U.S. patent application number 13/981364 was filed with the patent office on 2013-11-21 for tube structures for heat exchanger.
This patent application is currently assigned to Carrier Corporation. The applicant listed for this patent is Sunil S. Mehendale, Michael F. Taras, Mel Woldesemayat. Invention is credited to Sunil S. Mehendale, Michael F. Taras, Mel Woldesemayat.
Application Number | 20130306288 13/981364 |
Document ID | / |
Family ID | 45562485 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130306288 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
November 21, 2013 |
TUBE STRUCTURES FOR HEAT EXCHANGER
Abstract
A fluid-carrying tube for a heat exchanger includes an outer
perimeter, an inner perimeter, and a plurality of ridges extending
from the inner perimeter inwardly into an interior of the tube.
Each ridge includes a ridge height, a base width and a tip width. A
ratio of the ridge height to the base width is between about 0.2
and about 4.0, and a ratio of the tip width to the base width is
between about 0.015 and about 0.965.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Mehendale; Sunil S.;
(Manlius, NY) ; Woldesemayat; Mel; (Liverpool,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taras; Michael F.
Mehendale; Sunil S.
Woldesemayat; Mel |
Fayetteville
Manlius
Liverpool |
NY
NY
NY |
US
US
US |
|
|
Assignee: |
Carrier Corporation
Farmington
CT
|
Family ID: |
45562485 |
Appl. No.: |
13/981364 |
Filed: |
January 26, 2012 |
PCT Filed: |
January 26, 2012 |
PCT NO: |
PCT/US12/22641 |
371 Date: |
July 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61437427 |
Jan 28, 2011 |
|
|
|
Current U.S.
Class: |
165/181 |
Current CPC
Class: |
F28F 1/12 20130101; F28F
21/08 20130101; F28F 1/40 20130101; F28F 1/32 20130101 |
Class at
Publication: |
165/181 |
International
Class: |
F28F 1/12 20060101
F28F001/12 |
Claims
1. A fluid-carrying tube for a heat exchanger comprising: an outer
perimeter; an inner perimeter; and a plurality of ridges extending
from the inner perimeter inwardly into an interior of the tube,
each ridge having; a ridge height; a base width; and a tip width;
wherein a ratio of the ridge height to the base width is between
about 0.2 and about 4.0; and wherein a ratio of the tip width to
the base width is between about 0.015 and about 0.965.
2. The tube of claim 1, wherein the plurality of ridges extend
substantially axially along a length of the tube.
3. The tube of claim 1, wherein the plurality of ridges extend
helically along a length of the tube.
4. The tube of claim 3, wherein a helix angle of the plurality of
ridges is between about 18 degrees and 35 degrees.
5. The tube of claim 1, wherein a ratio of a number of ridges in
the plurality of ridges to a maximum internal diameter of the tube
expressed in millimeters is between about 5.4 and 10.1.
6. The tube of claim 5, wherein the ratio of a number of ridges in
the plurality of ridges to a maximum internal diameter of the tube
expressed in millimeters is between about 5.5 and 9.25.
7. The tube of claim 1, wherein a ratio of the ridge height to a
ridge pitch between adjacent ridges of the plurality of ridges is
between about 0.17 and about 1.36.
8. The tube of claim 7, wherein the ratio of the ridge height to
the ridge pitch is between about 0.19 and about 1.22.
9. The tube of claim 1, wherein a ratio of the ridge height to a
maximum internal diameter of the tube is between about 0.0008 and
about 0.0870.
10. The tube of claim 9, wherein the ratio of the ridge height to
the maximum internal diameter of the tube is between about 0.021
and about 0.035.
11. The tube of claim 1, wherein the tube is formed from an
aluminum or aluminum alloy.
12. The tube of claim 1, wherein the tube is of a substantially
non-circular cross-section, including but not limited to oval,
elliptical and race-track cross-sections.
13. The tube of claim 1, wherein the tube has an effective diameter
of between about 5 millimeters and about 13 millimeters.
14. A heat exchanger comprising: a plurality of fins; a plurality
of tubes passing a fluid therethrough and extending through the
plurality of fins, a least one tube of the plurality of tubes
including: an outer perimeter; an inner perimeter; and a plurality
of ridges extending from the inner perimeter inwardly into an
interior of the tube, each ridge having: a ridge height; a base
width; and a tip width; wherein a ratio of the ridge height to the
base width is between about 0.2 and about 4.0; and wherein a ratio
of the tip width to the base width is between about 0.015 and about
0.965.
15. The heat exchanger of claim 13, wherein the plurality of ridges
extend substantially axially along a length of the at least one
tube.
16. The heat exchanger of claim 13, wherein the plurality of ridges
extend helically along a length of the at least one tube.
17. The heat exchanger of claim 15, wherein a helix angle of the
plurality of ridges is between about 18 degrees and 35 degrees.
18. The heat exchanger of claim 13, wherein a ratio of a number of
ridges in the plurality of ridges to a maximum internal diameter
expressed in millimeters of the at least one tube is between about
5.4 and 10.1.
19. The heat exchanger of claim 17, wherein the ratio of a number
of ridges in the plurality of ridges to a maximum internal diameter
expressed in millimeters of the at least one tube is between about
5.5 and 9.25.
20. The heat exchanger of claim 13, wherein a ratio of the ridge
height to a ridge pitch between adjacent ridges of the plurality of
ridges is between about 0.17 and about 1.36.
21. The heat exchanger of claim 19, wherein the ratio of the ridge
height to the ridge pitch is between about 0.19 and about 1.22.
22. The heat exchanger of claim 13, wherein a ratio of the ridge
height to a maximum internal diameter of at least one tube of the
plurality of tubes is between about 0.0008 and about 0.0870.
23. The heat exchanger of claim 13, wherein at least one tube of
the plurality of tubes is formed from an aluminum or aluminum
alloy.
24. The heat exchanger of claim 13, wherein at least one tube of
the plurality of tubes is of a substantially non-circular
cross-section, including but not limited to oval, elliptical and
race-track cross-sections.
25. The heat exchanger of claim 13, wherein at least one tube of
the plurality of tubes has an effective diameter of between about 5
millimeters and about 13 millimeters.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to heat
exchangers. More specifically, the subject disclosure relates to
improved tube structures for a heat exchanger.
[0002] A simplified typical vapor compression refrigeration cycle
includes an evaporator, a compressor, a condenser and an expansion
device. Refrigerant flow is such that low pressure refrigerant
vapor passes through a suction line to the compressor. The
compressed refrigerant vapor is pumped to a discharge line that
connects to the condenser. A liquid line receives liquid
refrigerant exiting the condenser and directs it to the expansion
device. A two-phase refrigerant is returned to the evaporator,
thereby completing the cycle.
[0003] Two of the main components in a vapor compression cycle are
the evaporator and condenser heat exchangers. The most common type
of heat exchanger in use is of the round tube plate fin (RTPF)
construction type. Historically, the tubes were made of copper
while the fins were typically made of aluminum in such heat
exchangers. The thermal performance of a heat exchanger, the
ability to transfer heat from one medium to another, is inversely
proportional to the sum of its thermal resistances. For a typical
heating, ventilation, air conditioning and refrigeration
(HVAC&R) application using refrigerant inside the tubes and air
on the external fin side, the airside thermal resistance
contributes 50-70% while refrigerant side thermal resistance is
20-40% and the metal resistance is relatively small and represents
only 6-10%. Due to the continuous market pressure and regulatory
requirements to make HVAC&R units more compact and cost
effective, a lot of effort has been devoted to improving the heat
exchanger performance on the refrigerant side as well as the
airside.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention, a fluid-carrying
tube for a heat exchanger includes an outer perimeter, an inner
perimeter, and a plurality of ridges extending from the inner
perimeter inwardly into an interior of the tube. Each ridge
includes a ridge height, a base width and a tip width. A ratio of
the ridge height to the base width is between about 0.2 and about
4.0, and a ratio of the tip width to the base width is between
about 0.015 and about 0.965.
[0005] According to another aspect of the invention, a heat
exchanger includes a plurality of fins and a plurality of tubes
passing a fluid therethrough and extending through the plurality of
fins. At least one tube of the plurality of tubes includes an outer
perimeter, an inner perimeter, and a plurality of ridges extending
from the inner perimeter inwardly into an interior of the at least
one tube. Each ridge has a ridge height, a base width, and a tip
width. A ratio of the ridge height to the base width is between
about 0.2 and about 4.0, and a ratio of the tip width to the base
width is between about 0.015 and about 0.965.
[0006] These and other advantages and features will become more
apparent from the following description taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The subject matter, which is regarded as the invention, is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0008] FIG. 1 is a schematic view of an embodiment of a heat
exchanger;
[0009] FIG. 2 is a partial cross-sectional view of an embodiment of
a heat exchanger tube; and
[0010] FIG. 3 is a cross-sectional view of an embodiment of a heat
exchanger tube.
[0011] The detailed description explains embodiments of the
invention, together with advantages and features, by way of example
with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Shown in FIG. 1 is an embodiment of a round tube plate fin
(RTPF) heat exchanger 10, such as one utilized as an evaporator or
condenser. The RTPF heat exchanger 10 includes a plurality of tubes
12 and a plurality of fins 14. The plurality of tubes 12 carry a
fluid, for example, a refrigerant. Thermal energy is exchanged
between the fluid and air flowing past the plurality of fins 14. In
some embodiments, the tubes 12 may be formed of an aluminum or
aluminum alloy by, for example, an extrusion process, while in
other embodiments, the tubes 12 maybe formed of other materials,
for example, copper, Cu--Ni, steel or plastic.
[0013] FIG. 2 illustrates a partial cross-sectional view of a tube
12 of a heat exchanger 10. The tube 12 includes a plurality of
enhancements, or ridges 16 extending into an interior 18 of the
tube 12. As shown in FIG. 3, the tube 12 has an outer perimeter 32
and an inner perimeter 34, with the ridges 16 extending inwardly
from the inner perimeter 34 into the interior 18 of the tube 12.
The ridges 16 extend along a length 20 of the tube 12. In some
embodiments, the ridges 16 extend substantially axially, while in
other embodiments, the ridges 16 extend helically along the tube 12
at a helix angle .alpha. with respect to a tube axis 24. Ridges 16,
such as those described herein, improve the heat transfer
characteristics of the tubes 12 while maintaining a balance with
pressure drop requirements to achieve a desired refrigerant flow
through the tubes 12. Specific geometric configurations of the
ridges 16, enhancing both the pre-expansion and post-expansion tube
12 surface geometry, are described below by way of example.
[0014] Referring again to FIG. 2, the ridges 16 have a number of
characteristics to define their shape and arrangement in the
interior 18 of the tube 12. Each ridge 16 has a ridge 16 height h,
a base 26 width w, and a tip 28 width b. Sides 30 of the ridge 16
extend from the base 26 to the tip 28 at an apex angle Y. Adjacent
ridges 16 are spaced by a ridge 16 pitch P.sub.r. Each tube 12 has
a tube diameter D, and a baseline tube 12 wall thickness t.sub.b
between adjacent ridges 16.
[0015] Shape of the ridges 16, as well as ridge 16 pitch P.sub.r
and a number of ridges 16 in the tube 12, N.sub.r, are all taken
into account when comparing an internal surface area of a tube 12
including the ridges 16 to a typical tube having a smooth wall, and
thus an internal diameter as shown in equation (1) of:
D-2*t.sub.b (1)
[0016] The increased internal surface area of the tube 12 including
ridges 16 compared to the smooth-walled tube increases the
effectiveness of thermal energy transfer between fluid in the tube
12 and an external environment. The effect of the increased surface
area can be expressed as an enhancement ratio R.sub.x as in
equation (2) below:
R.sub.x=(2*h*N.sub.r*((1-sin(Y/2)/(.pi.*(D-2*(t.sub.b+h))*cos(Y/2)))+1)/-
cos .alpha. (2)
[0017] As can be seen from a review of equation (2), the
enhancement ratio Rx is a strong linear function of
h/(.pi.*(D-2*(t.sub.b+h))/N.sub.r), which is a ratio of the ridge
height h, to the ridge pitch P.sub.r.
