U.S. patent application number 15/003475 was filed with the patent office on 2017-07-27 for heat exchanger with enhanced heat transfer.
This patent application is currently assigned to Hamilton Sundstrand Corporation. The applicant listed for this patent is Hamilton Sundstrand Corporation. Invention is credited to Gregory K. Schwalm.
Application Number | 20170211898 15/003475 |
Document ID | / |
Family ID | 57906445 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170211898 |
Kind Code |
A1 |
Schwalm; Gregory K. |
July 27, 2017 |
HEAT EXCHANGER WITH ENHANCED HEAT TRANSFER
Abstract
A heat exchange device includes a plurality of flow passages.
Each flow passage has an inlet and an outlet configured for hot
fluid flow in a direction from the inlet to the outlet. Secondary
heat transfer elements within and adjacent each flow passage have
heat transfer characteristics varying in the direction of the hot
fluid flow such that peak metal temperatures limit creep to
acceptable values and such that transient thermal stresses are
limited to values producing acceptable life of the device.
Inventors: |
Schwalm; Gregory K.; (Avon,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hamilton Sundstrand Corporation |
Charlotte |
NC |
US |
|
|
Assignee: |
Hamilton Sundstrand
Corporation
Charlotte
NC
|
Family ID: |
57906445 |
Appl. No.: |
15/003475 |
Filed: |
January 21, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 3/02 20130101; F28F
2215/04 20130101; F28D 2001/0266 20130101; F28F 9/0246 20130101;
F28F 2265/10 20130101; F28D 1/0476 20130101; F28F 9/02 20130101;
F28F 13/14 20130101; F28F 2009/029 20130101; F28D 1/0408 20130101;
F28F 1/126 20130101; F28D 9/0062 20130101; F28F 3/025 20130101 |
International
Class: |
F28F 13/14 20060101
F28F013/14; F28F 3/02 20060101 F28F003/02; F28F 9/02 20060101
F28F009/02; F28D 1/047 20060101 F28D001/047 |
Claims
1. A heat exchange device, comprising: a plurality of flow
passages, each flow passage having an inlet and an outlet
configured for hot fluid flow in a direction from the inlet to the
outlet; and secondary heat transfer elements within and adjacent
each flow passage having heat transfer characteristics varying in
the direction of the hot fluid flow such that peak metal
temperatures, associated creep, and transient thermal stresses are
limited to values producing acceptable life of the device.
2. The heat exchange device of claim 1, wherein the heat transfer
elements are positioned proximate the inlet and the outlet and
gradually transition from straight heat transfer elements at the
inlet to shaped heat transfer elements proximate the outlet.
3. The heat exchange device of claim 1, wherein proximate the inlet
of each flow passage includes a first predetermined number of
straight heat transfer elements.
4. The heat exchange device of claim 3, wherein an intermediate
section between the inlet and outlet of the flow passage includes a
second predetermined number of straight heat transfer elements and
a third predetermined number of shaped heat transfer elements,
wherein the second predetermined number is greater than the first
predetermined number.
5. The heat exchange device of claim 4, wherein proximate the
outlet of the flow passage includes a fourth predetermined number
of shaped heat transfer elements greater than the third
predetermined number of shaped heat transfer elements.
6. The heat exchange device of claim 1, wherein the shaped fins
include wavy fins.
7. The heat exchange device of claim 1, wherein the shaped fins
allow for increased extended secondary heat transfer surface
area.
8. The heat exchange device of claim 1, further comprising: a first
section and a second section, each of the first and second sections
including the flow passages, wherein each flow passage includes
heat transfer elements positioned therein to provide increased heat
transfer in a direction from the inlet to the outlet.
9. The heat exchange device of claim 8, wherein the first and
second sections includes plate sections in a stacked arrangement
with each of the flow passages having a bend at an outer edge of
the heat exchange device configured to return high pressure fluid
to a center manifold.
10. The heat exchange device of claim 9, wherein the center
manifold includes a first plenum at one side configured to allow
fluid to enter the center manifold and a second plenum on the
opposing side configured to allow fluid to exit the center
manifold.
