Asymmetric composite runner plate heat exchanger

Abstract

The invention provides an asymmetric composite runner plate heat exchanger, and belongs to the field of heat exchange equipment. The problems that in a fourth-generation lead-cooled fast reactor, when a hot working medium exchanges heat with a cold working medium, the pressure drop is too large, a micro-channel is prone to being blocked, and the heat exchange efficiency is low are solved. Comprising a plurality of heat exchange units which are arranged in a stacked mode, a shell is arranged outside the heat exchange units which are arranged in a stacked mode, each heat exchange unit comprises an upper cold plate, a lower cold plate and a hot plate which are arranged from top to bottom, the upper cold plates and the lower cold plates are arranged in a mirror symmetry mode, and arc-shaped channels are correspondingly formed in the bottom faces of the upper cold plates and the top faces of the lower cold plates. After the upper cold plate and the lower cold plate are connected, the arc-shaped channels are in butt joint to form a cold working medium channel with an oval section, the cold working medium channel is of a snakelike structure, the hot plate is provided with a plurality of parallel straight channels to form a hot working medium channel, and the section size of the hot working medium channel is larger than that of the cold working medium channel. And the flowing directions of the cold working medium channel and the hot working medium channel are crossed.

Description

Technical Field

[0001] This invention belongs to the field of novel nuclear power system heat exchange equipment, and in particular relates to an asymmetric composite flow channel plate heat exchanger. Background Technology

[0002] In the nuclear energy industry, efficient and reliable heat exchange between the primary and secondary loops of a reactor is crucial for ensuring the safe and economical operation of the system. For advanced nuclear energy systems such as the fourth-generation lead-cooled fast reactor, high-temperature lead-bismuth alloys are often used as coolants in the primary loop, while supercritical carbon dioxide is preferred in the secondary loop to improve the thermodynamic cycle efficiency. However, lead-bismuth alloys and supercritical carbon dioxide have significant differences in physical properties. Lead-bismuth alloys have high viscosity and strong thermal conductivity, and their heat exchange mechanism is mainly based on boundary layer heat conduction, requiring the flow channel to have a low pressure drop along the flow path to avoid excessive pumping power. Supercritical carbon dioxide, on the other hand, needs to enhance turbulence at high flow rates to achieve excellent convective heat transfer. This huge difference in the characteristics of the working fluids puts forward asymmetrical and contradictory requirements for the flow channel design of the heat exchanger, making it difficult for traditional symmetrical flow channel heat exchangers to meet both requirements, which has become a technical problem that urgently needs to be solved in this field.

[0003] To address the aforementioned heat exchange challenges, some solutions have been proposed in the prior art. For example, Chinese patent CN115307464A discloses a printed plate heat exchanger core and heat exchanger, which presents a heat exchange scheme using etched flow channels. This scheme achieves heat transfer to a certain extent by forming a specific flow channel structure on the working fluid side using an etching process. However, due to the limitations of the etching process itself, the resulting flow channel structure is often relatively complex with many variations in the flow channel cross-section. When applied to lead-bismuth alloy working fluids, this complex flow channel structure can lead to unnecessary flow resistance and excessive pressure drop along the flow path. This not only increases the load on the reactor primary loop main pump and affects the energy utilization efficiency of the entire system, but also makes it difficult to fully utilize the thermal conductivity advantages of the lead-bismuth alloy boundary layer.

[0004] Chinese patent CN222104475U describes a compact plate heat exchanger, proposing a microchannel design scheme. This scheme incorporates microchannels on both the cold and hot working fluid sides to enhance heat transfer. While the microchannel design increases the specific surface area and improves heat transfer intensity, the channel size is extremely small. For lead-bismuth alloys, the tiny channel size makes them highly susceptible to flow obstruction or even complete blockage due to trace impurities or solidification risks in the working fluid, posing a high safety risk and significantly limiting the practical application of this technology in the harsh conditions of lead-cooled fast reactors. Furthermore, the simple microchannel design is insufficient in meeting the heat transfer requirements of high-velocity supercritical carbon dioxide, and its enhancement effect on convective heat transfer is limited.

[0005] Chinese patent CN118965465A discloses a thermal design method for a multi-flow diffusion-welded compact plate heat exchanger, specifically a symmetrical flow channel design. This design is effective in some conventional heat exchange scenarios with similar working fluid characteristics. However, when faced with a special working fluid pairing such as lead-bismuth alloy and supercritical carbon dioxide, its symmetrical flow channel structure cannot simultaneously meet the drastically different pressure drop and heat exchange requirements on both sides. If the flow channel design is biased towards adapting to the low pressure drop requirement of lead-bismuth alloy, the heat exchange efficiency on the supercritical carbon dioxide side will be compromised. Conversely, if priority is given to meeting the high-efficiency heat exchange of supercritical carbon dioxide, the flow pressure drop on the lead-bismuth alloy side will increase sharply, resulting in low overall efficiency of the heat exchanger using a symmetrical flow channel, making it difficult to meet the high-performance requirements of advanced nuclear energy systems for heat exchange equipment. Summary of the Invention

[0006] In view of this, the present invention aims to propose an asymmetric composite flow channel plate heat exchanger to solve the technical problems of excessive pressure drop, easy blockage of microchannels and low heat exchange efficiency in traditional schemes when heat exchange occurs between hot and cold working fluids in fourth-generation lead-cooled fast reactors.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: an asymmetric composite flow channel plate heat exchanger, comprising a shell and multiple sets of stacked heat exchange units. The shell surrounds the stacked heat exchange units and has a cold working fluid inlet, a cold working fluid outlet, a hot working fluid inlet, and a hot working fluid outlet. Each heat exchange unit includes an upper cooling plate, a lower cooling plate, and a hot plate arranged from top to bottom. The upper and lower cooling plates are mirror-symmetrically arranged. Arc-shaped channels are correspondingly provided on the bottom surface of the upper cooling plate and the top surface of the lower cooling plate. After being connected to the lower cold plate, the arc-shaped channels are joined to form an elliptical cross-section cold working medium channel. The cold working medium channel has a serpentine structure. Multiple parallel direct current channels are provided on the hot plate to form a hot working medium channel. The cross-sectional dimension of the hot working medium channel is larger than that of the cold working medium channel. The flow directions of the cold working medium channel and the hot working medium channel are cross-shaped. The cold working medium inlet is connected to the inlet of the cold working medium channel, the cold working medium outlet is connected to the outlet of the cold working medium channel, the hot working medium inlet is connected to the inlet of the hot working medium channel, and the hot working medium outlet is connected to the outlet of the hot working medium channel.

[0008] Furthermore, the hot plate includes hot plate partitions and hot plate pressure-bearing sections. Multiple hot plate partitions are equally spaced between two hot plate pressure-bearing sections. The hot plate partitions and hot plate pressure-bearing sections are independent discrete structures that form a heat transfer fluid channel.

[0009] Furthermore, the cross-section of the cold working fluid channel has a major axis length of 2 mm and a minor axis length of 1.5 mm.

[0010] Furthermore, the cross-section of the thermal fluid channel is rectangular, with dimensions of 10mm × 3mm.

[0011] Furthermore, the upper cooling plate, lower cooling plate, and hot plate are all made of stainless steel.

[0012] Furthermore, the upper and lower cold plates are connected by a diffusion welding process.

[0013] Furthermore, both the upper and lower cooling plates include an etched channel area and a pressure-bearing section, with the pressure-bearing section located around the etched channel area.

[0014] Furthermore, the cold working medium is supercritical carbon dioxide, and the hot working medium is a lead-bismuth alloy.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs an asymmetric flow channel configuration. Targeting the characteristics of the hot-side working fluid, lead-bismuth alloy, the flow channel utilizes a discrete parallel direct-flow channel with a large cross-sectional area. This perfectly adapts to the heat transfer mechanism of lead-bismuth alloy, which is primarily based on boundary layer heat conduction, providing a path with low flow resistance. This significantly reduces pressure drop along the flow path, fully meeting the design requirements of the reactor primary loop for low pumping power. Targeting the characteristics of the cold-side working fluid, supercritical carbon dioxide, the flow channel employs an elliptical serpentine microchannel with a smaller cross-sectional area. The serpentine structure effectively disrupts the flow boundary layer, enhancing the turbulence of the working fluid and thus significantly improving the heat transfer coefficient. Its heat transfer effect is superior to the simple straight-channel scheme. Because a sufficiently large direct-flow channel is provided for the lead-bismuth alloy side, the major safety hazard of easy blockage due to excessively small microchannels is fundamentally avoided. 2. The hot plate of this invention adopts a discrete design, that is, the hot plate partition and the pressure-bearing section are independent components, which are assembled through process-aided structures. This structure avoids the complex continuous flow channels formed by integral etching or stamping, fundamentally eliminating the risk of local blockage of the flow channels due to working fluid deposition or phase change, and greatly improving the reliability of long-term operation. The upper and lower cooling plates of this invention are connected by diffusion welding technology. This solid-phase connection process can form a uniform and high-strength integral structure, thereby forming a robust pressure-bearing section, which can withstand the high-pressure conditions of supercritical carbon dioxide in the secondary loop. Its pressure-bearing capacity and structural integrity are superior to the multi-process welding structure. The metallurgical bonding between the plates is achieved through diffusion welding, without the need for additional welding materials, making the structure of the heat exchange unit more compact and optimizing the overall size and weight of the equipment. 3. This invention enables the overall flow of hot and cold working fluids in a cross-shaped manner, and combines the principle of counter-current heat exchange in local areas. This allows for more efficient use of the entire heat exchange plate area, significantly improving the utilization rate of the heat exchange area and thus enhancing the overall heat transfer efficiency. The cold working fluid flows in the serpentine channel, which effectively extends the heat exchange path and further enhances heat exchange. This smooth serpentine bending design can effectively avoid the problems of local eddies and sudden pressure drop at the point of abrupt change in flow direction, making the flow more stable, the pressure drop distribution more uniform, and improving the stability of operation. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the axial structure of an asymmetric composite flow channel plate heat exchanger according to the present invention; Figure 2 This is a schematic diagram of the axial structure of multiple stacked heat exchange units in an asymmetric composite flow channel plate heat exchanger according to the present invention. Figure 3 This is an exploded structural diagram of the heat exchange unit of an asymmetric composite flow channel plate heat exchanger according to the present invention. Figure 4 This is a top view of the cold plate structure of an asymmetric composite flow channel plate heat exchanger according to the present invention. Figure 5 This is a top view of the heat plate structure of an asymmetric composite flow channel plate heat exchanger according to the present invention.

