Note: Descriptions are shown in the official language in which they were submitted.
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10 90329
This invention relates to plate heat exchangers characterized
by the geometry and the particular assembly of bumped plates
together with collector plates and also to particular appli-
cations of the same.
In a general way heat exchangers are known with very different
designs, according to a variety of functional necessities.
In the range of plate heat exchangers one knows the dismount-
able ones, made of a stack of corrugated plates, with peri-
pheric hermetic gaskets which contain a suitable gap between
the said plates. One knows the heat exchangers with fixed
corrugated plates, mounted in a housing with spacers and
fixed for example by glueing.
The corrugations support the turbulence in the fluid flow,
giving structural rigidity at the same time.
One uses also pocket shaped heat exchangers, made of rigid
plates with spacers fixed by soldering for example. Well
known are the plate heat exchangers with primary and second-
ary surfaces made as an assembly of flat metallic sheets,
operating as primary surfaces and intermediate layers of
metallic cut and pressed sheet acting as spacers and second-
ary heat exchanging fins as well the assembly being finished
by soldering or brasing.
Furthermore, different designs of heat exchanger plates have
been described in specialized literature. Up to now they did -
not come into general use, probably due to problems subsisting
- in connection with assembly and fluid collection.
According to a broad aspect of the present invention, there
is provided a counter current heat exchanger comprising a
plurality of spaced apart parallel plates having spacer means
therebetween for separating said plates and for spreading the
flow of fluid between said plates over the entire surface area
- of said plates, housing means completely closing the spaces
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1090329
between said plates along two opposed sides of said plates,
said housing means defining a plurality of rows of spaced
- apertures between said plates along the other two opposed
~ sides of said plates with the apertures in alternate rows
;; being offset from each other, primary inlet and outlet col-
lector means secured to said housing means and co-extensive
with the sides of said housing means having said apertures,
each of said collector means comprised of the one-piece zig-
. zag shaped wall member with adjacent portions of said wall
member being disposed at right angles to each other so that
alternate portions of said wall members are parallel to each
other, said parallel wall portions having identical triangu-
lar configurations disposed perpendicular to said plates bet-
ween said apertures so that alternate spaces between said
~ triangular plates communicate with the apertures in alternate
;; rows and secondary inlet and outlet collector means being
comprised of wall means surrounding said primary collector
means and disposed perpendicular to said apertured sides of
.~ said housing means, each of said secondary collector means
20 in conjunction with each primary collector means defining two
plenum chambers each having a triangular cross-section on
~; opposite sides of said primary collector means.
A heat exchanger conforming to the present invention is char-
. acterized by the special geometry and the particular way of
. assembling of pressed plates, which together make a compac-t,
~ rigid heat exchanger, having only primary heat exchanging
:t surfaces, as is explained in the following text and associated
figures.
. Figure 1 illustrates a design of dents or bumps which can be
. 30 used,
: Figure 2 illustrates a different design of dents or bumps
which can be used,
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Figure 3 illustrates an assembly of plates:Figure 4 illustrates a possible way for stopping a peripheric
zone:
Figure 5 illustrates an alternative for stopping:
Figure 6 illustrates a possible means of stopping peripheric
zones close to orifices, and a procedure of stopping by
casting
Figure 7 illustrates by two sections and one view a typical
counter flow heat exchanger:
Figure 8 illustrates three sections of a counter flow heat
exchanger with multiple orifices,
Figure 9 gives a general view of multiple collector counter
flow heat exchanger;
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Figure 10 shows a cross section of a special moulding device;
Figure 11 illustrates the fixation of a plates assembly by casting;
Figure 12 illustrates a plate assembly made of one single piece;
Figure 13 illustrates in three sections a heat exchanger body;
Figure 14 gives a cross section of a refrigerant condensor;
Figure 15 gives a cross section of a high pressure heat exchanger;
Figure 16 illustrates the fixation of plate edges by dipping;
Figure 17 illustrates thc fixation of plate edges by spraying.
To build a heat exchanger conforming to the present invention, one can use -
among other things- pressed sheets, repre~enting bumps or dents, ~ystemati-
-cally shaped and located in a suitable pattern, and protruding one or both
sides of the said sheets. Different designs of dents and bumps can be used,
some examples of which are illustrated in the first figures 1, and 2.
When a number of similar, for example rectangular pressod plates PP is assem-
ed with ~ edges in suitable alignment, the successive plates ~ and
supporting each other by the said bumps, one achieves a rectangular assembly
A offering, between the successive plates PP relatively narrow flow~paths S.
