U.S. patent application number 10/585665 was filed with the patent office on 2008-08-14 for heat exchanger.
This patent application is currently assigned to BEHR GMBH & CO. KG. Invention is credited to Wolfgang Kramer.
Application Number | 20080190589 10/585665 |
Document ID | / |
Family ID | 34716367 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190589 |
Kind Code |
A1 |
Kramer; Wolfgang |
August 14, 2008 |
Heat Exchanger
Abstract
The invention relates to a heat exchanger and a rib (1), in
particular a corrugated rib (1), especially for a flat tube heat
exchanger, in particular a coolant or charge-air cooler for motor
vehicles. The corrugated rib (1) is arranged between flat tubes (3)
of the heat exchanger, is connected thereto in a material fit,
comprises gills (6, 8), can be exposed to a flow of air and
comprises moulded reinforement means.
Inventors: |
Kramer; Wolfgang;
(Weinstadt, DE) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
BEHR GMBH & CO. KG
|
Family ID: |
34716367 |
Appl. No.: |
10/585665 |
Filed: |
December 6, 2004 |
PCT Filed: |
December 6, 2004 |
PCT NO: |
PCT/EP2004/013832 |
371 Date: |
November 13, 2007 |
Current U.S.
Class: |
165/152 ;
165/153 |
Current CPC
Class: |
F28F 2250/02 20130101;
F28F 1/325 20130101; F28F 3/027 20130101; F28F 2225/00 20130101;
F28F 1/128 20130101 |
Class at
Publication: |
165/152 ;
165/153 |
International
Class: |
F28D 1/02 20060101
F28D001/02; F28F 1/02 20060101 F28F001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2004 |
DE |
10 2004 001 306.3 |
Claims
1. A fin, in particular corrugated fin, in particular for a flat
tube heat exchanger, in particular a coolant or charge-air cooler
for motor vehicles, the fin being arranged between flat tubes of
the heat exchanger or being arranged perpendicularly to them and
being connected to them with a cohesive material joint or
mechanically, being provided with gills and being able to be flowed
over by air and having molded stiffening means, characterized in
that the stiffening means are integrated in the gills.
2. The fin as claimed in claim 1, wherein the gills have a
buckle-proof profile which deviates from a straight line or a
rectangular profile.
3. The fin as claimed in claim 2, wherein the profile has an
S-shaped cross section with two rounded portions.
4. The fin as claimed in claim 2, wherein the profile has a cross
section which is bent twice, three times or multiple times, for
example an approximately Z-shaped cross section.
5. The fin as claimed in claim 2, wherein the profile has an
approximately V-shaped cross section which is bent once.
6. The fin as claimed in claim, wherein cross section has an
incident-flow region and a flow-off region and a deflecting region
arranged between them, the incident-flow region and flow-off region
respectively having an incident-flow angle and flow-off angle
(.alpha.s, .alpha.z) of approximately the same size, and the
deflecting region having a deflecting angle (.beta.s, .beta.z), in
that the deflection angle is greater than the incident-flow angle
and flow-off angle, i.e. .beta.s>.alpha.s and .beta.z
.alpha.z.
7. The fin as claimed in claim 1 wherein the following ranges apply
for the angles .alpha.s and .beta.s: 0 .alpha.s.ltoreq.10 degrees,
and 15 .beta.s.ltoreq.35 degrees.
8. The fin as claimed in claim 1 wherein the following ranges apply
for the angles .alpha.s and .beta.s: 0 .alpha.s.ltoreq.5 degrees,
and 20 .beta.s.ltoreq.30 degrees.
9. The fin as claimed in claim 1 wherein the following ranges apply
for the angles .alpha.z and .beta.z:
Description
[0001] The invention relates to a heat exchanger, such as, in
particular, a flat tube heat exchanger, and to a fin, such as, in
particular, a corrugated fin, for example for a flat tube heat
exchanger, in particular for a coolant or charge-air cooler or
condensers or evaporators for motor vehicles according to the
precharacterizing clause of patent claim 1.