11. The heat exchange device of claim 10, wherein fluid flows
through the first plenum into an inlet of a respective flow passage
within the first and second sections, enters the center manifold
through an outlet of the respective flow passage, and exits the
center manifold through the second plenum.
12. A heat exchange device, comprising: a first section and a
second section, each of the first and second sections including
flow passages configured to cool fluid, each of the flow passages
having an inlet and outlet wherein each flow passage includes heat
transfer fins positioned proximate the inlet to the outlet, the
fins transition from straight fins proximate the inlet to shaped
fins proximate the outlet; and a center manifold disposed between
the first and second sections, wherein hot fluid enters the
manifold at a first plenum, passes through the first and second
sections and exits the center manifold at a second plenum.
13. The heat exchange device of claim 12, wherein the shaped fins
include wavy fins.
14. The heat exchange device of claim 12, wherein the shaped fins
include herringbone fins.
15. The heat exchange device of claim 12, wherein the shaped fins
allow for increased extended secondary heat transfer surface area.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present disclosure relates to heat exchangers, and more
particularly to plate-stack heat exchangers.
[0003] 2. Description of Related Art
[0004] Heat exchangers such as, for example, tube-shell heat
exchangers, are typically used in aerospace turbine engines and
other high temperature applications. These heat exchangers are used
to transfer thermal energy between two fluids without direct
contact between the two fluids. In particular, a primary fluid is
typically directed through a fluid passageway of the heat
exchanger, while a cooling or heating fluid is brought into
external contact with the fluid passageway. In this manner, heat
may be conducted through walls of the fluid passageway to thereby
transfer energy between the two fluids. One typical application of
a heat exchanger is related to an engine and involves the cooling
of air drawn into the engine and/or exhausted from the engine.
[0005] However, typical tube shell design heat exchangers have
structural issues when their cantilevered tube bundles are exposed
to typical aerospace vibration environments. In addition, there can
be bypass of flow around the tubes on the low pressure side of the
heat exchanger, resulting in reduced thermal effectiveness as well
as other adverse system impacts such as excessive low pressure
flow.
[0006] Traditional plate-stack heat exchangers are also used in
high temperature applications and address some of the
aforementioned structural and flow bypass issues. In prior art
applications, plate stack heat exchangers have been designed to
have a large product of heat transfer coefficient and heat transfer
surface area to achieve a large amount of heat transfer in a small
volume. However, as this product of heat transfer coefficient and
heat transfer surface area increases on the hot side of a plate
stack heat exchanger, the metal temperature increases.
[0007] As peak operating temperatures of both tube shell and plate
stack heat exchangers is increased in high temperature
applications, these prior art heat exchangers operate at conditions
such that metal temperatures in the hottest regions of the device,
specifically where the hot inlet flow and cold outlet flow are in
closest proximity are close enough to the metal melting point that
creep of the material occurs, significantly shortening the life of
the prior art device. Creep is a phenomenon whereby the material at
high temperatures deforms plastically at stresses below the yield
strength of the material. Furthermore, rapid changes in
temperatures of one or both of the heat transfer fluids flowing
through the heat exchanger result in large thermal gradients and
large resultant stresses and strains into the plastic region of the
heat exchanger material, resulting in reduced life of the heat
exchanger. These thermal gradients are typically largest near the
hottest portion of the heat exchanger.
[0008] Such conventional methods and systems have generally been
considered satisfactory for their intended purpose. However, there
is still a need in the art for improved heat exchangers with
reduced peak metal temperatures and reduced thermal gradients in
the metal of these devices during thermal transients. The present
disclosure provides a solution for this need.
SUMMARY OF THE INVENTION
[0009] A heat exchange device includes a plurality of flow
passages. Each flow passage has an inlet and an outlet configured
for hot fluid flow in a direction from the inlet to the outlet.
Secondary heat transfer elements within and adjacent each flow
passage have heat transfer characteristics varying in the direction
of the hot fluid flow such that peak metal temperatures limit creep
to acceptable values and such that transient thermal stresses are
limited to values producing acceptable life of the device.
