U.S. patent application number 09/833620 was filed with the patent office on 2001-10-18 for condenser for a vehicle air-conditioning system.
This patent application is currently assigned to BEHR GmbH & Co.. Invention is credited to Burk, Roland, Mittelstrass, Hagen, Staffa, Karl-Heinz.
Application Number | 20010029748 09/833620 |
Document ID | / |
Family ID | 7638709 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029748 |
Kind Code |
A1 |
Burk, Roland ; et
al. |
October 18, 2001 |
Condenser for a vehicle air-conditioning system
Abstract
In a condenser for an air-conditioning system, in particular for
an air-conditioning system of a motor vehicle, there is provision
for a collector (15) to be formed from a plurality of
series-connected tubes (18) which extend between header tubes (10,
11) and the cross section of which is a multiple of the cross
section of the flat tubes (13).
Inventors: |
Burk, Roland; (Stuttgart,
DE) ; Mittelstrass, Hagen; (Bondorf, DE) ;
Staffa, Karl-Heinz; (Stuttgart, DE) |
Correspondence
Address: |
Richard L. Schwaab
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Assignee: |
BEHR GmbH & Co.
|
Family ID: |
7638709 |
Appl. No.: |
09/833620 |
Filed: |
April 13, 2001 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
F28D 2021/0084 20130101;
F28F 9/0212 20130101; F28F 1/022 20130101; F25B 2500/01 20130101;
F28F 2210/08 20130101; B60H 1/3227 20130101; F28D 1/05391 20130101;
F25B 40/02 20130101; F25B 39/04 20130101; F25B 2339/044
20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 14, 2000 |
DE |
100 18 478.2 |
Claims
what is claimed is:
1. A condenser for an air-conditioning system comprising: a) a pair
of headers; b) a finned tube block comprised of a plurality of flat
tubes extending between said headers, wherein the tube block
includes a plurality of first flat tubes having a first tube
cross-section; and c) a collector integrated into said finned tube
block, said collector comprising a plurality of second flat tubes
having a second tube cross-section, wherein said second tube
cross-section is a multiple of at least twice as large as said
first tube cross-section, and wherein said second tubes are
connected to the headers to provide serial flow through said second
tubes.
2. A condenser for an air-conditioning system according to claim 1,
wherein said finned tube block further comprises corrugated fins
between said flat tubes.
3. A condenser for an air-conditioning system according to claim 1,
wherein said plurality of first tubes are connected to the headers
in parallel with one another.
4. A condenser for an air-conditioning system according to claim 1,
wherein said cross section of said second tubes is five times to
eight times greater than said cross section of said first
tubes.
5. A condenser for an air-conditioning system according to claim 4,
wherein said collector comprises a volume sufficient to contain
from about 150 g to about 400 g of refrigerant.
6. A condenser for an air-conditioning system according to claim 1,
wherein said headers comprise transverse walls subdividing said
headers such that said plurality of second tubes are connected in
series.
7. A condenser for an air-conditioning system according to claim 1,
wherein said plurality of second tubes further comprise at least
one of a plurality of internal ribs and internal dividing walls for
forming sub-passageways, for improving compression strength and
increasing heat transfer surface area.
8. A condenser for an air-conditioning system according to claim 1,
wherein said plurality of second tubes are positioned below said
plurality of first tubes.
9. A condenser for an air-conditioning system according to claim 1,
wherein said plurality of second tubes are positioned above said
plurality of first tubes.
10. A condenser for an air-conditioning system according to claim
9, wherein said finned tube block includes a condensation region
comprised of said first tubes positioned below said plurality of
second tubes, and wherein refrigerant passes through said tubes in
a direction from bottom to top of the condenser.
11. A condenser for an air-conditioning system according to claim
1, wherein the finned tube block further comprises a supercooling
region downstream of said collector.
12. A condenser for an air-conditioning system according to claim
11, wherein said supercooling region comprises a plurality of flat
tubes connected in parallel to one another.
13. A condenser for an air-conditioning system according to claim
12, wherein said flat tubes of said supercooling region are of
approximately the same dimension as said first tubes.
14. A condenser for an air-conditioning system according to claim
11, wherein said supercooling region is arranged in a middle
portion of the condenser, the supercooling region is positioned
above the plurality of second tubes and is connected to the
plurality of second tubes by a bypass.
15. A condenser for an air-conditioning system according to claim
14, wherein said supercooling stage is positioned in said condenser
at a point of optimum ventilation.
