Efficient tubular heat exchanger and operation control system thereof

Abstract

The invention discloses an efficient tubular heat exchanger and an operation control system thereof, belongs to the technical field of heat energy recovery of a papermaking drying process, and aims to improve the temperature uniformity of fins along the circumferential axial direction and the height direction of a heat exchange tube body and continuously guide and comb airflow through the collaborative design of'intermittent spiral fins' and'axial flow guide heat bridges'. A thermal boundary layer is efficiently destroyed, so that the defect of poor heat transfer of a traditional heat exchange tube is overcome, the gas side heat transfer coefficient is increased, and the dust accumulation resistance is remarkably improved; the operation control system comprises a heat source supply and pressure stabilization module, a hot air actual temperature regulation and control module and an operation control platform, a heat source side carries out feedforward regulation according to a vehicle speed-steam demand database established in advance, and in combination with pressure PID feedback, it is ensured that the pressure of a heat source supplied to a heat exchanger is stable; and the target temperature is dynamically set on the heat using side based on a paper type-temperature database and an environment temperature and humidity compensation model, and the precision of the hot air output temperature is improved.

Description

Technical Field

[0001] This invention relates to the field of heat recovery technology in paper drying processes, and more specifically, to a high-efficiency tubular heat exchanger and its operation control system. Background Technology

[0002] In the paper drying process, energy consumption is enormous, with the drying cylinder being the main energy-consuming stage. In order to reduce energy consumption and improve energy efficiency, the industry generally adopts heat recovery technology, which recovers the waste heat of the high-temperature condensate discharged from the drying cylinder and uses it to preheat air to assist in the drying of paper.

[0003] Typical recovery systems typically utilize flash tanks to recover waste heat from the high-temperature condensate in the drying cylinder and generate hot air via tubular heat exchangers. This hot air is then sent back to the drying section to assist in drying. Traditional straight fins transfer heat only through the narrow contact area at the fin root, resulting in a large temperature gradient along the height of the fins. This limits the ability to disturb the airflow and makes it difficult to effectively break the laminar thermal boundary layer that is close to the fin surface. This is the main source of air-side thermal resistance, leading to a low overall heat transfer coefficient (K value). In addition, in the papermaking process, on the one hand, the pressure of the heat source (flash steam) supplied to the heat exchanger by the flash tank is greatly affected by the changes in the paper speed and basis weight, resulting in drastic fluctuations and unstable hot air output. On the other hand, the actual temperature control of hot air often adopts simple feedback without considering the influence of multiple variables such as paper type and ambient temperature and humidity, resulting in poor accuracy, which cannot meet the requirements of high-quality paper production and also restricts the potential for energy saving.

[0004] Therefore, in response to the actual technical deficiencies, a high-efficiency tubular heat exchanger and its operation control system are proposed. Summary of the Invention

[0005] The purpose of this invention is to solve the practical technical defects, and a high-efficiency tubular heat exchanger and its operation control system are provided.

[0006] The objective of this invention can be achieved through the following technical solution: A high-efficiency tubular heat exchanger, comprising a tubular heat exchange structure connected to a flash tank pipeline, the tubular heat exchange structure comprising an S-shaped flow tube installed inside a heat exchange tube shell, an S-shaped heat exchange tube being sleeved inside the S-shaped flow tube, a heat exchange space being formed between the S-shaped flow tube and the S-shaped heat exchange tube, the S-shaped heat exchange tube comprising multiple parallel straight tube fin segments and bent tube straight sections installed at both ends of the straight tube fin segments, a pair of bent tube straight sections located at both ends being respectively connected to a heat medium inlet pipe and a heat medium outlet pipe extending to the outside of the S-shaped flow tube, and an exhaust pipe and an exhaust pipe respectively provided at both ends of the S-shaped flow tube, the exhaust pipe being connected to a drying hood; The outer wall of the straight tube fin segment is provided with multiple axial flow guides that are parallel to its axis and connected to its interior. The heat exchange space is equipped with spiral fins that are embedded and installed together with the straight tube fin segment and the axial flow guides.

[0007] Furthermore, the axial flow guide is arranged parallel to and protrudes axially from the straight tube fin segment. The planar cross-section of the axial flow guide is a triangular structure that intersects with the outer tube wall of the straight tube fin segment in an arc shape, including an arc-shaped intersection surface, a long inclined surface, and a short inclined surface.

[0008] Furthermore, the extension direction of the long inclined surface of the axial guide is adapted to the spiral direction of the airflow guided by the spiral fins, and the short inclined surface smoothly transitions to the tube wall of the straight tube fin segment. The spiral fins are provided with slots or connecting surfaces that match the shape of the axial guide, and are fixed to the axial guide by means of embedding, welding or brazing.

[0009] Furthermore, an operation control system for a high-efficiency tubular heat exchanger includes an operation control platform, a heat source supply and pressure stabilization module, and a hot air actual temperature control module. The operation control platform, serving as the data processing and command center of the system, is embedded with: The vehicle speed-steam demand database is established by simulating the steam demand conditions under different vehicle speeds and corresponding raw paper weights, and is used to map real-time vehicle speed to total steam demand load. Paper type-temperature database, which is grouped by paper type and basis weight, stores the corresponding hot air actual temperature reference set value; A temperature and humidity compensation algorithm model is used to calculate the compensation amount for the temperature reference setpoint based on the real-time ambient temperature and humidity. Flash tank pressure setpoint; The heat source supply and pressure stabilization module is used to receive the real-time speed signal from the paper machine, query the speed-steam demand database to obtain the predicted total steam demand load, generate a feedforward opening command for the flash tank outlet regulating valve, and collect the flash tank outlet main pipe pressure in real time, compare it with the flash tank pressure setpoint, generate a feedback regulation command through the PID control algorithm, and superimpose the feedforward opening command and the feedback regulation command to jointly control the opening of the flash tank outlet regulating valve. The hot air actual temperature control module is used to collect the actual hot air temperature and ambient temperature and humidity at the exhaust pipe outlet or downstream drying hood in real time. Based on the type and weight of paper currently being produced, it queries the paper type-temperature database to obtain the reference set value for the actual hot air temperature, and inputs the ambient temperature and humidity into the temperature and humidity compensation algorithm model to obtain the compensation amount. The reference set value is then corrected to obtain the target temperature. The target temperature is compared with the actual hot air temperature, and the opening of the regulating valve on the exhaust pipe is dynamically adjusted through a PID control algorithm.

[0010] Furthermore, the hot air actual temperature control module also executes the following control logic: continuously acquire the hot air actual temperature and target temperature at the same timestamp, establish hot air actual temperature trend curve and target temperature trend curve respectively in the same coordinate system with time as the x-axis and temperature as the y-axis, calculate the comprehensive temperature deviation value within a certain time window based on the hot air actual temperature trend curve and target temperature trend curve, compare the comprehensive temperature deviation value with the preset allowable deviation range, and when the temperature deviation value continues to exceed the preset allowable deviation range, generate a pressure coordinated intervention signal containing the intervention direction and the comprehensive temperature deviation value, and send it to the heat source supply and pressure stabilization module to request it to fine-tune the pressure setpoint of the flash tank.

[0011] Furthermore, the process of obtaining the comprehensive temperature deviation value specifically includes: calculating the average absolute deviation or integral absolute error within a set evaluation time window based on two trend curves as the comprehensive temperature deviation value.

[0012] Furthermore, after receiving the pressure coordination intervention signal, the heat source supply and pressure stabilization module first checks the intervention conditions to confirm that its own pressure is stable and the requested intervention direction is within the safe allowable adjustment range of the flash tank pressure setting value. Then, based on the comprehensive temperature deviation value, it makes directional fine adjustments to the flash tank pressure setting value in small fixed steps.

[0013] Optionally, the temperature and humidity compensation algorithm model is trained based on typical environmental parameters of historical environmental temperature and humidity (high temperature and high humidity in summer, low temperature and low humidity in winter) to correct the target temperature.

[0014] Compared with the prior art, the advantages of this invention are: 1. By combining the design of "intermittent spiral-corrugated fins" and "axial flow-guiding thermal bridge" on the traditional heat exchanger tube structure, the three-in-one innovation of heat conduction path reconstruction (thermal bridge in the flow guide), active flow field configuration (intermittent spiral + inclined flow guide) and anti-dust surface design (smooth transition between intermittent smooth tube and axial flow guide) effectively solves the defect of poor heat transfer in traditional heat exchanger tubes. While ensuring that the total heat dissipation area is not reduced, the air-side heat transfer coefficient is improved, and significant anti-dust accumulation capability is achieved.

