U.S. patent application number 14/407555 was filed with the patent office on 2015-06-18 for plate heat exchanger.
This patent application is currently assigned to ALFA LAVAL CORPORATE AB. The applicant listed for this patent is ALFA LAVAL CORPORATE AB. Invention is credited to Klas Bertilsson, Anders Nyander, Alvaro Zorzin.
Application Number | 20150168075 14/407555 |
Document ID | / |
Family ID | 48672583 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150168075 |
Kind Code |
A1 |
Bertilsson; Klas ; et
al. |
June 18, 2015 |
PLATE HEAT EXCHANGER
Abstract
The invention relates to a plate heat exchanger including a
plate package, which plate package includes a plurality of heat
exchanger plates of at least two configurations which are joined to
each other and which alternate with each other to form a stack of
heat exchanger plates forming plate interspaces between the heat
exchanger plates. The plate interspaces are arranged to receive at
least two different fluids. At least one through hole is arranged
to extend between the exterior of the plate package and a
compartment inside the plate package, the compartment being at
least partly formed by any of the plate interspaces, wherein the at
least one through hole is formed by a thermal drilling.
Inventors: |
Bertilsson; Klas; (Eslov,
SE) ; Nyander; Anders; (Staffanstorp, SE) ;
Zorzin; Alvaro; (Romans d'lsonzo (GO), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALFA LAVAL CORPORATE AB |
Lund |
|
SE |
|
|
Assignee: |
ALFA LAVAL CORPORATE AB
Lund
SE
|
Family ID: |
48672583 |
Appl. No.: |
14/407555 |
Filed: |
June 11, 2013 |
PCT Filed: |
June 11, 2013 |
PCT NO: |
PCT/EP2013/061982 |
371 Date: |
December 12, 2014 |
Current U.S.
Class: |
165/166 ;
72/71 |
Current CPC
Class: |
F28F 9/0243 20130101;
F28F 9/0248 20130101; F28D 9/005 20130101; F28D 9/0062 20130101;
B21J 5/066 20130101; F28F 9/0273 20130101; F28F 9/00 20130101; F28D
9/0006 20130101 |
International
Class: |
F28D 9/00 20060101
F28D009/00; B21J 5/06 20060101 B21J005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2012 |
EP |
12171915.7 |
Claims
1. A plate heat exchanger including a plate package, which plate
package includes a plurality of heat exchanger plates of at least
two configurations which are joined to each other and which
alternate with each other to form a stack of heat exchanger plates
forming plate interspaces between the heat exchanger plates, the
plate interspaces being arranged to receive at least two different
fluids, wherein at least one through hole is arranged to extend
between the exterior of the plate package and a compartment inside
the plate package, the compartment being at least partly formed by
any of the plate interspaces, wherein the at least one through hole
is formed by a thermal drilling.
2. A plate heat exchanger according to claim 1, wherein the
compartment comprises a plurality of plate interspaces
communicating with each other via a common channel wherein the at
least one through hole is arranged in a wall portion defining the
common channel.
3. A plate heat exchanger according to claim 1, wherein said at
least one through hole is arranged to receive a component contained
in the group consisting of sensors such as temperature sensors,
pressure sensors and optic sensors, plugs, such as drainage plugs
or inspection glasses and connectors for tubings.
4. A plate heat exchanger according to claim 1, wherein the
longitudinal axis of the at least one through hole is arranged to
extend essentially in parallel with a general plane of the
longitudinal surface extension of the heat exchanger plates.
5. A plate heat exchanger according to claim 1, wherein the at
least one through hole is arranged in a wall portion defining a
circumferential side wall of the plate package, the side wall
extending essentially perpendicular to a general plane of the
longitudinal surface extension of the heat exchanger plates.
6. A plate heat exchanger according to claim 1, wherein the at
least one through hole has a diameter providing access to more than
one plate interspace.
7. A plate heat exchanger according to claim 1, wherein the at
least one through hole is arranged in an upper or a lower end plate
forming part of the plate package.
8. A plate heat exchanger according to claim 1, wherein the heat
exchanger plates in the plate package are permanently joined
through brazing, welding, adhesive or bonding.
9. A plate heat exchanger according to claim 1, wherein the at
least one through hole comprises a longitudinal envelope surface
defining a sleeve having a longitudinal extension being coaxial
with the longitudinal axis of the through hole and the sleeve
having a free edge portion facing the interior of the
compartment.
