U.S. patent application number 09/769770 was filed with the patent office on 2001-09-27 for apparatus for evaporating and/or superheating a medium.
Invention is credited to Motzet, Bruno, Tischler, Alois, Weisser, Marc.
Application Number | 20010023760 09/769770 |
Document ID | / |
Family ID | 7628755 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023760 |
Kind Code |
A1 |
Motzet, Bruno ; et
al. |
September 27, 2001 |
Apparatus for evaporating and/or superheating a medium
Abstract
A device for evaporating and/or superheating a medium, in
particular a hydrocarbon or a hydrocarbon/water mixture for a gas
generation system of a fuel-cell plant, includes a heat exchanger.
The heat exchanger has, in its media-side region, at least one pair
of films and in each case an inlet orifice and an outlet orifice
which are connected in each case to a media space between the two
films of the at least one pair of films. The media-side region is
in thermally conductive contact with a region located on the heat
transfer medium side. The media space is formed between the two
films by depressions introduced on the medium-facing side of at
least one of the films. The surface, facing away from the medium,
in each case of at least one of the films of the at least one pair
of films is provided with heat conducting ribs, the height of the
heat conducting ribs being greater than the depth of the
depressions.
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.
1200 G Street, N.W., Suite 700
Washington
DC
20005
US
|
Family ID: |
7628755 |
Appl. No.: |
09/769770 |
Filed: |
January 26, 2001 |
Current U.S.
Class: |
165/162 ;
165/166; 165/167 |
Current CPC
Class: |
F23K 5/22 20130101; Y02E
60/50 20130101; H01M 8/0631 20130101; F28D 9/0031 20130101 |
Class at
Publication: |
165/162 ;
165/166; 165/167 |
International
Class: |
F28D 007/00; F28F
009/00; F28F 003/00; F28F 003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2000 |
DE |
100 03 273.7 |
Claims
What is claimed is:
1. A heat exchanger for evaporating or superheating a medium,
having a heat exchange body, comprising: at least one pair of films
having a media space formed therebetween in a media side region of
said heat exchanger; and at least one inlet orifice and one outlet
orifice, each connected to the media space between the at least one
pair of films; wherein the media-side region is in thermally
conductive contact with a region of said heat exchanger located on
a heat transfer medium side of said films; the media space between
the two films is formed by depressions introduced on a
medium-facing side of at least one of the films of said at least
one pair of films; a surface facing away from the medium, in each
case of at least one of the films of the at least one pair of films
is provided with heat conducting ribs; and a height of the heat
conducting ribs is greater than a depth of the depressions.
2. The heat exchanger according to claim 1, wherein the heat
conducting ribs are arranged on at least one side of the respective
pairs of films; and the heat conducting ribs have a corrugated
configuration.
3. The heat exchanger according to claim 1, further comprising
means for fastening the heat exchanger in a self-supporting manner
in a heat transfer medium volume flow by means of conduit elements
forming inlet and outlet orifices.
4. The heat exchanger according to claim 1, further comprising a
substantially cylindrical housing.
5. The heat exchanger according to claim 4, wherein the housing has
guide plates.
6. The heat exchanger according to claim 3, wherein the heat
exchanger body is received on one of the conduit elements by means
of a fixed bearing and on the other conduit element by means of a
loose bearing.
7. The heat exchanger according to claim 6, wherein the conduit
element received via the loose bearing is surrounded by a further
conduit element connected to the housing, this conduit element
having at least one flexible conduit portion in a direction of
flow, and the conduit element being fastened to the conduit element
surrounding the conduit element, on that side of the flexible
portion which faces away from the heat exchanger.
8. The heat exchanger according to claim 1, wherein said medium
comprises one of a hydrocarbon and a hydrocarbon/gas mixture for a
gas generator for a fuel cell system.
9. A heat exchanger for heating of a fluid medium by thermal
contact with a heat transfer medium comprising: at least one pair
of films; a media space formed between said at least one pair of
films on a media side thereof for accommodating a flow of said
fluid medium; a heat transfer medium space disposed on heat
transfer medium sides of said at least one pair of films opposite
said media side, for accommodating a flow of said heat transfer
medium; a plurality of heat conducting ribs formed on said heat
transfer medium sides of said films in said heat transfer medium
space; wherein the heat transfer medium space is in thermal contact
with said media space; the media space comprises a plurality of
elongate grooves formed on the media side of at least one of said
at least one pair of films; and a height of the heat conducting
ribs is greater than a depth of the grooves.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German patent
document 100 03 273.7, filed Jan. 26, 2000, the disclosure of which
is expressly incorporated by reference herein.
[0002] The present invention relates to an apparatus for
evaporating and/or superheating a medium.
[0003] German patent document DE 44 26 692 C1 discloses a two-stage
evaporating unit for converting a liquid reactant mass flow, which
is adjustable as a function of a load presetting, into a gaseous
reactant mass flow. With the aid of a heat transfer medium the
liquid reactant mass flow is at least partially evaporated in the
first stage and, if appropriate, completely evaporated in the
second stage. Subsequently it is superheated. The evaporator unit
is formed by an alternating stacking one on the other of films with
heat transfer medium ducts and of films with reaction ducts.
[0004] Other known heat exchangers which may be used as an
evaporator unit include, for example, plate heat exchangers with
shaped metal sheets having a corrugated structure, bar/plate or
plate/fin heat exchangers or laminated heat exchangers. Heating may
take place by means of liquid and/or gaseous media.
[0005] Particularly when used in the evaporation of hydrocarbons or
hydrocarbon/water mixtures, such as, for example, are employed for
gas generation systems, the operation of evaporators of this type
is problematic. Since abrupt load changes occur frequently,
especially in mobile plants, the abovementioned evaporators can be
used here only to a limited extent. That is, by virtue of their
design, they ensure proper functioning predominantly in stationary
operation, but are often unsuitable for dynamic operation because
response times are too long.
[0006] The object of the present invention is to provide a simple
and easily implementable design of a device for evaporating and/or
superheating a medium.
[0007] Another object of the invention is to provide such a device
which can evaporate the respective media quantity efficiently and
quickly, particularly under dynamic operating conditions.
[0008] Finally, still another object of the invention is to provide
a heating apparatus which is simple and cost-effective in terms of
its design and production.
[0009] These and other objects and advantages are achieved by the
apparatus according to the invention in which a media space is
formed from the two films of at least one pair of films, by
introducing depressions into the surfaces of one or both of the
respective films which face the medium. Such depressions may be
formed, for example, by an etching method, or by a stripping or
shaping machining of the respective films. This results in a
comparatively small media space between the films, in which the
medium introduced via the inlet orifice can be evaporated and/or
superheated, with insignificant idle times, even in the case of
pronounced load jumps in the volume flow of the medium.
[0010] In order to implement the desired output of the evaporation
device, the number of installed pairs of films can simply be
increased, until the desired output can be transmitted.
[0011] At the same time, heat conducting ribs are provided on the
surfaces facing away from the medium, of at least one of the films
of the pair of films. When a plurality of pairs of films are used,
pairs of films and heat conducting ribs can thus in each case be
stacked alternately one above the other and connected to one
another. A particularly advantageous manufacturing method which may
be used for this purpose is soldering. The heat conducting ribs
serve, in particular, for increasing the heat transmission surface
and for the generation of turbulence.
[0012] On account of the size differences between the dimension of
the heat conducting ribs and the depressions in the media space,
the device according to the invention for evaporating and/or
superheating a medium is particularly suitable for evaporating
and/or superheating small media quantities per pair of films. By
virtue of the much larger heat conducting ribs on or between the
respective pairs of films, this can be carried out by means of
thermal energy from a comparatively large volume flow of a heat
transfer medium.
[0013] In this case, the heat transfer medium flowing through the
device on the heat transfer medium side may be, in particular, a
hot gas which flows around the pairs of films with a very much
larger volume flow than that of the medium to be evaporated, and at
the same time flows through the respective heat conducting ribs. In
this case, this, for example, hot gas flow can discharge a large
part of its thermal energy to the heat conducting ribs and
consequently to the films which are in thermally conductive contact
with the heat conducting ribs. Thus, this thermal energy is
transmitted to the medium located in the media space between the
two films of the at least one pair of films.
[0014] The invention consequently provides an ideal combination of
a comparatively small media-side region of the heat exchanger with
as large a region of the heat exchanger as possible on the heat
transfer medium side. Very high dynamics and a very rapid
evaporation of quantities of medium which vary abruptly are
therefore possible. At the same time, the pressure loss is low on
the heat transfer medium side. Overall, high Reynolds numbers or
heat transmission coefficients can be achieved.
[0015] 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
[0016] FIG. 1 shows a cross section through a device according to
the invention for evaporating and/or superheating a medium;
[0017] FIG. 2 shows an enlargement of a detail corresponding to the
area II in FIG. 1; and
[0018] FIG. 3 shows a longitudinal section through the device
according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows a heat exchanger 1 in cross section. As can
also be seen later in FIG. 3, the heat exchanger 1 is designed as a
self-supporting structural element and is suspended in a housing 4
via two conduit elements 2, 3. The conduit element 2 forms the
inlet orifice for a medium B to be evaporated, while the conduit
element 3 forms the outlet orifice for the vapor B'. The media-side
region of the heat exchanger 1 itself is formed by pairs of films
5, with heat conducting ribs 6 arranged between pairs of films
5.
[0020] The design of the heat exchanger 1 can be seen clearly in
FIG. 2 in an enlarged detail. Each pair of films is composed of two
films 5a, 5b, between which is located a media space 7 formed via
numerous depressions 8 in the film 5b. The media space 7 of each
pair of films 5 is connected to the conduit elements 2 and 3
forming the inlet orifice and the outlet orifice respectively.
[0021] In the exemplary embodiment illustrated in FIG. 2, the media
space 7 is formed via depressions 8 introduced (for example etched)
into the film 5b. It is of course, also possible in principle, to
form the media space 7 via depressions 8 introduced into the film
5a or into both the film 5a and the film 5b.
[0022] Particularly when the depressions 8 are produced by means of
an etching, stripping or shaping method, the shape, size and depth
and also the surface layout of the depressions 8 in the respective
film 5b and/or 5a can be configured virtually almost as desired and
can be produced in a simple way.
[0023] The heat conducting ribs 6 are mounted on the surfaces 9
facing away from the media space, and are in thermally conductive
contact with the respective films 5a, 5b. This can be implemented,
for example, by soldering. In the exemplary embodiment illustrated,
the heat conducting ribs are formed from elements which are
inserted between the individual pairs of films and which resemble
corrugated metal sheets. In principle, any other embodiments, such
as, for example, ribs, bosses, cones or the like soldered onto the
pairs of films, would also be conceivable.
[0024] Between the pairs of films 5 and the heat conducting ribs 6
are formed cavities 10, which form that region of the heat
exchanger 1 which is on the heat transfer medium side. A heat
transfer medium, in particular a gaseous heat transfer medium A,
can then flow through these cavities 10 perpendicularly to the
plane of FIG. 2.
[0025] FIG. 3 shows a longitudinal section through the heat
exchanger 1. Here too, a plurality of pairs of films 5 and the heat
conducting ribs 6 arranged between them can be seen again. A single
terminating film 11 is laid as an upper and a lower termination of
the heat exchanger 1, onto the bundle stacked alternately from the
pairs of films and the heat conducting ribs. In order to ensure
that the conduit elements 2, 3 are connected to the respective
media spaces 7 and are sealed off relative to the space surrounding
the heat exchanger 1, spacers 12 are arranged between the
individual pairs of films in the region of the conduit elements 2,
3.
[0026] The housing 4 has, in the plane perpendicular to the
inflowing heat transfer medium A or the outflowing heat transfer
medium A', at least approximately the shape of a conduit element,
here of a pipeline element of round cross section. The structure
consisting of the heat exchanger 1 and the housing 4 can thus be
integrated, without further pressure losses, into an already
existing pipeline of comparable diameter. At the same time, the
cylindrical shape of the housing 4 affords sufficient stability,
along with comparatively small wall thicknesses, with the result
that costs and weight can be saved.
[0027] It is also possible, however, to introduce the heat
exchanger 1 complete, without the housing 4, into a heat transfer
medium flow A, or to provide the housing 4 with conduit elements
perpendicularly to the depicted direction of flow of the heat
transfer medium A or A', for the supply with the heat transfer
medium.
[0028] In the exemplary embodiment illustrated in FIG. 3, guide
plates 13 are fitted into the housing 4. The guide plates 13 ensure
that the volume flow of the heat transfer medium A flows through
the region of the heat exchanger 1 and does not, for example, flow
past the heat exchanger 1.
[0029] In the exemplary embodiment illustrated, the heat exchanger
1 is designed to be self-supporting here, as already mentioned
above, and is fastened to the two conduit elements 2, 3 in the
housing 4. As regards the conduit element 2, the inlet orifice for
the medium B to be evaporated and/or superheated, the fastening is,
in principle, a fixed bearing 14. The conduit element 2 may, for
example, be screwed or welded in the housing 4.
[0030] In this case, the conduit element 3, the outlet orifice for
the evaporated and/or superheated medium B', forms, in principle, a
loose bearing 15. By means of the loose bearing 15, it becomes
possible for the conduit element 3 (and therefore also for the heat
exchanger 1) to move relative to the housing 4. Consequently,
elongations in the heat exchanger 1 caused by heating due to the
hot heat transfer medium A can be absorbed without pronounced
material stresses occurring in the materials of the heat exchanger
1.
[0031] In this case, the loose bearing is formed, in principle, by
a conduit element 16 surrounding the conduit element 3. The conduit
element 16 has two rigid end pieces 16a, 16b, a flexible conduit
portion 16c being arranged between the two rigid end pieces 16a,
16b. At the same time, the rigid portion 16a, facing the housing,
of the conduit element 16 is connected (for example welded) firmly
to the housing 4. By contrast, the conduit element 3 of the heat
exchanger 1 is connected rigidly to the conduit end 16b uncoupled
from the rigid conduit end 16a by the flexible conduit portion 16c.
This connection, too, may, for example, be a welded connection.
When the heat exchanger 1 is elongated, then, its change in length
in the housing 4 can be compensated via the loose bearing 15 or by
the flexible conduit portion 16c. Material stresses due to the
thermal elongation of the heat exchanger 1 are thereby
prevented.
[0032] The design of the heat exchanger has, in this case, great
flexibility, since only the number of pairs of films 5 and heat
conducting ribs 6 need be adapted to accommodate a desired output
to be transmitted. In principle, the heat exchanger 1 can then be
inserted into any conduit element, as the housing 4, with a
diameter suitable for this purpose, and can therefore easily be
integrated into an existing system.
[0033] By virtue of the size differences between the comparatively
small depressions 8 of the media space 7 and the comparatively
large heat conducting ribs 6, a highly dynamic response behavior of
the heat exchanger 1 can be achieved even, for example in the event
of abrupt load changes or changes in the media quantity of the
medium B to be evaporated. At the same time, the pressure loss on
the heat transfer medium side is reduced.
[0034] The device described is used preferably in fuel-cell systems
for the evaporation and/or superheating of educts. From these
evaporated educts, preferably a hydrocarbon or hydrocarbon/water
mixture, the hydrogen required for the fuel cell is then generated
in a so-called gas generation system. In this case, preferably, the
waste gas from the fuel cell is used on the heat transfer medium
side.
[0035] 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.
* * * * *