ie also with higher fan powers. Accordingly, the joining technique is complex, ie, aluminum or stainless steel systems are used whose components such as pipes, ribs, tubesheets, De¬ ckel and manifolds are soldered or welded together. The known systems are too expensive or unsuitable for the abovementioned media and process conditions: conventional stainless steel coolers are usually designed for higher pressures, plastic coolers are not sufficiently powerful owing to their poor heat conductivity, and aluminum coolers are not sufficient, even with corrosion-inhibiting coatings Corro sion resistant. It is therefore an object of the present invention to provide a heat exchanger, in particular condenser of the aforementioned type, which is ei¬ nerseits corrosion resistant to a first medium to be cooled and on the other hand designed for low pressures and high cooling capacity at low production costs. In particular, the heat exchanger should have good condensate drainage properties.

This object is solved by the features of claim 1. Materials and joining technology for the heat exchanger according to the invention are chosen with regard to their function: the collecting boxes including tubesheet are made of plastic and the tubes made of stainless steel - both materials are corrosion resistant. Low wall thicknesses and the formation of the heat transfer surfaces as primary surfaces lead despite a possibly low thermal conductivity of the materials to a low power density. At the same time a sufficient compressive strength of the flat tubes is given, which have a low cooling air side pressure drop as an advantage. The joining technique of the components of the heat exchanger according to the invention is adapted to the low requirements (with regard to pressure resistance and tightness). The tube ends of the flat tubes are tightly and firmly received in openings of the plastic tube bottom.

Further advantageous embodiments of the invention will become apparent from the dependent claims. Advantageously, the compressive strength of the flat tubes, which are inherently unstable, can be enhanced by beads or nubs or widening of the tube ends. In this case, beading as inside or outside cusps as well as continuous or non-continuous longitudinal beads are possible. It is also advantageous that gaps are left for the Kühlluft¬ leadership between the flat tubes, in which no conventional ribs are arranged - thus resulting in a low pressure drop on the air side and a low fan power. Nevertheless, a good cooling effect is achieved due to the long gap between the flat tubes. It is also advantageous if the collecting boxes are made of two parts, namely a lid and a tube sheet joined and sealed together. There are two sealing zones, namely on the one hand between the lid and the tubesheet and on the other hand between the tubes and the tubesheet. Vorteilhafter- example, the sealing of both sealing zones by a sealant, namely a bonding sealant, preferably a two-component silicone or a potting compound, as is commonly used for electronic assemblies done. For this purpose, the pipe ends are inserted into corresponding openings of the tube sheet, with a certain pipe protrusion towards the lid. Then the bottom is poured out with the liquid sealant and the lid is put on. Lid and Rohr¬ soil are bonded by the curing sealant in a circumferential joining area, are thus firmly and tightly connected. The pipe ends are circumferentially surrounded by the curing, but elastically leadable sealing compound, so that a sufficient sealing of the pipes with respect to the tubesheet ensures and leakage of aggressive process air is prevented in the environment. Cover and tube sheet are advantageously made of a polyamide (PA) or polyoxymethylene (POM) as molded parts, ie inexpensive to produce. Alternatively, it can also be advantageous to replace the "liquid" seal, ie the two-component silicone adhesive, with a solid, elastomeric seal, at least in the circumferential joining region between the bottom and the cover The lid rests on the seal with a circumferential flange and is mechanically connected to the tubesheet by externally acting clips or clips, which may result in a manufacturing and assembly aid Under certain circumstances, one advantage of a liquid seal is that an "adhesive bond" can also be produced "wet-on-wet".

According to a further advantageous embodiment of the invention, a so-called diffuser plate, which is preferably designed as a multi-hole diaphragm in plastic used in the inlet-side collecting container, for. B. positioned and fixed by a simple clip connection. Due to the large number of pinhole diaphragms, it is possible under some circumstances to achieve a flow velocity which is more uniform over the tubes. The condensate can be in the vertically an¬ ordered, smooth on the inside, partly with Längssi- - A -

These flat tubes are very well drained so that a further improvement of the condensation conditions results.

An embodiment of the invention is illustrated in the drawing and will be described in more detail below. Show it

1 shows an air-cooled condenser in longitudinal section,

1 in a half side view and in half section, FIG. 1b shows the condenser according to FIG. 1 in a plan view with removed cover, FIG.

Fig. 2 shows a detail X of Fig. 1, Fig. 3 is a flat tube of the capacitor and

4 shows a cross section through a further flat tube formation with internal beads.

Fig. 1 shows a capacitor 1, as it z. B. for the condensation of moist process air of a fuel cell process, for example in a DMFC ("direct methanol fuel cell"), in particular for motor vehicles can find use.The moist process exhaust air has a relatively low pressure, contains, inter alia, water and methanol in vapor The condenser has an upper intake-side header 2 and a lower drain-side header 3, each with an inlet 4 and an outlet 5. The upper header 2 is composed of a cover 6 and a tube plate 7 - The lower collection box 3 in an analogous manner from a De¬ 8 and a tube sheet bottom plate 9. Between the two manifolds 2, 3 parallel flat tubes 10 are arranged, which are tightly received with their tube ends 11, 12 in the tube plates 7, 9 Intermediate see the individual flat tubes 10 are left column 13, in which no conventional Ribs are arranged - insofar, the capacitor 1 is a primary surface heat exchanger. The gaps 13 form smooth cooling air channels. In the upper header 2, a diffuser plate 14 is arranged, above the tube ends 11 and parallel to the tube plate 7. The diffuser plate 14 has a plurality of pinhole 15, ie calibrated Openings on. The diffuser plate 15 is fixedly arranged in the lid 6, z. B. fixed by a clip connection, not shown.

Fig. 1a shows the condenser 1 in a half-section and in a half-side view, in particular the diffuser plate 14 with the Lochblen¬ the 15 in the cover 6 can be seen. The diffuser plate 14 thus extends over the entire flow cross section of the process gases entering through the inlet connection 4, so that they can only reach the flat tubes 10 through the apertured apertures 15. Between the perforated plate 14 and the upper edge of the flat tube ends 11 there is a sufficient Zwischen¬ space 16, which allows a delay of accelerated by the pinhole 15 th flow of process gases, combined with a Druckan¬ rose. The direction of flow of the cooling air through the condenser 1 is indicated by an arrow L.

FIG. 1b shows a plan view of the tube plate 7 with the flat tube ends 11, which extend over the entire depth of the tube plate 7. This results in relatively long smooth surfaces in the direction of flow of the cooling air.

FIG. 2 shows a detail X of FIG. 1, ie an edge region of the tube bottom 7 with four flat tubes 10 and their flat tube ends 11, which are widened relative to the tubes 10. The tubesheet 7 (blackened) is a plastic injection molded part, for. B., made of a polyamide (PA). It has tube openings 17 into which the widened tube ends 11 are inserted in such a way that they project inwards relative to the tubesheet 7, ie have a tube projection Ü. The edge region of the bottom 7 has a circumferential groove 18, whose outer side 18a is pulled up to the height of the pipe protrusion Ü. As already mentioned, the collection box 2 (and analogously also the collection box 3) is composed of the lid 6 and the bottom 7. To join the two parts, the tube 7 is covered ("flooded") with a liquid or pasty sealant 19 after the tubes 10 have been inserted with their tube ends 11. Such a liquid sealant may be a two-component adhesive (silicone) is present in liquid form at the beginning of its processing and later hardens to an elastic mass.This sealing compound 19 then fills the Gaps between the flat tube ends 11 and the circumferential groove 18 from. In this liquid state, the lid 6, which has a flange 20 adapted to the channel 18 with a rib 20a, is then placed in the sealing compound 19 and on the tubesheet 7. In this case, the circumferential rib 20a immersed in the liquid sealant 19 and forms with this an enlarged sealing or setting surface, so that a mechanically fixed and tight connection between tube sheet 7 and cover 6 er¬ is. At the same time, the tubes 10 or their tube ends 11 are sufficiently sealed by the aus¬ hardening sealing compound 19 with respect to the tube plate 7 and mechanically supported due to the adhesive effect of the sealing compound 19. In principle, therefore, no mechanical widening of the tube ends 11 with respect to the tube openings is required 17 to be made, although this may be advantageous to increase the sealing and holding action.

Fig. 3 shows a single flat tube 10, the tube ends 11, 12 are widened in the longitudinal and transverse directions, which also shows in particular from the sectional view. The expansion of the flat tubes 10 takes place for the purpose of providing increased stability to the flat tubes, which are relatively unstable to internal pressure, in particular in the case of extreme depth, as here, d. H. in the field of pipe / floor connections. The cross section of the flat tube 10 is composed of two smooth, straight longitudinal sides 10a, 10b and in the region of the flat tube ends 11 of two smooth longitudinal sides 11a, 11b together and two semicircular arches 11c, 11d. Because of this simple oval shape, two straight lines and two semicircles, the corresponding tube openings in the tubesheet can be easily produced.

