KR20140061306A - Steam generator tube lane flow buffer - Google Patents

Abstract

Having a diameter substantially equal to the diameter of the heat exchange tubes in the tube bundle, for buffering the flow from the heat exchange tubes in the tube lanes to weaken the turbulent forces on the first several rows of heat exchange tubes adjacent the tube lanes, A tube end shell steam generator is disposed on both sides of the tube lane.

Description

STEAM GENERATOR TUBE LANE FLOW BUFFER [0002]

Cross reference of related application

This application claims priority to Provisional Application No. 61 / 471,328, filed April 4, 2011, entitled " Steam Generator Tube Lane Flow Buffer. &Quot;

The present invention relates generally to a U-tube and shell steam generator, and more particularly to a U-tube and shell steam generator for buffering a heat exchange tube from a high velocity flow of circulating fluid and feed water in a tube lane, To the same steam generator.

The pressurized water reactor steam generator includes a vertically oriented shell, a plurality of U-shaped tubes disposed within the shell to form a tube bundle, a tube sheet for supporting the tubes at both ends of the U-shaped bend, A partition plate, and a channel head forming a primary fluid inlet header at one end of the tube bundle and a primary fluid outlet header at the other end of the tube bundle. The primary fluid inlet nozzle is in fluid communication with the primary fluid inlet header and the primary fluid outlet nozzle is in fluid communication with the primary fluid outlet header. The steam generator secondary includes a wrapper disposed between the tube bundle and the shell to form an annular chamber comprised of a shell on the outside and a wrapper on the inside, and a feedwater ring disposed above the U-shaped bend of the tube bundle.

The primary fluid heated by the circulation through the reactor flows into the steam generator through the primary fluid inflow nozzle. The primary fluid flows from the primary fluid inlet nozzle, through the primary fluid inlet header, through the U-shaped tube bundle, to the exterior of the primary fluid outlet header, and through the primary fluid outlet nozzle to the remainder of the reactor coolant system Guidance. At the same time, the feed water is supplied to the side of the steam generator which forms an interface with the outside of the tube bundle in the secondary side of the steam generator, i.e., above the tube sheet, through the feed water nozzle connected to the feed water ring inside the steam generator . In one embodiment, the feed water is mixed with the water returning from the water separator as soon as it enters the steam generator. This mixture, referred to as downcomer flow, is introduced into the shell until the tube sheet located at the bottom of the annular chamber changes the direction in which the water travels to the inside of the wrapper in a heat transfer relationship with the outside of the U- And is guided downwardly of the adjacent annular chamber. While water circulates in a heat transfer relationship with the tube bundle, the heat is transferred from the primary fluid in the tube to the water around the tube, thereby converting a portion of the water around the tube to steam. To distinguish this steam / water mixture from a single phase downcomerflow, the fluid flow around the tube is called tube bundle flow. The steam is then guided through a plurality of water separators that ascend and separate the water entrained from the steam and then steam is discharged from the steam generator and circulated through the turbine to generate electricity in a manner known in the art .

Since the primary fluid contains radioactive material and is isolated from the feedwater only by the U-shaped tube wall, the U-shaped tube wall forms part of the primary boundary for isolating such radioactive material. Therefore, by holding the U-shaped tube well so that a rupture that may cause undesirable results to flow from the primary fluid to the secondary side does not occur in the U-shaped tube, the U- It is important to do. The support for the U-shaped tube is achieved by a plurality of longitudinally spaced transverse tube support plates which are axially positioned along the height of the tube bundle and through which the end of the heat exchange tube extends And is fixed to the tube sheet. Typically, the holes in the backing plate have a land that supports the heat exchange tubes in a transverse direction and a lobe between the tubes that allows passage of the tube bundle flow and steam. However, the possibility of tube abrasion at the tube support plate of the steam generator unit and fouling of the tube and / or tube support plate after a long period of operation has been reported. The maximum indication has a depth of 28%. Of 79 total indications reported by one steam generator 58, 73% of the total number of indications occurs in columns 1 to 5 of the heat exchange tubes. Of these 79 total indications, 34% occur in one row of tubes. Most of these occur at higher tube support plate heights, where damping is reduced and speed is increased. These rows are adjacent to the tube lane region centered between the hot leg and the cold leg of the tube, so that they may experience blows caused by turbulence. It is well known that the forces of turbulence are rapidly attenuated within the first few rows of heat exchange tubes and the data demonstrate the presence of this phenomenon by the distribution of wear indications.

It is therefore an object of the present invention to reduce the wear of the heat exchange tubes at the tube support plates adjacent to the tube lanes in the tube end shell steam generator.

Furthermore, it is an object of the present invention to reduce the wear of the heat exchange tubes within the vicinity of the tube support plate adjacent to the tube lane without reducing the efficiency of the steam generator.

It is also an object of the present invention to reduce the wear of the heat exchange tubes within the first few rows of heat exchange tubes adjacent to the tube lanes within the vicinity of the upper tube support plates.

This and other objects are achieved by a tube end shell steam generator having a fluid header with one end closed by a first side of the tubesheet and separated by an inflow plenum and an outlet plenum by a partition plate . The steam generator has a plurality of U-shaped hollow heat exchange tubes each having a cold leg and a hot leg, the cold leg and the hot leg being connected by U-shaped bent portions at one end, The inlet portions of the hot legs extend through the tubesheet to open into the inlet plenum and the outlet portions of the cold legs extend into the outlet sheet and open into the outlet plenum. The steam generator further comprises a tube lane at the shell side of the tube sheet opposite the first side, the tube lane being centered between the hot leg and the cold leg of the plurality of U-shaped hollow heat exchange tubes, Legs and cold legs, respectively. An improvement is achieved with a plurality of elongated buffer rods extending in the tube lane and on both sides of the tube lane in a direction substantially perpendicular to the tube sheet with the elements described above. The buffer load is supported in a manner not in communication with the primary fluid in the primary fluid header.

In one embodiment, the maximum outer diameter of the buffer rod is substantially the same as the outer diameter of the U-shaped hollow heat exchange tube. In another embodiment, the buffer rod has an axial length and the outer diameter of the buffer rod varies along the axial length. Preferably, the axial lengths are changed stepwise, and the steam generators comprise a plurality of spaced apart tube support plates, each of which is stacked vertically side by side and transversely to the axial length of the buffer rod, The diameter is a tube support plate from which the buffer rod extends, and is located on a tube support plate that is furthest away from the tube sheet.

In another embodiment, the buffer rod is connected to the tube sheet at one end. Preferably, the buffer rod extends into the tube sheet without extending through the tube sheet.

In a further embodiment, the steam generator comprises a plurality of spaced apart, longitudinally aligned, longitudinally spaced, longitudinally spaced, longitudinally extending, A tube support plate is further included wherein the hot legs and the cold legs pass through the plurality of spaced apart tube support plates. The buffer load extends between at least a portion of the tube support plate. Preferably, the buffer rod extends through substantially all of the tube support plates from the tubesheet.

In one embodiment, at least a portion of the axial length of the buffer rod is hollow and the hollow portion of the buffer rod has a wall thickness that is at least equal to or greater than the wall thickness of the plurality of U-shaped hollow heat exchange tubes. In yet another embodiment, the buffer load is solid.

Optionally, the buffer load may start to extend from a height above the tubesheet, and the buffer rod may also be terminated below the uppermost tube support plate. In addition, the buffer rod may extend through the holes in at least two adjacent support plates, and at least some of the holes through which the buffer rod in one of the two adjacent support plates pass, Is offset from a corresponding hole in the tube support plate. Preferably, the offset is at most about 4 mm.

A further understanding of the invention may be obtained from the following description of a preferred embodiment with reference to the attached drawings.

1 is a partial cutaway perspective view of a vertical tube end shell steam generator;
Figure 2 is a plan view showing a portion of one of the tube support plates around the tube lane area with the buffer rod inserted through a flow hole extending on either side of the tube lane;
3 is a schematic side view of a partial section of the lower portion of the steam generator showing the inventive buffer rod extending through the upper tube support plate from the tube sheet;
Figure 4 is a schematic partial cross-sectional view of the lower portion of the steam generator showing the buffer rod extending from above the tube sheet through the plurality of tube support plates to the underside of most of the upper tube support plates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIG. 1 illustrates the use of a plurality of U-shaped tubes forming a tube bundle 12 that provides the heating surface required for transferring heat to a secondary fluid that evaporates or boils from the primary fluid Steam or steam generator (10). The steam generator 10 includes a vessel having a vertically oriented tubular shell portion 14, a top enclosure or dish-like head 16 surrounding the top portion and a generally hemispherical channel head 18 surrounding the bottom portion . The lower shell portion 14 has a smaller diameter than the upper shell portion 15 and the frustoconical transition portion 20 connects the upper shell portion and the lower shell portion. The tube sheet 22 has a plurality of holes 24 attached to the channel head 18 and arranged to receive both ends of the U-shaped tube 13. The partition plate 26 is centrally disposed within the channel head 18 to divide the channel head into two compartments 28 and 30 which act as a header for the tube bundle 12 . The compartment 30 is a primary fluid inlet compartment and has a primary fluid inlet nozzle 32 in fluid communication therewith. The compartment 28 is a primary fluid outflow compartment and has a primary fluid outflow nozzle 34 in fluid communication therewith. Therefore, the primary fluid, that is, the reactor coolant flowing into the fluid compartment 30, flows through the tube bundle 12 and is discharged to the outside through the outflow nozzle 34.

The tube bundles 12 are surrounded by a wrapper 36 and cone portions 14 and 20, respectively, which form an annular passage 38 between the wrapper 36 and the shell. The upper portion of the wrapper 36 is covered by a lower deck plate 40 that includes a plurality of openings 42 in fluid communication with a plurality of large tubes 44. The swirl vane 46 is connected to the large tube 44 so that when the steam flowing through the large tube 44 flows through the primary centrifuge, the steam is rotated and a part of the water contained in the steam is adjusted by the centrifugal force, . The water separated from the steam in the primary separator is returned to the upper surface of the lower deck plate (40). After flowing through the centrifugal separator, the steam passes through the secondary separator 48 and reaches the steam outlet nozzle 50 located centrally in the dish head 16.

The feed water inflow structure of this generator includes a feed water inflow nozzle 52 having a generally horizontal portion called a feed ring 54 and a plurality of discharge nozzles 56 located above the feed ring. The feed water supplied through the feed water inflow nozzle 52 passes through the feed water ring 54 and then through the discharge nozzle 56 and is mixed with water separated from the steam in one prior art embodiment And recirculated. Next, the mixture flows downward from the lower deck plate (40) into the annular downcomer passage (38). The water then flows into the tube bundle 12 from the lower portion of the wrapper 36 and flows upward between the tube bundles and is heated to produce steam.

Due to the boiling action of the water and the flow of fluid through the heat exchange tube, fluid elastic excitation can occur which can cause vibration of the heat exchange tube which can promote wear of the heat exchange tube. A plurality of longitudinally spaced heat exchange tube support plates 58 are positioned transverse to the axial dimension of the shell 14 and have holes through which the heat exchange tubes extend. The holes are specially designed to support the heat exchange tubes and provide openings for feed water and recycle steam passing through the heat exchange tubes. Figure 2 shows a top view of a portion of the heat exchange tube support plate in the region of the tube lane extending downwardly of the U-shaped bend region of the heat exchange tube. Heat transfer to the tube 13 in several of the first, second and third rows of tube holes 64 is described. It is to be understood that the heat exchange tubes 13 are shown in several, but not all, broaching holes 64, but extend through substantially each of the shown broaching holes. The tube 13 is supported on the land 70 of the hole 64 and the coolant flow is guided around the tube through the lobe 66. The columns 1, 2 and 3 are most susceptible to the effects of vibration and wear caused by turbulence caused by lateral flow in the central tube lane 60. Therefore, the heat exchange tubes 13 in columns 1, 2 and 3 are subjected to a blow which is strengthened and induced by turbulence. The heat exchange tube wear data collected from the working generator certifies that the turbulence forces are rapidly attenuated within the first few rows of heat exchange tubes 13. [ A flow aperture 74, which is closer to the centerline of the tube support plate, limits the flow of water through the tube lane region of the tube bundle and distributes the flow prior to entry into the U-shaped transverse flow region. A flow slot is used instead of the flow hole 74 for the lower tube support plate.

Here, the elongated buffer rod 62 extends through the flow holes 74 on both sides of the tube lane 60, and the first, second, and third rows of the heat exchange tubes 13 extend through the flow holes 74 And substantially does not receive a blow by the water passage in the direction crossing the flow hole 74. [ Thus, the tube-lane flow buffer 62 is positioned between the areas without flow tubes along the tube lane 60, and when flow through the tube lanes passes through each successive tube support plate 58 and / Which is generated when the tubular support plate 58 collides with the continuous tube support plate 58 of the tubular support plate 58. The buffer rod 62 may be laterally supported by a rounded hole such as the flow hole 74 or a broached hole such as a tube support hole 64 and may be made of stainless steel or other corrosion resistant / . In a preferred embodiment, the flow buffer rod 62 extends from the secondary side of the tube sheet 22 to a range exceeding a few inches of the uppermost tube support plate 68. 3 schematically shows a cross-sectional view of the lower portion of the steam generator including tube bundles 12, in which only a representative number of U-shaped tubes are shown. In this embodiment, eight support plates 58 are arranged vertically side by side along the axis of the generator. The tube support plate is laterally supported by a plurality of support rods 72 whose lower ends are attached to the tube sheet 22 by screwing them into threaded recesses within the upper surface of the weld or tube sheet. The support rods extend from the tube sheet through the round openings in each of the tube support plates 58 so as to protrude a short distance above the upper support plate 68. Although only two support rods 72 are shown in FIG. 3 for the sake of illustration, a substantial number of additions between the hot legs and cold legs of the heat exchange tubes 13 to actually support the lateral support of the tube support plate Is provided. Similarly, in this preferred embodiment, the buffer rod 62 extends from the recess in the top surface of the tube sheet 22, where the buffer rod 62 can be similarly attached and the upper tube support plate 68 It is possible to extend by a few inches to the upper side of FIG. Preferably, the buffer rod 62 is fabricated to the same diameter as the heat exchange tube 13, so that it does not interfere with maintenance operations such as bundle inspection or sludge lancing, There is no difference. The decrease in the width of the tube lane due to the presence of the buffer load does not affect the water retention since the width of the tube lane is kept larger than the width of the steam generator unit in which the width of the tube lane is the most restricted.

Figure 4 shows a schematic view of the steam generator already shown in Figure 3 in which the buffer rod 62 has a height from the height above the tubesheet 22, in this example above the lowermost heat exchange tube support plate 76, And extends to a height just above the heat exchange tube support plate 58 below the side heat exchange support plate 68. The buffer load 62 also has a stepped diameter with a larger diameter that extends through the upper heat exchange tube support plate 58 to provide better protection against striking in the region of greater turbulence. . Further, the buffer rod 62 may have a thicker wall than the heat exchange tube wall, as shown in the upper range of the buffer rod shown in Fig. 4, or may be solid as shown in Fig. In addition, the position of the buffer rod and the heat exchange tube support hole centerline of the alternately disposed tube support plate can be offset by about 4 mm to further control the vibration of both the heat exchange tube 13 as well as the buffer rod 62. This provides a preload of hardness that helps to eliminate impact wear with greater wear rate than corrosion wear.

Although specific embodiments of the invention have been described in detail above, those skilled in the art will appreciate that various modifications and alterations may be made to these details in light of the overall teachings of the disclosure. Accordingly, the specific embodiments disclosed are illustrative only and not meant to limit the scope of the invention, which is provided as a full range of equivalents to the appended claims and any equivalents thereof or their equivalents.

Claims (15)

A tube and shell steam generator for transferring heat from a primary fluid to a secondary fluid, the tube and shell steam generator comprising:
A primary fluid header at one end closed by a first side of the tubesheet and separated by an inlet plenum and an outlet plenum by a partition plate;
A plurality of U-shaped hollow heat exchange tubes each having a cold leg and a hot leg, wherein the cold leg and the hot leg are connected at one end by U-shaped bent portions, and at the other end, Wherein the inlet portion of the hot leg extends through the tube sheet to open into the inlet plenum and the outlet portion of the cold leg extends into the tube sheet to open into the outlet plenum, U-shaped hollow heat exchange tubes;
A tube lane at the shell side of the tube sheet opposite the first side, the tube lane being centered between a hot leg and a cold leg of the plurality of U-shaped hollow heat exchange tubes, the hot leg and the cold leg Each having a side adjacent to the tube lane; And
A plurality of elongated buffer rods extending in the tube lane and on both sides of the tube lane in a direction substantially perpendicular to the tube sheet and not in communication with the primary fluid in the primary fluid header doing
Tube end shell steam generator. The method according to claim 1,
The maximum outer diameter of the buffer rod is substantially the same as the outer diameter of the U-shaped hollow heat exchange tube
Tube end shell steam generator. 3. The method of claim 2,
Wherein the buffer rod has an axial length and the outer diameter of the buffer rod varies along an axial length of the buffer rod
Tube end shell steam generator. The method of claim 3,
The axial length is varied stepwise
Tube end shell steam generator. 5. The method of claim 4,
A plurality of spaced apart tube support plates stacked side by side vertically and positioned respectively transverse to the axial length of the buffer rod,
Wherein the maximum diameter of the buffer rod is a tube support plate on which the buffer rod extends and which is located on a tube support plate spaced farthest from the tube sheet
Tube end shell steam generator. The method according to claim 1,
The buffer rod is connected at one end to the tube sheet
Tube end shell steam generator. The method according to claim 6,
The buffer rod extends into the tube sheet without extending through the tube sheet
Tube end shell steam generator. The method according to claim 1,
The steam generator further comprises a plurality of spaced apart tube support plates, each having an axial dimension perpendicular to the tube sheet and extending in a direction away from the primary fluid header, each positioned transverse to the axis, Including,
Wherein the hot leg and the cold leg pass through the plurality of spaced apart tube support plates and the buffer rod extends between at least a portion of the tube support plate
Tube end shell steam generator. 9. The method of claim 8,
The buffer rod extends through substantially all of the tube support plates from the tubesheet
Tube end shell steam generator. 9. The method of claim 8,
At least a portion of the axial length of the buffer rod is hollow and the hollow portion of the buffer rod has a wall thickness at least equal to or greater than the wall thickness of the plurality of U-
Tube end shell steam generator. 9. The method of claim 8,
The buffer rod
Tube end shell steam generator. 9. The method of claim 8,
Wherein the buffer rod begins to extend from a height above the tube sheet
Tube end shell steam generator. 9. The method of claim 8,
The extension of the buffer rod is terminated below the uppermost tube support plate
Tube end shell steam generator. 9. The method of claim 8,
Wherein the buffer rod extends through the holes in at least two adjacent tube support plates and at least a portion of the holes through which the buffer rod in one of the two adjacent tube support plates pass is defined by one of the two adjacent tube support plates Is offset from a corresponding hole in the other tube support plate
Tube end shell steam generator. 15. The method of claim 14,
The offset is at most about 4 mm
Tube end shell steam generator.

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