[0015] 2. The operation control system includes a heat source supply and pressure stabilization module, a hot air actual temperature control module, and an integrated operation control platform. On the heat source side, feedforward adjustment is performed based on a pre-established "vehicle speed-steam demand" database, combined with pressure PID feedback, to ensure that the heat source pressure supplied to the heat exchanger is stable (fluctuation ≤ ±5%). On the heat user side, the target temperature is dynamically set based on a "paper type-temperature" database and a real-time environmental temperature and humidity compensation model, and the output hot air actual temperature accuracy reaches ±2℃ through closed-loop control. In addition, the system has an intelligent collaborative intervention mechanism between modules. When the temperature control has a continuous deviation, the heat source pressure setpoint can be automatically fine-tuned to form a global optimization. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the result of combining the flash tank with the tubular heat exchanger structure of the present invention. Figure 2 This is a cross-sectional view of the tubular heat exchange structure of the present invention; Figure 3 This is an internal cross-sectional view of the S-shaped flow tube of the present invention; Figure 4 This is a schematic diagram of the structure of the present invention, showing the combination of the straight tube fin segment, the spiral fin, and the axial flow guide. Figure 5 This is a top cross-sectional view of the combination of the straight tube fin segment, the spiral fin, and the axial flow guide of the present invention; Figure 6 This is a system principle block diagram of Embodiment 2 of the present invention; Figure 7 This is a logic control flowchart of the heat source supply and voltage stabilization module of the present invention; Figure 8 This is a flowchart illustrating the logic control of the hot air temperature control module of the present invention.

[0017] Explanation of the labels in the diagram: 1. Flash tank; 2. S-shaped flow tube; 3. S-shaped heat exchange tube; 31. Straight tube finned section; 32. Bent tube straight section; 33. Heat medium inlet pipe; 34. Heat medium outlet pipe; 4. Spiral fins; 5. Extraction pipe; 6. Exhaust pipe; 7. Axial guide 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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Example 1: This invention discloses a high-efficiency tubular heat exchanger. Please refer to [link / reference]. Figures 1-4 The tube heat exchange structure is connected to the flash tank 1. The tube heat exchange structure includes an S-shaped flow tube 2 installed in the heat exchange tube shell. An S-shaped heat exchange tube 3 is installed inside the S-shaped flow tube 2. A heat exchange space is formed between the S-shaped flow tube 2 and the S-shaped heat exchange tube 3. The S-shaped heat exchange tube 3 includes multiple parallel straight tube fin segments 31 and bent tube straight sections 32 installed at both ends of the straight tube fin segments 31. A pair of bent tube straight sections 32 at both ends are respectively connected to a heat medium inlet pipe 33 and a heat medium outlet pipe 34 extending to the outside of the S-shaped flow tube 2. The two ends of the S-shaped flow tube 2 are respectively provided with an exhaust pipe 5 and an exhaust pipe 6. The exhaust pipe 6 is connected to a drying hood. The flash steam outlet at the top and the high-temperature condensate outlet at the bottom of the flash tank 1 are connected in parallel or mixed through pipes and then connected to the heat medium inlet pipe 33 (i.e., the inlet of the heat exchanger pipe) of the tubular heat exchanger structure. Therefore, the "high-temperature fluid" flowing through the heat exchanger pipe is actually a two-phase heat medium from the flash tank 1, which is mainly flash steam and may be mixed with some high-temperature condensate. The flash tank 1 is a key device for heat recovery and pressure reduction. It converts high-grade waste heat (high-temperature condensate) into a low-grade heat source (flash steam) that can be stably utilized by the heat exchanger, providing a stable and controllable heat source for subsequent heat exchange. The outer wall of the straight tube fin segment 31 is provided with multiple axial flow guides 7 that are parallel to its axis and connected internally. The heat exchange space is equipped with spiral fins 4 that are embedded and installed together with the straight tube fin segment 31 and the axial flow guides 7. In the paper drying section, the high-speed movement of paper sheets releases fiber dust that floats in the workshop air. When the exhaust fan of the heat exchange system draws air from the workshop environment (or an area near the drying section) as a cold source, this dusty air is sent into the heat exchanger shell, scouring the heat exchange tubes and fins. Using intermittent spiral fins, the airflow velocity and direction change in the straight section of the 32mm smooth tube (the finless area), generating localized vortices that create a reverse scouring effect on the upstream fin tips, causing loosened paper dust to detach.

[0020] Please see Figures 4-5The axial flow guide 7 is arranged parallel to and protrudes axially from the straight tube fin segment 31. The planar cross section of the axial flow guide 7 is a triangular structure that intersects with the outer tube wall of the straight tube fin segment 31 in an arc shape, including an arc-shaped intersection surface, a long inclined surface, and a short inclined surface. The extension direction of the long inclined surface of the axial flow guide 7 is adapted to the spiral direction of the airflow guided by the spiral fin 4. The short inclined surface smoothly transitions to the tube wall of the straight tube fin segment 31. The spiral fin 4 is provided with a slot or connecting surface that matches the shape of the axial flow guide 7. It is fixed to the axial flow guide 7 by embedding, welding, or brazing. Multiple axial flow guides 7 distributed in rings on the outside of the straight tube fin segment 31 serve as an outwardly protruding heat transfer skeleton, forming a "thermal bridge" distributed along the axial direction of the straight tube fin segment 31. Its interior, together with the straight tube fin segment 31, serves as a heat conduction channel for low-pressure hot steam medium. It can directly obtain heat from the core of the tube wall and can be efficiently conducted to the fin area far from the tube wall through solid metal, fundamentally improving the temperature uniformity of the fin along the height direction and improving the fin efficiency. The spiral fins 4 are not directly wound on the smooth tube wall, but are embedded on the outer inclined surface of multiple axially arranged axial flow guides 7. The spiral fins 4 form a spiral corrugated structure on the outer wall of the straight tube fin segment 31. When the airflow flows along the spiral channel between the spiral fins 4, the airflow will experience a surface shape that changes periodically along the axis, thus disrupting the boundary layer. The addition of the axial flow guides 7 forms a multi-stage heat conduction path of "tube wall-flow guides-fins". The heat source of the fins is no longer limited to the tube wall contact line, but is "injected at multiple points" through multiple flow guides, which greatly reduces the thermal resistance of the fins, making the overall temperature of the fins higher and more uniform, and significantly enhancing the heat exchange capacity. Based on axial heat guidance, the long inclined surface matches the spiral direction of the airflow, which can continuously guide and "comb" the airflow to avoid separation. At the same time, it generates directional and continuous micro-disturbances to the airflow, just like arranging a series of micro-vortex generating structures in the spiral downward / downward heat exchange space, which effectively destroys the thermal boundary layer. In addition, the smooth transition of the short inclined surface avoids the airflow stagnation zone and dust "trap" formed in the right-angle area at the root of the traditional fin, making it difficult for paper dust to adhere and accumulate. In addition, the axial flow guide 7, as an axial reinforcing rib, can significantly enhance the mechanical strength of the straight tube fin segment 31. The embedded structure makes the connection between the spiral fin 4 and the straight tube fin segment 31 more solid, and the vibration resistance and thermal fatigue performance are better. By upgrading and modifying traditional heat exchangers, while ensuring the total heat dissipation area is ≥95% of the original area, the frontal area is reduced by 15%-20%, and the hot air velocity is increased from 1.2m / s to 1.5-1.8m / s. The traditional fin structure is replaced with a spiral corrugated composite fin, aiming to improve the heat dissipation efficiency by more than 10% compared to the original design, and achieve a heat transfer coefficient ≥35W / (m²). K), and reduce paper dust accumulation.

[0021] In this embodiment, high-temperature and high-pressure condensate is depressurized and flash-evaporated in flash tank 1 to generate low-pressure steam. The tubular heat exchanger uses this low-pressure steam or high-temperature condensate as a heat source to heat the air drawn from the workshop. The hot air is then sent back to the drying section to assist in drying. The traditional heat exchange tube structure is designed with a combination of "intermittent spiral-corrugated fins" and "axial flow guide heat bridge". Through the three-in-one innovation of heat conduction path reconstruction (flow guide heat bridge), active flow field configuration (intermittent spiral + inclined flow guide), and anti-dust surface design (smooth transition of intermittent smooth tube and axial flow guide), the defect of poor heat transfer in traditional heat exchange tubes is effectively solved. While ensuring that the total heat dissipation area is not reduced, the air-side heat transfer coefficient is improved, and a significant anti-dust accumulation capability is achieved.

