Same-pass tubular heat exchanger

Abstract

The invention discloses a same-pass tubular heat exchanger, which belongs to the technical field of heat exchange devices, and comprises a same-pass pipeline system, the same-pass pipeline system comprises two parallel main flow guide pipes and N rows of secondary flow guide pipes, and the main flow guide pipes and the secondary flow guide pipes are arranged in a mutually perpendicular crossing manner and are communicated through welding, the pipe wall of the secondary flow guide pipe is provided with inward concave structures, and the inward concave structures are evenly distributed in the length direction of the secondary flow guide pipe. The inner concave structures of the pipe wall of the secondary flow guide pipe are evenly distributed in the length direction, the flow field of fluid in the pipe can be optimized, when the fluid flows in the secondary flow guide pipe, the inner concave structures can disturb the fluid, so that the fluid is converted from a relatively stable laminar flow state to a turbulent flow state, the turbulent flow degree of the fluid is enhanced, and the flow efficiency is improved. Therefore, the heat exchange efficiency between the fluid and the pipe wall of the secondary flow guide pipe is improved, the local resistance of the fluid flowing in the pipe can be reduced, and the fluid flows more smoothly.

Description

Technical Field

[0001] This invention belongs to the technical field of heat exchange devices, and specifically relates to a parallel tube heat exchanger. Background Technology

[0002] Existing parallel-flow tube heat exchangers solve the problems of uneven heat exchange and high water resistance in traditional parallel-flow systems by arranging the main and secondary flow tubes in the same direction. However, there is still room for optimization in terms of fluid flow characteristics and local heat exchange efficiency. On the one hand, the fluid in the traditional straight-tube secondary flow tube is prone to forming a "laminar boundary layer," with low fluid velocity near the tube wall, posing a risk of local stagnation and leading to a decrease in heat medium distribution efficiency. On the other hand, heat exchange capillaries are mostly smooth straight tubes. Although the heat exchange area is increased by dense arrangement, the turbulence of the external medium to be exchanged is weak when flowing through the tube wall, resulting in a low heat transfer coefficient and making it difficult to further improve the heat exchange efficiency.

[0003] Meanwhile, in harsh environments such as sewage and high-hardness water, fouling tends to adhere evenly to the smooth surface of traditional straight pipes, forming a continuous scale layer after long-term operation, hindering heat transfer. However, simply increasing the pipe diameter to improve flow rate would increase the space occupied by the heat exchanger, violating the requirement of "compact design." Therefore, it is urgent to improve the pipe wall structure through irregular shapes, simultaneously optimizing fluid flow characteristics and heat transfer performance while ensuring the advantages of the same-flow system, balancing anti-fouling capabilities with space compactness. Summary of the Invention

[0004] The purpose of this invention is to provide a parallel tube heat exchanger to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a parallel tube heat exchanger, comprising a parallel tube system, the parallel tube system including two parallel main flow tubes and N rows of secondary flow tubes, the main flow tubes and the secondary flow tubes being perpendicularly intersecting each other and connected by welding to form a vertical parallel tube system, the tube wall of the secondary flow tubes having a concave structure, the concave structure being uniformly distributed along the length direction of the secondary flow tubes, the concave depth being 1 / 8 to 1 / 5 of the diameter of the secondary flow tubes, the concave structure being used to optimize the fluid flow field inside the tubes.

[0006] Preferably, the outer wall of each row of secondary guide tubes is welded with heat exchange capillaries arranged at equal intervals. The wall of the heat exchange capillaries is provided with an outward convex structure. The outward convex structure is spirally distributed or arrayed along the length of the heat exchange capillaries. The height of the outward convex structure is 1 / 10 to 1 / 6 of the diameter of the heat exchange capillaries. The outward convex structure is used to enhance the degree of fluid turbulence.

[0007] Preferably, a corrugated heat exchange branch pipe is tightly fitted around the outside of the secondary guide pipe, and the corrugated heat exchange branch pipe does not contact the heat exchange capillary.

[0008] Preferably, the concave structure of the secondary guide tube is an arc-shaped concave or a polygonal concave, and the cross-sectional profile of the concave structure smoothly transitions with the inner wall of the secondary guide tube.

[0009] Preferably, the convex structure of the heat exchange capillary is hemispherical and the surface roughness of the convex structure is ≤Ra1.6μm.

[0010] Preferably, when the convex structures are spirally distributed, the spiral angle is 30° to 60°, and when distributed in an array, adjacent convex structures are arranged in an equilateral triangle or a square.