[0017] In the picture: 1. Cold working fluid inlet; 2. Cold working fluid outlet; 3. Hot working fluid outlet; 4. Hot working fluid inlet; 5. Upper cold plate; 6. Lower cold plate; 7. Hot plate; 8. Cold working fluid channel; 9. Hot working fluid channel; 10. Hot plate partition; 11. Hot plate pressure section; 12. Etched channel area; 13. Pressure section. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0019] Detailed implementation method: See Figure 1-5This embodiment describes an asymmetric composite flow channel plate heat exchanger, comprising a shell and multiple stacked heat exchange units. The shell surrounds the stacked heat exchange units and has a cold working fluid inlet 1, a cold working fluid outlet 2, a hot working fluid inlet 4, and a hot working fluid outlet 3. The shell provides a cavity for the internal stacked heat exchange units and provides pressure-bearing and external interface connection functions, ensuring that the cold and hot working fluids flow in their respective independent flow channels. The external interfaces facilitate the introduction and export of the working fluids. The heat exchange units are used to handle the cold and hot working fluids. The heat transfer between them, and the superposition of multiple heat exchange units can increase the total effective heat exchange area, thereby meeting the reactor system's requirement for large heat exchange capacity; each heat exchange unit includes an upper cooling plate 5, a lower cooling plate 6, and a hot plate 7 arranged from top to bottom. The upper cooling plate 5 and the lower cooling plate 6 are arranged in a mirror symmetrical manner. The bottom surface of the upper cooling plate 5 and the top surface of the lower cooling plate 6 are respectively provided with arc-shaped channels. After the upper cooling plate 5 and the lower cooling plate 6 are connected, the arc-shaped channels are joined to form an elliptical cross-section cold working fluid channel 8. The cold working fluid channel 8 has a serpentine structure. The cold working medium channel can extend the flow path of the cold working medium within a limited space, thereby increasing the heat exchange time and heat exchange efficiency. The elliptical cross-sectional shape helps optimize flow characteristics. Multiple parallel straight channels are arranged on the hot plate 7 to form hot working medium channels 9. These hot working medium channels 9 are straight flow channels, thereby minimizing the flow resistance of the hot working medium and reducing pressure drop along the flow path. The cross-sectional dimensions of the hot working medium channels 9 are larger than those of the cold working medium channels 8, thus meeting different pressure drop and heat exchange requirements. The flow directions of the cold working medium channels 8 and 9 are... The flow path is cross-shaped, meaning the overall flow directions of the hot and cold working fluids are perpendicular to each other in the planar interior. This cross-flow can disrupt their respective thermal boundary layers, enhance fluid mixing and turbulence, thereby improving the heat transfer coefficient. The cold working fluid inlet 1 is connected to the inlet of the cold working fluid channel 8, the cold working fluid outlet 2 is connected to the outlet of the cold working fluid channel 8, the hot working fluid inlet 4 is connected to the inlet of the hot working fluid channel 9, and the hot working fluid outlet 3 is connected to the outlet of the hot working fluid channel 9, ensuring that the cold and hot working fluids can effectively exchange heat throughout the entire heat exchange unit according to the preset cross-flow path.

[0020] The hot plate 7 includes hot plate partitions 10 and hot plate pressure-bearing sections 11. Multiple hot plate partitions 10 are equally spaced between two hot plate pressure-bearing sections 11. Adjacent hot plate partitions 10 define the width and length of the working fluid channel 9, providing a boundary for the flow of the working fluid. The hot plate pressure-bearing sections 11 are used to withstand pressure to maintain the stability of the structure. The hot plate partitions 10 and hot plate pressure-bearing sections 11 are independent discrete structures forming the working fluid channel 9. The discrete structure avoids complex internal flow channels, fundamentally reducing the risk of flow channel blockage caused by impurity deposition or phase change in the working fluid, and improving the operational safety of the equipment.

[0021] The cross-section of the cold working medium channel 8 has a major axis length of 2 mm and a minor axis length of 1.5 mm, which ensures that enough flow channels can be arranged on a given cold plate area, thereby providing a huge total heat exchange area, which is the basis for achieving efficient and compact heat exchange.

[0022] The heat transfer medium channel 9 has a rectangular cross-section with dimensions of 10mm × 3mm, ensuring that the channel has a sufficiently large flow cross-section, significantly reducing the frictional resistance of the fluid, and effectively avoiding the risk of poor flow or even blockage caused by trace impurities in the working medium or local temperature fluctuations. This enhances the overall heat exchange effect and greatly improves operational reliability.

[0023] The upper cooling plate 5, lower cooling plate 6, and hot plate 7 are all made of stainless steel, which can simultaneously meet the requirements of high temperature corrosion resistance, high pressure resistance, compatibility with key welding processes, and ensure nuclear-grade safety and reliability.

[0024] The upper cold plate 5 and the lower cold plate 6 are connected by diffusion welding process to achieve the requirements of high pressure sealing, geometric conformity, overall pressure bearing and stable material properties.

[0025] Both the upper cooling plate 5 and the lower cooling plate 6 include an etched channel area 12 and a pressure-bearing section 13. The pressure-bearing section 13 is located around the etched channel area 12. The etched channel area 12 is used to directly form millimeter-level arc-shaped channels on the stainless steel plate through precision processing techniques such as chemical etching or photolithography. When the upper cooling plate 5 and the lower cooling plate 6 are aligned and joined, these corresponding arc-shaped channels form a serpentine flow channel 8 for the cooling medium, thereby guiding the cooling medium and exchanging heat. The pressure-bearing section 13 refers to the solid frame area around the etched channel area 12 on the cooling plate that is not etched and maintains the original thickness and integrity of the plate. The pressure-bearing section 13 is used to provide the main mechanical strength and pressure bearing capacity, and can effectively withstand and disperse the high-pressure load from the internal cooling medium, preventing the upper cooling plate 5 and the lower cooling plate 6 from bulging or deforming under pressure. It is the structural basis for ensuring the safe and stable operation of the heat exchanger under high-pressure conditions, so that the upper cooling plate 5 and the lower cooling plate 6 can simultaneously meet the requirements of precision flow heat exchange and high-pressure reliable bearing.

[0026] The cooling medium is supercritical carbon dioxide, and the heating medium is a lead-bismuth alloy. The lead-bismuth alloy, as the primary coolant of the reactor, has the significant characteristics of high boiling point, good neutron performance and heat carrying capacity. The supercritical carbon dioxide, as the secondary working medium, has the advantages of high density, low viscosity and excellent flow and heat transfer characteristics near the critical point, which can achieve efficient thermodynamic cycle.

[0027] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. An asymmetric composite flow channel plate heat exchanger, characterized in that: The device includes an outer shell and multiple stacked heat exchange units. The outer shell covers the multiple stacked heat exchange units and has a cold working fluid inlet (1), a cold working fluid outlet (2), a hot working fluid inlet (4), and a hot working fluid outlet (3). Each heat exchange unit includes an upper cooling plate (5), a lower cooling plate (6), and a hot plate (7) arranged from top to bottom. The upper cooling plate (5) and the lower cooling plate (6) are mirror-symmetrically arranged. The bottom surface of the upper cooling plate (5) and the top surface of the lower cooling plate (6) are respectively provided with arc-shaped channels. After the upper cooling plate (5) and the lower cooling plate (6) are connected, the arc-shaped channels are joined to form an elliptical cross-section. The cold working medium channel (8) has a serpentine structure. The hot plate (7) is provided with multiple parallel direct current channels to form a hot working medium channel (9). The cross-sectional size of the hot working medium channel (9) is larger than that of the cold working medium channel (8). The flow directions of the cold working medium channel (8) and the hot working medium channel (9) are cross-shaped. The cold working medium inlet (1) is connected to the inlet of the cold working medium channel (8), the cold working medium outlet (2) is connected to the outlet of the cold working medium channel (8), the hot working medium inlet (4) is connected to the inlet of the hot working medium channel (9), and the hot working medium outlet (3) is connected to the outlet of the hot working medium channel (9).

2. The asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The hot plate (7) includes a hot plate partition (10) and a hot plate pressure bearing section (11). Multiple hot plate partitions (10) are equally spaced between two hot plate pressure bearing sections (11). The hot plate partitions (10) and the hot plate pressure bearing sections (11) are independent discrete structures forming a heat working fluid channel (9).

3. The asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The cross-section of the cold working medium channel (8) has a major axis length of 2 mm and a minor axis length of 1.5 mm.

4. An asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The cross-section of the thermal fluid channel (9) is rectangular, with a cross-sectional size of 10mm × 3mm.

5. An asymmetric composite flow channel plate heat exchanger according to claim 3, characterized in that: The upper cooling plate (5), lower cooling plate (6), and hot plate (7) are all made of stainless steel.

6. An asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The upper cold plate (5) and the lower cold plate (6) are connected by diffusion welding process.

7. An asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The upper cooling plate (5) and the lower cooling plate (6) both include an etched channel area (12) and a pressure-bearing section (13), with the pressure-bearing section (13) located around the etched channel area (12).

8. An asymmetric composite flow channel plate heat exchanger according to claim 1, characterized in that: The cold working medium is supercritical carbon dioxide, and the hot working medium is a lead-bismuth alloy.

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