[0022] Example 2: This invention also proposes an operation control system for a high-efficiency tubular heat exchanger. This system is applied to the aforementioned high-efficiency tubular heat exchanger. Please refer to [link / reference]. Figures 6-8 It includes an operation control platform, a heat source supply and pressure stabilization module, and a hot air actual temperature control module; The operation control platform, serving as the data processing and command center of the system, is embedded with: The vehicle speed-steam demand database is established by simulating the steam demand conditions under different vehicle speeds and corresponding raw paper weights, and is used to map real-time vehicle speed to total steam demand load. Paper type-temperature database, which is grouped by paper type and basis weight, stores the corresponding hot air actual temperature reference set value; The temperature and humidity compensation algorithm model is used to calculate the compensation amount of the temperature benchmark setpoint based on the real-time ambient temperature and humidity. The temperature and humidity compensation algorithm model is trained based on typical environmental parameters of historical ambient temperature and humidity (high temperature and high humidity in summer, low temperature and low humidity in winter) to correct the target temperature. Flash tank pressure setpoint; The heat source supply and pressure stabilization module is used to receive the real-time speed signal from the paper machine and query the speed-steam demand database to obtain the predicted total steam demand load. Based on this, it generates a feedforward opening command for the regulating valve at the outlet of the flash tank. For example, if there is a corresponding record for the real-time speed, the corresponding preset valve opening is directly retrieved as the feedforward command. If it is between records, it is calculated by linear interpolation and other methods. The system collects the pressure of the main outlet pipe of the flash tank in real time, compares it with the pressure setpoint of the flash tank, obtains the pressure deviation, and generates a feedback adjustment command based on the pressure deviation through the PID control algorithm. This command represents "the amount of adjustment that needs to be made on the current valve opening in order to correct the current pressure deviation to zero". The feedforward opening command and the feedback adjustment command are superimposed to jointly control the opening of the regulating valve at the outlet of flash tank 1. The feedforward opening command provides a "reference opening" that matches the current operating conditions. The feedback adjustment command makes "fine adjustments" on this reference to compensate for all subtle changes that the feedforward cannot predict. This can quickly suppress pressure fluctuations caused by changes in vehicle speed, achieve pressure stability, and keep the pressure fluctuations of the hot fluid supplied to the heat exchanger within ±5% of the set value, thus achieving automatic balance between the steam used for main drying of the drying cylinder and the steam used for heat exchanger recovery. The hot air actual temperature control module is used to precisely control the actual temperature of the hot air output from the high-efficiency tubular heat exchanger. It executes the following control logic: real-time acquisition of the actual temperature of the hot air at the outlet of exhaust pipe 6 or the downstream drying hood and the ambient temperature and humidity; based on the type and weight of paper currently being produced, querying the paper type-temperature database to obtain the reference set value of the actual hot air temperature; inputting the ambient temperature and humidity into the temperature and humidity compensation algorithm model to obtain the compensation amount; correcting the reference set value to obtain the target temperature; comparing the target temperature with the actual hot air temperature; and dynamically adjusting the opening of the regulating valve on exhaust pipe 6 through the PID control algorithm to change the hot air flow rate or mixing ratio, so that the actual hot air temperature is stabilized within ±2℃ of the target temperature. The above-mentioned parts employ the PID control algorithm, which is a "closed-loop feedback" controller: by continuously measuring the "result" and comparing it with the "target", the "action" is adjusted to narrow the gap with the target.

[0023] The hot air actual temperature control module also executes the following control logic: continuously acquire the hot air actual temperature and target temperature at the same timestamp, establish the hot air actual temperature trend curve and the target temperature trend curve in the same coordinate system with time as the x-axis and temperature as the y-axis, and calculate the comprehensive temperature deviation value within a certain time window based on the hot air actual temperature trend curve and the target temperature trend curve. The process of obtaining the comprehensive temperature deviation value specifically includes: calculating the average absolute deviation or integral absolute error within a set evaluation time window (such as 60 seconds) based on the two trend curves as the comprehensive temperature deviation value. The system compares the overall temperature deviation with the preset allowable deviation range. When the temperature deviation continues to exceed the preset allowable deviation range, a pressure-coordinated intervention signal containing the intervention direction and the overall temperature deviation value is generated and sent to the heat source supply and pressure stabilization module, requesting it to fine-tune the flash tank pressure setpoint. If the temperature deviation continues to exceed the limit and the adjustment is ineffective, the system will determine that it may be caused by fluctuations on the heat source side, and then send a pressure-coordinated intervention signal instruction to form cross-module coordination, eliminating the temperature deviation from the root cause. That is, through the coordinated intervention mechanism, the system can automatically perform auxiliary adjustment from the heat source side when the end regulating valve capacity is saturated, thereby coping with larger process disturbances and achieving precise temperature control over a wider operating range. Upon receiving a pressure-coordinated intervention signal, the heat source supply and pressure stabilization module first checks the intervention conditions to confirm that its own pressure is stable and the requested intervention direction is within the safe adjustment range of the flash tank pressure setpoint. Then, based on the overall temperature deviation value, it performs directional fine-tuning of the flash tank pressure setpoint in small, fixed steps (e.g., adjusting the original setpoint by 0.5%-1% each time). After fine-tuning, it enters an observation period. During this period, it continuously monitors the overall temperature deviation value from the hot air actual temperature control module. If the overall temperature deviation value shows a clear decreasing trend and returns to the allowable range, it is considered that one or more coordinated interventions have been successful. If the hot air actual temperature deviation value does not return after the number of consecutive fine-tunings reaches the preset upper limit, it is determined to be a fault that cannot be resolved by pressure adjustment (e.g., severe dust accumulation in the heat exchanger, valve failure, etc.), and the intervention is terminated and an alarm is triggered. Through this coordinated intervention mechanism, the system can automatically perform auxiliary adjustment from the heat source side when the capacity of the terminal regulating valve is saturated, thereby coping with larger process disturbances and achieving precise temperature control over a wider operating range.

[0024] This invention designs multiple threshold comparisons. The threshold, or preset value, preset range, etc., are set for result comparison and analysis to determine good or bad. The magnitude of the threshold is set, entered, and stored based on a combination of large-scale model analysis of sample data and human experience. It can also be appropriately adjusted based on seasonal or common-sense influencing conditions.

[0025] In summary, this high-efficiency tubular heat exchanger improves upon traditional heat exchange tubes by employing an S-shaped arrangement of heat exchange tube bundles. The core improvement lies in the external reinforcement structure. Multiple axially extending flow guides are provided on the outer wall of the straight tube finned segment 31. These flow guides are internally connected to the tube cavity of the straight tube finned segment 31 and have a specific beveled shape. The spiral fins are not directly wound around the tube wall but are embedded in multiple axial flow guides, forming a multi-stage high-efficiency heat conduction path of "tube wall-flow guide-fins," fundamentally improving fin temperature uniformity and efficiency. Simultaneously, intermittently arranged spiral-corrugated composite fins are used, forming a bend-through section 32 between the straight tube finned segments 31. Through the synergistic effect of the spiral corrugated flow guide and the beveled turbulence composite structure, the gas-side heat transfer coefficient is improved while achieving significant anti-dust accumulation capability. The operation control system includes a heat source supply and pressure stabilization module, a hot air actual temperature control module, and an integrated operation control platform. On the heat source side, feedforward adjustment is performed based on a pre-established "vehicle speed-steam demand" database, combined with pressure PID feedback, to ensure stable heat source pressure supplied to the heat exchanger (fluctuation ≤ ±5%). On the heat consumption side, the target temperature is dynamically set based on a "paper type-temperature" database and a real-time environmental temperature and humidity compensation model, and closed-loop control is used to ensure that the actual output hot air temperature accuracy reaches ±2℃. In addition, the system has an intelligent collaborative intervention mechanism between modules. When a continuous deviation occurs in temperature control, the heat source pressure setpoint can be automatically fine-tuned to form global optimization.

[0026] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto; any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency tubular heat exchanger, comprising a tubular heat exchange structure connected to a flash tank (1) via piping, characterized in that: The tubular heat exchange structure includes an S-shaped flow tube (2) installed inside the heat exchange tube shell. An S-shaped heat exchange tube (3) is installed inside the S-shaped flow tube (2). A heat exchange space is formed between the S-shaped flow tube (2) and the S-shaped heat exchange tube (3). The S-shaped heat exchange tube (3) includes multiple parallel straight tube fin segments (31) and bent tube straight sections (32) installed at both ends of the straight tube fin segments (31). A pair of bent tube straight sections (32) at both ends are respectively connected to a heat medium inlet pipe (33) and a heat medium outlet pipe (34) extending to the outside of the S-shaped flow tube (2). The two ends of the S-shaped flow tube (2) are respectively provided with an exhaust pipe (5) and an exhaust pipe (6). The exhaust pipe (6) is connected to a drying hood. The outer wall of the straight tube fin segment (31) is provided with a plurality of axial flow guides (7) that are parallel to its axis and connected to its interior. The heat exchange space is provided with spiral fins (4) that are embedded together with the straight tube fin segment (31) and the axial flow guides (7).

