Note: Descriptions are shown in the official language in which they were submitted.
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A PORTHOLE GASKET FOR A PLATE HEAT EXCHANGER, A PLATE
PACKAGE AND A PLATE HEAT EXCHANGER WITH SUCH A PORTHOLE GASKET
Technical Field
The present invention generally relates to plate heat exchangers, and in
particular
to a porthole gasket for installation between two adjacent heat exchanger
plates of a
plate heat exchanger.
Background
Plate heat exchangers, PHEs, typically consist of two end plates in between
which a heat exchanger plate package is arranged. The plate package typically
includes
a plurality of heat exchanger plates stacked on each other to define first and
second
spaces for first and second fluids, where each heat exchanger plate includes
portholes
that permit fluid communication with the first and second spaces. In one type
of well-
known PH Es, the so called gasketed PH Es, field and porthole gaskets are
arranged
between the heat exchanger plates. The field gaskets are typically arranged in
field
gasket grooves which run along outer edges of the heat exchanger plates while
the
porthole gaskets typically are arranged in porthole gasket grooves which run
along inner
edges, more particularly around the portholes, of the heat exchanger plates.
The end
plates, and therefore the heat exchanger plates, are pressed towards each
other
whereby the gaskets seal between the heat exchanger plates. In another type of
well-
known PH Es, the so-called semi-welded plate heat exchangers, the plate
package is
formed by plate modules, which each comprises two heat exchanger plates welded
to
each other to define one of the first spaces, the field and porthole gaskets
thus being
replaced by welds, and the plate modules are stacked, with intermediate field
and
porthole gaskets arranged in field and ring gasket grooves, respectively, to
define the
second spaces between them. The semi-welded heat exchangers are frequently
used in
applications where the first fluid is aggressive or under a significantly
elevated pressure,
and the second fluid is relatively non-aggressive. The porthole gaskets will
be subjected
to the first fluid and may have to be manufactured of a high quality material.
However,
since the porthole gaskets contain a relatively small material volume, this
should not
have to involve any major increase in costs.
For a plate heat exchanger to be leak proof, it may be important that the
gaskets
are properly positioned in the gasket grooves. The gasket grooves are
typically defined
by an outer lateral wall, an inner lateral wall and a bottom wall extending
there between.
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The outer and inner lateral walls typically result from pressing of the heat
exchanger
plates during which operation the plates are provided with a pattern of
valleys and ridges.
In conventional plate heat exchangers the outer lateral walls of the porthole
gasket
grooves are intermittent so as to provide, to the porthole gaskets, only
periodical support,
i.e. support in separated support areas. Thus, there is a risk of the porthole
gaskets
being displaced, between the support areas, from their proper positioning in
the porthole
gasket grooves, especially when a pressure prevailing within the porthole
gaskets, i.e.
inside the portholes, is considerably higher than a pressure prevailing
outside the
porthole gaskets.
As a solution to this problem, W02004/072570 proposes to re-design the heat
exchanger plates so as to make the outer lateral walls of the porthole gasket
grooves
continuous and thereby capable of providing uninterrupted porthole gasket
support.
However, there is a need for alternative solutions.
Summary
It is an objective of the invention to at least partly overcome one or more
limitations of the prior art. Another objective is to reduce the risk for
fluid leakage in plate
heat exchangers with overlapping portholes sealed by porthole gaskets. A still
further
objective is to reduce the risk for fluid leakage in plate heat exchangers
sealed by
porthole gaskets located in dedicated ring-shaped gasket grooves with
intermittent
openings along their outer lateral walls. One or more of these objectives, as
well as
further objectives that may appear from the description below, are at least
partly
achieved by means of a porthole gasket, a plate package for a plate heat
exchanger and
a plate heat exchanger according to the independent claims, embodiments
thereof being
defined by the dependent claims.
A first aspect of the invention is a porthole gasket for installation between
two
adjacent heat exchanger plates of a plate heat exchanger, the porthole gasket
being
configured to seal a circumferential region around two overlapping portholes,
each of
which being formed in a respective one of the two adjacent heat exchanger
plates, so as
to define a passage for a fluid into or out of the plate heat exchanger. The
porthole
gasket comprises a ring-shaped portion configured to be compressed between the
two
adjacent heat exchanger plates while surrounding the overlapping portholes.
The
porthole gasket further comprises a plurality of projections that protrude
from an outer
perimeter of the ring-shaped portion and are configured to be compressed
between the
two adjacent heat exchanger plates so as to support the ring-shaped portion
against
pressure exerted by the fluid.
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Compared to a conventional porthole gasket, which has a smooth continuous
outer perimeter, the projections will serve to increase the total contact area
of the
porthole gasket and thus the friction between the porthole gasket and the two
adjacent
heat exchanger plates when the porthole gasket is compressed between the heat
exchanger plates. Thereby, the porthole gasket is more firmly held in place
around the
two overlapping portholes, reducing the risk for fluid leakage across the
circumferential
region that is sealed by the porthole gasket.
