U.S. patent number 3,590,917 [Application Number 04/773,268] was granted by the patent office on 1971-07-06 for plate-type heat exchanger.
This patent grant is currently assigned to Linde Aktiengesellschaft. Invention is credited to Johann Huber, Leonhard Poth.
United States Patent |
3,590,917 |
Huber , et al. |
July 6, 1971 |
PLATE-TYPE HEAT EXCHANGER
Abstract
A plate-type heat exchanger in which the stamped plates have
corrugated central portions flanked by noncorrugated inlet and
outlet zones. The sinusoidal and trapezoidal section corrugations
of the plates are offset by half the distance between the
corrugations to form uniform cross section channels throughout the
stack. The plates are bonded together along marginal portions and
at their bearing faces with a thermosetting synthetic resin.
Inventors: |
Huber; Johann (Am Grundelberg,
DT), Poth; Leonhard (Pullach, DT) |
Assignee: |
Linde Aktiengesellschaft
(Wiesbaden, DT)
|
Family
ID: |
5680889 |
Appl.
No.: |
04/773,268 |
Filed: |
November 4, 1968 |
Foreign Application Priority Data
|
|
|
|
|
Nov 3, 1967 [DT] |
|
|
P 1601 216.1 |
|
Current U.S.
Class: |
165/166; 165/167;
165/DIG.373 |
Current CPC
Class: |
F25J
3/04412 (20130101); F28D 9/0037 (20130101); F25J
5/002 (20130101); F25J 5/005 (20130101); F25J
2290/42 (20130101); F25J 2290/44 (20130101); F28F
2275/025 (20130101); F25J 2205/24 (20130101); F25J
2250/02 (20130101); Y10S 165/373 (20130101) |
Current International
Class: |
F28D
9/00 (20060101); F25J 3/00 (20060101); F28f
003/08 () |
Field of
Search: |
;165/166,167,171 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matteson; Frederick L.
Assistant Examiner: Streule; Theophil W.
Claims
We claim:
1. A plate-type heat exchanger, comprising a stack of at least two
pairs of geometrically similar and registering rectangular plates
having congruently registering outlines, each plate being formed
with a plurality of transversely spaced corrugations parallel to
its longitudinal edges and projecting out of the principal plane of
the plate over only a central region thereof whereby the
corrugation crests define a secondary plane parallel to the
principal plane of the respective plate, each plate further having
a pair of substantially noncorrugated regions at opposite ends of
said central region lying in said principal plane and forming fluid
distribution compartments communicating with troughs between the
respective corrugations, the corrugations of each plate being
transversely offset from the corrugations of adjacent plates by
about half the transverse spacing of the corrugations, one plate of
each pair being formed with first edge portions lying in its
principal plane and second edge portions lying in its secondary
plane while the other plate of the pair is provided with second
edge portions lying in its secondary plane and sealed to the first
edge portions of said one plate of the pair while defining openings
along said edge portions communicating with the compartments of the
respective pair; and means for feeding fluid through said openings
of each pair and between said pairs of plates.
2. The heat exchanger defined in claim 1 wherein said substantially
noncorrugated regions of the plates of each pair at opposite
longitudinal ends of said corrugations are formed with
frustoconical projections reaching from each plate of the pair into
engagement with the projections of the other plate of the
respective pair whereby said projections define passages between
them communicating with said compartments.
3. The heat exchanger defined in claim 2 wherein said corrugations
have flat surfaces each engaging a flat surface of a trough of an
adjacent plate of another pair.
Description
The present invention relates to plate-type heat exchanges and,
more particularly, to heat exchangers for low-temperature
applications such as air or gas liquefaction and/or
rectification.
It has been common practice for some time to provide so-called
"plate-type" heat exchangers in which a plurality of stacked plates
are formed with channels or the like and are assembled by soldering
to provide two or more sets of compartments separated by the plates
through which heat exchange occurs.
