BR112014016949A2 - HEAT EXCHANGER AND METHODS TO CLEAN OR REPAIR A HEAT EXCHANGER AND TO REPAIR, INSPECT, CLEAN OR IMPROVE A HEAT EXCHANGER - Google Patents

Abstract

HEAT EXCHANGER, AND, METHODS FOR CLEANING OR REPAIRING A HEAT EXCHANGER AND FOR REPAIRING, INSPECTING, CLEANING OR IMPROVING A HEAT EXCHANGER A modular hull and plate heat exchanger in which welded pairs of heat transfer plates are spaced across line (tandem) and coupled in parallel between an inlet and outlet duct to form a heat transfer assembly. The heat transfer assembly is placed in the hull to transfer heat from a secondary fluid to a primary fluid. Modules of one or more of the heat transfer plates are removably connected using gaskets in the inlet and outlet ducts that are connected to a primary fluid inlet and a primary fluid outlet nozzle. The heat transfer set is supported by a structure that rests on an internal rail that is attached to the hull and facilitates the removal of the heat transfer plates. The plate and hull heat exchanger has a removable head integral with the hull to remove the heat transfer assembly for inspection, maintenance and replacement.

Description

“HEAT EXCHANGER, AND, METHODS FOR CLEANING OR REPAIRING A HEAT EXCHANGER AND FOR REPAIRING, INSPECTING, CLEANING OR IMPROVING A HEAT EXCHANGER”: CROSS REFERENCE TO RELATED APPLICATION: [0001] This Order is a partial continuation of the Patent Application US serial number 12 / 432,147, deposited on April 29, 2009.

BACKGROUND

1. Field

[0002] The present invention relates generally to heat exchangers and, more particularly, to modularization for stacked plate heat exchangers.

2. Description of the related technique

[0003] Feed water for steam generators in nuclear power plants is typically preheated before being introduced to the secondary side of the steam generators. Similarly, the feed water is preheated before being introduced into boilers for non-nuclear power plant applications. Feed water heat exchangers are typically used for this purpose. Conventionally, heat exchanger designs are divided into two generic classes: heat exchangers with a plate structure and those with a shell and tube structure. The main difference in the two classes with respect to both construction and heat transfer is that the heat transfer surfaces are mainly plates in one structure and tubes in the other.

[0004] The plate and hull heat exchanger in numerous feed water heater applications employs a horizontal or vertical tubular hull that has hemispherical or flat ends. The interior of the horizontal hull is divided into sections by a tube sheet that is normal to the hull axis. More specifically, at one end of the hull a water chamber section is defined on one side of the tube plate that includes a water inlet chamber that has a water inlet opening and a water outlet chamber that has a water opening. water outlet. In a tube heat exchanger and U-tube hull, the plurality of heat transfer tubes are folded into their intermediate portions in a U-shape and extend from the other side of the tube sheet along the axis of the hull. These tubes are attached to the tube plate at both ends, such that one end of each tube 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 tubes. The heat transfer tubes are supported by a plurality of tube support plates spaced in a suitable step in the longitudinal direction of the tubes. A steam inlet opening and a drain inlet and outlet are formed in the hull, in the portion in which the tubes extend.

[0005] In operation, the feed water coming into the feed water heater from the water inlet chamber flows through the U-shaped heat transfer tubes and absorbs heat from the heating steam that comes into the feed water heater from the steam inlet opening to condense the steam. Condensate is collected at the bottom of the hull and discharged outside via a drain at the bottom of the hull. Thanks to the cylindrical shape of the hull and heat exchange tubes, the structure is well suited as a pressure vessel, and thus tube and hull heat exchangers have been used in extremely high pressure applications.

[0006] The most significant disadvantage of tube and hull heat exchangers is their weight, which is heavy when compared to the surface area of the heat transfer surfaces. Because of this, the tube and shell heat exchangers are usually large in size. It is also difficult to design and manufacture tube and shell heat exchangers when heat transfer, flow characteristics, and expense are taken into account.

[0007] A typical plate heat exchanger is made up of ribbed or grooved plates & rectangular plates that are pressed together against one another by means of extreme plates which, in turn, are fastened to the ends of the plate stack by means of tie rods or tension screws.

The spaces between the plates are closed and sealed with banded seals on their outer circumference, and the seals are also used in the drainage channels. Since the carrying capacity of thin plates is poor, and they are reinforced with grooves that are usually arranged transversely on adjacent plates, in which they also improve the pressure resistance of the structure when the groove ridges are supported by each other . However, the most important aspect is the importance of the heat transfer grooves; the shapes of the grooves and their angle in relation to the flow affect heat transfer and pressure losses. In a conventional plate heat exchanger, a heat supply medium flows into each other space between the plates and a heat receiving medium flows into the remaining spaces. In pairs of alternating plates the flow is conducted between the plates through holes located in the vicinity of the corners of the plates. Each space between the plates in pairs of alternating plates always contains two holes with closed edges and two other holes that function as input and output channels for the space between the plates. Plate heat exchangers are usually constructed of relatively thin plates when a small, lightweight structure is desired. Since the plates can be profiled to any desired shape, it is possible to make the heat transfer exchange properties suitable for almost any type of application. The maximum weakness in conventional plate heat exchangers is the seals that limit the pressure and temperature resistance of the heat exchangers. In several cases, the seals have impaired the possibility of using with corrosive means of heat supply or receiving heat.

[0008] Attempts have been made to improve the construction of: plate heat exchanger by excluding all seals and replacing them with: brazed joints or welded seams. Plate heat exchangers manufactured by brazing or welding usually resemble those equipped with seals. The most significant external difference is the absence of tension screws between the ends. However, the brazed or welded structure makes it difficult, if not impossible, to disassemble without destroying such heat exchangers for cleaning.

[0009] Attempts have been made to combine the advantages of the tube and shell heat exchanger and the plate heat exchanger in heat exchangers, the construction of which partially resembles both of these basic types. Such a solution is disclosed in US Patent 5,088,552, in which circular or polygonal plates are stacked on top of each other to form a stack of plates that is supported by means of end plates.

The stack of plates is surrounded by a hull whose sides are provided with inlet and outlet channels for corresponding flows of heat supply and heat receiving medium. Unlike the conventional plate heat exchanger, all fluid flows into the spaces between the plates are 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 pressures as when using a tube and shell heat exchanger, with the heat transfer properties of a plate heat exchanger.

[00010] The International Publication WO 91/09262 aims to present an improvement on the previous Publication, which more prominently presents typical aspects of both, the plate and shell and tube and shell heat exchangers. The circular plates are brought together in pairs by welding them together through the edges of holes that form an inlet and outlet channel. By welding the pairs of plates manufactured in the above manner together by means of the outer perimeters of the plates, a closed circuit is: achieved for the flow of a heat transfer medium. 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 each other space between the plates by means of a hull surrounding the stack of plates. To prevent runoff from occurring between the stack of plates and the hull, seals are used, which are used primarily as deflectors for the runoff. Obviously, pressure resistance is not required for 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, for example, for cleaning purposes.

[00011] The hull 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 loss of thermal performance. The loss of thermal performance in the feed water system is expensive for nuclear power plants and eventually requires replacement of the hull and tube feed water heater. Another limitation of the tube hull design is that the hull side inspection is typically limited to small manholes and manholes and, as a result, corrosion and erosion damage is difficult to detect. Significant corrosion / erosion has been sustained by internal baffles which can lead to: (1) flow contour and degradation of thermal performance, and (2) pipe wear due to flow-induced vibration. Significant corrosion / erosion has also been observed on the inner hull surface of the hull and tube feed water heater design.

[00012] Therefore, a new feed water heater design is desired for long-term sustainable thermal load, and for long-term improved component integrity in relation to the project. current heater and tube feed water heater. Preferably, long-term sustainable thermal load will be achieved by replacing or: repairing the heat transfer surfaces as necessary, rather than requiring the heat transfer surface to be taken out of service. Additionally, it is desired to be able to increase the heat transfer capacity of the feed water heater to accommodate reclassifications (improvements) of the power plant without replacing the entire feed water heater.

SUMMARY

[00013] The foregoing objectives are achieved by means of a modular plate and hull feed water heater, in which pairs of welded heat transfer plates are placed in a hull to transfer heat from the steam drain flow from extraction for feed water at a nuclear power plant. Heat transfer plate pairs or groups welded or otherwise connected to heat transfer plate pairs, ie 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 duct and an outlet duct that are respectively connected to inlet and outlet water supply nozzles. The inlet and outlet ducts of heat transfer plate pairs form a heat transfer assembly that is preferably supported by a structure that rests on, and is movable along, an internal rail attached to the interior of the hull, which facilitates the removal of heat transfer plates from the hull. The modular plate and hull feed water heater has a removable head integral with the hull for removing heat transfer plates for inspection, repair or replacement. Preferably, the entry and exit locations are sealed up to and extend through the removable head.

. [00014] Preferably the heat exchanger provided here includes a means to increase the heat exchange capacity of the unit over time, to accommodate improvements to the plant in which the heat exchanger is installed. In one embodiment, the inlet and outlet ducts include numerous additional connection points for pairs of heat transfer plates that are initially buffered. In another embodiment, the inlet and outlet ducts can be expanded by connecting additional pairs of heat transfer plates or modules. In the latter embodiment, the heat exchanger may initially be provided with a spacer module that has a relatively negligible heat transfer capacity, which is supported in tandem with the heat transfer plate modules. A heat transfer plate module can later be replaced by 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 or connected pairs of heat transfer plates are detachable for ease of repair and replacement. Preferably, tie rods connect the modules and, in the mode where the inlet and outlet ducts extend between modules, the tie rods provide compressive force for the pressure seals at the interface of the duct segments of the modules that interface to form a watertight seal.

[00015] "- —Preferably the heat transfer set is removed from the hull with the removable head. Alternatively, a visit entry is provided in the hull to provide access to the interior of the hull, to disconnect the water inlet nozzle. of the feed water inlet duct and to disconnect the feed water outlet duct from the feed water outlet nozzle, or both options can be provided.

[00016] In a desirable manner, the modules have support panels at each end, between which the struts extend. The pairs of heat transfer plates are sandwiched between the support panels and, in an À mode, the primary fluid inlet duct and the primary fluid outlet duct 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 to the support panels and adjacent support panels are mechanically connected to each other.

[00017] The invention also provides a method of cleaning or repairing the feed water heater, which includes the steps of: accessing the interior of the pressure vessel hull; removing at least one pair of the heat transfer plates from the heat transfer plate heat transfer assembly; clean, repair or replace the removed pair of heat transfer plates and reconnect the clean, repaired or replaced pair of heat transfer plates to the heat transfer assembly. Preferably the step of accessing the interior of the pressure vessel hull includes removing the detachable head, and the step of removing at least one pair of heat transfer plates comprises removing one pair of heat transfer plates from the inlet duct. feed water and the feed water outlet pipe.

[00018] The invention also includes a method of repairing, inspecting, cleaning or improving the feed water heater, in which the pressure vessel has a detachable head. The method comprises the steps of: removing the detachable head, or otherwise accessing the inside of the pressure vessel hull; and disconnect the feed water inlet and feed water outflow from the feed water inlet and the feed water outlet, respectively, while the heat transfer assembly is in the pressure vessel . This method also 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 has been put into service to improve the feed water heater.

BRIEF DESCRIPTION OF THE DRAWINGS

[00019] Another understanding of the invention can be obtained from the following description of the preferred modalities when read in conjunction with the accompanying drawings, in which:

[00020] The Figure | is an elevation view of the feed water heater of an embodiment of this invention;

[00021] Figure 2 is a top view of the feed water heater shown in Figure 1;

[00022] 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 hull;

[00023] Figure 4 is a perspective view of one of the extreme modules of pairs of heat transfer plates of the modality shown in Figure 3;

[00024] Figure 5 is a perspective view with a portion cut and removed from the heat transfer assembly partially shown in Figures 3 and 4;

[00025] Figure 6 is a diagram of the flow of primary fluid through the modality of the feed water heater illustrated in Figures 3 to 5;

[00026] Figure 7 is a side view of a pair of heat transfer plates;

[00027] Figure 8 is a schematic view of an embodiment of a heat transfer plate module described here below; . [00028] Figure 9 is a schematic view of a second embodiment of a heat transfer plate module described here: below;

[00029] Figure 10 is a sectional view of a spacer module described here below; and

[00030] Figure 11 is a side view partially in section of a tie segment that can be used to couple two heat transfer plate modules.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[00031] Current feed water heater designs employed in nuclear power plants use a shell and tube heat exchanger arrangement. Another generic type of heat exchanger that has been around since 1923 is the plate and skeleton 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 modalities described here provide a plate and hull feed water heater that combines and optimizes the aspects of a plate and skeleton heat exchanger and the traditional shell and tube heat exchanger that is conveniently maintained and can be maintained. easily changed relatively economically to increase its heat transfer capacity, where desired.

[00032] One embodiment of the feed water heater 10 of the inventions claimed hereinafter is illustrated in the elevation view shown in Figure | and in the top view shown in Figure 2. Two heat transfer plates 12 and 14 are welded together to form a pair of welded plates 16 that form a flow path for feed water fluid between them as in a heat exchanger. traditional plate. In one embodiment the pair of heat transfer plates 16 is. removably connected, such as with gaskets 18 and bolted flange joints 20, a and in direct communication with an inlet head tube 22 at one end of the welded heat transfer plate pair 16 and an outlet head tube 24 at the other end of the pair of welded heat transfer plates 16. Numerous of these pairs of welded heat transfer plates 16 are stacked in a spaced tandem arrangement, each coupled between the input head and the output head, to form a set of heat transfer that has a parallel flow path. Such an arrangement is shown in Figure 2. Alternatively, it should be appreciated that a number of the pairs of heat transfer plates 16 can be coupled in series with the ends of the series arrangement removably attached in a similar manner to the head tube. inlet 22 and the outlet head tube 24. In either embodiment, the end ends of the heat transfer plate pairs 16 are connected, either directly or indirectly, to the inlet head tube 22 and the outlet head tube 24. The tube inlet head 22 and outlet head tube 24 are respectively connected to a feed water inlet and a feed water outlet nozzle 26 and 28, preferably using a gasketed screw closure in a similar manner to that described for removably fix the pair of heat transfer plates 16 to the inlet and outlet head tubes 22 and 24, although it should be appreciated that other means of connection removable can be used.

[00033] In the embodiment shown in Figures 1 and 2, the head tubes 22 and 24 are supported by a skeleton structure 30 that rests on an internal track 32 attached to the lower portion of the cylindrical hull 34 that forms a pressure vessel that surrounds the assembly heat transfer plate 36. The rail 32 and wheels 33 on the skeleton structure 30 facilitate the removal of the hull heat transfer plate assembly for repair, cleaning or. improvement. In one embodiment, the hull 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 cylindrical hull 34, hemispherical end 38, and removable head 40. However, it should be appreciated that the ends need not be hemispherical to take advantage of this invention, although hemispherical ends are preferable for high pressure applications. The removable head 40 has the feed water inlet nozzle 26 and the feed water outlet nozzle 28 extending through it, as shown in Figures | and 2. Alternatively, hemispherical end 38 can be constructed to be removable instead of head 40, or pumps can be connected by flange connections bolted to hull 34 for added flexibility in gaining access to the interior of hull 34 to maintain the assembly heat transfer plate 36. hull 34 is also equipped with an extraction steam inlet 42, drain inlets 44 and 46 and drain outlets 48 and 50.

[00034] During operation, the feed water introduced passes through the inlet nozzle 26, the inlet head tube 22, the pairs of welded heat transfer plates 16 where it is heated by the drain and extraction steam flow, from the outlet head tube 24 and outlet nozzle 28. The extraction steam when entering the feed water heater through the extraction steam inlet 42 is distributed by the steam sacrifice plate 52 and passes through the upper hull region where it mixes with the drain flow that enters from the drain inlet nozzles 44 and 46. The extraction steam and drain flow then pass between the welded pairs of heat transfer plate 16 where it is cooled by feed water and condenses to the lower hull region where it exits through drain outlet nozzles 48 and 50.

: [00035] During a plant shutdown, an inspection of the heat transfer plates and internal hull surface can be performed: using the following steps. First, the hull end 38 is bolted to the flange 54 and removed. The head tubes 22 and 24 can then be disconnected from the inlet and outlet nozzles 26 and 28. A manhole port 56 on the head 40 can be used to gain access to the connection between the inlet and outlet head tubes 22 and 24 of the nozzles. inlet and outlet 26 and 28. Alternatively, when the head 40 is removed on the flange 58 the head 40 can be moved outward with the heat transfer assembly 36 sliding on the rail 32, so that access can be gained for the connection between inlet and outlet heads 22 and 24 and feed water inlet and outlet nozzles 26 and 28. Spool tubing (not shown) will need to be removed from inlet and outlet nozzles 26 and 28 before moving head 40. Then the heat transfer plate assembly 36 can be moved as a unit along the rails 32 located at the bottom of hull 34, to a point where the individual heat transfer plates 12 and 14, and the interior of hull 34 can be inspected for harm. The pairs of individual heat transfer plates 16 can then be cleaned or, if necessary, repaired or replaced. If repair or replacement is required, the pair of heat transfer plates 16 that need attention can be screwed from the inlet head tube 22 and the outlet head tube 24 and replaced with a new or repaired pair of heat transfer plates 16 screwed in place. The outlet head tube 24 and the entry head tube 22 are also provided with one or more additional openings 60, which are initially sealed by plugs. These additional openings can be unsealed to accommodate additional heat transfer plate pairs 16 if improvement in the future is desirable.

[00036] The removable plate design allows replacement of the heat transfer surface and mass production of plates. heat transfer and gaskets result in a relatively low cost for critical spare parts. Employing this project makes it possible to increase the! number of plates and thus the heat transfer area to accommodate energy improvements and provides improved hull side inspection.

[00037] Although specific modalities of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to these details could be developed in the light of the global teachings of disclosure. For example, although separate inlet and outlet head tubes, or conduits, are shown in the manner illustrated in Figures 1 and 2, any other structure that performs its described function can also be used without departing from the spirit of this invention. For example, the mode of the heat transfer set 36 shown in Figures 3, 4 and 5 shows segments of the inlet and outlet ducts 22 and 24 as integral parts of the pairs of heat transfer plates 16. In Figures 3, 4 and 5 components corresponding to those shown in the Figures | and 2 receive equal 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 of a number of pairs of spaced tandem heat transfer plates 16 which are connected together as an integral unit. Each of the modules 17 shown in Figures 3, 4 and 5 has approximately 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 consequence that the more pairs of heat transfer plates 16 for a module 17 the more expensive the module will be to be replaced. Alternatively, the more modules there are, the more will be spent on gaskets' and closing equipment. An optimal range of the number of boards per module should be determined on the basis of a specific application based on: economic considerations. Also the number of modules 17 in the heat transfer set 36 can vary depending on the number of pairs of heat transfer plates 16 per module, and the heat transfer requirements of the application in which the heat exchanger is being employed.

[00038] In the embodiment shown in Figures 3, 4 and 5, the outer surface, that is, the front and rear of each pair of heat transfer plates 16 has two openings on each side, with the corresponding openings substantially aligned one with another, and to which incremental segments 23 of the inlet and outlet ducts 22 and 24 are connected, such as by welding, brazing or any other suitable connection that forms a durable, substantially rigid joint, which is substantially impermeable to the fluids flowing into the and around the inlet and outlet ducts 22 and 24 in the area between the pairs of heat transfer plates 16. The incremental segments of the inlet and outlet ducts 22 and 24 that pass between the pairs of heat transfer plates 16 and the outer surface of] pairs of adjacent heat transfer plates 16 provide a flow path between the pairs of heat transfer plates 16 for the extraction steam and flow the drain pass. At the outer end of the segments 23 of the inlet and outlet ducts 22 and 24 formed through each module 17, it preferably has 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 in each module 17 can then be attached to a corresponding segment 23 on the outer side of an adjacent module with a gasket in between using struts 64 shown in Figures 3, 4 and 5, although other forms of mechanical connection can be used in place of risers. In the modality shown in Figures 3.4 and 5, modules 17 are held in position by front and rear face structures or plates 62: which are brought together by tie rods 64. Face plate 62 in front of the heat transfer plate assembly has openings for the inlet and outlet ducts 22 and 24 so that the flanges on the outer segments 23 can be attached respectively to the inlet and outlet nozzles 26 and 28 shown in Figure 2. The outer segments 23, that is, both inlet and heat outlet 36 are plugged to close the feed water drain loop or the rear heat transfer plate is made without the inlet and outlet holes.

[00039] A flow diagram of the primary fluid through the heat transfer plate assembly of the modalities described above which has a parallel flow path through the heat transfer plate pairs 16 is illustrated in Figure 6. Figure 7 shows the construction of pairs of heat transfer plates. As shown in Figure 7, a weld bead 66 extends around each of the incremental segments 23 of the inlet conduit 22 in the corresponding openings in the heat transfer plates 12 and 14 and forms a fluid tight seal at the interface. Similarly, a weld bead 68 extends around the incremental segments 23 of the outlet conduit 24 in the corresponding openings in the heat transfer plates 12 and 14 and forms a fluid tight seal at the interface. In addition, a waist weld 70 extends around the entire circumference of the pair of heat transfer plates 16. As shown in Figure 7, the primary fluid penetrates inlet 72 of the inlet conduit 22 of each pair of plates heat transfer 16 by connecting it to adjacent pairs or support plates. A portion of the fluid flows down between the heat transfer plates 12, 14 where it absorbs heat from the extraction vapor and drain flow that passes over the outside of the pairs of. heat transfer plates, and exits at outlet 78 to outlet conduit 24 where it joins with the primary fluid upstream flow from It is other pairs of heat transfer plates that entered through the outlet conduit inlet 76 for 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 heat transfer plate assembly 36, the remainder of the primary fluid entering the inlet 72 that does not flow between the heat transfer plates 12 and 14 of a given pair of heat transfer plates 16 exits through the inlet conduit outlet 74 to the next pair of heat transfer plates 16. All the primary fluid running through 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 Fi girl

6. It is irrelevant whether the water drains upwards as shown in Figure 6 or downwards 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 outlet duct 24.

[00040] Figure 8 is a schematic of a modality of a heat transfer plate module 17. Module 17 is shown with four pairs of heat transfer plate 16, although as described above, the number of pairs of heat transfer plate 16 may vary. The heat transfer plate pairs 16 have relatively thin heat transfer plates 12 and 14 when 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 after the others to accommodate the ties shown in Figures 3, 4 and 5, although it should be appreciated that this modality is slightly different than the modality shown in Figures 3 4 and 5. However, the way in which the modules are attached to each other is the same, although it should be appreciated that other means of securing the modules together, for example, continuous threaded rods, screws, etc., could also be used. The inner heat transfer plates are welded together with the incremental duct segments 23 shown in Figure 4 extending between them with the weld extending around the circular openings in the incremental segments of the inlet duct 22 and outlet duct 24 and the outer edges, by means of circumferential plate welds 70. Gasket grooves 84 are provided around openings in the inlet conduit 22 and outlet conduit 24 in the support plates 82 for gaskets, to seal the openings in the interface with support plates corresponding 82 of adjacent modules 17.

[00041] 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 respect to Figure 8, except that the heat transfer plates exteriors have a gasket retaining ring 86 around the openings for inlet conduit 22 and outlet conduit 24. A single support plate is interposed between modules 17 and gaskets on retainer rings 86 seal openings 22 and 24 between each support plate and the heat transfer plates. Alternatively, grooves can be provided on one or both sides of the support plates to retain the gaskets.

[00042] A spacer module 88 can be inserted in place of a heat transfer plate pair module 17 to preserve space for the latest addition of another heat transfer plate pair module 17 in the event of a future plant improvement in which the heat exchanger is installed requires additional heat transfer capability within the existing hull. One embodiment of such a spacer module 88 is illustrated in Figure 10. The spacer module 88 is preferably of the same dimension as Y the 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 slots 84 as described above, which 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 the support lower 96 may, but need not, be part of a continuous support cylinder. The embodiment shown in Figure 10 is designed to be inserted between the heat transfer plate pair modules 17 in a tube 90 which is welded around its circumference at each support plate interface to form an airtight seal. The tube 90 forms the portion of the inlet conduit 22 that carries the primary fluid between the heat transfer plate pair modules 17 that it connects. Similarly, a tube 92 is sealed to and covers the space between the support plates 82 of the spacer module 88 to load the primary fluid through outlet conduit 24. If the spacer is used at the end of the end 80 of the transfer plate assembly of heat 36, then the openings in the spacer module support plates 82 are unnecessary.

[00043] Figure 11 illustrates a modality of a tie arrangement that can be used to bring modules 17 and 88 together. The riser 64 is designed to extend between support plates 82 similar to the extensions between support structures 62 shown in Figure 5. In the embodiment shown in Figure 11 the risers 64 have a reduced diameter end that has a circumferential thread 104. The circumferential thread 104 ends at a support surface 106 which is dimensioned to touch one side of a periphery of a module support plate around a hole, in which the thread 104 is dimensioned to extend through and out the other side. The other end of rod 64 has an internal thread 100 which is sized to correspond with an outer circumferential thread 84 in an adjacent rod 64 which is extended through a corresponding hole in an adjacent support plate 82. Preferably, the outer circumference 102 around of the end of the tie that has the internal thread 100 has a: square or hexagonal contour on which a torque can be easily applied.

[00044] As mentioned earlier, the heat transfer plate assembly 36 has wheels 33 that mount on the rail 32, described earlier, to facilitate maintenance of the heat transfer plate assembly. Maintenance is the same as described for the modality illustrated in Figures | and 2, except that to improve the heat transfer plate assembly, spacer module 88 is removed and an additional heat transfer plate module 17 is coupled in place.

[00045] 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. Consequently, the particular modalities disclosed are meant to be only illustrative and not limiting as to the scope of the invention, which must be provided must receive the full scope of the attached claims and any of their equivalents.

Claims (20)

1. Heat exchanger (10), characterized by the fact that it comprises:: an elongated pressure vessel hull (34) that has an axial dimension with a removable closure (40) at one end of the axial dimension, a fluid inlet primary (26) a primary fluid outlet (28), a secondary fluid inlet (42, 44, 46) a drain outlet (48, 50) a heat transfer assembly (36) comprising: an inlet conduit primary fluid (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 pair of sealed plates (70) around the periphery to define a primary fluid flow channel between a first and a second heat transfer plate heat (12, 14) of each pair, with each pair having a heat transfer plate inlet opening (22) connected either directly or indirectly to the primary fluid inlet conduit (22) and a heat plate outlet opening heat transfer (78) connected either directly or indirectly to the primary fluid outlet conduit; and in which, the plurality of pairs of heat transfer plates (16) are arranged in modules (17) with at least one of the modules connected in tandem with an adjacent module or the primary fluid inlet or the primary fluid outlet with a non-destructively removable mechanical coupling (84). Heat exchanger (10) according to claim 1, characterized by the fact that at least some of the modules (17) include a plurality of pairs of heat transfer plates (16). Heat exchanger (10) according to claim 1,; characterized by the fact that the service access for the heat transfer set is obtained through the removable lock (40). | Heat exchanger (10) according to claim 3, characterized in that the heat transfer assembly (36) is removable from the pressure vessel hull (34) when the removable latch (40) is open. Heat exchanger (10) according to claim 4, characterized in that the heat transfer assembly (36) is slidable out of the pressure vessel hull (34) when the removable latch (40) is open . 6. Heat exchanger (10) according to claim |, characterized in that the heat transfer assembly (36) is mobilely supported on a rail (32) attached to an interior of the pressure vessel (34) so that the heat transfer assembly can be removed as a unit from the pressure vessel via one end (40) by moving the heat transfer assembly along the rail. Heat exchanger (10) according to claim 6, characterized in that the heat transfer assembly (36) is supported on the rail (32) on wheels (33) that mount on the rail. Heat exchanger (10) according to claim 1, characterized in that the primary fluid inlet (26) and the primary fluid outlet (28) extend from the removable closure (40). Heat exchanger (10) according to claim 1, characterized in that it includes a device for expanding the heat transfer capacity of the heat transfer assembly (36). 10. Heat exchanger (10) according to claim 9, characterized by the fact that the heat transfer assembly (36) is equipped with a number of extra couplings (60) for connection to additional pairs of heat transfer plates (16), the extra couplings are 'initially buffered and are available for further improvement of the heat transfer capacity of the heat exchanger after the À heat exchanger has been put into operation, removing at least some of the extra couplings and connecting a number of additional pairs of heat transfer plates. Heat exchanger (10) according to claim 9, characterized in that the device for expanding the heat transfer capacity of the heat transfer assembly (36) includes a spacer module (88) connected in tandem with the modules of pairs of heat transfer plates (17). Heat exchanger (10) according to claim 1, characterized in that the pressure vessel hull (34) is a cylindrical shape with hemispherical ends (40, 38). 13. Method for cleaning or repairing a heat exchanger (10) according to claim 1, characterized by the fact that it comprises the steps of: accessing the interior of the pressure vessel hull (34); removing at least one pair of the 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 heat transfer plates (16) to the heat transfer assembly (36). Method for cleaning or repairing a heat exchanger (10) of claim 13, characterized in that the step of accessing the interior of the pressure vessel hull (34) comprises or removes the removable closure (40) from one end or opening a manhole (56) in the pressure vessel hull, and the step of removing at least a pair of heat transfer plates (16) comprises removing at least a pair of: plates of heat transfer from the primary fluid inlet conduit (22) and the primary fluid outflow conduit (24). ' 15. Method for repairing, inspecting, cleaning or improving a heat exchanger (10) according to claim 1, characterized by the fact that it comprises the steps of: accessing the interior of the pressure vessel hull (34); and 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. 16. Method according to claim 15, characterized in that it includes the step of replacing a defective pair of heat transfer plates (16). 17. Method according to 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 put into operation to improve the heat exchanger. 18. Heat exchanger (10) according to claim 1, characterized in that at least some of the modules (17) comprise a plurality of pairs of heat transfer plates (16) with each of the pairs of transfer plates of heat inside a module connected together in the system, also through a welded coupling (23). 19. Heat exchanger (10) according to claim 1, characterized in that at least some of the modules (17) have a support plate (82) on a first and a second end, with the ss heat transfer plates (12, 14) between them, in which the support plates are thicker than the heat transfer plates. Heat exchanger (10) according to claim 1,. characterized by the fact that the modules (17) are supported in tandem by tie rods (64). : 125 vs 8 gs 9 £ € ££: ££ [D EN EN Ss * E: Tm: laugh | 8 £ CC À vs E es e ne gs: 9 e se vs € "Old | | 81 91 91 91 91 [E o o a finger SS 82: TT Tr A 9L R = pl oz o9 A a aa ad 8 £ - Ev E) oz o gl E e de : E HI vo Dá el: dd ANNA ES AN dA ANNAN: A A aa a Ata te Na Sd LL gar Pã à Ea FIG. 4 S ze: Í A PM à: GL 2 2 AT TA A Ny 9 DG De &) Di 7 Gp HA Q DR Á y NS 21 E jo O A A: 7 EX & 7 O à | A 2 NS | (AA: |: VS 2 o E Ns SE 2280] E do do: E AN Z ll (7 Exit OS À (7 A Ô NAN / S dd 22 and A Ny A o o) o and VA RA GG a dd A 2 RO 2 n 2 A DA S: o 7 Ea and $ A vz <<. ((Z. | = (= E A 8 GHZ, Healthy (/ 22 EE ÃZ, RA aa0a (7 2 o FA Y NE = o 2 DA A CG: e 7 and TAZ, 4 RAN - and Ze A FG, 008%, 2 frog 02 o) p << o A do à 9> ((/ 29808> o Ú 2224]> 4 DDS 02 >> ”- ú 22 pg>: SS DD (7 O. A. = A: = (o = ã (q.: E ([o = =: S = Sea A <> Y O: 24 2. Pp: ”CNES o a OJ to; - ALLE LL Ea aa O CO A o) AND FIG. 6 paro 70 SIA 14 24 78 76 68 EO: EE: 7 74 FIG. 7 7th í 84 dation, q 2 66> 7 66 fem 7 EE PG FA O G pe F q 2 68 68 81 E duos 82 82. 2 22 86 and ÇEe í 86 FIG. 9 is rss: ”Z: o Z Za Hd INSSSSSSTESTSS SS and Z Za FP 7 Ô ox 92 ão Tr a to 82 À A P 82 94 G 7 FA 98 FIG. 10 64 104 102 Ú: / | —100 106 FIG. 11