[0011] Preferably, the heat exchange capillary tube is made of corrosion-resistant metal.

[0012] Preferably, the inlet ends of the two main flow pipes are respectively connected to the inlet pipe and the outlet ends are respectively connected to the outlet pipe. The diameters of the inlet pipe and the outlet pipe are both adapted to the diameter of the main flow pipe. The inlet pipe is equipped with a flow meter and a pressure gauge, and the outlet pipe is equipped with a temperature sensor.

[0013] Preferably, it also includes a severe water quality treatment structure, which includes an anti-corrosion coating applied to the inner wall of the main flow pipe, the inner wall of the secondary flow pipe, and the outer wall of the heat exchange capillary.

[0014] Preferably, the anti-corrosion coating is an epoxy resin coating or a polytetrafluoroethylene coating, with a coating thickness of 0.1 to 0.3 mm, and a spraying and brushing composite process is used at the recessed part of the secondary guide tube and the protruding part of the heat exchange capillary.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. This invention employs a parallel pipeline system with two main guide pipes and multiple rows of secondary guide pipes perpendicularly welded together, ensuring uniform fluid flow through each row of secondary guide pipes. Compared to non-parallel pipeline systems, this avoids uneven flow distribution caused by differences in pipe length, resulting in more balanced heat exchange across all areas of the heat exchanger and improved overall heat exchange stability and reliability. It is particularly suitable for large-scale heat exchange scenarios requiring high flow uniformity. The concave structure of the secondary guide pipe wall is uniformly distributed along its length, optimizing the fluid flow field within the pipe. When the fluid flows within the secondary guide pipe, the concave structure disturbs the fluid, causing it to transition from a relatively stable laminar flow state to a turbulent state, enhancing the turbulence and thus improving the heat exchange efficiency between the fluid and the secondary guide pipe wall. Simultaneously, it reduces local resistance to fluid flow within the pipe, allowing for smoother fluid flow.

[0017] 2. This invention increases the contact area between the heat exchanger and the fluid by welding heat exchange capillaries at equal intervals. A larger contact area means more space for heat exchange, effectively improving overall heat exchange efficiency and better meeting the needs of applications with high heat exchange efficiency requirements, such as large-volume devices. Simultaneously, the convex structures on the capillary walls are spirally or arrayed along their length. When the fluid flows through these structures, the original laminar flow is further disrupted, creating stronger turbulence. This strong turbulence allows for faster and more uniform heat transfer within the fluid, significantly improving heat exchange efficiency. Furthermore, the presence of the convex structures also increases the effective heat exchange area of ​​the capillary, further enhancing heat exchange capacity from a structural perspective.

[0018] 3. This invention, by tightly fitting a corrugated heat exchange branch pipe around the secondary guide pipe, increases the contact area with the fluid to be heat exchanged due to the corrugated structure of the corrugated pipe, thereby improving its heat exchange efficiency and assisting the secondary guide pipe and heat exchange capillary tube in heat exchange. Simultaneously, the design of the corrugated heat exchange branch pipe not contacting the heat exchange capillary tube avoids mutual interference between the two during fluid flow, ensuring the stability of their respective flow fields, preventing damage to heat exchanger components due to structural collisions, enhancing the overall structural stability and durability, and extending the service life of the heat exchanger.

[0019] 4. This invention, through the design of a smoothly transitioning concave structure, can, on the one hand, avoid the generation of local eddies or dead zones during fluid flow, reduce fluid energy loss, and make fluid flow smoother. On the other hand, the smooth surface also helps to reduce the frictional resistance of the fluid during flow, while reducing the probability of dirt adhesion at these special structures, reducing the impact of scaling on heat exchange efficiency, and facilitating the cleaning and maintenance of the heat exchanger. Attached Figure Description

[0020] Figure 1 This is a plan view of the present invention;

[0021] Figure 2 This is a partial view of the heat exchange capillary tube of the present invention;

[0022] Figure 3 This is a cross-sectional view of the secondary guide tube of the present invention;

[0023] Figure 4 This is a schematic diagram of the secondary guide tube and the concave structure of the present invention.

[0024] In the diagram: 1. Main flow tube; 2. Secondary flow tube; 3. Concave structure; 4. Corrugated heat exchange branch tube; 5. Heat exchange capillary tube; 6. Convex structure. Detailed Implementation

[0025] 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.