When "plate-type heat exchangers" are concerned, they usually are
characterized by rectangular plates which define the heat transfer
partitions as well as the channels for the respective media, as
opposed to tube-type heat exchangers in which a plurality of tubes
or pipes carry one medium while the surrounding space is filled
with the other medium.
An economical manner of making plate-type heat exchangers has been
to shape the plates and assemble them together so that at least at
the peripheral zones of the plates or the boundaries of the
channels a hermetic seal is provided. To this end, prior-art
techniques have generally made use of solder seals between the
contacting faces of the stack, the molten solder being drawn by
capillarity into the region of the interface to render the seal
gastight. To solder the plates together, it has been the practice
to make use of molten or fused salt baths, heated salt beds and the
like to bring the plates to the soldering temperature. Such systems
have led to relatively high production costs with the need for
expensive equipment, etc. Even more significant, however, is the
fact that this soldering technique very often allowed fluid leakage
through insufficiently soldered portions which were inaccessible
and thus could not be repaired after assembly of the plates. As a
result, entire assemblies were discarded or torn apart with
manufacturing delays and the like. In addition, the solder joints,
if defective, were sensitive to the thermal stresses applied to the
plates when such heat exchangers were used for low-temperature
technology, e.g. for air or gas liquefaction and/or
rectification.
It is the principal object of the present invention to provide an
improved heat exchanger of relatively low cost and simple
construction with particular utility in cryogenic
installations.
A further object of this invention is to provide an improved
plate-type heat exchanger of high efficiency and low cost which
obviates the disadvantages of earlier heat exchanger devices of the
same general type.
It has now been found that an improved plate-type heat exchanger,
particularly satisfactory for use in low-temperature processes, can
be made at relatively low cost and yet be of high heat exchange
efficiency, when the heat exchanger is constituted of a stack of
heat exchange plates deformed into an undulating cross section at
least along a center region of the plates and juxtaposed such that
the longitudinally extending undulations of each plate are
transversely offset from those of the adjacent plate by
approximately one half of the distance between corresponding
undulation peaks or troughs (i.e. one half the wave length or
period of the undulations) so that the undulations define channels
of uniform cross section, the stack being assembled by an adhesive
at the contacting or closest approach regions of the plates, e.g.
at the periphery or the undulations thereof.
When the term "adhesive" is used here, it will be understood that
reference is intended to synthetic resin bonding materials,
especially thermosetting synthetic resins such as epoxy resins or
epoxyderivative resins. It has been found, surprisingly, that the
use of such adhesives in place of the solder used heretofore is
that the solder is substantially more sensitive to the surface
condition of the plates and often fails to "wet" the latter even
when the assembly is brought to the flow temperature of the solder.
Furthermore, solder bonds effectively only when the assembly has
cooled below the hardening temperature of the solder so that the
bond itself is not formed at elevated temperatures which, however,
may give rise to surface films repelling the solder. It has now
been observed, with much surprise, that the use of thermosetting
synthetic resins, especially epoxy resins, permits bonding to the
metal surface whether they are pressed together tightly or not,
whether they become coated with films or not, and whether or not
the resin is considered to be capable of "wetting" the metal. As a
purely practical matter, it has been found that such adhesives
indeed "wet" the metal as they approach their cooling temperature
in spite of the fact that at ambient temperatures that may not have
appeared to be capable of "wetting" the plates.
The resulting plate-type heat exchanger is substantially less
expensive than soldered heat exchangers, not only because of the
lower cost of the adhesive, but also because the defect rate
decreases with the use of such adhesives. The apparatus used in the
manufacture of the heat exchanger is of lower cost and the process
steps are of decreased complexity.
According to another aspect of the present invention, the
undulating profile or cross section of the heat exchanger plates is
substantially periodic in the manner of corrugations which may be
generally sinusoidal or angular when, for example, the undulations
have trapezoidal profiles. At any rate, it is found that best
results are obtained when the troughs and crests of the undulations
are geometrically similar and the undulations of the plates of the
stack are identical. In accordance with one aspect of this
invention, the crests on one side of one of the plates of the stack
bear directly upon the crests at the opposite side of the
juxtaposed plate, the latter crest forming floors of troughs in
line with the first-mentioned crests.
