U.S. patent application number 09/759146 was filed with the patent office on 2001-09-27 for stacked plate heat exchanger for a reforming reactor.
Invention is credited to Motzet, Bruno, Tischler, Alois, Weisser, Marc.
Application Number | 20010023761 09/759146 |
Document ID | / |
Family ID | 7627331 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023761 |
Kind Code |
A1 |
Motzet, Bruno ; et
al. |
September 27, 2001 |
Stacked plate heat exchanger for a reforming reactor
Abstract
A heat exchanger has a stack of thermally conductive plate
elements, each having a wave-shaped cross sectional profile. The
plate elements are connected in a fluid-tight manner along abutting
wave profile regions to form first and second channel structures
which are separated from each other in a fluid-tight manner. The
wave profiles of the plate elements comprise at least two types of
waves of different width: a first type of wave defines the channels
of the first channel structure, and a second type of wave defines
the channels of the second channel structure. The channels of the
first channel structure have a larger passage cross section than
the channels of the second channel structure.
Inventors: |
Motzet, Bruno;
(Weilheim/Teck, DE) ; Tischler, Alois; (Aidenbach,
DE) ; Weisser, Marc; (Owen/T., DE) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS & LENAHAN, P.L.L.C.
Suite 700
1200 G Street, N.W.
Washington
DC
20005
US
|
Family ID: |
7627331 |
Appl. No.: |
09/759146 |
Filed: |
January 16, 2001 |
Current U.S.
Class: |
165/166 ;
165/167 |
Current CPC
Class: |
B01J 2219/2459 20130101;
B01J 2219/2493 20130101; B01J 2219/2453 20130101; B01J 19/249
20130101; B01J 2219/2462 20130101; B01J 2208/022 20130101; F28D
9/005 20130101; F28F 3/042 20130101 |
Class at
Publication: |
165/166 ;
165/167 |
International
Class: |
F28F 003/00; F28F
003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2000 |
DE |
100 01 065.2 |
Claims
What is claimed is:
1. A heat exchanger comprising: a stack of thermally conductive
plate elements, each having a wave profile, which plate elements
are connected in a fluid-tight manner along abutting wave profile
regions to form first and second channel structures that are
separated from each other in a fluid tight manner, wherein: wave
profiles of the plate elements comprise at least two types of
waves, with different widths; in said stack of plate elements, a
first type of wave defines at least one channel of the first
channel structure and a second type of wave defines at least one
channel of the second channel structure; and the at least one
channel of the first channel structure has a larger passage cross
section than the at least one channel of the second channel
structure.
2. A heat exchanger according to claim 1, wherein the wave profiles
comprise grooves which are spaced apart from one another by planar
plate sections, and have a cross section which is one of
semicircular and trough shaped.
3. A heat exchanger, comprising a stack of alternating first and
second thermally conductive plate elements having a plurality of
elongate parallel ridges and grooves formed therein, wherein: said
ridges of said first plate elements have a first transverse cross
sectional shape and define a first transverse cross sectional area
which is open in a first direction, and said grooves have a second
transverse cross sectional shape different from said first cross
sectional shape, and define a second transverse cross sectional
area which is open in a second direction opposite said first
direction; said second transverse cross sectional area is greater
than said first transverse cross sectional area; ridges and grooves
of said first plate elements are transversely space and aligned
with ridges and grooves of said second plate elements, whereby
ridges and grooves of adjacent stacked plate elements form first
and second channel structures, respectively; and abutting surfaces
of said ridges and grooves in adjacent plate elements in said stack
are joined in a fluid tight manner, whereby said first and second
channel structures are sealed off from each other.
4. A heat exchanger according to claim 3, wherein: said ridges are
formed by a separation of said grooves; and said second cross
sectional shape is one of undulating and trough shaped.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German patent
document 100 01 065.2, filed Jan. 13, 2000, the disclosure of which
is expressly incorporated by reference herein.
[0002] The invention relates to a stacked plate heat exchanger of
the type which is suitable for use in a reforming reactor.
[0003] Heat exchangers of this type in plate form (also known as
"disc form") are disclosed, for example, in International Patent
Document WO 97/15798 (PCT/SE96/01339). They are in use for various
applications, such as in reforming reactors for producing hydrogen
by steam reforming of a hydrocarbon or hydrocarbon derivative in
stationary or mobile installations, such as fuel cell vehicles, and
in gas-heated evaporators.
[0004] Conventionally, the plate elements have a "wave" or
corrugated profile with alternating ridges and grooves that
generally form a uniform wave structure, in which the waves are of
a single type. For example, they may be in the form of a sine wave,
and follow one another periodically without an interval between
them. This configuration leads to identical (or substantially
identical) cross sections of the two channel structures which are
separated with regard to fluid. They are formed by stacking of the
wave-profile plate elements which are connected in a fluid-tight
manner along the contact points. An associated medium can be passed
through each channel structure (for example a transverse channel
structure obtained as a result of the stack), in order to transfer
heat from one medium to another via the thermally conductive plate
elements.
[0005] For certain applications, a heat exchanger of the type
described above, in which one channel structure has a significantly
larger cross section than the other, is desirable; for example in
order to obtain a compact reforming reactor suitable in particular
for mobile applications, such as in fuel cell powered vehicles. In
such applications, one channel structure forms a reforming reaction
chamber and the other channel structure forms a temperature-control
chamber for controlling the temperature of the reforming reaction
chamber. The temperature-control chamber is responsible for the
required supply or dissipation of heat to or from the reforming
reaction chamber and, if required, may be designed in such a way
that it fulfils an additional function. For example, it may form a
catalytic burner or a CO oxidation stage which is in thermal
contact with a reforming reaction chamber via the plate
elements.
[0006] For the reforming reaction chamber, a channel structure of
relatively large cross section is desirable, so that large amounts
of catalyst material can be introduced in the form of a bed of
pellets. On the other hand, a smaller cross section is sufficient
for the temperature-control chamber. The latter may be designed,
for example, so that it can be heated by a hot gas or
temperature-control oil. Also, the smaller cross section is often
even advantageous for achieving turbulent flow conditions.
[0007] One object of the invention is to provide a heat exchanger
of the type described previously, which can be produced with
relatively little outlay.
[0008] Another object of the invention is to provide such a heat
exchanger which has channel structures of different cross section
for at least two media which are to be brought into thermal contact
with one another.
[0009] Finally, yet another object of the invention is to provide
such a heat exchanger which, where necessary, is suitable in
particular for producing a compact reforming reactor or
evaporator.
[0010] These and other objects and advantages are achieved by the
stacked plate heat exchanger according to the invention, in which
the stack of plates comprises plate elements having wave profiles
(that is, transverse cross sections) with at least two types of
waves of different width. (As used herein, the term "width" refers
to the cross-sectional area of a respective half-wave; i.e., the
integral--or cross sectional area--beneath the associated wave
curve.) One type of wave defines one channel structure, while the
other type of wave defines the other channel structure.
[0011] The arrangement of the plate elements in the stack and the
design of the wave profiles is selected so that the channel or
channels of one channel structure have a larger cross section than
those of the other channel structure. This can be achieved in a
simple way by providing different widths of the two associated
types of waves. As a result, as desired, two channel structures
with different passage cross sectional areas are provided for two
media which are to be brought into thermal contact with one another
in a compact plate-type heat exchanger
[0012] In one advantageous configuration of the invention, which
entails little manufacturing outlay, the wave profile having at
least two different types of waves is provided by forming elongate
parallel valleys or indentations in the plate element, with
semicircular or trough shaped cross sections, which indentations
are spaced at a lateral or transverse distance from one another.
These indentations form the half-waves for one type of wave, while
the resulting ridges in the area between the spaced-apart
indentations form the half-waves of the other type of wave. The
different widths for the two types of waves can be achieved, for
example, by making the (transverse) width of the indentations
significantly greater than the distance between indentations.
[0013] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a longitudinal section through a stacked plate
heat exchanger having four plate elements with a wave profile which
comprises semicircular indentations; and
[0015] FIG. 2 shows a view corresponding to that shown in FIG. 1,
but for a variant with a plate element wave profile which has
indentations in the form of troughs.
DETAILED DESCRIPTION OF THE DRAWINGS
[0016] The stacked plate heat exchanger shown in longitudinal
section in FIG. 1 comprises four plate elements 1a, 1b, 1c, 1d.
which may for example be rectangular, and are stacked on top of one
another. At their edge regions 2, they are drawn upwards in the
form of a dish, and are laid inside one another and connected in a
fluid-tight manner. In their region which is active in terms of
heat transfer, inside the edge region 2, the plate elements 1a to
1d are provided with a wave profile, as can be seen in a central
region 3 in FIG. 1. The central region 3, in the sectional plane
shown in FIG. 1, is laterally adjoined by a distribution/collection
channel 4, 5 with a channel longitudinal axis 6, 7 that runs
parallel to the stacking direction. Outside the
distribution/collection channel structure, the wave profile of the
plate elements 1a to 1d extends all the way to the edge region 2
(not shown, for simplicity).
[0017] The wave profile of the plate elements 1a to 1d
characteristically comprises two types of waves of different
widths, (i.e., different cross-sectional area F1, F2).
Specifically, in this example, in cross section the wave profile
comprises semicircular indentations 8 (or, therefore with the same
meaning, semicircular elevations), which are formed at a distance
from one another in such a manner that a web-like, planar plate
section 9 remains between each two edges 8a, 8b of adjacent
indentations, which edges face towards one another. In this manner,
the sequence of indentations 8 and planar plate sections 9 forms a
wave structure with alternating, relatively wide half-waves 10 in
the form of an arc of a circle and a relatively narrow, flattened
half-waves 11. I.e., a hybrid wave structure of quasi-alternating
wavelength.
[0018] The indentations 8 or elevations 9 are formed in the various
plate elements 1a to 1d at the same lateral positions, so that in
the plate-stacking direction indentations and elevations alternate
with one another. Consequently, on one side the arc-shaped
half-waves 10 of each inner plate element 1b, 1c bear against the
arc-shaped half-waves 10 of one adjacent plate element, and on the
other side the flattened half-waves 11 of each inner plate element
1b, 1c bear against the flattened half-waves of the other adjacent
plate element. (See FIG. 1.) Along the contact lines or areas
between the abutting arc-shaped half-waves 10 and the abutting
flattened half-waves 11 formed in this way, the plate elements 1a
to 1d are connected to one another in a fluid-tight manner, for
example by soldering or welding, in the same way as in the edge
region 2.
[0019] Consequently, this heat exchanger structure provides two
channel structures, each with a plurality of channels 14, 15
through which medium can flow in parallel. The channels 14 of a
channel structure are defined by two opposite semicircular
indentations 8 and the channels 15 of the second channel structure
are defined by two opposite flattened wave structure sections.
Since the free cross section F1 of the semicircular indentations 8
is selected to be significantly greater than the free cross section
F2 of the flattened wave regions between in each case two
indentations 8, the passage cross section for the channels 14 of
the first channel structure (which corresponds to double the free
cross section) is correspondingly larger than that of the channels
15 of the second channel structure.
[0020] As can also be seen from FIG. 1, the design of the
above-described wave profile means that the periphery of a
plurality of channels of one channel structure adjoin each channel
of the other channel structure. Thus, when the heat exchanger is
operating, with a first medium being passed through the first
channel structure and a second medium being passed through the
second channel structure, there is effective transfer of heat from
one medium to the other via the wave profile walls. It will of
course be understood that, for this purpose, the plate elements 1a
to 1d are made from a thermally conductive material, and have a
variable thickness which can be selected depending on the
application and may, for example, be small enough for the plate
elements 1a to 1d to be formed from flexible sheets.
[0021] The heat exchanger shown in FIG. 1 may, for example, be used
as a compact reforming reactor for generating hydrogen in a fuel
cell vehicle. For this purpose, the first channel structure having
the larger channels 14 is used as a reforming reaction chamber, for
which the associated channels 14 are charged with a suitable
catalyst bed. The second channel structure, having the narrower
channels 15, may be designed as a catalytic burner, as a CO
oxidation stage or simply as a temperature-control chamber for a
suitable heat-transfer medium, such as oil, glycol, etc., in order
to sufficiently heat the reforming reaction chamber channels. When
it is designed as a CO oxidation stage, the second channel
structure 15 is fed, for example, with a reformate gas for gas
cleaning, i.e. for reducing the CO concentration by selective
carbon monoxide oxidation.
[0022] In addition to efficient heat transfer, further advantages
of the heat exchanger structure shown in FIG. 1 are the low level
of manufacturing outlay and the high mechanical pressure stability
as a result of the plate elements 1a to 1d being connected in
internal contact with one another, combined with a relatively low
weight. When a catalyst bed is introduced into the channels 14
having the larger passage cross section to produce a reforming
reactor, it is possible, with a given overall size of the reactor,
to achieve a high level of reforming conversion, since a large
amount of reforming catalyst material can be introduced and the
flow of process gas in the reaction chamber channels can be well
distributed.
[0023] It will be understood that, instead of the four plate
elements shown, the modular heat exchanger structure may comprise
any other number of stacked plate elements, depending on the
requirements. As an alternative to the reforming reactor function
described above, the heat exchanger may also be used, for example,
as an evaporator for dynamic evaporation of hydrocarbons that are
used in a reforming reactor or elsewhere.
[0024] FIG. 2 shows a variant of the heat exchanger structure in
FIG. 1, which differs from the latter in terms of the
cross-sectional shape of the indentations. Specifically, in this
case elevations or indentations 8' in the form of troughs provide
the wave profile of the plate elements, which forms the flow
channels. Consequently, the associated wider half-waves 10' in this
example have a wide, flattened wave crest section, resulting in
broader or diamond-shaped contact surfaces 12', along which these
half-waves 10' of adjacent plate elements bear against one another.
Unlike in the corresponding, somewhat punctiform or linear contact
surfaces 12 from the example shown in FIG. 1, in the heat exchanger
shown in FIG. 2 there are relatively wide contact-area webs 12'. In
this region the plate elements may be provided with apertures 16,
as shown in FIG. 2, without risk of losing the seal between one of
the channels 14' of larger cross section of the first channel
structure and one of the channels 15' of smaller cross section of
the second channel structure. The apertures 16 provide fluid
communication in each case between the channels 14' of the first
channel structure of larger passage cross section, which follow one
another in series, parallel to the direction of stacking.
[0025] Otherwise, the variant shown in FIG. 2 has the same
properties and advantages as those which have been described above
in connection with the exemplary embodiment shown in FIG. 1, to
which reference may be made.
[0026] It will be understood that, within the context of the
invention, if necessary it is also possible to provide heat
exchangers whose plate elements have a wave profile with three or
more different types of waves. In that event, the associated
half-waves differ in terms of their free cross section (i.e., their
surface integral) but are of the same amplitude, so that, when two
plate elements bear against one another, the half-waves of all the
types of waves are in contact in a common plane, where they can be
connected to one another in a fluid-tight manner to form a
corresponding number of different channel structures.
[0027] By suitable selection of the wave profiles for the plate
elements parallel to the plane of the plates, (i.e., perpendicular
to the direction of stacking), it is possible, to produce different
types of channel structure, depending on requirements. For example,
it is possible to form a transverse channel structure with
rectangular plate elements by providing the plate elements with
suitable openings in the four corner regions, which form collection
and distribution channels, and otherwise with a wave profile which
is V-shaped when the plate elements are viewed from above, with two
wave profiles of adjacent plate elements running in opposite
directions in a V shape, which face towards one another in the
stack and bear against one another. The wave profiles in this case
preferably form a row of waves which follow one another in the
longitudinal direction of the plate and have a V-shaped
longitudinal extent between the two plate wide sides with a V arc
region lying approximately in the longitudinal center plane of the
plate. The V arc regions of the V waves face in the direction of
one narrow side for one plate element and in the direction of the
opposite narrow side for an adjacent plate element.
[0028] An alternative possibility is a flow channel structure which
is in the form of a set of channels, once again with rectangular
plate elements having openings in the corner regions which form
collection and distribution channels. A wave profile is provided
having a plurality of waves which, in their longitudinal direction,
extend between diagonally opposite corner-side openings. In this
case, the waves of two adjacent plate elements extend between two
different openings of the two pairs of corner-side openings which
lie diagonally opposite one another. As a result, two groups of
channel sets are formed which are arranged alternately in the plate
stack, run perpendicular to the direction of stacking, and each
extend between an associated distribution channel and an associated
collection channel. Thus, a first medium can be passed through one
half of the channel-set layers in the stack and a second medium can
be passed through the other channel-set layers which are arranged
alternately with respect to the first half in the stack, so that
the two media are brought into effective thermal contact. In the
design with a flow channel structure in the form of sets of
channels, it is possible to use wave profiles which comprise waves
of different amplitude. It is then only necessary to ensure that
the wave troughs of each one plate element are in linear contact,
along their longitudinal extent, with the wave crests of the
adjacent, facing plate element. For this purpose the waves of the
adjacent plate element have correspondingly different amplitudes.
For this embodiment, it is possible, for example, to use wave
profiles having double hump waves.
[0029] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *