Canadian Patents Database / Patent 2864231 Summary

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(12) Patent: (11) CA 2864231
(54) English Title: MODULAR PLATE AND SHELL HEAT EXCHANGER
(54) French Title: ECHANGEUR DE CHALEUR A ENVELOPPE ET PLAQUE MODULAIRE
(51) International Patent Classification (IPC):
  • F28F 3/08 (2006.01)
(72) Inventors :
  • TAYLOR, CREED (United States of America)
(73) Owners :
  • WESTINGHOUSE ELECTRIC COMPANY LLC (United States of America)
(71) Applicants :
  • WESTINGHOUSE ELECTRIC COMPANY LLC (United States of America)
(74) Agent: BERESKIN & PARR LLP/S.E.N.C.R.L.,S.R.L.
(74) Associate agent:
(45) Issued: 2020-01-21
(86) PCT Filing Date: 2013-01-04
(87) Open to Public Inspection: 2013-07-18
Examination requested: 2017-11-30
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
13/348,832 United States of America 2012-01-12

English Abstract


A modular plate and shell heat exchanger in which welded pairs of heat
transfer plates are tandemly spaced and
coupled in parallel between an inlet and outlet conduit to form a heat
transfer assembly. The heat transfer assembly is placed in the
shell in order to transfer heat from a secondary to a primary fluid. Modules
of one or more of the heat transfer plates are removably
connected using gaskets at the inlet and outlet conduits which are connected
to a primary fluid inlet and a primary fluid outlet
nozzle. The heat transfer assembly is supported by a structure which rests on
an internal track which is attached to the shell and
facilitates removal of the heat transfer plates. The modular plate and shell
heat exchanger has a removable head integral to the shell for
removal of the heat transfer assembly for inspection, maintenance and
replacement.


French Abstract

La présente invention se rapporte à un échangeur de chaleur à enveloppe et plaque modulaire, des paires soudées de plaques de transfert de chaleur étant espacées et couplées en tandem et en parallèle entre un conduit d'entrée et un conduit de sortie afin de former un ensemble de transfert de chaleur. L'ensemble de transfert de chaleur est placé dans l'enveloppe afin de transférer la chaleur provenant d'un fluide secondaire à un fluide primaire. Des modules d'une ou plusieurs plaques de transfert de chaleur sont raccordés de manière amovible à l'aide de joints d'étanchéité au niveau des orifices d'entrée et de sortie qui sont raccordés à un orifice d'entrée de fluide primaire et à une buse de sortie de fluide primaire. L'ensemble de transfert de chaleur est supporté par une structure qui reste sur un chemin interne qui est fixé à l'enveloppe et facilite le retrait des plaques de transfert de chaleur. L'échangeur de chaleur à enveloppe et plaque modulaire comprend une tête amovible intégrée à l'enveloppe pour permettre le retrait de l'ensemble de transfert de chaleur pour permettre une inspection, la maintenance et le remplacement.


Note: Claims are shown in the official language in which they were submitted.

What is claimed is:
1. A heat exchanger (10), comprising:
an elongated pressure vessel shell (34) having an axial dimension with a
removable
closure (40) at one end of the axial dimension, a primary fluid inlet (26), a
primary fluid
outlet (28), a secondary fluid inlet (42,44, 46), a drain outlet (48, 50) and
a heat transfer
assembly (36) comprising:
a primary fluid inlet conduit (22) extending into the pressure vessel (34)
from
the primary fluid inlet (26);
a primary fluid outlet conduit (24) extending into the pressure vessel (34)
from
the primary fluid outlet (28);
a plurality of pairs of heat transfer plates (16) supported in tandem with
each
of the pairs of plates sealed (70) around the periphery to define a primary
fluid flow channel
in between a first and second heat transfer plate (12, 14) of each pair, with
each pair having a
heat transfer plate inlet (72) opening fluidly connected either directly or
indirectly to the
primary fluid inlet conduit (22) and a heat transfer plate outlet opening (78)
fluidly connected
either directly or indirectly to the primary fluid outlet conduit to form a
parallel flow path
with flow in the same direction through each of the pairs of heat transfer
plates in a direction
orthogonal to the axial dimension of the pressure vessel shell;
means for expanding a heat transfer capacity of the heat transfer assembly
over an original heat transfer capacity the heat exchanger has when the heat
exchanger is first
placed into service; and
wherein the plurality of pairs of heat transfer plates (16) are arranged in
modules (17) with at least one of the modules, including at least one of the
pairs of heat
transfer plates, connected in tandem with an adjacent module or the primary
fluid inlet or the
primary fluid outlet with a nondestructively removable mechanical coupling
(84) and the
means for expanding the heat transfer capacity of the heat transfer assembly
includes a spacer
module having substantially less heat transfer capacity than the modules of
pairs of heat
transfer plates, with the spacer module connected in tandem with the modules
of pairs of heat
transfer plates, the spacer module being at least as long in the axial
dimension as the modules
of the pairs of heat transfer plates and having an inlet duct passing axially
therethrough,
fluidly connected either directly or indirectly to the primary fluid inlet
conduit and an outlet
duct passing axially therethrough, fluidly connected either directly or
indirectly to the
primary fluid outlet conduit.

