U.S. patent application number 11/697155 was filed with the patent office on 2007-12-20 for internal heat exchanger with calibrated coil-shaped fin tube.
Invention is credited to Pavel Bartos, Zdenek Fidler, Roman Heckt, Thomas Klotten, Stephan Koster.
Application Number | 20070289723 11/697155 |
Document ID | / |
Family ID | 38513522 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070289723 |
Kind Code |
A1 |
Koster; Stephan ; et
al. |
December 20, 2007 |
INTERNAL HEAT EXCHANGER WITH CALIBRATED COIL-SHAPED FIN TUBE
Abstract
An internal heat exchanger unit for use in refrigerant circuits
of automotive air conditioning systems. The internal heat exchanger
includes a casing within which is located an accumulator, spaced
thereapart so as to define a gap between the two components.
Located within the gap is a coil-shaped fin tube. The fins of the
fin tube include bend end portions at spaced apart locations about
the fins, and the bent end portions defining an outer dimension of
the fins that substantially corresponds to the gap width.
Inventors: |
Koster; Stephan;
(Langerwehe, DE) ; Heckt; Roman; (Aachen, DE)
; Klotten; Thomas; (Koln, DE) ; Fidler;
Zdenek; (Koprivnice, CZ) ; Bartos; Pavel;
(Novy Jicin, CZ) |
Correspondence
Address: |
VISTEON
C/O BRINKS HOFER GILSON & LIONE
PO BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
38513522 |
Appl. No.: |
11/697155 |
Filed: |
April 5, 2007 |
Current U.S.
Class: |
165/145 |
Current CPC
Class: |
F25B 40/00 20130101;
F25B 2309/061 20130101; B60H 1/00499 20190501; F25B 43/006
20130101; B60H 1/00492 20130101; F25B 9/008 20130101; B60H 1/00328
20130101; F28F 2240/00 20130101; F25B 2400/051 20130101; F28D 7/024
20130101; F25B 2500/18 20130101; F28F 1/24 20130101 |
Class at
Publication: |
165/145 |
International
Class: |
F28F 9/22 20060101
F28F009/22 |
Foreign Application Data
Date |
Code |
Application Number |
May 6, 2006 |
DE |
10 2006 017 432.1 |
Claims
1. An internal heat exchanger unit for use in refrigerant circuits
of air conditioning systems in automotive vehicles, comprising: a
casing having a casing side wall limited by top and bottom cover
plates; an accumulator located in the casing, the accumulator
having an accumulator side wall spaced apart from the casing side
wall and defining a gap therebetween having a gap width x, the
accumulator configured to receive liquid refrigerant at low
pressure; a coil-shaped fin tube located in the gap between the
casing and the accumulator and configured to receive refrigerant at
high pressure, the coil-shaped fin tube including a tube and a
plurality of fins located thereon, the fins including bend end
portions at spaced apart locations about the fins, the bent end
portions defining an outer dimension of the fins that substantially
corresponds to the gap width x, the bent end portions further
defining a bent length z.
2. The internal heat exchanger of claim 1 wherein the bent end
portions of the fins are bent in an axial direction relative to the
tube.
3. The internal heat exchanger of claim 1 wherein the bent end
portions define bearing surfaces.
4. The internal heat exchanger of claim 3 wherein the bearing
surfaces are bearing surfaces between the casing and the bent end
portions and the accumulator and the bent end portions.
5. The internal heat exchanger of claim 3 wherein the coil-shaped
fine tube has a plurality of coils and the bearing surfaces are
bearing surfaces between the adjacent coils, the bearing surfaces
defining surfaces configured to permit sliding of one coil relative
to the adjacent coil.
6. The internal heat exchanger of claim 1 wherein the fins include
at least two bent end portions.
7. The internal heat exchanger of claim 1 wherein the fins include
four bent end portions.
8. The internal heat exchanger of claim 1 wherein the fins are
arranged concentric on the tube.
9. The internal heat exchanger of claim 1 wherein the fins are
generally annular in shape.
