U.S. patent application number 14/674699 was filed with the patent office on 2015-10-22 for counterflow helical heat exchanger.
The applicant listed for this patent is Enterex America LLC. Invention is credited to James Kolb.
Application Number | 20150300745 14/674699 |
Document ID | / |
Family ID | 54321744 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150300745 |
Kind Code |
A1 |
Kolb; James |
October 22, 2015 |
COUNTERFLOW HELICAL HEAT EXCHANGER
Abstract
A heat exchanger assembly comprising a tube with a thermally
conductive tube insert sealed therein, the tube insert having a
substantially similar cross-section to the cross-section of the
tube, and a plurality of fluid ports for passage of fluid into and
out of the tube, the fluid ports arranged for counterflow
operation. The tube insert includes a pair of helices extending
along the length of the tube insert, the helices having first and
second sides offset from each other by a predetermined distance
along the length of the tube insert and first and second ends, each
of the first ends offset from the other by a predetermined angle
and each of the second ends offset from the other by a
predetermined angle. The tube insert is sealed within the tube to
form a first fluid flow path and a second fluid flow path, the
first fluid flow path defined between the first sides of the
helices and the second fluid path defined between the second sides
of the helices.
Inventors: |
Kolb; James; (Westbrook,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Enterex America LLC |
Westbrook |
CT |
US |
|
|
Family ID: |
54321744 |
Appl. No.: |
14/674699 |
Filed: |
March 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61980274 |
Apr 16, 2014 |
|
|
|
Current U.S.
Class: |
165/156 ;
165/184; 29/890.036; 29/890.048; 29/890.054 |
Current CPC
Class: |
F28F 13/12 20130101;
F28D 7/0066 20130101; F28F 2275/122 20130101; F28F 2230/00
20130101; F28D 7/022 20130101; F28F 2009/0287 20130101; F28F 1/022
20130101; F28F 2275/04 20130101; F28D 7/026 20130101; F28F 9/0202
20130101; B23P 15/26 20130101; F28F 1/36 20130101 |
International
Class: |
F28D 7/10 20060101
F28D007/10; B23P 15/26 20060101 B23P015/26; F28F 1/36 20060101
F28F001/36 |
Claims
1. A helical heat exchanger assembly, comprising: a tube having
first and second ends, a length, an inner diameter and a
cross-section incorporating the inner diameter; a thermally
conductive tube insert having a length and a substantially similar
cross-section to the cross-section of the tube, the tube insert
having first and second ends and including a pair of helices
extending along the length of the tube insert, the helices having
first and second sides offset from each other by a predetermined
distance along the length of the tube insert and first and second
ends, each of the first ends offset from the other by a
predetermined angle and each of the second ends offset from the
other by a predetermined angle, the tube insert sealed within the
tube to form a first fluid flow path and a second fluid flow path,
the first fluid flow path defined between the first sides of the
helices and the second fluid path defined between the second sides
of the helices; and a plurality of inlet and outlet fluid ports for
passage of a first and second fluid into and out of the tube.
2. The heat exchanger assembly of claim 1 wherein the fluid ports
are arranged for counterflow operation whereby the first and second
fluids flow in opposite directions.
3. The heat exchanger assembly of claim 2 wherein at least one of
the inlet or outlet fluid ports in a set of fluid ports is
positioned in an opening in a wall of the tube.
4. The heat exchanger assembly of claim 2 wherein at least one of
the inlet or outlet fluid ports in a set of fluid ports is
positioned on an end of the tube.
5. The heat exchanger assembly of claim 1 wherein each of the tube
and tube insert has a substantially circular cross-section.
6. The heat exchanger assembly of claim 1 wherein the first ends of
the helices are offset from each other by an angle of 180
degrees.
7. The heat exchanger assembly of claim 1 wherein each of the
helices has a predetermined pitch which is less than the tube inner
diameter.
8. The heat exchanger assembly of claim 1 wherein the tube insert
does not extend substantially beyond the tube first or second
ends.
9. The heat exchanger assembly of claim 1 wherein the assembly
includes a first end cap sealed to the tube and tube insert first
ends and a second end cap sealed to the tube and tube insert second
ends.
10. The heat exchanger assembly of claim 9 wherein the first and
second end caps are flat, circular plates and are sealed flush with
the ends of the tube and tube insert to prevent fluid mixing inside
the heat exchanger.
11. The heat exchanger assembly of claim 1 wherein the tube insert
includes an inner expansion tube having first and second ends, a
length and a diameter less than the tube insert outer diameter, the
inner expansion tube capable of receiving an expansion mandrel
inserted therein to expand the tube insert into a tight fit with an
inner surface of the tube, the helices extending along the length
of and winding around the inner expansion tube.
12. The heat exchanger assembly of claim 11 wherein the assembly
includes a first end cap sealed to the tube, tube insert, and inner
expansion tube first ends and a second end cap sealed to the tube,
tube insert, and inner expansion tube second ends.
13. The heat exchanger assembly of claim 12 wherein the first and
second end caps are flat, circular plates and are sealed flush with
the ends of the tube, tube insert, and inner expansion tube to
prevent fluid mixing inside the heat exchanger.
