A high temperature heat exchanger

Abstract

The application discloses a high-temperature heat exchanger, and relates to the field of fuel cells, which comprises a shell, a first channel for flue gas flow, a second channel for fuel gas flow and a third channel for air flow are arranged in the shell, the first channel, the second channel and the third channel are isolated from each other, the second channel and the third channel are arranged in a spiral overlapping mode, the flue gas in the first channel is used for high-temperature heat exchange of the fuel gas in the second channel and the air in the third channel, and the application effectively solves the problem of excessive temperature difference between the fuel side and the air side at the inlet of the electric pile in a solid oxide fuel cell power generation system. Due to the spiral overlapping arrangement of the second channel and the third channel and the high-efficiency heat exchange of the flue gas, the fuel gas and the air can be heated to similar or the same temperature before entering the electric pile, so that the damage of thermal stress caused by the temperature difference to the electric pile is reduced, and the comprehensive thermal efficiency and the operation stability of the power generation system are improved.

Description

Technical Field

[0001] This invention relates to the technical field of fuel cells, and more specifically, to a high-temperature heat exchanger. Background Technology

[0002] A fuel cell is an electrochemical energy conversion device that directly converts chemical energy into electrical energy. Fuel cells are not limited by the Carnot cycle and, compared to traditional heat engines, have advantages such as high energy conversion efficiency (up to 50%-60%) and environmental friendliness (i.e., very low NOx, SO2, and noise emissions). Solid oxide fuel cells (SOFCs) are all-solid-state electrochemical energy conversion devices that utilize fuel efficiently and cleanly. SOFCs operate at reaction temperatures of 650-950℃ and the system can be divided into a fuel stack and peripheral auxiliary units.

[0003] The fuel cell stack is the core of an SOFC power generation system. It is a device that directly converts chemical energy into electrical energy. The peripheral auxiliary units surrounding the fuel cell stack system include an air supply system, a fuel supply system, a pure water supply system, a reforming reaction system, a burner system, a combustion flue gas heat exchange system, an electrical management system, and a control system.

[0004] The burner system is where the fuel-side anode exhaust gas and the air-side cathode exhaust gas are burned. In the prior art, the combustion flue gas is usually passed through the fuel-side and air-side high-temperature heat exchangers in sequence to heat the fuel and air before entering the SOFC stack to the temperature required for the SOFC reaction. However, in the above scheme, the temperature difference between the fuel-side and air-side at the stack inlet is large, which has an adverse effect on the stack performance.

[0005] In summary, how to make the fuel-side temperature and air-side temperature at the fuel stack inlet similar or even the same before entering the fuel stack, and reduce the thermal stress caused by the high temperature difference, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a high-temperature heat exchanger that effectively solves the problem of excessive temperature difference between the fuel side and the air side at the inlet of the solid oxide fuel cell power generation system, ensuring that the fuel and air are heated to similar or the same temperature before entering the fuel cell, reducing the thermal stress caused by the high temperature difference and the damage to the fuel cell, and improving the overall thermal efficiency and operational stability of the power generation system.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A high-temperature heat exchanger includes a shell, within which are provided a first channel for combustion flue gas flow, a second channel for fuel gas flow, and a third channel for air flow. The first channel, the second channel, and the third channel are isolated from each other. The second channel and the third channel are arranged in a spiral overlapping manner. The combustion flue gas in the first channel is used for high-temperature heat exchange with the fuel gas in the second channel and the air in the third channel.

[0009] Preferably, the second channel includes a fuel-side inlet and a fuel-side outlet that are respectively opened on the housing, and the third channel includes an air-side inlet and an air-side outlet that are respectively opened on the housing.

[0010] Preferably, the fuel-side inlet and the air-side inlet are located on the same side of the housing, and the fuel-side outlet and the air-side outlet are located on the same side of the housing.

[0011] Preferably, the second channel includes a plurality of fuel-side heat exchange channels disposed between the fuel-side inlet and the fuel-side outlet, and each of the fuel-side heat exchange channels has the same inner diameter;

[0012] The third channel includes multiple air-side heat exchange channels disposed between the air-side inlet and the air-side outlet, each of which has the same inner diameter.

[0013] Preferably, there are two fuel-side heat exchange channels, namely an outer spiral heat exchange channel and an inner spiral heat exchange channel.

[0014] There are two air-side heat exchange channels, namely an outer spiral heat exchange channel and an inner spiral heat exchange channel.