10. The internal heat exchanger of claim 1 wherein the fins have a
height h from an exterior surface of the tube, the height h being
about 5% of the gap width x.
11. The internal heat exchanger of claim 1 wherein the fins are
dimensioned such that a distance between an exterior surface of the
tube and an interior surface of the casing and/or an exterior
surface of the accumulator is about 5% of the gap width x.
12. The internal heat exchanger of claim 1 wherein the bent length
z is at least equal to half of a length L1, where L1 is the
distance between adjacent fin surfaces.
13. The internal heat exchanger of claim 1 wherein the fins are
spaced apart on the tube by a distance t, whereby a ratio of the
distance t to the fin height h is in the range of about 1 to 4.
14. The internal heat exchanger of claim 1 wherein the bent ends of
the fins are generally T-shaped.
15. The internal heat exchanger of claim 1 wherein the bent ends of
the fins are upset ends.
16. The internal heat exchanger of claim 1 wherein the side wall of
the casing includes an insulating layer.
17. The internal heat exchanger of claim 1 wherein the side wall of
the accumulator includes an insulating layer.
18. The internal heat exchanger of claim 1 wherein the top and
bottom cover plates of casing are provided with connections for the
refrigerant at low pressure and high pressure.
19. The internal heat exchanger of claim 1 wherein the fins are
arranged on the tube so as to define passageway between the fins
for refrigerant vapor at low pressure that is
cross-countercurrently to the refrigerant at high pressure within
the tubes.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The invention relates to an internal heat exchanger with a
calibrated coil-shaped fin tube, which together with a refrigerant
accumulator, forms a unit used in refrigeration circuits of the air
conditioning of automotive vehicles.
[0003] The combined accumulator with internal heat exchanger
combines the functionalities of both components in one unit, a
combined component. The combined component is used preferably in
mobile R744-refrigeration plants. Compared to the single
components, the compact combined component adapts better to the
limited space in the engine compartment. It is also advantageous as
to costs for the general system of the mobile refrigeration
plant.
[0004] 2. Related Technology
[0005] In a refrigeration machine or heat pump, the accumulator is
arranged downstream of the evaporator and is intended to take
refrigerant filling quantities varying due to varying operation
conditions, thereby holding out a refrigerant reserve in order to
make up for leakage losses occurring over the maintenance interval.
The internal heat exchanger has the function to transfer heat
within the system for overcooling from the high from the
high-pressure side to the low-pressure side, which thereby is
heated.
[0006] The combination of collector and internal heat exchanger can
be configured as to containers arranged concentrically. The inner
container functions as refrigerant collector. In the annular gap
between the inner container and the outer container, there is the
internal heat exchanger.
[0007] The state-of-the-art knows varied combinations of internal
heat exchangers and accumulators.
[0008] From DE 311 19 440 A1, an internal heat exchanger and
accumulator is known where the refrigerant collects in the
accumulator at low pressure and is then thermally contacted with
high-pressure flow. The heat exchanger coil containing the
high-pressure flow consists of coil-shaped bundles of smooth pipes.
On the inner side of the coil bundle, the refrigerant passes
through the pipe coil of the internal heat exchanger at high
pressure, and on the outer side, the refrigerant vapor flows around
the pipe coil at low pressure. It applies as a matter of principle
that, in the refrigerant circuit, both sides are admitted with
equal mass flows. For thermodynamic reasons, the low pressure side
is considerably more problematic than the high-pressure side as to
the pressure loss and heat transmission. The transport quantities
of carbon dioxide (and density as well) on the low-pressure side
result in a larger heat transmission area and a larger flow
cross-section. The disadvantage of this internal heat exchanger
with a high-pressure pipe is that the refrigerant circulating
countercurrently produces pressure losses on the low-pressure side
that are too high and the available heat exchanger surface is too
small. The design structure with several parallel pipes causes that
the low-pressure side flows cross-countercurrently relative to the
high-pressure side. The pressure loss on the low-pressure side
clearly decreases while the heat exchanger area clearly increases.
However, manufacture of an internal heat exchanger with bundled
smooth pipes is expensive and the produced heat transmission
packets are difficult to reproduce as to the exact determination of
the gaps decisive for the flow cross-sectional area.
[0009] DE 101 61 886 A1 describes an internal heat exchanger where,
in the space between the walls of an inner and an outer container,
a helical pipeline (a coil-shaped internal heat exchanger) is
provided. A first fluid passes through the helical pipeline while a
second fluid passes through two gaps between the walls and the
helical pipeline. The gap widths are chosen to reduce the pressure
drop without impairing the heat exchanger capacity, or to maximize
heat transmission, respectively.
[0010] DE 35 43 230 A1 also describes a coil-shaped pipeline
functioning as heat exchanger. A refrigeration unit is disclosed
where a liquid refrigerant receiver, a drawn-in vapor refrigerant
collector and a refrigerant heat exchanger are integrated to form a
unit. The integrated unit is limited by an approximately
cylindrical outer casing which forms the drawn-in vapor refrigerant
collector, and is provided with a refrigerant vapor inlet and a
refrigerant vapor outlet. Further, the integrated unit includes as
inner casing, also approximately cylindrical, which is located
within the upper part of the outer casing forming an annular space
between itself and the outer casing. The inner casing serves a
liquid refrigerant receiver having a liquid refrigerant inlet to be
connected to the condenser outlet thereof and another outlet
located within the inner casing. Further, the integrated unit
includes a heat exchanger coil, which is located in the annular
space between the inner and outer casings, on the inlet side
connected to the outlet of the liquid refrigerant receiver and on
the outlet side leading to an outlet to be connected to the
evaporator inlet.
[0011] Common to all the solutions described above is that the
warmer high-pressure refrigerant passes the pipe coils on the inner
side and the colder low-pressure refrigerant flows around the pipe
coils on the outer side. Mass flow is equal on both sides so that a
considerably bigger volume flow results for the low-pressure side.
On the low-pressure side, however, the pressure loss must be kept
comparatively low for thermodynamic reasons, which requires
relatively wide cross-sections. At the same time, because of the
low density and the concomitant low heat transmission capacity of
the refrigerant, a large exchange area must be provided.
[0012] Requirements like that are best met by a coil-shaped fin
tube seen in DE 35 43 230 A1. As with all above mentioned
solutions, the refrigerant collector and the internal heat
exchanger are combined by two concentric containers, whereby the
coil-shaped fin tube which functions as the internal heat exchanger
is placed between the inner and the outer container. This
construction, however, has some design disadvantages.
[0013] If the fin heads do not bear against the outer wall of the
inner container and the inner wall of the outer container, one, or
two, respectively, annular gaps without exchanger area are formed,
starting from the internal heat exchanger. Then, low-pressure
bypass flows will pass through these annular gaps, significantly
impairing the efficiency of the internal heat exchanger.
[0014] If the fin heads do not bear against the annular gap
surfaces, then under normal vehicle vibration conditions the tube
coil starts to vibrate, continuously beating against the container
walls, which leads to considerable noise development.
[0015] If the fin tubes themselves and the tube coils are
manufactured true to size in order to avoid annular gaps between
the fin heads and the coil walls, at a very great expense,
considerable problems are created particularly in series production
when the components are assembled. Assembling under the condition
of such a little allowance between the tube coils and annular gaps
is additionally made even more difficult in that the tube coils
with the fines get caught on each other when they are axially
assembled. Adapting the coil diameter, for example, by manually
rotating the tube coil during the assembling process gets nearly
impossible.
[0016] DE 195 46 489 A1 discloses a heat exchanger with a fin tube
where, in the contact areas, in order to avoid that two coil
flights situated adjacent each other will engage into each other,
the fins of at least one coil flight are rectangularly bent at
approximately half their radial extension.
[0017] Naturally, the fin heads are pointed relatively sharply.
Whether there is a gap or not between the fin heads and the
container walls, due to the natural vehicle vibrations, the fins
can produce notches in the container walls. The notches may
possible lead to failure of the component.
