EP0672882B1 - Heat exchanger fin - Google Patents

Description

The invention relates to a fin for a heat exchanger according to the preamble of claim 1.

Such heat exchanger fins were described in DE-A-37 28 969 and also known from DE-C-34 23 746. For the performance of a heat exchanger is among other things its rib density or so-called rib pitch (Number of ribs per dm) decisive - for reasons This predetermined rib density is therefore of constant quality to adhere exactly to why the positioning of the ribs on the Pipes certain spacers are provided. The latter can either as a flap protruding from the ribbed sheet, which then also act as turbulence generators, are formed, or by angled contact surfaces attached to the ends of the rib passages. In DE-A '969, these contact surfaces are on the circumference Distributed tongues formed and in the DE-C '746 as on the long sides of the ellipses arranged crescent-shaped contact surfaces. Disadvantageous in these versions, it may be that when expanding the Pipes no longer a complete system compared to the fins between passage and pipe is guaranteed. Otherwise means relocating the contact surfaces after an additional operation pulling through.

GB-A 2 088 035 developed a heat exchanger with flat tubes and Known ribs that are soldered to the tubes. The ribs point right-angled openings for receiving the flat tubes, taking off These openings have rectangular flaps in the area of the long sides are cut out and set up. These are flat rags soldered to the flat sides of the flat tubes. For spacing the ribs have these right-angled lobes in the form of noses (Figures 6 and 7). This kind of Pipe / fin connection is for mechanical production, i.e. without Soldering, not suitable.

GB-A 1 075 272 also shows a brazed flat tube system about rectangular openings in the ribs, from which rag in the area the long sides are upright. On this rag bends are provided at the end for spacing. Also this tube / fin connection is for a mechanical bond of Pipes and fins are not suitable.

GB-A 1 174 402 established a mechanically joined Pipe / fin system is known, in which the pipes compared to the Passages in the ribs are mechanically widened. The passages have bent tongues at the ends, distributed over the circumference, which serve to hold the ribs apart. Bending the tongues means an additional operation, which is the manufacturing cost elevated.

It is an object of the present invention to provide a rib at the beginning to improve the type mentioned in such a way that, on the one hand, safe spacing between the ribs, on the other hand good heat transfer guaranteed between tube and fins and beyond simple manufacture is possible.

This object is achieved by the characterizing features of the claim 1 solved. The new spacers in the form of Noses are partially stamped out of the wall of the passage, so that with its upper edge it is a contact surface for the above form arranged rib. The fact that several noses on the Scope of passage are distributed, there is a good and stable Support for the next rib. The noses are too easy to manufacture because of the additional folding process after pulling through is omitted. The heat transfer is also guaranteed since the noses are only partially provided and thus the heat transfer hardly between inner surface passage and outer surface pipe restrict. The noses also expand upwards is the lower tip of such a nose, e.g. in Shape of a half cone, slightly above the rib plane, so that a continuous circumferential contact surface of a certain width maintained between the tube and the fin passage for good heat transfer remains. Advantageous embodiments of the invention result from the subclaims, the invention being for both tubes with circular as well as oval or elliptical cross sections can be used advantageously is. The lugs advantageously have the shape of half pyramids or half cones divided in the vertical are.

Because a larger one for heat transfer reasons Clearance height is not necessary, the lugs are embossed in rags, which surpass the remaining draft in terms of its amount and thus the degree of rib division, i.e. the rib spacing. Recommended for oval or elliptical cross sections for technical reasons, the noses to be arranged against each other - this allows the maximum height of the Rags are made. If the rib spacing in relation to Pull width is smaller, the lugs or lobes can also opposite.

Finally, the invention also relates to a method for pulling through with the noses to make what's in four or three consecutive Operations are done with the imprint of the noses either by a punch stroke in the pulling direction or in the opposite direction he follows.

Figur 1

eine Rippe in der Draufsicht,

Figur 2

die Rippe gemäß Figur 1 im Schnitt, vergrößert,

Figur 3

einen Durchzug der Rippe gemäß Figur 1, vergrößert,

Figur 4a, 4b, 4c und 4d

die einzelnen Verfahrensschritte zur Herstellung des Durchzuges mit Nasen,

Figur 5

ein Rohr mit Rippen, vergrößert und

Figur 6

ein Detail aus Figur 5: Rohrwand mit Rippendurchzügen.

