U.S. patent application number 14/708889 was filed with the patent office on 2016-01-21 for angled tube fins to support shell side flow.
The applicant listed for this patent is Nicholas F. Urbanski. Invention is credited to Nicholas F. Urbanski.
Application Number | 20160018168 14/708889 |
Document ID | / |
Family ID | 55074306 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160018168 |
Kind Code |
A1 |
Urbanski; Nicholas F. |
January 21, 2016 |
Angled Tube Fins to Support Shell Side Flow
Abstract
A heat exchanger, including: a shell configured to have an inlet
and an outlet for a first fluid; baffles disposed in the shell,
wherein the baffles are configured to guide the first fluid into a
helical flow pattern, and at least some of the baffles are disposed
in a helical pattern with a helix angle; a tube disposed in the
shell, wherein the tube extends along a longitudinal axis of the
shell, the tube passes through the baffles, and the tube is
configured to facilitate an exchange of thermal energy between a
second fluid within the tube and the first fluid; and fins fixedly
attached to an outer surface of the tube, wherein at least some of
the fins are angled to match the helix angle of the at least some
of the baffles.
Inventors: |
Urbanski; Nicholas F.;
(Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Urbanski; Nicholas F. |
Katy |
TX |
US |
|
|
Family ID: |
55074306 |
Appl. No.: |
14/708889 |
Filed: |
May 11, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62026953 |
Jul 21, 2014 |
|
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|
Current U.S.
Class: |
165/159 |
Current CPC
Class: |
F28D 7/16 20130101; F28F
9/22 20130101; F28F 2009/228 20130101; F28D 2021/0059 20130101;
F28F 1/24 20130101; F28F 1/34 20130101 |
International
Class: |
F28F 13/06 20060101
F28F013/06 |
Claims
1. A heat exchanger, comprising: a shell configured to have an
inlet and an outlet for a first fluid; baffles disposed in the
shell, wherein the baffles are configured to guide the first fluid
into a helical flow pattern, and at least some of the baffles are
disposed in a helical pattern with a helix angle; a tube disposed
in the shell, wherein the tube extends along a longitudinal axis of
the shell, the tube passes through the baffles, and the tube is
configured to facilitate an exchange of thermal energy between a
second fluid within the tube and the first fluid; and fins fixedly
attached to an outer surface of the tube, wherein at least some of
the fins are angled to match the helix angle of the at least some
of the baffles.
2. The heat exchanger of claim 1, wherein the angle of the fins is
constant over an entire outer surface of the tube.
3. The heat exchanger of claim 2, wherein the helix angle of the at
least some of the baffles is constant.
4. The heat exchanger of claim 1, wherein the helix angle of the at
least some of the baffles varies and matches a varying angle of the
fins.
5. The heat exchanger of claim 1, wherein a height of the fins is
constant over an entire outer surface of the tube.
6. The heat exchanger of claim 1, wherein a height of the fins
varies over an entire outer surface of the tube.
7. The heat exchanger of claim 1, wherein a number of fins per unit
length of the tube is constant over an entire surface of the
tube.
8. The heat exchanger of claim 1, wherein a number of fins per unit
length of the tube varies over an entire surface of the tube.
9. The heat exchanger of claim 1, wherein the outer surface of the
tube is configured to enhance shell side fluid flow and heat
transfer performance.
10. The heat exchanger of claim 9, wherein the outer surface of the
tube is smooth, contoured, or includes smooth sections and
contoured sections.
11. The heat exchanger of claim 1, wherein the tube is configured
to have a cross-section that is configured to enhance tube side
flow and heat transfer performance.
12. The heat exchanger of claim 11, wherein an inside surface of
the tube is smooth, wavy, or includes smooth sections and wavy
sections.
13. The heat exchanger of claim 1, further comprising a plurality
of tubes that include fins angled to match the helical angle.
14. The heat exchanger of claim 1, wherein a metallurgy of the fins
is constant over an entire outer surface of the tube.
15. The heat exchanger of claim 1, wherein a metallurgy of the fins
varies over an entire outer surface of the tube.
16. The heat exchanger of claim 1, wherein the fins are high fins
that with a height of 9.0 to 32.0 mm.
17. The heat exchanger of claim 1, wherein the fins have a
different composition than the outer surface of the tube.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S. patent
application No. 62/026,953 filed Jul. 21, 2014 entitled ANGLED TUBE
FINS TO SUPPORT SHELL SIDE FLOW, the entirety of which is
incorporated by reference herein.
TECHNOLOGICAL FIELD
[0002] Exemplary embodiments described herein pertain to heat
exchangers. More specifically, some exemplary embodiments described
herein pertain to a shell-and-tube heat exchanger, wherein the tube
is fitted with angled fins.
BACKGROUND
[0003] This section is intended to introduce various aspects of the
art, which may be associated with exemplary embodiments of the
present invention. This discussion is believed to assist in
providing a framework to facilitate a better understanding of
particular aspects of the present invention. Accordingly, it should
be understood that this section should be read in this light, and
not necessarily as admissions of prior art.
[0004] A shell-and-tube heat exchanger is a class of heat
exchangers typically employed in oil refineries and other large
chemical processes. A shell-and-tube heat exchanger includes a
shell (a large pressure vessel) with a bundle of tubes inside it.
One fluid runs through the tubes and another fluid flows over the
tubes (through the shell) to transfer heat between the two fluids.
The term tube bank is often used, in the literature, to denote a
crossflow situation and bundle to indicate longitudinal flow,
however this convention is far from universal.
[0005] A shell-and-tube heat exchanger may contain a bundle of
tubes with baffles that induce and support a helical flow of the
shell side fluid from the inlet to the outlet of the unit. CB&I
Lummus provides a shell-and-tube heat exchanger based on this
technology. Helical baffles currently exist in single-helix and
double-helix configurations. A triple-helix configuration may also
exist. The tubes comprising the tube bundle of a helical baffle
heat exchanger resemble that of a conventional tube bundle: plain,
internally finned, externally finned, straight, or U-tube.
[0006] Two fluids, of different starting temperatures, flow through
the shell-and-tube heat exchanger. One flows through the tubes (the
tube side) and the other flows outside the tubes but inside the
shell (the shell side). Heat is transferred from one fluid to the
other through the tube walls, either from tube side to shell side
or vice versa. The fluids can be either liquids or gases on either
the shell or the tube side. In order to transfer heat efficiently,
a large heat transfer area should be used, leading to the use of
many tubes.
[0007] U.S. Pat. No. 8,613,308 "Process for Transferring Heat or
Modifying a Tube in a Heat Exchanger" describes a vertically
oriented shell-and-tube heat exchanger equipped with either helical
baffles or expanded metal baffles. The vertically oriented tubes
possess internal rifling that may be spiral in nature. The outer
fins are understood to be integral with the tube material and
oriented ninety degrees (90.degree.) from the longitudinal plane of
the tubes. These fins are not claimed to assist or to enhance the
shell side fluid flow through the helical or expanded metal
baffles. U.S. Pat. No. 8,613,308 is incorporated herein by
reference in its entirety.
[0008] U.S. Pat. No. 5,092,038 "Method of Manufacturing Spiral Heat
Exchanger Tubes with an External Fin" describes a method of
fabricating a heat exchanger that possesses helical ridges and
other convoluted circumferential surfaces for enhanced heat
transfer. Conventional fins may be added to the complex surface of
the twisted fin tube by conventional means. The patent describes an
integral helical fin and additional circumferential surfaces that
are formed by twisting/deforming the tube material during formation
of the tube. These fins are integral with the tube, that is, of the
same metal of which the tube is made. As such, the heights of such
fins typically range from 0.5 to 3.0 mm. These are commonly called
"low-fins." The height of these low-fins is limited by the amount
of metal available on the circumference of the tube and the
required minimum wall thickness required for mechanical viability
of the tube in service. While the patent does describe the addition
of high-fins onto the surface of the twisted fin tube surface,
these high-fins remain oriented 90.degree. from the longitudinal
plane of the tube. U.S. Pat. No. 5,092,038 is incorporated herein
by reference in its entirety.
