Steam generator with axial preheater

Abstract

The steam generator comprises a pressure-bearing shell, a heat transfer pipe, a pipe plate, a partition plate, an inner-layer sleeve and an outer-layer sleeve, the pipe plate is arranged in the pressure-bearing shell, a containing cavity is formed between the pipe plate and the pressure-bearing shell, and the heat transfer pipe, the partition plate, the inner-layer sleeve and the outer-layer sleeve are all located in the containing cavity; the two ends of the heat transfer tube are arranged on the tube plate, the middle portion of the heat transfer tube is arranged in the inner sleeve to form a tube bundle area, the outer sleeve is arranged on the outer side of the inner sleeve in a sleeving mode, the bottom of the partition plate is connected with the tube plate, and the two sides of the partition plate penetrate through the inner sleeve and are connected with the two sides of the outer sleeve. A cold side descending channel is formed among the inner-layer sleeve, the outer-layer sleeve and the partition plate, the two ends of the cold side descending channel communicate with the containing cavity and the pipe bundle area correspondingly, and a main water supply opening communicating with the cold side descending channel is formed in the pressure-bearing shell. By means of the structure, the enhanced heat exchange effect of the preheater is improved, and meanwhile abrasion of the heat transfer pipes is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of heat exchangers, and in particular to a steam generator with an axial preheater. Background Art

[0002] As a key device connecting the primary and secondary circuits in the steam supply system of a pressurized water reactor nuclear power plant, the steam generator undertakes the important function of heat and mass transfer. Its performance largely determines the safe, reliable and economical operation of the nuclear power plant unit. In order to strengthen the heat exchange on the secondary side, a steam generator with a preheater came into being. It introduces all the secondary side feed water into the cold end of the heat transfer tube bundle, and introduces the recycled water separated by the steam-water separator and the dryer into the hot end of the tube bundle. The large temperature difference between the secondary side feed water and the cold end of the primary side of the tube bundle is used to improve the heat exchange efficiency. Compared with the steam generator without a preheater, the saturated steam pressure is higher under the same conditions, which can effectively improve the unit power and the economy of the nuclear power unit. However, the existing steam generator with a preheater still has many problems in practical applications:

[0003] Prior art 1: Patent US6173680B1 discloses a steam generator with a preheater, in which the secondary side feed water enters the steam generator through a semi-annular feed water pipe assembly. Under the guidance of the baffle, the feed water enters the cold side descending channel composed of a double-layer sleeve in the form of a jet. However, this structure has the problem of main feed water backflow and the feed water jet carrying too much recirculated water. After the secondary side feed water flows out of the baffle, part of it flows back upward into the hot side descending channel, resulting in a discount in the enhanced heat exchange effect of the preheater; after the feed water passes through the baffle, the flow velocity is high and the local pressure is low, and too much recirculated water is entrained into the descending channel, reducing the enhanced heat exchange effect of the preheater.

[0004] Prior art 2: The preheater type steam generator disclosed in patent US4357908A uses a semi-circular feedwater pipe assembly and a long J-tube to introduce the secondary side feedwater into the steam generator descending channel. This technology has the problem of main feedwater reflux, causing the preheater to enhance the heat exchange effect and deviate from expectations. In addition, the J-tube has a large resistance, which increases the head of the main feedwater pump, increasing the manufacturing difficulty and cost of the main pump.

[0005] Prior art three: Please refer to Figure 1 , some existing technologies set the main feed water pipe at the bottom of the lower pressure shell of the steam generator, and introduce the feed water into the preheater installed on the cold side of the bottom of the heat transfer tube. The cold and hot sides of the heat transfer tube are separated by the pipe gallery partition. This technology uses baffles to guide the secondary side feed water to scour the heat transfer tube horizontally, which is easy to cause turbulent vibration and micro-vibration wear of the heat transfer tube. If the design is not considered enough, it may also cause fluid elastic instability under the condition of loose support with gaps, causing collision wear between the heat transfer tube and the baffle support. In addition, there is a gap between the insulation board at the bottom of the preheater and the heat transfer tube. The fluid leakage problem will reduce the enhanced heat exchange effect of the preheater and the thermal power of the steam generator.

[0006] Prior art 4: Please refer to Figure 2 This solution uses a manifold device and a small-area anti-collision plate to disperse the water supply, and continuously flushes the heat transfer tube horizontally through the baffle. Although the heat exchange efficiency is improved to a certain extent, the vibration and wear of the heat transfer tube caused by the baffle cannot be avoided. In addition, the anti-collision plate design does not adequately control the uniformity of fluid distribution, which is easy to form local hot spots or flow dead zones, affecting the overall thermodynamic performance. Summary of the invention

[0007] The object of the present invention is to provide a steam generator with an axial preheater, aiming to solve the problems of poor enhanced heat exchange effect of the preheater of the existing steam generator and easy wear of the heat transfer tube.

[0008] An embodiment of the present invention provides a steam generator with an axial preheater, comprising: a pressure shell, a heat transfer tube, a tube sheet, a partition plate, an inner sleeve and an outer sleeve, wherein the tube sheet is arranged in the pressure shell and forms an accommodating cavity with the pressure shell, the heat transfer tube, the partition plate, the inner sleeve and the outer sleeve are all located in the accommodating cavity, both ends of the heat transfer tube are arranged on the tube sheet, the middle part of the heat transfer tube is arranged in the inner sleeve to form a tube bundle area, the outer sleeve is sleeved on the outside of the inner sleeve, the bottom of the partition plate is connected to the tube sheet, both sides of the partition plate pass through the inner sleeve and are connected to both sides of the outer sleeve, a cold side descending channel is formed between the inner sleeve, the outer sleeve and the partition plate, both ends of the cold side descending channel are connected to the accommodating cavity and the tube bundle area respectively, and the pressure shell is provided with a main water supply port connected to the cold side descending channel.

[0009] Furthermore, the cold side descending channel is an annular cavity, and the curvature of the annular cavity is 40° to 160°.

[0010] Furthermore, one end of the inner sleeve is conically arranged, one end of the outer sleeve extends to one end of the inner sleeve, and a first communication port communicating with the accommodating cavity is provided between one end of the outer sleeve and one end of the inner sleeve.

[0011] Furthermore, the other end of the outer sleeve extends to the tube sheet, and a second communication port communicating with the tube bundle area is provided between the other end of the outer sleeve and the other end of the inner sleeve.

[0012] Furthermore, it also includes a flow limiting member, on which a plurality of flow limiting hole groups are arranged, and the flow limiting member is arranged in the cold side descending channel and is located near the first connecting port.

[0013] Further, a plurality of groups of the flow limiting hole groups are arranged around the center of the inner sleeve, each group of the flow limiting hole groups includes a plurality of flow limiting holes, and the spacing between adjacent flow limiting holes in each group of the flow limiting hole groups is the same.

[0014] Furthermore, it also includes: a heat-insulating sleeve, which is arranged between the outer sleeve and the inner wall of the main water supply port.

[0015] Furthermore, a water flow dispersion portion is provided on the inner sleeve, and the water flow dispersion portion is arranged corresponding to the main water supply port.

[0016] Furthermore, the cross section of the water flow dispersion portion is conical.

[0017] Furthermore, a plurality of dispersing protrusion structures are provided on the water flow dispersing portion.

[0018] Furthermore, it also includes: a flow distributor, on which a plurality of distribution through holes are arranged, and the flow distributor is arranged in the cold side descending channel so that the velocity distribution of the fluid in the cold side descending channel entering the tube bundle area is uniform.

[0019] Furthermore, the flow distribution component is located below the main water supply port.

[0020] Furthermore, a plurality of the distribution through holes are arranged at intervals around the center of the inner sleeve, and the spacing between adjacent distribution through holes is the same.

[0021] Furthermore, a baffle for blocking the upward flow of fluid flowing out of the main water supply port is provided at a portion of the cold side descending channel located above the main water supply port.

[0022] Furthermore, the inner sleeve is provided with an opening, and the opening is located above the baffle.

[0023] Furthermore, the height of the bottom of the opening is greater than the height of the baffle.

[0024] Furthermore, it also includes a mixing device, which is arranged in the inner sleeve and corresponds to the opening.

[0025] Furthermore, the cross-sectional area of ​​the cold-side descending channel decreases from both ends to the middle.

[0026] The present invention discloses a steam generator with an axial preheater, comprising: a pressure shell, a heat transfer tube, a tube sheet, a partition plate, an inner sleeve and an outer sleeve. The tube sheet is arranged in the pressure shell and forms an accommodating cavity with the pressure shell. The heat transfer tube, the partition plate, the inner sleeve and the outer sleeve are all located in the accommodating cavity. Both ends of the heat transfer tube are arranged on the tube sheet, the middle part of the heat transfer tube is arranged in the inner sleeve to form a tube bundle area, the outer sleeve is sleeved on the outside of the inner sleeve, the bottom of the partition plate is connected to the tube sheet, both sides of the partition plate pass through the inner sleeve and are connected to both sides of the outer sleeve, a cold side descending channel is formed between the inner sleeve, the outer sleeve and the partition plate, both ends of the cold side descending channel are respectively connected to the accommodating cavity and the tube bundle area, and a main water supply port connected to the cold side descending channel is arranged on the pressure shell. The present invention guides all the feed water into the preheater, eliminates the risk of the secondary side feed water flowing back upward into the hot side descending channel, and limits the excessive recirculating water from entering the descending channel, thereby improving the enhanced heat exchange effect of the preheater. At the same time, by dispersing the main feed water through the cold side inner sleeve and entering the tube bundle area through the sleeve bottom opening above the tube sheet, the continuous lateral flushing of the heat transfer tubes to cause turbulent excitation of the heat transfer tubes and the flow elastic instability under the loose support condition are avoided, thereby reducing the wear of the heat transfer tubes and improving the service life of the heat transfer tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0028] Figure 1 It is a structural schematic diagram of a steam generator of prior art 3;

[0029] Figure 2 It is a structural schematic diagram of a steam generator of prior art 4;

[0030] Figure 3 It is a schematic structural diagram of a steam generator with an axial preheater according to Example 1;

[0031] Figure 4 A schematic diagram of the structure between the inner sleeve, the outer sleeve and the partition plate from a first-person perspective;

[0032] Figure 5 A schematic diagram of the structure between the inner sleeve, the outer sleeve and the partition plate from a second perspective;

[0033] Figure 6 for Figure 3 Partial diagram of A in the figure;

[0034] Figure 7 for Figure 3 Partial diagram of B in the figure;

[0035] Figure 8 It is a cross-sectional schematic diagram of the thermal insulation sleeve and the surrounding structure;

[0036] Fig. 9 It is a cross-sectional schematic diagram of a water flow dispersion portion provided on an inner sleeve;

[0037] Fig.10 It is a cross-sectional schematic diagram of a dispersion protrusion structure provided on a water flow dispersion part;

[0038] Fig.11 It is a schematic structural diagram of a steam generator with an axial preheater according to Example 2;

[0039] Fig.12 It is a structural schematic diagram of a flow distribution component;

[0040] Fig.13 It is a structural schematic diagram of a steam generator with an axial preheater according to Example 3;

[0041] Fig.14 for Fig.13 Partial diagram of C in the middle;

[0042] Fig.15 It is a structural schematic diagram of a steam generator with an axial preheater according to Example 4;

[0043] Fig.16 It is a structural schematic diagram of the current limiting component;

[0044] Fig.17 This is a schematic diagram of the structure of the main water supply pipe;

[0045] Fig.18 is a cross-sectional schematic diagram of the thermal insulation sleeve and surrounding structures of Example 5;

[0046] Description of the markings in the figure:

[0047] 1. Pressure shell; 2. Heat transfer tube; 3. Tube sheet; 4. Partition plate; 5. Inner sleeve; 6. Outer sleeve; 7. Accommodating cavity; 8. Tube bundle area; 9. Cold side descending channel; 10. Main water supply port; 11. First connecting port; 12. Second connecting port; 13. Insulating sleeve; 14. Water flow dispersion part; 15. Dispersion protrusion structure; 16. Lower head; 17. Blocking plate; 18. First water chamber; 19. Second water chamber; 20. Primary side inlet pipe; 21. Primary side outlet pipe; 22. Upper head; 23. Conical cylinder; 24. Flow distributor; 25. Distribution through hole; 26. Baffle; 27. Opening; 28. Mixing device; 29. ​​Flow limiting component; 30. Flow limiting hole group; 31. Flow limiting hole; 32. Main water supply pipe. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0050] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0051] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0052] Embodiment 1:

[0053] See also Figure 3-Figure 5 The present embodiment provides a steam generator with an axial preheater, comprising: a pressure shell 1, a heat transfer tube 2, a tube sheet 3, a partition plate 4, an inner sleeve 5 and an outer sleeve 6. The tube sheet 3 is arranged in the pressure shell 1 and forms an accommodating chamber 7 with the pressure shell 1. The heat transfer tube 2, the partition plate 4, the inner sleeve 5 and the outer sleeve 6 are all located in the accommodating chamber 7. Both ends of the heat transfer tube 2 are arranged on the tube sheet 3, and the middle part of the heat transfer tube 2 is arranged in the inner sleeve 5 to form a tube bundle area 8. The outer sleeve 6 is sleeved on the outer side of the inner sleeve 5. The bottom of the partition plate 4 is connected to the tube sheet 3. Both sides of the partition plate 4 pass through the inner sleeve 5 and are connected to both sides of the outer sleeve 6. A cold side descending channel 9 is formed between the inner sleeve 5, the outer sleeve 6 and the partition plate 4. Both ends of the cold side descending channel 9 are respectively connected to the accommodating chamber 7 and the tube bundle area 8. The pressure shell 1 is provided with a main water supply port 10 connected to the cold side descending channel 9.

[0054] This embodiment guides all the feed water into the preheater, eliminates the risk of the secondary side feed water flowing back upward into the hot side descending channel, and limits the excessive amount of recirculated water entering the descending channel, thereby improving the enhanced heat exchange effect of the preheater. At the same time, by dispersing the main feed water through the cold side inner sleeve and entering the tube bundle area 8 through the sleeve bottom opening above the tube plate 3, continuous lateral scouring of the heat transfer tube 2 to cause turbulent excitation of the heat transfer tube 2 and fluid elastic instability under loose support conditions is avoided, thereby reducing the wear of the heat transfer tube 2 and improving the service life of the heat transfer tube 2.

[0055] Its working principle is as follows: the main feed water enters the cold side descending channel 9 from the main feed water port 10 on the pressure shell 1, and the channel is surrounded by the inner sleeve 5, the outer sleeve 6 and the partition plate 4. The main feed water flows downward in the cold side descending channel 9, and then the main feed water flows through the tube bundle area 8, and performs convection heat exchange with the high-temperature fluid in the heat transfer tube 2 in the tube bundle area 8. The heat is transferred to the main feed water through the tube wall. Then the preheated main feed water flows upward to the steam-water separator and the dryer, and then part of the recirculating water separated by the steam-water separator and the dryer enters the cold side descending channel 9 through a specific structure to mix with the main feed water. The mixed fluid continues to flow downward into the tube bundle area 8, and the other part of the recirculating water enters the hot side of the tube bundle area 8 through the annular descending channel between the pressure shell 1 and the inner sleeve 5, and between the pressure shell 1 and the outer sleeve 6.

[0056] In this embodiment, the cold side descending channel 9 is an annular cavity, and the arc of the annular cavity is 40° to 160°.

[0057] The curvature design of the annular cavity reduces the flow resistance of the fluid in the cold side descending channel 9. Compared with channels with right angles or too small curvatures, the curvature of 40° to 160° allows the main feed water and recirculating water to flow downward more smoothly, reducing energy consumption, and also helps to reduce pressure fluctuations caused by poor fluid flow, ensuring the stability of steam generator operation.

[0058] In this embodiment, one end of the inner sleeve 5 is conical, one end of the outer sleeve 6 extends to one end of the inner sleeve 5, and a first communication port 11 (such as Figure 6 shown).

[0059] The first connecting port 11 formed between the outer sleeve 6 and one end of the inner sleeve 5, in conjunction with the sealed connection between the two ends of the outer sleeve 6 and the partition plate 4, can accurately adjust the flow of the recirculating water. By controlling the size of the first connecting port 11, 10% of the recirculating water separated from the steam and water can enter the annular cavity formed by the inner sleeve 5 and the outer sleeve 6 and mix with the main feed water, while the other 90% of the recirculating water can enter the hot side of the tube bundle area 8 through the annular descending channel between the pressure shell 1 and the inner sleeve 5, and between the pressure shell 1 and the outer sleeve 6. This precise flow control helps to optimize the heat exchange process in the steam generator, ensure that the preheater achieves the expected enhanced heat exchange effect, improve the overall heat exchange efficiency, and thus improve the economy of the nuclear power unit.

[0060] In this embodiment, the other end of the outer sleeve 6 extends to the tube sheet 3, and a second communication port 12 (such as Figure 7 shown).

[0061] The existence of the second connecting port 12 enables the fluid to be distributed relatively evenly into the tube bundle area 8. Since the temperature and flow rate of the fluid in the annular space between the outer sleeve 6 and the inner sleeve 5 are relatively uniform, when entering the tube bundle area 8 through the second connecting port 12, a relatively uniform fluid distribution can be formed on the cross section of the tube bundle area 8, avoiding the situation where the local fluid flow is too large or too small. This helps to ensure that the fluid working conditions around each heat transfer tube 2 in the tube bundle area 8 are similar, achieve more uniform heat exchange, prevent local overheating or overcooling, and improve the service life of the heat transfer tube 2 and the reliability of the steam generator.

[0062] In this embodiment, please refer to Figure 8 , and also includes: a heat insulating sleeve 13, which is arranged between the outer sleeve 6 and the inner wall of the main water supply port 10.

[0063] When the steam generator is running, the temperature of the main feed water is low, while the ambient temperature inside the pressure shell 1 is high. The presence of the thermal insulation sleeve 13 effectively blocks the direct contact between the low-temperature main feed water and the pressure shell 1, and forms a water gap between the outer sleeve 6, the thermal insulation sleeve 13 and the pressure shell 1 including the main feed water connection pipe, thereby reducing the thermal shock of the low-temperature feed water on the pressure shell 1. Thermal shock may cause the material performance of the pressure shell 1 to deteriorate, cracks to form and other problems. The thermal insulation sleeve 13 can prevent such situations from happening, extend the service life of the pressure shell 1, and ensure the structural integrity and safety of the steam generator. Silicone rubber

[0064] The heat insulating sleeve 13 can be made of alkali-free glass fiber, silicone rubber, polytetrafluoroethylene (PTFE) and fluoroplastic (F46).

[0065] In this embodiment, the inner sleeve 5 is provided with a water flow dispersion portion 14 (such as Fig. 9 As shown), the water flow dispersion part 14 protrudes from the inner sleeve 5, and the water flow dispersion part 14 is arranged corresponding to the main water supply port 10.

[0066] When the main feed water enters directly, turbulence may be formed due to uneven flow velocity, increasing flow resistance. The water flow dispersion part 14 rectifies the feed water so that the water flow enters the cold side descending channel 9 in a more orderly manner, reducing the generation of turbulence and vortices, and reducing the flow resistance of the fluid in the channel. This means that the energy required for the main feed water pump to push the water flow is reduced, reducing the energy consumption of the pump and improving the energy efficiency of the entire system. In addition, the water flow dispersion part 14 can effectively buffer the impact of the main feed water entering and stabilize the flow in the cold side descending channel 9. When the main feed water flow rate fluctuates slightly, the water flow dispersion part 14 can adjust the entry speed and direction of the feed water to make the flow in the channel change smoothly, avoid the impact on subsequent components due to sudden changes in flow, and ensure the stability of the fluid flow in the steam generator.

[0067] Furthermore, the cross section of the water flow dispersion portion 14 is conical. Specifically, the water flow dispersion portion 14 can be a cone, a pyramid, or other structures with conical cross sections.

[0068] The water flow dispersion part 14 with a conical cross-section can disperse the main feed water efficiently. When the main feed water enters the steam generator, the concentrated water flow has a large impact force, which is not conducive to uniform heat exchange. The large end of the conical structure faces the main feed water. As the water flows along the cone surface to the small end, the water flow area gradually decreases, the water flow velocity and pressure distribution change, and the main feed water is evenly dispersed. Compared with other shapes of dispersion parts, the cone can ensure that the water flows more evenly into the cold side descending channel 9.

[0069] It should be noted that the water flow dispersion portion 14 may also adopt other structures besides the cone shape, such as a special shape.

[0070] In some embodiments, the water flow dispersion portion 14 is provided with a plurality of dispersion protrusion structures 15 (such as Fig.10 shown).

[0071] The dispersing protrusions 15 can break the concentrated flow state of the water flow, so that the water flow is diverted to multiple directions when passing through the water flow dispersing portion 14. Compared with the case without the protrusions, the water flow will be more evenly dispersed to different areas, avoiding the situation where the water flow is concentrated in some local areas while the water flow in other areas is scarce, thereby achieving a more ideal water flow distribution.

[0072] The dispersing protrusion structure 15 may be a hemispherical protrusion, or may be an arc-shaped or irregular-shaped protrusion structure or other protrusion structures that can disperse the main water supply more evenly.

[0073] In some embodiments, the water flow dispersion portion 14 may be integrally disposed on the inner sleeve 5 .

[0074] The integrated setting makes the water flow dispersion part 14 and the inner sleeve 5 form an integral structure. Compared with the assembled structure, the gaps and weak points in the connection parts are reduced, so that the pressure and impact of the water flow can be better withstood, the stability and reliability of the entire structure during operation are improved, and the risk of failure caused by loose components or loose connections is reduced. At the same time, the integrated structure avoids the gaps and unevenness that may exist between different components, making the water flow smoother when passing through the water flow dispersion part 14 and the inner sleeve 5, reducing the turbulence and interference of the water flow during the flow process. This helps to reduce the energy loss of the water flow and improve the stability and uniformity of the water flow.

[0075] In some embodiments, the water flow dispersion portion 14 is separately disposed on the inner sleeve 5 .

[0076] The split structure allows the water flow dispersion part 14 and the inner sleeve 5 to be independently optimized and designed according to their respective functions and performance requirements. The water flow dispersion part 14 can focus on achieving the best water flow dispersion effect, such as using special shapes, structures or materials to improve the uniformity and stability of the water flow; while the inner sleeve 5 can be specially designed and manufactured according to its main functions, such as heat preservation and anti-corrosion, so that both can play the best performance and improve the overall performance of the entire system. At the same time, the water flow dispersion part 14 is in a high-speed water flow environment for a long time, and the water flow will have a strong scouring effect on the surface of the water flow dispersion part 14, which will gradually wear its surface material, make the surface rough, and even cause local damage, affecting its normal function, thereby shortening its service life. Therefore, the split water flow dispersion part 14 can be easily disassembled and replaced. When maintenance is required, it is only necessary to remove the water flow dispersion part 14 for replacement, without disassembling the entire inner sleeve 5. This not only reduces maintenance costs, but also improves maintenance efficiency.

[0077] In this embodiment, please refer to Figure 3 , and also includes: a lower head 16 and a blocking plate 17, the lower head 16 is fixedly connected to the pressure shell 1, a water chamber is formed between the lower head 16 and the tube sheet 3, two ends of the blocking plate 17 are respectively connected to the tube sheet 3 and the lower head 16 to divide the water chamber into a first water chamber 18 and a second water chamber 19, the lower head 16 is provided with a primary side inlet pipe 20 connected to the first water chamber 18, and a primary side outlet pipe 21 connected to the second water chamber 19, and two ends of the heat transfer tube 2 are respectively connected to the first water chamber 18 and the second water chamber 19.

[0078] The blocking plate 17 separates the water chamber between the lower end 16 and the tube sheet 3, and cooperates with the primary side inlet and outlet pipes, so that the primary side working fluid flows into the first water chamber 18 from the primary side inlet pipe 20, enters the tube through one end of the heat transfer tube 2, exchanges heat with the secondary side working fluid during the flow in the tube, and then flows out from the other end of the heat transfer tube 2 into the second water chamber 19, and finally flows out through the primary side outlet pipe 21. This orderly process prolongs the heat exchange time, improves the heat transfer efficiency, and thus improves the overall heat exchange effect of the steam generator.

[0079] In this embodiment, it also includes: an upper head 22 and a conical cylinder 23, and two ends of the conical cylinder 23 are respectively fixedly connected to the upper head 22 and the pressure-bearing shell 1.

[0080] Embodiment 2:

[0081] See also Fig.11 and Fig.12 In this embodiment, it also includes: a flow distribution member 24, on which a plurality of distribution through holes 25 are arranged, and the flow distribution member 24 is arranged in the cold side descending channel 9 so that the velocity distribution of the fluid in the cold side descending channel 9 entering the tube bundle area 8 is uniform.

[0082] When the fluid enters the tube bundle area 8 unevenly, the heat transfer tube 2 will be subjected to impact forces of different directions and magnitudes, causing the heat transfer tube 2 to vibrate. Long-term vibration can easily cause wear, fatigue, or even rupture of the heat transfer tube 2, seriously affecting the safety of the equipment. The flow distributor 24 ensures that the fluid enters evenly, reduces the difference in such impact forces, and reduces the vibration amplitude and frequency of the heat transfer tube 2. It effectively reduces the risk of equipment failure caused by vibration and ensures the long-term stable operation of the steam generator. In addition, the multiple distribution holes 25 on the flow distributor 24 can act as a simple filtering device to intercept foreign loose parts such as metal debris, welding slag, etc. that enter the cold side descending channel 9 with the fluid. If these foreign objects enter the tube bundle area 8, they may scratch the surface of the heat transfer tube 2, destroy the protective film of the heat transfer tube 2, and cause corrosion or accelerate wear. The flow distributor 24 intercepts foreign objects outside, reduces the possibility of damage to the heat transfer tube 2, extends the service life of the heat transfer tube 2, and reduces equipment maintenance costs and downtime for overhaul.

[0083] Furthermore, the flow distribution component 24 is located below the main water supply port 10 .

[0084] After the main water supply flows out from the main water supply port 10, it flows downward under the action of gravity. The flow distributor 24 is located below it, which can timely disperse the main water supply for a second time. After the main water supply is initially dispersed by the water flow dispersion part 14, there may still be uneven distribution of flow velocity and flow rate, and the flow distributor 24 further refines and evens it. At the same time, in this process, the main water supply can be more fully mixed with the recycled water entering the cold side descending channel 9 from other channels, so that the fluid parameters entering the tube bundle area 8 are more uniform, creating good conditions for subsequent efficient and stable heat exchange in the tube bundle area 8.

[0085] Furthermore, a plurality of distribution through holes 25 are arranged at intervals around the center of the inner sleeve 5 , and the intervals between adjacent distribution through holes 25 are the same.

[0086] Multiple distribution holes 25 are evenly distributed around the center of the inner sleeve 5, so that the fluid in the cold side descending channel 9 can enter the tube bundle area 8 evenly from all directions. This all-round uniform flow distribution method avoids the fluid from entering the tube bundle area 8 from a certain area, ensuring that each heat transfer tube 2 in the tube bundle area 8 can be exposed to a fluid with a similar flow rate and flow velocity, so that the heat exchange conditions of the heat transfer tubes 2 are basically consistent, effectively avoiding the phenomenon of excessive or weak local heat exchange, and improving the overall heat exchange efficiency and steam quality of the steam generator. At the same time, the spacing between adjacent distribution holes 25 is the same, ensuring that the resistance and distribution conditions encountered by the fluid when passing through the flow distribution component 24 are consistent. Regardless of the operating conditions of the steam generator, it can ensure that the fluid enters the tube bundle area 8 stably and evenly.

[0087] Embodiment 3:

[0088] See also Fig.13 and Fig.14 In this embodiment, a baffle 26 for blocking the upward flow of the fluid flowing out of the main water supply port 10 is provided at a portion of the cold side descending channel 9 located above the main water supply port 10 .

[0089] The baffle 26 can effectively prevent the fluid flowing out of the main water supply port 10 from flowing upward and out of the cold side descending channel 9, forcing it to flow downward along the cold side descending channel 9. In the absence of the baffle 26, the main feed water may flow back upward, causing part of the feed water to be unable to fully participate in the heat exchange process, thereby reducing the heat exchange efficiency of the steam generator. After the baffle 26 is set, it is ensured that all the main feed water flows downward, enters the tube bundle area 8, and performs convective heat exchange with the high-temperature fluid in the cold side tube bundle, thereby improving the utilization rate of the main feed water and enhancing the overall heat exchange effect. At the same time, the baffle 26 can prevent the recirculating water from entering the cold side descending channel 9, thereby reducing the impact of the recirculating water entering the cold side descending channel 9 on the heat exchange effect of the preheater, thereby improving the heat exchange effect of the preheater.

[0090] Furthermore, the inner sleeve 5 is provided with an opening 27, which is located above the baffle 26. The opening 27 allows part of the recirculated water from the steam-water separation to enter the tube bundle area 8, mix with the main feed water heated to a temperature close to the saturation temperature, flow upward and generate steam.

[0091] The openings 27 reduce the flow rate at the bottom of the hot side tube bundle, thereby reducing the lateral flushing speed at the bottom of the hot side tube bundle, thereby reducing the risk of vibration and wear of the heat transfer tubes 2.

[0092] Furthermore, the height of the bottom of the opening 27 is greater than the height of the baffle 26 .

[0093] The height difference between the opening 27 and the baffle 26 guides the fluid to flow naturally in the direction of gravity, avoiding the lateral scouring effect caused by the baffle or complex flow guide structure. The longitudinal flow pattern of the fluid can reduce turbulent excitation and micro-vibration wear of the heat transfer tube 2, reduce the risk of fluid elastic instability, and extend the life of the equipment.

[0094] In some embodiments, a mixing device 28 is further included. The mixing device 28 is disposed in the inner sleeve 5 and is disposed corresponding to the opening 27 .

[0095] A mixing device 28, such as a guide vane or a mixing grid, is provided at the opening 27 above the baffle on the inner sleeve 5. After the recirculating water enters from the opening 27, it is more fully mixed with the main feed water through these mixing devices 28. The guide vane can guide the flow direction of the recirculating water so that it forms a staggered flow state with the main feed water, thereby increasing the uniformity of mixing; the mixing grid can divide and mix the recirculating water and the main feed water for multiple times, further improving the mixing effect, ensuring that the temperature and composition of the fluid entering the tube bundle area 8 are uniform, thereby improving the heat exchange efficiency.

[0096] Embodiment 4:

[0097] See also Fig.15 and Fig.16 In this embodiment, a flow limiting member 29 is further included. A plurality of flow limiting hole groups 30 are arranged on the flow limiting member 29. The flow limiting member 29 is arranged in the cold side descending channel 9 and is located near the first connecting port 11.

[0098] The recirculating water enters the cold side descending channel 9 through the first connecting port 11, and the flow limiting hole group 30 on the flow limiting member 29 can accurately control its flow by controlling the flow area and the opening 27 of the first connecting port 11. By adjusting the aperture, number and distribution of the flow limiting hole group 30, the flow of the recirculating water entering the cold side descending channel 9 can be accurately adjusted to ensure that 10% of the recirculating water enters the channel and mixes with the main feed water. This precise flow control helps to optimize the heat transfer process in the steam generator, ensure that the preheater achieves the expected enhanced heat exchange effect, and improve the overall heat exchange efficiency.

[0099] Furthermore, a plurality of flow limiting hole groups 30 are arranged around the center of the inner sleeve 5 , each flow limiting hole group 30 includes a plurality of flow limiting holes 31 , and the spacing between adjacent flow limiting holes 31 in each flow limiting hole group 30 is the same.

[0100] The multiple groups of flow-limiting hole groups 30 arranged around the center of the inner sleeve 5 can uniformly control the flow of the recycled water entering the cold side descending channel 9 from multiple directions. Since the spacing between adjacent flow-limiting holes 31 in each group of flow-limiting hole groups 30 is the same, it is ensured that the flow distribution of the recycled water in the circumferential direction is uniform when passing through the flow-limiting member 29. The regular layout of the flow-limiting hole groups 30 makes the flow of the recycled water smoother when passing through the flow-limiting member 29, reducing the local resistance and turbulence caused by the uneven distribution of the orifices. The same spacing between adjacent flow-limiting holes 31 ensures that the water flow conditions are consistent when passing through each hole, avoids sudden changes in water flow velocity and pressure, reduces flow resistance, and improves the efficiency of the recycled water entering the cold side descending channel 9.

[0101] See also Fig.17 In this embodiment, it also includes: a main water supply pipe 32, which is arranged on the pressure shell 1, and the main water supply port 10 is arranged in the main water supply pipe 32. The main water supply pipe 32 is directly arranged on the pressure shell 1. This design makes the whole system more compact, reduces additional connecting parts and pipes, and thus saves space. Among them, the main water supply pipe 32 can be detachably arranged on the pressure shell 1, or it can be integrally arranged on the pressure shell 1.

[0102] Embodiment 5:

[0103] In this embodiment, please refer to Fig.18 , the cross-sectional area of ​​the cold side descending channel 9 decreases from both ends to the middle. That is, the cross-sectional area of ​​the cold side descending channel 9 decreases first and then increases. Specifically, at least one side surface of the cold side descending channel 9 gradually approaches the center of the cold side descending channel 9 and gradually moves away from the center of the cold side descending channel 9 from top to bottom.

[0104] When the recirculating water flows from the wider sections at both ends of the channel to the narrow area in the middle, the flow rate naturally increases, and the increase in inertial force effectively suppresses the flow separation phenomenon and reduces the generation of vortices and backflow. This smooth transition flow state enables the fluid to diffuse stably after passing through the narrow section, significantly improving the flow uniformity. Secondly, after the contraction of the middle section of the channel accelerates the fluid, the gradual expansion design of the expansion section gradually restores the static pressure, greatly reducing the energy loss caused by the sudden change in flow rate. Compared with the straight channel, this dynamic balance mechanism significantly reduces the overall pressure drop, thereby reducing the energy consumption of the system. At the same time, the traditional straight channel is prone to cavitation collapse (cavitation) due to the sudden drop in local pressure under high pressure difference, while the smooth transition design of the double cone structure can avoid the formation of extremely low pressure areas by controlling the pressure gradient, fundamentally reducing the probability of cavitation, and thus forming a stable flow state. The stable flow state reduces the impact force of the fluid on the pipe wall, and at the same time, the turbulent noise is significantly reduced, which improves the comfort and safety of the equipment operating environment.

[0105] Furthermore, the connections of the four side surfaces of the cold side descending channel 9 are arc-shaped, that is, the two connections between the inner sleeve 5 and the partition plate 4 are arc-shaped, and the two connections between the outer sleeve 6 and the partition plate 4 are arc-shaped.

[0106] The arc-shaped connection makes the flow path of the fluid in the cold side descending channel 9 smoother, avoiding the flow dead corners and turbulent areas caused by right-angle or sharp connections. The fluid can pass through the channel more smoothly, reducing unnecessary energy loss, reducing flow resistance, and improving the transmission efficiency of the fluid. At the same time, compared with sharp connections, the arc design can significantly reduce the generation of eddy currents. Eddy currents can cause waste of fluid energy and local pressure fluctuations, and may even cause additional scouring and wear on the channel wall. By reducing eddy currents, not only the flow efficiency of the fluid is improved, but also the risk of damage to the channel structure is reduced.

[0107] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0108] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive.

[0109] Inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "including a..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A steam generator with an axial preheater, characterized in that: include: A pressure-bearing shell, a heat transfer tube, a tube sheet, a partition plate, an inner sleeve and an outer sleeve, the tube sheet is arranged in the pressure-bearing shell and forms an accommodating cavity with the pressure-bearing shell, the heat transfer tube, the partition plate, the inner sleeve and the outer sleeve are all located in the accommodating cavity, both ends of the heat transfer tube are arranged on the tube sheet, the middle part of the heat transfer tube is arranged in the inner sleeve to form a tube bundle area, the outer sleeve is sleeved on the outside of the inner sleeve, the bottom of the partition plate is connected to the tube sheet, both sides of the partition plate pass through the inner sleeve and are connected to both sides of the outer sleeve, a cold side descending channel is formed between the inner sleeve, the outer sleeve and the partition plate, both ends of the cold side descending channel are respectively connected to the accommodating cavity and the tube bundle area, and the pressure-bearing shell is provided with a main water supply port connected to the cold side descending channel.

2. The steam generator with axial preheater according to claim 1, characterized in that: The cold side descending channel is an annular cavity, and the arc of the annular cavity is 40° to 160°.

3. The steam generator with axial preheater according to claim 1, characterized in that: One end of the inner sleeve is conically arranged, one end of the outer sleeve extends to one end of the inner sleeve, and a first communication port communicating with the accommodating cavity is provided between one end of the outer sleeve and one end of the inner sleeve.

4. The steam generator with axial preheater according to claim 3, characterized in that: The other end of the outer sleeve extends to the tube sheet, and a second communication port communicating with the tube bundle area is provided between the other end of the outer sleeve and the other end of the inner sleeve.

5. The steam generator with axial preheater according to claim 3, characterized in that: It also includes a flow limiting member, on which a plurality of flow limiting hole groups are arranged. The flow limiting member is arranged in the cold side descending channel and is located near the first connecting port.

6. The steam generator with axial preheater according to claim 5, characterized in that: A plurality of groups of the flow limiting hole groups are arranged around the center of the inner sleeve, each group of the flow limiting hole groups includes a plurality of flow limiting holes, and the spacing between adjacent flow limiting holes in each group of the flow limiting hole groups is the same.

7. The steam generator with axial preheater according to claim 1, characterized in that: Also includes: A heat-insulating sleeve, wherein the heat-insulating sleeve is arranged between the outer sleeve and the inner wall of the main water supply port.

8. The steam generator with axial preheater according to claim 1, characterized in that: The inner sleeve is provided with a water flow dispersion portion, and the water flow dispersion portion is arranged corresponding to the main water supply port.

9. The steam generator with axial preheater according to claim 8, characterized in that: The cross section of the water flow dispersion portion is conical.

10. The steam generator with axial preheater according to claim 8, characterized in that: The water flow dispersion part is provided with a plurality of dispersion protrusion structures.

11. The steam generator with axial preheater according to claim 1, characterized in that: Also includes: A flow distributor is provided with a plurality of distribution through holes, and the flow distributor is arranged in the cold side descending channel so that the velocity distribution of the fluid in the cold side descending channel entering the tube bundle area is uniform.

12. The steam generator with axial preheater according to claim 11, characterized in that: The flow distribution component is located below the main water supply port.

13. The steam generator with axial preheater according to claim 11, characterized in that: A plurality of distribution through holes are arranged at intervals around the center of the inner sleeve, and the spacing between adjacent distribution through holes is the same.

14. The steam generator with axial preheater according to claim 1, characterized in that: The cold side descending channel is provided with a baffle plate located above the main water supply port for blocking the upward flow of the fluid flowing out of the main water supply port.

15. The steam generator with axial preheater according to claim 14, characterized in that: The inner sleeve is provided with an opening, and the opening is located above the baffle.

16. The steam generator with axial preheater according to claim 15, characterized in that: The height of the bottom of the opening is greater than the height of the baffle.

17. The steam generator with axial preheater according to claim 15, characterized in that: It also includes a mixing device, which is arranged in the inner sleeve and corresponds to the opening.

18. The steam generator with axial preheater according to claim 1, characterized in that: The cross-sectional area of ​​the cold side descending channel decreases from both ends to the middle.

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