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

Figure 1

a rib in top view,

Figure 2

the rib of Figure 1 in section, enlarged,

Figure 3

a passage of the rib according to Figure 1, enlarged,

Figure 4a, 4b, 4c and 4d

the individual process steps for the production of the passage with noses,

Figure 5

a tube with fins, enlarged and

Figure 6

a detail from Figure 5: pipe wall with fins.

Figure 1 shows a rib 1 in plan view with flat oval passages 2, which are arranged offset in two rows to one another, wherein each gill panels 3 are arranged between the passages 2. The passages 2 accommodate pipes of the same cross section, not shown, which are mechanically widened with respect to these passages and thereby produce the contact necessary for heat conduction or heat transfer. In the area where no gill panels 3 and no passages 2 are provided, the rib 1 essentially forms a flat surface 4. Each passage 2 has - as will be explained in more detail below - three lugs 8, 9, 10. The rib 1 is preferably made of aluminum or an aluminum alloy and has a thickness of approximately 0.1 mm.

Figure 2 shows a section II-II through the rib of Figure 1 in an enlarged form, so that in particular the known inclined gills of the gill panels 3 can be seen. They deflect the air sweeping over the fins, which increases the air-side heat transfer. In this illustration, two passages 2 are shown in the side view, three tabs 5, 6, 7 each being recognizable, into which the lugs 8, 9, 10 are each stamped in the center. The tabs 5, 6, 7 are thus arranged offset from one another, ie the tabs 5 and 7 are located at the front, and the tab 6 is located at the rear, ie on the rear longitudinal side of the passage 2.

A passage 2, also enlarged, is shown in FIG. 3 , specifically in plan view a as a flat oval shape, from which the lugs 8, 9, 10 are clearly recognizable as bulges in the form of segments of a circle. A dash-dotted line 11 is drawn in the interior of the flat oval passage 2, which delimits a punched-out section 12, so that the passage surface 2 'can be seen in the flat, not yet solid state. Sections c and b of the passage are shown on the right and left of the passage a , the left illustration b showing the centrally arranged tab 6 with the nose 9 and the right illustration c showing the two off-center tabs 5 and 7 with the lugs 8 and 10. The lugs 8, 9, 10 each have an outwardly sloping upper edge 8 ', 9', 10 ', which determines the distance H' (see FIG. 6) of the ribs. It is clear that the height H of the tabs 5, 6, 7 exceeds the height h of the rest of the passage - however, a continuous area 13 of height h is obtained which bears on all sides on the outer circumference of the tube, so that a closed heat transfer surface between the rib and tube is formed, which also maintains the elastic tension required after expansion.

FIGS. 4a, 4b, 4c and 4d now - as already indicated in FIG. 3 by line 11 - show the individual process steps for producing the swipe according to the invention. FIG. 4a shows the ribbed sheet 20 after punching, ie a strip 24 with rounded ends 22, 23 is cut out of the flat ribbed sheet 20 by means of a suitable punch, whereby offset tabs 25, 26, 27 are cut free. According to FIG. 4b , in the subsequent process step, tabs 28, 29, 30 are embossed into these tabs 25, 26, 27 by means of an embossing stamp, which are pyramid-shaped, that is to say are formed from two planar triangular surfaces inclined towards one another. In the next process step, which is shown in FIG. 4c , the passage 21 is drawn in against a die 31 with a corresponding oval-shaped bending edge, that is to say only “tilted” so that the lugs come to rest against the inner wall of the die 31, but the rest Passage 21 is still conical. In Figure 4c , the tabs 25 ', 26', 27 'are therefore shown shortened compared to Figure 4b.

In the last process step according to FIG. 4d , the passage is completed, ie the collar 21 is pulled through by means of a stamp, not shown, so that it acquires a cylindrical shape (with a flat oval cross section) and the noses 25 ″, 26 ″, 27 ″ as The triangles protrude outwards, which is made possible by corresponding cutouts 32, 33, 34 in the die. With the described method, the passages with the molded noses can be produced simply, quickly and with consistent quality.

Another method is also possible in which the method steps according to Figures 4b and 4c only at the end, namely by means of an embossing stamp that enters the finished passage from above.

FIG. 5 shows an enlarged section of a tube 40, on which ribs 41 to 45 are “threaded”. This tube 40 is part of a heat exchanger (not shown in more detail), the tube shape and division and fin design of which could correspond to FIG. As already mentioned, the ribs 41 to 45 are mechanically joined to the tube 40, ie connected by expanding the tube 40 with respect to the rib passages by means of a metallic press fit. So there is no soldering or gluing, ie material connection is necessary.

