U.S. patent application number 12/697586 was filed with the patent office on 2010-08-05 for fin for a heat exchanger.
Invention is credited to Hermann KNAUS, Stefan ROESLER, Florian SCHMIDT.
Application Number | 20100193172 12/697586 |
Document ID | / |
Family ID | 39968008 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100193172 |
Kind Code |
A1 |
KNAUS; Hermann ; et
al. |
August 5, 2010 |
FIN FOR A HEAT EXCHANGER
Abstract
A fin for a heat exchanger is provided that includes a fin
element which extends in a flow direction of a first fluid and has
a wall face around which the first fluid flows on both sides,
wherein at least one flap is provided in the wall face, which flap
forms a cutout, through which the first fluid can flow, in the wall
face, wherein a first straight edge of the flap extends
substantially perpendicularly to the flow direction and is arranged
at a distance from the wall face in order to form the cutout,
wherein the flap has an inclined, smooth tab face which terminates
at the first straight edge, and wherein the tab face is connected
to the wall face via two side walls of the tab, which side walls
have a curved profile mirror-symmetrically with respect to each
other and, starting from the first edge, have a height which
decreases in a manner corresponding to the inclination of the tab
face.
Inventors: |
KNAUS; Hermann; (Stuttgart,
DE) ; SCHMIDT; Florian; (Remseck, DE) ;
ROESLER; Stefan; (Esslingen, DE) |
Correspondence
Address: |
Muncy, Geissler, Olds & Lowe, PLLC
4000 Legato Road, Suite 310
FAIRFAX
VA
22033
US
|
Family ID: |
39968008 |
Appl. No.: |
12/697586 |
Filed: |
February 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2008/005983 |
Jul 22, 2008 |
|
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|
12697586 |
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Current U.S.
Class: |
165/185 |
Current CPC
Class: |
F28F 1/325 20130101;
F28F 3/027 20130101; F28F 1/128 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2007 |
DE |
DE 102007036308.9 |
Claims
1. A fin for a heat exchanger comprising: a fin element configured
to extend in a flow direction of a first fluid and has a wall face
around which the first fluid flows on both sides; and at least one
flap provided in the wall face, the flap forming an aperture
through which the first fluid can flow into the wall face, a first
straight edge of the flap being configured to extend substantially
perpendicular to the flow direction and being arranged at a
distance from the wall face to form the aperture, wherein the flap
has an inclined, smooth tab face that terminates at the first
straight edge, and wherein the tab face is connected to the wall
face via two side walls of the tab, which side walls have a curved
profile mirror-symmetrically with respect to one another and,
starting from the first edge, have a height which decreases in a
manner corresponding to the inclination of the tab face.
2. The fin according to claim 1, wherein the first edge, end-side
edges of the side walls, and a second straight edge of the wall
face form a rectangle that is oriented substantially
perpendicularly to the flow direction and through which the first
fluid is flowable.
3. The fin according to claim 2, wherein a long side of the
rectangle corresponds to the first edge and has a length that is
approximately five times the length of a short side of the
rectangle.
4. The fin according to claim 2, wherein the length of the tab face
in the flow direction is approximately eight times the length of
short sides of the rectangle.
5. The fin according to claim 1, wherein flap is mirror-symmetrical
with respect to a central axis of symmetry.
6. The fin according to claim 1, wherein a width of the tab face
reduces with increasing distance from the first edge.
7. The fin according to claim 6, wherein an end of the tab face
opposite the first edge has a smallest width, and wherein the
smallest width is no more than one tenth, in particular about one
twelfth of the length of the first edge.
8. The fin according to claim 1, wherein a curve of one of the side
walls has at least one point of inflection in its course with
regard to a direction of curvature.
9. The fin according to claim 1, wherein an inclination of the tab
face with respect to the wall face is approximately seven
degrees.
10. The fin according to claim 1, wherein a shape of the tab face
starting from the first edge has approximately the parameterisation
[0; 2.500], [0.805; 2.470], [1.610; 2.290], [2.420; 1. 910],
[3.220; 1.540], [4.030; 1.210], [4.840; 0.980], [5.640; 0.780],
[6.440; 0.590], [7.240; 0. 400], [8.050; 0.210], wherein the first
value in each case specifies the distance from the first edge and
the second value in each case specifies the distance from a central
axis of symmetry to a side wall.
11. The fin according to claim 1, wherein the fin has a plurality
of flaps arranged one after the other in the direction of flow.
12. The fin according to claim 1, wherein at least two flaps with
different opening directions are provided in the wall face.