10. A plate heat exchanger according to claim 1, wherein the mouth
of the at least one through hole facing away from the compartment
comprises a circumferential collar formed during the thermal
drilling.
11. A plate heat exchanger according to claim 1, wherein the at
least one through hole comprises a threaded portion.
12. A plate heat exchanger according to claim 1, further comprising
a bracket arranged in or around the mouth of the at least one
through hole.
13. A plate heat exchanger according to claim 1, wherein the stack
of the plate package includes a number of first heat exchanger
plates and a number of second heat exchanger plates, which are
joined to each other and arranged side by side in such a way that a
first plate interspace is formed between each pair of adjacent
first heat exchanger plates and second heat exchanger plates, and a
second plate interspace is formed between each pair of adjacent
second heat exchanger plates and first heat exchanger plates,
wherein the first plate interspaces and the second plate
interspaces are separated from each other and provided side by side
in an alternating order in the at least one plate package.
14. A plate heat exchanger according to claim 2, wherein the common
channel comprises a plurality of through holes formed by thermal
drilling, wherein at least two of the through holes are arranged
for the supply of a first of the at least two different fluids to
the common channel.
15. A plate heat exchanger according to claim 14, wherein the first
of the at least two different fluids is supplied to the common
channel via a manifold connected to the at least two through
holes.
16. A method of providing a through hole in a plate heat exchanger,
the method comprising: providing a plate heat exchanger comprising
a plate package, which plate package includes a plurality of heat
exchanger plates of at least two configurations which are joined to
each other and which alternate with each other to form a stack of
heat exchanger plates forming plate interspaces between the heat
exchanger plates, the plate interspaces being arranged to receive
at least two different fluids, and arranging by thermal drilling at
least one through hole extending between the exterior of the plate
package and a compartment inside the plate package, the compartment
being at least partly formed by any of the plate interspaces.
Description
TECHNICAL FIELD
[0001] The present invention refers generally to a plate heat
exchanger having at least one through hole being formed by thermal
drilling. The invention also relates to a method of arranging at
least one through hole in a plate heat exchanger.
BACKGROUND ART
[0002] Heat exchangers and especially plate heat exchangers are
examples of thin walled structures for the provision of an interior
channel system for the guiding of one or several fluids between at
least one inlet and at least one outlet.
[0003] A typical plate heat exchanger is formed by a plurality of
thin heat exchangers plates arranged to form a plate package. The
plate package is formed by a number of first and second heat
exchanger plates. The heat exchanger plates may be permanently
joined to each other and arranged side by side in such a way that a
first plate interspace is formed between each pair of adjacent
first and second heat exchanger plates and a second plate
interspace is formed between each pair of adjacent second and first
heat exchanger plates. The first plate interspaces and the second
plate interspaces are separated from each other and provided side
by side in an alternating order in the plate package. Substantially
each heat exchanger plate has at least a first porthole and a
second porthole, wherein the first portholes form a first inlet
channel to the first plate interspaces and the second portholes
form a first outlet channel from the first plate interspaces.
[0004] The permanently joining may be achieved by welding, brazing,
bonding or adhesives. In such permanently joined plate heat
exchanger the positions of inlets or outlets are depending on the
first and second portholes. Also, any surface profile of the heat
exchanger plates is depending on the position of the inlets and the
outlets in order to optimize the flow through the panel interspaces
and thereby the thermal efficiency. Generally, there is a constant
struggle to reduce the size of the port holes to maximize the
available heat transfer surface of the heat exchanger plates.
[0005] The thin walled lamellae like structure formed by the
permanently joined plate heat exchanger makes it very complicated
to add additional inlets or outlets, sensors or the like since the
positioning thereof is limited to the port holes and the inlet or
outlet channels formed thereof.
[0006] There are many problems relating to making a connection or
an interface in a permanently joined plate heat exchanger. Just to
mention a few of them: It is almost impossible to create a hole in
a side thereof by preparing/pressing a pattern in the individual
plates before joining the plates to form a plate package. If
drilling or threading holes in a plate package, chips will
inevitable get into the plate package and contaminate it. Due to
the highly complex cross section of a permanently joined plate heat
exchanger, it is almost impossible to remove any chips. There is
also a risk of contamination of any devices to be arranged
downstream thereof, such as a compressor. The thin goods in the
sides, created by the flanks of the individual plates, is as such
not thick enough to allow a threaded connection. The complex and
irregular lamellae structure of a permanently joined plate heat
exchanger results in an unreliable material for machining and the
inner structures in the inlet or outlet ports may collapse.