[0009] U.S. Pat. No. 4,699,211 "Segmental High Performance Shell
and Tube Heat Exchanger" describes a concept in which the
successive baffles of a conventional segmental baffle arrangement
are rotated at angles other than 180.degree.. U.S. Pat. No.
4,699,211 is incorporated herein by reference in its entirety.
[0010] U.S. Pat. No. 2,384,714 A "Tubular Heat Exchanger" describes
what appears to be one of the first helical baffle applications
within a shell-and-tube type heat exchanger. An additional novel
concept appears to be the "nesting" of the tubes which are then
connected to a manifold residing directly within the heat exchanger
vessel. The patent does not discuss enhancements on the outside of
the tube surface to enhance shell side flow. U.S. Pat. No.
2,384,714 is incorporated herein by reference in its entirety.
[0011] Other background information regarding heat exchangers can
also be found in U.S. Pat. Nos. 8,613,308, 5,092,038, and
6,827,138, and U.S. patent publication 2009/0301699, each of which
is incorporated herein by reference in its entirety.
SUMMARY
[0012] A heat exchanger, including: a shell configured to have an
inlet and an outlet for a first fluid; baffles disposed in the
shell, wherein the baffles are configured to guide the first fluid
into a helical flow pattern, and at least some of the baffles are
disposed in a helical pattern with a helix angle; a tube disposed
in the shell, wherein the tube extends along a longitudinal axis of
the shell, the tube passes through the baffles, and the tube is
configured to facilitate an exchange of thermal energy between a
second fluid within the tube and the first fluid; and fins fixedly
attached to an outer surface of the tube, wherein at least some of
the fins are angled to match the helix angle of the at least some
of the baffles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] While the present disclosure is susceptible to various
modifications and alternative forms, specific example embodiments
thereof have been shown in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific example embodiments is not intended to limit the
disclosure to the particular forms disclosed herein, but on the
contrary, this disclosure is to cover all modifications and
equivalents as defined by the appended claims. It should also be
understood that the drawings are not necessarily to scale, emphasis
instead being placed upon clearly illustrating principles of
exemplary embodiments of the present invention. Moreover, certain
dimensions may be exaggerated to help visually convey such
principles.
[0014] FIG. 1A is an elevational cut-away view of an exemplary
shell of a heat exchanger.
[0015] FIG. 1B is a perspective view of a baffle cage with tube
bundles.
[0016] FIG. 2 shows an example of how baffles plates can be
arranged within the heat exchanger.
[0017] FIGS. 3A, 3B, 3C, 3D illustrate exemplary cross-sections of
tubes with external fins.
[0018] FIGS. 4A, B, C, and D depict the various techniques to
attach fins to the outer circumference of the tube surface.
DETAILED DESCRIPTION
[0019] Exemplary embodiments are described herein. However, to the
extent that the following description is specific to a particular,
this is intended to be for exemplary purposes only and simply
provides a description of the exemplary embodiments. Accordingly,
the invention is not limited to the specific embodiments described
below, but rather, it includes all alternatives, modifications, and
equivalents falling within the true spirit and scope of the
appended claims.
[0020] Exemplary embodiments of the present technological
advancement introduce the concept of employing angled external fins
on tubes such that they are no longer perpendicular to the
longitudinal axis of the tube (or parallel to a normal of the
longitudinal axis of the tube) and that the established external
fin angle matches that of the angle of the helical baffle
arrangement so as to better promote the establishment and
maintenance of a uniform helical flow along the shell side of a
helically-baffled heat exchanger. "Match", as used herein, does not
require that the angle of the fins be identical to the baffle
angle. Rather, the angle of the fin matches the baffle angle if it
is within +/-5 degrees.