FIG. 6 shows an enlargement of a section from FIG. 5, namely a part of the tube wall 40 and three rib cutouts 41, 42, 43 which, with their passages 46, 47, 48 of height h, lie closely and circumferentially on the tube 40, while their noses 49, 50 , 51 protrude from the outer wall of the tube 40 and determine the distance H 'between the ribs 41, 42, 43 with its upper edge. The rib spacing H 'is slightly smaller than the height H of the tabs (cf. FIG. 3b, c) because the rib passage has a transition radius on which the lugs are supported. Both FIGS. 5 and 6 show the finished tube / fin arrangement, ie after the tube 40 has been expanded in the mechanically finished state of the tube and fin passages.

Such fins connected with a bundle of parallel tubes are, in turn, taken up in tube sheets from collecting tanks are used in particular in heat exchangers for motor vehicles, e.g. as a coolant / air cooler for the engine or as a heating heat exchanger. Flat oval tube cross-sections work here advantageous in terms of air pressure drop.

Claims (10)

1. A fin for a heat exchanger essentially consisting of a matrix of tubes and fins (1; 41:45) arranged transversely thereto, the fins having punched mountings (2; 46:48) for receiving the tubes to be mechanically joined and a first, preferably liquid medium flows through the tubes and a second, preferably gaseous medium is applied to the fins which are positioned by means of integral spacers in the pitch of the fin, characterised in that the spacers are provided in the form of noses (8, 9, 10; 49, 50, 51) stamped out from the punched mountings (2; 46:48) distributed around the circumference thereof, the noses (8, 9, 10) being wider in the punching direction to form a top abutment edge (8', 9', 10'), and the bottom edge of the noses (8, 9, 10; 49, 50, 51) is arranged more or less at a height h above the plane (4) of the fin thereby leaving a surrounding punched ring (13) lying against all sides of the tube.
2. A fin as claimed in claim 1, characterised in that the tubes and the punched mountings (2) are circular in cross-section.
3. A fin as claimed in claim 1, characterised in that the tubes and the punched mountings (2) are oval or elliptical in cross-section, preferably having an axial ratio greater than 3 : 1.
4. A fin as claimed in claim 1, 2 or 3, characterised in that the noses (8, 9, 10) have, in planes parallel with the fins, a semi-circular, arcuate, semi-ellipsoid or triangular cross-section.
5. A fin as claimed in one of the preceding claims, characterised in that the noses (8, 9, 10) are stamped out from flaps (5, 6, 7) respectively, the height H of which is greater than the height h of the remainder of the punched mounting (2).
6. A fin as claimed in one of the preceding claims with the exception of claim 2, characterised in that the noses (8, 9, 10) are arranged on the longitudinal sides of the punched mountings (2).
7. A fin as claimed in claim 6, characterised in that the noses (8, 9, 10) are arranged offset from one another.
8. A method of manufacturing punched mountings for fins as claimed in one of the preceding claims, characterised by the following process steps:

   a) punching orifices (12; 22-23-24) are punched into the flat fin plate (4), flaps (25, 26, 27) being cut free,

   b) noses (28, 29, 30) are stamped into the flaps (25, 26, 27) by means of a stamping die pushed in the punching direction,

   c) the flaps (25, 26, 27) together with the outwardly punched noses (28, 29, 30) are pushed in and tilted back by means of a stamp and die and

   d) the entire punched mounting, i.e. collar (21) with flaps (25, 26, 27) is fully punched through.
9. A method of manufacturing punched mountings for fins as claimed in one of claims 1 to 7, characterised by the following process steps:

   a) punching orifices are punched into the flat fin plate(4) and flaps cut free,

   b) the entire punched mounting, i.e. collar with flaps, is punched into a cylindrical shape,

   c) the noses are punched by means of a punching die which travels from above into the free end of the punched mounting.
10. A heat exchanger essentially consisting of a matrix of tubes with fins arranged transversely thereto, the fins having punched mountings for receiving the mechanically jointed tubes and a first, preferably liquid medium flows through the tubes and a second, preferably gaseous medium is applied to the fins which are positioned by means of integral spacers in the pitch of the fin, characterised by fins as claimed in one of claims 1 to 7.

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