[0002] Heat exchangers of this type have been disclosed by EP 0 547
309 B1 by the applicant.
[0003] Corrugated fins and flat tubes form a soldered cooling
system in which a medium to be cooled, for example a coolant or
charge air, flows through the flat tubes and a cooling medium, for
example ambient air, flows over the corrugated fins. Soldered
cooling systems of this type are used for coolant coolers for
cooling an internal combustion engine or as charge-air coolers, for
cooling the compressed intake air of internal combustion engines in
motor vehicles. Heating elements or condensers or evaporators, for
example, are also of similar construction. Fins can also be used in
mechanically joined heat exchangers in which the fins and the tubes
of the heat exchangers are connected mechanically to one
another.
[0004] Development tends to go in the direction of higher pressures
for the medium to be cooled, in particular in the coolant circuit,
with the flat tubes being of extremely slender design on account of
the lower pressure drop on the air side, and therefore being
extremely unstable to increased internal pressure. The flat tubes
therefore tend to "swell", i.e. to form a bulge, under internal
pressurization. This bulge can be counteracted from the inside and
outside: in the interior of the flat tube, use is made of
soldered-turbulence inserts which act as tie rods, and corrugated
fins exert a supporting effect on the flat tubes from the outside.
The-flat tubes are provided with gills to improve the heat
transfer, which has disadvantages in terms of strength. The
corrugated fins therefore tend to buckle at higher internal
pressure loading of the flat tubes.
[0005] It has therefore been proposed in U.S. Pat. No. 4,693,307-A
to mold a stiffening bead into the center of a gilled panel, i.e.
an individual double gill which is designed in the shape of a roof
and at the same brings about a deflection of the flow.
[0006] EP 0 547 309 B1by the applicant has disclosed a corrugated
fin for flat tubes, in which a stiffening bead is arranged between
two gilled panels and in the center of the flat tube, i.e. the
point at which the greatest buckling stress occurs for the
corrugated fin. However, only a spot-type stiffening of the
corrugated fin is achieved with this, which is no longer adequate
if the stress increases as a consequence of increased internal
pressure.
[0007] It is the object of the present invention to improve a
corrugated fin of the type mentioned at the beginning with regard
to its supporting effect without its thermodynamic properties, such
as heat transfer and pressure drop, being adversely affected.
[0008] This object is achieved by the features of patent claim 1
and of claim 11. According to the invention, the stiffening means
are integrated in the gills, i.e. in principle all of the gills of
the corrugated fin contribute to the supporting effect. The flat
tubes are therefore supported over their entire length by a
stiffened corrugated fin. Each individual gill advantageously has a
buckle-proof profile with which the entire corrugated fin obtains
increased security against buckling.
[0009] According to an advantageous refinement of the invention,
the profile of each gill has an S-shaped cross section. This
achieves the advantage of a greater moment of resistance to
buckling without the pressure drop on the air side-over the
corrugated fin increasing significantly--in contrast, even a lower
pressure drop is to be expected. The gills of S-shaped design in
cross section therefore have, in contrast to the prior art, a
variable gill angle which initially rises from a very low value to
a maximum value in the center of the gill length and then goes back
again to a minimum value. A "gentle" deflection of the air flow is
therefore achieved without--as in the prior art--loss-affected
eddies occurring at the incident-flow edge and flow-off edge of the
gills. An unexpected combination effect turns out to be
advantageous by the buckling resistance of the gills being
increased and their pressure drop being reduced at the same
time.
[0010] According to a further advantageous refinement of the
invention, the cross section of the gills is bent twice and has an
approximately Z-shaped profile, i.e. the gill bent in accordance
with the invention has three gill angles, with the gill angle
jumping at the first buckling point from a low to a high value and
jumping again at the second buckling point to the low value. In
comparison to the S-shape, the Z-shape therefore has a
discontinuous profile of the gill angle over the gill length, which
affords simplification in terms of manufacturing. Moreover, the
advantage is also achieved here of increased buckling resistance,
associated with a reduced pressure drop.