With a suitable repartition of the bumps as described above, a fluid can, in
each of the flow paths S between the successive plates PP, circulate and -
spread in all directions.
Obviously one should control the actual fluid flow, by partial stopping of
the peripheric zone Z of the said flow path S (this means : the zone close to
the edges of the plates). In that case, the fluid cannot enter nor leave thç
flow path except in non stopped or closed places.
For example, as shown in fig.7, one can stop the periphery of a first flow
ath Sl, except in two distinct places, where subsist in- and outlet orifices
65~5'a~
Il~ l. A circulating fluid nocc80cr61y goes from the entry to the exit,
from Il to 1~ in between the fluid circulates according to lowest resistance,
thus spreading over the available cross section. Doing the same for all of
the odd flow paths Sl of a plates assembly A, the in- and outlet orifices Il
and l being similarly located each time, their orifices are in alignment and
can easily communicate with in- and outlet fluid collecto~s CIl and COl.
Similarly, one can partially stop the peripheric zones of the even flow paths
S2 ~ in- and outlet orifices I2 ant 2 being located in order to communicate
with in- and outlet collectors CI2 and C02, different from but close to the
foregoing ones CIl and COl.
With a relatively long heat exchanger as illustrated in fig.7, counter-
current operation can be achieved when the orifices and collectors are suit-
~BL~
ab~ located on the short sides of the rectangular plates which together make
the assembly. With relatively short exchangers, this would practically re-
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l~9V3Z9
sult in cross flow operation.
However, a counter current flow in relatively short
bumped plate exchangers can be achieved by multiple collectors
as illustrated in Fig. 8, representing some cross-sections,
and Fig~ 9, giving a general view of such a heat exchanger
with multiple collectors. One can see how any odd flow path -
Sl for example has three inlet orifices I2 and three outlet
orifices 2' As herein shown, each of the multiple collectors
define a prismatic polyhedral volume with the opposite faces -
having alternating triangular faces perpendicular to the
plates P. In Fig. 9 the outlet orifices 2 and CO2 cannot
be seen. All of these orifices are located on two opposite
faces of the plates assembly A, which constitutes the heat -
exchanger. Moreover, the said orifices are arranged in such
a way that the connected collectors are close together, and
alternating. This means that for example each CIl collector
is next to or between CO2 collectors and vice versa~ The ~-
cross-section (b) in Fig. 8, shows how for example one common
zig-zag shaped partition bounds both the inlet collectors CI
open to the left and the outlet collectors open to the right
side. Obviously with this arrangement it is easy to arrange
a general collector, for primary inlet CCIl connected with
the three primary inlet collectors CIl, and a general secondary
outlet collector CCO2 in connection with the aforesaid outlet
collectors CO2.
This arrangement gives fair counter-current opera-
tion if the width of the collectors CIl, CO2, is relatively
; small as compared to the length of the flow path through the
~ heat exchanging assembly.
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1090;~'~9
:
Fig. 9 gives a general view of a plate heat
exchanger with multiple collectors for counter-current
operation In this case a constructive variation on the
former example, using a zig-zag shaped partition between the
collectors, the folds of which are not parallel, allows in a
simple and compact way to canalize the fluids in such a way
that the flow in the main in- and outlets is parallel to
the flow within any of the flow paths of the heat exchanging
assembly A.
; 10 In practice the partial and systematic stopping of
the periphery of the flow paths S in a plates assembly A as
described above, can be achieved in different ways.
For example one can clamp a wire with a suitable
diameter between the successive plates, or fold the edges of
the said plates in the zones to be stopped, and finish the
job by brasing of dipping.
Instead of the wire or the edge folding, one can
clamp two consecutive plates located between two orifices to
-` be connected to a common collector. These procedures are
illustrated in Figs. 4, 5 and 6a.
Figs. 10 and 11 illustrate another solution applic-
able in the zones where inlet and outlet orifices are wanted.
In this case (B) one does the reverse: provisional plugs C
are putthere where orifices I or O are wanted, possibly the
edges of two plates in contact with each other are clamped,
as shown
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in fig.6a. A face of the assembly A, comple~tely prepared with provisional
.9 plugs is put horizontally in an horizontal un~eep mould m (see fig.ll, 6b)
`- where a liquid mass M i8 poured, possibly on a reinforcing grid, the liquid
;`` solidifying by polymerisation or cooling, thus stopping and plugging the pe-
~` ripheric zones of the flow paths, submerged in the solidified mass M. By
- withdrawing the plugs C after unmoulding the necessary in- and outlet orifi-
ces come free. Obviously the same operation of preparation and moulding is
repeated for any of the four faces formed by the edges of the bumped plates
which constitute the heat exchanger.
Fig.10 illustrates an improved procedure. In this case the plugs CC have
flexible walls, and can be inflated during the moulding operation, and thus
be kept right in place. By deflating or by applying a vacuum, they can be
removed easily during unmoulding, after the mass M is solidified.
~",Lo6o
Furthermore, one single flexible piece for example in ~ww~e rubber constitu-
tes the mould m, and incorporates any. of the necessary plugs CC. These are
; in communication with a common pressure tap Px, by means of a small integra-
. ted duct K.
,f-' These improvements allow to accelerate the preparation, moulding and unmoul-
ding operations; together higher precision results.
The joining of consecutive plates in a zone where inlet or outlet orifices
, ,
are wanted can also be done by dipping at a limited depth, the plate edges
being shaped by pressing in order to touch each other -(as shown in fig.l6).
If the dipping fluid (M) has suitable viscosity and surface tension, the pla-
tes in contact with each other will be bound. Where there is a fair gap be-
. .,
tween the plate edges, the orifices will stay free and open.Another procedure involves spraying of a solidifying mass (M), possibly in
different layers, the spraying gun being held in a plane perpendicular to the
plates, at angles close to a right angle, as shown in fig.17, once from right
?:; to left, once in the opposite sence. It is easy to see how depending on the
spraying angle and the gap between plate couples only a narrow strip on each
of the plates will be covered.
Gravity forces make the films of depo~ited liquid (with suitable viscosity
and surface tension) to 30in.
....
In fact, by dipping or spraying as explained or by a combination of both, a
V-shaped binding strip (U) is formed along the plates edges, as shown in
fig.l6.17. This will not be sub~ect to "peeling" but rather to shear and
traction forces when pressure differences are applied to a finished heat ex-
changer.
- Moreover, the spraying procedure allows the use of two component binding
agents with a li~ited "pot life", with minimum material wastes.
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In some application heat exchangers have to support important fluid pressure
differences under severe tightness conditions. In such cases the aforesaid
manufacture procedures might fail. In some cases welding is necessary. For
good rigidity and resistance a particular bumping can be used which involves
that each point of the originally flat plate is stretched, and after pressing,
no straight or flat places subsist.
To limit the total length of welded ~oints oa the heat exchanger~ one can .
make the plates PP, or P of the exchanger as a single seamless piece, from a
- long continuous suitably bumped strip of sheet material, folded ln zigzag as
shown in fig.12.
Each layer constitutes a plate P (or PP), two consecutive plates make a
pocketlike flow path Sl, which is closed on the lower folding line.
Using an even number of folds or plates with uniform width, one obtains a
number of identical flow paths Sl, which all are closed on one side (downside
in fig.l2) and open on the opposite side (up~ide), and which together make a
rectangular bumped plates assembly as described above (compare fig.3).
- With suitable bumping as explained with foregoing figures 1 and 2, and folding
up to the point where the consecutive folds touch each other by means of the
~ bumps as explained with the foregoing figures 4, 5 or 6, obviously an assem-
20 bly of parallel plates results at uniform difitances, between which~fluids can
circulate and spread in principle in any direction.
This sssembly, obtained by suitable bumping and folding, can be comp~ted as
illustrated in fig.l3 by a flat cover plate Py on the assembly's face y where
~ originally the flow paths are open, the cover Py having inlet and outlet ori-
f~''!' fices CIl and COl located at the extremities and sized in order to communicate
`~ with any of the pocket like flow paths Sl. The edge of the said cover Py is
weldet to the outer edges of the zigzag assembly. Moreover each couple of
plates making a flow path Sl is welded and tightened at the extremities. The
f latter ~oints can be made with cast metal somewhat according to fig.ll, in-
30 stead of welding.
~i In the way described with a relatively limited length of welded ~oints one
realises a hollow, tight and compact body X with a great outer surface.
~ Through the orifices CIl and C01 a primary fluid can circulate inside. This
; body resists well to external preAsure, since the bumped plates support each
other. For higher rigidity one can for example decrease the distance between
successive bumps.
A secondary fluid can in principle circulate in any direction through the
flow paths S2 subsisting between two successive pocket like paths Sl. This
secondary fluid can be guided by an envelope E fitting around the rectangular
40 hollow body X ~ust described, with suitable inlet and outlet orifices CI~ and
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C02. As shown in the cross section, fig.14 an elongsted cylindrical envelope
E can be used for better resistance to high static pressure in the secondary
fluid This kind of heat exchnager performs very well as a refrigerant con-
densor, the refrigerant condensing in the cylindrical shell or envelope E,
the cooling water circulating through the body X mounted inside the shell E.
