U.S. patent application number 13/890885 was filed with the patent office on 2014-11-13 for heat exchanger.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is FORD GLOBAL TECHNOLOGY, LLC. Invention is credited to Syed K. Ali, Jun-Lon Chen, Jonathan Raver.
Application Number | 20140332188 13/890885 |
Document ID | / |
Family ID | 51787705 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140332188 |
Kind Code |
A1 |
Chen; Jun-Lon ; et
al. |
November 13, 2014 |
HEAT EXCHANGER
Abstract
A heat exchanger is provided having two headers with a plurality
of elongate tubes extending between the headers, where the tubes
cooperate with an array of fins. The tubes have a plurality of
dimpled sections having a non-uniform dimple density alternating
with a plurality of smooth sections. The alternating dimpled and
smooth sections allow heat to effectively transfer from a liquid
coolant flowing through the tubes into the tube walls and fins at
laminar, transitional, and turbulent flow conditions.
Inventors: |
Chen; Jun-Lon; (Ann Arbor,
MI) ; Raver; Jonathan; (Northville, MI) ; Ali;
Syed K.; (Dearborn, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FORD GLOBAL TECHNOLOGY, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
51787705 |
Appl. No.: |
13/890885 |
Filed: |
May 9, 2013 |
Current U.S.
Class: |
165/109.1 |
Current CPC
Class: |
F28F 1/42 20130101; F28F
13/12 20130101; F28F 1/126 20130101; F28D 1/05366 20130101; F28F
1/426 20130101 |
Class at
Publication: |
165/109.1 |
International
Class: |
F28F 1/42 20060101
F28F001/42; F28F 13/12 20060101 F28F013/12 |
Claims
1. A heat exchanger comprising: first and second headers having a
plurality of elongate tubes extending there between, the tubes
cooperating with an array of fins, wherein the tubes have a
plurality of dimpled sections having a non-uniform dimple density
followed by one of a plurality of alternating smooth sections, in
order to effectively transfer heat between a liquid flowing through
each tube and a tube wall at laminar, transitional, and turbulent
flow conditions.
2. The heat exchanger of claim 1, wherein the dimpled sections have
a first end and a second end, and the density of the dimples
gradually decreases along a longitudinal direction moving from the
first end to the second end in the direction of liquid flow.
3. The heat exchanging tube of claim 1, wherein each of the tubes
have at least three dimpled sections and at least three smooth
sections.
4. The heat exchanger of claim 1, wherein the dimples within the
dimpled sections are arranged in a plurality of clusters.
5. The heat exchanger of claim 1, wherein the plurality of elongate
tubes are made from aluminum.
6. The heat exchanger of claim 1, further comprising two header
tanks that are fixed to the first and second headers, wherein the
header tanks collect the liquid that flows through the plurality of
elongate tubes.
7. The heat exchanger of claim 6, wherein the header tanks are made
from plastic.
8. The heat exchanger of claim 6, wherein the header tanks are made
from aluminum.
9. The heat exchanger of claim 1, wherein the liquid flows into the
heat exchanger at the first header, through the plurality of tubes,
and out of the heat exchanger at the second header.
10. The heat exchanger of claim 1, wherein the dimpled sections
have a length L that ranges between 10 mm and 200 mm.
11. The heat exchanger of claim 1, wherein the smooth sections have
a length M that ranges between 10 mm and 200 mm.
12. A heat exchanger comprising: first and second headers having a
plurality of elongate tubes extending there between, the tubes
cooperating with an array of fins; and first and second header
tanks having ports, attached to the first and second headers for
collecting a liquid flowing into and out of the heat exchanger,
wherein the tubes have a plurality of dimpled sections having a
non-uniform dimple density followed by one of a plurality of
alternating smooth sections, in order to effectively transfer heat
between the liquid flowing through each tube and a tube wall at
laminar, transitional, and turbulent flow conditions.
13. The heat exchanger of claim 12, wherein the dimpled sections
have a first end and a second end, and the density of the dimples
gradually decreases along a longitudinal direction moving from the
first end to the second end in the direction of liquid flow.
14. The heat exchanger of claim 12, wherein each of the tubes have
at least three dimpled sections and at least three smooth
sections.
15. The heat exchanger of claim 12, wherein the dimples within the
dimpled sections are arranged in a plurality of clusters.
16. The heat exchanger of claim 12, wherein the plurality of
elongate tubes are made from aluminum.
17. The heat exchanger of claim 12, wherein the header tanks are
made from plastic.
18. The heat exchanger of claim 12, wherein the header tanks are
made from aluminum.
19. The heat exchanger of claim 12, wherein the dimpled sections
have a length L that ranges between 10 mm and 200 mm.
20. The heat exchanger of claim 12, wherein the smooth sections
have a length M that ranges between 10 mm and 200 mm.