[0011] According to further advantageous refinements of the
invention, advantageous angle dimensions are indicated both for the
S-shaped and for the Z-shaped cross section of the gill. In this
case, in particular the low incident-flow angle and flow-off angle
are advantageous because, as a result--as already mentioned--a
formation of eddies behind the incident-flow edge and flow-off edge
is avoided. At the same time, the heat transfer capacity of the
corrugated fin is not made worse, since, as before, a new starting
of the thermal boundary layer takes place at each incident-flow
edge of a gill. This mechanism is responsible for a large part of
the heat transmission. Finally, the advantage is also achieved
thereby that the entire heat exchanger is improved in respect of
its efficiency.
[0012] Exemplary embodiments of the invention are illustrated in
the drawing and are described in more detail below. In the
drawing
[0013] FIG. 1 shows a corrugated fin with gills according to the
prior art in a view from the front,
[0014] FIG. 2 shows the corrugated fin according to the prior art
in a plan view,
[0015] FIG. 3 shows a section through the corrugated fin according
to FIG. 2 along the line III-III,
[0016] FIG. 4 shows the corrugated fin according to the prior art
and its loading,
[0017] FIG. 5 shows a corrugated fin according to the invention
with an S-shaped cross section,
[0018] FIG. 6 shows a corrugated fin according to the invention
with a cross section with a double bend,
[0019] FIG. 7 shows a detail X from FIG. 5, and
[0020] FIG. 8 shows a detail Y from FIG. 6.
[0021] FIG. 1 shows a corrugated fin 1 with gills 2 as seen in the
air flow direction. The corrugated fin 2 is part of a cooling
system (not illustrated at all), comprising corrugated fins and
flat tubes 3 which are indicated by dashed lines. The corrugated,
fins are arranged in each case between two tubes. The tubes are,
for their part, connected in a fluid-tight manner at their end
regions to header boxes. The tubes are typically inserted into
openings in the header box and are connected in a fluid-tight
manner to them. The tubes are preferably pushed into a tube plate
with openings and are connected in a sealed manner, so that the
fluid can pass from one header box to the other header box by the
fluid connections within the tubes. The corrugated fin 1 and the
flat tubes 3 are preferably in each case composed of an aluminum
material and are soldered to one another. However, in other variant
embodiments, use can also be made of other materials, such as, for
example, steel in particular for exhaust gas heat exchangers, or
copper or other alloys.
[0022] FIG. 2 shows the corrugated fin 1 in a plan view, with the
air flow direction being illustrated by an arrow L. The gills 2
form two gilled panels with front gills 2a and rear gills 2b.
[0023] FIG. 3 shows a section along the line III-III and the
oppositely directed gill angles .alpha.1 and .alpha.2 of the front
gills 2a and of the rear gills 2b, respectively.
[0024] FIG. 4 shows the corrugated fin 1 according to the prior art
and its loading by the flat tubes (not illustrated here) when the
latter are subjected to internal pressure. The loading of the
corrugated fin 1 is illustrated by arrows P1, P2 which act in each
case on a fin bend 1a, 1b. This results in a pressure loading of
the fin sections between the fin bend 1a, 1b, i.e. also to a
pressure loading of the gills 2, which are also therefore subject
to a buckling load. Owing to the rectangular cross section of the
known gills 2, a relatively low buckling load is produced here
permitting the corrugated fin 1 to buckle as per the prior art (cf.
Dubbel, Taschenbuch fur den Maschinenbau [Handbook for machine
construction], 20th edition, C 43).
[0025] FIG. 5 shows a corrugated fin 5 according to the invention
with front gills 6a and rear gills 6b which have an S-shaped cross
section. The S-shaped cross section is characterized by a
continuously variable gill angle from the entry to the exit of the
air flow. An enlarged cross section is illustrated as detail X in
FIG. 7 and is described there in more detail.