[0026] Example 1

[0027] Please see Figures 1-4 This invention provides a parallel-flow tube heat exchanger, including a parallel-flow pipe system. The parallel-flow pipe system includes two parallel main flow tubes 1 and N rows of secondary flow tubes 2. The main flow tubes 1 and secondary flow tubes 2 are perpendicularly intersecting each other and connected by welding to form a vertical parallel-flow pipe system. The wall of the secondary flow tubes 2 is provided with a concave structure 3. The concave structure 3 is evenly distributed along the length of the secondary flow tubes 2, and the concave depth is 1 / 8 to 1 / 5 of the diameter of the secondary flow tubes 2. The concave structure 3 is used to optimize the fluid flow field inside the tube. The concave structure 3 of the secondary flow tubes 2 is an arc-shaped concave or a polygonal concave. The cross-sectional profile of the concave structure 3 smoothly transitions with the inner wall of the secondary flow tubes 2.

[0028] Furthermore, the parallel flow piping system employs a structure where two parallel main flow pipes 1 are perpendicularly welded to multiple rows of secondary flow pipes 2, forming a vertical parallel flow piping system. This parallel flow design ensures uniform flow of the heat medium through each row of secondary flow pipes 2, avoiding uneven flow distribution due to differences in pipe length. This results in a more balanced heat exchange effect across all areas of the heat exchanger, improving overall heat exchange stability and reliability. The concave structure 3 of the secondary flow pipe 2 wall is evenly distributed along its length and is either arc-shaped or polygonal, with a smooth transition between its cross-sectional profile and the inner wall of the secondary flow pipe 2. This design primarily optimizes the fluid flow field within the pipe, reducing local resistance and allowing for smoother fluid flow. It also enhances turbulence, improving heat exchange efficiency, as stronger turbulence allows for more complete heat exchange between the heat medium, the pipe wall, and the medium to be exchanged.

[0029] The mechanism of the concave structure 3 is as follows: when the heat medium flows in the secondary guide pipe 2, the concave region will have a guiding effect on the fluid, breaking the continuous distribution of the laminar boundary layer, causing the low-velocity fluid near the pipe wall to flow towards the center of the pipe, reducing local stagnation dead zones. At the same time, the smooth transition of the concave profile can avoid the formation of eddies, reduce local resistance loss, and ensure the resistance balance of the same-path system. According to simulation calculations, compared with a straight pipe, the concave structure 3 can improve the uniformity of fluid velocity distribution in the secondary guide pipe 2 by 20% to 30% and reduce the local resistance coefficient by 15% to 20%.

[0030] Each row of guide tubes 2 has heat exchange capillary tubes 5 welded to its outer wall at equal intervals. The tube wall of the heat exchange capillary tubes 5 is provided with an outward convex structure 6. The outward convex structure 6 is spirally distributed or arrayed along the length of the heat exchange capillary tubes 5. The height of the outward convex structure is 1 / 10 to 1 / 6 of the diameter of the heat exchange capillary tubes 5. The outward convex structure is used to enhance the degree of fluid turbulence. The outward convex structure 6 of the heat exchange capillary tubes 5 is hemispherical and has a surface roughness ≤ Ra1.6μm. The heat exchange capillary tubes 5 are made of corrosion-resistant metal tubes. When the outward convex structure 6 is spirally distributed, the spiral angle is 30° to 60°. When it is arrayed, adjacent outward convex structures 6 are arranged in an equilateral triangle or square.

[0031] Furthermore, heat exchange capillary tubes 5 are welded at equal intervals to the outer wall of each row of secondary guide tubes 2, increasing the heat exchange area of ​​the heat exchanger. A larger heat exchange area means more thorough contact between the heat transfer medium and the medium to be heat exchanged, thereby improving the overall heat exchange efficiency and meeting the heat exchange requirements of large-volume devices. The convex structure 6 is spirally or arrayed along the length of the heat exchange capillary tubes 5. When the fluid flows through the convex structure 6, it breaks the originally relatively stable laminar flow state, forming more turbulence. Turbulence enables faster and more uniform heat transfer within the fluid, greatly improving heat exchange efficiency. The convex structure 6 is hemispherical with a surface roughness ≤ Ra1.6μm. This smooth surface helps reduce the probability of fouling on the surface of the heat exchange capillary tubes 5, reducing the impact of fouling on heat exchange efficiency, extending the clean operating time of the heat exchanger, and reducing maintenance costs. When the convex structure 6 is spirally distributed, the spiral angle is 30°-60°, which can guide the fluid to flow along the spiral direction, prolong the contact time between the fluid and the heat exchange capillary 5, and further enhance the heat exchange. When distributed in an array, adjacent convex structures 6 are arranged in an equilateral triangle or square, which can make the fluid turbulence more uniform in space and ensure the uniformity of heat exchange.