Description
[0001] This nonprovisional application is a continuation of
International Application No. PCT/EP2008/005983, which was filed on
Jul. 22, 2008, and which claims priority to German Patent
Application No. DE 10 2007 036 308.9, which was filed in Germany on
Jul. 31, 2007, and which are both herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a fin for a heat exchanger.
[0004] 2. Description of the Background Art
[0005] Heat exchangers are known in which fins are provided in
channels through which fluid flows in order to improve the capacity
of the exchanger. Such fins can be designed, for example, in the
form of smooth fins, gill-shaped fins or also in the form of web
fins. In the first case, as a result of the extensively laminar
flow, only a relatively small improvement in the performance of the
exchanger is achieved, although the drop in pressure of the fluid
caused by the fins is also relatively small. Web fins show a
particularly clear improvement in the performance of the exchanger
for a given size, but also often mean an undesirably large drop in
pressure across the flow channel. Amongst other applications, web
fins are used in charge air coolers of motor vehicles,
predominantly on the charge air side.
[0006] DD 0 152 187 describes a strip-shaped tubular installation
element for tube bundle heat exchangers in the petrochemical
industry field with which trapezoidal flaps are provided for
producing turbulence. The flaps have a variable width in the flow
direction, wherein the flaps are bent out from the strip by an
angle of more than 30.degree. about a longer of two parallel edges
of the trapezium.
[0007] Research Memorandum Number RM A9L29 of the National Advisory
Committee for Aeronautics (NACA), Washington, USA, of 23 Feb. 1950
describes a submerged air inlet for aircraft wings which were being
investigated with regard to their flow behaviour in a speed range
from Mach 0.6 to Mach 1.08.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention to
provide a fin for a heat exchanger whose heat transmission is
improved for a given drop in pressure.
[0009] According to an embodiment, as a result of two
mirror-symmetrical side walls of the flaps which have a curved
profile with respect to one another and which are oriented
perpendicular to the wall face and which, starting from the first
edge, have a height which decreases in a manner corresponding to
the inclination of the tab face, an improved air flow is achieved
in the area of the flaps, as a result of which a greater quantity
of heat is transmitted between air and fin for a given drop in
pressure.
[0010] In an embodiment, the first edge, end-side edges of the side
walls, and a second straight edge of the wall can form a rectangle
which is oriented perpendicularly to the flow direction and through
which the first fluid can flow. A long side of the rectangle can
correspond to the first edge and can have a length which is
approximately five times the length of short side of the rectangle.
The length of the tab face in the flow direction is approximately
eight times the length of the short sides of the rectangle. At the
same time, the flap can be designed mirror-symmetrically with
respect to a central plane of symmetry, and furthermore a width of
the tab face preferably reduces with increasing distance from the
first edge. In doing so, an end of the tab face opposite the first
edge has a smallest width, wherein the smallest width
advantageously is no more than one tenth, in particular about one
twelfth of the length of the first edge. The curve of one of the
side walls also has at least one point of inflection in its course
with regard to the direction of curvature. In a preferred
embodiment, the inclination of the tab face with respect to the
wall face is approximately seven degrees. Overall, this provides a
hood-like tab with a particularly low drop in pressure with good
heat transfer of the air flowing through it, as has been shown by
trials.
[0011] In an embodiment, the shape of the tab face starting from
the first edge can have approximately the parameterisation [0;
2.500], [0.805; 2.470], [1.610; 2.290], [2.420; 1.910], [3.220;
1.540], [4.030; 1.210], [4.840; 0.980], [5.640; 0.780], [6.440;
0.590], [7.240; 0.400], [8.050; 0.210]. This parameterisation is
understood to mean that the first value in each case specifies the
distance from the first edge and the second value in each case
specifies the distance from a central axis of symmetry to one of
the two mirror-symmetrical side walls. Apart from a considerable
scaling factor, this parameterisation corresponds to the shape of
the air inlet described in the NACA report RM A9L29.
[0012] In a further embodiment, the fin can have a plurality of
flaps arranged one after the other in the direction of flow, which,
particularly in the case of long fins, results in an expedient
arrangement for the purpose of deflecting the air several times
over the length of the fin. Otherwise, the air flow would only be
advantageously affected by the flap over part of the fin.
[0013] Furthermore, at least two flaps with different opening
directions can be provided in the wall face. As a result of such an
alternating arrangement of the flap opening directions, heat can be
exchanged with the flowing air particularly uniformly on both sides
of the fin.
[0014] The invention also relates to a heat exchanger having at
least one fin.
[0015] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limitive of the present invention, and wherein:
[0017] FIG. 1 shows a spatial representation of a first exemplary
embodiment of a fin according to the invention;
[0018] FIG. 2 shows a scale plan view on a flap of a fin according
to the invention from above; and
[0019] FIG. 3 shows a spatial representation of a second exemplary
embodiment of a fin according to the invention.
DETAILED DESCRIPTION
[0020] The exemplary embodiment of the invention shown in FIG. 1
comprises a fin 1 made from an aluminium sheet which has been
folded several times. A flow channel 2, through which a first fluid
of the heat exchanger, in this case air, flows in the direction of
the arrow A or also in the opposite direction as shown by the arrow
A', is formed between two parallel wall faces 1a. The heat
exchanger is designed so that a plurality of the fins 1 are
arranged adjacent to one another to form parallel adjacent flow
channels 2. Exchanger tubes or separating walls (not shown), which
form the boundary of a second fluid, are connected to the surface
of the fins 1 above and below the fins 1.
[0021] A flap 3 which has a smooth tab face 4 and is inclined with
respect to the sidewall 1a is arranged in at least one of the side
walls 1a of the fin 1. The angle of inclination is approximately
7.degree..
[0022] The tab face 4 has a first straight edge 5 which extends
perpendicular to the flow direction A, A' and parallel to the wall
face 1a.
[0023] A cutout which is coincident with the tab face and which has
a second straight edge 6 is provided in the wall face 1a. At the
same time, the tab face 4 is connected to the wall face 1a of the
fin by means of two side walls 7, 8 which have a curved profile and
are arranged mirror-symmetrically with respect to an axis of
symmetry S of the flap and to each other. The side walls 7, 8 of
the flap are perpendicular to the wall face 1a of the fin 1.
Corresponding to the inclination of the tab face 4, the height of
the side walls 7, 8 increases in the flow direction A and decreases
in the opposite, likewise possible, flow direction A'. At the same
time, edges 7a, 8a with the maximum height of the side walls 7, 8
are formed at the end and lie in one plane with the first straight
edge 5 of the tab face and the second straight edge 6 of the wall
face 1a, wherein the four edges 5, 6, 7a, 8a form a rectangular
aperture or opening 9 perpendicular to the wall face 1a. The
rectangle 9 has a side ratio of 1:5, the long sides of the
rectangle being formed by the first and second straight edge 5,
6.
[0024] In the flow direction A, the curved, mirror-symmetrical side
walls 7, 8 are initially at a smallest distance from one another at
their beginning, the distance growing steadily over the length L of
the tab face. At both the beginning of their path and at the end,
the side walls run approximately parallel to the axis of symmetry S
so that at the end of their path they meet the first and second
straight edge 5, 6 approximately at right angles (see FIG. 2).
[0025] Corresponding to the inclination of about 7.degree., the
length L of the tab face 4 is approximately eight times the maximum
height of the side walls 7, 8.
[0026] The side walls 7, 8 change their direction of curvature
approximately halfway through their path so that the curve has
exactly one point of inflection. A parameterisation of the path of
the side walls of the preferred exemplary embodiment is:
[0027] [0; 2.500], [0.805; 2.470], [1.610; 2.290], [2.420; 1.910],
[3.220; 1.540], [4.030; 1.210], [4.840; 0.980], [5.640; 0.780],
[6.440; 0.590], [7.240; 0.400], [8.050; 0.210].
[0028] Here, the first number of a coordinate pair [x; y] in each
case means the distance starting from the first edge 6 in the
direction of the axis of symmetry S, that is to say in the opposite
direction to the flow direction A. The second number y describes
the perpendicular distance of a side wall from the axis of symmetry
S at this point. In these non-dimensional relative units, the side
walls 7, 8 have a maximum height of approximately 1.0 and the
maximum width B of the tab face 4 which runs along the first
straight edge is correspondingly 5.0.
[0029] As a result of the hood-like form of the flap described
above with an inclined tab face and ascending side walls in the
flow direction, the air flowing through the flow channel 2 along
the wall face 1a can pass through the opening 9, wherein it both
swirls and is exchanged with an adjacent flow channel. The
ascending path of the tab face and the curved diverging side walls
result in a form which is particularly favourable for dynamic flow
and which achieves a good exchange of heat with a low drop in
pressure.
[0030] An improvement of the fin according to the invention is
shown in FIG. 3 in which a plurality of flaps 3 are arranged one
behind the other in the direction of flow. Here, two consecutive
flaps are shown reversed with regard to their opening direction in
the wall face 1a, that is to say alternating. This achieves a
uniform and optimum swirling of the air particularly with long flow
channels 2.
[0031] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are to be included within the scope of the following
claims.
* * * * *