14. The heat exchanger assembly of claim 1 wherein at least one of
the helices includes turbulating dimples or ridges.
15. The heat exchanger assembly of claim 1 wherein the tube and
tube insert are comprised of braze-clad aluminum.
16. The heat exchanger assembly of claim 15 wherein the helices and
tube are brazed together to create fluid-tight first and second
fluid flow paths.
17. The heat exchanger assembly of claim 1 wherein the assembly
includes a plurality of tubes with tube inserts sealed therein, the
first fluid inlet ports of each tube arranged in parallel and the
second fluid inlet ports of each tube arranged in parallel, and the
first fluid outlet ports of each tube arranged in parallel and the
second fluid outlet ports of each tube arranged in parallel, and
further including: a first inlet manifold connecting each of the
first fluid inlet ports, the first inlet manifold including a fluid
inlet port for passage of a first fluid into the heat exchanger
assembly; a first outlet manifold connecting each of the first
fluid outlet ports, the first outlet manifold including a fluid
outlet port for passage of a first fluid out of the heat exchanger
assembly; a second inlet manifold connecting each of the second
fluid inlet ports, the second inlet manifold including a fluid
inlet port for passage of a second fluid into the heat exchanger
assembly; and a second outlet manifold connecting each of the
second fluid outlet ports, the second outlet manifold including a
fluid outlet port for passage of a second fluid out of the heat
exchanger assembly, wherein the inlet and outlet manifolds are each
sealed to prevent fluid mixing inside the heat exchanger
assembly.
18. The heat exchanger assembly of claim 17 wherein the first and
second inlet and outlet manifold fluid ports are arranged for
counterflow operation whereby the first and second fluids flow in
opposite directions.
19. A method of assembling a heat exchanger, comprising the steps
of: providing a tube having first and second ends, a length, an
inner diameter and a cross-section incorporating the inner
diameter; providing a thermally conductive tube insert having first
and second ends, a length and a substantially similar cross-section
to the cross-section of the tube, the tube insert including a pair
of helices extending along the length of the tube insert, the
helices having first and second sides offset from each other by a
predetermined distance along the length of the tube insert and
first and second ends, each of the first ends offset from the other
by a predetermined angle and each of the second ends offset from
the other by a predetermined angle; inserting the tube insert
within the tube and sealing the tube insert therein to form a first
fluid flow path and a second fluid flow path, the first fluid flow
path defined between the first sides of the helices and the second
fluid path defined between the second sides of the helices; and
providing a plurality of inlet and outlet fluid ports for passage
of a first and second fluid into and out of the tube.
20. The method of claim 19 wherein the fluid ports are arranged for
counterflow operation whereby the first and second fluids flow in
opposite directions.
21. The method of claim 19 wherein the tube insert is inserted
within the tube by automation.
22. The method of claim 19 wherein each of the tube and tube insert
has a substantially circular cross-section.
23. The method of claim 19 wherein the first ends of the helices
are offset from each other by an angle of 180 degrees.
24. The method of claim 19 wherein each of the helices has a
predetermined pitch which is less than the tube inner diameter.
25. The method of claim 19 wherein the tube insert does not extend
substantially beyond the tube first or second ends.
26. The method of claim 19 wherein at least one of the helices
includes turbulating dimples or ridges.
27. The method of claim 19 further including the steps of: sealing
a second end cap to the tube and tube insert second ends; and
sealing a first end cap to the tube and tube insert first ends.
28. The method of claim 27 wherein the first and second end caps
are flat, circular plates and are sealed flush with the ends of the
tube and tube insert to prevent fluid mixing inside the heat
exchanger.
29. The method of claim 19 wherein the tube insert includes an
inner expansion tube having first and second ends, a length and a
diameter less than the tube insert outer diameter, the inner
expansion tube capable of receiving an expansion mandrel inserted
therein to expand the tube insert into a tight fit with an inner
surface of the tube, the helices extending along the length of and
winding around the inner expansion tube, and further including the
step of: inserting the expansion mandrel into the inner expansion
tube and expanding the tube insert until the tube insert is a tight
fit against an inner surface of the tube.
30. The method of claim 29 further including the steps of: sealing
a second end cap to the tube, tube insert, and inner expansion tube
second ends; and sealing a first end cap to the tube, tube insert,
and inner expansion tube first ends.
31. The method of claim 30 wherein the first and second end caps
are flat, circular plates and are sealed flush with the ends of the
tube, tube insert, and inner expansion tube to prevent fluid mixing
inside the heat exchanger.
32. The method of claim 19 wherein the tube and tube insert are
comprised of braze-clad aluminum, and further including the step
of: brazing the heat exchanger in a furnace to create fluid-tight
first and second fluid flow paths.
