U.S. patent application number 10/542711 was filed with the patent office on 2006-03-16 for heat exchanger, especially gas cooler.
Invention is credited to Uwe Forster, Kurt Molt.
Application Number | 20060054313 10/542711 |
Document ID | / |
Family ID | 32602865 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054313 |
Kind Code |
A1 |
Forster; Uwe ; et
al. |
March 16, 2006 |
Heat exchanger, especially gas cooler
Abstract
The invention relates to a heat exchanger, especially a gas
cooler for a CO2 coolant circuit of a motor vehicle air
conditioning unit, comprising at least one collecting box that is
divided into two longitudinal ducts by means of a longitudinal
partition, and a series of flat tubes that are provided with ends
which are accommodated within openings located in the collecting
box and are fluidically connected to the longitudinal ducts.
Inventors: |
Forster; Uwe; (Algorbitzer
Ring, DE) ; Molt; Kurt; (Bietigheim-Bissingen,
DE) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Family ID: |
32602865 |
Appl. No.: |
10/542711 |
Filed: |
November 7, 2003 |
PCT Filed: |
November 7, 2003 |
PCT NO: |
PCT/EP03/12467 |
371 Date: |
July 20, 2005 |
Current U.S.
Class: |
165/173 |
Current CPC
Class: |
F28D 1/0535 20130101;
F28D 2021/0073 20130101; F28F 9/0214 20130101 |
Class at
Publication: |
165/173 |
International
Class: |
F28F 9/02 20060101
F28F009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2003 |
DE |
103-02-412.3 |
Claims
1. A heat exchanger, especially gas cooler for a CO2 coolant
circuit of a motor vehicle air conditioning system, having at least
one collecting box (2) which is divided into two longitudinal ducts
(5, 6) by a longitudinal dividing wall (7), and a series of flat
tubes (3) with flat tube ends (3a) which are accommodated in
openings (4) in the collecting box (2), and are fluidically
connected to the longitudinal ducts (5, 6), wherein the collecting
box (2) with the longitudinal ducts (5, 6) is bent from a prepared
sheet metal strip (8) with longitudinal edges (9, 10) having
tongues (11, 12) and a central connecting region (14) having
cutouts (13), the longitudinal edges (9, 10) forming the
longitudinal dividing wall (7) and being anchored in the cutouts
(13) via the tongues (11, 12).
2. The heat exchanger as claimed in claim 1, wherein the tongues
(11, 12) and cutouts (13) are arranged on the side of the
collecting box (2) facing the flat tubes (3).
3. The heat exchanger as claimed in claim 1, wherein the tongues
(23) and the cutouts (24) are arranged on the side of the
collecting box (21) facing away from the flat tubes (22).
4. The heat exchanger as claimed in claim 1, wherein the
longitudinal dividing wall (7, 25) has notches (15, 27) in which
the flat tube ends (3a, 22a) engage.
5. The heat exchanger as claimed in claim 1, wherein the collecting
box or parts of the collecting box are provided with corresponding
shaped portions, integrally formed-on portions and/or beads which
serve as stops for the tubes.
6. The heat exchanger as claimed in claim 4, wherein gaps (16, 28)
are left between the notches (15, 27) and the flat tube ends (3a,
22a).
7. The heat exchanger as claimed in claim 6, wherein the gaps (16)
are formed in a U shape.
8. The heat exchanger as claimed in claim 6, wherein the gaps are
arranged laterally and the notches form a stop for the tube
ends.
9. The heat exchanger as claimed in claim 6, wherein gaps (28) are
arranged above and/or below the flat tube ends (22a, 22b).
10. The heat exchanger as claimed in claim 1, wherein the tongues
(11, 12; 23) and cutouts (13, 24) are arranged between the n-th
flat tube (3, 22), where n=1, 2, 3, 4, 5, . . . .
11. The heat exchanger as claimed in claim 1, wherein the cross
sections of the longitudinal ducts (5, 6; 23, 24; 36, 37) are of
approximately circular design, in particular over a circumferential
range of at least 270 degrees.
12. The heat exchanger as claimed in claim 11, wherein the central
connecting region (35) which accommodates the tongues (34) is
stepped back in the direction of the longitudinal dividing wall
(33) by an amount x and is curved toward the outside.
13. The heat exchanger as claimed in claim 1, wherein the cross
sections of the longitudinal ducts are different in shape and/or
size.