Fig. 4 shows a further embodiment of a flat tube 21, which in the longitudinal direction and mutually parallel, inwardly directed longitudinal beads 22 has. The flat tube 21 is significantly improved by these inner beads 22 in terms of its stability and receives a higher rigidity.

Alternatively, modified forms of the beads 22 in number and shape, ie, for example, not continuously possible. The beads 22 may also be directed outwards or replaced by round or elongated knobs. In order to can also be a support effect to the outside, ie be achieved from flat tube to flat tube. Otherwise, the inner surfaces of the flat tubes are essentially smooth, so that the condensate can drain off well.

Fig. 5 shows a further embodiment of a flat tube 23, which is composed of two half-shells, the front side are tight and optionally firmly connected. The connecting seams 24, 25 are preferably producible by welding, soldering, adhesive bonding and / or by folding. The otherwise difficult under certain circumstances to be sealed contour of the surfaces or edges to be joined is compensated by a liquid-pasty Ab¬ sealing compound or at least tolerable.

LIST OF REFERENCE NUMBERS

1 capacitor

2 collecting tank, inlet side

3 collection box, drain side

4 inlet nozzles

5 drain connection

6 lids, top

7 tubesheet, top

8 lids, below

9 tubesheet, bottom

10 flat tube

11 pipe end

12 pipe end

13 gap

14 diffuser plate

15 pinhole

16 space

17 pipe openings

18 gutter

18a outer wall

19 sealant

20 flange

20a rib

21 bead tube

22 inside bead

23 flat tube

Claims

Patent claims

1. Heat exchanger, in particular condenser (1) for a first vapor and / or gaseous fluid with an inlet side and ei¬ nem drainage side collecting tank (2, 3) and the two Sammelkäs¬ th (2, 3) connecting pipes, of the The first fluid can be flowed through and can flow around a second gaseous fluid, in particular air, and have tube ends, characterized in that the tubes are designed as flat tubes (10) and made of a corrosion-resistant material of high thermal conductivity, in particular stainless steel the collecting boxes (2, 3) are made of a corrosion-resistant material, in particular plastic, and each have a cover and a tube bottom, and that the tube ends (11, 12) are held firmly and tightly in the tube plates (7, 9) are.

2. Heat exchanger according to claim 1, characterized in that the flat tubes (10) are made of a thin-walled sheet and extending in the longitudinal direction beads, in particular internal beads or studs.

3. Heat exchanger according to claim 1 or 2, characterized marked, that between the flat tubes (10) ribless column (13) for

Guiding the cooling air are left.

4. Heat exchanger according to claim 1, 2 or 3, characterized gekenn¬ characterized in that the tube ends (11, 12) are widened.

5. Heat exchanger according to claim 1, 2, 3 or 4, characterized gekenn¬ characterized in that the collecting boxes (2) formed essentially in two parts, from cover (6) and tube sheet (7) are joined and a circumferential joining area ( 18, 20).

6. Heat exchanger according to one of claims 1 to 5, characterized ge indicates that the tube plate (7) on its the cover (6) zu¬ facing side with a layer of an adhesive Dichtmas- se (19) is covered, the one Seal the pipe ends (11) gegen¬ over the tube sheet (7) and / or between the lid (6) and Rohrbo¬ the (7) in the joining region (20, 18).

7. Heat exchanger according to claim 6, characterized in that the sealing compound is pourable and in particular consists of a Zweikom¬ component silicone (19).

8. Heat exchanger according to one of claims 1 to 7, characterized ge indicates that the collecting boxes (2, 3) and the cover (6) and tube sheets (7) made of a polyamide (PA), preferably as Spritz¬ castings are.,

9. Heat exchanger according to one of claims 1 to 8, characterized ge indicates that in the inlet side header box (2) a diffuser plate (14) is arranged parallel to the plane of the tube plate (7).

10. Heat exchanger according to claim 9, characterized in that the diffuser plate as a multi-hole (14, 15) is formed in particular of plastic.

11. Heat exchanger according to one of claims 5 to 10, characterized ge indicates that the cover (6) with the tube sheet (7) and / or the diffuser plate (14) with the lid (6) are clipped or latched.

12. Heat exchanger according to claim 5, characterized in that arranged between the cover (6) and tube sheet (7) in the joining region an elastomeric seal and that the cover (6) and the Rohrbo¬ the (7) are mechanically clamped.

13. Use of a capacitor according to at least one of the vorher¬ preceding claims for the cooling and condensation of process zessabgasen a fuel cell system, in particular in a DMFC.