The increased contact area and friction allows the porthole gasket to be
firmly
held in place if installed, for example, in a ring-shaped gasket groove that
has openings
in its outer lateral wall. For installation in such a gasket groove, the
porthole gasket is
suitably configured such that its ring-shaped portion mates with the gasket
groove, while
its projections mate with and extend through at least a subset of the openings
in the
outer lateral wall of the gasket groove. These openings may have any
distribution along
the outer lateral wall.
However, the inventive porthole gasket may be installed between any types of
adjacent heat exchanger plates, which may or may not be provided with gasket
grooves
for receiving the porthole gasket. In certain applications, and depending on
the design of
the porthole gasket and its projections, the porthole gasket may have a
sufficient ability
to seal the circumferential region around the overlapping portholes and
withstand the
pressure exerted by the fluid inside the portholes, even if installed and
compressed
between essentially flat surfaces on the two adjacent heat exchanger plates.
It is to be understood that "ring-shaped" does not imply a circular shape, but
merely indicates that the ring-shaped portion is configured to surround the
overlapping
portholes in the circumferential region. Thus, the ring-shaped portion of the
porthole
gasket may be either circular or non-circular, including regular shapes, such
as oval,
rectangular, triangular or hexagonal shapes, and irregular shapes.
In one embodiment, at least one of the projections comprises a friction-
enhancing
surface pattern that defines a patterned first surface portion for engaging a
first one of
the two adjacent heat exchanger plates when the projections are compressed
between
the two adjacent heat exchanger plates. The provision of such a surface
pattern has
been found to significantly improve the ability of the porthole gasket to
withstand
pressure, by further increasing the friction between the porthole gasket and
the two
adjacent heat exchanger plates.
The sealing ability and stability of the porthole gasket may be further
improved by
optimizing the design of the surface pattern, for example according to one or
more of the
following embodiments.
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In one embodiment, the surface pattern defines a patterned second surface
portion for engaging a second one of the two adjacent heat exchanger plates
when the
projections are compressed between the two adjacent heat exchanger plates, the
first
and second surface portions being arranged on opposite sides of said at least
one of the
projections.
In one embodiment, the surface pattern comprises a plurality of spaced-apart
pattern structures, as seen parallel to a normal direction of the patterned
first surface
portion. It may further be advantageous for the pattern structures to be
separated by a
gap distance, as seen parallel to the normal direction of the patterned first
surface
portion, the gap distance being at least half of a smallest dimension of the
pattern
structures, as seen parallel to the normal direction of the patterned first
surface portion.
Furthermore, at least a subset of the pattern structures may have rounded
ends, as seen
parallel to the normal direction of the patterned first surface portion, said
rounded ends
having a radius which is approximately equal to half of the smallest dimension
of the
respective pattern structure, as seen parallel to the normal direction of the
patterned first
surface portion.
In one embodiment, the pattern structures comprise protrusions protruding,
parallel to the normal direction of the patterned first surface portion, from
a bulk portion of
said at least one of the projections, to define the patterned first surface
portion. Each of
the protrusions may have an extent, from the bulk portion and parallel to the
normal
direction, which is approximately 2.5-5%, or even 2-10%, of a thickness of the
bulk
portion parallel to the normal direction.
In one embodiment, the pattern structures comprise elongated ribs.
In one embodiment, said at least one of the projections is elongated and
extend
in a longitudinal direction away from the outer perimeter of the ring-shaped
portion, and
at least part of the pattern structures extend essentially transverse to the
longitudinal
direction.
Alternatively or additionally, the sealing ability and stability of the
porthole gasket
may be further improved by optimizing the design of the projections, for
example
according to one or more of the following embodiments.
One or more of the projections may be connected to the ring-shaped portion by
a
link portion, which has a smaller material thickness than said one or more of
the
projections.
In one embodiment, at least a subset of the projections are elongated and
extend
in a longitudinal direction away from the outer perimeter of the ring-shaped
portion. It
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may further be advantageous for the longitudinal direction to be non-
perpendicular to the
outer perimeter of the ring-shaped portion, for at least one of the
projections.
The projections may be uniformly distributed around at least a major part of
the
outer perimeter of the ring-shaped portion.
The ring-shaped portion may extend in a geometric plane, and the projections
may extend from the ring-shaped portion parallel to the geometric plane. The
ring-
shaped portion and the projections may extend in the same geometric plane.
To facilitate installation of the porthole gasket between the two adjacent
heat
exchanger plates, the porthole gasket may further comprise an attachment
member
which protrudes from an inner perimeter of the ring-shaped portion and is
arranged to
engage with an edge portion of one of the overlapping portholes.
In a further embodiment, the porthole gasket comprises a label member which
protrudes from the outer perimeter of the ring-shaped portion and is arranged
to extend
beyond the two adjacent heat exchanger plates so as to be visible externally
of the plate
heat exchanger.