14. The heat exchanger as claimed in claim 1, wherein the
longitudinal dividing wall has at least one opening or notch or
overflow opening.
Description
[0001] The invention relates to a heat exchanger, especially a gas
cooler for a CO.sub.2 coolant circuit of a motor vehicle air
conditioning system, according to the preamble of patent claim
1.
[0002] Heat exchangers for air conditioning systems with R134a as
the coolant, for example condensers, are composed of a heat
transfer network with flat tubes and collecting tubes which are
arranged on each side of the network and have a circular cross
section or some other cross section. Other heat exchangers for air
conditioning systems, for example two-row evaporators according to
DE-A 198 26 881 by the applicant, have a collecting box which is
divided into two longitudinal chambers and which is manufactured
from a prepared sheet metal plate by bending the edge regions of
the sheet metal plate. In this way, a central, double-layered
longitudinal dividing wall is obtained and is secured in cutouts in
the flat bottom of a collecting box by means of tongues. Two rows
of passages for the two rows of flat tubes are arranged in the
bottom, that is to say each longitudinal chamber communicates with
a row of flat tubes. This design already provides a relatively high
level of compressive strength. In modern air conditioning systems
which use CO.sub.2 (R744) as the coolant there are, however,
relatively high pressures which are multiplied by approximately 10
and can no longer be coped with using the conventional designs for
heat exchangers. For this reason, extruded collecting tubes with an
increased wall strength have been proposed in WO 98/51 983, a
collecting tube being composed of four circular flow ducts which
are arranged one next to the other. Owing to the tools which are
required for this, such an extruded collecting tube is costly to
manufacture.
[0003] Another type of collecting tube has been proposed in DE-A
199 06 289, with a collecting tube being constructed of two or
three extruded or pressed components and having two circular flow
ducts for the coolant (CO.sub.2). With this design also it is
necessary for at least part of the collecting tube to be
manufactured by extrusion or some other costly shaping method,
which usually has an unfavorable effect on the manufacturing costs
of the heat exchanger, for example the gas cooler.
[0004] The object of the present invention is therefore to improve
a heat exchanger of the type mentioned at the beginning to the
effect that the collecting box has a high degree of strength with a
low weight and can be manufactured cost-effectively.
[0005] This object is achieved by means of the features of patent
claim 1.
[0006] As is known from the prior art (DE-A 198 26 881) which is
mentioned at the beginning, the collecting box is formed in one
piece and is bent out of a sheet metal strip in such a way that two
longitudinal ducts are produced which are, however, fluidically
connected, in contrast to this prior art, only to one row of flat
tubes. This design of the collecting box permits an approximately
circular cross section and thus a pressure-resistant collecting
box. The double-layered longitudinal dividing wall is secured and
anchored in a central region of the sheet metal strip by means of
tongues, which facilitate fabrication and increases the
strength.
[0007] According to one advantageous development of the invention,
the tongues for securing the longitudinal dividing wall may be
arranged either on the side facing the flat tubes or on the side
facing away from the flat tubes. This increases the configuration
possibilities of the heat exchanger.
[0008] According to one advantageous development of the invention,
notches in which the flat tube ends engage are formed in the
longitudinal dividing wall, in the region of the flat tube ends
which project into the longitudinal ducts. As a result, the flat
tubes can be pushed into the collecting box by a relative distance,
approximately as far as the center, and formed at a maximum depth
(the depth of the flat tube is measured in the direction of air
flow). The collecting box is deeper than the flat tube only to an
insignificant degree. This advantageously provides space for shaped
portions or passages.
[0009] In a further advantageous embodiment of the invention, gaps,
which may be formed, for example, in a U shape or be arranged only
to the side of the flat tube or above it, are left between the
notches and the flat tube ends. It is advantageous here if the
notches serve simultaneously as a stop for the flat tubes when the
latter are pushed into the collecting box through the slot-shaped
openings. This results in precise positioning for the flat tubes in
the collecting box. The gaps permit pressure and flow to be
equalized between the two longitudinal ducts which are arranged one
next to the other.
[0010] According to a further advantageous embodiment of the
invention, the region of the collecting box in which the cutouts
are arranged with the tongues can be stepped back somewhat toward
the interior, i.e. in the direction of the longitudinal dividing
wall, as a result of which a certain degree of "cutting to size" of
the cross section of the collecting box is carried out. This
ensures that the cross sections of the longitudinal ducts are
approximated even more, i.e. beyond 270 degrees circumference, to a
circular cross section which then fits the strength and the
weight.
[0011] Finally, it may also be advantageous to form the cross
sections of the two longitudinal ducts so that they are not the
same but rather different, and at the same time the dividing wall
can be positioned off-center, i.e. asymmetrically. An essential
feature for the configuration of the collecting box is that the
tongues are arranged approximately at right angles to the
connecting strip with the cutouts in order to bring about an
optimum tie rod effect.
[0012] Exemplary embodiments of the invention are illustrated in
the drawing and will be described in more detail in the text which
follows. In the drawing:
[0013] FIG. 1 is a perspective partial view of a gas cooler,
[0014] FIG. 2 shows a section through the gas cooler according to
FIG. 1,
[0015] FIG. 3 shows a section along the line III-III in FIG. 2,
[0016] FIG. 4 shows a second exemplary embodiment of a gas
cooler,
[0017] FIG. 5 shows a section through the gas cooler according to
FIG. 4,
[0018] FIG. 6 shows a section along the line VI-VI in FIG. 5,
and
[0019] FIG. 7 shows a third exemplary embodiment of a gas cooler in
section.
[0020] FIG. 1 shows a detail of a gas cooler 1 with a collecting
box 2 and flat tubes 3 which open with their flat tube ends 3a into
the collecting box 2 and are accommodated in slot-shaped openings
4. Corrugated ribs for enlarging the air-side heat transfer face
are provided between the flat tubes 3, and are not illustrated. The
gas cooler 1 is suitable in particular for use in a coolant circuit
with CO.sub.2 as a coolant of a motor vehicle air conditioning
system but is not restricted to this application. Gaseous CO.sub.2
flows through the gas cooler on the primary side, i.e. in the
collecting boxes and the flat tubes, at a pressure of approximately
120 bar and ambient air is applied to it on the secondary side;
said gas cooler has the function of cooling the CO.sub.2 gas from a
temperature of approximately 150 degrees Celsius to 50 degrees
Celsius. The pressure which occurs in this context is approximately
ten times that of conventional condensers in a circuit with the
coolant R134a.
[0021] FIG. 2 shows the gas cooler 1 according to FIG. 1 in a
section, the construction of the collecting box 2 clearly being in
one piece. Said collecting box 2 has two longitudinal chambers 5, 6
which are divided from one another by a double longitudinal
dividing wall 7. The collecting box 2 is manufactured from a sheet
metal plate or a sheet metal strip 8 which has external edge strips
or longitudinal edges 9, 10 which are provided with tongues 11, 12.
Cutouts 13 are arranged in the center of the sheet metal strip 8 in
a way which corresponds to the arrangement of the tongues 11,
12.
[0022] The collecting box 2 is manufactured from the sheet metal
strip 8 which has been prepared, i.e. cut to size and punched out,
in such a way that the sides with the longitudinal edges 9, 10 are
bent over to form approximately cylindrical ducts 5, 6 and that the
longitudinal edges 9, 10 are moved back to the center,
approximately perpendicularly to a central connecting region 14
where they are plugged into the cutouts 13 by means of the tongues
11, 12. As a result the longitudinal edges 9, 10 are secured and
the collecting box 2 is ready for the soldering process. The flat
tubes 3 are plugged by their flat tube ends 3a into the openings 4
and project with their upper edge 3b approximately halfway into the
free cross section of the longitudinal ducts 5, 6. Since the cross
section of the longitudinal ducts 5, 6 is at its maximum width
here, the cross section which tapers after this produces a stop for
the flat tubes 3.
[0023] FIG. 3 shows a section through the gas cooler 1 in the plane
III-III in FIG. 2. This section through the longitudinal duct 5
shows the dividing wall 7 which has U-shaped notches 15 in the
region of the flat tube ends 3a. A gap 16 which clears a
throughflow cross section between the two longitudinal ducts 5, 6
is left between the contour of the flat tube ends 3a and the
contour of the notch 15. Through this gap 16 it is possible, on the
one hand, for the coolant also to emerge in the center of the flat
tubes ends 3a, and, on the other hand, coolant can flow from one
longitudinal duct 5 into the other longitudinal duct 6 and vice
versa so that pressure equalization can take place between the two
longitudinal ducts. The notches 15 and the gap shape 16 are
indicated only in exemplary fashion in the drawing, and the shape
of the gap can also be modified in such a way that there is a gap
only above the flat tube ends, i.e. above the upper edge 3b, or
only to the side of the flat tube ends 3a. In the latter case, the
upper edge 3b of the flat tube would abut against the notch in the
dividing wall 7, which would result in a stop. The tongues 11, 12
protrude above the outer wall of the collecting box 2 and are each
arranged approximately centrally between two flat tubes 3. However,
it is also possible to bridge one or more distances between flat
tubes and to arrange the tongues 11, 12 and the cutouts 13 at any
desired distances respectively between two flat tubes.
[0024] FIG. 4 shows a further exemplary embodiment of a gas cooler
20 with a collecting box 21 and flat tubes 22. Tongues 23 and
cutouts 24 are arranged here on the upper side of the collecting
box 21, i.e. on the side facing away from the flat tubes 22.
[0025] FIG. 5 shows this gas cooler 20 in section. The collecting
box 20 is in principle of the same design as in the exemplary
embodiment according to FIG. 2 but mirror inverted. The collecting
box 21 has two longitudinal chambers 21a, 21b which are divided
from one another by a double longitudinal dividing wall 25. Flat
tubes 22 are pushed into the collecting box 21 by an opening (not
shown here) so that with their flat tube ends 22a they fill
approximately half of the longitudinal ducts 21a, 21b. The upper
edge 22b therefore lies at the height of the maximum width of the
internal cross section. The flat tube 22 has a continuous depth t
which extends into the collecting box 21.
[0026] FIG. 6 shows a section in the plane VI-VI through the
longitudinal ducts 21a in FIG. 5. The flat tubes 22 are inserted
into collecting boxes 21 through corresponding openings 26, with
the openings 26 extending over the full depth t of the flat tube
22. Approximately circular notches 27 are arranged above the upper
edge 22b of the flat tube ends 22a, said notches 27 merging with
the rectangular cross section corresponding to the flat tube cross
section and thus permitting the flat tube ends 22a to be inserted.
An approximately circular gap 28, which forms a passage cross
section between the two longitudinal chambers 21a, 21b, is left
above the upper edge 22b of the flat tube ends 22a. No gap is left
directly next to the flat tube ends 22a. The tongues 23 and also
the cutouts (not shown here) are also respectively arranged here
between the flat tubes 22.
[0027] FIG. 7 shows a third exemplary embodiment of a gas cooler 30
with a collecting box 31 and flat tubes 32. A double longitudinal
dividing wall 33 is anchored with tongues 34 in a central
connecting region 35, with this connecting region 35 being stepped
back somewhat toward the inside, i.e. offset inward by an amount x
with respect to a lower boundary line 1 of the collecting box 31.
As a result, the cross sections of the longitudinal ducts 36, 37
are approximated to the circular shape beyond the three-quarter
circle (270 degrees). Nevertheless, the set-back central connecting
region 35 and the double longitudinal dividing wall 33 form a right
angle. This cross sectional shape thus provides a higher degree of
compressive strength for the collecting box 31.
[0028] All the exemplary embodiments described above are suitable
and advantageous for high internal pressures and thus also for a
coolant circuit of a motor vehicle air conditioning system which is
operated with CO.sub.2.
LIST OF REFERENCE NUMERALS
[0029] 1 Gas cooler [0030] 2 Collecting box [0031] 3 Flat tube
[0032] 4 Opening [0033] 5 Longitudinal duct [0034] 6 Longitudinal
chamber [0035] 7 Longitudinal dividing wall [0036] 8 Sheet metal
strip [0037] 9 Longitudinal edge [0038] 10 Longitudinal edge [0039]
11 Tongue [0040] 12 Tongue [0041] 13 Cutout [0042] 14 Central
connecting region [0043] 15 Notch, U-shaped [0044] 16 Gap [0045] 17
Gap [0046] 20 Gas cooler [0047] 21 Collecting box [0048] 21a
Longitudinal chamber [0049] 21b Longitudinal chamber [0050] 22 Flat
tubes [0051] 23 Tongue [0052] 24 Cutout [0053] 25 Longitudinal
dividing wall [0054] 26 Opening [0055] 27 Notch [0056] 28 Gap
[0057] 30 Gas cooler [0058] 31 Collecting box [0059] 32 Flat tube
[0060] 33 Longitudinal dividing wall [0061] 34 Tongues [0062] 35
Central connecting region [0063] 36 Longitudinal duct [0064] 37
Longitudinal duct [0065] 38 Gap
* * * * *