[0010] The heat transfer elements can be positioned proximate the
inlet and the outlet and gradually transition from straight heat
transfer elements at the inlet to shaped heat transfer elements
proximate the outlet. Proximate the inlet of each flow passage can
include a first predetermined number of straight heat transfer
elements. An intermediate section between the inlet and outlet of
the flow passage can include a second predetermined number of
straight heat transfer elements and a third predetermined number of
shaped heat transfer elements, wherein the second predetermined
number is greater than the first predetermined number. Proximate
the outlet of the flow passage can include a fourth predetermined
number of shaped heat transfer elements greater than the third
predetermined number of shaped heat transfer elements.
[0011] The device can further include a first section and a second
section. Each of the first and second sections including the flow
passages, wherein each flow passage includes heat transfer elements
positioned to provide increased heat transfer in a direction from
the inlet to the outlet. The first and second sections can include
plate sections in a stacked arrangement with each of the flow
passages having a bend at an outer edge of the heat exchange device
configured to return high pressure fluid to a center manifold. The
center manifold can include a first plenum at one end configured to
allow fluid to enter the center manifold and a second plenum on the
opposing side configured to allow fluid to exit the center
manifold. Hot fluid can flow through the first plenum into an inlet
of a respective flow passage within the first and second sections,
enters the center manifold through and outlet of the respective
flow passage, and exits the center manifold through the second
plenum.
[0012] A heat exchange device includes a first section and a second
section. Each of the first and second sections including flow
passages configured to cool fluid, each of the flow passages having
an inlet and outlet wherein each flow passage includes heat
transfer fins positioned proximate the inlet to the outlet and
gradually transition from straight fins at the inlet to shaped fins
proximate the outlet. A center manifold disposed between the first
and second sections, wherein hot fluid enters the manifold at a
first plenum, passes through the first and second sections and
exits the center manifold at a second plenum.
[0013] These and other features of the systems and methods of the
subject disclosure will become more readily apparent to those
skilled in the art from the following detailed description of the
preferred embodiments taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] So that those skilled in the art to which the subject
disclosure appertains will readily understand how to make and use
the devices and methods of the subject disclosure without undue
experimentation, preferred embodiments thereof will be described in
detail herein below with reference to certain figures, wherein:
[0015] FIG. 1 is a perspective view of a prior art heat exchanger,
showing fins within flow passages forming flow channels between the
fins;
[0016] FIG. 1A is a cross-sectional view of prior art fins of FIG.
1, showing only shaped fins;
[0017] FIG. 2 is an exemplary embodiment of fins constructed in
accordance with the present disclosure, showing the transition
between straight fins to shaped fins within the flow passage;
and
[0018] FIG. 3 is a perspective view of a heat exchange device,
showing first and second sections and a center manifold.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject disclosure. For purposes of explanation and
illustration, and not limitation, a partial view of an exemplary
embodiment of a heat exchange device in accordance with the
disclosure is shown in FIG. 2 and is designated generally by
reference character 100. Other embodiments of the heat exchange
device in accordance with the disclosure, or aspects thereof, are
provided in FIGS. 1-3, as will be described. The systems and
methods described herein can be used in turbine engines exposed to
high pressure and high temperatures, for example in aerospace
application. The present disclosure provides for a device that
reduces the product of heat transfer coefficient and heat transfer
surface area in regions of the device where metal temperatures must
be limited to meet life requirements, while still maintaining a
large product of heat transfer coefficient and heat transfer
surface area where large amounts of heat transfer per unit heat
exchanger volume and weight can be achieved with reasonably low
metal temperatures from a structural perspective between the hot
and cold fluids.
[0020] With reference to FIGS. 1 and 1A a typical heat exchanger
known in the prior art is shown. Hot fluid enters through an inlet
20 at one end and passes through fin channels in flow passages to
an outlet 22 at an opposing end. Cold fluid is passed surrounding
the flow passages to transfer heat between the hot fluid within the
flow passages and the cold fluid. Typical heat exchangers include
secondary heat transfer elements, such as fins 10, within each flow
passage. As shown in FIG. 1 and in more detail in FIG. 1A,
generally these fins extend from the inlet 20 to the outlet 22 and
are equal in dimensions throughout the length of the flow passage
10. As shown in FIG. 1A, fins 10 are herringbone fins that extend
from the inlet 20 to the outlet 22.