A second aspect of the invention is a plate heat exchanger comprising a
porthole
gasket of the first aspect.
A third aspect of the invention is a plate package for a plate heat exchanger,
comprising two adjacent heat exchanger plates and the porthole gasket of the
first
aspect compressed between the two adjacent heat exchanger plates, each of the
two
adjacent heat exchanger plates being formed with a porthole, the portholes of
the two
adjacent heat exchanger plates being overlapping, and the porthole gasket
surrounding
the portholes.
In one embodiment, each of the projections is compressed between a respective
pair of opposite engagement surfaces on the two adjacent heat exchanger
plates, and
wherein each of the projections has a thickness, before compression, which
exceeds a
distance between the respective pair of opposite engagement surfaces after
compression by approximately 10-20%, or even 5-20%.
In one embodiment, the ring-shaped portion is located in a ring groove formed
in
at least one of the two adjacent heat exchanger plates, and at least a subset
of the
projections are located in channels that are defined by the two adjacent heat
exchanger
plates to extend away from the ring groove. The respective channel may be
formed by
single channel groove in one of the heat exchanger plates, or by two mutually
aligned
channel grooves as defined further below. To further improve the stability of
the porthole
gasket, one or more of the projections may be fitted in a respective one of
the channels
that has a non-linear extent away from the ring groove, and each of said one
or more of
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the projections may have an extent that conforms to the non-linear extent of
the
respective one of the channels. Alternatively or additionally, the ring-shaped
portion may
be compressed between bottom surfaces of a first ring groove formed in a first
one of the
two adjacent heat exchanger plates and a second ring groove formed in a second
one of
the two adjacent heat exchanger plates, the first and second ring grooves
being
arranged in mutual alignment, and said at least a subset of the projections
may be
compressed between bottom surfaces of channel grooves, which are formed in the
two
adjacent heat exchanger plates and arranged in mutual alignment to define said
channels.
At least one of the two adjacent heat exchanger plates may be formed to extend
in at least an intermediate plane, an upper plane and a lower plane, said
planes being
substantially parallel to each other, wherein the ring-shaped portion may
engage said at
least one of the two adjacent heat exchanger plates in the intermediate plane,
and
wherein the projections may engage said at least one of the two adjacent heat
exchanger plates in the lower plane. The intermediate plane and the lower
plane may
coincide.
Any one of the embodiments of the first aspect can be combined with the second
to third aspects to attain the corresponding technical effects or advantages.
Still other objectives, features, aspects and advantages of the present
invention
will appear from the following detailed description, from the attached claims
as well as
from the drawings.
Brief Description of Drawings
Embodiments of the invention will now be described in more detail with
reference
to the accompanying schematic drawings.
Fig. 1 is a side view of a plate heat exchanger with a plate package.
Fig. 2 is a schematic plan view of a heat exchanger plate for the plate
package in
Fig. 1.
Fig. 3 is a schematic plan view of the heat exchanger plate in Fig. 2 welded
to
another heat exchanger plate.
Fig. 4 is a schematic plan view of the heat exchanger plate in Fig. 2 welded
to
another heat exchanger plate and provided with gasket members.
Fig. 5 is an enlarged plan view of area I of the heat exchanger plate in Fig.
2.
Fig. 6A is a section view taken along line II-II in Fig. 5, Fig. 6B is a
corresponding
section view with a porthole gasket placed on the heat exchanger plate, and
Fig. 60 is a
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section view of two assembled heat exchanger plates with a porthole gasket
between
them.
Fig. 7 is a plan view corresponding to Fig. 5 in which a porthole gasket
according
to one embodiment is installed to surround a porthole in the heat exchanger
plate.
Fig. 8 is a perspective view corresponding to Fig. 7.
Fig. 9 is an enlargement of a portion of the heat exchanger plate and the
porthole
gasket in Fig. 8.
Fig. 10 is a plan view of a porthole gasket according to another embodiment.
Fig. 11 is a perspective view of a portion of the porthole gasket in Fig 10.
Fig. 12 is a section view taken along line III-Ill in Fig. 10.
Fig. 13 is a section view taken along line IV-IV in Fig. 10.
Fig. 14 is a plan view of area V in Fig. 10.
Fig. 15 is a plan view of a portion of a ring gasket according to yet another
embodiment.
Detailed Description of Example Embodiments
Fig. 1 illustrates a plate heat exchanger 100 including a plate package 1 with
a
number of plate modules 2, which each includes a number of heat exchanger
plates 3
arranged adjacent to each other. In the embodiments disclosed herein, each
such plate
__ module 2 includes two heat exchanger plates 3, but the plate modules 2 may
be formed
by combining a group of more than two heat exchanger plates 3.
The plate package 1 is arranged between two end plates 4, 5. The end plates 4,
5
are pressed against the plate package 1 and each other by means of tightening
bolts 6
extending through the end plates 4, 5. The tightening bolts 6 include threads
and the
__ stack of plate modules 2 may thus be compressed by threading nuts 7 onto
the
tightening bolts 6 in a manner known per se. In the embodiments disclosed
herein, four
tightening bolts 6 are implied (of which only two are visible in the figures).