When troughs and crests of trapezoidal profile were assembled in
this manner, the duct for the several heat exchange fluids will
have a generally hexagonal cross section, especially when the
offset of the crests or the troughs of juxtaposed mutually adjacent
plates is one half the intercrest spacing and one half the
intertrough spacing.
An advantage of this construction, wherein each crest abuts the
floor of the trough of an adjoining compartment and vice versa, is
that the assembly has a honeycomb structure capable of supporting
the assembly mechanically against pressure differentials which may
develop between the fluids traversing the respective channels.
Furthermore, spacers within the channels can be avoided or omitted
and vibrations in the form of alternate contractions and expansions
of the channels are prevented. Since there is little change in flow
cross section as a result of pressure differentials across the
walls of the heat exchanger, the device is particularly suitable
for use as a reversing heat exchanger in low-temperature technology
wherein, for example, a gas to be liquefied is passed through one
set of channels and impurities condensed therefrom as the gas
traverses these channels in one direction. Frequently, a warm gas
must flow through the same channels in the opposite direction at a
subsequent stage while some arrangements provide for temporary
evacuation of the channels and the use of sparging gases at various
stages of the process. Since all of the channels have the identical
flow cross section in the system of the present invention, such use
of the heat exchanger as a "reversing" or "reversible" heat
exchanger is facilitated.
When the undulate plates have sinusoidal profiles, the zone of
contact between the crest of one plate and the floor of the trough
of an adjacent plate lies substantially along a line. It has been
found that such structures are susceptible to deformation,
especially when the adhesive is applied only along marginal zones
of the heat exchanger plates. Consequently, the adhesive should
also be applied at the crest-contacting surfaces of the sinusoidal
profiles.
When trapezoidal profiles are provided, contact occurs along the
small base of the trapezoid between the crest and trough of the
adjacent plates; the adhesive thus may be applied to the crests and
troughs as well as along the marginal zones of contact. The
adhesive at the crests is not vital but may be used if additional
stability is desired. It may be noted, however, that it is the
preferred arrangement to apply the adhesive at all contacting
surfaces. This ensures total lack of movement of the plates of the
heat exchanger relatively to one another both in their planes and
transverse to their planes and also precludes any fluid flow
transverse to the crests of the undulations.
According to another aspect of this invention, the plates have a
generally rectangular configuration with the flow channels defined
between and within the corrugations extending in the longitudinal
direction of the rectangle. Advantageously, the undulate portion of
each plate is formed by the central region thereof and is flanked
at the small ends of the rectangle by an inlet and outlet zone free
from the undulations and extending practically over the entire
width thereof, these zones being identical on all the plates. The
plates are thus not only mutually coextensive but preferably have
coextensive central corrugated zones and coextensive inlet and
outlet zones at either end of the undulating zone. These inlet and
outlet zones are provided with guide structures, e.g. bosses which,
together with the continuous crests and troughs produce a
right-angle flow at each end of the undulate zone. Thus the
incoming fluid is bent through 90.degree. at the inlet zone and
traverses the undulating zone before being diverted through
90.degree. again at the outlet zone. The result is a Z-shaped or
U-shaped path for the heat exchange fluid. In the latter case, the
inlet and outlet openings may be located at the same longitudinal
side of the rectangle.
As has been observed, the inlet and outlet zones of each plate are
not corrugated or of wave configuration and are subject of
deformation as a result of any pressure differential across these
plates or between the heat exchange fluids. The bosses, which are
spaced apart in both the longitudinal and transverse directions at
the inlet and outlet zones of the plates and are of frustoconical
configuration, bear upon the adjoining plates and reinforce the
stack against plate deformation under this pressure differential.
The bosses of each plate are alternately recessed therein and
pressed outwardly therefrom to opposite sides of the plate for
engagement with the inversely shaped bosses of the adjoining plate.
The circular contact surfaces of these plates may also be provided
with adhesive to bond the plates together. Additionally, the bosses
constitute projections in the path of the heat exchange fluid and
thus increase the turbulence of the fluid flow and the heat
exchange efficiency. Also, one or more bores or holes can be
provided in the inlet and/or outlet region by means of which the
heat exchange medium can be delivered to the respective sets of
channels. Fluid supply in this manner is analogous to that of the
radiator art.
To facilitate assembly of the heat exhanger and increase the
structural strength thereof, the marginal regions of each plate are
provided with a profiled ridge over part or all of the periphery,
the ridge being pressed transversely from the plate during the
stamping operation which forms the crests and troughs and the
bosses. In the spaces between two interconnected plates, profiled
bars of a cross section corresponding to these passages, can be
inserted and bonded with a thermosetting adhesive to the plates.
The ends of the heat exhanger can be supported in part by comblike
structure whose arms are inserted into the openings between each
pair of two interconnected plate edges. The profiled bars and comb
structures increase the rigidity of the assembly as well as the
fluid tightness thereof. It should be pointed out that the profiled
reinforcing bars or combs should be disposed so as not to obstruct
the openings for introduction or removal of the fluid. They may,
however, act as supports for housing structures designed to enclose
the stack of plates and to introduce or remove the fluids from the
channels.
To increase the structural strength of the unit, we provide that
the stack of relatively thin sheet metal plates is flanked along
their broad surfaces by a pair of relatively thick-walled cover
plates whose surfaces turned away from the stack are smooth or flat
while the surfaces of these thick plates turned toward the stack
are corrugated or undulated corresponding to the corrugations of
the plates against which they bear.
According to still another feature of this invention, the stack of
plates forming the body of the heat exchanger is composed of plates
of unit construction and is symmetrical about a median plane
through the stack whereby the plates may merely be reversed with
respect to one another, stacked, cemented together with adhesive
and assembled into the desired configuration. Moreover, it has been
found to be advantageous to secure between plates of each pair
defining an array of channels or passages for the fluids with their
respective corrugations, throughs or crests, spring-ribbed sheet
metal strips, preferably of profiled cross section, which increase
the turbulence of the fluids passing through the channels. The
strips may be of sinusoidal configuration or trapezoidal
configuration, as will be apparent hereinafter, and formed with
flanks generally parallel to the direction of fluid flow through
the channel and to the crests and/or troughs in which they are
housed. These flanks may extend along the channels to subdivide
them into a plurality of parallel compartments and may be formed
with pockets, projections, protuberances or other formations which
interfere with laminar flow along these flanks and promote
turbulence.
The plates of the stack of the present heat exchanger are
preferably formed of a material of high thermal conductivity which
also is usually stamped, e.g. copper, brass, aluminum or aluminum
alloy. Best results are obtained with aluminum and its alloys
although chromium-nickel-steel plates may also be employed.
The above and other objects, features and advantages of the present
invention will become more readily apparent from the following
description, reference being made to the accompanying drawing, in
which:
FIG. 1A and FIG. 1B are plan views from the top of a lower plate
and upper plate, respectively, forming a stack in accordance with
the present invention for a plate-type heat exchanger;
FIG. 2 is a perspective view in exploded form of the plate stack of
a heat exchanger in accordance with another embodiment of our
invention;
FIG. 3 is a view similar to FIG. 2 illustrating yet another
embodiment;
FIG. 4 is a perspective exploded view of the plate stack of a heat
exchanger according to this invention wherein one fluid describes a
U-shaped path while the other fluid a substantially straight
path;
FIG. 5 is a cross-sectional view through a plate-type heat
exchanger embodying the present invention;
FIG. 6 and FIG. 7 are fragmentary perspective views of heat
transfer elements adaptEd to be used in the system of FIG. 5;
FIG. 8 is an enlarged cross-sectional view of a fragment of a heat
exchanger stack showing the use of the thermosetting resin to bond
the plates together;
FIG. 9 is a partial perspectIve view of another plate assembly;
FIG. 10 is a view similar to FIG. 8, showing the application of the
principles of the present invention to a heat exchanger using
plates of sinusoidal profile;
FIG. 11 is a cross-sectional view of another embodiment of this
invention;
FIG. 12 is a plan view of a plate according to another feature of
this invention;
FIG. 13 is a fragmentary elevational view diagrammatically
illustrating a method of assembling and stiffening the stack;
and
FIG. 14 is a cross-sectional view of the boss arrangement of the
plates in FIGS. 1--4.
In FIGS. 1A and lB, we have shown a pair of plates 1 and 11 for a
plate-type heat exchanger in which the plates may be stacked (FIG.
5 or 8), reinforced by the fingers of a comb support (FIG. 13) and
bonded at its boss structure (FIG. 14). The lower plate of this
embodiment, shown in FIG. 1A, is a pressed or stamped rectangular
sheet metal body 1 having a central zone C spaced inwardly from the
narrow ends of the plate by the zones I and O respectively
constituting the inlet and outlet sides of the plates and which are
free from corrugations. The central zone C of the plate is formed
with a plurality of mutually parallel transversely spaced
corrugations of trapezoidal cross section both in the longitudinal
plane P and in the transverse plane P, the crests 3 of the
corrugations rising out of the plane of the paper in FIG. 1A.
The narrow base of each trapezoid 3 rests upon the downwardly
turned narrow face of the troughs of an upper plate. The trapezoids
are open at their wide bases. At the inlet side I, the plate 1 has
a zone 4 which is free from the corrugations 2, 3 and is provided
with stamped bosses 6 which rise out of the plane of the paper and
are of frustoconical configuration as shown, for example, in FIG.
14. The bosses 6 have a height corresponding to that of the crests
3.
Along part of the periphery of the plate 1, we have formed sealing
ridges 7, 8, 9 and 10, which completely surround the formations 2,
3, 6 except at inlet 18 and outlet 19 along the right-hand
longitudinal side of plate 1. The sealing surfaces 7--10 may be
coated with adhesive (FIG. 11) and are of the same height as the
bosses 6 and the crests 2 and 3. A similar array of bosses 6 is
provided at the noncorrugated outlet side as represented at 5.
The upper plate 11 (FIG. 1B), which is designed to be placed upon
the plate 1 of FIG. 1A, may be identIcal with plate 1 but rotated
in its plane through 180.degree.. When the plate 11 is then placed
upon the plate 1, the raised surfaces 7--10 of the latter abut the
nonraised sealing surfaces 12, 13, 14 and 15 of plate 11 and are
hermetically sealed relatively thereto with a thermosetting
adhesive as described in connection with FIGS. 8--12 and 14.
The crests 3 of plate 1 are brought to bear against the floors 16
of plate 11 so that hexagonal channels are formed as shown in FIGS.
5 and 8. The bosses 6 are so constituted that they alternately
project from the surface (boss 6') or are recessed therein (6");
thus the recessed bosses 6" of plate 11 rest upon the upstanding
bosses 6' of the plate 1 (see FIG. 14).
A layer TP.sub.1 of thermosetting synthetic resin is provided
between the juxtaposed sealing faces of these bosses. Plates 1 and
11 are hermetically sealed with this resin over all of their
mutually contacting surfaces. The plates can be stacked without
separators and the gaps between the plates formed by the
corrugations 2 charged with the heat exchange media.
In the system of FIG. 1, in which plate 11 is placed upon plate 1,
one heat exchange medium is introduced at 17 and passes through the
inlet 18 about the bosses 6 and is then deflected through the
spaces between the crests prior to deflection outwardly through the
outlet 19. The result is a U-shaped flow pattern. A countercurrent
flow of the other gas stream along the opposite surfaces of plate
11 is represented by arrows 20. The gas here passes into the
assembly through inlet 21 and then flows along the valleys or
troughs 16 prior to emerging from the system in a U-shaped pattern.
The fluid stream, in each case, is deflected twice through angles
of 90.degree..
In FIG. 2, an exploded view of a modified stack of plates has been
illustrated, the plates 25, 26, 27 and 28 being of totally
identical configuration with every other plate being rotated in its
plane through 180.degree.. As in the system of FIG. 1, the marginal
portions 29 and 30 of plate 26 project toward the corresponding
marginal portions 33 and 34 of plate 25 by a distance t equal to
one half the combined altitudes a of the bosses 37, 38 and,
therefore, the altitudes A of the channels formed between the
plates (FIG. 5). The plates 25 and 27 and the plates 26 and 28 thus
are oriented similarly. When the plates 26 and 28 are assembled
together, the boundary surfaces 29, 30, 31 and 32 of the plate 26
engage the boundary surfaces 33, 34, 35 and 36 through layers of
thermosetting adhesive applied as shown at TP.sub.2 to the boundary
portions in FIG. 12. The troughs 16 of the trapezoidal corrugations
2 of plate 25, which have the same configuration as the
correspondingly numbered portions of FIG. 1, bear against the crest
3 of the undulations of the opposite plate, thereby forming between
these plates six-sided channels as shown in FIG. 5.
The noncorrugated inlet and outlet sides 4 and 5 of the plates
25--28, are provided with the bosses 37 and 38 which correspond to
the bosses 6, 6', 6", and which alternately stand out from the
plate or are pressed rearwardly therefrom. The bosses 37 of plate
26 for example, bear against the bosses 38 of plate 25 (see FIG.
14). This construction of the plate allows each plate to rest
against the neighboring plate at a multiplicity of locations,
thereby rendering the entire assembly substantially resistant to
pressure differentials between the fluids.
The adhesive is preferably applied to the plates over all of their
bearing locations and the system thereafter assembled and subjected
to heat treatment at the curing temperature of the resin.
In the openings 40 between the pairs of plates, there are provided
reinforcements in the form of the arms 100 of a comb 101 or as
profiled rods which fill the space between the surfaces 41 and 29
of plates 26 and 27, (see FIG. 13). Manifold chambers are provided
at 103. Similar arms can be received in the openings 102 inwardly
of the marginal portions 29 and 33 or 39 and 40 of the pairs of
plates. The arms 100, of course, have a cross section identical to
that of the openings in which they are received. Suitable profiled
bars for insertion in these openings have been shown at 91 and are
received in the openings in the narrow end sides of the stack. The
thermosetting bonding agent is applied to the bearing surfaces of
the plates, the profiled bars 91 and/or the arms 100 of the
assembly. The bars 91 (FIG. 5) increase the compressive strength,
stiffness and fluid tightness of the assembly. The profiled bars
need not extend the full length of the openings in which they are
inserted to accommodate inlets and outlets for the heat exchange
medium which, in the embodiments of FIG. 2, is represented by the
arrow 42 and passed in a U-shaped path from the inlet openings 43
to the outlet openings 44 between the plates.
The other heat exchange medium is represented by the arrow 45 and
flows along an inserted U-shaped path through the inlet 46 to the
outlet 47 between the plates 26 and 27 in countercurrent to the
first-mentioned medium 42. The collecting and manifold chambers of
the heat exchanger are represented at 103 in which they are shown
to be attached to bosses or other formations on the profiled bars
91 and/or the support comb 101. The chambers may be hoods welded to
these members (FIG. 13).
The flow cross section of the fluid mediums 42 and 45 can be
interchanged for operation of the heat exchanger as a so-called
"reversing exchanger" inasmuch as the flow cross section between
each pair of plates is identIcal. The two mediums which are passed
in heat-exchanging relationship, may have inlets in the form of two
manifold chambers on the left side of the stack and two manifold
chambers on the right side of the stack respectively for the
functional interchange of the mediums in their flows through the
respective channels.
The heat exchanger stack illustrated in FIG. 3 comprises the plates
50--53 which operate with three different mediums. The plates are
basically similar to those of FIGS. 1A, 1B and FIG. 2 and have
trapezoidal section longitudinal undulations over the central
region as described in connection with these Figures. The inlet and
outlet ends of the plates are free from such crests or troughs but
are formed with frustoconical bosses which bear upon one another
and are bonded together by the thermosetting synthetic resin.
When the plates 50 and 51 are bonded together at their peripheral
surfaces 54--57 and 58--61, respectively, the usually confronting
bosses and crests are similarly joined. Plates 50 and 51 define
between them a U-shaped flow path wherein a first medium
(represented by arrow 62) enters at an inlet 63 and exits through
an outlet 64 between this pair of plates. The boundary surfaces
58--61 of plates 51 are so contoured that between the plates 51 and
52 a linear flow path exists for a second medium 65 which, when the
plates are bonded together by the thermosetting resin, cannot mix
with the medium 62 and which enters at the narrow side 66 while
departing at the narrow sides 67 of the assembly. Plate 50
corresponds to the plates 25 and 27 of FIG. 2 while plate 53
corresponds to plates 52 but is rotated in its plane 180.degree.
with respect to the other. The space between plates 52 and 53 can
sustain the flow of a third medium 68 in the same flow direction as
medium 65. Between plates 53 and a subsequent plate of the stack
(not shown), the channels are formed as in plates 52 and 50 and a
flow path is provided for the first medium 62.
The heat exchanger stack of FIG. 3 can be used with considerable
advantage in air rectification wherein air, oxygen and nitrogen
constitute the first, second and third medium. Since the flow cross
sections of all the plates are identical, the channels my be used
interchangeably for reversing heat exchanger relationship.
The stack of FIG. 3 requires two manifold chambers for the medium
62 and 68 on the right and left sides of the unit respectively and
a further pair of collecting chambers along the upper and lower
sides of the stack. When the stack is modified so that plate 51 is
rotated in its plane through 180.degree., thereby providing its
inlet and outlet openings on the right rather than the left side of
the unit, four mediums can be used, e.g. air, nitrogen, oxygen and
a turbine gas which is to be heated for operating a low-temperature
expansion turbine. The latter stack requires eight collecting
chambers, two at each longitudinal side and two at each of the
narrow sides of the plates.
The stack of FIG. 4 provides the four plates 70, 71, 72 and 73 of
which plates 70 and 72, and plates 71 and 73 are identical in form
and position. The direct stacking of the plates (within intervening
layers of thermosetting synthetic resin to bond them together as
described in connection with FIG. 2) forms a heat exchanger
assembly in which gas flow paths as represented by the arrows 80
and 83 can be sustained. The trapezoidal corrugations 2 are pressed
from the sheet metal plates and extend perpendicular to the plane
of the paper but, with respect to the alternate plates, are offset
from one another by half the intercorrugation distance. The
boundary zone 74--77 of plate 71 bears against corresponding
surfaces of plate 70 via the intervening thermosetting layer so
that between plate 70 and 71 and between 72 and 73 U-shaped flow
paths 80 are constituted, the inlet 78 and the outlet 79 being
formed with interruptions in the marginal strip 74--77. Between
plates 71 and 72, the superimposition of the plates produces a
linear flow path as represented at 83 from the underside of the
stack to exit at the upper side thereof. A plate-type heat
exchanger as shown in FIG. 4 has been found to be particularly
suitable for use as an evaporator-condenser, e.g. in the upper
column of a double rectification column for the separation of air
into nitrogen and oxygen in accordance with the Linde-Frankl
rectification system. In this case, a central duct leads nitrogen
vapor from the lower column to the heat exchanger as the first
medium 80 to condense the latter while liquid oxygen passes
directly through the unit and is vaporized. When the thermosetting
resin may be sensitive to deterioration in contact with liquid
oxygen, the oxygen flow chamber may be closed by ultrasonic
welding.
FIG. 5, as has been noted, shows the honeycomb section of a
platelike heat exchanger in accordance with the invention and in
which the broad open bases of the trapezoid register with one
another to form hexagonal channels 90. The crest of each one of the
corrugations of a lower plate is bonded to the floor of the trough
of a plate superimposed thereon. Each of the channels may have a
cross section with a hexagonal side length S of 2 to 3 mm. Between
each pair of juxtaposed-plate edges and the edges of an adjacent
pair, there are formed openings which receive the profiled rods 91
or the arms 100 mentioned earlier. Furthermore, at each of the
broad ends of the heat exchanger stack, parallel to the plates,
there is provided a relatively massive terminal plate 92 whose
outer surface 92a is flat while the inner surface is formed with
solid corrugations 92b which are received in the initial plate 92c.
The result is a more rigid heat exchanger structure and a
fluidtight seal.
To increase the heat exchange surface area, one or more channels
may be provided with a longitudinally extending heat transfer
element 93 or 94 shown in enlarged scale in FIGS. 6 and 7. The
sheet metal elements, which may span the width of the channels, act
as partitions whose flanks 93a, 93b and 94a subdivide the channels
into compartments on opposite sides of these partitions. The
partitions are provided with pockets 95, 96 which project into the
path of the fluid to produce turbulence. A sinusoidal heat transfer
element is shown at 94 while the element 93 is of trapezoidal
configuration.
In FIG. 8, I have shown the honeycomb structure of FIG. 5 wherein
contact is made between the small bases of the trapezoidal
channels. The synthetic resin layer TP.sub.3 is here coextensive
with the small-base portions 108 and bonds the plates 109, 110, 111
and 112 together. As has been pointed out, a sheet metal partition
113 can be introduced between the small bases 108 of the
trapezoids, with the usual intervening layer TP.sub.4 of
thermosetting synthetic resin. The undulating portions 115 and 116
on opposite sides of the plate 113 may be perforated as shown at
117 (FIG. 9) or provided with teeth (FIG. 11).
It has also been pointed out that the corrugations may be of
generally sinusoidal configuration as is shown, for example, for
the plates 118, 119 and 120 in FIG. 10. At the mutually approaching
crests and troughs of this assembly, strips TP.sub.5 of
thermoplastic synthetic resin are provided to bond the stack into a
heat exchange unit. Between the crests and the troughs, a partition
121 can be disposed (FIG 11) and bonded to the plates 122 and 123
by thermosetting synthetic strips TP.sub.6. Again, the plates may
be perforated or formed with teeth as shown at 124 in FIG. 11.
FIG. 12 has shown a plate to be stacked with similar plates in a
heat exchange structure and herein the marginal edge 125 of the
plate is continuous but is provided with the thermoplastic adhesive
coating previously mentioned. A pair of bores 127 at the
uncorrugated inlet side of the plate 128 serve to admit the heat
exchange fluid (129) and permit it to pass the bosses 130 which
extend alternately upwardly and downwardly from the plane of the
plate. The flow paths (arrows 131) are of Z-shaped configuration
and lead to the outlet bores 132.
EXAMPLE
A plate-type heat exchanger using the configuration of FIG. 2, is
assembled so that the six-sided longitudinally extending channel
have a hexagonal side length S of 3 mm. or 2 mm. in tests A and B
while the wall thickness s of the plates is 0.3 mm. and 0.2 mm. The
plates were composed of aluminum and cemented together with epoxy
heated at the curing temperature in the usual manner. The following
table lists the parameters and the results achieved: ##SPC1##
The improvement described and illustrated is believed to admit of
many modifications within the ability of persons skilled in the
art, all such modifications being considered within the spirit and
scope of the invention except as limited by the appended
claims.
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