[0021] In contrast, with reference to FIG. 2, fins 132 in
accordance with the present disclosure are shown. Fins 132 are
included within each of the flow passages 110 and fins 134 extend
from the flow passages 110. The fins 132, 134 form a solid matrix
to provide thermal and structural connection. Fins 132 provide
increased heat transfer in a direction from the inlet 120 to the
outlet 122. Straight fins 132a are positioned proximate the inlet
120 where creep and transient thermal stresses are greatest. The
straight fins 132a transition to shaped fins 132b at the outlet 122
where enhanced thermal performance is desired. Positioning straight
fins 132a at the hottest regions reduces peak temperatures and
associated creep, and peak temperature gradients and associated
thermal stresses, which in turn will provide a longer life span for
the heat exchange device. The shaped fins 132b allow for increased
extended secondary heat transfer surface area or increased heat
transfer coefficient, which is more desirable at the outlet 122.
With the variation in fins 132a, 132b, the device allows for peak
metal temperatures and thermal transient stresses that are limited
such that the device meets specified life requirements for a
specified set of operating conditions or duty cycle. Fins 132 can
be within each flow passage 110 and/or adjacent each flow passage
110. This allows the metal temperature in any given region of the
device to be affected by the heat transfer characteristics of the
heat transfer elements on both the hot and cold fins. While varying
heat transfer characteristics on just the inlet side alone can
solve the temperature and stress problems, varying heat transfer
characteristics on both inlet and outlet sides or even just the
outlet side is also suitable. The optimal configuration will depend
on the specific design. For example, cost or manufacturing
constraints could result in various design configurations.
[0022] In certain embodiments, a first predetermined number of
straight fins 132a can be positioned proximate the inlet 120. An
intermediate section of the flow passage 110 between the inlet 120
and outlet 122 can include a second predetermined number of
straight fins 132a and a third predetermined number of shaped fins
132b, where the second predetermined number of straight fins 132a
is greater than the first predetermined number 132a. Proximate the
outlet 122 a fourth predetermined number of shaped fins 132b can be
included that is less than the third predetermined number of shaped
fins 132b. Those skilled in the art will recognize that the
variation of fins as shown and described in FIG. 2 can extend to
various embodiments of heat exchanger devices without departing
from the scope of the present disclosure.
[0023] With reference to FIG. 3, one embodiment of a heat exchange
device 100 is shown. The device includes a first section 102 and a
second section 104. The first and second sections 102, 104 are two
identical heat exchange plate core sections each made up of flow
passages 110 configured for heat exchange between heat exchange
fluid within the flow passages 110 and fluid external of the fluid
passages 110. Each of the flow passages 110 includes an inlet 120
and an outlet 122 (as shown in FIG. 2) with a bend or loop 130 at
the outer edges of the device 100 to return the fluid to a center
manifold 106. The bulk of the heat transfer occurs within the flow
passages 110 of the first and second sections 102, 104.
[0024] The center manifold 106 separates the first and second
sections 102, 104 and is configured to allow high pressure fluid to
enter the manifold 106 at one end 112, pass into the flow passages
110 on either side of the manifold 106, and return to the manifold
106 to exit the manifold 106 at the opposite end 114. More
specifically, the center manifold 106 includes a first plenum 112a
at one end and a second plenum 114a on an opposing end. Fluid flows
into the first plenum 112a of the center manifold 106, passes
through a respective fluid inlet 120 of a flow passage 110, follows
a bend/loop 130 of the flow passage 106, enters the center manifold
106 again through the fluid outlet 122 and then exits the center
manifold 106 through the second plenum 114a. The design for the
first and second sections 102, 104 and the center manifold 106
facilitates installation of the proposed heat exchange device 100
in place of an existing tube-shell unit.
[0025] The methods and systems of the present disclosure, as
described above and shown in the drawings, provide for a heat
exchange device with superior properties including heat transfer
enhancements. While the apparatus and methods of the subject
disclosure have been shown and described with reference to
preferred embodiments, those skilled in the art will readily
appreciate that changes and/or modifications may be made thereto
without departing from the scope of the subject disclosure.
* * * * *