Description
TECHNICAL FIELD
[0001] This invention relates to a heat exchanger of a tube and fin
design.
BACKGROUND
[0002] Tube and fin heat exchangers are used to transfer heat
between a liquid coolant flowing through the tubes and the
surrounding environment. The tube and fin design consists of
several tubes that extend between first and second headers with the
tubes cooperating with an array of fins providing a large surface
area. The liquid coolant flows across the tubes from one header to
the other while the fins are exposed to the air of the surrounding
environment. The fins and tubes are made from a material having a
high thermal conductivity allowing heat to effectively transfer
between the liquid coolant and the air of the surrounding
environment. The headers are typically attached to tanks that
collect the liquid flowing in and out of the heat exchanger.
[0003] In order to transfer heat from the tubes and fins to the
air, energy must first be transferred from the liquid coolant to
the tubes and fins. Various tube and fin designs have been proposed
to increase heat transfer from the liquid to the tubes and fins,
however, various designs function differently at different flow
rates. Both smooth tubes and tubes having dimples that protrude
into the interior of the tube have been used in tube and fin heat
exchangers. During times of low flow rates when the flow is
laminar, the difference in the amount of the heat transfer of a
tube and fin heat exchanger having either a smooth tube design or a
dimpled tube design is negligible. When the liquid coolant flow
rate increases, flow enters a transitional flow phase, between
laminar and turbulent flow, where the heat transfer from the liquid
coolant to the tube walls and fins is significantly greater with
dimpled tubes. Higher heat transfer is achieved with a heat
exchanger using dimpled tubes rather than smooth tubes during
transitional flow, because the dimples "stir up" the flows creating
disturbances, which increases the turbulence and heat transfer.
During turbulent flow, the heat transfer from the liquid coolant to
the tube walls and fins is significantly greater with smooth tubes
rather than dimpled tubes. Higher heat transfer is achieved with a
heat exchanger using smooth tubes rather than dimpled tubes during
turbulent flow, because the flows already have significant
disturbances, and the dimples on the walls of the dimpled tubes
reduce the contact area between the tubes and fins reducing the
heat that transfers between the tubes and fins. The reduction in
heat transfer from the tubes to the fins ultimately reduces the
overall heat transferred from the liquid coolant in the heat
exchanger to the surrounding external environment.
[0004] It would be desirable to provide a heat exchanger that
encompasses the properties of the dimpled tubes during transitional
flow and smooth tubes during turbulent flow, to allow for increased
heat transfer during both flow conditions of the liquid
coolant.
SUMMARY
[0005] A heat exchanger is disclosed for transferring heat between
a liquid coolant and the air of the surrounding environment. The
heat exchanger includes several elongate tubes that extend between
two headers and cooperate with an array of fins. The tubes consist
of alternating dimpled and smooth sections where the dimpled
sections have a non-uniform dimple density. Alternating the dimpled
and smooth sections on the tubes, allows for sufficient heat
transfer from the liquid flowing through the tube and into the tube
walls and fins at laminar, transitional, and turbulent flow
conditions. The liquid coolant flows across the tubes from one
header to the other while the fins are exposed to the air of the
surrounding environment. The tubes and fins are made from a
material having a high thermal conductivity allowing heat to
effectively transfer from the liquid coolant, into the tubes and
fins, and into the surrounding environment. Preferably, tanks are
attached to each header to collect the liquid coolant that flows in
and out of the tubes. The heat exchanger may also work in the
reverse direction, where the heat is flowing from the surrounding
environment, into the tubes and fins, and into the liquid coolant
that is flowing through the tubes, as in the case of an evaporator
in an air conditioning system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is an isometric view of the heat exchanger, the
number of tubes shown is reduced, and the spacing between sections
of each of the accordion style fins is increased for ease of
illustration;
[0007] FIG. 2 is a partial cross-sectional isometric view of the
header, tubes, and fins of the heat exchanger taken along the line
2-2 in FIG. 1;
[0008] FIG. 3 is a longitudinal cross-sectional view of the tube
taken along the line 3-3 of FIG. 2;
[0009] FIG. 4a is a plan view of a tube having zones of dimpled
sections with a gradually decreasing dimple density, and
alternating smooth zones;
[0010] FIG. 4b illustrates a graph having a plot of the dimpled
density of the tube in FIG. 4a versus the tube length in the
direction X;
[0011] FIG. 5a is a plan view of a tube having zones of clustered
dimpled sections, and alternating smooth sections;
[0012] FIG. 5b illustrates a graph having a plot of the dimpled
density of the tube in FIG. 5a versus the tube length in the
direction X; and
[0013] FIG. 6 illustrates a graph comparing the relative heat
transfer capabilities of dimpled tubes, smooth tubes, and tubes
with alternating dimpled and smooth sections during laminar,
transitional, and turbulent flow conditions.