16. A condenser for an air-conditioning system according to claim
14, wherein said bypass comprises: a) transverse walls in one of
said headers; and b) a tube passing through said transverse
walls.
17. A condenser for an air-conditioning system according to claim
14, wherein said bypass comprises a double tube section in one of
said headers.
18. A condenser for an air-conditioning system according to claim
1, wherein the lateral dimension of said second tubes is
approximately the same size as the lateral dimension of said first
tubes.
19. A condenser for an air-conditioning system according to claim
11 wherein said collector has a volume sufficient to contain an
amount of refrigerant encompassing a refrigerant fraction between
supercooled refrigerant containing essentially no vapor and
incompletely condensed refrigerant containing a vapor fraction of
up to about 15%.
20. A condenser for an air-conditioning system according to claim
11 wherein said collector and supercooling region have an air-side
exchange surface that comprises between 15% and 25% of the entire
air-side exchange surface of the condenser.
21. A condenser for an air-conditioning system according to claim
20, wherein said collector and supercooling region air-side
exchange surface comprises 20% of the entire air-side exchange
surface.
22. A condenser for an air-conditioning system according to claim
9, further comprising means for preventing refrigerant from flowing
back out of said collector to a compressor.
23. A condenser for an air-conditioning system according to claim
1, wherein said air-conditioning system comprises a motor vehicle
air-conditioning system.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a condenser for an air-conditioning
system. In particular the invention relates to a condenser for an
air-conditioning system of a motor vehicle. The condenser of the
invention comprises lateral header tubes and a finned tube block.
The finned tube block contains a section serving as a collector and
comprises flat tubes and corrugated fins.
[0002] In a known condenser of the type disclosed in FR-A 2776 759,
the collector is integrated as a reservoir into the finned tube
block. In a first embodiment, a section of flat tubes which are
connected in parallel and which correspond to the other flat tubes,
serves as the collector. In another embodiment, the collector
provided is only a single large-volume tube which projects beyond
the contour of the condenser on at least one side. In further
embodiments, flat tubes connected in parallel as well as an outer
tube are provided. The outer tube is parallel to and has a larger
cross section than the flat tubes. In this known construction,
phase separation between liquid and vaporous refrigerant takes
place in the section serving as a collector or reservoir. During
transverse accelerations of the vehicle, for example, during
cornering, the liquid level changes. These changes in liquid level
may lead to an uneven cooling process or even to breakdowns in the
cooling process, particularly when refrigerant has already been
lost after a lengthy operating period. In a reservoir or collector
of small cross-section flat tubes connected in parallel, the loss
of refrigerant during lengthy operational periods is practically
unavoidable. Even in the case of relatively low refrigerant losses,
the losses lead to the displacement of supercooling to a relatively
great extent, thereby impairing the cooling capacity of the air
conditioning system. This displacement of supercooling may go so
far that supercooling is no longer achieved at all within the
condenser.
SUMMARY OF THE INVENTION
[0003] An object of the present invention is to provide an improved
condenser, especially for use in automotive air-conditioning
units.
[0004] A further object of the invention is to integrate a
collector into the finned tube block of a condenser, in such a way
that transverse accelerations have no effect on the cooling
capacity and that refrigerant losses do not have too great an
effect on condenser function.
[0005] In accomplishing the objects of the invention, there has
been provided, according to one aspect of the invention, a
condenser for an air-conditioning system comprising: a) a pair of
headers; b) a finned tube block comprised of a plurality of flat
tubes extending between the headers, wherein the tube block
includes a plurality of first flat tubes having a first tube
cross-section; and c) a collector integrated into the finned tube
block, the collector comprising a plurality of second flat tubes
having a second tube cross-section, wherein the second tube
cross-section is a multiple of at least twice as large as the first
tube cross-section, and wherein the second tubes are connected to
the headers to provide serial flow through the second tubes.
[0006] Further objects, features and advantages of the invention
will become apparent from the detailed description of preferred
embodiments that follows, when considered together with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 shows a frontal view of a condenser according to the
invention.
[0008] FIG. 2 shows a partial section through the region of a
collector of the condenser of FIG. 1 on a larger scale.
[0009] FIG. 3 shows a view of a condenser according to the
invention, with a throughflow direction from bottom to top.
[0010] FIG. 4 shows a view of a condenser according to the
invention with a supercooling stage arranged in the middle
region.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] According to the invention a collector is formed from a
plurality of tubes which are connected in a series and which extend
between the header tubes. The cross section of the plurality of
tubes is a multiple of the cross section of the other flat
tubes.
