Note: Descriptions are shown in the official language in which they were submitted.
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Title:IMPROVED HEAT TRANSFER APPARATUS
This invention relates to plates for heat transfer
apparatus, such as heat exchangers or evaporators.
In such heat transfer apparatus heat is transferred
between two thin. broad streams, which may be both of
liguid or one stream of liquid and one stream of vapour
or two streams of vapour, or in some cases one or both
streams may have mixed liquid and vapour phases. The
streams are separated by plates assembled in a spaced
face to face relationship to provide flow spaces between
the adjacent faces of the plate. The boundaries of the
flow spaces are enclosed and sealed by flexible or
resilient gaskets surrounding the flow spaces between
the flow spaces and entry and exit ports. The ports, in
plate heat exchangers usually one at each corner of the
plate, are similarly surrounded or part-surrounded by
gaskets.
A substantially similar construction to that used in
plate heat exchangers has also been employed in
tissue-culture vessels, which makes advantageous use of
the large surface area afforded by such a construction.
In such vessels the gasketing contains a possibly
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pathogenic organism and in some embodiments i6 subjected
to the thermal shock associated with steam cleaning, it
is therefore of the utmost importance that the gaskets
sealing ability is not compromised.
Each gasket is normally of a one piece construction set
within a pressed groove formsd in the plate.
The manufacture of the gaske~ is normally carried out in
moulds, but according to the size of the plate or the
manufacturing technigues used the gasket may be
assembled from two or more smaller components. The
gaskets are normally moulded of an elastomeric material.
The sealing force against the fluid pressure in the flow
space is obtained by compression of the gaskets in a
direction normal to the plate surface and the resistance
to gasket extrusion from the proper sealing position in
the groove is normally enhanced by securing the gasket
to ths plate surface by the application of a system of
adhesion, which is necessary in certain applications in
order to minimise gasket movement which would result in
leakage. Such movements can arise because changes in the
loading condition of one gasket will alter the condition
of the gasket on either side, and, perhaps of greater
importance, the gaskets are assembled into the groove
which is formed from this sheet material and which is
therefore flexible. This system of adhesion is
frequently complex and time consuming, involving the
application of an adhesive to both the gasket and the
plate surface. and assembly of the two components
together. According to the system which is adopted it
may be necessary to prepare the mating surface of either
component before assembly and it may be necessary to
subject the assembled components to a process designed
for curing the bond after assembly.
The foregoing description covers the initial
manufacturing process. It is common practice that as the
elastomeric gasket material hardens and deforms in use
with the passage of time, the servicing of the plate
head exchanger at the user's factory requires the
replacement of the gasket. Removal of the old gasket
requires destruction of the adhesive bond and cleaning
of the groove. Also, it is not always possible to
subject the newly assembled gasket to the optimum
process of adhesion such as would be applied during
initial manufacture by the supplier.
It is an object of the invention to provide mechanical
engagement of the gasket with the plate so as to avoid
the necessity for a system of adhesion.
It is well understood in industrial practice to form a
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seal groove in the face of one component, which groove
has an opening smaller in dimension than the resilient
gasket which has to be inserted through the opening. The
gasket is thus releasably secured by its own resilience.
Such a groove is di~ficult to form in a pressed plate in
that it would not be readily produced in a one-hit
pressing operation.
It is a known practice in the manufacture of plate heat
exchange~s to attach a resilient gasket to an aperture
in a substrate material by pushing somewhat oversize
projections through apertures located in the floor of
the groove.
It has also been suggested, that the gasket should be
secured to a surface by fixing means such as a mask, or
such as tabs which are attached to or integral with the
gasket and are secured to the surface outside of the
sealing area. The latter method is illustrated in the
German Patent No. 832 975.
A further known gasket, as bes~ illustrated in the U.S.
Patent No. 4377204 teaches that the ~ab s~lould lie in a
trough, and be attached by the known oversi2e projection
method related above.
According to a first aspect of the present invention
there is provided a heat transfer plate at least
partially bounded by a groove for receiving a gasket for
genaral conformity therewith and to seal against an
adjacent plate, wherein;
a) said groove comprises an inner side wall and an
outer side wall,
b) the outer side wall of the groove is provided with a
number of lateral bays, the gasket being formed with a
number of corresponding spaced projections engaging in
and matching with said bays,
c) the base of each bay is at a level other than the
base of the outer side wall of the groove, and,
d) each bay does not communicate with the ambient
thereby limiting movement of the gasket material along
each said bay.