[0015] The fuel outer spiral heat exchange channel and the air outer spiral heat exchange channel are arranged in a spiral overlapping manner, and the fuel inner spiral heat exchange channel and the air inner spiral heat exchange channel are also arranged in a spiral overlapping manner.

[0016] Preferably, the spiral radius of the fuel outer spiral heat exchange channel is the same as that of the air outer spiral heat exchange channel, and the air outer spiral heat exchange channel overlaps above the fuel outer spiral heat exchange channel;

[0017] The spiral radius of the fuel internal spiral heat exchange channel is the same as that of the air internal spiral heat exchange channel, and the air internal spiral heat exchange channel overlaps above the fuel internal spiral heat exchange channel.

[0018] Preferably, the inner diameter of the fuel-side heat exchange channel is smaller than that of the air-side heat exchange channel.

[0019] Preferably, the ratio of the flow area of ​​the air-side heat exchange channel to the flow area of ​​the fuel-side heat exchange channel is in the range of 3:2 to 4:1.

[0020] Preferably, manifolds are provided at both ends of the plurality of fuel-side heat exchange channels with the fuel-side inlet and the fuel-side outlet, respectively, to realize the diversion and convergence of the second channel;

[0021] Both ends of the plurality of air-side heat exchange channels are provided with manifolds between the air-side inlet and the air-side outlet, respectively, to realize the diversion and convergence of the third channel.

[0022] Preferably, the first channel, the second channel, and the third channel are all arranged in a spiral overlapping manner, and the first channel is located between the second channel and the third channel.

[0023] The high-temperature heat exchanger provided by this invention allows fuel gas and air to flow in independent second and third channels, respectively, and to exchange heat efficiently with the combustion flue gas in the first channel. At the same time, due to the spiral overlapping arrangement of the second and third channels, not only can the fuel gas and air be fully heated, but the temperature difference between them can also be effectively reduced, thereby providing more uniform reaction conditions for the solid oxide fuel cell and improving the overall operating efficiency and stability of the system.

[0024] The further solutions provided in this application can also achieve at least one of the following beneficial technical effects:

[0025] By placing the fuel-side inlet and air-side inlet on the same side of the casing, and the fuel-side outlet and air-side outlet on the same side of the casing, the installation convenience of the heat exchanger is significantly improved. In practical applications, this allows the high-temperature heat exchanger to be more easily connected to other components of the solid oxide fuel cell system, reducing the complexity of piping layout, and also contributing to the overall compact design of the system and ease of maintenance.

[0026] By having fuel gas and air flow separately in multiple heat exchange channels of the same inner diameter, it is possible to ensure that the fluid velocity is uniform in each channel, thereby improving heat exchange efficiency and reducing uneven temperature distribution caused by uneven flow velocity. This also simplifies the manufacturing process, improves system reliability and stability, and further reduces potential safety risks.

[0027] By utilizing the spiral overlapping arrangement between the outer spiral heat exchange channel of fuel and the outer spiral heat exchange channel of air, and between the inner spiral heat exchange channel of fuel and the inner spiral heat exchange channel of air, a more efficient heat exchange path can be formed between fuel gas and air during the heat exchange process. This effectively improves the heat exchange efficiency and reduces the temperature difference fluctuation between high-temperature flue gas and cold fluid, thereby ensuring the stability of the heat exchange process and further enhancing the overall performance of the system.

[0028] In a solid oxide fuel cell (SOFC) power generation system, the air-side flow rate is higher than the fuel-side flow rate. By setting the inner diameter of the fuel-side heat exchange channel smaller than that of the air-side heat exchange channel, the flow velocities in both channels are ensured to be nearly identical. To further ensure this consistency, the flow area ratio is preferably between 3:2 and 4:1. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the high-temperature heat exchanger in this embodiment.

[0031] Figure 1 In the accompanying drawings, the reference numerals include:

[0032] 1. Air-side outlet; 2. Fuel-side outlet; 3. Air-side inlet; 4. Fuel-side inlet; 5. High-temperature flue gas inlet; 6. High-temperature flue gas outlet; 7. Shell; 71. First channel; 72. Second channel; 73. Third channel; 723. Fuel outer spiral heat exchange channel; 724. Fuel inner spiral heat exchange channel; 733. Air outer spiral heat exchange channel; 734. Air inner spiral heat exchange channel. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. An embodiment of this application discloses a high-temperature heat exchanger.

[0035] The core of this invention is to provide a high-temperature heat exchanger.

[0036] Please refer to Figure 1 .

[0037] The high-temperature heat exchanger provided by the present invention includes a shell 7, and a first channel 71 for combustion flue gas flow, a second channel 72 for fuel gas flow, and a third channel 73 for air flow are provided inside the shell 7. The first channel 71, the second channel 72, and the third channel 73 are isolated from each other. The second channel 72 and the third channel 73 are arranged in a spiral overlapping manner. The combustion flue gas in the first channel 71 is used for high-temperature heat exchange with the fuel gas in the second channel 72 and the air in the third channel 73.

[0038] Specifically, the second channel 72 is used to introduce fuel gas into the SOFC power generation system, and the third channel 73 is used to introduce air into the SOFC power generation system. The first channel 71 introduces high-temperature flue gas, which then exchanges heat with the second channel 72 and the third channel 73. The first channel 71, the second channel 72, and the third channel 73 are isolated from each other, effectively preventing the fuel gas, air, and high-temperature flue gas from mixing and avoiding the safety risks caused by the mixing of cathode and anode gases. The high-temperature flue gas can be the high-temperature flue gas produced after the fuel exhaust gas and air exhaust gas from the SOFC reaction enter the combustion zone and are combusted.

[0039] Fuel gas and air enter from the fuel-side inlet 4 of the second channel 72 and the air-side inlet 3 of the third channel 73, respectively, and then flow along the spirally overlapping second and third channels 72 and 73, respectively. Simultaneously, combustion flue gas flows within the first channel 71, exchanging high-temperature heat with the fuel gas in the second channel 72 and the air in the third channel 73. Due to the spirally overlapping arrangement of the second and third channels 72 and 73, the fuel gas and air can fully exchange heat with the combustion flue gas during flow, thereby improving heat exchange efficiency. Finally, the heat-exchanged fuel gas and air flow out from the fuel-side outlet 2 of the second channel 72 and the air-side outlet 1 of the third channel 73, respectively, and enter the subsequent solid oxide fuel cell system. Furthermore, the parallel spiral arrangement of the second and third channels 72 and 73 ensures more uniform temperature distribution within the second and third channels 72 and allows for synchronous temperature increases during heat exchange.

[0040] The aforementioned high-temperature heat exchanger effectively solves the problem of excessive temperature difference between the fuel side and the air side at the inlet of the solid oxide fuel cell power generation system. Due to the spiral overlapping arrangement of the second channel 72 and the third channel 73, as well as the efficient heat exchange effect of the combustion flue gas, the fuel gas and air can be heated to similar or the same temperature before entering the fuel cell stack. This reduces the thermal stress caused by the high temperature difference and damage to the fuel cell stack, thereby improving the overall thermal efficiency and operational stability of the power generation system.

[0041] The high-temperature heat exchanger provided by the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

[0042] In one specific implementation, reference is made to... Figure 1 The second channel 72 includes a fuel-side inlet 4 and a fuel-side outlet 2 that are respectively opened on the housing 7, and the third channel 73 includes an air-side inlet 3 and an air-side outlet 1 that are respectively opened on the housing 7.

[0043] Specifically, the fuel-side inlet 4 and the fuel-side outlet 2 are disposed opposite to each other on both sides of the housing 7, and the air-side inlet 3 and the air-side outlet 1 are disposed opposite to each other on both sides of the housing 7. Fuel enters through the fuel-side inlet 4 and exits through the fuel-side outlet 2, while air enters through the air-side inlet 3 and exits through the air-side outlet 1.

[0044] Optionally, the ends of the fuel-side inlet 4, fuel-side outlet 2, air-side inlet 3, and air-side outlet 1 are all equipped with components for easy connection. These components can be flanges, threaded joints, or other standard connections, which can be selected according to actual needs to ensure reliable connection between the heat exchanger and other system components. This not only effectively improves the system's installation efficiency but also helps reduce maintenance costs and failure rates.

[0045] Furthermore, the fuel-side inlet 4 and the air-side inlet 3 are located on the same side of the housing 7, and the fuel-side outlet 2 and the air-side outlet 1 are located on the same side of the housing 7.

[0046] Specifically, since the fuel-side inlet 4 and the air-side inlet 3 are located on the same side of the casing 7, the fuel supply pipes and air supply pipes can be conveniently arranged on this side, reducing the possibility of pipe crossing and interference, and improving the system's compactness and aesthetics. Similarly, the fuel-side outlet 2 and the air-side outlet 1 are also located on the same side of the casing 7, allowing the heat-exchanged fuel and air to flow out smoothly and easily connect to subsequent system components. This helps improve the system's reliability and safety. By reducing the number and complexity of pipe connections, the risk of leakage and failure can be reduced. At the same time, it also facilitates routine maintenance and repair work, improving the system's maintainability.