33. A method of operating a heat exchanger assembly, comprising:
providing a heat exchanger having a tube with first and second
ends, a length, an inner diameter and a cross-section incorporating
the inner diameter; a thermally conductive tube insert having a
length and a substantially similar cross-section to the
cross-section of the tube, the tube insert including a pair of
helices extending along the length of the tube insert, the helices
having first and second sides offset from each other by a
predetermined distance along the length of the tube insert and
first and second ends, each of the first ends offset from the other
by a predetermined angle and each of the second ends offset from
the other by a predetermined angle, the tube insert sealed within
the tube to form a first fluid flow path and a second fluid flow
path, the first fluid flow path defined between the first sides of
the helices and the second fluid path defined between the second
sides of the helices; and a plurality of inlet and outlet fluid
ports for passage of a first and second fluid into and out of the
tube; connecting inlet and outlet fluid lines for a first fluid to
a first set of inlet and outlet ports; connecting inlet and outlet
fluid lines for a second fluid to a second set of inlet and outlet
ports; and flowing the first and second fluids through the first
and second sets of inlet and outlet ports, respectively, to cool
one of the fluids.
34. The method of claim 33 wherein the first and second sets of
inlet and outlet fluid ports are arranged for counterflow operation
whereby the first and second fluids flow in opposite directions
through the first and second fluid paths between the helices.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Application No.
61/980,274, filed on Apr. 16, 2014.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to heat exchangers and, more
particularly, to liquid-to-liquid heat exchangers for use in
comparatively smaller spaces, such as in automobiles or other motor
vehicles.
[0004] 2. Description of Related Art
[0005] Designers of heat exchangers for use in automobiles and
other motor vehicles are constantly striving to obtain increased
heat transfer capability in a smaller space. In the field of
liquid-to-liquid heat exchangers, the use of turbulators on the hot
fluid side and extended surface, such as a sintered metal matrix,
on the cool fluid side, are well-known approaches to the problem.
Increasing the flow path length of the fluids while maintaining
reasonable fluid pressure drops is another approach to increased
heat transfer, but it is not usually possible to accomplish this in
a smaller space.
[0006] Therefore, a need exists for an improved heat exchanger with
superior heat transfer capabilities, which would provide for
optimum performance at the least possible cost while utilizing
standard liquid-to-liquid heat exchanger manufacturing techniques,
and providing the same in an equivalent- or smaller-sized
package.
SUMMARY OF THE INVENTION
[0007] Bearing in mind the problems and deficiencies of the prior
art, it is therefore an object of the present invention to provide
an improved heat exchanger assembly which can provide equivalent or
superior heat transfer performance in a smaller package.
[0008] It is another object of the present invention to provide an
improved heat exchanger which provides a considerable increase in
flow path length, and consequently an increase in heat transfer,
for a given tube length.
[0009] A further object of the invention is to provide an improved
heat exchanger which allows for counterflow operation, providing
optimum heat transfer performance.
[0010] It is yet another object of the present invention to provide
an improved heat exchanger which makes use of standard aluminum
liquid-to-liquid heat exchanger manufacturing techniques, such as
inner tube expansion and cab (controlled atmosphere brazing)
furnace flux brazing.
[0011] It is still another object of the present invention to
provide an improved heat exchanger which includes a helical tube
insert, thereby creating two fluid-tight fluid flow paths, each
with considerably increased length, within the tube.
[0012] Still other objects and advantages of the invention will in
part be obvious and will in part be apparent from the
specification.
[0013] The above and other objects, which will be apparent to those
skilled in the art, are achieved in the present invention which is
directed to a helical heat exchanger assembly comprising a tube
having first and second ends, a length, an inner diameter and a
cross-section incorporating the inner diameter. The helical heat
exchanger assembly includes a thermally conductive tube insert
having first and second ends and a length therebetween and a
substantially similar cross-section to the cross-section of the
tube, and a plurality of inlet and outlet fluid ports for passage
of a first and second fluid into and out of the tube. The tube
insert includes a pair of helices extending along the length of the
tube insert, the helices having first and second sides offset from
each other by a predetermined distance along the length of the tube
insert and first and second ends. Each of the helices' first ends
is offset from the other by a predetermined angle and each of the
second ends is offset from the other by a predetermined angle. The
tube insert is sealed within the tube to form a first fluid flow
path and a second fluid flow path, the first fluid flow path
defined between the first sides of the helices and the second fluid
path defined between the second sides of the helices.
[0014] The fluid ports may be arranged for counterflow operation,
whereby the first and second fluids flow in opposite directions. At
least one of the inlet or outlet fluid ports in a set of fluid
ports may positioned in an opening in a wall of the tube, or
alternatively, at least one of the inlet or outlet fluid ports in a
set of fluid ports may be positioned on an end of the tube. The
first ends of the helices may be offset from each other by an angle
of 180 degrees, and each of the helices may have a predetermined
pitch which is less than the tube inner diameter. At least one of
the helices may include turbulating dimples or ridges.
[0015] Each of the tube and tube insert may have a substantially
circular cross-section. The tube insert may be sealed inside the
tube such that the tube insert does not extend substantially beyond
the tube first or second ends, and the assembly may include a first
end cap sealed to the tube and tube insert first ends and a second
end cap sealed to the tube and tube insert second ends. The first
and second end caps may be flat, circular plates and may be sealed
flush with the ends of the tube and tube insert to prevent fluid
mixing inside the heat exchanger.
[0016] The tube insert may include an inner expansion tube having
first and second ends and a length therebetween and a diameter less
than the tube insert outer diameter, the helices extending along
the length of and winding around the inner expansion tube. The
inner expansion tube is capable of receiving an expansion mandrel
inserted therein to expand the tube insert into a tight fit with an
inner surface of the tube. The tube may include a first end cap
sealed to the tube, tube insert and inner expansion tube first
ends, respectively, and a second end cap sealed to the tube, tube
insert and inner expansion tube second ends, respectively. The
first and second end caps may be flat, circular plates and may be
sealed flush with the ends of the tube, tube insert and inner
expansion tube to prevent fluid mixing inside the heat
exchanger.
[0017] The tube and tube insert may each be comprised of braze-clad
aluminum, and the helices and tube may be brazed together to create
fluid-tight first and second fluid flow paths.
[0018] The helical heat exchanger assembly may include a plurality
of tubes with tube inserts sealed therein, the first fluid inlet
ports of each tube arranged in parallel and the second fluid inlet
ports of each tube arranged in parallel, and the first fluid outlet
ports of each tube arranged in parallel and the second fluid outlet
ports of each tube arranged in parallel. The assembly may further
include a first inlet manifold connecting each of the first fluid
inlet ports, the first inlet manifold including a fluid inlet port
for passage of a first fluid into the heat exchanger assembly, a
first outlet manifold connecting each of the first fluid outlet
ports, the first outlet manifold including a fluid outlet port for
passage of a first fluid out of the heat exchanger assembly, a
second inlet manifold connecting each of the second fluid inlet
ports, the second inlet manifold including a fluid inlet port for
passage of a second fluid into the heat exchanger assembly, and a
second outlet manifold connecting each of the second fluid outlet
ports, the second outlet manifold including a fluid outlet port for
passage of a second fluid out of the heat exchanger assembly,
wherein the inlet and outlet manifolds are each sealed to prevent
fluid mixing inside the heat exchanger assembly.
[0019] The first and second inlet and outlet manifold fluid ports
may be arranged for counterflow operation whereby the first and
second fluids flow in opposite directions.
[0020] In another aspect, the present invention is directed to a
method of assembling a heat exchanger, comprising the steps of
providing a tube having first and second ends, a length, an inner
diameter and a cross-section incorporating the inner diameter. The
method includes providing a thermally conductive tube insert having
first and second ends, a length and a substantially similar
cross-section to the cross-section of the tube, the tube insert
including a pair of helices extending along the length of the tube
insert, the helices having first and second sides offset from each
other by a predetermined distance along the length of the tube
insert and first and second ends, each of the first ends offset
from the other by a predetermined angle and each of the second ends
offset from the other by a predetermined angle, and inserting the
tube insert within the tube and sealing the tube insert therein to
form a first fluid flow path and a second fluid flow path, the
first fluid flow path defined between the first sides of the
helices and the second fluid path defined between the second sides
of the helices. The method further includes providing a plurality
of inlet and outlet fluid ports for passage of a first and second
fluid into and out of the tube.
[0021] The fluid ports may be arranged for counterflow operation,
whereby the first and second fluids flow in opposite directions.
Each of the first ends of the helices may be offset from the other
by an angle of 180 degrees and each of the second ends of the
helices may be offset from the other by an angle of 180 degrees,
and each of the helices may have a predetermined pitch which is
less than the tube inner diameter. At least one of the helices may
include turbulating dimples or ridges.
[0022] Each of the tube and tube insert may have a substantially
circular cross-section and the tube insert may be inserted within
the tube by automation. The tube insert may be inserted within the
tube such that the tube insert does not extend substantially beyond
the tube first or second ends, and the method may further include
the steps of sealing a second end cap to the tube and tube insert
second ends and sealing a first end cap to the tube and tube insert
first ends, respectively. The first and second end caps may be
flat, circular plates and may be sealed flush with the ends of the
tube and tube insert to prevent fluid mixing inside the heat
exchanger.
[0023] The tube insert may include an inner expansion tube having
first and second ends, a length and a diameter less than the tube
insert outer diameter, the helices extending along the length of
and winding around the inner expansion tube. The inner expansion
tube is capable of receiving an expansion mandrel inserted therein
to expand the tube insert into a tight fit with an inner surface of
the tube. The method may further include the step of inserting the
expansion mandrel into the inner expansion tube and expanding the
tube insert until an outer surface of the tube insert is a tight
fit against an inner surface of the tube. The method may then
include sealing a second end cap to the tube, tube insert, and
inner expansion tube second ends and sealing a first end cap to the
tube, tube insert, and inner expansion tube first ends,
respectively. The first and second end caps may be flat, circular
plates and may be sealed flush with the ends of the tube, tube
insert and inner expansion tube to prevent fluid mixing inside the
heat exchanger.
[0024] The tube and tube insert may each be comprised of braze-clad
aluminum, and the method may further include the step of brazing
the heat exchanger in a cab (controlled atmosphere brazing) furnace
to create fluid-tight first and second fluid flow paths.