[0032] The working mechanism of the convex structure 6 is as follows: On the one hand, the convex structure 6 can directly increase the outer wall surface area of ​​the heat exchange capillary 5. Compared with a smooth straight tube, the surface area can be increased by 30% to 50%, significantly increasing the contact area with the external heat exchange medium. On the other hand, when the external medium flows through the convex structure 6, a small-scale vortex will be formed behind the protrusion, enhancing the fluid turbulence, destroying the heat exchange boundary layer, and improving the convective heat transfer coefficient of the heat exchange capillary 5. Moreover, the enhanced turbulence can reduce the adhesion of fouling to the tube wall and reduce the scaling rate.

[0033] The outer side of the secondary guide tube 2 is tightly fitted with a corrugated heat exchange branch tube 4, and the corrugated heat exchange branch tube 4 does not contact the heat exchange capillary tube 5.

[0034] Furthermore, the corrugated heat exchange branch pipe 4 is tightly fitted with the secondary guide pipe 2. On the one hand, its corrugated structure increases the contact area with the heat exchange medium, thereby improving heat exchange efficiency. On the other hand, its design of not contacting the heat exchange capillary tube 5 avoids mutual interference between the two during fluid flow, ensuring the stability of their respective flow fields. It also prevents damage to heat exchanger components due to structural collisions, enhancing the overall structural stability and durability.

[0035] The inlet ends of the two main flow pipes 1 are connected to the inlet pipes, and the outlet ends are connected to the outlet pipes. The diameters of the inlet and outlet pipes are matched with the diameter of the main flow pipes 1. A flow meter and a pressure gauge are installed on the inlet pipe, and a temperature sensor is installed on the outlet pipe.

[0036] Furthermore, the inlet and outlet water pipes are matched with the main flow pipe 1 in diameter, ensuring smooth fluid flow within the pipes and avoiding additional flow resistance caused by sudden changes in pipe diameter, thus making the fluid transport of the entire heat exchange device more efficient. The flow meter on the inlet water pipe can monitor the fluid flow rate entering the heat exchanger in real time, and the pressure gauge displays the inlet water pressure, allowing operators to adjust system operating parameters promptly based on flow and pressure data, ensuring the heat exchanger operates under suitable conditions. The temperature sensor on the outlet water pipe can monitor the outlet water temperature. Combined with the flow and pressure data at the inlet end, the heat exchanger's heat exchange effect can be more accurately assessed. If an abnormal outlet water temperature is detected, the problem can be investigated promptly, ensuring a stable and efficient heat exchange process.

[0037] The severe water quality treatment structure includes an anti-corrosion coating applied to the inner wall of the main flow pipe 1, the inner wall of the secondary flow pipe 2, and the outer wall of the heat exchange capillary tube 5. The anti-corrosion coating is made of epoxy resin or polytetrafluoroethylene, with a coating thickness of 0.1 to 0.3 mm. A combined spraying and brushing process is used at the recessed part of the inner concave structure 3 of the secondary flow pipe 2 and the protruding part of the outer convex structure 6 of the heat exchange capillary tube 5.

[0038] Furthermore, the combined spraying and brushing process ensures that the anti-corrosion coating is evenly and completely covered in the recessed areas of the inner concave structure 3 of the secondary guide tube 2 and the protruding areas of the outer convex structure 6 of the heat exchange capillary tube 5. These areas, due to their unique structure, are prone to becoming weak points in corrosion protection. This combined process effectively enhances the adhesion and integrity of the coating, improving the corrosion and scaling resistance of the main guide tube 1, secondary guide tube 2, and heat exchange capillary tube 5 in harsh water conditions, extending the service life of the heat exchanger, and ensuring its stable operation in water containing corrosive substances or prone to scaling.

[0039] Example 2

[0040] This embodiment provides a parallel-flow tubular heat exchanger for use in a large-volume water storage tank of 15m³, for heat exchange between sewage and clean water.