[0018] In some embodiments, the ridges 16 may extend substantially
axially along the length 20, or may extend at helix angle a of
between about 18 degrees and about 35 degrees. Further, a ratio of
the number of ridges Nr to a maximum internal diameter of the tube
12, or N.sub.r/D.sub.imax may be between about 5.4 and about 10.1,
where D.sub.imax is specified in millimeters. In some embodiments,
a ratio of the ridge height, h, to the ridge pitch, P.sub.r, is
between about 0.17 and about 1.36. R.sub.x, as shown in equation 1,
is between about 1.28 and about 3.49 in some embodiments, for
example, those where the ridges 16 extend substantially axially
along the tube 12. In other embodiments, for example where the
helix angle .alpha. is not zero, R.sub.x is between about 1.34 and
about 4.26. In some embodiments, a ratio ridge height h to maximum
internal diameter of the tube 12, or MD. , is between about 0.0008
and about 0.0870. For some ridges 16, the apex angle Y is between
about 10 degrees and 25 degrees. Further, in some embodiments, the
ridge height h and base width w are related such that a ratio of
the ridge height to the base width, or h/w is between about 0.2 and
about 4.0. Similarly, in other embodiments, the tip width b and the
base width w, or b/w, is between about 0.015 and about 0.965.
[0019] Such ratios and ranges described above may vary for specific
tube 12 outer diameters. For example, for tubes 12 with outer
diameters of about 0.5 inches, N.sub.r/D.sub.imax may be between
about 5.4 and about 9.25. Further, h/P.sub.r is between about 0.17
and about 1.22. R.sub.x is between about 1.28 and about 3.23 in
embodiments where the ridges 16 extend substantially axially along
the tube 12 and where the helix angle .alpha. is not zero, R.sub.x
is between about 1.34 and about 3.94. In embodiments of 0.5 inch
diameter tube, h/D.sub.imax, is between about 0.0008 and about
0.035.
[0020] In other embodiments where the tubes 12 have outer diameters
of about 0.375 inches, N.sub.r/D.sub.imax , where D.sub.imax is
expressed in millimeters, may be between about 5.8 and about 10.1.
Further, h/P.sub.r is between about 0.19 and about 1.36. R.sub.x is
between about 1.30 and about 3.49 in embodiments where the ridges
16 extend substantially axially along the tube 12 and where the
helix angle .alpha. is not zero, R.sub.x is between about 1.37 and
about 4.26. In embodiments of 0.375 inch diameter tube,
h/D.sub.imax, is between about 0.0117 and about 0.0488.
[0021] In other embodiments where the tubes 12 have outer diameters
of about 7 millimeters, N.sub.r/D.sub.imax may be between about 5.4
and about 9.5, where D.sub.imax is specified in millimeters.
Further, h/P.sub.r is between about 0.18 and about 1.30. R.sub.x is
between about 1.28 and about 3.37 in embodiments where the ridges
16 extend substantially axially along the tube 12 and where the
helix angle .alpha. is not zero, R.sub.x is between about 1.35 and
about 4.12. In embodiments of 7 millimeter diameter tube,
h/D.sub.imax, is between about 0.021 and about 0.087.
[0022] In still other embodiments where the tubes 12 have outer
diameters of about 5 millimeters, N.sub.r/D.sub.imax may be between
about 5.5 and about 9.4, where D.sub.imax is specified in
millimeters. Further, h/P.sub.r is between about 0.18 and about
1.30. R.sub.x is between about 1.29 and about 3.39 in embodiments
where the ridges 16 extend substantially axially along the tube 12
and where the helix angle a is not zero, R.sub.x is between about
1.36 and about 4.14. In embodiments of 5 millimeter diameter tube,
h/D.sub.imax, is between about 0.021 and about 0.087.
[0023] While the tubes 12 illustrated herein are substantially
circular, it is to be appreciated that, in other embodiments, the
tubes 12 may be noncircular in cross-section having, for example,
an oval, an elliptical, or a race-track cross-section. In such
tubes, an equivalent to tube 12 diameter D would be a circular
cross-section tube diameter that would have identical mass or
material content in the cross-section as the particular
non-circular cross-section. All geometrical ratios described
hereabove are equally applicable to such non-circular tube
configurations allowing achieving substantially improved in-tube
thermal and hydraulic performance.
[0024] Referring to the geometric ratios described herein, tubes 12
including such ridges 16 that conform to the exemplary ranges of
these ratios exhibit substantially improved thermo-hydraulic
performance over prior art tubes. The ratios, and described ranges
for the ratios, are not obvious and have been developed via
extensive simulation and experimentation on the component and
sub-component level, while specifically focusing on the two-phase
refrigerant flows.
[0025] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *