SUPPORT PLATE FOR U-SHAPED HEAT TRANSFER TUBE OF STEAM GENERATOR OF NUCLEAR POWER PLANT AND STEAM GENERATOR THEREOF

Abstract

 The present invention discloses a support plate for U-shaped heat transfer tube of steam generator of nuclear power plant including a plate body. The plate body is provided with a number of three-leaf plum blossom-shaped holes extending through the plate body. A hole bridge is formed between two adjacent three-leaf plum blossom-shaped holes. Each three-leaf plum blossom-shaped holes includes a boss edge, a side edge and a top edge. After the U-shaped heat transfer tubes are inserted into the three-leaf plum blossom-shaped holes, the boss edge supports tube wall of the U-shaped heat transfer tube. The side edge and the top edge of the three-leaf plum blossom-shaped hole and the tube wall of the U-shaped heat transfer tube enclose a heat exchange fluid channel at outer side of the U-shaped heat transfer tube. A tube gallery area is formed at a middle portion of the plate body. The tube gallery area is provided with through holes and the three-leaf plum blossom-shaped holes are arranged on two sides of the tube gallery area, wherein and an included angle of connection line of the three-leaf plum blossom-shaped hole and side edge corresponding thereto is α, and 0<α≤13°. Compared with the prior art, the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant according to the present invention make the U-shaped heat transfer tube arranged more compactly, and more U-shaped heat transfer tubes can be arranged on the same area, thereby reducing the overall size and cost of the equipment. The three-leaf plum blossom-shaped hole has a larger heat exchange fluid flow area, ensuring the structural continuity and the strength at the weakest point of the hole bridge structure of the support plate.

Description

FIELD OF THE INVENTION

[0001] The present invention generally relates to pressurized water reactor nuclear power plants and, more particularly, relates to support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof.

BACKGROUND OF THE INVENTION

[0002] At present, pressurized water reactor (PWR) nuclear power plants generally use steam generators having vertical, inverted U-shaped heat transfer tubes. The U-shaped heat transfer tubes are key components of the steam generator (SG). A steam generator generally includes a large number of U-shaped heat transfer tubes each has thin wall thickness and long straight section length. The U-shaped heat transfer tubes are easy to vibrate under the action of the fluid, which will cause fatigue failure of the U-shaped heat transfer tubes. Therefore, a support plate on the straight section of the U-shaped heat transfer tube is needed to effectively support the U-shaped heat transfer tube and ensure low vibration level of the steam generator during the operating life thereof, so that wear caused by vibration is acceptable. At the same time, it is necessary to ensure effective heat exchange of the fluid outside the U-shaped heat transfer tube, prevent evaporation in the pores, and reduce stress corrosion and sludge deposition in the U-shaped heat transfer tubes.

[0003] In a support plate for U-shaped heat transfer tube commonly used in existing PWR nuclear power plant, round holes are defined in the central tube gallery area of the support plate to facilitate natural circulation of the fluid outside the U-shaped heat transfer tube. However, it is difficult to compactly arrange this kind of support plate, the fluid circulation area and the continuity of the hole bridge structure are insufficient, which easily causes the increase of the fluid flow resistance outside the U-shaped heat transfer tube during operation of the steam generator and reduces the circulation rate of the steam generator. Moreover, insufficient structural continuity can easily lead to stress concentration and structural fatigue damage. In addition, the prior art fails to take the need of washing the support plate during in-service inspection into account, the sludge deposited on the support plate after the steam generator is running cannot be washed and removed effectively, which easily leads to partial evaporation of the U-shaped heat transfer tube. The support plate and the U-shaped heat transfer tube are prone to stress corrosion damage.

[0004] In view of the foregoing, what is needed, therefore, is to provide support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof, so that the U-shaped heat transfer tubes can be arranged compactly and have large heat exchange fluid circulation channel, thereby avoiding evaporation of the U-shaped heat transfer tubes.