[0041] Furthermore, the main flow tube 1 is made of DN100 seamless steel pipe, with one at the top and one at the bottom. The secondary flow tubes 2 are made of DN50 seamless steel pipe, arranged in 10 rows at 300mm intervals along the length of the main flow tube 1. The concave structure 3 of the secondary flow tubes 2 is arc-shaped, with a concave depth of 8mm and a concave spacing of 120mm. The heat exchange capillary tubes 5 are made of 304 stainless steel pipe, with an inner diameter of 6mm and an outer diameter of 10mm. The convex structure 6 of the heat exchange capillary tubes 5 is hemispherical, with a convex height of 1.8mm and a convex spacing of 18mm, arranged in a spiral distribution with a spiral helix angle of 45°. The corrugated heat exchange branch pipes 4 are made of DN50 stainless steel corrugated pipe and are sleeved on the outside of the secondary flow tubes 2. The anti-corrosion coating is an epoxy resin coating with a thickness of 0.2mm.

[0042] Operational Results: The heat medium enters through the main flow pipe 1 at the top, and after being guided by the concave structure 3 of the 10 rows of secondary flow pipes 2, it is evenly distributed to each heat exchange capillary tube 5. The external heat exchange medium is sewage in a 15m³ water storage tank. When it flows through the convex structure 6 of the heat exchange capillary tube 5, it forms turbulence and exchanges heat with 70℃ clean water. After running for 3 hours, the sewage temperature rises to 45℃. The heat exchange efficiency is improved compared with the traditional parallel tube heat exchanger. After running continuously for 6 months, there is no obvious scaling in the concave structure 3 of the secondary flow pipes 2, and the amount of fouling on the convex structure 6 of the heat exchange capillary tube 5 is reduced by 35% compared with the smooth straight pipe.

[0043] Example 3

[0044] This embodiment provides a parallel-flow tubular heat exchanger, applied to a large industrial heat exchange device with a capacity of 20m³, for treating high-hardness water.

[0045] Furthermore, the main guide tube 1 is made of DN125 seamless steel pipe, and the secondary guide tube 2 is made of DN70 seamless steel pipe, arranged in 15 rows with a spacing of 250mm. The concave structure 3 of the secondary guide tube 2 is polygonal, with a concave depth of 12mm and a concave spacing of 180mm. The heat exchange capillary tube 5 is made of titanium alloy pipe with an inner diameter of 8mm and an outer diameter of 12mm. The convex structure 6 of the heat exchange capillary tube 5 is semi-cylindrical with a convex height of 2mm and a convex spacing of 20mm, arranged in a square array. The corrugated heat exchange branch pipe 4 is made of DN70 stainless steel corrugated pipe. The anti-corrosion coating is made of polytetrafluoroethylene with a thickness of 0.3mm.

[0046] Operational Results: After the heat medium enters the main flow pipe 1, the flow field is optimized by the concave structure 3 of the secondary flow pipe 2, with no local stagnation. When the external high-hardness water flows through the convex structure 6 of the heat exchange capillary 5, the turbulence is enhanced, and the heat transfer coefficient is increased by 40%. After 4 hours of operation, the temperature of the high-hardness water rises to 60℃, meeting the industrial heat demand. After 8 months of continuous operation, there are no corrosion marks on the pipe wall, and the scale layer thickness is ≤0.1mm, eliminating the need for frequent cleaning.

[0047] The working principle and usage process of this invention are as follows: The fluid to be heat-exchanged enters the inlet pipe and, after being monitored by a flow meter and pressure gauge, flows into the upper main flow pipe 1. The fluid flows within the main flow pipe 1 and, through a vertical connection structure with the secondary flow pipes 2, is distributed to each row of secondary flow pipes 2. Within the secondary flow pipes 2, due to the concave structure 3 of its pipe wall, the fluid flow field is optimized, resulting in smoother flow and enhanced turbulence. Simultaneously, the heat exchange capillary tubes 5 outside the secondary flow pipes 2, with their convex structure 6 of the pipe wall, further enhance fluid turbulence, increase the heat exchange area, and allow the fluid to fully exchange heat with the heat exchange capillary tubes 5, the secondary flow pipes 2, and the corrugated heat exchange branch pipes 4. The corrugated heat exchange branch pipes 4 also participate in heat exchange using their own corrugated structure, further improving heat exchange efficiency. After heat exchange, the fluid collects at the outlet end of the main flow pipe 1 and flows out after its temperature is monitored by a temperature sensor in the outlet pipe. Throughout the process, the anti-corrosion coating protects all pipeline components from corrosion caused by harsh water quality, ensuring the long-term stable operation of the system.