[0021] Referring to FIG. 1A, a helically baffled heat exchanger 30
is configured with a plurality of quadrant shaped segment baffle
plates 32 each positioned at an angle .lamda. relative to a normal
N-N to a longitudinal axis A-A of a shell 34. The baffle quadrant
plates 32, (hereafter referred to as baffles), thus guide a shell
side cross flow 36 into a helical pattern and at a reduced
unsupported pipe spans between the baffles. The result is true
cross flow on the shell side with effective conversion of available
pressure drop to heat transfer and reduced risk due to minimized
vibration of tubes 40 traversed by another fluid. There are no dead
spots along the cross flow 36 for fouling, and wasted energy of
eddies or back mixing is substantially eliminated. Although the
baffles 32, as shown in the accompanying drawings, are flat, the
opposite sides of each baffle may be curved to guide the cross flow
36 along the helical pattern.
[0022] FIG. 1B provides an example of the helical baffle plates 32
with tubes 40 passing through baffle holes 50. As used herein,
baffle refers to a device to direct the shell side fluid across
tubes for optimum heat transfer. Baffles are installed on the shell
side to provide a higher heat transfer rate due to increased
turbulence and to support the tubes, thus reducing the change of
damage due to vibration.
[0023] As illustrated in FIG. 1B, a baffle cage 26, which can be a
combination of successive baffles or quadrant plates 32 positioned
at the angle .lamda. and interconnected by a plurality of tie rods
28, serves as a support for multiple tubes 40 and as a helical
guide for the cross flow 36. A bundle or coil of tubes 40 can form
the assembly of the heat exchanger that transfers energy between
the source and load fluids.
[0024] While the exemplary embodiment of FIG. 1B illustrates a
baffle cage formed of discontinuous plates, the baffle can be
formed from continuous or discontinuous plates disposed to form a
helix. The helix angle of the baffles 32 can be determined, for
example, by unwinding the helix, forming a two-dimensional
representation of the helical pattern. As illustrated in FIG. 2 for
baffle cage 26, the helix angle is determined as the arctangent of
the shell circumference C divided by the pitch p (longitudinal
distance transversed by a baffle arc extending 360.degree.. The
pitch is equal to p=C* tan (B), where B is the helix angle.
Therefore the helix angle is arctan (p/C).
[0025] The pitch (or baffle-pitch) is the center-to-center distance
between baffles, and this can be adjusted to vary the crossflow
velocity. In practice the baffle pitch is not normally greater than
a distance equal to the inside diameter of the shell or closer than
a distance equal to one-fifth the diameter or 50.8 mm (2 in)
whichever is greater. The baffle pitch can be constant or vary over
the length of the heat exchanger.
[0026] FIG. 2 shows baffles plates 32 arranged within the heat
exchanger such that the baffles at one end of the heat exchanger
have a different helix angle than baffles at an opposite end of the
heat exchanger. As illustrated in FIG. 2, heat exchanger 30 is
equipped with helical baffles 32. Baffles 32 proximate shellside
inlet 46 may have a helix angle .alpha.. Baffles 32a proximate
shellside outlet 48 may have a helix angle .beta. with respect to
longitudinal axis A-A of shell 34.
[0027] In some embodiments, baffles intermediate shellside fluid
inlet 46 and outlet 48 may have a helix angle .gamma. intermediate
that of helix angles .alpha.,.beta.. For example, the helix angles
of baffles 32 may gradually increase or decrease from inlet 46 to
outlet 48, depending on the type of service (e.g., condensing,
evaporating, etc.). In other embodiments, the helix angles for
baffles 32 may undergo one or more step changes.
[0028] .alpha.,.beta., and .gamma. can all be equal, in which case
the helix angle is constant (see, FIG. 1A for example).
[0029] The tubes 40 are fitted with external fins in order to
increase the heat-transfer area (fins not shown in FIGS. 1A, 1B and
2 for clarity). As used herein, fin is a projection on a tube in a
shell and tube heat exchanger used for increasing heat transfer.