SUMMARY OF THE INVENTION
[0018] An objective of the invention is to provide an internal heat
exchanger with accumulator for refrigerant circuits, whereby the
above mentioned disadvantages of the state-of-the-art the heat
exchangers are eliminated, which is configured to be easily and
cost-effectively manufactured, which provides a large heat
transmission area for the low-pressure flow, which creates less
flow losses of the low-pressure flow, and which avoid bypass
flows
[0019] In achieving the above, the invention provides an internal
heat exchanger with a calibrated coil-shaped fin tube. Together
with an accumulator the heat exchanger forms a unit and is used in
refrigerant circuits of, particularly, motor vehicle air
conditioning units. The internal heat exchanger includes a casing
with a top cover plate and a bottom cover plate. Within the casing
there is provided an accumulator for the low pressure liquid
refrigerant. A coil-shaped fin tube, through which passes high
pressure refrigerant, is located in an annular gap (with gap width
x) between the accumulator and the casing. The fins are annular and
radially arranged on the fin tube so that the refrigerant vapor is
readable at low pressure between the fins of the fin tube
cross-countercurrently and, possibly, cocurrently to the high
pressure refrigerant. According the invention, the fins are
calibrated to adopt the dimensions of the annular gap by bending
the fins at their distal ends. The coil-shaped fin tube is
integrated into the annular gap such that fin heads bear against
the inner and outer containers, that means bearing surfaces of the
fin heads form in the radial direction.
[0020] More specifically, the fins are bent-off at their distal end
by a defined length, length z, whereby the bent length z of the fin
is smaller than or equal to the distance between adjacent fins.
Further, the surfaces of the fin heads in the region of contact
with the walls of the casing or accumulator are larger.
[0021] The internal heat exchanger according to the invention is
advantageous in that the fabrication and manufacture processes can
be handled better and carried out more effectively, compared with
the use of several smooth tubes that must be formed to establish a
heat transmission bundle.
[0022] The present invention also results in a significantly
reduced pressure loss. The fins of the fin tube serve to maintain
the distance between the tube and the accumulator, as well as
between the tube and the casing. Refrigerant vapor flows between
the fins into the so formed channels. Based on the dedicated
establishing of the fin height the gap and, hence, the volume flow
or the flow pressure loss, respectively, become calibratable. This
results in a reproducible design of the gap width.
[0023] The internal heat exchanger according to the invention can
be manufactured at a lower price, as compared to an internal heat
exchanger formed of a bundle of smooth tubes. In addition, the
internal heat exchanger according to the invention allows a higher
efficiency of heat transmission to be reached.
[0024] The concept of the invention consists in that the fin tube
coil is calibrated by bending the ends of the fins so as to take
the dimensions of the annular gap in order to avoid bypass flows
and enlarge the surfaces of the fin heads in contact with the walls
defining the annular gap.
[0025] Calibration of the inner and outer diameters of fin tube
coils by partially bending the fin heads in radial coil direction
results in that the fin tube can itself be manufactured to
relatively large tolerances. The resulting accuracy of fit prevents
bypass flow around the fin tube coil from developing, so that
material expenditure for the internal heat exchanger is reduced
because the same heat capacity is reached by less heat transmission
surface. In addition, the resulting accuracy of fit prevents the
fin tube coil from vibrating, hence from developing undesirable
noise.
[0026] Further, the bending of the fins results in the ends of the
fins bearing flat against the outer wall, i.e., the wall of the
casing, and/or the internal wall of the annular gap, i.e., the wall
of the accumulator. This avoids damage (in form of notches) to the
container walls due to vehicle vibrations.
[0027] In another advantageous embodiment, the fin heads are
partially bent-off not only in the radial direction, but also in
the axial direction. As such, bearing surfaces form between
individual coils on which the coils can slide relative to one
another, without hooking together. The internal heat exchanger is
preferably configured as fin tube coil with fin heads bent-off in
four locations. In such a construction, the fin heads are bent on
opposing sides in the radial and axial directions.