[0048] Operating Procedure: First, connect the inlet pipe to the inlet end of the main flow pipe 1, and connect the outlet pipe to the outlet end. Check that all pipe connections are secure and that there are no leaks. Confirm that the flow meter, pressure gauge, temperature sensor, and other instruments are working properly, and check that all components of the heat exchanger are undamaged.

[0049] Then, open the inlet valve to slowly introduce the fluid to be exchanged into the system, while observing the pressure gauge readings to ensure the inlet pressure is within the normal range. Monitor the inlet flow rate using a flow meter and adjust the valve to meet the heat exchange requirements. The fluid flows within the heat exchanger in a parallel pipeline system, exchanging heat with each heat exchange component. During this process, the outlet water temperature can be monitored in real time using a temperature sensor on the outlet pipeline to assess the heat exchange effect. After heat exchange is complete, close the inlet valve and wait for most of the fluid to be discharged from the system before closing the outlet valve. Regularly inspect the heat exchanger, checking the integrity of the anti-corrosion coating. Repair any damage promptly and clean any small amounts of scale that may have accumulated inside the pipes to ensure efficient heat exchange for the next use.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A parallel-pass tube heat exchanger, characterized in that, The system includes a parallel pipeline system comprising two parallel main flow pipes (1) and N rows of secondary flow pipes (2). The main flow pipes (1) and the secondary flow pipes (2) are perpendicularly intersecting each other and connected by welding to form a vertical parallel pipeline system. The wall of the secondary flow pipes (2) is provided with a concave structure (3). The concave structure (3) is evenly distributed along the length of the secondary flow pipes (2), and the concave depth is 1 / 8 to 1 / 5 of the diameter of the secondary flow pipes (2). The concave structure (3) is used to optimize the fluid flow field inside the pipe.

2. A parallel-tube heat exchanger according to claim 1, characterized in that, Each row of secondary guide tubes (2) has heat exchange capillaries (5) arranged at equal intervals welded to its outer wall. The heat exchange capillaries (5) have a convex structure (6) on their walls. The convex structure (6) is spirally distributed or arrayed along the length of the heat exchange capillaries (5). The convex height is 1 / 10 to 1 / 6 of the diameter of the heat exchange capillaries (5). The convex structure is used to enhance the degree of fluid turbulence.

3. A parallel-tube heat exchanger according to claim 1, characterized in that, The secondary guide tube (2) is tightly fitted with a corrugated heat exchange branch tube (4), and the corrugated heat exchange branch tube (4) does not contact the heat exchange capillary tube (5).

4. A parallel-tube heat exchanger according to claim 1, characterized in that, The concave structure (3) of the secondary guide tube (2) is an arc-shaped concave or a polygonal concave, and the cross-sectional profile of the concave structure (3) smoothly transitions with the inner wall of the secondary guide tube (2).

5. A parallel-tube heat exchanger according to claim 2, characterized in that, The convex structure (6) of the heat exchange capillary (5) is hemispherical and the surface roughness of the convex structure (6) is ≤Ra1.6μm.

6. A parallel-tube heat exchanger according to claim 2, characterized in that, When the convex structure (6) is spirally distributed, the spiral angle is 30° to 60°. When distributed in an array, adjacent convex structures (6) are arranged in an equilateral triangle or a square.

7. A parallel-tube heat exchanger according to claim 2, characterized in that, The heat exchange capillary tube (5) is made of corrosion-resistant metal.

8. A parallel-tube heat exchanger according to claim 1, characterized in that, The inlet ends of the two main flow pipes (1) are respectively connected to the inlet pipe, and the outlet ends are respectively connected to the outlet pipe. The pipe diameters of the inlet pipe and the outlet pipe are both adapted to the pipe diameter of the main flow pipe (1). A flow meter and a pressure gauge are provided on the inlet pipe, and a temperature sensor is provided on the outlet pipe.

9. A parallel-tube heat exchanger according to claim 1, characterized in that, It also includes a severe water quality treatment structure, which includes an anti-corrosion coating applied to the inner wall of the main flow pipe (1), the inner wall of the secondary flow pipe (2) and the outer wall of the heat exchange capillary (5).

10. A parallel-tube heat exchanger according to claim 9, characterized in that, The anti-corrosion coating is made of epoxy resin or polytetrafluoroethylene, with a coating thickness of 0.1 to 0.3 mm. The coating is applied by a combination of spraying and brushing at the recessed part of the concave structure (3) of the secondary guide tube (2) and the protruding part of the convex structure (6) of the heat exchange capillary tube (5).

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