[0012] The condenser design of the present invention deliberately
dispenses with phase separation. Surprisingly, it was found that
good functioning is maintained despite dispensing with phase
separation. The present invention takes advantage of the fact that
as warmth is extracted from the condensing refrigerant, the density
of the two phase mixture changes significantly as it approaches the
saturated liquid state. The large density gradient region ends at
the point where condensation has ended and supercooling commences.
The refrigerant buffer volume received in the collector is
distributed to a plurality of tubes connected in a series.
Depending on the position of the large density gradient region,
this results in a sufficiently different filling of the condenser
with refrigerant without displacing the boundary of the beginning
of supercooling in the surface of the condenser to too great an
extent. The collector simultaneously functions as a supercooling
stage, when it can receive a large enough quantity liquid
refrigerant, i.e., about 150 g to about 400 g depending on the size
of the air conditioning system, and when air-side finning for heat
dissipation is assigned to the volume of refrigerant.
[0013] In another embodiment of the invention, a supercooling stage
with a plurality of flat tubes is provided following the collector.
It is thereby possible to achieve a kind of plateau for
supercooling.
[0014] In a further embodiment of the invention, the tubes of the
collector are rectangular tubes with inner fins and/or with a
plurality of walls forming sub-passageways. This improves
compressive strength while simultaneously increasing the heat
transmission surface in contact with the refrigerant.
[0015] According to an additional embodiment of the invention a
supercooling stage following the collector and arranged above the
collector is provided. It is thereby possible to shift the
supercooling stage into a region of the frontal face of a vehicle
which is not shielded by front-end structures, such as bumpers or
the like.
[0016] In yet another embodiment of the invention, a condensation
stage arranged below the collector is provided. This condensation
stage is further arranged for a predetermined refrigerant flow
direction going from the bottom toward the top. This provides the
advantage that, without special design measures, the supercooling
stage formed by the collector or the supercooling stage following
the collector may be arranged at the top in a region through which
the air flowing onto the frontal face of a vehicle or of the
condenser flows effectively. The air flows effectively since this
region is not covered by front-end structures, such as bumpers or
the like.
[0017] Further features and advantages in the invention may be
gathered from the following description of the exemplary preferred
embodiments and accompanying drawings.
[0018] The condenser illustrated in FIG. 1 is designed as a
so-called flat-tube condenser. It has two lateral header tubes 10,
11 which are assembled from sheet-metal profiles, as is known, for
example, from DE 43 19 293 C2. A finned tube block 12 composed of
flat tubes 13 and of corrugated fins 14 located between them is
arranged between the header tubes 10, 11. The design of the
condenser is, in this respect, essentially in accordance with the
construction of DE 43 19 293 C2. The essential difference is that a
collector arranged parallel to one of the header tubes 10, 11 has
been dispensed with. Instead, collector 15 is integrated into the
finned tube block 12 of the condenser as explained below.
[0019] The header tube 10 is provided, at the top, with a supply
connection 16 for vaporous refrigerant and, in the region of its
lower end, with a discharge connection 17 for liquid refrigerant.
The vaporous refrigerant passes into the flat tubes 13 and
increasingly condenses. About the lower fifth of the total height
of the condenser is designed as a collector 15 which simultaneously
fulfils the function of a supercooling stage. The region of the
collector 15 is composed of large-volume tubes 18 which are
connected in a series, i.e., through which the flow passes in a
serpentine manner. For this purpose, the header tubes 10, 11 are
subdivided respectively by transverse walls 19, 20. The tubes 18,
which preferably have a cross section of the order of magnitude of
five times to eight times the free cross section of the flat tubes
13, are sized in such a way that the collector can receive a
sufficient quantity of liquid refrigerant, i.e., about 150 g to 400
g. Corrugated fins 14 are arranged between the tubes 18 for further
condensation and supercooling of the refrigerant.
[0020] The design according to the invention deliberately dispenses
with phase separation, so that the tubes 18, in order to improve
the compression strength and to increase the heat transmission
surface, can be provided with a plurality of inner fins and/or
chambers, as illustrated in FIG. 2.
[0021] The concept implemented by the present invention makes use
of the fact that the density of the two-phase mixture changes
significantly as heat is further extracted from the increasingly
condensing refrigerant and as the saturated liquid state is
approached. The region of the large density gradient ends at the
point where condensation has ended and supercooling commences.