It is to be
noted that the number of tightening bolts 6 may vary and be different in
different
applications. The plate heat exchanger 100 also includes two inlet members 8
(only one
__ shown) and two outlet members 9 (only one shown). The inlet and outlet
members 8, 9
may be attached to one of the end plates 4, 5 in alignment with respective
inlet and outlet
ports (not shown) in the end plates 4, 5. These inlet and outlet ports are in
turn aligned
with inlet and outlet channels that are formed by mutually aligned portholes
of the heat
exchanger plates 3, as will be described in more detail below.
Each heat exchanger plate 3 has a primary side 3 and a secondary side 3" (Fig.
6A) and is formed to extend in at least three planes, which are substantially
parallel to
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each other: an intermediate plane al, an upper plane a2 and a lower plane a3.
The
intermediate plane al may, but need not, be located centrally between the
upper plane
a2 and the lower plane a3.
In the embodiments disclosed herein, the heat exchanger plates 3 in each plate
module 2 are so arranged that their secondary sides 3" face each other and
define an
inner first space. Further, each pair of two adjacent ones of the plate
modules 2 defines a
second space. Thus, the second spaces are defined by the primary sides 3' of
two
adjacent ones of the heat exchanger plates 3, which adjacent heat exchanger
plates are
comprised in different, but adjacent, plate modules 2. The heat exchanger
plates 3 in
each plate module 2 are preferably permanently connected to each other, e.g.
by means
of welding, brazing or gluing.
Fig. 2 shows an example of a heat exchanger plate 3 as seen towards its
secondary side 3, and Fig. 3 shows a plate module 2 which is created by
combining two
of the heat exchanger plates 3 in Fig. 2. When combining the two heat
exchanger plates
3 into the plate module 2, one of the heat exchanger plates 3 is turned upside
down with
respect to the other heat exchanger plate 3. Therefore, in the plate package 1
of stacked
plate modules 2, every second one of the heat exchanger plates 3 will be
turned upside
down with respect to a reference orientation of the heat transfer plates.
As seen in Fig. 2, each heat exchanger plate 3 includes first portholes 13
which
are arranged to permit fluid communication with the first space. Each plate 3
also
includes second portholes 15 which are arranged to permit fluid communication
with the
second space. When the plate modules 2 are assembled into the plate package 1,
the
portholes 13 are aligned to define an inlet channel and an outlet channel in
fluid
communication with the first spaces, and the portholes 15 are aligned to
define an inlet
channel and an outlet channel in fluid communication with the second spaces.
As noted
above, when the plate package 1 is installed as part of a heat exchanger 100,
the inlet
channels are in fluid communication with a respective inlet member 8, and the
outlet
channels are in fluid communication with a respective outlet member 9.
A first fluid may thus be introduced via one of the inlet members 8 and the
inlet
channel defined by the first portholes 13, flow through the first spaces and
leave through
the outlet channel defined by the first portholes 13 and one of the outlet
members 9. A
second fluid may be introduced via the other inlet member 8 and the inlet
channel
defined by the second portholes 15, flow through the second spaces and leave
through
the outlet channel defined by the second portholes 15 and the other outlet
member 9.
Each heat exchanger plate 3 is preferably manufactured of a metal sheet, for
instance stainless steel, aluminum or titanium, and includes a substantially
central heat
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exchanging surface 20, see Figs 2-4. The heat exchanging surface 20, just like
other
portions of the heat exchanger plates 3, may in a manner known per se be
provided with
a corrugation of ridges and valleys (not disclosed) obtained through forming
of the metal
sheet. In a variant, one or more of the heat exchanging surfaces 20 may lack
the
corrugation and thus be completely planar.
Figs 3-4 disclose a plate module 2 in which the plates 3 are connected to each
other by means of a weld joint 21 (illustrated by a dashed line) extending
around the heat
exchanging surface 20 and the first portholes 13. Weld joints 21 (illustrated
by a
respective dashed line) also extend around each of the second portholes 15.
Between the plate modules 2, gasket members are installed and compressed to
seal the second spaces. As shown in Fig. 4, the gasket members include
porthole
gaskets 22 (also denoted "ring gaskets") which are installed in a
circumferential region
around each of the first portholes 13, and a peripheral or field gasket 23
which is
installed to extend around the heat exchanging surface 20 and the second
portholes 15.
Each of the portholes 13, 15 is defined by a port edge 31, as shown for the
first
porthole 13 in Fig. 5. Each of the first portholes 13 is surrounded by a ring
groove 32,
which is arranged to receive the respective porthole gasket 22. The ring
groove 32 is
provided on the primary side 3' at a determined distance from the port edge
31. As
shown in greater detail in Figs 5 and 6A, the ring groove 32 is defined by a
bottom
surface 33, an inner lateral wall 34 and an outer lateral wall 35. As seen in
the section
view of Fig. 6A, the bottom surface 33 is substantially formed at the level of
the
intermediate plane al. The inner lateral wall 34 extends upwardly from the
bottom
surface 33 in a direction towards the port edge 31 and around the bottom
surface 33.
