U.S. patent application number 11/286397 was filed with the patent office on 2007-05-31 for heat exchanger.
Invention is credited to Markus Wawzyniak.
Application Number | 20070119580 11/286397 |
Document ID | / |
Family ID | 38047809 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070119580 |
Kind Code |
A1 |
Wawzyniak; Markus |
May 31, 2007 |
Heat exchanger
Abstract
The invention is directed to a heat exchanger (10) having a
block (2) which includes a plurality of tubes (11) for conducting a
fluid therethrough. The heat exchanger also includes a collector
(5) having a tube base (4). The tubes have tube end sections (11)
and the tubes are inserted into the tube base so that the end
sections are accommodated therein and extend into the collector to
an insertion depth (x). The insertion depth (x) of the end sections
(11a) is variable. The heat exchanger is preferably used as an
evaporator in climate control systems for motor vehicles.
Inventors: |
Wawzyniak; Markus;
(Rochester Hills, MI) |
Correspondence
Address: |
WALTER OTTESEN
PO BOX 4026
GAITHERSBURG
MD
20885-4026
US
|
Family ID: |
38047809 |
Appl. No.: |
11/286397 |
Filed: |
November 25, 2005 |
Current U.S.
Class: |
165/174 ;
165/173 |
Current CPC
Class: |
F28F 9/0282 20130101;
F28D 2021/0085 20130101; F28F 9/04 20130101; F28D 1/05383
20130101 |
Class at
Publication: |
165/174 ;
165/173 |
International
Class: |
F28F 9/02 20060101
F28F009/02 |
Claims
1. A heat exchanger comprising: a block including a plurality of
tubes for conducting a fluid therethrough; a collector having a
tube base; said plurality of tubes having respective end sections;
said plurality of tubes being inserted into said tube base so as to
cause said end sections to be accommodated in said tube base and to
extend into said collector to an insertion depth (x); and, said
insertion depth (x) being variable.
2. The heat exchanger of claim 1, wherein said heat exchanger is an
evaporator.
3. The heat exchanger of claim 2, wherein said fluid is a two-phase
fluid.
4. The heat exchanger of claim 3, wherein said fluid is a
refrigerant.
5. The heat exchanger of claim 1, wherein said collector includes
at least one inlet chamber.
6. The heat exchanger of claim 5, wherein said inlet chamber has an
end face; and, said collector includes an injection opening for
passing said fluid into said header.
7. The heat exchanger of claim 5, wherein said inlet chamber,
viewed geodetically, is disposed above said block and said end
sections of said tubes communicate with said inlet chamber; and,
said tubes are mounted relative to said inlet chamber so as to
permit said fluid to flow downwardly through said tubes in a
direction corresponding to the direction of gravitational
force.
8. The heat exchanger of claim 5, wherein said inlet chamber,
viewed geodetically, is disposed below said block and said end
sections communicate with said inlet chamber; and, said tubes are
mounted relative to said inlet chamber so as to permit said fluid
to flow through said tubes upwardly in a direction opposite to the
direction of gravitational force.
9. The heat exchanger of claim 7, wherein said insertion depth (x)
decreases with increasing distance (a) of said end sections away
from said injection opening.
10. The heat exchanger of claim 8, wherein said insertion depth (x)
increases with increasing distance (a) of said end sections away
from said injection opening.
11. The heat exchanger of claim 1, wherein said insertion depth (x)
changes in accordance with a linear function.
12. The heat exchanger of claim 1, wherein said insertion depth (x)
changes in accordance with a nonlinear function.
13. The heat exchanger of claim 1, wherein said plurality of tubes
are apportioned into first and second sets of tubes through which
said fluid flows; and, said insertion depth (x) is variable at
least for said first set of tubes.
14. The heat exchanger of claim 1, wherein said tubes are
configured as flat tubes.
15. The heat exchanger of claim 14, wherein said flat tubes are
configured as multi-chamber tubes.
16. A climate control system comprising a heat exchanger; and, said
heat exchanger includes: a block including a plurality of tubes for
conducting a fluid therethrough; a collector having a tube base;
said plurality of tubes having respective end sections; said
plurality of tubes being inserted into said tube base so as to
cause said end sections to be accommodated in said tube base and to
extend into said collector to an insertion depth (x); and, said
insertion depth (x) being variable.
Description
BACKGROUND OF THE INVENTION
[0001] Heat exchangers, for example, refrigerant vaporizers, are
used in climate control systems for motor vehicles. These heat
exchangers include essentially a block of tubes through which a
refrigerant flows and which refrigerant is to be evaporated. Ribs
are provided and the air, which is to be cooled, is passed over
these ribs and is supplied to the interior of the vehicle. The
tubes are connected to collector compartments or distributor
compartments via which the refrigerant is supplied, redirected or
conducted away.