Since the buffer volume is distributed to a plurality of tubes 18
of larger cross section and which are connected in series, this
results in a sufficiently different filling of the condenser with
the refrigerant, depending on the position of the region of the
large density gradient. The boundary of the beginning of
supercooling is displaced to a relatively slight extent within the
finned condenser network.
[0022] Since phase separation has been deliberately dispensed with
in the condenser design according to the invention, the entire
condenser can be installed in a reversed configuration, such that
the collector 15 is located at the top and the flow then passes
through the condenser from the bottom upward. What is then achieved
thereby is that the collector 15 and consequently, above all, the
supercooling stage formed by the collector is located in the upper
and usually better ventilated region. In this case, measures should
be taken, by means of which liquid refrigerant is prevented from
flowing back to the compressor after the latter has been switched
off. For example, this may be achieved by a supply line 23' which
leads from the compressor to the condenser in a siphon-like manner,
as indicated by dashes in FIG. 3.
[0023] A condenser with a throughflow direction from the bottom
upward is shown in FIG. 3. In this exemplary embodiment, a finned
tube block 12 composed of flat tubes 13 and of corrugated fins 14
arranged between them is likewise provided between two header tubes
21, 22. The header tube 22 is provided at its lower end with an
inflow 23 for vaporous refrigerant. The header tube 21 has at its
upper end an outlet 24 for liquid supercooled refrigerant. The
finned tube block 12 formed from flat tubes 13 and corrugated ribs
14 is followed by a collector 25 which is formed from a plurality
of tubes 26 connected in series and corrugated fins 14 located
between them. The header tubes 21, 22 are subdivided by transverse
walls 27 and 28 in this region, in order to achieve a series
connection of the tubes 26.
[0024] The collector 25 is followed by a supercooling stage 29
which is formed from a plurality of flat tubes 13 connected in
parallel and corrugated fins 14 arranged between them.
[0025] Despite variation in the filling quantity, in order to
obtain an obliquely plateau-like supercooling profile, it is
expedient if half the air-side exchange surface of the collector
and supercooling zone is provided with large-volume tubes 26 and
half with small-volume flat tubes 13. The air-side heat exchange
surface of the collector and supercooling region is typically
between 15% and 25% and preferably about 20% of the entire air-side
exchange surface of the condenser. The flow pass through the flat
tubes 13 in parallel because of the smaller cross-sectional
surface. The dimension of the cross section of the large-volume
tubes 26 is such that the amount of refrigerant (difference in
mass) contained in the collector represents a refrigerant fraction
encompassing partially condensed refrigerant between supercooled
liquid (no vapor fraction) and incompletely condensed refrigerant
having a vapor fraction up to 15%, preferably from 10% to 15%. This
represents the desired refrigerant buffer quantity and corresponds
to the refrigerant in the region of the large density gradient. The
calculation of this buffer quantity may be based on a density
difference of about 0.7 kg/dm.sup.3. In order to buffer a quantity
of 250 g of refrigerant, a total volume of 333 cm.sup.3 is then
required for the collector. This total volume consists of the inner
volumes of the tubes 26 and of the associated volume of the
sections of the lateral header tubes 21, 22.
[0026] The embodiment according to FIG. 4, also shows a condenser
with a collector 15 integrated into the finned tube block 12. The
collector 15, composed of the larger-volume tubes 18 with
corrugated fins 14 located between them, is followed by a
supercooling stage 30 with narrow flat tubes connected in parallel.
This supercooling stage is connected to the collector 15 by means
of bypass ducts and, in the exemplary embodiment, is located
approximately at condenser mid-height. The height at which the
supercooling stage 30 is arranged may be varied as desired, so that
it can be placed at the point of best ventilation. In the header
tube 31 on the left in the drawing, the partitions 32 arranged
between the tubes 18 are pierced by a tube 33 leading to a section
of the header tube 31 which is limited by partitions 34 and which
is already an integral part of the supercooling stage 30.
[0027] The header tube 35, on the right in the drawing, possesses,
in the region of the supercooling stage 30, a double-tube section
36, one tube of which continues the header tube 35, while the inner
section receives the flat tubes of the supercooling stage 30. The
same design concept of a refrigerant bypass may, of course, also be
implemented on both sides of the condenser.
[0028] The disclosure of German Patent Application No. 100 18
478.2, filed Apr. 14, 2000, is hereby incorporated by reference in
its entirety.
* * * * *