2. The heat exchanger (10) of Claim 1 wherein at least some of the modules
(17)
include a plurality of the pairs of heat transfer plates (16) with the pairs
of heat transfer plates
within the at least some of the modules supported together with a tie rod
(64).
3. The heat exchanger (10) of Claim 2 wherein the at least some of the
modules
(17) connected in tandem with an adjacent module is connected by coupling
their respective
tie rods (64).
4. The heat exchanger (10) of Claim 2 or 3 wherein the heat transfer
assembly
(36) is slidable out of the pressure vessel shell (34) when the removable
closure (40) is
opened.
5. The heat exchanger (10) of Claim 1 wherein the heat transfer assembly
(36) is
moveably supported on a track (32) attached to an inside of the pressure
vessel (34) so that
the heat transfer assembly can be removed as a unit from the pressure vessel
through the one
end (40) by moving the heat transfer assembly along the track.
6. The heat exchanger (10) of Claim 5 wherein the heat transfer assembly
(36) is
supported on the track (32) on wheels (33) that ride on the track.
7. The heat exchanger (10) of Claim I wherein the primary fluid inlet (26)
and
the primary fluid outlet (28) extend from the removable closure (40).
8. The heat exchanger (10) of any one of Claims 1 to 7, wherein the heat
transfer
assembly (36) is fitted with a number of extra couplings (60) configured to
attach additional
pairs of heat transfer plates (16), the extra couplings are initially plugged
and are available for
later uprating of the heat transfer capability of the heat exchanger after the
heat exchanger has
been placed in operation over an original heat transfer capacity, by
unplugging at least some
of the extra couplings and attachment of a number of the additional pairs of
heat transfer
plates.
9. The heat exchanger (10) of Claim 1 wherein the pressure vessel shell
(34) is a
cylindrical shape with hemispherical ends (40, 38).
16

I O. The heat exchanger (10) of Claim 1 wherein at least some of the
modules (17)
comprise a plurality of pairs of heat transfer plates (16) with each of the
pairs of heat transfer
plates within a module connected together in the tandem array via a welded
coupling (23).
11. The heat exchanger (10) of Claim I wherein at least some of the modules
(17)
have a support plate (82) on a first and a second end with the heat transfer
plates (12, 14)
therebetween wherein the support plates are thicker than the heat transfer
plates.
12. The heat exchanger (10) of Claim 1 wherein the modules (17) are
supported in
tandem by tie rods (64).
13. A method of repairing, inspecting. cleaning or uprating the heat
exchanger (10) of
Claim 1 comprising the steps of:
accessing the interior of the pressure vessel shell (34);
disconnecting the primary fluid inlet conduit (22) and the primary fluid
outlet conduit (24) from
the primary fluid inlet (26) and the primary fluid outlet (28), respectively,
and
including the step of replacing a defective pair of heat transfer plates (16).
14. The method of Claim 13 including the step of increasing the number of
pairs of
heat transfer plates (16) within the heat transfer assembly (36) after the
heat exchanger (10) has
been placed in operation to uprate the heat exchanger.
17

Note: Descriptions are shown in the official language in which they were submitted.

= =
WO 2013/106240 PCT/US2013/020206
MODULAR PLATE AND SHELL HEAT EXCHANGER
BACKGROUND
I. Field
100011 The present invention relates generally to heat exchangers and, more
particularly
to modularization for stacked plate heat exchangers.
2. Description of the Related Art
100021 The feedvvater for steam generators in nuclear power plants is
typically
preheated before being introduced into the secondary side of the steam
generators. Similarly,
fcedwater is preheated before being introduced into boilers for non-nuclear
power plant
applications. Feedwater heat exchangers are typically used for this purpose.
Conventionally,
heat exchanger designs are divided into two general classes; heat exchangers
with a plate
structure and those with a tube and shell structure. The major difference in
the two classes, with
regard to both construction and heat transfer, is that the heat transfer
surfaces are mainly plates
in one structure and tubes in the other.
100031 The tube and shell heat exchanger in a number of feedwater heater
applications
employs a horizontal or vertical tubular shell having hemispherical or flat
ends. The inside of the
horizontal shell is divided into sections by a tube sheet which is normal to
the axis of the shell.
More specifically, at one end of the shell, a water chamber section is defined
on one side of the
tube sheet that includes a water inlet chamber having a water inlet opening
and a water outlet
chamber having a water outlet opening. In a U-tube tube and shell heat
exchanger plurality of
heat transfer tubes are bent at their mid portions in a U shape and extend
from the other side of
the tube sheet along the axis of the shell. These tubes are fixed to the tube
sheet at both ends such
that one end of each of the tubes opens in the water inlet chamber, while the
other end opens in
the water outlet chamber. Another type of tube and shell heat exchanger
employs straight tubes
with an inlet chamber and an outlet chamber respectively at opposite ends of
the
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tubes. The heat transfer tubes are supported by a plurality of tube supporting
plates, spaced at a
suitable pitch in the longitudinal direction of the tubes. An inlet opening
for steam and a drain
inlet and outlet are formed in the shell in the portion in which the tubes
extend.
[0004] In operation, the feedwater coming into the feedwater heater from the
water inlet
chamber flows through the U-shaped heat transfer tubes and absorbs the heat
from the heating
steam coming into the feedwater heater from the steam inlet opening to
condense the steam. The
condensate is collected at the bottom of the shell and discharged to the
outside through a drain in
the bottom of the shell. Thanks to the cylindrical shape of the shell and the
heat exchange tubes,
the structure is well suited as a pressure vessel, and thus tube and shell
heat exchangers have
been used in extremely high pressure applications.
[0005] The most significant drawback of the tube and shell heat exchangers is
their
heavy weight when compared to the surface area of the heat transfer surfaces.
Due to that, the
tube and shell heat exchangers are usually large in size. Also, it is
difficult to design and
manufacture tube and shell heat exchangers when the heat transfer, flow
characteristics and
expense are taken into account.
[0006] A typical plate heat exchanger is composed of rectangular, ribbed or
grooved
plates, which are pressed against each other by means of end plates, which, in
turn, are tightened
= to the ends of the plate stack by means of tension rods or tension
screws. The clearances
between the plates are closed and sealed with banded seals on their outer
circumference and the
= seals are also used at the flow channels. Since the bearing capacity of
the sleek plates is poor,
they are strengthened with the grooves which are usually arranged crosswise in
adjacent plates,
wherein they also improve the pressure endurance of the structure when the
ridges of the grooves
are supported by each other. However, a more important aspect is the
significance of the
grooves for heat transfer; the shape of the grooves and their angle with
respect to the flow, affect
the heat transfer and pressure losses. In a conventional plate heat exchanger,
a heat supplying
medium flows in every other clearance between the plates and a heat receiving
medium flows in
the remaining clearances. In alternate plate pairs the flow is conducted in
between the plates via
holes located in the vicinity of the comers of the plates. Each clearance
between the plates in
alternate plate pairs always contains two holes with closed rims and two other
holes functioning
as inlet and outlet channels for the clearance between the plates. The plate
heat exchangers are
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usually constructed of relatively thin plates when a small and light structure
is desired. Because
the plates can be profiled into any desired shape, it is possible to make the
heat transfer
properties suitable for almost any type of application. The greatest weakness
in conventional
plate heat exchangers is the seals which limit the pressure and temperature
endurance of the heat
exchangers. In several cases, the seals have impaired the possibility of use
with heat supplying
or heat receiving corrosive medium.
[0007] Attempts have been made to improve the plate heat exchanger
construction by
leaving out all of the seals and replacing them with soldered joints or welded
seams. Plate heat
exchangers fabricated by soldering or welding usually resemble those equipped
with seals. The
most significant external difference is the absence of tension screws between
the ends. However,
the soldered or welded structure makes it difficult if not impossible to
nondestructively
dissemble such heat exchangers for cleaning.
[0008] Attempts have been made to combine the advantages of the tube and shell
heat
exchanger and the plate heat exchanger in heat exchangers whose construction
partly resembles
both of these basic types. One such solution is disclosed in the U.S. Patent
5,088,552, in which
circular or polygonal plates are stacked on top of each other to form a stack
of plates which is
supported by means of end plates. The plate stack is encircled by a shell, the
sides of which are
provided with inlet and outlet channels for corresponding flows of heat
supplying and heat
receiving medium. Differing from the conventional plate heat exchanger, all
fluid flows into the
clearances between the plates are directed from outside the plates. When the
heat exchanger
according to the publication is closed by welding, it is possible to attain
the same pressures as
when using a tube and shell heat exchanger with the heat transfer properties
of a plate heat
exchanger.
[0009] International Publication WO 91/09262 purports to present an
improvement on
the foregoing publication, which more distinctly exhibits features typical of
both plate heat
exchangers and tube and shell heat exchangers. The circular plates are drawn
together in pairs
by welding them together by the rims of holes which form an inlet and outlet
channel. By
welding the plate pairs fabricated in the above manner together by the outer
perimeters of the
plates, a closed circuit is attained for the flow of one heat transfer medium.
Differing from the
conventional plate heat exchanger, this structure is welded and there are only
two holes in the
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plates. The flow of another heat transfer medium is directed to every other
clearance between
the plates by means of a shell surrounding the stack of plates. In order to
prevent the flow from
running between the plate stack and the shell, seals are utilized which are
primarily used as
deflectors for the flow. Obviously, pressure endurance is not required of the
deflectors. Due to
the structure of the plate stack, it is difficult to implement the seals.
Elastic rubber gaskets are
suggested for the seals so that it is possible to disassemble the heat
exchanger, e.g., for cleaning
purposes.
[0010] The shell and tube heat exchanger currently used in nuclear power
plants has a
common design flaw that when tube degradation occurs, in an effort to minimize
leakage, the
only option is to plug the damaged tube resulting in a loss of thermal duty.
The loss of thermal
duty in the feedwater system is costly for nuclear power plants and eventually
requires the
replacement of the shell and tube feedwater heater. Another limitation of the
shell and tube
design is that the shell side inspection is typically limited to small hand
holes and inspection
ports and as a result corrosion/erosion damage is difficult to detect.
Significant corrosion/erosion
has been sustained by the internal baffling which can lead to (1) flow bypass
and thermal
performance degradation, and (2) tube wear due to flow induced vibration.
Significant
corrosion/erosion has also been observed on the inner shell surface of the
shell and tube
feedwater heater design.
[0011] Therefore, a new feedwater heater design is desired for long term,
sustainable
thermal duty and for improved long term component integrity relative to the
current shell and
tube feedwater heater design. Preferably, long term, sustainable thermal duty
will be achieved
by replacement or repair of the heat transfer surfaces, as needed, instead of
requiring that the heat
transfer surface be removed from service. Additionally, it is desirable to be
able to increase the
heat transfer capability of the feedwater heater to accommodate power plant
uprates without
replacing the entire feedwater heater.
SUMMARY
[0012] The foregoing objectives are achieved by a modular plate and shell
feedwater
heater in which welded heat transfer plate pairs are placed in a shell in
order to transfer heat from
the drain flow and extraction steam to the feedwater in a nuclear power plant.
The heat transfer
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plate pairs, or welded or otherwise bonded groupings of heat transfer plate
pairs, i.e., modules of
heat transfer plate pairs, are arranged in tandem and at least some of the
modules are connected
using gaskets and share, in parallel, a common inlet conduit and an outlet
conduit which are
respectively connected to feedwater inlet and outlet nozzles. The inlet and
outlet conduits and
heat transfer plate pairs form a heat transfer assembly that is preferably
supported by a structure
which rests on and is moveable along an internal track attached to the
interior of the shell, which
facilitates removal of the heat transfer plates from the shell. The modular
plate and shell
feedwater heater has a removable head integral with the shell for removal of
the heat transfer
plates for inspection, repair or replacement. Preferably, the inlet and outlet
nozzles are sealed to
and extend through the removable head.
[0013] Preferably, the heat exchanger provided for herein includes a means for

increasing the heat exchange capacity of the unit over time to accommodate
upratings of the
plant in which the heat exchanger is installed. In one embodiment, the inlet
and outlet conduits
include a number of additional attachment points for pairs of the heat
transfer plates that are
initially plugged. In another embodiment, the inlet and outlet conduits can be
expanded by the
attachment of additional heat transfer plate pairs or modules. In the latter
embodiment, the heat
exchanger may initially be provided with a spacer module having no or
relatively negligible heat
transfer capacity that is supported in tandem with the heat transfer plate
modules. A heat transfer
plate module may later be substituted for the spacer module to increase the
heat transfer capacity
of the heat exchanger. Desirably, at least some of the couplings between the
pairs of heat
transfer plates, or modules of bonded pairs of heat transfer plates, are
detachable for ease of
repair and replacement. Preferably, tie rods connect the modules; and in the
embodiment where
the inlet and outlet conduits extend between modules, the tie rods provide
compressive force for
pressure seals at the interface of the conduit segments of the interfacing
modules to form a tight
seal.
[0014] Preferably, the heat transfer assembly is withdrawn from the shell with
the
removable head. Alternately, a manway is provided in the shell for gaining
access to the interior
of the shell for disconnecting the feedwater inlet nozzle from the feedwater
inlet conduit and for
disconnecting the feedwater outlet conduit from the feedwater outlet nozzle or
both options may
be provided.

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[0015] Desirably, the modules have support panels at each end between which
the tie
rods extend. The heat transfer plate pairs are sandwiched between the support
panels and in one
embodiment, the primary fluid inlet conduit and the primary fluid outlet
conduit pass through the
modules. Preferably, the support panels are thicker than the heat transfer
plates. In one
embodiment the heat transfer plates between the support panels are welded to
each other and to
the support panels and adjacent support panels are mechanically connected to
each other.
[0016] The invention also provides for a method of cleaning or repairing the
feedwater
heater which includes the steps of: accessing the interior of the pressure
vessel shell; removing
at least one pair of heat transfer plates from the heat transfer assembly of
heat transfer plates;
cleaning, repairing, or replacing the removed pair of heat transfer plates;
and reconnecting the
cleaned, repaired or replaced pair of heat transfer plates to the heat
transfer assembly.
Preferably, the step of accessing the interior of the pressure vessel shell
includes removing the
detachable head; and the step of removing at least one pair of heat transfer
plates comprises
removing the one pair of heat transfer plates from the feedwater inlet conduit
and the feedwater
outlet conduit.
[0017] The invention further includes a method of repairing, inspecting,
cleaning or
uprating the feedwater heater wherein the pressure vessel has a detachable
head. The method
comprises the steps of: removing the detachable head or otherwise accessing
the interior of the
pressure vessel shell; and disconnecting the feedwater inlet conduit and the
feedwater outlet
conduit from the feedwater inlet nozzle and the feedwater outlet nozzle,
respectively, while the
heat transfer assembly is in the pressure vessel. This method further includes
the step of
replacing a defective pair of heat transfer plates as well as the step of
increasing the number of
pairs of heat transfer plates after the feedwater heater has been placed in
service to uprate the
feedwater heater.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] A further understanding of the invention can be gained from the
following
description of the preferred embodiments when read in conjunction with the
accompanying
drawings in which:
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[0019] Figure 1 is an elevational view of the feedwater heater of one
embodiment of this
invention;
[0020] Figure 2 is a top view of the feedwater heater shown in Figure 1;
[0021] Figure 3 is a perspective view of another embodiment of the feedwater
heater of
this invention with the heat transfer assembly separated into modules and
partially removed from
the shell;
[0022] Figure 4 is a perspective view of one of the end modules of pairs of
heat transfer
plates of the embodiment shown in Figure 3;
[0023] Figure 5 is a perspective view, with a portion cut away, of the heat
transfer
assembly partially shown in Figures 3 and 4;
[0024] Figure 6 is a schematic of the flow of primary fluid through the
embodiment of
the feedwater heater illustrated in Figures 3-5;
[0025] Figure 7 is a side view of a heat transfer plate pair;
[0026] Figure 8 is a schematic view of one embodiment of a heat transfer plate
module
described hereafter;
[0027] Figure 9 is a schematic view of a second embodiment of a heat transfer
plate
module described hereafter;
[0028] Figure 10 is a sectional view of a spacer module described hereafter;
and
[0029] Figure 11 is a side view, partially in section, of a tie rod segment
which can be
employed to couple two heat transfer plate modules.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] Current feedwater heater designs employed in nuclear power plants
utilize a shell
and tube heat exchanger arrangement. Another general type of heat exchanger
that has been in
existence since 1923 is the plate and frame heat exchanger. The latter is
characterized by a
compact design, high heat transfer coefficients, high fluid pressure drop
within the plates and is
generally limited to low pressure fluids. The embodiments described herein
provide a plate and
shell feedwater heater that combines and optimizes the aspects of a plate and
frame heat
exchanger and the traditional shell and tube type heat exchanger that is
conveniently serviceable
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and can be easily altered, relatively inexpensively, to increase its heat
transfer capacity, where
desired.
[0031] One embodiment of the feedwater heater, 10, of the inventions claimed
hereafter
is illustrated in the elevational view shown in Figure 1 and the top view
shown in Figure 2. Two
heat transfer plates 12 and 14 are welded together to form a welded plate pair
16 that
therebetween form a flowpath for feedwater fluid as in a traditional plate
heat exchanger. In one
embodiment, the heat transfer plate pair 16 is removably connected, such as
with gaskets 18 and
bolted flange joints 20, to and in fluid communication with an inlet header
pipe 22 at one end of
the welded heat transfer plate pair 16 and an outlet header pipe 24 at the
other end of the welded
heat transfer plate pair 16. A number of these welded heat transfer plate
pairs 16 are stacked in a
spaced tandem arrangement, each coupled between the inlet header and outlet
header to form a
heat transfer assembly having a parallel flow path. One such arrangement is
shown in Figure 2.
Alternately, it should be appreciated that a number of the heat transfer plate
pairs 16 can be
coupled in series with the ends of the series arrangement removably attached
in a similar fashion
to the inlet header pipe 22 and the outlet header pipe 24. In either
embodiment, the terminal ends
of the heat transfer plate pairs 16 are connected either directly or
indirectly to the inlet header
pipe 22 and the outlet header pipe 24. The inlet header pipe 22 and the outlet
header pipe 24 are
respectively connected to a feedwater inlet and a feedwater outlet nozzle 26
and 28 preferably
using a bolted closure with gaskets in a manner similar to that described for
removably fastening
the pair of heat transfer plates 16 to the inlet and outlet header pipes 22
and 24, though it should
be appreciated that other means of removable attachment may be used.
[0032] In the embodiment shown in Figures 1 and 2, the header pipes 22 and 24
are
supported by a frame structure 30 which rests on an internal track 32 attached
to the lower
portion of the cylindrical shell 34 that forms a pressure vessel that
surrounds the heat transfer
plate assembly 36. The track 32 and wheels 33 on the frame structure 30
facilitate removal of
the heat transfer plate assembly from the shell for repair, cleaning or
uprating. In one
embodiment the shell has an integral hemispherical end 38 on one side and a
removable
hemispherical head 40 on the other side to completely enclose and seal the
heat transfer
assembly 36 within the pressure vessel formed by the cylindrical shell 34,
hemispherical end 38
and removable head 40. However, it should be appreciated that the ends need
not be
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hemispherical to take advantage of this invention, though hemispherical ends
are preferable for
high pressure applications. The removable head 40 has the feedwater inlet
nozzle 26 and the
feedwater outlet nozzle 28 extending therethrough as shown in Figures 1 and 2.
Alternately, the
hemispherical end 38 can be constructed to be removable instead of the head 40
or both can be
connected by bolted flange connections to the shell 34 for added flexibility
in gaining access to
the interior of the shell 34 to service the heat transfer plate assembly 36.
The shell 34 is also
fitted with an extraction steam inlet 42, drain inlets 44 and 46 and drain
outlets 48 and 50.
[0033] During operation, the inlet feedwater passes through the inlet nozzle
26, the inlet
header pipe 22, the heat transfer welded plate pairs 16 where it is heated by
the drain flow and
extraction steam, the outlet header pipe 24 and the outlet nozzle 28. The
extraction steam, upon
entering the feedwater heater through the extraction steam inlet 42, is
distributed by the steam
impingement plate 52 and passes through the upper shell region where it mixes
with the entering
drain flow from the drain flow inlet nozzles 44 and 46. The extraction steam
and drain flow then
pass between the heat transfer plate welded pairs 16, where it is cooled by
the feedwater and
condenses to the lower shell region where it exits through the drain flow
outlet nozzles 48 and
50.
[0034] During a plant outage, an inspection of the heat transfer plates and
shell internal
surface can be performed using the following steps. First, the shell end 38 is
unbolted at the
flange 54 and removed. The header pipes 22 and 24 may then be disconnected
from the inlet and
outlet nozzles 26 and 28. A manway 56 on the head 40 can be used to gain
access to the
connection between the inlet and outlet header pipes 22 and 24 and the inlet
and outlet nozzles
26 and 28. Alternately, when the head 40 is removed at the flange 58, the head
40 can be moved
out with the heat transfer assembly 36 sliding on the track 32 so that access
can be gained to the
connection between the inlet and outlet headers 22 and 24 and the feedwater
inlet and outlet
nozzles 26 and 28. Spool piping (not shown) will need to be removed from the
inlet and outlet
nozzles 26 and 28 before moving the head 40. Next, the heat transfer plate
assembly 36 can be
moved as a unit along the tracks 32 located in the bottom of the shell 34 to a
point where the
individual heat transfer plates 12 and 14 and the interior of the shell 34 can
be inspected for
damage. The individual heat transfer plate pairs 16 can then be cleaned or, if
necessary, repaired
or replaced. If repair or replacement is necessary, the heat transfer plate
pair 16 in need of
9

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WO 2013/106240 PCT/US2013/020206
attention can be unbolted from the inlet header pipe 22 and the outlet header
pipe 24 and
replaced with a new or repaired heat transfer plate pair 16 bolted in its
place. The outlet header
pipe 24 and inlet header pipe 22 are also provided with one or more additional
openings 60 that
are initially sealed by plugs. These additional openings can be unsealed to
accommodate
additional heat transfer plate pairs 16 if uprating in the future is
desirable.
[0035] The removable plate design allows for replacement of the heat transfer
surface
and mass production of heat transfer plates and gaskets results in a
relatively low cost for critical
spares. Employing this design makes it possible to increase the number of
plates and thus the
heat transfer area to accommodate power uprates and provides improved shell
side inspection.
[0036] While specific embodiments of the invention have been described in
detail, it
will be appreciated by those skilled in the art that various modifications and
alternatives to those
details could be developed in light of the overall teachings of the
disclosure. For example, while
separate inlet and outlet header pipes or conduits are shown in the embodiment
illustrated in
Figures 1 and 2, any other structure that performs their stated function may
also be used without
departing from the spirit of this invention. For instance, the embodiment of
the heat transfer
assembly 36 shown in Figures 3, 4 and 5, shows segments of the inlet and
outlet conduits 22 and
24 as integral parts of the heat transfer plate pairs 16. In Figures 3, 4 and
5 corresponding
components to that shown in Figures 1 and 2, are given like reference
characters. The heat
transfer plate assembly 36 in the embodiment shown in Figures 3, 4 and 5 is
formed from a
number of heat transfer plate modules 17. Four such heat transfer plate
modules are visible in
Figure 5. Each such module 17 is formed from a number of tandemly spaced heat
transfer plate
pairs 16 which are bonded together as an integral unit. Each of the modules 17
shown in Figures
3, 4 and 5 has approximately 10 such heat transfer plate pairs, though it
should be appreciated
that any number of such heat transfer plate pairs 16 may be used with the
consequence that the
more heat transfer plate pairs 16 to a module 17 the more costly the module
will be to replace.
Alternatively, the more modules there are the more will be spent on gaskets
and closure
hardware. An optimum range of the number of plates per module should be
determined on an
application specific basis based on economic considerations. Also, the number
of modules 17 in
the heat transfer assembly 36 may vary depending on the number of heat
transfer plate pairs 16

CA 02864231 2014-06-23
WO 2013/106240 PCT/US2013/020206
per module and the heat transfer requirements of the application in which the
heat exchanger is
going to be employed.
[0037] In the embodiment shown in Figures 3, 4 and 5 the outer surface (i.e.,
the front
and the back) of each heat transfer plate pair 16 has two openings on either
side with the
corresponding openings substantially aligned with each other and to which
incremental segments
23 of the inlet and outlet conduits 22 and 24 are bonded such as by welding,
brazing or any other
suitable bond that forms a substantially rigid durable joint that is
substantially impervious to the
fluids flowing in and around the inlet and outlet conduits 22 and 24 in the
area between the heat
transfer plate pairs 16. The incremental segments of the inlet and outlet
conduits 22 and 24 that
pass between the heat transfer plate pairs 16 and the outside surface of the
adjoining heat transfer
plate pairs 16 provide a flow path between the heat transfer plate pairs 16
for the extraction
steam and drain flow to pass. The outer end of the segments 23 of the inlet
and outlet conduits
22 and 24 formed through each module 17 preferably have a flange on which the
corresponding
flange of an adjacent heat transfer plate module segment 23 can be connected;
preferably with a
gasket pressed between the flanges. The outer segments 23 on each module 17
may then be
attached to a corresponding segment 23 on the outer side of an adjacent module
with a gasket in
between using the tie rods 64 shown in Figures 3, 4 and 5, though other forms
of mechanical
attachment may be used in place of the tie rods. In the embodiment shown in
Figures 3, 4 and 5,
the modules 17 are held in position by front and rear face frames or plates 62
that are drawn
together by tie rods 64. The face plate 62 in the front of the heat transfer
plate assembly has
openings for the inlet and outlet conduits 22 and 24 so that the flanges on
the outer segments 23
can be respectively attached to the inlet and outlet nozzles 26 and 28 (shown
in Figure 2). The
outer segments 23, i.e., both inlet and outlet on the rear heat transfer plate
at the end 80 of the
heat transfer assembly 36 are either plugged to close the feedwater flow loop
or the rear heat
transfer plate is made without the inlet and outlet holes.
[0038] A schematic of the flow of the primary fluid through the heat transfer
plate
assembly of the embodiments described above having a parallel flow path
through the heat
transfer plate pairs 16 is illustrated in Figure 6. Figure 7 shows the
construction of the heat
transfer plate pairs. As shown in Figure 7, a weld bead 66 extends around each
of the
inciciuental segments 23 of the inlet conduit 22 at the corresponding openings
in the heat
11

CA 02864231 2014-06-23
WO 2013/106240 PCT/US2013/020206
transfer plates 12 and 14 and form a fluid tight seal at the interface.
Similarly, a weld bead 68
extends around the incremental segments 23 of the outlet conduit 24 at the
corresponding
openings in the heat transfer plates 12 and 14 and form a fluid tight seal at
the interface.
Furthermore, a girth weld 70 extends around the entire circumference of the
heat transfer plate
pair 16. As shown in Figure 7, the primary fluid enters the inlet conduit 22
inlet 72 of each heat
transfer plate pair 16 connecting it to adjacent pairs or support plates. A
portion of the fluid
flows down between the heat transfer plates 12 and 14 where it absorbs heat
from the extraction
steam and drain flow passing on the outside of the heat transfer plate pairs
and exits at the outlet
78 to the outlet conduit 24 where it joins with the primary fluid upstream
flow from other heat
transfer plate pairs that entered through the outlet conduit inlet 76 to the
heat transfer plate pair
16. Except for the last heat transfer plate pair 16 at the end 80 (Figure 5)
of the heat transfer
plate assembly 36, the remainder of the primary fluid entering the inlet 72
which did not flow
between the heat transfer plates 12 and 14 of a given heat transfer plate pair
16 exits through the
inlet conduit outlet 74 to the next heat transfer plate pair 16. All of the
primary fluid traversing
the inlet conduit to the end 80 of the heat transfer plate assembly 36 is
conducted through the last
pair of heat transfer plates 12 and 14 where it exits through the outlet
conduit 24 as shown in
Figure 6. It is irrelevant whether the water flows up (as shown in Figure 6),
down (as described
here) or sideways through the heat transfer plate pairs 16 as long as the flow
extends from the
inlet conduit 22 to the outlet conduit 24.
[0039] Figure 8 is a schematic of one embodiment of a heat transfer plate
module 17.
The module 17 is shown with four heat transfer plate pairs 16, though as
previously stated the
number of heat transfer plate pairs 16 may vary. The heat transfer plate pairs
16 have relatively
thin heat transfer plates 12 and 14, as compared to the outer support plates
82, which are thicker
than the inner heat transfer plate pairs 16. The support plates 82 are
referred to as support plates
and are longer than the others and extend past the others to accept the tie
rods shown in Figures
3, 4 and 5, though it should be appreciated that this embodiment is slightly
different than the
embodiment shown in Figures 3, 4 and 5. However, the way in which the modules
are secured
to each other is the same, though it should be appreciated that other means of
securing the
modules together, e.g., continuous threaded rods, bolts, etc., could also be
used. The inner heat
transfer plates are welded to each other with the conduit incremental segments
23 (shown in
12

CA 02864231 2014-06-23
WO 2013/106240
PCT/US2013/020206
Figure 4) extending therebetween, with the welds extending around the circular
openings in the
incremental segments of the inlet conduit 22 and outlet conduit 24, and the
outer edges by the
circumferential plate welds 70. Gasket grooves 84 are provided around the
inlet conduit 22 and
outlet conduit 24 openings in the support plates 82 for gaskets to seal the
openings at the
interface with mating support plates 82 of adjoining modules 17.
[0040] A second embodiment of a heat transfer plate pair module 17 is shown in
Figure
9. The embodiment shown in Figure 9 is very similar to that described above
with regard to
Figure 8 except the outside heat transfer plates have a gasket retaining ring
86 around the
openings to the inlet conduit 22 and outlet conduit 24. A single support plate
is interposed
between the modules 17 and gaskets on the retaining rings 86 seal the openings
22 and 24
between each support plate and the heat transfer plates. Alternately, grooves
can be provided on
one or both sides of the support plates for retaining the gaskets.
[0041] A spacer module 88 may be inserted in place of a heat transfer plate
pair module
17 to preserve space for the later addition of another heat transfer plate
pair module 17 should a =
future uprating of the plant in which the heat exchanger is installed require
additional heat
transfer capacity within the existing shell. One embodiment of such a spacer
module 88 is
illustrated in Figure 10. The spacer module 88 is, preferably, the same size
as a standard heat
transfer plate pair module 17 for the heat exchange unit 10 in which it is to
be employed. The
spacer module in this embodiment has two support plates 82 with gasket grooves
84, as
previously described, that are separated by an upper support 96 and lower
support 98 with a
secondary fluid drain 94. It should be appreciated that the upper support 96
and lower support
98 may (but need not) be part of one continuous support cylinder. The
embodiment shown in
Figure 10 is intended to be inserted between heat transfer plate pair modules
17 and has a pipe 90
which is welded around its circumference at each support plate interface to
form a hermetic seal.
The pipe 90 forms a portion of the inlet conduit 22, carrying the primary
fluid between the heat
transfer plate pair modules 17 that it connects. Similarly a pipe 92 is sealed
to and spans the
space between the support plates 82 of the spacer module 88 to carry the
primary fluid through
the outlet conduit 24. If the spacer is used at the end of the end 80 of the
heat transfer plate
assembly 36 then the openings in the spacer module support plates 82 is
unnecessary.
13

CA 02864231 2014-06-23
WO 2013/106240 PCT/US2013/020206
[0042] Figure 11 illustrates one embodiment of a tie rod arrangement that can
be used to
draw the modules 17 and 88 together. The tie rod 64 is designed to span
between support plates
82, similar to the spans between support frames 62 shown in Figure 5. In the
embodiment shown
in Figure 11, the tie rods 64 have one end with a reduced diameter that has a
circumferential
thread 104. The circumferential thread 104 terminates at a bearing surface 106
that is sized to
abut one side of a periphery of a module support plate around a hole in which
the thread 104 is
sized to extend through and out the other side. The other end of the tie rod
64 has an internal
thread 100 that is sized to mate with an external circumferential thread 104
on an adjoining tie
rod 64 which is extended through a corresponding hole in an adjoining support
plate 82.
Preferably, the outer circumference 102 around tie rod end having the internal
thread 100 has a
square or hex contour on which a torque can readily be applied.
[0043] As previously mentioned, the heat transfer plate assembly 36 has wheels
33 that
ride on the track 32 previously described to facilitate servicing of the heat
transfer plate
assembly. Servicing is the same as described for the embodiment illustrated in
Figures 1 and 2,
except to uprate the heat transfer plate assembly, the spacer module 88 is
removed and an
additional heat transfer plate module 17 is coupled in its place.
[0044] Additionally, while the preferred embodiment is described in an
application to a
feedwater heater the invention can be employed with similar benefits in most
other types of heat
exchangers. Accordingly, the particular embodiments disclosed are meant to be
illustrative only
and not limiting as to the scope of the invention which is to be given the
full breadth of the
appended claims and any and all equivalents thereof.
14

A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
Forecasted Issue Date 2020-01-21
(86) PCT Filing Date 2013-01-04
(87) PCT Publication Date 2013-07-18
(85) National Entry 2014-06-23
Examination Requested 2017-11-30
(45) Issued 2020-01-21

Abandonment History

There is no abandonment history.

Maintenance Fee

Last Payment of $200.00 was received on 2020-12-03


 Upcoming maintenance fee amounts

Description Date Amount
Next Payment if small entity fee 2022-01-04 $100.00
Next Payment if standard fee 2022-01-04 $204.00 if received in 2021
$203.59 if received in 2022

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Patent fees are adjusted on the 1st of January every year. The amounts above are the current amounts if received by December 31 of the current year. Please refer to the CIPO Patent Fees web page to see all current fee amounts.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $400.00 2014-06-23
Maintenance Fee - Application - New Act 2 2015-01-05 $100.00 2014-06-23
Registration of a document - section 124 $100.00 2014-09-12
Maintenance Fee - Application - New Act 3 2016-01-04 $100.00 2015-12-16
Maintenance Fee - Application - New Act 4 2017-01-04 $100.00 2016-12-19
Request for Examination $800.00 2017-11-30
Maintenance Fee - Application - New Act 5 2018-01-04 $200.00 2017-12-18
Maintenance Fee - Application - New Act 6 2019-01-04 $200.00 2018-12-17
Final Fee 2019-12-09 $300.00 2019-11-20
Maintenance Fee - Application - New Act 7 2020-01-06 $200.00 2019-12-18
Maintenance Fee - Patent - New Act 8 2021-01-04 $200.00 2020-12-03
Current owners on record shown in alphabetical order.
Current Owners on Record
WESTINGHOUSE ELECTRIC COMPANY LLC
Past owners on record shown in alphabetical order.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Document
Description
Date
(yyyy-mm-dd)
Number of pages Size of Image (KB)
Abstract 2014-06-23 1 72
Claims 2014-06-23 4 133
Drawings 2014-06-23 8 226
Description 2014-06-23 14 774
Representative Drawing 2014-06-23 1 40
Cover Page 2014-10-31 1 61
Assignment 2014-06-23 6 199
PCT 2014-06-23 1 47
Correspondence 2014-09-12 2 55
PCT 2014-08-26 1 22
Assignment 2014-09-12 6 238
Prosecution-Amendment 2017-11-30 1 47
Prosecution-Amendment 2018-12-04 3 200
Prosecution-Amendment 2019-05-07 6 226
Description 2019-05-07 14 782
Claims 2019-05-07 3 115
Correspondence 2019-11-20 2 61
Cover Page 2020-01-14 1 54