[0002] A problem, which occurs with all evaporators, is the uniform
distribution of the refrigerant, which is injected into the
evaporator, into all tubes. The refrigerant is expanded in an
expansion element directly in advance of entry into the evaporator
and is present at the injection location of the evaporator as a
two-phase mixture comprising a vaporous refrigerant and a liquid
refrigerant. If the evaporator tubes are not uniformly charged,
then there is a nonuniform evaporation and therefore a nonuniform
temperature distribution which effects the air end of the
evaporator and leads to a so-called stringiness of the air flow.
Furthermore, an increased pressure drop can develop in the
individual tubes which is damaging for the capacity of the
evaporator. These disadvantages are especially pronounced in the
thermal part-load operation which, on an annual average, usually
occurs most often, as opposed to the full-load operation. An
improvement of the refrigerant distribution not only increases
comfort but also reduces the power required and therefore the
consumption of fuel.
[0003] Various solutions are known wherein a uniform distribution
of the refrigerant to the individual tubes is strived for. In
German patent publication 4,422,178, a distributor element in the
form of an apertured body is mounted in the inlet region of the
evaporator. The refrigerant exits through the apertures and is
intended to then distribute uniformly. Additional suggestions for a
distribution of the refrigerant in the inlet region are suggested
in the following: German patent publications 197 19 250 and 197 19
257 and U.S. Pat. No. 6,199,401. Separate channels or distributor
tubes leading to the tubes and having refrigerant outlet openings
are provided. These suggestions are characterized by an increased
constructive complexity in the area of the inlet compartments of
the evaporator which increases the manufacturing costs.
[0004] Present-day flat tube evaporators are disclosed, for
example, in U.S. Pat. No. 6,449,979 or in international patent
publication WO 2005/047800 A1. These present-day flat tube
evaporators operate without such distributor means. The known flat
tube evaporators are configured in two rows and have respective two
double collector compartments wherein the tube end sections are
inserted. The injection of the refrigerant takes place from an end
face of a collector compartment into an inlet chamber. From there,
the refrigerant is distributed to the tubes and is redirected once
or several times in the evaporator block (multiple throughflow in
individual tube groups). These known flat tubes also lead a
nonuniform distribution of the refrigerant and the above-mentioned
disadvantages.
SUMMARY OF THE INVENTION
[0005] It is an object of the invention to provide a distribution
of the fluid as uniform as possible in a heat exchanger of the
above-mentioned type.
[0006] The heat exchanger of the invention includes: a block
including a plurality of tubes for conducting a fluid therethrough;
a collector having a tube base; a plurality of tubes having
respective end sections; the plurality of tubes being inserted into
the tube base so as to cause the end sections to be accommodated in
the tube base and to extend into the collector to an insertion
depth (x); and, the insertion depth (x) being variable.
[0007] According to the invention, the insert depth of the tubes in
the tube base is variable, that is, the tube end sections project
out of the tube base at different elevations. The heat exchanger is
advantageously configured as an evaporator and the fluid is
advantageously a two-phase fluid, especially, a refrigerant. In a
further advantageous embodiment, the evaporator has an inlet
chamber with at least an injection opening mounted in an end face.
The injection opening or openings can, in principle, also be
mounted at other locations, especially, at the longitudinal sides.
In an evaporator having an inlet region disposed topside, it is
advantageous that the insertion depths of the tube end sections
decrease with increasing distance from the location of the
injection. In an evaporator having an entry region at the lower
end, it is advantageous when the insertion depth increases with
increasing distance from the location of injection. The increasing
or decreasing insertion depth can advantageously take place as a
linear function or a nonlinear function.
[0008] It has been determined that the refrigerant flow increases
greatly with increasing distance from the location of injection up
to the tube farthest remote therefrom. More specifically, the
refrigerant flow is present in the region of the injection location
as an intensely turbulent mixture of refrigerant vapor and liquid
droplets. The refrigerant flow passes into a layered flow with
increasing distance from the injection location. For a horizontal
flow, a layer of liquid refrigerant and a layer of vaporous
refrigerant thereabove forms in the geodetically bottom-lying
region. The location of the transition from turbulent to layered
flow is dependent upon the amount of the refrigerant mass flow.
Because of varying insertion depths of the tubes, this phenomenon
of the refrigerant flow can be taken into account and an
approximately uniform distribution of the refrigerant is achieved
to the individual tube cross sections. The solution of the
invention is relatively easily realized and therefore cost
effective, that is, by simply utilizing different tube lengths
and/or insertion depths. It is possible that different insertion
depths, at least in a portion of the tubes, can be realized also
without different tube lengths when, for example, a compensation at
the other end of the corresponding tube is provided. The following
advantages are achieved: a uniform temperature distribution on the
air side; a uniform, lower pressure drop in the tubes; and, a
higher evaporator capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will now be described with reference to the
drawings wherein:
[0010] FIG. 1 is a section view of a flat tube evaporator according
to the prior art; and,
[0011] FIG. 2 is a section of an embodiment of the evaporator
according to the invention having variable tube insertion
depths.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0012] FIG. 1 is a cutaway view of an evaporator 1 as it is known
from the prior art, for example, from U.S. Pat. No. 6,449,979 or
from international patent publication WO 2005/047800 A1. The
evaporator 1 includes a block 2 of flat tubes 3. Ribs (not shown)
are mounted between these tubes over which air flows. The tubes 3
have tube ends 3a which are inserted into a tube base 4. The tube
base 4 is part of a collector 5 which has an injection tube 6
mounted at an end face and through which refrigerant is supplied to
the evaporator 1. The axis of the injection tube 6 is identified by
reference numeral 6a and this axis corresponds to the injection
direction of the refrigerant. The collector 5 includes an inlet
chamber 7 which is partitioned off relative to a neighboring
chamber by a partition wall 8. The refrigerant reaches the inlet
chamber 7 via the injection tube 6 and distributes from there to
the tubes 3. The refrigerant then flows from top to bottom in the
drawing, that is, in a direction corresponding to the direction of
gravitational force. Thereafter, the refrigerant is redirected in
the depth (in air flow direction) and/or in the width (transversely
to the air flow direction). In this way, the refrigerant vaporizes
in the tubes 3 and thereby effects a cooling of the air to be
climatized. In the known evaporator 1, the tube ends 3a have an
insertion depth which is characterized by the amount (x). The
amount (x), that is, the insertion depth, is the same for all tubes
3. Because of the changing refrigerant flow, there results a
nonuniform charging of the tubes 3 in the known evaporator 1 shown
in FIG. 1.
[0013] FIG. 2 shows an evaporator 10 according to an embodiment of
the invention. Here, the same parts have the same reference
numerals as in FIG. 1. The evaporator 10 includes an inlet chamber
7 having an injection tube 6 mounted at an end face and a tube base
4. The flat tubes 11 have tube end sections 11a which are inserted
at different insertion depths into the tube base 4. The upper edges
of the tube end sections 11a are connected via a straight line (f).
The distance of the tubes 11 from the end face of the injection
tube 6 is identified by reference character (a). The insertion
depth of the tube, which lies closest to the injection tube 6, is
identified by x.sub.max and the insertion depth of the flat tube
11, which is farthest away from the injection tube 6, is identified
by reference character x.sub.min. From FIG. 2, it can be seen that
the insertion depth (x) follows a linearly decreasing function (f)
over the distance (a).
[0014] The refrigerant flow, which enters horizontally through the
injection tube 6 into the inlet chamber 7, is present first as a
two-phase intensely turbulent mixture of refrigerant vapor and
refrigerant liquid droplets. With increasing distance (a) from the
injection tube 6, the refrigerant flow changes its state into a
layered flow which comprises a lower layer of liquid refrigerant
and a layer of vaporous refrigerant thereabove. With the stepped
insertion depth (x) of the tube end sections 11a, the tubes 11 are
supplied substantially uniformly with refrigerant, that is, with an
approximately equal refrigerant mass flow per tube.
[0015] The linearly decreasing function (f) shown is only one
embodiment of the invention. It does show, not to scale, a
schematic representation of the invention. It is likewise possible
to have a nonlinear decreasing function.
[0016] Furthermore, the tube insertion depth (x), which is to be
selected, is dependent upon the refrigerant throughput which is
applied for the design or configuration of the evaporator. For a
maximum refrigerant throughput, the turbulent refrigerant flow
extends relatively far (in direction (a)) into the inlet chamber,
that is, the transition to a layering of the flow occurs at a
greater distance (a) from the injection location. For a weaker
refrigerant mass flow, the layered flow adjusts closer to the
injection location. The pattern for the variable injection depths
of the tube end sections will orientate itself at a design point
between these two extremes.
[0017] Departing from the embodiment shown, the inlet chamber,
viewed geodetically, is mounted below so that the refrigerant,
which is supplied at the end of the inlet chamber, flows in the
refrigerant tubes from below to above, that is, opposite to the
direction of the force of gravity. In this case, the function for
the insertion depth is preferably an increasing function, that is,
the depth of insertion increases with increasing distance (a) from
the injection tube 6.
[0018] The evaporator 10 shown in FIG. 2 is preferably configured
as a two-row flat tube evaporator and has a multi-flow refrigerant
flow, that is, the refrigerant is redirected in the width (in
direction +a or -a) as well as in the depth (in airflow direction).
In the realization of the invention, it can be provided that the
variable insertion depth preferably applies for the first
passthrough. In the embodiment shown, these are the flat tubes 11
opening into the inlet chamber 7. After the first passthrough, it
can often be assumed that the refrigerant flow is uniform or
homogenized to the extent that a variable insertion depth is no
longer necessary or brings with it no significant advantages.
[0019] The evaporator of the invention is preferably used for
climate control systems in motor vehicles.
[0020] It is understood that the foregoing description is that of
the preferred embodiments of the invention and that various changes
and modifications may be made thereto without departing from the
spirit and scope of the invention as defined in the appended
claims.
* * * * *