[0025] In yet another aspect, the present invention is directed to
a method of operating a heat exchanger assembly, comprising the
steps of providing a heat exchanger having a tube with first and
second ends, a length, an inner diameter and a cross-section
incorporating the inner diameter. The heat exchanger includes a
thermally conductive tube insert having a length and a
substantially similar cross-section to the cross-section of the
tube, the tube insert including a pair of helices extending along
the length of the tube insert, the helices having first and second
sides offset from each other by a predetermined distance along the
length of the tube insert and first and second ends, each of the
first ends offset from the other by a predetermined angle and each
of the second ends offset from the other by a predetermined angle.
The tube insert is sealed within the tube to form a first fluid
flow path and a second fluid flow path, the first fluid flow path
defined between the first sides of the helices and the second fluid
path defined between the second sides of the helices. The heat
exchanger further includes a plurality of inlet and outlet fluid
ports for passage of a first and second fluid into and out of the
tube. The method includes connecting inlet and outlet fluid lines
for a first fluid to a first set of inlet and outlet ports,
connecting inlet and outlet fluid lines for a second fluid to a
second set of inlet and outlet ports, and flowing the first and
second fluids through the first and second sets of inlet and outlet
ports, respectively, to cool one of the fluids.
[0026] The first and second sets of inlet and outlet fluid ports
may be arranged for counterflow operation, whereby the first and
second fluids flow in opposite directions through the first and
second fluid paths between the helices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The features of the invention believed to be novel and the
elements characteristic of the invention are set forth with
particularity in the appended claims. The figures are for
illustration purposes only and are not drawn to scale. The
invention itself, however, both as to organization and method of
operation, may best be understood by reference to the detailed
description which follows taken in conjunction with the
accompanying drawings in which:
[0028] FIG. 1 depicts a perspective view of one embodiment of the
heat exchanger with helical tube insert according to the present
invention;
[0029] FIG. 2 depicts an exploded perspective view of the heat
exchanger with helical tube insert according to the present
invention, as shown in FIG. 1;
[0030] FIG. 3 depicts a perspective view of one embodiment of the
helical tube insert according to the present invention, as shown in
FIG. 2;
[0031] FIG. 4A depicts a top cross-sectional view of another
embodiment of the heat exchanger with helical tube insert;
[0032] FIG. 4B depicts an end view of the upper portion of the heat
exchanger with helical tube insert of FIG. 4A, showing a first
fluid outlet port and a second fluid inlet port;
[0033] FIG. 5 depicts a top plan view of a portion of the helical
tube insert according to the present invention as shown in FIG. 4A,
taken along length L3; and
[0034] FIG. 6 depicts a top plan view of another embodiment of the
helical tube insert according to the present invention, wherein
each of the helices includes turbulating dimples or ridges.
[0035] FIG. 7 depicts a perspective view of one embodiment of the
heat exchanger assembly including multiple helical heat exchangers
arranged in parallel and connected by inlet and outlet manifolds,
according to the present invention;
[0036] FIG. 8 depicts a cross-sectional view of the embodiment of
the heat exchanger assembly shown in FIG. 7, taken along section
B-B; and
[0037] FIG. 9 depicts a cross-sectional view of the embodiment of
the heat exchanger assembly shown in FIG. 7, taken along section
A-A.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0038] In describing the embodiment of the present invention,
reference will be made herein to FIGS. 1-9 of the drawings in which
like numerals refer to like features of the invention.
[0039] The present invention is directed to a heat exchanger
assembly including a heat exchanger tube and a helical tube insert.
The helical tube insert is sealed within a tube of substantially
similar cross-section, thereby creating two distinct fluid flow
paths within the tube. The pitch of the helical convolutions is
less than or equal to the inner diameter of the tube, in order to
obtain fluid flow paths of increased length over that of a
conventional liquid-to-liquid heat exchanger tube. The ends of the
heat exchanger tube are capped and the tube is fitted with inlet
and outlet fluid ports for each of the two fluid flow paths. The
flow paths within the heat exchanger assembly of the present
invention may be parallel flow or co-current (where the fluids move
in the same direction), or counterflow (where the direction of the
flow of one working fluid is opposite the direction of the flow of
the other fluid.) In parallel flow heat exchangers, the outlet
temperature of the "hot" fluid can never become lower than the
outlet temperature of the "cold" fluid, and the exchanger is
performing at its best when the outlet temperatures are equal.
Counterflow heat exchangers are inherently more efficient than
parallel flow heat exchangers and have several significant
advantages over a parallel flow design. The more uniform
temperature difference between the two fluids minimizes the thermal
stresses throughout the heat exchanger, the outlet temperature of
the "hot" fluid can become considerably lower than the outlet
temperature of the "cold" fluid and can actually approach the inlet
temperature of the "cold" fluid, and the more uniform temperature
difference produces a more uniform rate of heat transfer throughout
the heat exchanger, over the entire length of the fluid flow path.
The fluid connection fittings of the present invention may be
arranged for counterflow operation for optimum heat transfer
performance.
[0040] Certain terminology is used herein for convenience only and
is not to be taken as a limitation of the invention. For example,
words such as "upper," "lower," "left," "right," "horizontal,"
"vertical," "upward," and "downward" merely describe the
configuration shown in the drawings. For purposes of clarity, the
same reference numbers may be used in the drawings to identify
similar elements.
[0041] Referring now to FIG. 1, a perspective view of one
embodiment of the helical heat exchanger assembly of the present
invention is shown. The assembly includes a tube 10 of
substantially circular cross-section, having a length L1 and first
and second ends (not shown), and a helical tube insert (not shown)
of substantially similar cross-section sealed therein. Tubes having
a circular-shaped axial cross-section (i.e. perpendicular to the
axis of the tube) are typically utilized for optimum heat transfer
performance of the heat exchanger, although other tube shapes and
cross-sections may also be utilized to achieve the objects of the
present invention. The ends of the tube 10 may be sealed by a first
end cap 14 and second end cap 24 to form a self-contained heat
exchanger assembly unit. Preferably, the end caps 14, 24 are flat,
circular plates which are sealed flush with the ends of the tube
and helical tube insert to prevent fluid mixing at the interior
ends of the heat exchanger unit. The first and second end caps 14,
24 may be secured and sealed to the respective ends of the tube by
welding, solder baking, brazing or other equivalent process known
to those in the art.
[0042] Tube 10 includes a plurality of inlet and outlet fluid ports
for passage of fluid into and out of the heat exchanger assembly.
As shown in FIG. 1, the heat exchanger assembly of the present
invention includes a first fluid inlet port 40 and outlet port 42,
and a second fluid inlet port 50 and outlet port 52. The first
fluid flow path is depicted in direction 41, and the second fluid
flow path is depicted in direction 51. As shown in FIG. 2, the
fluid connection fittings as described above may be inserted into
aligned openings 30 in the wall of the tube 10 and arranged for
counterflow operation. The fluid connection fittings are positioned
per design requirements, and alternatively may be positioned, for
example, on either ends of the tube, as shown in the upper portion
of FIG. 4A and in FIG. 4B, so long as the fittings are arranged for
counterflow operation.
[0043] Referring now to FIG. 2, an exploded perspective view of the
heat exchanger assembly of the present invention, including a
helical tube insert 100, is shown. Tube insert 100 has first and
second ends 101, 102, a length L2 and a substantially similar
cross-section to that of tube 10, and is comprised of two helices
120, 130 extending along the length L2 of tube insert 100 and
offset from each other by a predetermined distance d. Each of the
helices has a first end 121, 131 and a second end 124, 134 (FIG.
6.) As shown in FIGS. 2, 4A and 4B, in a normal configuration,
helices first ends 121, 131 are adjacent tube insert first end 101,
and helices second ends 124, 134 are adjacent tube insert second
end 102. The first ends of each of the helices are offset from each
other by a predetermined angle, such as an angle of 180 degrees, as
they contact tube end cap 14 and the second ends of each of the
helices are offset from each other by a predetermined angle
(preferably the same angle as for the first ends) as they contact
tube end cap 24 (FIG. 4B.) In the embodiments shown in FIGS. 2 and
4A, the pitch p of the helical convolutions of each of the helices
120, 130 is less than the inner diameter D1 of the heat exchanger
tube 10, thereby creating two fluid flow paths, each with
substantially increased length over that of a typical heat
exchanger tube. Alternatively, the pitch p of each of the helical
convolutions may be greater than or equal to the inner diameter D1
of heat exchanger tube 10; however such a configuration will result
in a shorter fluid flow path than if the pitch p were less than the
inner diameter D1 of the tube 10. The pitch of the helical
convolution is defined as the axial advance of a point during one
complete rotation.
[0044] As further shown in FIG. 2, the helical tube insert 100 may
have an outer diameter D2 which is nominally smaller than the inner
diameter D1 of tube 10, to allow for a sliding fit therein. During
assembly of the heat exchanger, tube insert 100 is slideably
inserted into a first tube end 12 in the direction of a second tube
end 22. As shown in FIGS. 1-4A, tube insert 100 does not extend
substantially beyond the first and second tube ends 12, 22, after
insertion into tube 10. Tube insert 100 may be installed manually
or by automation during assembly of the heat exchanger unit. After
installation, end caps 14, 24 are sealed to tube ends 12, 22, tube
insert ends 101, 102, and helices ends 121, 131, 124, 134,
respectively, to form fluid-tight fluid flow paths 41, 51 inside
the heat exchanger assembly (FIG. 4A.)
[0045] As shown in FIG. 2, and more particularly shown in FIG. 3,
in an embodiment of the invention, the first ends 121, 131 of the
windings of helices 120, 130 are offset from each other by an angle
of 180 degrees, and the helices extend along the length of and are
wound around an inner expansion tube 110 of relatively small
diameter. As further shown in FIG. 3, the second ends 124 and 134
(not shown) of helices 120, 130 are also offset from each other by
an angle of 180 degrees. Inner expansion tube 110 has a first end
111 adjacent tube insert first end 101 and a second end 112
adjacent tube insert second end 102 (FIG. 4A.) As shown in FIG. 4A,
inner expansion tube 110 has a length substantially equal to the
lengths L1, L2 of tube 10 and tube insert 100.
[0046] FIG. 4A depicts a top cross-sectional view of another
embodiment of the assembled heat exchanger with helical tube
insert, showing fluid inlet and outlet ports positioned in the wall
of the tube and on one end of the tube, respectively, and arranged
for counterflow operation. As shown in FIG. 4A, each of helices
120, 130 has a first side 122, 132 and a second side 123, 133. The
respective first 122, 132 and second sides 123, 133 of the helices
are offset by a predetermined distance d along the length of tube
insert 100, creating two distinct fluid flow paths 41, 51 between
the helical convolutions. First fluid flow path 41 begins at tube
inlet 40 and ends at tube outlet 42, and is defined between the
second sides 123, 133 of the helices, while second fluid flow path
51 begins at tube inlet 50 and ends at tube outlet 52 and is
defined between the first sides 122, 132 of the helices. The pitch
p of the helical convolutions of each of the helices 120, 130 is
less than the inner diameter D1 of the heat exchanger tube 10,
thereby creating two fluid flow paths, each with substantially
increased length over that of a typical heat exchanger tube. As
shown in the bottom portion of FIG. 4A, first fluid inlet port 40
and second fluid outlet port 52 are positioned in openings in the
wall of tube 10. Fluid connection fittings positioned other than in
openings in the wall of the tube may also be used, for example,
fittings and connections at the ends of tube 10, as shown in the
upper portion of FIG. 4A, and more particularly shown in FIG.
4B.
[0047] FIG. 4B shows an end view of the upper portion of FIG. 4A,
showing first fluid outlet port 42 and second fluid inlet port 50
disposed on and integral with end cap 24. Fluid connection fittings
40, 42, 50, 52 are shown arranged for counterflow operation. In
operation of the heat exchanger, inlet and outlet fluid lines (not
shown) for first fluid flow path 41 are connected to inlet and
outlet ports 40 and 42, respectively, and inlet and outlet fluid
lines (not shown) for second fluid flow path 51 are connected to
inlet and outlet ports 50 and 52, respectively. A first fluid then
enters flow path 41 and a second fluid then enters flow path 51
through the respective sets of inlet and outlet ports, and through
the respective fluid flow paths respectively, in counterflow
operation. The first and second fluids flow in opposite directions
through the respective fluid paths between the helices to cool one
of the fluids by transferring heat through the helices to the other
fluid.
[0048] After insertion of tube insert 100 into tube 10, the outer
edges of the helices 120, 130 are sealed to the inner surface 11 of
tube 10 and the inner edges of the helices 120, 130 are sealed to
the outer surface of inner expansion tube 110 to create fluid-tight
fluid flow paths 41, 51. Any suitable sealing material may be
employed between the helices edges and tubes 10 and 110.
[0049] FIG. 5 depicts a top plan view of a portion of the helical
tube insert as shown in FIG. 4A, taken along length L3. As shown in
FIG. 5, in at least one embodiment of the present invention, inner
expansion tube 110 is capable of receiving an expansion mandrel 113
inserted therethrough. After insertion of tube insert 100 into tube
10, expansion mandrel 113 is inserted into inner expansion tube 110
to expand tube insert 100 outwardly in direction 114. Tube insert
100 is expanded such that the tube insert is a tight fit against
the inner surface 11 of tube 10, as shown in FIG. 4A, in
preparation for sealing tube insert 100 to the inner surface of the
tube to complete the assembly.
[0050] The tube insert (helices 120, 130 and inner expansion tube
110) and, optionally, the tube, are made of thermally conductive
metal, such as aluminum or copper alloys. All parts of the heat
exchanger may be made of an aluminum alloy clad with a brazing
alloy, and the unit may be flux brazed in a cab (controlled
atmosphere brazing) furnace, as per standard aluminum
liquid-to-liquid heat exchanger manufacturing techniques. Brazing
of the entire unit ensures that the edges of helices 120, 130 of
tube insert 100, which are in a tight fit against the inner surface
11 of the tube 10 and the outer surface of inner expansion tube
110, become sealed thereto, and helices ends 121, 131 and 124, 134,
are sealed to end caps 14 and 24, respectively, such that two
distinct fluid flow paths are created and no common fluid is
allowed to flow on both sides of the helices in the same direction,
ensuring optimal heat transfer, as shown in FIG. 4A.
[0051] In at least one embodiment of the present invention,
projections such as turbulating dimples or ridges of various shapes
may be incorporated by deformation or embossment of the helices
120, 130 to provide turbulation, as shown in FIG. 6. FIG. 6 shows a
tube insert 100' having turbulating dimples 140 having an oval
shape within the fluid flow paths created by and defined between
the first 122, 132 and second sides 123, 133 of helices 120, 130.
The projections may have alternative shapes such as circular,
triangular, or other geometrical shape. The projections or dimples
140 promote transfer of heat from a heated first fluid to a second
cooled fluid through the helices during operation of the
liquid-to-liquid heat exchanger of the present invention.
[0052] It should be understood that the present invention as
described above has been described in its basic form of a heat
exchanger assembly including one heat exchanger tube with helical
tube insert sealed therein. More than one heat exchanger tube with
helical tube insert may be combined into a larger heat exchanger
assembly (FIGS. 7-9), per design requirements, in accordance with
the objects of the present invention.
[0053] In such a configuration, a plurality of helical heat
exchanger tubes are positioned such that the first fluid inlet
ports of each helical heat exchanger are arranged in parallel, the
second fluid inlet ports of each helical heat exchanger are
arranged in parallel, the first fluid outlet ports of each helical
heat exchanger are arranged in parallel and the second fluid outlet
ports of each helical heat exchanger are arranged in parallel. The
assembly includes inlet and outlet manifolds connecting each of the
first fluid inlet and outlet ports, respectively, and each of the
second fluid inlet and outlet ports, respectively. Each manifold
includes a fluid port for passage of a first or second fluid,
respectively, into or out of the heat exchanger assembly. The inlet
and outlet manifolds are each sealed to prevent fluid mixing inside
the heat exchanger assembly, and the first and second inlet and
outlet manifold fluid ports may be arranged for counterflow
operation whereby the first and second fluids flow in opposite
directions.
[0054] FIGS. 7-9 depict an embodiment of the present invention
wherein a heat exchanger assembly comprises multiple helical heat
exchangers arranged in parallel and combined into a larger
assembly. As shown in FIG. 7, heat exchanger assembly 1000 includes
a first inlet manifold 200 having a first fluid inlet port 210 for
passage of a first fluid 41 into the assembly and a first outlet
manifold 300 having a first fluid outlet port 310 (not shown) for
passage of the first fluid 41 out of the assembly. The assembly
further includes a second inlet manifold 400 having a second fluid
inlet port 410 for passage of a second fluid 51 into the assembly
and a second outlet manifold 500 having a second fluid outlet port
510 for passage of the second fluid 51 out of the assembly. The
inlet and outlet manifolds are each sealed to prevent mixing of the
first and second fluids 41, 51 inside the heat exchanger
assembly.
[0055] FIG. 8 depicts a cross-sectional view of heat exchanger
assembly 1000, taken along section B-B of FIG. 7. As shown in FIG.
8, heat exchanger assembly 1000 includes three heat exchanger tubes
10, each with a helical tube insert 100 secured therein. The tubes
10 are positioned such that the second fluid outlet ports 52 of
each heat exchanger tube are arranged in parallel. The second fluid
outlet ports 52 are connected by a second outlet manifold 500.
Second outlet manifold 500 is sealed to prevent fluid mixing inside
the assembly and includes a second fluid outlet port 510 for
passage of the second fluid 51 out of the assembly. On the opposing
side of the assembly, the first fluid outlet ports 42 (not shown)
are also arranged in parallel and connected by a first outlet
manifold 300. First outlet manifold 300 is sealed to prevent fluid
mixing inside the assembly and includes a first fluid outlet port
310 for passage of the first fluid 41 out of the assembly. Any
suitable sealing material may be employed to seal the respective
manifolds. The number of heat exchanger tubes arranged in parallel
in one assembly is shown as three, for illustrative purposes only,
as an assembly including two, or more than three, heat exchanger
tubes still falls under the scope of the invention.
[0056] FIG. 9 depicts a cross-sectional view of heat exchanger
assembly 1000, taken along section A-A of FIG. 7. As shown in FIG.
9, each of the first fluid inlet ports 40 are arranged in parallel
and connected by first inlet manifold 200, and each of the second
fluid inlet ports 50 are arranged in parallel and connected by
second inlet manifold 400. First inlet manifold 200 has a fluid
inlet port 210 for passage of a first fluid 41 into the assembly,
and second inlet manifold 400 has a second inlet port 410 for
passage of a second fluid 51 into the assembly. As shown in FIG. 9,
first and second inlet and outlet manifold fluid ports 210, 310,
410, 510 are arranged for counterflow operation.
[0057] Thus the present invention achieves one or more of the
following advantages. The present invention provides an improved
heat exchanger assembly which includes a tube with helical tube
insert sealed therein, thereby creating two fluid-tight fluid flow
paths of considerably increased length within the tube. The heat
exchanger provides a considerable increase in fluid flow path
length, and consequently an increase in heat transfer, for a given
tube length, and thus provides superior heat transfer performance
over that of a typical liquid-to-liquid heat exchanger. The heat
exchanger allows for counterflow operation, providing optimum heat
transfer performance, and makes use of standard aluminum
liquid-to-liquid heat exchanger manufacturing techniques, such as
inner tube expansion and cab (controlled atmosphere brazing)
furnace flux brazing.
[0058] While the present invention has been particularly described,
in conjunction with a specific embodiment, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art in light of the foregoing description. It
is therefore contemplated that the appended claims will embrace any
such alternatives, modifications and variations as falling within
the true scope and spirit of the present invention.
* * * * *