SUMMARY OF THE INVENTION

[0005] One object of the present invention is to overcome the disadvantage of the prior art and provide support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof, so that the U-shaped heat transfer tubes can be arranged compactly and have a large heat exchange fluid circulation channel, thereby avoiding evaporation of the U-shaped heat transfer tubes.

[0006] According to one embodiment of the present invention, a support plate for U-shaped heat transfer tube of steam generator of nuclear power plant includes a plate body. The plate body is provided with a number of three-leaf plum blossom-shaped holes extending through the plate body. A hole bridge is formed between two adjacent three-leaf plum blossom-shaped holes. Each three-leaf plum blossom-shaped hole includes a boss edge, a side edge and a top edge. After the U-shaped heat transfer tube is inserted into the three-leaf plum blossom-shaped hole, the boss edge supports the tube wall of the U-shaped heat transfer tube. The side edge and the top edge of the three-leaf plum blossom-shaped hole and the tube wall of the U-shaped heat transfer tube enclose a heat exchange fluid channel at outer side of the U-shaped heat transfer tube. A tube gallery area is formed at a middle portion of the plate body. The tube gallery area is provided with through holes and the three-leaf plum blossom-shaped holes are arranged on two sides of the tube gallery area, wherein the included angle of connection line of the three-leaf plum blossom-shaped holes and side edge corresponding thereto is α, and 0<α≤13°.

[0007] According to one aspect of the present invention, the included angle of connection line of the three-leaf plum blossom-shaped holes and side edges corresponding thereto is α, and 5°≤α≤13°.

[0008] According to one aspect of the present invention, a ratio P/D of distance between two adjacent three-leaf plum blossom-shaped holes P to an outer diameter of the U-shaped heat transfer tube D is 1.2 to 1.5.

[0009] According to one aspect of the present invention, the plate body has a thickness of 25mm to 35mm.

[0010] According to one aspect of the present invention, the through holes are rectangular holes.

[0011] According to one aspect of the present invention, the through holes are round holes and rectangular holes.

[0012] According to one aspect of the present invention, the top edge is arc-shaped, and the arc center of the top edge is concentric with the center of the U-shaped heat transfer tube hole, and a circular arc transitions between the boss edge, the side edge and the top edge.

[0013] According to one aspect of the present invention, the three-leaf plum blossom-shaped holes are uniformly arranged on the plate body in a regular triangle fashion.

[0014] According to another embodiment of the present invention, a steam generator includes a U-shaped heat transfer tube and a support plate, and the support plate is the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of the present invention. Compared with the prior art, the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof of the present invention have the following advantages:

1) Due to the configuration and arrangement of the three-leaf plum blossom-shaped holes, the U-shaped heat transfer tube can be arranged compactly, and more U-shaped heat transfer tubes can be arranged on the same area, thereby reducing the overall size and cost of the equipment.

2) The three-leaf plum blossom-shaped hole has a larger circulation area of heat exchange fluid, which can avoid evaporation of the U-shaped heat transfer tube.

3) Through the treatment of the special angle structure of the hole bridge of the three-leaf plum blossom-shaped hole, the support plate has good structure continuity, the strength of the weakest point is ensured, and the stress concentration and structural fatigue damage of the hole bridge structure of the support plate are reduced.

4) Due to the holes in the tube gallery area in the middle of the support plate, sludge generated during the operation of the support plate can be flushed with sludge washing equipment during the maintenance process, thereby avoiding adverse effect of excessive sludge deposition on the performance of the steam generator and the safety of the U-shaped heat transfer tube, and improving the thermal and hydraulic performance of the steam generator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view of the arrangement of three-leaf plum blossom-shaped holes of a support plate for U-shaped heat transfer tube of steam generator of nuclear power plant according to one embodiment of the present invention;

Fig. 2 is an enlarged view of the three-leaf plum blossom-shaped hole of the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant according to one embodiment of the present invention;

Fig. 3 is a schematic view of a steam generator according to one embodiment of the present invention;

Fig. 4 is a cross-sectional view of the steam generator along a line A-A in Fig. 3;

Fig. 5 is an enlarged view of circled portion A in Fig. 4;

Fig. 6 is a cross-sectional view of the steam generator along a line B-B in Fig. 3; and

Fig. 7 is an enlarged view of circled portion B in Fig. 6.

[0016] 10-plate body; 12-three-leaf plum blossom-shaped hole; 120-boss edge; 122-side edge; 124-top edge; 14-hole bridge; 16-U-shaped heat transfer tube; 18-heat exchange fluid channel; 19-tube gallery area; 190-through hole; 1902-round hole; 1900-rectangular hole; 1- steam generator; 2- support plate; 3- support plate; 40- inspection hole.

DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to make the objective, technical solutions and effects of the present invention clearer, the present invention will be further described in detail below in conjunction with accompanying drawings and embodiments. It should be understood that the embodiments described herein are only for explaining the present invention, not for limiting the scope of the present invention.

[0018] Referring to Figs. 1 to 7, a support plate for U-shaped heat transfer tube of steam generator of nuclear power plant according to one embodiment of the present invention includes a plate body 10. The plate body 10 defines a number of three-leaf plum blossom-shaped holes 12 extending through the plate body 10. A hole bridge 14 is formed between two three three-leaf plum blossom-shaped holes 12. Each three-leaf plum blossom-shaped hole 12 includes a boss edge 120, a side edge 122 and a top edge 124. After the U-shaped heat transfer tube 16 is inserted into the three-leaf plum blossom-shaped hole 12, the boss edge 120 supports the tube wall of the U-shaped heat transfer tube 16, and the side edge 122 and top edge 124 of the three-leaf plum blossom-shaped hole 12 and the tube wall of the U-shaped heat transfer tube 16 jointly enclose a heat exchange fluid channel 18 outside the U-shaped heat transfer tube 16. A tube gallery area 19 is seated in the middle of the plate body 10, and the tube gallery area 19 is provided with a number of through holes 190. The three-leaf plum blossom-shaped holes 12 are arranged on two sides of the tube gallery area 19, wherein the included angle of connection line of the three-leaf plum blossom-shaped holes 12 and the side edge 122 corresponding thereto is α, and 0<α≤13°.

[0019] According to one embodiment of the present invention, the plate body 10 is made from martensitic stainless steel having good corrosion resistance. The plate body 10 has a thickness of 25mm to 35mm.

[0020] The three-leaf plum blossom-shaped holes 12 are uniformly arranged on the plate body 10 in a regular triangle fashion. The ratio P/D of the distance P between two adjacent three-leaf plum blossom-shaped holes 12 to the outer diameter D of the U-shaped heat transfer tube 16 is 1.2 to 1.5, ensuring the U-shaped heat transfer tubes 16 can be arranged compactly, and more U-shaped heat transfer tubes 16 being arranged on a same area, which can reduce the size of the device. There is a small gap between the boss edge 120 of the three-leaf plum blossom-shaped hole 12 and the tube wall of the U-shaped heat transfer tube 16, which provides support for the U-shaped heat transfer tube 16 during the operation of the nuclear power plant, to prevent the U-shaped heat transfer tube 16 from vibrating in the three-leaf plum blossom-shaped hole 12. The side edge 122 and the top edge 124 of the three-leaf plum blossom-shaped hole 12 and the outer wall of the U-shaped heat transfer tube 16 jointly enclose a heat exchange fluid channel 18 for the exchange heat of the outside of the U-shaped heat transfer tube 16.

[0021] The top edge 124 is arc shaped. The arc center of the top edge 124 is concentric with the center of the U-shaped heat transfer tube 16. A circle arc transitions between the boss edge 120, the side edge 122 and the top edge 124.

[0022] A hole bridge 14 is formed between two adjacent three-leaf plum blossom-shaped holes 12. In order to ensure the strength of the hole bridge 14, the included angle of the hole bridge 14 (the included angle of connection line of the three-leaf plum blossom-shaped holes 12 and side edge corresponding thereto) α is 0<α≤13°, preferably 5°<α≤13°. In the illustrated embodiment, the included angle α is 13°.

[0023] Figs. 3 to 5 show a first embodiment of the support plate of the present invention, i.e. support plate 2. The tube gallery area 19 in the middle of the plate body 10 of the support plate 2 is provided with a number of through holes 190. The through holes 190 are a rectangular hole and the rectangular holes are located on the central axis of the support plate 2. The length of the rectangular hole is greater than the width of the rectangular hole. Preferably, the length of the rectangular hole is 3 times greater than the width of the rectangular hole, the width of the rectangular hole is smaller than the width of the tube gallery area 19, and the three-leaf plum blossom-shaped holes 12 are arranged side by side on both sides of the rectangular hole. The size of the rectangular hole is sufficient to allow the sludge washing equipment to reach each layer of the support plate 2 through the rectangular hole during the maintenance of the steam generator, and then wash the sludge generated on the support plate 2 during operation.

[0024] Figs. 3, 6 and 7 show a second embodiment of a support plate of the present invention, i.e. support plate 3. The tube gallery area 19 in the middle of the plate body 10 of the support plate 3 is also provided with a number of through holes 190. Through holes 190 are rectangular holes 1900 and round holes 1902. The rectangular holes 1900 are regularly and evenly arranged on the center line of the tube gallery area 19, the round holes 1902 are the same, and the rectangular holes 1900 are spaced apart from the round holes 1902. The width of the round holes 1902 arranged side by side is substantially the same as the width of the rectangular holes 1900, and is smaller than the width of the tube gallery area 19. The length and width of the rectangular holes 1900 are almost the same, and the width is the same as that of the rectangular hole shown in Fig. 5. The three-leaf plum blossom-shaped holes 12 are arranged side by side on both sides of the round holes 1902 and the rectangular holes 1900. Due to the rectangular holes 1900 and round holes 1902 on the tube gallery area 19, the water outside the U-shaped heat transfer tube 16 can be forced into the gap area of the adjacent the U-shaped heat transfer tube 16, increasing the resistance, making the circulating water in the steam generator flows to places other than the tube gallery area 19 and preventing the water from directly flowing away from the tube gallery area 19, thereby affecting the heat exchange of the U-shaped heat transfer tube 16. The size of the rectangular hole 1900 and the round hole 1902 can be adjusted according to actual conditions.

[0025] The heat generated by the reactor core of the PWR nuclear power plant heats the water in the reactor pressure vessel. The heated high-temperature water flows into the U-shaped heat transfer tube 16, and the high-temperature water in the U-shaped heat transfer tube 16 transfers the heat. The water outside the U-shaped heat transfer tube 16 is heated to generate steam to drive the steam turbine to generate electricity. Due to the impact of the water flow and steam flow outside the U-shaped heat transfer tube 16, the U-shaped heat transfer tube 16 will vibrate during operation. Therefore, it is necessary to provide several support plates (2 and/or 3) with through holes 190 on the straight section of the U-shaped heat transfer tube 16, to limit the vibration of the U-shaped heat transfer tube 16 during operation.

[0026] Therefore, the present invention provides a steam generator 1 with a support plate 3 installed on the upper part thereof. Several support plates 2 are installed below the support plate 3. The straight sections of the U-shaped heat transfer tubes 16 are inserted into corresponding three-leaf plum blossom-shaped holes 12 in the support plate 2 and the support plate 3.

[0027] By inserting the U-shaped heat transfer tube 16 into the three-leaf plum blossom-shaped holes 12 of the support plates 3 and 2 in turn, the three-leaf plum blossom-shaped holes 12 on the support plate 3 and the support plate 2 will support the U-shaped heat transfer tubes 16 during the operation of the nuclear power plant, to provide effective support and ensure good heat transfer. At the same time, due to the rectangular holes on the support plate 2, during the maintenance of the steam generator 1, the sludge washing equipment is allowed to enter from the inspection hole 40, and pass through the rectangular holes in the tube gallery area 19 to reach the support plates 2 of each layer, and the sludge on the support plate 2 generated during the operation is washed. Since the uppermost support plate 3 is provided with rectangular holes 1900 and round holes 1902 on the tube gallery area 19, the water outside the U-shaped heat transfer tube 16 can be forced into the gap area between the adjacent U-shaped heat transfer tubes 16, increasing resistance and making the water circulating in the steam generator 1 flows outside the tube gallery area 19, to prevent the water flow from directly flowing away from the tube gallery area 19, so as not to affect the heat exchange of the U-shaped heat transfer tube 16 and improve the heat exchange performance of the steam generator 1.

[0028] Compared with the prior art, the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant and steam generator thereof of the present invention have the following advantages:

1) Due to the configuration and arrangement of the three-leaf plum blossom-shaped holes, the U-shaped heat transfer tube can be arranged compactly, and more U-shaped heat transfer tubes can be arranged on the same area, thereby reducing the overall size and cost of the equipment.

2) The three-leaf plum blossom-shaped hole has a larger circulation area of heat exchange fluid, which can avoid evaporation of the U-shaped heat transfer tube.

3) Through the treatment of the special angle structure of the hole bridge of the three-leaf plum blossom-shaped hole, the support plate has good structure continuity, the strength of the weakest point is ensured, and the stress concentration and structural fatigue damage of the hole bridge structure of the support plate are reduced.

4) Due to the holes in the tube gallery area in the middle of the support plate, sludge generated during the operation of the support plate can be flushed with sludge washing equipment during the maintenance process, thereby avoiding adverse effect of excessive sludge deposition on the performance of the steam generator and the safety of the U-shaped heat transfer tube, and improving the thermal and hydraulic performance of the steam generator.

[0029] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments, it should be appreciated that alternative embodiments without departing from the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A support plate for U-shaped heat transfer tube of steam generator of nuclear power plant, comprising a plate body (10), characterized in that the plate body (10) is provided with a plurality of three-leaf plum blossom-shaped holes (12) extending through the plate body (10), a hole bridge (14) is formed between two adjacent three-leaf plum blossom-shaped holes (12), each three-leaf plum blossom-shaped hole (12) comprises a boss edge (120), a side edge (122) and a top edge (124), after the U-shaped heat transfer tube (16) is inserted into the three-leaf plum blossom-shaped hole (12), the boss edge (120) supports a tube wall of the U-shaped heat transfer tube (16), the side edge (122) and top edge (124) of the three-leaf plum blossom-shaped hole (12) and a tube wall of the U-shaped heat transfer tube (16) enclose a heat exchange fluid channel (18) outside the U-shaped heat transfer tube (16), a tube gallery area (19) is formed in the middle of the plate body (10), and the tube gallery area (19) is provided with through holes (190), the three-leaf plum blossom-shaped holes (12) are arranged on two sides of the tube gallery area (19), characterized in that an included angle of connection lines of the three-leaf plum blossom-shaped holes (12) and side edge corresponding thereto is α, and 0<α≤13°.

2. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the included angle of connection line of the three-leaf plum blossom-shaped holes (12) and side edge corresponding thereto is α, and 5°≤α≤13°.

3. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that a ratio P/D of distance P between two adjacent three-leaf plum blossom-shaped holes (12) and outer diameter D of the U-shaped heat transfer tube is 1.2 to 1.5.

4. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the plate body (10) has a thickness of 25 mm to 35mm.

5. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the through holes (190) are rectangular holes (1900).

6. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the through holes (190) are round holes (1902) and rectangular holes (1900).

7. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the top edge (124) is arc-shaped, and an arc center of the top edge (124) is concentric with a center of the U-shaped heat transfer tube (16), and a circular arc transitions between the boss edge (120), the side edge (122) and the top edge (124).

8. The support plate for U-shaped heat transfer tube of steam generator of nuclear power plant of claim 1, characterized in that the three-leaf plum blossom-shaped holes (12) are uniformly arranged on the plate body (10) in a regular triangle fashion.

9. A steam generator (1), comprising: a U-shaped heat transfer tube (16) and a support plate (2,3), characterized in that the support plate (2,3) is the support plate for U-shaped heat transfer tube of steam generator of nuclear power plant according to any one of claims 1 to 8.

Drawing