The outer lateral wall 35 extends upwardly from the bottom surface 33 away
from the
port edge 31 and around the bottom surface 33. Both the inner lateral wall 34
and the
outer lateral wall 35 include openings along their respective extension around
the bottom
surface 33 and are thus discontinuous. The openings along the inner lateral
wall 34 on
the primary side 3' are defined by a wave-shaped portion of alternately
arranged ridges
and valleys which are located at the upper and lower planes a2, a3,
respectively. When
the plates 3 have been assembled into a plate package 1, the wave-shaped
portions of
adjacent plates 3 provide support for the port edge 1, by the valleys of one
plate 3
abutting on the ridges of the other plate 3, and vice versa, while allowing
fluid to flow into
or out of the first spaces via the first portholes 13. The openings along the
outer lateral
wall 35 on the primary side 3' are likewise defined by a wave-shaped portion
of
alternately arranged ridges and valleys which are located at the upper and
lower planes
a2, a3, respectively. These valleys define channel grooves 36 that extend from
the
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openings in the outer lateral wall 35 away from the first porthole 13. The
channel grooves
36 are defined by a bottom surface 37, which is located at the level of the
lower plane a3,
and lateral side walls 38, 39 (Fig. 9). As will be described in more detail
below, at least a
subset of the channel grooves 36 are configured to accommodate a respective
projection
22B of the porthole gasket 22 such that the bottom surface 37 engages with the
projection 22B. In this sense, the bottom surface 37 forms an "engagement
surface". The
placement of the channel grooves 36 along the outer lateral wall 35, and their
extent
away from the outer lateral wall 35, may be set to achieve a desired flow path
for the first
fluid from the first porthole 13 inside the first spaces (since the valleys
that form the
channel grooves 36 correspond to ridges on the opposite secondary side 3"). It
is also
conceivable that at least a subset of the channel grooves 36 are provided for
the sole
purpose of accommodating a respective projection 22B, e.g. the channel grooves
36 at
the upper right portion of the ring groove 32 in Fig. 5.
The following description will focus on the configuration of the porthole
gasket 22.
As used herein, a peripheral direction of the porthole gasket 22 extends
around its
perimeter, a radial direction of the porthole gasket 22 extends radially with
respect to its
center point, and an axial direction of the porthole gasket 22 extends
perpendicular to its
peripheral and radial directions.
Generally, the porthole gasket 22 is an integral component made of a flexible
material, such as rubber or a rubber composition.
Figs 7-8 illustrate a porthole gasket 22 as mounted on the primary side 3' of
the
heat exchanger plate 3 in Fig. 5, so as to surround the porthole 13. The
porthole gasket
22 is composed of a ring-shaped portion 22A (denoted "ring portion" in the
following) and
a plurality of projections 22B which are distributed with essentially equal
spacing
(uniformly) around the outer perimeter of the ring portion 22A. In the
illustrated example,
the projections 22B are formed as fingers that generally extend away from the
ring
portion 22A in a respective longitudinal direction. The ring portion 22A
extends in a two-
dimensional geometric plane which is parallel to a figure plane of Fig. 7, and
the
projections 22B generally extend away from the ring portion 22A parallel to
this
geometric plane. The ring portion 22A conforms to and is arranged in the ring
groove 32,
and the projections 22B conform to and are arranged in the channel grooves 36.
The
projections 22B are integrally formed with the ring portion 22A.
It is understood that when the plate modules 2 have been assembled into the
plate package 1 (Fig. 1), the porthole gaskets 22 are compressed between the
primary
sides 3' of adjacent plates 3. The ring portion 22A of each porthole gasket 22
is received
within a pair of mutually aligned ring grooves 32 around the respective first
porthole 13 of
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the adjacent plates 3, while a respective projection 22B of the porthole
gasket 22 is
received within a pair of mutually aligned channel grooves 36 of the adjacent
plates 3.
Each pair of mutually aligned channel grooves 36 thus forms a channel 36' for
receiving
one of the projections 22B (cf. Fig. 60).
The projections 22B serve to increase the contact area of the porthole gasket
22
and thereby increase the friction between the porthole gasket 22 and the
adjacent plates
3 when the plate modules 2 are pressed together to compress the porthole
gasket 22. To
achieve the increase in contact area, each projection 22B has a thickness,
before
compression, in the axial direction of the porthole gasket 22, which exceeds
the total
distance between the surfaces of the plates 3 that engage with the projection
22B when
the plates 3 are assembled into the plate package 1. This ensures that the
projections
22B are compressed between the plates 3 in the plate package 1. In the
illustrated
embodiment, as understood from Fig. 6A, this total distance is twice the
distance
between the upper and lower planes a2, a3. It is currently believed that
optimum sealing
and gasket stability is achieved when the ratio between the projection
thickness and the
total distance is in the range from about 1.05 to about 1.2.