The fin can be flattened, include ridges, be perforated, or have
other geometric enhancements. Low-fins are integral with the tube
and made of the same material as the tube. As there is only so much
tube wall material from which to form a low-fin, low-fins -extend
for a short distance above the tube surface. High-fins are not
integral with the tube material, but are rather fixedly attached to
the outer surface of the tube. While a high-fin may be of the same
material as the tube,--they are typically not (for example,
stainless steel tubes with aluminum fins). A high-fin, not being
formed from the tube material itself, allows the manufacture of
taller fins (e.g., 9 mm to 32 mm, or more) as well as additional
geometric enhancements (grooves, dimples, perforations, etc.).
[0030] FIGS. 3A-3C illustrate exemplary cross-sections of tubes 40
with external fins 300a-c. In FIG. 3A, fins 300a are angled to
match the angle of the baffle, and the height of the fins remains
constant over the entire surface of the tube 303. The angles of
helical baffles are typically range from 15 to 40 degrees. In FIG.
3A, the density of the fins (number of fins per unit length of the
tube) remains constant over the entire external surface of the tube
303. In FIG. 3B, the fins 300b are also angled to match the angle
of the baffle and have a constant height, but are displaced in a
radial direction of the tube via member 302. FIG. 3C illustrates an
example in which fins 300c have heights and densities that vary
over the entire surface of the tube 303.
[0031] The fins 300a-c do not need to be integral with the tube
material, can have a different composition than the tube material,
and can have heights ranging from 9.0 to 32.0 mm. These are
commonly called "high-fins." The height of high-fins is not limited
as that of low-fins. High-fins are not typically of the same
material as that of the tube 303 to which they are connected. In
the embodiment of FIG. 3C, fins 300c can all be high-fins or a
mixture of high-fins and low-fins.
[0032] In FIGS. 3A-3C, the angle of the fins remains constant over
the entire surface of the tube. In FIG. 3D, the angle of the fins
300d varies over the entire external surface of the tube in order
to match a varying baffle angle (i.e., FIG. 2 with different helix
angles .alpha., .beta., and .gamma.). When the fin angles and
baffle angles vary, a "match" can be determined by comparing a fin
to a baffle plate on one or both sides of the fin.
[0033] The present technological advancement can enhance heat
transfer performance. Angled fins that match the helical angle of
the baffle plates provide enhanced heat transfer by improving the
helical flow on the shell-side. The outer surface of tubes 40 can
be smooth, contoured, otherwise enhanced, or fabricated to employ a
combination of these attributes for enhanced shell side fluid flow
and heat transfer performance. The circumference of tubes 40 can be
circular, oval, wavy, otherwise enhanced, or fabricated to employ a
combination of these attributes for enhanced shell side fluid flow
and heat transfer performance. The inside surface of tubes 40 may
be smooth, wavy, otherwise enhanced, or fabricated to employ a
combination of these attributes for enhanced tube side fluid flow
and heat transfer performance.
[0034] Moreover, the various characteristics in FIGS. 3A-3D can be
mixed and matched in order to be combined in various ways that are
self-evident to those of ordinary skill in light of the teachings
of the present disclosure. The angled external fins specifically
promote and enhance the shell side fluid helical flow pattern
through a tube field (or tube bundle) within a shell-and-tube heat
exchanger employing helical baffle technology by varying fin angle,
height, density, metallurgy, or base tube arrangement and other
surface enhancements.
[0035] FIGS. 4A-D depict the various techniques to attach fins to
the outer circumference of the tube surface. In FIG. 4A, the fins
have an L-shaped connection to the outer-surface of the tube. In
FIG. 4B, the fins have an overlap L-shaped connection to the
outer-surface of the tube and an adjacent fin. In FIG. 4C, the fins
are extruded. In FIG. 4C, the fin material is wrapped around the
base tube and then pressed during fabrication such that the fin is
extruded from the material wrapped around the tube, not from the
tube material itself. In FIG. 4D, the fins are embedded in the
outer-surface of the tube.
[0036] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *