Passive residual heat removal system containing phase change energy storage condensation water hammer inhibition

Abstract

The invention discloses a phase change energy storage-containing passive residual heat removal system for inhibiting a condensed water hammer. The passive residual heat removal system comprises a passive heat exchange tube bundle, an inlet tube, a containment shell, a discharge tube, a phase change material energy storage device and a floating platform wall surface, the passive heat exchange tube bundle is arranged in the containment shell, an inlet and an outlet of the passive heat exchange tube bundle are respectively connected with an inlet tube and a discharge tube, and the wall surface of the floating platform is connected with the inlet tube and the discharge tube; the phase-change material energy storage device is installed on the upper half portion of the discharge pipe, and after saturated steam floating on the upper half portion of the discharge pipe makes contact with the phase-change material energy storage device for heat exchange, the content of the saturated steam is reduced, and formed steam clusters are reduced. The phase-change material energy storage device is arranged on the discharge pipe of the passive heat exchanger to condense and cool high-temperature steam, so that the proportion and strength of direct contact condensation of the steam and supercooled seawater are reduced, the occurrence of water hammers is inhibited, the flow resistance of the device is not increased, and the stability and residual heat discharge capacity of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the technical fields of heat transfer and fluid mechanics, and specifically relates to a waste heat removal system that condenses and cools high-temperature steam by arranging a phase change material energy storage device on the discharge pipe of a passive heat exchanger, thereby suppressing water hammer induced by direct condensation of steam and supercooled water. Background Art

[0002] In passive waste heat removal systems on offshore nuclear platforms, such as floating nuclear power plants, the limited space and direct use of the ocean as a heat sink necessitate significantly reduced riser lengths, or even the elimination of these systems. Consequently, passive waste heat removal systems exhibit contoured height differences. Concave height differences in systems are prone to flow instability due to insufficient natural circulation driving force. In the horizontal discharge pipes of passive heat exchangers, under the influence of the inertia and buoyancy of the high-temperature steam, supercooled seawater flows back into the pipes, surrounding the steam and forming a steam mass. Direct contact and condensation of the steam mass with the supercooled seawater causes it to collapse, inducing water hammer and generating large local pressure peaks that can destructively impact the pipe's structural function.

[0003] Existing solutions for suppressing water hammer caused by steam condensation within pipes are limited. Most rely on modifying the internal pipe geometry, which undoubtedly increases the system's flow resistance. Furthermore, since the flow characteristics of passive systems are sensitive to resistance, such solutions can degrade the performance of waste heat removal systems. Therefore, finding a method to suppress water hammer caused by steam condensation without increasing pipe flow resistance is of great significance for related industrial applications. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a passive waste heat removal system with condensation water hammer suppression containing phase change energy storage. The system innovatively combines a phase change material energy storage device with a passive waste heat removal system, suppressing water hammer induced by direct contact condensation between steam and supercooled seawater in height-difference passive waste heat removal systems such as marine nuclear platforms, thereby improving the stability of the system and the waste heat removal capacity.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A passive waste heat removal system for condensation water hammer suppression with phase change energy storage includes: a passive heat exchange tube bundle 1, placed in a containment shell 3, absorbing waste heat in the containment shell 3 through natural circulation; an inlet pipe 2, connected to the inlet of the passive heat exchange tube bundle 1, for introducing seawater as a cooling medium; a discharge pipe 4, connected to the outlet of the passive heat exchange tube bundle 1, for discharging the medium after absorbing heat; a phase change material energy storage device 5, fixed to the outer wall of the upper half of the discharge pipe 4, condensing and cooling the saturated steam in the discharge pipe through outer wall contact heat exchange; a floating platform wall 6, connected to the inlet pipe 2 and the discharge pipe 4, so that the system is directly connected to the marine environment; wherein, the phase change material energy storage device 5 reduces the content of saturated steam by absorbing the heat of saturated steam, suppresses the water hammer phenomenon induced by direct contact condensation of steam and supercooled seawater, and does not change the original flow channel structure and natural circulation resistance characteristics of the discharge pipe 4.

[0007] The passive heat exchange tube bundle 1 adopts a multi-tube structure to increase the heat exchange area and improve the heat exchange efficiency.

[0008] The passive heat exchange tube bundle 1 is connected to the discharge pipe 4 through an arc-shaped transition, and the curvature radius of the transition section is ≥ 3 times the pipe diameter to reduce local flow resistance.

[0009] The inlet pipe 2 and the outlet pipe 4 are both provided with valves for controlling the start and stop of the system.

[0010] The phase change material energy storage device 5 includes: a phase change material energy storage device shell 5-2, which is semi-cylindrical and fixed to the outer wall of the upper half of the discharge pipe 4 by welding; a phase change material 5-3, which is filled in the phase change material energy storage device shell; a partition 5-1, which is welded at equal distances along the outer wall of the discharge pipe 4 and has a semi-annular shape, and divides the phase change material 5-3 in the phase change material energy storage device shell into independent blocks to prevent uneven distribution of the material due to ocean movement.

[0011] The phase change material 5-3 is a solid-liquid phase change material, and is an alloy phase change material with high thermal conductivity, a thermal conductivity of not less than 14W / (m·K), and a volume latent heat of not less than 200MJ / m 3 .

[0012] The phase change material energy storage device housing 5 - 2 is provided with a monitoring device for real-time monitoring of the temperature and state of the phase change material 5 - 3 .

[0013] A sealing device is provided between the phase change material energy storage device housing 5 - 2 and the discharge pipe 4 to prevent leakage.

[0014] The outer wall of the upper half of the discharge pipe 4 is provided with a heat conduction enhancement structure, including a corrugated surface or fins, to improve the heat exchange efficiency between the phase change material energy storage device 5 and the discharge pipe 4 .

[0015] During operation of the passive waste heat removal system, the seawater in the heat exchange tube bundle absorbs waste heat. At high heat exchange rates, saturated steam forms within the discharge tube. Due to its low density, saturated steam floats in the upper region of the discharge tube. The phase change material energy storage device located in the upper region exchanges heat with the saturated steam within the tube, condensing and cooling it. This reduces the proportion and intensity of direct condensation between the steam and supercooled seawater, thereby suppressing water hammer and improving system stability and waste heat removal capabilities.

[0016] Phase change material energy storage offers advantages such as high energy storage density, compact size, a wide range of phase change temperature options, and fast response, enabling efficient and rapid heat absorption. This invention incorporates a phase change material energy storage device on the discharge pipe of a passive heat exchanger to condense and cool high-temperature steam, thereby suppressing water hammer caused by direct contact and condensation between steam and supercooled water. Compared to existing technologies, this invention offers the following advantages:

[0017] The present invention is an improvement and innovation made to the existing technology. The current non-passive waste heat removal system with equal height difference is prone to water hammer induced by direct contact condensation between steam and supercooled seawater in the discharge pipe. The huge pressure peak generated has a destructive effect on the structure and function of the pipeline, and the stability of the system and the waste heat removal capacity are greatly reduced. The present invention adopts the method of setting a phase change material energy storage device in the discharge pipe to exchange heat with the saturated steam in the pipe to condense and cool it, thereby reducing the proportion and intensity of direct contact condensation between steam and supercooled seawater, thereby suppressing the occurrence of water hammer. In addition, the phase change material energy storage device does not change the original internal pipeline structure, so it will not increase the natural circulation flow resistance. Therefore, the invention can effectively suppress the occurrence of water hammer induced by steam condensation in the non-passive waste heat removal system, improve the stability and waste heat removal capacity of the system, and has important engineering application value.

[0018] 1. The present invention innovatively combines a phase change material energy storage device with a passive waste heat removal system. This design can effectively suppress the occurrence of water hammer caused by condensation caused by direct contact between steam and supercooled seawater in passive waste heat removal systems with high elevation differences, such as those on offshore nuclear platforms.

[0019] 2. Phase change materials condense and cool saturated steam, reducing the content of saturated steam, thereby reducing the proportion and intensity of direct contact condensation between steam and supercooled seawater.

[0020] 3. By setting up partitions in the phase change material energy storage device, there will be no accumulation after the phase change material absorbs heat and melts, which can effectively reduce the degree of uneven distribution caused by the influence of ocean conditions.

[0021] 4. The phase change material energy storage device is arranged in the upper part of the discharge pipe to condense and cool the saturated steam generated by the passive heat exchange tube bundle. The shell of the phase change material energy storage device can discharge the waste heat absorbed by the phase change material. The phase change material using solid-liquid phase change has a small volume change, which is suitable for the narrow space of the floating nuclear platform.

[0022] 5. The phase change material energy storage device adopts an outer wall contact heat exchange design and is installed on the outside of the discharge pipe. It does not change the original geometric structure of the flow channel in the pipe, thereby not increasing the natural circulation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the passive waste heat removal system for condensation water hammer suppression with phase change energy storage according to the present invention.

[0024] Figure 2 This is a schematic structural diagram of the phase change material energy storage device of the passive waste heat removal system for condensation water hammer suppression containing phase change energy storage of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 and Figure 2 As shown, the passive heat removal system for condensate hammer suppression with phase change energy storage includes a passive heat exchange tube bundle 1, an inlet pipe 2, a containment shell 3, a discharge pipe 4, a phase change material energy storage device 5, and a floating platform wall 6. The passive heat exchange tube bundle 1 is located within the containment shell 3. The inlet pipe 2 and the discharge pipe 4 are connected to the passive heat exchange tube bundle 1 through the containment shell 3. Their other ends are directly connected to the seawater through the floating platform wall 6. Valves for the start-stop system are installed on the inlet pipe 2 and the discharge pipe 4. The passive heat exchange tube bundle 1 and the discharge pipe 4 are connected by an arc-shaped transition with a curvature radius of ≥3 times the pipe diameter to reduce local flow resistance.

[0027] like Figure 1 and Figure 2As shown, the phase change material energy storage device 5 includes a phase change material energy storage device shell 5-2 connected to the discharge pipe 4, a phase change material 5-3 filled therein, and a partition 5-1 that divides the phase change material at different positions into blocks. The phase change material energy storage device shell 5-2 is connected to the discharge pipe 4 by welding. Its structure is a semi-cylindrical shape. It is arranged in the upper half of the discharge pipe 4 and seals the phase change material 5-3 therein. The partition 5-1 is welded and arranged at equal distances along the outside of the discharge pipe 4. It has a semi-annular shape and is also connected to the phase change material energy storage device shell 5-2 by welding. In addition to dividing the phase change material 5-3, it also plays a role in strengthening the fixed structure. The phase change material 5-3 filled therein adopts an alloy phase change material with high thermal conductivity whose phase change process is solid-liquid phase change. The thermal conductivity is not less than 14W / (m·K) and the volume latent heat is not less than 200MJ / m 3 The upper outer wall of the discharge pipe 4 is provided with a heat conduction enhancement structure, including a corrugated surface or fins. A monitoring device is provided on the phase change material energy storage device housing 5-2 for real-time monitoring of the temperature and state of the phase change material 5-3. A sealing device is provided between the housing 5-2 and the discharge pipe 4 to prevent leakage.

[0028] The saturated steam and water mixture generated by the passive heat exchange tube bundle 1 enters the discharge pipe 4. Due to its low density, the saturated steam floats in the upper half of the discharge pipe 4, exchanging heat directly with the phase change material energy storage device 5. The phase change material 5-3 absorbs a significant amount of heat from the saturated steam, condensing it and cooling it. This reduces the saturated steam content, thereby reducing the backflow of supercooled seawater into the discharge pipe 4. Ultimately, this reduces the formation of steam clusters surrounded by supercooled water surrounding the saturated steam and suppresses the occurrence of water hammer. The other end of the phase change material 5-3 is connected to the phase change material energy storage device housing 5-2, slowly dissipating the absorbed waste heat and maintaining a stable temperature. The partition 5-1 reduces the accumulation of melted phase change material 5-3 under ocean motion conditions, ensuring uniform distribution within the phase change material energy storage device 5.

[0029] The operation process of the passive waste heat removal system with condensation water hammer suppression and phase change energy storage is as follows:

[0030] When the system begins operation, seawater enters the passive heat exchange tube bundle 1 through the inlet pipe 2. The seawater absorbs waste heat, raising its temperature. Natural circulation begins under the influence of density differences. As the heat load on the passive heat exchange tube bundle 1 increases, the seawater enters the outlet pipe 4 as a mixture of saturated steam and water. The saturated steam floats on the upper half of the outlet pipe 4, where it condenses and cools after heat exchange with the phase change material energy storage device 5. This reduces the saturated steam content and the resulting steam clusters, thereby reducing the proportion and intensity of condensation caused by direct contact between steam and supercooled seawater, thereby suppressing the occurrence of water hammer. This improves the system's stability and waste heat removal capabilities.

Claims

1. A passive waste heat removal system for condensation water hammer suppression with phase change energy storage, characterized by: include: The passive heat exchange tube bundle (1) is placed in the containment shell (3) and absorbs the residual heat in the containment shell (3) through natural circulation; An inlet pipe (2) is connected to the inlet of the passive heat exchange tube bundle (1) and is used to introduce seawater as a cooling medium; a discharge pipe (4) is connected to the outlet of the passive heat exchange tube bundle (1) and is used to discharge the medium after absorbing heat; a phase change material energy storage device (5) is fixed to the outer wall of the upper half of the discharge pipe (4) and condenses and cools the saturated steam in the discharge pipe through outer wall contact heat exchange; a floating platform wall (6) is connected to the inlet pipe (2) and the discharge pipe (4) so that the system is directly connected to the marine environment; wherein the phase change material energy storage device (5) reduces the content of saturated steam by absorbing the heat of saturated steam, suppresses the water hammer phenomenon induced by the direct contact condensation of steam and supercooled seawater, and does not change the original flow channel structure and natural circulation resistance characteristics of the discharge pipe (4).

2. The passive residual heat removal system according to claim 1, characterized in that: The passive heat exchange tube bundle (1) adopts a multi-tube structure to increase the heat exchange area and improve the heat exchange efficiency.

3. The passive residual heat removal system according to claim 1, characterized in that: The passive heat exchange tube bundle (1) is connected to the discharge pipe (4) through an arc-shaped transition, and the curvature radius of the transition section is ≥3 times the pipe diameter, so as to reduce local flow resistance.

4. The passive residual heat removal system according to claim 1, characterized in that: The inlet pipe (2) and the outlet pipe (4) are both provided with valves for controlling the start and stop of the system.

5. The passive residual heat removal system according to claim 1, characterized in that: The phase change material energy storage device (5) comprises: a phase change material energy storage device shell (5-2) in a semi-cylindrical shape, fixed to the outer wall of the upper half of the discharge pipe (4) by welding; a phase change material (5-3) filled in the phase change material energy storage device shell; and a partition (5-1) welded at equal intervals along the outer wall of the discharge pipe (4) in a semi-annular shape, which divides the phase change material (5-3) in the phase change material energy storage device shell into independent blocks to prevent uneven distribution of the material due to ocean movement.

6. The passive residual heat removal system according to claim 5, characterized in that: The phase change material (5-3) is a solid-liquid phase change material, and is an alloy phase change material with high thermal conductivity, a thermal conductivity of not less than 14W / (m·K), and a volume latent heat of not less than 200MJ / m 3 .

7. The passive residual heat removal system according to claim 5, characterized in that: A monitoring device is provided on the shell (5-2) of the phase change material energy storage device for real-time monitoring of the temperature and state of the phase change material (5-3).

8. The passive residual heat removal system according to claim 5, characterized in that: A sealing device is provided between the phase change material energy storage device housing (5-2) and the discharge pipe (4) to prevent leakage.

9. The passive residual heat removal system according to claim 1, characterized in that: The outer wall of the upper half of the discharge pipe (4) is provided with a heat conduction enhancement structure, including a corrugated surface or fins, to improve the heat exchange efficiency between the phase change material energy storage device (5) and the discharge pipe (4).

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