[0028] The bending of the fin heads in the axial direction of the
fin tube coil results in individual coils bear against the bent
surfaces of adjacent coils and do not hook together. Assembling of
the component is made possible also with fin tube coils made true
to size. Another advantage consists in that therefore, the height
of the fin tube coil is exactly defined and not dependent on the
degree of hooking. Homogeneous distribution of the individual coils
over the height of the fin tube coil is ensured.
[0029] In yet another embodiment of the invention, annulus-shaped
fins are arranged concentric on the fin tube. In a preferred
embodiment, the annulus-shaped fins are dimensioned such that
between the end of the fins and the casing (and/or the
accumulator), a gap of 5% maximum relative to the gap width x is
established. The preferred height h of the annulus-shaped fins is
5% to 30% of the gap width value x.
[0030] The annulus-shaped fins are arranged at a distance t to each
other. By this, for the dimensional ratio between the distance t
and the fin height h a value from a range of one to four is chosen.
Preferably, the bent-off length z is at least half the length L1,
whereby the length L1 is the distance between two neighboring fin
surfaces.
[0031] In an alternative embodiment, an internal heat exchanger
with coil-shaped fin tubes, together with an accumulator, forms a
unit. The internal heat exchanger has a top cover plate and a
bottom cover plate. An accumulator is located in the casing for the
liquid refrigerant at low pressure. The coil-shaped fin tube, in
which passed the high pressure refrigerant, is located in the gap
between the accumulator and the casing.
[0032] The fins are arranged radially on the fin tube so that the
refrigerant vapor is readable, at low pressure, between the fins of
the fin tube cross-countercurrently and, possibly, cocurrently to
the refrigerant at high pressure. As opposed to the solution
previously described the fins are formed by upsetting so that
bearing surfaces in radial direction develop.
[0033] According to one advantageous embodiment, the inner surface
of the casing is equipped with an insulating layer. When the inner
cylinder is configured as high-pressure profile, also the inner
side of the internal cylinder may also be equipped with an
insulating layer. Another embodiment consists in the outer surface
of the accumulator being equipped with an insulating layer.
Preferably both the top and bottom cover plates of the casing are
provided with connections for the refrigerant at low and high
pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Further objects, features and advantages of this invention
will become readily apparent to persons skilled in the art after
review of the following description, with reference to the
drawings, in which:
[0035] FIG. 1 shows an internal heat exchanger with an accumulator,
in cross-sectional view;
[0036] FIG. 2 is a cross-sectional view, generally taken along line
2-2 in FIG. 1 showing the fin tube coil in it assembled
position;
[0037] FIG. 3a is a prior art construction of two neighboring fins
during axial assembling;
[0038] FIG. 3b illustrates two neighboring fins and tubes according
the present invention fins during axial assembling;
[0039] FIGS. 4a and 4b are end and side views, respectively, of a
portion of a fin tube with bent-off fins;
[0040] FIGS. 5a and 5b are end and side views, respectively, of a
portion of a fin tube with upset fins.
DETAILED DESCRIPTION OF THE INVENTION
[0041] In FIG. 1 an internal heat exchanger 100 with a coil-shaped
fin tube is shown; the heat exchanger 100, together with an
accumulator 10 forming a unit. The internal heat exchanger 100
includes a casing 2, which is preferably cylindrical, particularly
circular-cylindrical. The casing 2 is limited by a top cover plate
4 and a bottom cover plate 6. Integrated into the top cover plate 4
is a low-pressure inlet 12 and a high-pressure outlet 20.
Integrated into the bottom cover plate 6 is a low-pressure outlet
16 and a high-pressure inlet 18. The accumulator 10 is provided
concentrically in the interior of the heat exchanger 100 and is in
the form of a cylinder. A side wall 11 of the accumulator 10 is
closed at the bottom by a bottom cover plate 13 and at the top by a
top cover plate 15. In the top cover plate 15, there is provided an
opening for the low-pressure inlet 12 next to an opening configured
as overflow 14. The refrigerant, at high pressure, passes through
the coil-shaped fin tube 8, which extends from the bottom cover
plate 6 and is arranged in the gap (with gap width x) between the
accumulator 10 and the casing 2, coiling coaxially along the side
wall 11 of the accumulator 10, from bottom to top, and exits the
internal heat exchanger 100 via the high-pressure outlet 20 through
the top cover plate 4.