DETAILED DESCRIPTION
[0014] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention.
[0015] FIG. 1 illustrates a heat exchanger 10 according to the
present disclosure. The heat exchanger 10 consists of several
elongate tubes 12 that extend between two headers 14, with the
tubes 12 attached to an array of fins 16. In the preferred
embodiment, a liquid coolant flows across the tubes 12 from one
header 14 to the other in a single pass. The invention however, is
not limited to a single pass flow and the disclosure should be
construed to include other embodiments having multiple passes.
Also, in the preferred embodiment, the fins 16 are disposed between
adjacent tubes, arranged in an accordion type configuration, and
exposed to the air of the surrounding environment. The invention
however, is not limited to the according type fin configuration,
and should be construed to include other fin configurations, such
as an intersecting tube and fin configuration. The tubes 12,
headers 14, and fins 16 are preferably made from a material having
a high thermal conductivity, such as aluminum, copper, brass, or
steel, but should not be limited to these materials. Brazing is
typically the process used to fix the tubes 12 to the headers 14.
Two header tanks 18 are provided that are fixed to the headers 14
and collect the liquid coolant flowing in and out of the heat
exchanger 10 at ports 20. Preferably, the header tanks 18 are made
from a lightweight corrosion resistant material such as plastic.
However, the header tanks 18 should not be limited to lightweight
plastic only, and could be made from other materials such as
aluminum, steel, or copper alloys such as brass.
[0016] As illustrated in FIG. 2, the elongate tubes 12 have an
outside width W and an outside height H. Preferably, the width W of
the elongate tubes 12 ranges from 10 mm to 40 mm and the height H
ranges from 1 mm to 2.5 mm. Preferably the material thickness of
the elongate tubes 12 will range between 0.15 mm and 0.35 mm. The
headers will have a preferred material thickness of about 1.5 mm,
while the fins 16 will have a preferred material thickness that
ranges from 0.05 mm to 0.10 mm. The fin height will preferably
range from 4 mm and 9 mm. The fin height being approximately equal
to the distance between two adjacent elongate tubes 12 in the
accordion fin design illustrated.
[0017] Referring to FIGS. 2 and 3, dimples 22 are provided that
protrude into the interior of the elongated tubes 12. The dimples
22 increase heat transfer during transitional flow conditions by
agitating the liquid coolant. The agitation is represented by the
circular shaped flow arrows in FIG. 3.
[0018] Referring to FIGS. 4a and 5a, an elongate tube 12 is divided
into alternating dimpled sections 24 and smooth sections 26. The
smooth tubes 26 have higher heat transfer than the dimpled sections
24 during turbulent flow conditions.
[0019] Still referring to FIGS. 4a and 5a, the preferred embodiment
alternates dimpled sections 24 with smooth sections 26 in order to
take advantage of the increased heat transfer properties of both
dimpled and smooth tubes whether in transitional or turbulent flow
conditions. The dimpled sections have a length L and the smooth
sections have a length M. Preferably, the lengths L and M will both
range between 10 mm and 200 mm, and more preferably from 35 mm to
75 mm.
[0020] FIGS. 4a and 4b illustrate an embodiment according to the
present disclosure having alternating dimpled sections 24 and
smooth sections 26 of an elongate tube 12, where the density of
dimples 22 in the dimpled sections 24 gradually decreases as you
move in a direction X. FIG. 4b is a graphical representation of a
portion of the elongate tube 12, showing the dimple density
decreasing in a linear fashion over each dimpled section 24 and a
dimple density of zero in each smooth section as you move in a
direction X.
[0021] FIGS. 5a and 5b illustrate an alternative embodiment
according to the present disclosure having alternating dimpled
sections 24 and smooth sections 26 of an elongate tube 12. The
dimples 22 are arranged in several clusters, where the number of
dimples in each cluster decreases as you move in a direction X
across each dimpled section 24. FIG. 5b is a graphical
representation of a portion of the elongate tube 12, showing
clusters of decreasing size over each dimpled section 24, where the
dimple density is zero between each cluster and in each smooth
section as you move in a direction X.
[0022] The present disclosure should not be limited to the
embodiments described herein, and should be construed to include
all elongate tubes 12 having alternating dimpled sections 24 and
smooth sections 26, where the dimple density in the dimpled
sections 24 is non-uniform.
[0023] The graph in FIG. 6 illustrates the relative heat transfer
capabilities of dimpled, smooth, and tubes having alternating
dimpled and smooth sections during laminar, transitional, and
turbulent flow conditions.
[0024] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms of the
invention. As previously noted, the invention is not limited to
radiators, but can be a heat exchanger used as a condenser or
evaporator in an air conditioning system or the like. The words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
Additionally, the features of various implementing embodiments may
be combined to form further embodiments of the invention.
* * * * *