According to a second aspect of the invention, there is
provided a gasket for use with a heat transfer plate at
least partially bounded by a groove, the gasket being
formed of a compressible material and having a number of
spaced projections to correspond with a number of bays
provided in an outer side wall of the gasket groove, the
spaced projections engaging in and matching with the
said bay~ on installation of the gasket in the groove,
wherein each said projection is less thick in a
direction normal to the plane of the said plate than the
body of the gasket
Conveniently, at least one of the said bays is provided
with means for securing the corresponding matching
projection of the gasket thereto.
In an embodiment, the means for securing the
corresponding matching projection of the gasket comprise
an aperture in the plate which co-operates with a stud
provided on the gasket.
In a further embodimnt the gasket is provided with a
peaked upper surface to engage and seal on an adjacent
plate.
The invention also extends to combinations of the
gaskets and heat transfer plates as disclosed herein.
The invention will be further described with reference
to the accompanying drawings in which:-
Figure 1 is a plan view of a known heat transfer plate:
Figure 2 is a section on the line X-X of Figure l;
Figure 3 is an elevational view of one form of gasket
groove according to the present lnvention,
Figure 4 is an enlarged section on the line Y-Y of
Figure ~, with the gasket added;
Figure 5 is an elevation of ano~her form of gasket
according to the present invention;
Figure 6 is an enlarged section on the line Z-Z of
Figure 5, and
Figure 7 is a view similar to Figure 4 showing a further
modification.
Figure l shows an outline of a conventional heat
exchanger plate in which the plate l has the usual and
exit ports 2 and the central heat transfer area 3
surrounded by a resilient gasket 4. As shown in Figure
2. which is a section XX through the gasket (shown
dashed), the gasket 4 is mounted in a pressed groove 5
and attached to the plate by means of an oversize
projection 6. which protrudes through a hole ll, at a
fixing point located in a trough 7.
One problem with this arrangement is that the
considerable overpressures which occur in the flow
spaces of a heat exchanger extrude the gasket 4 along
the trough 7, and cause the sealing to fail at these
fixing eoints.
In another well known form of plate design the gasket
groove 19, as shown in Figure 3, is provided with
lateral enlargements in the vertical wall 20 as shown at
11. By this means the width of the gasket groove is
locally enlarged. It is proposed that between some or
all of these enlargements the groove edge 20 should be
formed as indication by the numeral 21 and as shown in
Figure 4, to provide la~eral bays 21 in the gasket
groove.
In a preferred orm of the invention the latecal bays 21
are provided with apertures 25 and protuberances 10 are
provided on the gasket, being manufactured to such
dimensions that the protruberances will be slightly
compressed when entering the apertures so that the
gasket ~ and plate 3 will remain assembled, but can be
dis-assembled by pulling the gasket away from the plate.
It should be noticed that the wider portions of the
gasket groove are normally positioned to alternate one
with another from plate to plate, and thus in this
embodiment the protuberances 10 remain unaffected by
compression when the plate pack is tightened to operable
conditions, because the apertures 25 and protruberances
10 are well removed to one side of the sealing surface
of the gaskets.
It should be understood that the apertures 25 are not
restricted in their placement to the base of the bay 21
but may be located in the rear wall 27 of the said bay
or where the bay has side walls, they may be located in
such side walls.
In an alternative form of the invention shown in figures
5 and 6, the bay 30 is not located between two
enlargements, but provided in the flat outer wall 31 of
a gasket groove 3Z, having a floor 34. An aperture 33 is
provided in the base of the bay thereby enabling the
gasket to be secured to the heat t-ransfer plate.
Furthermore, in this embodiment the bay 30 is
rectilinear rather than curvilinear as in the embodiment
of figure 3.
In figure 7 an embodiment is illustrated in which the
base 40 of the bay 41 is below the base of the groove
42, and the gasket 43 is so profiled as to enable the
plates to be sealingly mated against one another.
The embodiments of the invention illustrated in the
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accompanying drawings and described herein have a common
feature that the gasket sealingly engages the rear wall
generally indicated by the numeral 27. This engagement
limits extrusion of the gasket material along the bay of
the groove and thereby prevents "blowing-out" of the
gasket at these points. Furthermore the floor of the
bay. (for example indicated as 40 in figure 7 and as 33
in figure 5) is always at a level other than the floor
of the groove ~indicated by 42 in figure 7 and 34 in
figure 6). This difference in level aids engagemen~
between the gasket and the heat-transfer plate.
Various modifications may be made within the scope of
the invention, for example, the gasket may be formed
with recesses in the exposed face adapted to seal
against the adjacent plate to receive the ends of the
projections from the gasket in the groove in that
adjacent plate.