[0042] According to this embodiment to FIG. 1, the inner surface of
the cylindrical casing 2 is provided with an insulating layer 22.
According to another embodiment, the outer surface of the side wall
11 of the accumulator 10 may also be provided with an insulating
layer 24.
[0043] As seen in FIG. 2, a single calibrated fin tube coil 26 of
the coil-shaped fin tube 8, which according to the invention is
calibrated by bending of the ends or heads of the fins 28 located
on the tubes 29. The bent length z of the fin's ends can be set
unproblematically so that the inner diameter d and the outer
diameter D of the fin tube coil 26 can be fitted exactly to the
inner and outer diameters defining the annular gap between the
casing 2 and the accumulator 10. Such calibrating of the fin tube
coil 26 makes the bent fin heads 30 bear against the limiting side
wall 11 of the accumulator 10 and the limiting side wall 32 of the
casing 2r. Therefore, annular gaps for low-pressure side bypass
flows in the internal heat exchanger are avoided. Bearing of the
bent fin heads 30 also prevents the calibrated tube coil 26 from
vibrating, caused by the usual vehicle vibrations, and avoids
disturbing noise.
[0044] The bent fin heads 30 enlarge the bearing areas on the
limiting side walls 11, 32 so that no notches, due to the ends,
fins are created in the side walls 11, 32.
[0045] In FIGS. 3a and 3b, two neighboring fin tube coils are shown
during axial assembling of the component into the annular gap.
[0046] In FIG. 3a, the hooking of the tube coils into each other is
observed in a known assembly, inevitably caused during axial
assembly of the component. Adjusting the coil diameter by, for
example, manual action becomes impossible due to the coil's hooking
together. If fin tube coils that are manufactured true to size are
used, assembling the components may become impossible.
[0047] In FIG. 3b, the bent fin heads 30 are bent generally in the
axial direction of the tubes 29. Therefore, bearing surfaces 36 are
formed between adjacent ones of the single fin tube coils 26 on
which the fin tube coils 26 can axially, transversely and radially
slide relative to each other without hooking together. Adaptation
of the diameter of the fin tube coil 26 during assembly is no
problem for the fins 28 with the fin heads 30 bent in axial
direction of the tubes 29, also when manufactured true to size.
[0048] In FIGS. 4a and 4b, end and side views of a portions of the
coil-shaped fin tube 8 is shown, where the bent fin heads 30 are
bent at four bending points 38, at 90.degree. intervals, and
provided with a length z. The heads 30 are bent at both axial and
radial locations, relative to longitudinal axis of the heat
exchanger 100. The fins 28 are arranged concentric to the tube 29
so that the values of the fin height h are equal on both sides of
the tube 29. The tube 29 itself has a wall with the wall thickness
s, as well as an inner diameter d1 and an outer diameter d2. The
complete coil-shaped fin tube 8 has a clear diameter d3. The
cross-sectional area passed by the high-pressure refrigerant
follows from the channel formed by two neighboring fins 14. The
fins 14 are arranged on the tube 29 with a distance whereby L1 is
the distance of neighboring opposing fin surfaces, and L2 is the
fin 28 thickness.
[0049] An alternative forming measure to provide bearing surfaces
in radial direction is upsetting of the ends of the fins 40. A
detailed view of a coil-shaped fin tube 8 with fins 40 upset at the
fin heads 42 is shown in FIG. 5b. FIG. 5a illustrates the fins 29
before the heads 42 have been subjected to upsetting. As seen
therein, the cross-section of the fins 40 is such that the fin
heads 42 form a general T-shaped configuration.
[0050] Of course, the invention is not limited to the embodiments
described and of which only one is illustrated in the accompanying
drawings. Modifications are possible, particularly from the point
of view of the composition of the various elements and by
substitution of technical equivalents, without thereby departing
from the scope of protection of the invention.
* * * * *