[0026] FIG. 6 shows a further embodiment of the invention, namely a
corrugated fin 7 with front gills 8a and rear gills 8b which are in
each case bent twice,. i.e. have a double bend. The gill angle
changes discontinuously in the case of this double bend gill 8a,
8b, i.e. changes in each case at the buckling point. An enlarged
illustration is illustrated as detail Y in FIG. 8 and is described
in more detail there.
[0027] FIG. 7 shows the detail X from FIG. 5, i.e. the gill 6a,
which is arranged symmetrically upward and downward with respect to
a central plane e of the corrugated fin 5. The S-shape of the gill
6a has an approximately sinusoidal profile and is characterized by
three sections, namely an incident-flow region 9, a central
deflecting region 10 and a flow-off region 11. The inclinations of
the individual regions 9, 10, 11 are depicted by straight lines a,
b, c. There is a continuous transition in each case between the
sections 9, 10, 11. The incident-flow section 9 forms an
incident-flow angle as with the central plane e, and the flow-off
region 11 forms a flow-off angle .alpha.s with the central plane e,
i.e. the angle between the straight lines c and e. The central
cross-sectional region 10, i.e. the deflecting region, forms a
deflecting angle .beta.s with the central plane e (angle between
the straight lines b and e). The angles .alpha.s lie in a range of
from 0 to 10 degrees, preferably in a relatively narrow range of
from 0 to 5 degrees. The deflecting angle .beta.s lies in a range
of from 15 to 35 degrees and preferably in a range of from 20 to 30
degrees. The air flow characterized by an arrow L therefore
impinges in the incident-flow region 9 on an extremely small
incident-flow angle .alpha.s, so that no separations and eddies
form on the rear side or suction side of the gill profile. The
incident-flow angle .alpha.s, which corresponds to the gill angle
.alpha. in the prior art, changes with increasing flow around the
gill 6a up to the value .beta.s and then decreases again to the
value as in the region 11. A separation-free flowing off of the air
therefore also takes place. The S-shaped cross section of the gill
6a produces an increased moment of resistance to buckling, i.e. a
higher permissible buckling load--in comparison to the known
rectangular cross section.
[0028] FIG. 8 shows the detail Y from FIG. 6, i.e. the corrugated
fin 7 with gills 8a which are bent twice and have a cross section
with a double bend or an approximately Z-shaped profile. The
central plane of the corrugated fin 7 is also indicated here with
e, i.e. as a reference plane for the individual angles. The cross
section of the gill 8a is divided into three sections, namely an
incident-flow section 12, a central deflecting section 13 and a
flow-off section 14, with all three sections 12, 13, 14 running
approximately rectilinearly and being connected to one another by
radii r. The inclinations of the individual sections 12, 13, 14 are
marked by straight lines a, b, c and form the incident-flow angle
and flow-off angle .alpha.z and the deflecting angle .beta.z with
the reference plane e. The air flow in turn is illustrated by an
arrow L, and it can be seen that the incident-flow angle .alpha.z
is relatively small, so that hardly any flow-separation phenomena,
if any at all, arise on the suction side of the incident-flow
section 12 and also of the deflecting section 13. The air flow can
therefore bear against the suction side of the gill 8a, which
results in a low pressure drop. The incident-flow and flow-off
angles .alpha.z lie in the range of from 0 to 25 and preferably in
the range of from 5 to 15 degrees, and the deflecting angle .beta.z
lies in the range of from 15 to 35 degrees and preferably in the
range of from 20 to 30 degrees. This Z-shaped profile of the gill
8a also results in an increased moment of resistance to buckling,
which is added to the number of gills to form an increased overall
moment of resistance to buckling for the entire corrugated fin.
[0029] The production of the above-described gills, i.e. both with
an S-profile and with a Z-profile, takes place in a similar manner
as in the prior art, i.e. by means of "ribbed cutting rollers",
which cut the gills out of a planar sheet-metal strip and shape
them.
* * * * *