[0047] Based on any of the above embodiments, refer to Figure 1 The second channel 72 includes multiple fuel-side heat exchange channels disposed between the fuel-side inlet 4 and the fuel-side outlet 2, each fuel-side heat exchange channel having the same inner diameter. The third channel 73 includes multiple air-side heat exchange channels disposed between the air-side inlet 3 and the air-side outlet 1, each air-side heat exchange channel having the same inner diameter.

[0048] Specifically, because the inner diameter of each fuel-side heat exchange channel (fuel side) and each air-side heat exchange channel (air side) is the same (fuel-side heat exchange channels have the same inner diameter as fuel-side heat exchange channels, and air-side heat exchange channels have the same inner diameter as air-side heat exchange channels), the flow velocity of fuel gas and air within their respective channels is more uniform. This helps to achieve uniform heat exchange between fuel gas / air and combustion flue gas, avoiding localized overheating or undercooling, thereby improving heat exchange efficiency and system stability. At the same time, the design of heat exchange channels with the same inner diameter simplifies the manufacturing process of the heat exchanger. Standardized pipes and connectors can be used, reducing production costs and manufacturing difficulty. It also facilitates the maintenance and replacement of the heat exchanger, improving the maintainability of the system.

[0049] Because the inner diameter of each fuel-side heat exchange channel (fuel side) and air-side heat exchange channel (air side) is the same, the fluid flow within the channels is more stable, reducing pressure fluctuations and vibrations caused by uneven flow rates. This helps improve system reliability and extend the service life of the heat exchanger.

[0050] Furthermore, two heat exchange channels are provided on the fuel side: an outer spiral heat exchange channel 723 and an inner spiral heat exchange channel 724. Two heat exchange channels are also provided on the air side: an outer spiral heat exchange channel 733 and an inner spiral heat exchange channel 734. The outer spiral heat exchange channel 723 and the outer spiral heat exchange channel 733 are arranged in a spiral overlapping manner, as are the inner spiral heat exchange channel 724 and the inner spiral heat exchange channel 734.

[0051] Specifically, the outer spiral heat exchange channel 723 for fuel and the outer spiral heat exchange channel 733 for air are spirally arranged inside the shell 7 and close to the inner wall of the shell 7, while the inner spiral heat exchange channel 724 for fuel and the inner spiral heat exchange channel 734 for air are located inside the spiral of the outer spiral heat exchange channel 723 for fuel and the outer spiral heat exchange channel 733 for air. This allows the fuel and air to come into full contact during the flow process, thereby achieving efficient heat exchange. The heat conduction between the inner and outer spiral channels can form a sandwich effect, which helps to further improve the heat exchange efficiency.

[0052] Based on any of the above embodiments, refer to Figure 1 The spiral radius of the fuel outer spiral heat exchange channel 723 is the same as that of the air outer spiral heat exchange channel 733, and the air outer spiral heat exchange channel 733 overlaps above the fuel outer spiral heat exchange channel 723. The spiral radius of the fuel inner spiral heat exchange channel 724 is the same as that of the air inner spiral heat exchange channel 734, and the air inner spiral heat exchange channel 734 overlaps above the fuel inner spiral heat exchange channel 724.

[0053] Specifically, the overlapping arrangement of the spiral channels with the same spiral radius allows for the formation of tight heat exchange interfaces between the outer fuel spiral heat exchange channel 723 and the outer air spiral heat exchange channel 733, as well as between the inner fuel spiral heat exchange channel 724 and the inner air spiral heat exchange channel 734. When the combustion flue gas passes through the first channel 71, its heat is evenly transferred to the outer fuel spiral heat exchange channel 723 and the outer air spiral heat exchange channel 733, as well as the inner fuel spiral heat exchange channel 724 and the inner air spiral heat exchange channel 734. This heat transfer method not only improves heat exchange efficiency but also helps reduce heat loss, allowing the fuel gas and air to be heated more effectively to the required temperature. It also helps reduce fluid resistance during flow, increasing fluid velocity and heat exchange efficiency. Furthermore, the uniform and stable spacing between the spiral channels reduces localized overheating or undercooling caused by uneven fluid distribution, thereby improving the overall performance and reliability of the heat exchanger.

[0054] Based on any of the above embodiments, refer to Figure 1 The inner diameter of the fuel-side heat exchange channel is smaller than that of the air-side heat exchange channel.

[0055] Specifically, this consideration is based on the reality that the air-side flow rate in a solid oxide fuel cell (SOFC) system is typically higher than the fuel-side flow rate. The air side needs to provide sufficient oxidant to support the electrochemical reaction in the fuel cell. Furthermore, since SOFC power generation is an exothermic reaction, excess air is used to lower the stack temperature and prevent localized hot spots that could damage the stack. Therefore, its flow rate is often relatively high. The fuel side, on the other hand, supplies an appropriate amount of fuel gas based on the actual power requirements of the fuel cell. To ensure that both the fuel gas and air are adequately heated within the heat exchanger and that their temperatures are similar or identical before entering the fuel cell, a proper design of the heat exchange channel's inner diameter is necessary.

[0056] By making the inner diameter of the fuel-side heat exchange channel (i.e., the heat exchange channel on the fuel side) smaller than that of the air-side heat exchange channel (i.e., the heat exchange channel on the air side), the flow velocities of the fuel gas and air can be matched while ensuring an appropriate ratio of their flow areas. Since the air-side flow rate is relatively large, a larger inner diameter can reduce its velocity, preventing insufficient heat exchange or excessive pressure loss due to excessively high flow rates; while the fuel-side flow rate is relatively small, a smaller inner diameter can maintain a moderate flow rate, thereby improving heat exchange efficiency.

[0057] Furthermore, the design of the inner diameter difference helps reduce uneven fluid distribution within the heat exchange channels. A larger inner diameter provides a more stable flow space for air, reducing eddies and turbulence, thereby improving heat exchange efficiency and system stability. While the fuel side has a smaller inner diameter, its flow rate is also smaller; therefore, efficient heat exchange can still be achieved through proper channel length and shape design. By making the inner diameter of the fuel-side heat exchange channel smaller than that of the air-side heat exchange channel, this application can better adapt to the actual needs of SOFC systems, achieving efficient and uniform heating of fuel gas and air, and improving the overall performance of the entire power generation system.

[0058] Furthermore, the ratio of the flow area of ​​the air-side heat exchange channel to the flow area of ​​the fuel-side heat exchange channel ranges from 3:2 to 4:1.

[0059] Specifically, through further calculations and experiments, when the ratio of the flow area of ​​the air-side heat exchange channel to the flow area of ​​the fuel-side heat exchange channel is between 3:2 and 4:1, it can be further ensured that the flow velocities of the two are close to being the same.

[0060] Based on any of the above embodiments, refer to Figure 1Each end of one of the multiple fuel-side heat exchange channels is connected to a manifold between the fuel-side inlet 4 and the fuel-side outlet 2, respectively, to achieve the diversion and convergence of the second channel 72. Similarly, each end of one of the multiple air-side heat exchange channels is connected to a manifold between the air-side inlet 3 and the air-side outlet 1, respectively, to achieve the diversion and convergence of the third channel 73.

[0061] Specifically, on the fuel side, manifolds are located at fuel-side inlet 4 and fuel-side outlet 2. Their main function is to evenly distribute the fuel gas to each fuel-side heat exchange channel (i.e., the outer spiral heat exchange channel 723 and the inner spiral heat exchange channel 724), and after heat exchange, to collect the fuel gas from each channel before discharging it from the heat exchanger. This splitting and confluence design ensures that the fuel gas can pass through the heat exchanger efficiently and evenly, improving heat exchange efficiency.

[0062] Similarly, on the air side, manifolds are located at the air-side inlet 3 and the air-side outlet 1. Their function is to evenly distribute air to each air-side heat exchange channel (i.e., the outer spiral heat exchange channel 733 and the inner spiral heat exchange channel 734), and after heat exchange, to collect the air from each channel and then discharge it from the heat exchanger. This design also helps to improve the heat exchange efficiency of the air and ensures that the air can pass through the heat exchanger evenly and stably.

[0063] The manifold design effectively considers system reliability and maintainability. By rationally designing the manifold's shape, size, and connection methods, the flow of fuel gas and air within the heat exchanger can be made more stable and reliable, reducing the risk of leaks and malfunctions. At the same time, the manifold facilitates routine maintenance and repairs, improving system maintainability.

[0064] Based on any of the above embodiments, the first channel 71, the second channel 72 and the third channel 73 are all arranged in a spiral overlapping manner, and the first channel 71 is located between the second channel 72 and the third channel 73.

[0065] Specifically, the spiral overlap of the first channel 71, the second channel 72, and the third channel 73 allows the first channel 71 (typically carrying combustion flue gas) to be tightly interwoven between the second channel 72 (fuel-side heat exchange channel) and the third channel 73 (air-side heat exchange channel). This significantly increases the heat exchange area between the combustion flue gas and the fuel gas and air, thereby improving heat exchange efficiency. During the spiral flow, the combustion flue gas continuously transfers heat with the fuel gas and air, ensuring that the fuel gas and air are sufficiently preheated to reach the ideal reaction temperature before entering the solid oxide fuel cell. Simultaneously, the location of the first channel 71 between the second channel 72 and the third channel 73 helps achieve uniform heat distribution. Because the combustion flue gas exchanges heat with both fuel gas and air simultaneously, it ensures a more uniform temperature distribution of the fuel gas and air within the heat exchanger, avoiding localized overheating or undercooling. Furthermore, the spiral overlap arrangement makes the heat exchanger structure more compact and efficient. By optimizing the channel layout and shape, a larger heat exchange area and higher heat exchange efficiency can be achieved within a limited space. This not only helps reduce the size and weight of heat exchangers, improving the portability and flexibility of the system, but also helps reduce manufacturing costs and maintenance difficulty.

[0066] The implementation principle of a high-temperature heat exchanger according to an embodiment of this application is as follows: Through a unique channel design and layout, efficient heat exchange is achieved between combustion flue gas, fuel gas, and air to meet the preheating requirements of solid oxide fuel cell (SOFC) systems for fuel gas and air. The high-temperature heat exchanger has three main channels: a first channel for combustion flue gas flow, a second channel for fuel gas flow, and a third channel for air flow. These two channels are arranged in a spiral overlapping manner. This spiral overlapping arrangement greatly increases the heat exchange area, enabling continuous heat transfer between the combustion flue gas and fuel gas and air during its flow.

[0067] During implementation, fuel gas and air enter the heat exchanger through their respective inlets and flow along the spirally overlapping second and third channels. Because the combustion flue gas in the first channel has a higher temperature, it acts as a heat source to heat the fuel gas in the second channel and the air in the third channel. By precisely designing the inner diameter and flow area ratio of the third and second channels (controlled between 3:2 and 4:1), the fuel gas and air can achieve similar flow velocities and uniform heating effects within the heat exchanger.

[0068] To further improve heat exchange efficiency and ensure uniform flow, this high-temperature heat exchanger is equipped with manifolds at both the inlet and outlet on both the fuel and air sides. The manifolds distribute the fuel gas and air evenly into each heat exchange channel and collect them after heat exchange, discharging them from the heat exchanger. This design not only improves heat exchange efficiency but also reduces the risk of localized overheating or undercooling caused by uneven fluid distribution.

[0069] Based on any of the above embodiments, the heat exchange structure of the high-temperature heat exchanger is further optimized by adding spiral fins or annular fins to the outer surface of the fuel outer spiral heat exchange channel (723), the fuel inner spiral heat exchange channel (724), the air outer spiral heat exchange channel (733), and the air inner spiral heat exchange channel (734) to enhance heat exchange.

[0070] Specifically, spiral or annular fins can be directly formed onto the outer surface of the heat exchange channel through an integrated processing method. The fin height can be designed to be 10%-30% of the pipe diameter to ensure that the heat exchange area is effectively increased without increasing flow resistance or reducing structural strength due to excessive height. At the same time, the spacing between the fins can be set to 2-5 times the fin height, which can disrupt the laminar boundary layer of flue gas, promote turbulent heat transfer, and create flue gas turbulence between the fins, further improving the heat transfer coefficient.

[0071] Based on any of the above embodiments, the internal flow field of the high-temperature heat exchanger is further optimized. Specifically, multi-stage flow guide baffles are set inside the shell along the flue gas flow direction (from the high-temperature flue gas inlet 5 to the outlet 6). These flow guide baffles are arranged in 3-5 sets of 45° staggered baffles to guide the flue gas to form a more complex flow path within the heat exchanger.

[0072] Specifically, the spacing between the guide vanes can be 0.5-1.2 times the shell diameter to ensure sufficient turbulence during flue gas flow without increasing flow resistance due to excessive spacing. Simultaneously, the cut-out ratio of the guide vanes can be 20%-50%, ensuring smooth flue gas passage while enhancing turbulence to some extent. The multi-stage guide vanes create a Z-shaped flow pattern, significantly improving the uniformity of flue gas velocity and resulting in a more even distribution of flue gas within the heat exchanger, thus increasing heat exchange efficiency. It also reduces the dead zone area by over 60%, effectively preventing localized overheating or undercooling caused by poor flue gas flow, further enhancing the overall performance of the heat exchanger. Furthermore, it effectively extends the flue gas residence time by 15%-25%, allowing more time for heat exchange between the flue gas and fuel gas and air within the heat exchanger, thereby further improving the sufficiency and efficiency of heat exchange.

[0073] Based on any of the above embodiments, a porous metal foam layer with decreasing porosity along the flue gas flow direction is filled in the first channel 71. The porosity of the porous metal foam layer decreases gradually from 80%-85% at the high-temperature flue gas inlet 5 to 60%-65% at the high-temperature flue gas outlet 6. The thickness H of the porous metal foam layer is 1 / 3 to 1 / 2 of the spacing D of the spiral heat exchange pipes, and the spiral heat exchange pipes include overlapping spiral pipes of the second channel 72 and the third channel 73.

[0074] Specifically, the gradient porosity porous metal foam layer is prepared using powder metallurgy. A gradient porosity distribution is achieved by controlling the content of the pore-forming agent, resulting in a three-dimensional interconnected network structure. The average pore diameter is 2-3 mm at the inlet and 0.5-1 mm at the outlet, thus optimizing the internal flow field distribution of the high-temperature heat exchanger and significantly improving heat exchange efficiency and thermal management performance. Structurally, the high-porosity inlet design allows high-temperature flue gas to quickly and uniformly permeate into the porous layer, effectively reducing the flow resistance of the flue gas at the inlet section and thereby lowering the pressure loss of the entire heat exchanger.

[0075] Furthermore, as the flue gas penetrates deeper along the flow direction, the porosity of the porous metal foam layer gradually decreases, resulting in a denser structure at the outlet end. This dense structure significantly enhances the turbulence of the flue gas, promoting heat transfer between the flue gas and the spiral heat exchange pipe, thereby greatly improving the terminal heat exchange efficiency. Using a gradient porous layer significantly improves the heat transfer coefficient at the outlet section compared to schemes without a porous layer or with a uniform porous layer.

[0076] Furthermore, the ratio of the thickness H of the porous metal foam layer to the spacing D of the spiral heat exchange pipes can be between 1 / 3 and 1 / 2, ensuring a spatial layout match between the porous layer and the spiral pipes. This avoids the generation of flow dead zones and optimizes the heat transfer path. Therefore, the temperature field between the flue gas and the tube-side fluid can achieve synchronous gradient changes, significantly improving the thermal management efficiency of the heat exchanger.

[0077] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0078] Based on any of the above embodiments, the air outer spiral heat exchange channel 733, the air inner spiral heat exchange channel 734, the fuel outer spiral heat exchange channel 723, and the fuel inner spiral heat exchange channel 724 all adopt composite tubes. The composite tube includes an inner layer, a middle layer, and an outer layer arranged sequentially. The inner layer is an Inconel 625 nickel-based high-temperature alloy layer, the middle layer is a graphene-reinforced thermally conductive coating, and the outer layer is a SUS310S austenitic stainless steel layer or an Inconel 625 nickel-based high-temperature alloy layer.

[0079] Specifically, the inner layer is a 0.5-1mm thick Inconel 625 nickel-based high-temperature alloy layer. This Inconel 625 alloy layer directly contacts the high-temperature fuel / air medium, utilizing its excellent high-temperature corrosion resistance, withstanding temperatures up to 1150℃, and possessing anti-carburization properties to ensure the long-term stability of the pipeline in corrosive atmospheres containing sulfur and chlorine. The middle layer is a 0.2mm thick graphene-reinforced thermally conductive coating. This coating is prepared using chemical vapor deposition (CVD) technology, achieving an in-plane thermal conductivity of 5300 W / (m·K). Furthermore, nanoscale interface optimization technology enables the coating to form coherent grain boundaries with the inner and outer metal layers, achieving efficient heat conduction across the interlayer interface. The outer layer is a 1-1.5mm thick SUS310S austenitic stainless steel layer. The SUS310S stainless steel layer is formed into a dense oxide protective layer through cold rolling process. The Cr2O3 content is ≥22%. It can effectively block oxygen penetration in a high temperature environment of 800-950℃, while providing high-strength mechanical support with a tensile strength ≥520 MPa.