Generally it is hard to even create surfaces to seal against in a
permanently joined plate heat exchanger. Further, provided the
permanent joining is achieved by brazing, it is difficult to solder
or weld connections, such as weld bolts, without destroying the
brazed structure. Additionally, it is very hard to make large holes
covering one or several plate interspaces.
[0007] Following these examples of problems, it is very hard to
mount connections of any additional inlets or outlets, sensors,
probes, fastening means or the like to a plate heat exchanger, and
especially to a permanently joined plate heat exchanger. This is
especially the case in a high volume production.
SUMMARY
[0008] The object of the present invention is to provide a plate
heat exchanger having at least one through hole remedying the
problems mentioned above.
[0009] Another object is to provide a method allowing an
essentially arbitrary positioning of a through hole in a plate heat
exchanger.
[0010] Further, the method should be applicable to high volume
production where a high degree of reliability and repeatability is
required.
[0011] This object is achieved by a plate heat exchanger including
a plate package which plate package includes a plurality of heat
exchanger plates of at least two configurations which are joined to
each other and which alternate with each other to form a stack of
heat exchanger plates forming plate interspaces between the heat
exchanger plates, the plate interspaces being arranged to receive
at least two different fluids. The plate heat exchanger is
characterized in that at least one through hole is arranged to
extend between the exterior of the plate package and a compartment
inside the plate package, the compartment being at least partly
formed by any of the plate interspaces, wherein the at least one
through hole is formed by a thermal drilling
[0012] Thermal drilling, also known as flow drilling, friction
drilling or form drilling is a non-cutting method providing a
plastic re-shaping of the material. The hole is formed by rotating
a pin-like tool having a circular cross section with a diameter
essentially corresponding to the hole to be formed. During
rotation, the tool creates a hole by relying on the friction that
results from the high rotational speed. The generated heat makes
the material malleable enough to be formed and perforated. As the
tip of the tool penetrates the lower surface of the base material,
the displaced material starts to flow in the direction of the tool
feed. Some displaced material may form a collar around the upper
surface of the work piece. The rest of the material may form a
sleeve-like bushing in the lower surface. The formed sleeve is
remarkably strong and may by way of example be threaded in a
separate process.
[0013] Thermal drilling has surprisingly proven to be applicable to
thin-walled, honeycomb-like structures such as plate heat
exchangers. Further, thermal drilling is a non-cutting method
leaving no contaminating chips which may cause uncontrolled
throttling or blocking in the narrow passages in the interior of
the plate heat exchanger. Also, there is no risk of chips being
formed that might constitute problems for devices to be arranged
downstream of a plate heat exchanger, such as a compressor. The
combination of the honeycomb-like structure and the strict
requirement of no chip formation has traditionally made hole making
in joined plate heat exchangers very complicated and in fact
something that has generally been avoided where possible. This is
especially the case in high volume production.
[0014] By using thermal drilling, completely new possibilities
concerning access to the interior of the plate package of a
permanently joined plate heat exchanger are provided. This involves
insertion of instruments such as sensors, cameras or the like to
improve the monitoring and understanding of the operational
conditions inside the plate heat exchanger. Also, it provides
completely new possibilities regarding positioning of inlets or
outlets for fluid supply or tubings used therefore. In fact, the
thermal drilling allows an essentially arbitrary positioning of a
through hole in a plate heat exchanger. Further, by thermal
drilling it is made possible to make large holes providing access
to more than one plate interspace.
[0015] The compartment may comprise a plurality of plate
interspaces communicating with each other via a common channel,
wherein the at least one through hole is arranged in a wall portion
defining the common channel. Thus, the wall portion may be the
circumferential envelope surface of the common channel or a
longitudinal end surface thereof. The common channel may by way of
example be an inlet or an outlet channel extending through or along
the plate package.
[0016] The at least one through hole may be arranged to receive a
component contained in the group consisting of sensors such as
temperature sensors, pressure sensors and optic sensors, plugs,
such as drainage plugs or inspection glasses and connectors for
tubings. It is to be understood that these are not limiting
examples of components possible to be applied.
[0017] The longitudinal axis of the at least one through hole may
be arranged to extend essentially in parallel with a general plane
of the longitudinal extension of the heat exchanger plates.
[0018] The at least one through hole may be arranged in a wall
portion defining a circumferential side wall of the plate package,
the side wall extending essentially perpendicular to a general
plane of the longitudinal surface extension of the heat exchanger
plates.
[0019] The at least one through hole may have a diameter providing
access to more than one plate interspace.
[0020] The at least one through hole may be arranged in an upper or
a lower end plate forming part of the plate package.
[0021] The heat exchanger plates in the plate package may be
permanently joined to each other through brazing, welding, adhesive
or bonding.
[0022] The at least one through hole may comprise a longitudinal
envelope surface defining a sleeve having a longitudinal extension
being coaxial with the longitudinal axis of the through hole, and
the sleeve may have a free edge portion facing the interior of the
compartment. The sleeve may be used for threading or for the
receipt of a bushing, lining, connector or the like. The sleeve may
also be used to provide a channel past one or several plate
interspaces to thereby provide enhanced access to the interior
structure of the plate package allowing insertion of e.g. a
sensor.
[0023] The mouth of the at least one through hole facing away from
the compartment may comprise a circumferential collar formed during
the thermal drilling. Such circumferential collar may be used for
connection of a component to be inserted into the through hole.
[0024] The at least one through hole may comprise a threaded
portion.
[0025] The plate heat exchanger may further comprise a a bracket
arranged in or around the mouth of the at least one through hole.
Such bracket may be used for mounting of a component to be inserted
into the through hole.
[0026] The stack of the plate package may include a number of first
heat exchanger plates and a number of second heat exchanger plates,
which are joined to each other and arranged side by side in such a
way that a first plate interspace is formed between each pair of
adjacent first heat exchanger plates and second heat exchanger
plates, and a second plate interspace is formed between each pair
of adjacent second heat exchanger plates and first heat exchanger
plates. The first plate interspaces and the second plate
interspaces may be separated from each other and provided side by
side in an alternating order in the at least one plate package.
[0027] The common channel may comprise a plurality of through holes
formed by thermal drilling, wherein at least two of the through
holes are arranged for the supply of a first of the at least two
different fluids to the common channel.
[0028] The first of the at least two different fluids is supplied
to the common channel via a manifold connected to the at least two
through holes.
[0029] This offers a number of advantages to be discussed below.
For a brazed plate heat exchanger the diameter of the inlet port
for the first fluid, being a cooling agent, is designed in order to
keep the fluid velocity within a certain range to avoid a too high
pressure drop. That is very important when it comes to two phase
applications to keep the efficiency and the capacity. In prior art
solutions the first fluid is supplied via one end of the inlet
channel constituting a common channel made up by port holes in each
individual heat exchanger plate. This means that the port cut
design in each individual heat exchanger plate must be dimensioned
based on the flow of first fluid supplied thereto. Also the maximum
number of heat exchanger plates must be considered since the flow
is proportional thereto. It is well known that the port size has a
strong influence on the pressure resistance to the plate heat
exchanger. The larger the worse. The design pressure of a plate
heat exchanger is typically fixed by dividing the burst pressure by
a coefficient that normally ranges between 3 and 4.5. The
coefficient value is fixed mainly according to the requirements of
the pressure vessel approval body and also according to the design
temperature. Bodies allowing the lowest coefficient require a
pressure cycling endurance test. This makes it very challenging
when designing the port areas of a plate heat exchanger. By way of
example, in a so called CO.sub.2 trans-critical gas cooler, the
design pressure has to be around 120 bar and the burst pressure has
in the best case to be 360 bar and in the worst case 540 bar.
[0030] By providing a plurality of thermally drilled through holes
in the plate package after brazing and supplying the first fluid
via these through holes the port cuts in each heat exchanger plate
may be made smaller since each of these holes only has to handle a
part of the total flow to be supplied to the plate package. That
makes the port area of the plate package stronger. Yet another
advantage is that the smaller port holes leaves a larger area of
the individual heat exchanger plates for heat transfer.
[0031] According to another aspect, the invention may relate to a
method of providing a through hole in a plate heat exchanger, the
method comprising providing a plate heat exchanger comprising a
plate package, which plate package includes a plurality of heat
exchanger plates of at least two configurations which are joined to
each other and which alternate with each other to form a stack of
heat exchanger plates forming plate interspaces between the heat
exchanger plates, the plate interspaces being arranged to receive
at least two different fluids; and arranging by thermal drilling at
least one through hole extending between the exterior of the plate
package and a compartment inside the plate package, the compartment
being at least partly formed by any of the plate interspaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Embodiments of the invention will now be described, by way
of example, with reference to the accompanying schematic drawings,
in which
[0033] FIG. 1 discloses schematically a side view of a typical
plate heat exchanger.
[0034] FIG. 2 discloses schematically a front view of the plate
heat exchanger of FIG. 1.
[0035] FIG. 3 discloses a highly schematic cross section along an
inlet or outlet channel of a typical plate package of a plate heat
exchanger
[0036] FIGS. 4 and 5 disclose highly schematic examples of first
and second heat exchanger plates of a plate heat exchanger.
[0037] FIG. 6 discloses a first embodiment of a highly schematic
cross section of a plate package of a plate heat exchanger
exemplifying different positions of through holes.
[0038] FIG. 7a-7d schematically discloses the formation of a
through hole during thermal drilling and subsequent thermal
tapping.
[0039] FIG. 8 discloses a schematic cross section of a through hole
made by thermal drilling.
[0040] FIG. 9 discloses highly schematically a cross sectional top
view of the plate package of a plate heat exchanger.
DETAILED DESCRIPTION
[0041] FIGS. 1 to 3 disclose a typical example of a plate heat
exchanger 1. The plate heat exchanger 1 includes a plate package P,
which is formed by a number of compression molded heat exchanger
plates A, B, which are provided side by side of each other to
thereby form a stack 2. The heat exchanger plates included in the
embodiment are two different heat exchanger plates, which in the
following are called the first heat exchanger plates A, see FIGS.
3,4 and 6, and the second heat exchanger plate B, see FIGS. 3, 5
and 6. The plate package P includes substantially the same number
of first heat exchanger plates A and second heat exchanger plates
B.
[0042] As is clear from FIG. 3, the heat exchanger plates A, B are
provided side by side in such a way that a first plate interspace 3
is formed between each pair of adjacent first heat exchanger plates
A and second heat exchanger plates B, and a second plate interspace
4 between each pair of adjacent second heat exchanger plates B and
first heat exchanger plates A. Every second plate interspace thus
forms a respective first plate interspace 3 and the remaining plate
interspaces form a respective second plate interspace 4, i. e. the
first and second plate interspaces 3 and 4 are provided in an
alternating order in the plate package P. Furthermore, the first
and second plate interspaces 3 and 4 are substantially completely
separated from each other.
[0043] A plurality of compartments 5 are thus formed inside the
plate package P. By way of example, a first compartment 51 is
formed at least partly by any of the first plate interspaces 3 and
a second compartment 52 is formed at least partly by any of the
second plate interspaces 4.
[0044] The plate package P also includes an upper end plate 6 and a
lower end plate 7, which are provided on a respective side of the
plate package P.
[0045] The plate heat exchanger 1 may advantageously be adapted to
operate as an evaporator in a cooling agent circuit, not disclosed.
In such an evaporator application, the first plate interspaces 3
may form passages for a first fluid, such as a cooling agent,
whereas the second plate interspaces 4 may form passages for a
second fluid, which is adapted to be cooled by the cooling
agent.
[0046] In the embodiment disclosed in FIG. 1 and FIG. 3, the heat
exchanger plates A, B and the upper and lower end plates 6, 7 are
permanently connected to each other. Such a permanent connection
may advantageously be performed through brazing, welding, adhesive
or bonding.
[0047] As appears from especially FIGS. 2, 4 and 5, substantially
each heat exchanger plate A, B has four portholes 8, namely a first
porthole 8, a second porthole 8, a third porthole 8 and a fourth
porthole 8. The first portholes 8 form a first inlet channel 9 to
the first plate interspaces 3, which extends through substantially
the whole plate package P, i. e. all plates A, B and also the upper
end plate 6. The second portholes 5 form a first outlet channel 10
from the first plate interspaces 3, which also extends through
substantially the whole plate package P, i. e. all plates A, B and
the upper end plate 6. The third portholes 5 form a second inlet
channel 11 to the second plate interspaces 4, and the fourth
portholes 5 form a second outlet channel 12 from the second plate
interspaces 4. Also these two channels 11 and 12 extend through
substantially the whole plate package P, i. e. all plates A, B and
the upper end plate 6.
[0048] In the disclosed embodiment, the first inlet channel 9 being
in communication with the first plate interspaces 3 may be seen as
a part of the first compartment 51. The first outlet channel 10,
being in communication with the first plate interspaces 3, may also
be seen as forming part of the first compartment 51. Likewise in
the disclosed embodiment, the second inlet channel 11 being in
communication with the second plate interspaces 4 may be seen as a
part of the second compartment 52. The second outlet channel 12,
being in communication with the second plate interspaces 4, may
also be seen as forming part of the second compartment 52.
[0049] In this type of prior art plate heat exchangers the first
plate interspace 3 is accessed via the first inlet channel 9 or the
first outlet channel 10, i.e. via the first compartment 51.
Likewise, the second plate interspace 4 is accessed via the second
inlet channel 11 or the second outlet channel 12, i.e. via the
second compartment 52.
[0050] In a prior art plate heat exchanger, any instruments,
sensors or the like are inserted via one of these channels 9, 10,
11, 12, whereby they allow access along the longitudinal extension
of one of these channels. However, this only allow access to a
strict limited area of the interior of the plate heat exchanger,
and especially, it allows no access to the heat transfer surface of
an individual heat exchanger plate A, B. Access to such area is
cumbersome and is for practical reasons not possible during normal
use of a system produced in large scale.
[0051] Now, for better understanding of the invention, reference
will be made to FIG. 6 disclosing a schematic cross section of an
inlet channel 9; 11 or an outlet channel 10; 12 of a typical plate
heat exchanger 1 describing one embodiment of the invention.
Although the cross section is restricted to the area in and around
an inlet or outlet channel 9; 10; 11; 12, the same principle is
applicable to any exterior wall portion of the plate package P of a
plate heat exchanger 1.
[0052] FIG. 6 discloses a plurality of first and second heat
exchanger plates A, B provided side by side in such a way that a
first plate interspace 3 is formed between each pair of adjacent
first heat exchanger plates A and second heat exchanger plates B,
and a second plate interspace 4 between each pair of adjacent
second heat exchanger plates B and first heat exchanger plates A.
Every second plate interspace thus forms a respective first plate
interspace 3 and the remaining plate interspaces form a respective
second plate interspace 4, i. e. the first and second plate
interspaces 3 and 4 are provided in an alternating order in the
plate package P. Furthermore, the first and second plate
interspaces 3 and 4 are substantially completely separated from
each other.
[0053] The circumferential side wall 13 of the plate package P
comprises a plurality of outwardly extending flanges 14, each
flange 14 being formed by the outer peripheral edge portion 15 of a
pair of adjacent first heat exchanger plates A and second heat
exchanger plates B. The circumferential side wall 13 extends
essentially perpendicular to a general plane 16 of the first and
the second heat exchanger plates A, B.
[0054] In the disclosed embodiment a plurality of through holes 20
are arranged in the circumferential side wall 13 of the plate
package P. The through holes 20 are made by thermal drilling.
Thermal drilling as a method will be described below. The
longitudinal axis L of each through hole 20 is arranged to extend
essentially in parallel with the general plane 16 of the first and
the second heat exchanger plates A, B.
[0055] In the disclosed embodiment, each first plate interspace 3
comprises a through hole 20 extending from the exterior of the
plate package P into the through channel being an inlet channel 9;
11 or an outlet channel 10; 12. It is to be understood that other
hole patterns than that illustrated may be used. Further, it is to
be understood that by thermal drilling, the through hole 20 may be
arranged in any arbitrary position along the circumferential side
wall 13 of the plate package P.
[0056] In the disclosed embodiment, the through holes 20 are
arranged with their longitudinal axis L somewhat displaced from the
adjacent flanges 14, whereby the through holes 20 are essentially
made through a portion of either of the first or the second heat
exchanger plates A, B which together form a pair of heat exchanger
plates A, B. It is to be understood that other positions are
possible.
[0057] It is to be understood that the circumferential side wall 13
of the plate package P may be essentially smooth. This may be made
e.g. by bending the plurality of outwardly extending flanges 14 to
extend essentially in parallel with the circumferential wall
portion 13 or by cutting off the flanges 14. It is also to be
understood that the cross section depends on the surface pattern 21
of the heat exchanger plates A, B constituting the plate package
P.
[0058] Further in FIG. 6, a through hole 20 is arranged in the
upper end plate 6, whereby a communication is made possible from
the exterior of the plate package P to the plate interspace 3; 4
closest to the upper end plate 6. In the disclosed embodiment, the
through hole 20 extends into a first plate interspace 3, i.e. the
first compartment 51. Any arbitrary position is possible depending
on the intended use of the through hole 20. The same principle is
applicable to the lower end plate 7.
[0059] FIG. 6 also discloses a through hole 20; 23 arranged in the
lower end plate 7. The through hole 20; 23 extends past the plate
interspace 3; 4 closest to the lower end plate 7 and into the
second, subsequent plate interspace 3; 4. In the disclosed
embodiment, the longitudinal axis L of the through hole 20; 23
extends through a joint 22 between the two joined heat exchanger
plates A, B. It is to be understood that other positions are
possible.
[0060] Further, FIG. 6 discloses one embodiment of a through hole
20; 23 having a diameter that provides access to more than one
first or second plate interspace 3, 4. The through hole 20; 23 is
disclosed with an area extending across a plurality of heat
exchanger plates A, B and thereby the partition walls 24 between
two or several plate interspaces 3, 3; 4, 4, which partition walls
24 are formed by the heat exchanger plates A, B as such.
[0061] Now turning to FIG. 9 a cross sectional top view of a plate
package P of a plate heat exchanger is disclosed highly
schematically.
[0062] The common channel 9; 10; 11; 12 for the supply and
distribution of the first fluid comprises a plurality of through
holes 20 formed by thermal drilling. The first fluid is supplied to
the common channel 9; 10; 11; 12 via a manifold 50. The manifold 50
is connected to an exterior wall 51 of the plate package P and is
communicating with the common channel 9; 10; 11; 12 via the through
holes 20.
[0063] It is to be understood that the first fluid may be
distributed into the common channel 9; 10; 11; 12 via nozzles or
valves (not disclosed) arranged in connection to said manifold.
[0064] The fluid may be supplied to the through holes 20 via
individual pipings (not disclosed) or via a manifold 50
communicating with the plurality of through holes. The through
holes may be threaded to fix necessary connections and sealed with
gaskets, o-rings or the like. Soft brazing may also be used.
[0065] It is to be understood that the through holes 20 may be
arranged in a row or in any other pattern. It is also to be
understood that the same principle is applicable not only to the
inlet port of the first fluid but also to any other port of the
plate package.
[0066] Thermal drilling, also known as flow drilling, friction
drilling or form drilling is a non-cutting method used to form a
hole. The hole may be a through hole or a blind hole. The process
is illustrated in FIGS. 7a-7c. The thermal drilling provides a
plastic re-shaping of the material. The hole 20 is formed by
rotating a pin-like tool 30 having a circular cross section with a
diameter essentially corresponding to the hole to be formed, see
FIG. 7a. The tool 30 has a cone shaped free end 31 engaging a base
material 32 with a high rotational speed and with a relatively high
axial pressure to thereby form a hole 20. The tool 30 may be made
by way of example carbide, such as Wolfram carbide. During
rotation, the tool 30 creates a hole, see FIG. 9b by relying on the
friction that results from the high rotational speed. The generated
heat makes the base material 32 malleable enough to be formed and
perforated. As the tool 30 advances in the axial direction a
material displacement occurs, see FIG. 7c. Initially the displaced
material flows upwards towards the tool. As the tip of the free end
31 of the tool 30 penetrates the lower surface 33 of the base
material 32, the displaced material starts to flow in the direction
of the tool feed. As the material softens, the axial force is
reduced and the feed rate is increased. Some displaced material may
form a collar 34 around the upper surface 35 of the base material
32. The rest of the material forms a sleeve 36 in the lower surface
33. The collar 34 and the sleeve 36 will be coaxial with the
resulting through hole 20 and have a longitudinal extension L
slightly exceeding the thickness of the base material 32. The
degree of work hardening depends on the material. As a result, the
formed sleeve 36 is remarkably strong and may by way of example be
threaded in a separate process, see FIG. 7d. The threading may be
made either internally or externally of the sleeve 36. It is to be
understood that the threading 37 may be limited to a portion of the
collar 34, the base material 32 and the sleeve 36.
[0067] Standard drilling, NC, and CNC machines are all suitable for
thermal drilling. But the process depends on the speed and force
with which the specialized tool 30 engages the base material 32. It
is to be understood that parameters such as hole size, material,
and thickness all influence the suitable rotational speed, feed
rate, and axial force. For example, thin materials may bend or
collapse under excessive pressure, necessitating adequate support
to prevent deformation. Predrilled holes may reduce the required
axial force and also leave a smooth finish in the sleeve's lower
edge. However, due to chip-formation, predrilling is normally not
an option when applied to heat exchangers. By thermal drilling
being a non-cutting method no chips are formed that might fall into
and contaminate the plate heat exchanger, such as a permanently
joined plate package, or any devices to be arranged downstream such
plate heat exchanger. Thermal drilling has surprisingly proven to
be excellent when making large holes 23 having diameters straddling
a plurality of plate interspaces 3, 3; 4, 4, like in a plate heat
exchanger 1.
[0068] Provided the sleeve 36 is to be threaded, this may be made
by using thermal tapping, basically using the same principle as
with thermal drilling with the essential difference that the
temperatures are much lower. Thermal tapping provides a plastic
re-shaping of the material. The used tool 38, see FIG. 7d, has
threads 38a and when inserted into the hole 20 during rotation, the
material in the envelope surface of the hole flows into the thread
depression and the crest 38a of the tool 38. Thus, the threads are
cold formed leaving no chips. It is to be understood that the
thread form, the depth and the strength is decided by the elected
tool 38. It is also to be understood that the treading may be made
by a non-cutting conventional plastic cold forming.
[0069] Now turning to FIG. 8, a schematic cross section of a
through hole 20 made by thermal drilling is disclosed. As a
consequence of thermal drilling being a plastic re-shaping method
in which the hole 30 is formed by displacing material instead of
cutting material, the mouth 39 of the through hole 20 intended to
face away from the plate interspace 3; 4 may comprise the
circumferential collar 34 of displaced material. It is possible to
shape the collar 34 by the tool 30 used during the thermal drilling
to control the shape of the collar 34. Further, the through hole 20
comprises on its lower side a longitudinal envelope surface
defining the sleeve 36 having a longitudinal extension being
coaxial with the longitudinal axis L of the through hole 20. The
sleeve 36 has a free edge portion 40. Also the sleeve 36 is the
result of the thermal drilling being a plastic re-shaping method.
The through hole 20 may be threaded. The threading may be made
along the full interior envelope surface 41 of the through hole 20,
i.e. from the outer edge of the collar 34 to the free edge portion
40 of the sleeve 36. Alternatively, only a portion of the envelope
surface 41 be threaded. It is to be understood that the collar 34
may be used as connecting surface for any device, or for brackets
or the like.
[0070] The through holes 20 may be used to receive or mount
different types of sensors (not disclosed) such as temperature
sensors, pressure sensors and optic sensors. The through holes 20
may also be used to mount plugs (not disclosed), such as drainage
plugs or inspection glasses. Typical drainage plugs are drainage
plugs for compressor oil and drainage plugs for system evacuation.
The through holes 20 may also be used as separate inlets or outlets
(not disclosed) for reversed cooling/heating duties.
[0071] The invention has generally been described based on a plate
heat exchanger 1 having first and second plate interspaces 3; 4 and
four port holes 8 allowing a flow of two fluids. It is to be
understood that the invention is applicable also for plate heat
exchangers having different configurations in terms of the number
of plate interspaces, the number of port holes and the number of
fluids to be handled. The invention is even applicable to plate
heat exchangers wherein one or several inlet or outlet channels
formed as through holes integrated in the heat exchanger plates are
omitted. It is further to be understood that the invention is
applicable no matter type of heat exchanger. It may by way of
example be applied to heat exchangers of the tube and shell type or
spiral heat exchangers.
[0072] The four portholes 8 are in the disclosed embodiment
provided in the proximity of a respective corner of the
substantially rectangular heat exchanger plates A, B. It is to be
understood that other positions are possible, and the invention
should not be limited to the illustrated and disclosed
positions.
[0073] The invention is also applicable to plate heat exchangers
(not disclosed) comprising pairwise permanently joined heat
exchanger plates, wherein each pair forms a cassette. In such
solution, gaskets are arranged between each cassette. Also, in such
embodiment, the heat exchanger plates forming each cassette may be
permanently joined by welding. The invention is also applicable to
plate heat exchangers (not disclosed) where the plate package is
kept together by tie-bolts extending through the heat exchanger
plates and the upper and lower end plates. In the latter case
gaskets are used between the heat exchanger plates.
[0074] The invention is not limited to the embodiment disclosed but
may be varied and modified within the scope of the following
claims, which partly has been described above.
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