As can be seen in fig.l4, the collectors CIl and C01 of the sald body X are
mounted through the shell E which has a gas inlet CI2 located upside and a
; condensate outlet C02 downside.
In other cases, for example liquid/liquid heat exchange under high pressure,
: 10 one can use a design as illustrated in fig.l5. In this example a rectangular
hollow body X as desribed above is mounted inside a cylindrical shell E, to-
gether with fillings R in the voids between E and X, in order to force the se-
condary fluid to circulate in the flow paths S2 of the body X.
The fields of applicstion for heat exchangers with bumped plates or folds,
conforming to the present invention, sre numerou6 and diverse. Some examples
have been suggested and illustrated in figures 14 and 15. Another application
involves heat exchangers between low pressure gases in general, and more par-
ticularly heat recovery in ventilation and air conditioning systems. In the ~ -
latter case, the aim iB to exchange heat - or cold - between exhaust air and
; 20 fresh air. Evaporative cooling in non saturated ambient air can be related
to the aforesaid heat recovery.
For heat recovery in ventilation plan~s the exhaust air (primary fluid) and
the fresh air (secondary fluid) circulate in counter-current through a bumped
plates heat exchanger confonming to the preaent invention with a suitable
-~ rectangular envelope to resist to the static pressures involved, which in ge-
neral are very moderate.
Evaporative cooling can be achieved with a quite similar heat exchanger : am-
bient air to be cooled circulates as a primary fluid, preferably in counter-
current to a secondary ambient air flow which has been, upstream the heat ex-
- 30 changer, adiabatically saturated with liquid water, thus cooling down from
- the dry to the wet bulb temperature. The performance can be increased by in-
~ection of an e~cess of water in the secondary air. This liquid e*e~ss is
carried with the air which thus can be resaturated along the flow paths in the
heat exchanger and reach the outlet nearly saturated, this means with a maxi-
mum enthalpy for the temperature involved. Premature segregation by gravita-
tion can be avoided by suitable arrangements. For example, the heat exchanger
can be mounted for vertical flow, the secondary air coming down. This arran-
gement maintains a good contact between air and water in the flow paths S2 ;
at the outlet excess water can be separated and recirculated.
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Another solution i8 to have the heat exhanging surfaces in horizontal posi-
tion. In this case excess water can be carried as a fog, or flow on the ho-
rizontal surfaces, driven by the flowing air.
A new and very interesting application in air conditionning and ventilation
plants is the combination in one single heat exchanger of heat recovery and
evaporative cooling as explained above. Fresh outside air - which i8 warm in
summer - clrculates in counter-current with adiabatically sursaturated ex-
haust air. In a well balanced plant the exhaust air is normally far from sa-
turstion, and often lower in temperature than outside. Thus heat recovery
with sursaturation cooling can be very efflcient. Obviously in winter condi-
tions, the exhaust air should not be humidified for heat recovery. The change-
over from one to another condition can be automatic.
Bumped plate heat exchangers conforming to the present invention have typical
advantages.
As to thermal performance, a suitable bumping design can support the turbu-
lence in the fluid flow resulting in high heat transfer coefficients, thus re-
rh 6A ~J )J ~ c
-.~etively reduced exchanging srufaces and outside dimensions. In the mnan t~e
the associated pressure drops are relatively small as only pr~mary surfaces
are involved, without spacers. On the other hand the inlet and ou~let collec-
tors are arranged in a simple way and give insignificant local pressure drops.
From a mechanical point of view the resistance and rigidity are inherently
high, even with thin and poor quality sheet material, due to the multiple con-
tact points between succe~sive plates. In some cases one can for example use
plet-~o fllms or impregnated paper.
In connectlon with the inherent rigidity of the bumped plates heat exchanger
it can be designed and built with very narrow gaps between plates, and thus
with small outside slzes.
As to economlc aspects, lt can be noticed that the manufacture is simple and
cheap, even if a wide range of different units is produced, and thus a flexi-
ble sales programme is claimed.
Wlth relatively low first cost, one can expect important savings on running
costs, for example ln the case of heat recovery in A.C. plants. Even it is
qulte possible that the lnvestment for a heat exchanger for heat recovery ls
balanced by the investments savlngs for heat and cold generators to feed the
A.C. pl-nt.
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