MX2014008117A

MX2014008117A - Modular plate and shell heat exchanger.

Info

Publication number: MX2014008117A
Application number: MX2014008117A
Authority: MX
Inventors: Creed Taylor
Original assignee: Westinghouse Electric Corp
Priority date: 2012-01-12
Filing date: 2013-01-04
Publication date: 2014-08-27
Also published as: BR112014016949A2; TWI593934B; CA2864231A1; EP2802835A4; CA2864231C; KR20140112543A; KR101962996B1; TW201339532A; EP2802835B1; ES2699809T3; CN104040282A; JP2015505027A; CN104040282B; MX368753B; JP6200433B2; EP2802835A1; WO2013106240A1; BR112014016949B1

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.

Description

MODULAR HEATING EXCHANGER OF PLATES AND COVER CROSS REFERENCE OF THE RELATED APPLICATION The present application is a continuation in part of the United States Patent Application Serial No. 12 / 432,147, filed on April 29, 2009.

FIELD OF THE INVENTION The present invention relates in general to heat exchangers and, more particularly, to modularization for heat exchangers of stacked plates.

BACKGROUND OF THE INVENTION The feed water for steam generators in nuclear power plants is normally preheated before entering the secondary side of the steam generators. Similarly, the feed water is preheated before entering boilers for applications other than nuclear power plants. The feedwater heat exchangers are normally used for this purpose. Conventionally, designs of heat exchangers are divided into two general classes; heat exchangers with a plate structure and those with a tube and cover structure. The main difference between the two classes, with respect to both the construction and the heat transfer, is that the heat transfer surfaces are mainly plates in one structure and tubes in the other.

The tube and cover heat exchanger employs, in a number of feedwater heater applications, a horizontal or vertical tubular cover having hemispherical or flat ends. The interior of the horizontal roof is divided into sections by a tube sheet that is perpendicular to the axis of the roof. More specifically, at one end of the cover, 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. water that has a water outlet opening. In a tube heat exchanger and tube type cover U, a plurality of transfer tubes of heat bend in their middle portions in a U-shape and extend from the other side of the tube sheet along the axis of the cover. These tubes are fixed to the tube sheet at both ends so 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 cover heat exchanger employs straight tubes with an inlet chamber and an outlet chamber respectively at opposite ends of the tubes. The heat transfer tubes are supported by a plurality of plates supporting the tubes, spaced at a suitable distance in the longitudinal direction of the tubes. An inlet opening for steam and a drain inlet and outlet are formed in the cover in the portion in which the tubes extend.

In operation, the feed water entering the feed water heater from the water inlet chamber flows through the U-shaped water transfer tubes and absorbs the heat from the heating steam entering the water. Feed water heater from the steam inlet opening to condense the steam. The condensate is collected in the lower part of the roof and discharged to the outside through a drain in the lower part of the roof. Thanks to the cylindrical shape of the cover and the heat exchange tubes, the structure is suitable as a pressure vessel and, thus, tube and cover heat exchangers have been used in extremely high pressure applications.

The most significant drawback of tube and deck heat exchangers is their great weight when compared to the surface area of the heat transfer surfaces. Because of that, the tube and cover heat exchangers are usually large in size. In addition, it is difficult to design and manufacture shell and tube heat exchangers when taking into account heat transfer, flow characteristics and expenditures.

A typical plate heat exchanger consists of rectangular, ribbed or grooved plates that press together with end plates which, in turn, are secured to the ends of the plate stack by tension rods or tension screws. The free spaces between the plates are They close and seal with band seals on their outer circumference and the seals are also used in the flow channels. Since the bearing capacity of the smooth plates is not very good, they are reinforced with the grooves that are normally arranged transversely in the adjacent plates, in which they also improve the pressure resistance of the structure when the ridges of the grooves are they support each other. However, a more important aspect is the importance of the slots for heat transfer; The shape of the grooves and their angle with respect to the flow affect the heat transfer and the pressure losses. In a conventional plate heat exchanger, a heat supply means flows in any other free space between the plates and the heat receiving medium flows into the remaining clearances. In alternating pairs of plates, the flow is conducted between the plates by means of holes located in the vicinity of the corners of the plates. Each free space between the plates in alternating pairs of plates always contains two holes with closed edges and two other holes that function as input and output channels for the free space between the plates. Plate heat exchangers are usually constructed of relatively thin plates when a small, light structure is desired. Since the plates can be profiled with 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 lies in the joints that limit the pressure and temperature resistance of the heat exchangers. In several cases, the joints have reduced the possibility of use with a corrosive medium heat sink or heat supplier.

Attempts have been made to improve the construction of the plate heat exchanger by removing all joints and replacing them with welded joints or welded joints. Plate heat exchangers manufactured by welding usually resemble those that are equipped with gaskets. The most significant external difference is the absence of tension screws between the ends. However, the welded structure makes it difficult, if not impossible, to non-destructively remove such heat exchangers for cleaning.

Attempts have been made to combine the advantages of the tube and cover heat exchanger and the plate heat exchanger in heat exchangers whose construction resembles in part these two basic types. One solution is disclosed in 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 end plates. The plate stack is surrounded by a cover, the sides of which are provided with inlet and outlet channels for corresponding flows of a heat supplying medium and heat sink. Unlike the conventional plate heat exchanger, all the fluid flows in the free spaces between the plates and is directed from the outside of the plates. When the heat exchanger according to the publication is closed by welding, it is possible to achieve the same pressure as when using a tube and cover heat exchanger with the heat transfer properties of a plate heat exchanger.

International Publication WO 91/09262 aims to present an improvement over the previous publication, which more clearly exhibits typical features both of plate heat exchangers as well as shell and tube heat exchangers. The circular plates are joined in pairs by welding them together at the edges of holes that form an inlet and outlet channel. By welding together the pairs of plates manufactured in the above manner by the outer perimeters of the plates, a closed circuit for the flow of a heat transfer medium is achieved. Unlike the conventional plate heat exchanger, this structure is welded and there are only two holes in the plates. The flow of another heat transfer medium is directed to any other free space between the plates by a cover surrounding the stack of plates. To prevent the flow from running between the stack of plates and the cover, joints are used which are mainly used as deflectors for flow. Obviously, deflection pressure resistance is not required. Due to the structure of the plate stack it is difficult to implement the joints. For joints, rubber gaskets are suggested so that it is possible to disassemble the heat exchanger, for example, for cleaning purposes.

The roof and tube heat exchanger currently used in nuclear power plants has a common design flaw which is that when degradation occurs in the pipe, in an effort to minimize leakage, the only option is to plug the damaged pipe, which has as a result a loss of thermal power. The loss of thermal power in the feedwater system is very costly for nuclear power plants and ultimately requires the replacement of the water heater for cover and pipe feed. Another limitation of the cover and tube design is that the inspection of the side of the cover is usually limited to small hand holes and inspection ports and, as a result, corrosion / erosion damage is difficult to detect. Significant corrosion / erosion has been maintained by the internal deviator apparatus which can lead to (1) flow deviation and thermal performance degradation and (2) tube wear due to flow induced vibration. Significant corrosion / erosion has also been observed on the surface of the inner cover of the roof and tube feed water heater design.

Therefore, a new long-term water heater design, sustainable thermal power and improved long-term component integrity are desired in relation to the current design of the roof and pipe feed water heater. Preferably, in the long term, sustainable thermal power is achieved by replacing or repairing heat transfer surfaces, as needed, instead of requiring the heat transfer surface to be removed from service. Additionally, it is desirable to be able to increase the heat transfer capacity of the feed water heater to incorporate improvements in the plants without replacing the entire feed water heater.

BRIEF DESCRIPTION OF THE INVENTION The above objectives are achieved by a modular plate and cover feeding water heater in which pairs of welded heat transfer plates are placed in a cover to transfer heat from the drainage flow and extracting steam to the feed water in a nuclear power plant The pairs of heat transfer plates, or groups welded or otherwise bonded to pairs of heat transfer plates, i.e. modules of heat transfer plate pairs, are arranged in tandem and at least some of the modules they are connected using gaskets and share, in parallel, a common inlet duct and an outlet duct that respectively connect to feed water inlet and outlet nozzles. The inlet and outlet ducts and the pairs of heat transfer plates form a heat transfer assembly that is preferably supported by a structure that rests and moves along an internal slider attached to the interior of the cover, which facilitates the removal of heat transfer plates from the cover. The Modular Plate and Cover Power Water Heater has a removable lid that forms part of the cover to remove the heat transfer plates for inspection, replacement or repair. Preferably, the inlet and outlet nozzles are sealed to the removable cover and extend therethrough.

Preferably, the heat exchanger provided herein includes a means for increasing the heat exchange capacity of the unit with the passage of time to allow improvements to the plant in which the heat exchange is installed. In one embodiment, the inlet and outlet conduits include a number of additional attachment points for pairs of heat transfer plates that are initially capped. In another embodiment, the inlet and outlet conduits can be expanded by bonding pairs of additional heat transfer plates or modules. In the latter embodiment, the heat exchanger may initially be provided with a separator module that has no heat transfer capacity, or where it is relatively insignificant, which is supported in tandem with the heat transfer plate modules. A module of heat transfer plates can be replaced more forward through the separator module to increase the heat transfer capacity of the heat exchanger. Desirably, at least some of the couplings between pairs of heat transfer plates or paired modules of heat transfer plates can be removed for ease during repairs and replacements. Preferably, tie rods connect the modules; and in the embodiment where the inlet and outlet conduits extend between the modules, the tension rods provide compressive force for the pressure joints in the interconnection of the conduit segments of the interconnection modules to form a seal.

Preferably, the heat transfer assembly is removed from the cover with the removable cover. As an alternative, a manhole is provided on the cover to gain access to the inside of the cover to disconnect the feed water inlet nozzle from the feed water inlet duct and to disconnect the feed water outlet duct from the feed water inlet duct. the feed water outlet nozzle, or both can be provided.

Desirably, the modules have support panels at each end between which the tension rods extend. The pairs of heat transfer plates are trapped between the support panels and, in one embodiment, the primary fluid inlet conduit and the primary fluid exit 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 together and the support panels and the adjacent support panels are mechanically connected to each other.

The invention also provides a method of cleaning or repairing the feed water heater that includes the steps of: accessing the interior of the pressure vessel cover; removing at least one pair of the heat transfer plates from the heat transfer assembly of the heat transfer plates; clean, repair or replace the removed pair of heat transfer plates; and reconnecting the pair of heat transfer plates, cleaned, repaired or replaced in the heat transfer assembly.

Preferably, the step of accessing the interior of the pressure vessel cover includes removing the removable cover; and the step of removing at least a pair of the heat transfer plates comprises removing a pair of heat transfer plates from the feed water inlet conduit and the feed water outlet conduit.

The invention further includes a method of repair, inspection, cleaning or improvement of the feed water heater in which the pressure vessel has a removable lid. The method comprises the steps of: removing the removable lid or otherwise accessing the interior of the pressure vessel cover; and disconnect the feed water inlet duct and the feed water outlet duct from the feed water inlet nozzle and the feed water 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 feed water heater goes into operation to improve the heater of water supply.

BRIEF DESCRIPTION OF THE DRAWINGS A further understanding of the invention can be obtained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: Figure 1 is an elevational view of the feed water heater of an embodiment of this invention; Figure 2 is a top view of the feed water heater shown in Figure 1; Figure 3 is a perspective view of another embodiment of the feed water heater of this invention with the heat transfer assembly separated into modules and partially removed from the cover; 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; Figure 5 is a perspective view, with a cutout portion, of the heat transfer assembly partially shown in Figures 3 and 4; Figure 6 is a schematic of the primary fluid flow through the embodiment of the feedwater heater illustrated in Figures 3-5; Figure 7 is a side view of a pair of heat transfer plates; Figure 8 is a schematic view of an embodiment of a heat transfer plate module described hereinafter; Figure 9 is a schematic view of a second embodiment of a heat transfer plate module described hereinafter: Figure 10 is a sectional view of a separator module described hereinafter; Y Figure 11 is a side view, partially in section, of a tension stringer segment that can be used to couple two heat transfer plate modules.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Current designs of feedwater heater used in nuclear power plants use a roof and tube heat exchanger arrangement. Another general type of heat exchanger that has existed since 1923 is the plate and frame heat exchanger. The latter is characterized by a compact design, high heat transfer coefficients, a high drop in fluid pressure within the plates and is generally limited to low pressure fluids. The embodiments described herein provide a plate and cover feed water 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 useful and that it can be easily altered, relatively cheaply, to increase its heat transfer capacity, where desired.

An embodiment of the feed water heater 10 of the claimed inventions hereinafter is illustrated in the elevational view shown in Figure 1 and in the top view is shown in Figure 2. Two transfer plates 12 and 14 of heat are welded together to form a pair of welded plates 16 which, in between, form a flow path for the feedwater fluid as in a traditional plate heat exchanger. In one embodiment, the pair of heat transfer plates 16 is removably connected, such as with gaskets 18 and flange joints 20 bolted to and in fluid communication with an inlet manifold pipe 22 at one end of the pair of plates. heat transfer 16 welds and an outlet manifold pipe 24 at the other end of par 16 of heat transfer plates welded. A number of these pairs of heat transfer plates 16 welded are stacked in a separate tandem arrangement, each coupled between the input header and the output header to form a heat transfer assembly having a parallel flow path . Such an arrangement is shown in Figure 2. As an alternative, it should be appreciated that a number of pairs of heat transfer plates 16 can be coupled in series to the ends of the series arrangement removably attached in a manner similar to the pipe 22 collector of entrance and to the pipe 24 collector of exit. In both embodiments, the end ends of the pairs of heat transfer plates 16 are connected directly or indirectly to the inlet header pipe 22 and to the outlet header pipe 24. The inlet header pipe 22 and the outlet header pipe 24 are respectively connected to a feed water inlet nozzle 26 and to a feed water outlet nozzle 28 preferably using a joint bolted closure in a manner similar to that described for releasably attaching the pair of heat transfer plates 16 to the inlet and outlet manifold 22 and 24 pipes, although it should be appreciated that other removable attachment means may be used.

In the embodiment shown in Figures 1 and 2, the collector pipes 22 and 24 are supported by a frame structure 30 that rests on an internal slide 32 attached to the lower portion of the cylindrical cover 34 that forms a pressure vessel surrounding the set 36 of heat transfer plates. The slide 32 and the wheels 33 of the frame structure 30 facilitate the removal of the set of heat transfer plates from the structure for repair, cleaning or improvement. In one embodiment, the cover has a hemispherical end 38 that forms part of it on one side and a hemispherical cover 40 removable on the other side to completely surround and close the heat transfer assembly 36 within the pressure vessel formed by the cylindrical cover 34, hemispherical end 38 and removable cover 40. However, it should be appreciated that the ends do not need to be hemispherical to take advantage of this invention, although hemispherical ends are preferred for high pressure applications. The removable cap 40 has the feed water inlet nozzle 26 and the feed water outlet nozzle 28 extending therethrough as shown in Figures 1 and 2. Alternatively, the hemispherical end 38 can constructed to be removable in place of the cap 40 or both can be connected by bolted flange joints to the cover 34 for added flexibility by gaining access to the interior of the cover 34 to perform the maintenance of the heat transfer plate assembly 36. The cover 34 is also equipped with an extraction steam inlet 42, drain inlets 44 and 46 and drain outlets 48 and 50.

During operation, the input feed water passes through the inlet nozzle 26, the inlet header pipe 22, the pairs of welded heat transfer plates 16 where it is heated by the drain flow and the exhaust steam , the outlet manifold pipe 24 and the outlet nozzle 28. The extraction steam, when entering the feed water heater through the extraction steam inlet 42, is distributed via the steam effect plate 52 and passes through the upper region of the cover where it is mixed with the steam. the incoming drain flow from nozzles 44 and 46 of drainage flow inlet. The extraction steam and the drainage flow then pass between the welded pairs of heat transfer plates 16, where they are cooled by the feed water and condensed towards the lower region of the cover where they exit through the nozzles 48 and 50 drainage flow output.

During a power failure in the plant, an inspection of the heat transfer plates and the inner surface of the cover can be carried out using the following steps. First, the end 38 of the cover is released from the bolts in the flange 54 and removed. The pipes 22 and 24 collectors can then be disconnected from the inlet and outlet nozzles 26 and 28. A manhole 56 in the cap 40 can be used to gain access to the connection between the inlet and outlet manifolds 22 and 24 and the inlet and outlet nozzles 26 and 28. Alternatively, when the lid 40 is removed in the flange 58, the lid 40 can be removed with the heat transfer assembly 36 that slides in the slider 32 so that access can be gained to the connection between the headers 22 and 24 of inlet and outlet and nozzles 26 and 28 of feed water inlet and outlet. A length of pipe (not shown) will need to be removed from the inlet and outlet nozzles 26 and 28 before the lid 40 is moved. Thereafter, the heat transfer plate assembly 36 can move as a unit along the lengths of the plates. slides 32 located at the bottom of the cover 34 to a point where the individual heat transfer plates 12 and 14 and the interior of the cover 34 can be inspected for damage. The individual pairs of heat transfer plates 16 can then be cleaned or, if necessary, repair or replace. If a repair or replacement is necessary, the pair of heat transfer plates 16, which need attention, can be released from the bolts from the inlet header pipe 22 and the outlet header pipe 24 and moved with a new or repaired pair of 16 heat transfer plates bolted in place. The outlet manifold pipe 24 and the inlet header pipe 22 are also provided with one or more additional openings 60 which are initially sealed by plugs. These additional openings can be opened to incorporate additional pairs of heat transfer plates 16 if improvements are desired in the future.

The design of the removable plate allows the replacement of the heat transfer surface and the mass production of plates and heat transfer joints results in relatively low costs of critical spare parts. Employing this design makes it possible to increase the number of plates and, in this way, the heat transfer area to incorporate improvements of power and provide an improved inspection of the side of the cover.

Although specific embodiments of the invention have been described in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the general teachings of the disclosure. For example, although separate inlet and outlet collection pipes are shown in the embodiment illustrated in Figures 1 and 2, any other structure that performs its designated function could also be used without departing from the spirit of the invention. For example, the embodiment of the heat transfer assembly 36 shown in Figures 3, 4 and 5, shows segments of the inlet and outlet ducts 22 and 24 as parts that are part of the heat transfer plate pairs. 16. Figures 3, 4 and 5 provide components corresponding to those shown in Figures 1 and 2 as 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 of those heat transfer plate modules are visible in Figure 5. Each of these modules 17 is formed from a number of pairs of heat transfer plates 16 separated in tandem which are joined together as a unit. complete Each of the modules 17 shown in Figures 3, 4 and 5 has about 10 such pairs of heat transfer plates, although it should be appreciated that any number of such pairs of heat transfer plates 16 can be used with the The result is that the more pairs of heat transfer plates 16 have a more expensive module 17 will be to replace the module. As an alternative, the more modules there are, the more money will be spent on meetings and closing tools. An optimal range of the number of plates per module should be determined in a specific manner in an application based on economic considerations. In addition, the number of modules 17 in the heat transfer assembly 36 may vary depending on the number of heat transfer plate pairs 16 per module and the heat transfer requirements of the application in which the heat exchanger is to be used. hot.

In the embodiment shown in Figures 3, 4 and 5, the outer surface (ie, the front and rear) of each pair of heat transfer plates 16 has two openings on each side with the corresponding openings substantially aligned with each other and to which additional segments 23 of the inlet passages 22 and 24 are joined. and output by welding, brazing or any other suitable joint that forms a substantially rigid durable joint that is substantially impermeable to fluids flowing in and around the inlet and outlet ducts 22 and 24 in the area between the pairs of plates. heat transfer 16. The additional segments of the inlet and outlet ducts 22 and 24 passing between the pairs of heat transfer plates 16 and the outer surface of the pairs of adjacent heat transfer plates 16 provide a fluid path between the pairs of heat transfer plates 16 to pass the extraction steam and the drainage flow. The outer end of the segments 23 of the inlet and outlet ducts 22 and 24 formed through each module 17 preferably has a flange in which the corresponding flange of a segment 23 of adjacent heat transfer plate module can be connected; preferably, with a seal caught between the flanges. The outer segments 23 of each module 17 can then be attached to a corresponding segment 23 on the outer side of an adjacent module with a joint therebetween using the traction straps 64 shown in Figures 3, 4 and 5, although others may be used. Mechanical joining forms instead of tensile ties. In the embodiment shown in Figures 3, 4 and 5, the modules 17 are held in place by frames or plates 62 of front and rear orientation which are joined by tension rods 64. The surface plate 62 on 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 attached respectively to the inlet nozzles 26 and 28 and output (not shown in Figure 2). The outer segments 23, i.e., the inlet and outlet in the heat transfer back plate at the end 80 of the heat transfer assembly 36, are plugged to close the feed water flow circuit or the transfer backplane Heat is manufactured without the inlet and outlet holes.

In Figure 6 there is illustrated a flow diagram of the primary fluid through the set of heat transfer plates of the embodiments described above having a parallel flow path through the pairs of heat transfer plates 16. The 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 additional segments 23 of the inlet conduit 22 in the corresponding openings in the heat transfer plates 12 and 14 and forms a gas tight seal. fluid in the interconnection. Similarly, a weld bead 68 extends around the additional segments 23 of the outlet conduit 24 at the corresponding openings in the heat transfer plates 12 and 14 and forms a fluid seal at the interconnection. In addition, a circumferential weld 70 extends around the entire circumference of the pair of heat transfer plates 16. As its sample in Figure 7, the primary fluid enters the inlet 72 of the inlet conduit 22 of each pair of plates 16 heat transfer by 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 the heat from the extraction steam and the drainage flow passing through the outside of the heat transfer plate pairs and exits through the outlet 78 of the outlet duct 24 where it joins the upstream flow of primary fluid from other pairs of heat transfer plates that entered through the inlet 76 of the outlet duct in the pair of heat transfer plates 16. Except for the last pair of heat transfer plates 16 at the end 80 (Figure 5) of the set 36 of heat transfer plates, the remainder of the primary fluid entering the inlet 72, which did not flow between the plates 12 and 14 of heat transfer of a certain pair of heat transfer plates 16, exits through the outlet 74 of the inlet conduit to the next pair of heat transfer plates 16. All the primary fluid you pass through to 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 the Figure 6. It is irrelevant if the water flows upward (such as shown in Figure 6), down (as described here) or sideways through the pairs of heat transfer plates 16 as long as the flow extends from the inlet duct 22 to the duct 24 of departure.

Figure 8 is a schematic of an embodiment of a module 17 of heat transfer plates. The module 17 is shown with four pairs of heat transfer plates 16, although as mentioned above the number of pairs of heat transfer plates 16 may vary. The pairs of heat transfer plates 16 have relatively thin heat transfer plates 12 and 14, as compared to plates 82 of the outer support, which are thicker than the pairs of internal heat transfer plates 16. The support plates 82 are referred to as support plates and are longer than the others and extend beyond the others to accept the tension rods shown in Figures 3, 4 and 5, although it should be appreciated that this embodiment is slightly different from the embodiment shown in Figures 3, 4 and 5. However, the way in which the modules secure each other is the same, although it should be appreciated that other means to secure the modules together, for example, continuous threaded rods, bolts, etc., could also be used. The internal heat transfer plates are welded together with the additional segments 23 of the conduit (shown in Figure 4) that descend between them, with the welds extending around the circular openings in the additional segments of the inlet duct 22 and the outlet duct 24 and the outer edges near the circumferential plate welds 70. The joint slots 84 are provided around the openings of the inlet conduit 22 and the outlet conduit 24 in the support plates 82 so that the joints close the openings in the interconnection with the module support plates 82. 17 contiguous.

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 in relation to Figure 8, except that the outer heat transfer plates have a seal retention ring 86 around the openings of the inlet conduit 22 and the outlet conduit 24.

A single support plate is interposed between the modules 17 and the joints in the retaining rings 86 to close the openings 22 and 24 between each support plate and the heat transfer plates. Alternatively, grooves may be provided on one or both sides of the support plates to retain the joints.

A spacer module 88 may be inserted in place of a heat transfer plate pair module 17 to preserve space for a later addition of another heat transfer plate module 17, in case a future upgrade of the exchange is required. where the heat exchanger is installed requires an additional heat transfer capacity within the existing roof. An embodiment of such a spacer module 88 is illustrated in FIG. 10. The spacer module 88 is preferably of the same size as a standard heat transfer plate pair module 17 for the heat exchange unit 10 in which it is placed. It's going to use. The spacer module in this embodiment has two support plates 82 with joint grooves 84, as previously described, which are separated by an upper support 96 and a lower support 98 with a secondary fluid drain 94. It should be appreciated that the upper support 96 and the lower support 98 can (but not necessarily) be part of a continuous support cylinder. The embodiment shown in Figure 10 is intended to be inserted between the heat transfer plate pair modules 17 and has a pipe 90 that is welded around its circumference at each support plate interconnect to form a seal. The pipe 90 forms a portion of the inlet duct 22, carrying the primary fluid between the modules 17 of the pair of heat transfer plates it connects. Similarly, a pipe 92 is sealed to the plates 82 of the support and spans the space therebetween of the spacer module 88 to carry the primary fluid through the outlet conduit 24. If the separator is used at the end of the end 80 of the heat transfer plate assembly 36, in that case the openings in the support plates 82 of the spacer module are not necessary.

Figure 11 illustrates an embodiment of a tension strut arrangement that can be used to join the modules 17 and 88 together. The traction tie 64 is designed to extend between the support plates 82, similar to the spans between the support frames 62 shown in Figure 5. In the embodiment shown in Figure 11, the traction rods 64 have an end with a reduced diameter having a circumferential thread 104. The circumferential thread 104 terminates in a surface of support 106 having a size for splicing with one side of a periphery of a module support plate around an orifice in which the thread 104 has a size to extend through and out of the other side. The other end of the traction tie 64 has an internal thread 100 which is sized to engage with an outer circumferential thread 104 in a contiguous tension stringer 64 that extends through a corresponding hole in an adjoining support plate 82. Preferably, the outer circumference 102 around the end of the tension strut having the internal thread 100 has a square or hexagonal contour in which a torque can be applied immediately.

As previously mentioned, the heat transfer plate assembly 36 has wheels 33 which are mounted on the slide 32 previously described to facilitate maintenance of the heat transfer plate assembly. Maintenance is the same as described for the embodiment illustrated in Figures 1 and 2, except for the improvement of the heat transfer plate assembly, the separator module 88 is removed and an additional heat transfer plate module 17 is dock in place.

Additionally, although the preferred embodiment is described in an application for a feed water heater, the invention can be employed with similar benefits in most other types of heat exchangers. Accordingly, the particular embodiments disclosed herein are intended to be illustrative only and not to limit the scope of the invention to which it is given the full scope of the appended claims and any and all equivalents thereof.

Claims

1. A heat exchanger (10), characterized in that it comprises: an elongate cover (34) of pressure vessel 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), an inlet (42, 44, 46) secondary fluid, a drain outlet (48, 50) and a heat transfer assembly (36) comprising: a primary fluid inlet duct (22) extending within the pressure vessel (34) from the primary fluid inlet (26); a primary fluid outlet conduit (24) extending inside 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 sealed plates (70) around the periphery to define a primary fluid flow channel between a first and a second plate (12) , 14) of heat transfer of each pair, each pair having an inlet opening (72) of heat transfer plates connected directly or indirectly to the primary fluid inlet conduit (22) and an outlet opening (78) of heat transfer plates connected directly or indirectly to the primary fluid outlet conduit; Y wherein the plurality of pairs of heat transfer plates (16) is arranged in modules (17) with at least one of the modules connected in tandem to an adjacent module or the primary fluid inlet or the primary fluid outlet with a mechanical coupling (84) non-destructively removable.

2. The heat exchanger (10) of claim 1, characterized in that at least some of the modules (17) includes a plurality of the pairs of heat transfer plates (16).

3. The heat exchanger (10) of claim 1, characterized in that the service access to the heat transfer assembly is obtained through the removable closure (40).

4. The heat exchanger (10) of claim 3, characterized in that the heat transfer assembly (36) can be removed from the pressure vessel cover (34) when the removable closure (40) is opened.

5. The heat exchanger (10) of claim 4, characterized in that the heat transfer assembly (36) can slide out of the pressure vessel cover (34) when the removable closure (40) is opened.

6. The heat exchanger (10) of claim 1, characterized in that the heat transfer assembly (36) is movable supported on a slide (32) attached to an interior of the pressure vessel (34) so that the transfer assembly of heat can be removed, as a unit, from the pressure vessel through the one end (40) by moving the heat transfer assembly along the slider.

7. The heat exchanger (10) of claim 6, characterized in that the heat transfer assembly (36) is supported on the slide (32) on wheels (33) that roll on the slide.

8. The heat exchanger (10) of claim 1, characterized in that the primary fluid inlet (26) and the primary fluid outlet (28) extend from the removable closure (40).

9. The heat exchanger (10) of claim 1, characterized in that it includes means for expanding the heat transfer capacity of the heat transfer assembly (36).

10. The heat exchanger (10) of claim 9, characterized in that the heat transfer assembly (36) is equipped with a number of extra couplings (60) for attachment to additional pairs of heat transfer plates (16), the couplings being extra-plugged initially and available for a further improvement of the heat transfer capacity of the heat exchanger after the heat exchanger has been put into operation, uncovering at least some of the extra couplings and joining a number of additional pairs of heat transfer plates.

11. The heat exchanger (10) of claim 9, characterized in that the means for expanding the heat transfer capacity of the heat transfer assembly (36) includes a spacer module (88) connected in tandem to the modules (17) of pairs of heat transfer plates.

12. The heat exchanger (10) of claim 1, characterized in that the cover (34) of the pressure vessel has a cylindrical shape with hemispherical ends (40, 38).

13. A cleaning or repair process of the heat exchanger (10) of claim 1, characterized in that it comprises the steps of: accessing the interior of the cover (34) of the pressure vessel; removing at least one pair of heat transfer plates (16) from the heat transfer assembly (36); clean, repair or replace the removed pairs of heat transfer plates (16); reconnect the cleaned, repaired or replaced pairs of the heat transfer plates (16) to the heat transfer assembly (36).

14. The cleaning or repair process of the heat exchanger (10) of claim 13, characterized in that the step of accessing the interior of the cover (34) of the pressure vessel comprises removing the removable closure (40) from the one end or opening a manhole (56) in the cover of the pressure vessel and the step of removing at least a pair of heat transfer plates (16) comprises removing the at least one pair of heat transfer plates from the conduit (22) of primary fluid inlet and the primary fluid outlet conduit (24).

15. A repair, inspection, cleaning or improvement procedure of the heat exchanger (10) as defined in claim 1, characterized in that it comprises the steps of: accessing the interior of the cover (34) of the pressure vessel; Y disconnecting the primary fluid inlet duct (22) and the primary fluid outlet duct (24) from the primary fluid inlet (26) and the primary fluid outlet (28), respectively.

16. The method of claim 15, characterized in that it includes the step of replacing a defective pair of heat transfer plates (16).

17. The method of claim 15, characterized in that it includes 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 improve the heat exchanger.

18. The heat exchanger (10) of claim 1, characterized in that at least some of the modules (17) comprises a plurality of pairs of heat transfer plates (16) with each of the pairs of heat transfer plates within of a module connected together in the tandem array by means of a welded coupling (23).

19. The heat exchanger (10) of claim 1, characterized in that at least some of the modules (17) have a support plate (82) at a first and second end with plates (12, 14) of heat transfer between the same, in which the support plates are thicker than the heat transfer plates.

20. The heat exchanger (10) of claim 1, characterized in that the modules (17) are supported in tandem by tension rods (64).