In the illustrated example, all projections 22B are elongated to achieve high
friction and ensure that the ring portion 22A is not dislocated in the ring
groove 32 by the
pressure exerted on the ring portion 22A by the first fluid via the first
porthole 13.
As seen in the section view of Fig. 6B, which is taken in Fig. 7 at the
location of
line II-II in Fig. 5, the ring portion 22A has an essentially flat bottom
surface, which
conforms to the shape of the bottom surface 33 of the ring groove 32, and a
roof-shaped
top surface. The roof-shaped top surface may be provided to achieve a desired
deformation and sealing action when the gasket 22 is compressed. However, the
ring
portion 22A may have any other cross-section known in the art.
In the section view of Fig. 60, another heat exchanger plate 3 has been
arranged
and pressed onto the heat exchanger plate 3 shown in Fig. 6B, such that the
porthole
gasket 22 is fitted between the two adjacent plates 3. The ring portion 22A is
thereby
compressed between the plates 3 to essentially fill the space between the two
mutually
facing ring grooves 32, and the projection 22B is likewise compressed to
essentially fill
the space between the two mutually facing channel grooves 36. Thus, the ring
portion
22A is engaged with and compressed between the bottom surfaces 33 of the
opposing
ring grooves 32, and the projections 22B are engaged with and compressed
between the
bottom surfaces 37 of the opposing channel grooves 36, which thus define a
channel 36'
for accommodating the respective projection 22B. By their engagement with the
porthole
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gasket 22, the bottom surfaces 33, 37 form "engagement surfaces". Although not
shown
in Fig. 60, it is to be understood that the plates 3 belong to a respective
plate module 2.
As seen in Figs 6B-6C, the respective projection 22B has first and second
surface
portions 226, 22B" on its opposite sides that face and engage with the bottom
surface
37 of the respective channel groove 36 when the porthole gasket 22 is
compressed
between the plates 3. These first and second surface portions 226, 22B" are
denoted
"main contact surfaces" in the following. As indicated in Fig. 6B, each main
contact
surface 226, 22B" is associated with a normal direction N, which is
perpendicular to the
respective main contact surface 226, 22B. It is understood that the normal
direction N
typically is parallel to the above-mentioned axial direction of the porthole
gasket 22.
Returning to Figs 7-8, it is seen that a portion of the projections 22B extend
non-
perpendicularly from the ring portion 22A, i.e. in a direction that deviates
from the radial
direction of the porthole gasket 22. Such a non-radial extension may be
governed by the
layout of the flow channels on the secondary side 3, as discussed above.
However, it
may also be advantageous to deliberately design the channel grooves 36 to
provide for
such non-radial extension of the projections 22B. The non-radial extension may
provide
for a more secure attachment of the porthole gasket 22 on the plate 3 during
assembly of
the plate package 1. It may also increase the resistance of the porthole
gasket 22 to
radial displacement caused by the pressure exerted by the first fluid via the
first porthole
13. Furthermore, as also seen in Figs 7-8, one or more projections 22B may
have a non-
linear extension, in the above-mentioned two-dimensional geometric plane, to
further
improve the resistance to radial displacement. The non-linear extension may be
implemented as a bend or knee along the extent of the projection 22B.
In the example of Figs 7-8, the porthole gasket 22 is also integrally formed
with a
label member 22D which is arranged to project from the plate package 1 when
assembled. The label member 22D has a connecting portion that extends from the
ring
portion 22A, or one of the projections 22B, to a crossbar portion. It is
understood that the
plates 3 are provided with appropriate channel grooves for accommodating the
connecting portion. The crossbar portion is labeled to designate the type of
porthole
gasket 22 that is installed in the plate package 1. For example, the heat
exchanger may
be provided with different types of porthole gaskets 22 depending on the type
of fluids to
be conveyed through the plate package/heat exchanger.
In the illustrated example, as best shown in Fig. 6B and Fig. 9, a link
portion 220
connects the respective projection 22B to the ring portion 22A. The link
portion 220 has
a thinner (smaller) material thickness than the connected projection 22B, at
least parallel
to the normal direction N of the main contact surfaces 226', 22B", so as to
increase the
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flexibility between the respective projection 22B and the ring portion 22A, in
particular in
the axial direction of the porthole gasket 22. This flexibility may facilitate
mounting of the
porthole gasket 22 on the plate 3, to ensure that the projections 22 are
properly received
and compressed in the channel grooves 36 when the plate package 1 is
assembled.
Alternatively or additionally, the link portion 220 may have a material
thickness in the
peripheral direction of the porthole gasket 22 that is smaller than the
material thickness
of the projection 22B in the transverse direction of the projection 22B (see
e.g. Fig. 14
and 15), to increase flexibility in the peripheral direction of the porthole
gasket 22. How-
ever, if more rigid link portions 22 are desired or required, the material
thickness of the
link portions 22B may be equal to or exceed the material thickness of the
projection 22B.
As seen in Fig. 9 in conjunction with Fig. 6B, the main contact surfaces 226,
22B" of the projections 22B are defined by a surface pattern 40. In the
illustrated
example, the surface pattern 40 is composed of three or four pattern
structures in the
form of ribs 41 that are spaced in the longitudinal direction of the
projection 22B and
have an elongated extent in the transverse direction of the projection 22B.
The ribs 41
are three-dimensional structures that protrude from a bulk portion 22E" of the
projection
22B and thus have a predefined height in the normal direction N. The bulk
portion 22B"'
thus designates the remaining material of the projection 22B after a removal
of the three-
dimensional pattern structures, such as the ribs 41. In the illustrated
implementation, the
ribs 41 have a height of about 0.2 mm, a width in the transverse direction of
about 0.4
mm, a width in the longitudinal direction of about 0.2 mm, and are spaced in
the
longitudinal direction by a gap distance of about 0.2 mm. These dimensions are
merely
given as a non-limiting example.
The provision of a surface pattern 40 on the main contact surfaces 226, 22B"
has
been generally found to increase the friction between the projections 22B and
the plates
3 (viz, the bottom surfaces 37) and thereby enhance the ability of the
porthole gasket 22
to withstand fluid pressure. The surface pattern 40 may also reduce the impact
of fluid
being deposited on the bottom surfaces 37 of the channel grooves 36 before
assembly,
by allowing such fluid to be pressed out between the structures (e.g. ribs) of
the pattern
40, when the plate modules 2 are pressed together during assembly. Without the
pattern
40, a fluid film might be formed between the projections 22B and the plate 3,
resulting in
an undesirably low friction there between.
Figs 10-14 illustrate a variant of the porthole gasket 22, in which the
projections
22B are provided with a different surface pattern 40, which is composed of
seven pattern
structures in the form of elongated ribs 41. Furthermore, as shown to the
lower left of the
porthole gasket 22 in Fig. 10, two of the projections 22B are formed as non-
elongated
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bulbs, which also lack surface pattern. This configuration of the projections
22 may be
governed by the design of the heat exchanger plates 3 (not shown) between
which the
porthole gasket 22 is to be installed. As further seen in Fig. 10, the
porthole gasket 22
includes a number of attachment members 22E for attachment of the porthole
gasket 22
in the ring groove 32. The attachment members 22E are provided on the inner
perimeter
of the ring portion 22A to ensure that the porthole gasket 22 is immobilized
during
assembly of the plate package 1, and in particular when the plate modules 2
are brought
into engagement with each other. Each attachment member 22E has a T-like
shape. A
connecting portion 45 extends radially inwards from the ring portion 22A to a
crossbar
portion 46. The crossbar portion 46 extends in the peripheral direction of the
porthole
gasket 22 and has two hooks 47 at its ends. The hooks 47 extend towards the
ring
portion 22A and have a cross-section that fits within the openings that are
formed by the
valleys and ridges along the port edge 31. Thus, when the porthole gasket 22
is mounted
on the heat exchanger plate 3, the hooks 47 are inserted into these openings
to
immobilize the porthole gasket 22. More particularly, the attachment members
22E are
fastened to the port edge 31 by their respective connecting portion 45
engaging with the
primary side 3', and their respective hooks 47 engaging with the secondary
side 3", of
the heat exchanger plate 3.
Fig. 15 shows a further example of a protruding surface pattern 40, which is
composed of a series of arrow-shaped ribs 41 that are spaced apart in the
longitudinal
direction of the projection 226.
Many further variants of the surface pattern 40 are conceivable within the
scope
of the invention. For example, the pattern 40 may include pattern structures
that are
essentially linear, oval, circular, zigzag-shaped or arrow-shaped, or any
combination
thereof. It is also conceivable that at least part of the pattern structures
are formed as
cuts, grooves or notches in the projection 226. It is realized that the
layout, type and
implementation of the pattern structures may be optimized for a particular
installation by
simulation and testing.
In the embodiments shown herein, the ribs 41 protrude from the bulk portion
2213" on opposite sides of the projection 226 so as to define the main contact
surfaces
226, 2213. It is currently believed that adequate performance, with respect to
friction and
ability to dispense with fluid deposits, may be achieved by applying a design
rule that
relates the height of the ribs 41 to the thickness of the bulk portion 22E.
This design rule
is further explained in relation to Fig. 12, where variable A designates the
total or
maximum thickness of the projection 226 including the ribs 41 (parallel to the
normal
direction N), and variable B designates the thickness of the bulk portion
22E", i.e. the
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thickness of the projection 226 excluding the ribs 41 (parallel to the normal
direction N).
According to the design rule, the ratio A/I3 is about 1.05-1.1 for a
projection 226 that is
provided with ribs 41 on both of its main contact surfaces 226', 2213", and
about 1.025-
1.05 for a projection 226 that is provided with ribs 41 on only one of its
main contact
surfaces 226', 2213". This means that each of the ribs 41 has a height (i.e.
an extent from
the bulk portion 2213" parallel to the normal direction N), which is
approximately 2.5-5%
of the thickness of the bulk portion 2213" parallel to the normal direction N.
This design
rule applies to any type of projection 226 that has protruding pattern
structures
("protrusions") on at least one of its main contact surfaces 226', 2213".
It is currently believed that the provision of pattern structures that extend
essentially transverse to the longitudinal direction of the respective
projection 226, such
as the ribs 41 in Figs 14-15, serve to improve the friction between the
porthole gasket 22
and the plates 3.
With specific reference to patterns 40 composed of a plurality of parallel
transversely extending ribs 41, it is currently believed that the gap distance
between the
ribs 41 should be at least half the width of the ribs 41 in the longitudinal
direction of the
projection 226, E D/2 (Fig. 14). This configuration will facilitate
manufacture of the
patterned porthole gasket 22, e.g. by molding. According to a more general
design rule,
which may be applied to any surface pattern composed of a plurality of
separated pattern
structures, the gap distance should be at least half of the smallest dimension
of the
pattern structures, as seen in plan view of the main contact surface 226',
2213", i.e.
parallel to the normal direction N of the respective main contact surface
226', 2213" (cf.
Fig. 66).
Manufacture is also facilitated by providing the respective rib 41 with a
radius at
its ends 41A, 4113, i.e. the ends 41A, 4113 are rounded in plan view (Figs 14
and 15). In
one preferred embodiment, the radius is approximately equal to half the width
of the rib
41 in the longitudinal direction of the projection 226, F 7-- D/2 (Fig. 14).
As a general
design rule, which may be applied to any surface pattern, each pattern
structure that has
a rounded end 41A, 4113 should be designed with a radius of the rounded end
41A, 4113
that is approximately equal to half of the smallest dimension of the pattern
structure, as
seen in plan view of the main contact surface 226', 2213", i.e. parallel to
the normal
direction N of the respective main contact surface 226', 2213" (cf. Fig. 66).
The surface pattern 40 need not be confined to the main contact surfaces 226',
2213", but may also be circumferential to the projections 226, so as to also
engage with
the side walls 38, 39 of the channel grooves 36. This may further enhance the
friction
between the porthole gasket 22 and the plates 3. For example, not shown, the
projection
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226 may be provided with a plurality of circumferential flanges that are
spaced from each
other in the longitudinal direction of the projection 226. These flanges may
e.g.
correspond to the ribs 41 on opposite sides of the projection 226 in Fig. 14
being
extended to meet and thereby go around the entire perimeter of the projection
226.
The above described embodiments of the present invention should only be seen
as examples. A person skilled in the art realizes that the embodiment
discussed can be
varied and combined in a number of ways without deviating from the inventive
conception.
For example, the above described plate heat exchanger is of parallel counter
flow
type, i.e. the inlet and the outlet for each fluid are arranged on the same
half of the plate
heat exchanger and the fluids flow in opposite directions through the first
and second
spaces between the heat exchanger plates 3. Naturally, the plate heat
exchanger could
instead be of diagonal flow type and/or a co-flow type.
Furthermore, the plate package 1 need not be formed by plate modules 2 that
include a number of permanently connected heat exchanger plates 3. Instead,
the plate
package 1 may be formed as a stack of individual heat exchanger plates 3 and
the weld
lines disclosed in the foregoing may be replaced by appropriate gasket
members,
including the porthole gasket 22.
Still further, the porthole gasket 22 may be used between any type of heat
exchanger plates 3 for sealing a circumferential region around overlapping
portholes.
Thus, the adjacent plates 3 need not be arranged with their primary sides 3'
facing each
other, and the secondary sides 3" facing each other, but could be arranged
with the
primary side 3' of one plate 3 facing the secondary side 3" of the other plate
3, as in
known in the art. It is also possible that the adjacent plates are of
different types.
It is also possible that all or a subset of the projections 226 are formed
without a
surface pattern 40, or that the surface pattern 40 is provided on only one of
the main
contact surfaces 226', 2213". Likewise, all or a subset of the projections 226
may be
formed as non-elongated bulbs on the outer perimeter of the ring portion 22A
(cf. Fig.
10).
Still further, the projections 226 need not be uniformly distributed around
the ring-
shaped portion 22A. Depending on the design of the plate heat exchanger 100,
it may be
advantageous to ensure that the projections 226 are uniformly distributed
around at least
a major part of the outer perimeter of the ring-shaped portion 22A.
The field and porthole gaskets need not be separated but could be connected to
each other or even integrally formed.
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It should be stressed that a description of details not relevant to the
present
invention has been omitted and that the figures are just schematic and not
drawn
according to scale. It should also be said that some of the figures have been
more
simplified than others. Therefore, some components may be illustrated in one
figure but
left out on another figure.