[0080] The aforementioned composite tube structure achieves metallurgical bonding of each layer of material through a vacuum hot-pressing diffusion welding process. The expansion coefficients of the three layers are designed with a gradient matching, with the Inconel 625 alloy layer having an expansion coefficient of 12.8 × 10⁻⁻⁻⁶. 6 At / ℃, the coefficient of thermal expansion of the graphene coating is -6×10⁻ 6 At / ℃, the coefficient of thermal expansion of the SUS310S stainless steel layer is 16.0×10⁻ 6 / ℃, to effectively alleviate thermal cycling stress.

[0081] The heat exchanger using this composite tube achieves the following performance improvements in a solid oxide fuel cell (SOFC) system: improved tube-side fluid temperature uniformity by 40%, extended thermal cycle life by more than 3 times, reduced wall thickness by 25% under the same heat exchange load, and achieved a heat exchanger compactness index (HEI) of 58 m² / m³, which is 35% higher than that of the traditional structure.

[0082] The high-temperature heat exchanger provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of this invention.

Claims

1. A high-temperature heat exchanger, characterized in that, Includes a housing (7), which is provided with a first channel (71) for combustion flue gas flow, a second channel (72) for fuel gas flow, and a third channel (73) for air flow. The first channel (71), the second channel (72), and the third channel (73) are isolated from each other. The second channel (72) and the third channel (73) are arranged in a spiral overlapping manner. The combustion flue gas in the first channel (71) is used for high-temperature heat exchange with the fuel gas in the second channel (72) and the air in the third channel (73). The fuel-side inlet (4) and the air-side inlet (3) are located on the same side of the housing (7), and the fuel-side outlet (2) and the air-side outlet (1) are located on the same side of the housing (7); The second channel (72) includes a plurality of fuel-side heat exchange channels disposed between the fuel-side inlet (4) and the fuel-side outlet (2), and each of the fuel-side heat exchange channels has the same inner diameter; The third channel (73) includes multiple air-side heat exchange channels disposed between the air-side inlet (3) and the air-side outlet (1), and each air-side heat exchange channel has the same inner diameter; There are two fuel-side heat exchange channels, namely an outer fuel spiral heat exchange channel (723) and an inner fuel spiral heat exchange channel (724). There are two air-side heat exchange channels, namely an outer air spiral heat exchange channel (733) and an inner air spiral heat exchange channel (734). The fuel outer spiral heat exchange channel (723) and the air outer spiral heat exchange channel (733) are arranged in a spiral overlapping manner, and the fuel inner spiral heat exchange channel (724) and the air inner spiral heat exchange channel (734) are arranged in a spiral overlapping manner. The inner diameter of the fuel-side heat exchange channel is smaller than that of the air-side heat exchange channel; The ratio of the flow area of ​​the air-side heat exchange channel to the flow area of ​​the fuel-side heat exchange channel ranges from 3:2 to 4:

1. The first channel (71), the second channel (72) and the third channel (73) are all arranged in a spiral overlapping manner, and the first channel (71) is located between the second channel (72) and the third channel (73).

2. A high-temperature heat exchanger according to claim 1, characterized in that, The second channel (72) includes a fuel-side inlet (4) and a fuel-side outlet (2) that are opened opposite to each other on the housing (7), and the third channel (73) includes an air-side inlet (3) and an air-side outlet (1) that are opened opposite to each other on the housing (7).

3. A high-temperature heat exchanger according to claim 1, characterized in that, The spiral radius of the fuel outer spiral heat exchange channel (723) is the same as that of the air outer spiral heat exchange channel (733), and the air outer spiral heat exchange channel (733) overlaps above the fuel outer spiral heat exchange channel (723). The spiral radius of the fuel internal spiral heat exchange channel (724) is the same as that of the air internal spiral heat exchange channel (734), and the air internal spiral heat exchange channel (734) overlaps above the fuel internal spiral heat exchange channel (724).

4. A high-temperature heat exchanger according to claim 1, characterized in that, Both ends of the multiple fuel-side heat exchange channels are provided with manifolds between the fuel-side inlet (4) and the fuel-side outlet (2) respectively, so as to realize the diversion of the second channel (72) and the convergence of the second channel (72); Both ends of the multiple air-side heat exchange channels are provided with manifolds between the air-side inlet (3) and the air-side outlet (1) respectively, so as to realize the diversion of the third channel (73) and the convergence of the third channel (73).

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