2. The high-efficiency tubular heat exchanger according to claim 1, characterized in that: The axial flow guide (7) is arranged axially parallel to the straight tube fin segment (31) and protrudes axially. The top cross section of the axial flow guide (7) is a triangular structure that intersects with the outer tube wall of the straight tube fin segment (31) in an arc shape, including an arc-shaped intersection surface, a long inclined surface, and a short inclined surface.

3. The high-efficiency tubular heat exchanger according to claim 2, characterized in that: The extension direction of the long inclined surface of the axial flow guide (7) is adapted to the spiral direction of the airflow guided by the spiral fin (4), and the short inclined surface smoothly transitions to the tube wall of the straight tube fin segment (31). The spiral fin (4) is provided with a slot or connecting surface that matches the shape of the axial flow guide (7), and is fixed to the axial flow guide (7) by embedding, welding or brazing.

4. An operation control system for a high-efficiency tubular heat exchanger, wherein the system is applied to the high-efficiency tubular heat exchanger described in claim 3, characterized in that, This includes an operation control platform, a heat source supply and pressure stabilization module, and a hot air actual temperature control module; The operation control platform, serving as the data processing and command center of the system, is embedded with: The vehicle speed-steam demand database is established by simulating the steam demand conditions under different vehicle speeds and corresponding raw paper weights, and is used to map real-time vehicle speed to total steam demand load. Paper type-temperature database, which is grouped by paper type and basis weight, stores the corresponding hot air actual temperature reference set value; A temperature and humidity compensation algorithm model is used to calculate the compensation amount for the temperature reference setpoint based on the real-time ambient temperature and humidity. Flash tank pressure setpoint; The heat source supply and pressure stabilization module is used to receive the real-time speed signal from the paper machine, query the speed-steam demand database to obtain the predicted total steam demand load, generate a feedforward opening command for the flash tank outlet regulating valve, and collect the flash tank outlet main pipe pressure in real time, compare it with the flash tank pressure setpoint, generate a feedback regulation command through the PID control algorithm, and superimpose the feedforward opening command and the feedback regulation command to jointly control the opening of the flash tank outlet regulating valve. The hot air actual temperature control module is used to collect the hot air actual temperature and ambient temperature and humidity at the outlet of the exhaust pipe (6) or the downstream drying hood in real time. Based on the paper type and weight currently being produced, it queries the paper type-temperature database to obtain the hot air actual temperature reference setting value, and inputs the ambient temperature and humidity into the temperature and humidity compensation algorithm model to obtain the compensation amount. It then corrects the reference setting value to obtain the target temperature, compares the target temperature with the hot air actual temperature, and dynamically adjusts the opening of the regulating valve on the exhaust pipe (6) through the PID control algorithm.

5. The operation control system for a high-efficiency tubular heat exchanger according to claim 4, characterized in that: The hot air actual temperature control module also executes the following control logic: continuously acquire the hot air actual temperature and target temperature at the same timestamp, establish hot air actual temperature trend curve and target temperature trend curve respectively in the same coordinate system with time as the x-axis and temperature as the y-axis, calculate the comprehensive temperature deviation value within a certain time window based on the hot air actual temperature trend curve and target temperature trend curve, compare the comprehensive temperature deviation value with the preset allowable deviation range, and when the temperature deviation value continues to exceed the preset allowable deviation range, generate a pressure coordinated intervention signal containing the intervention direction and the comprehensive temperature deviation value, and send it to the heat source supply and pressure stabilization module to request it to fine-tune the pressure set value of the flash tank.

6. The operation control system for a high-efficiency tubular heat exchanger according to claim 5, characterized in that: The process of obtaining the comprehensive temperature deviation value specifically includes: calculating the average absolute deviation or integral absolute error within a set evaluation time window based on two trend curves as the comprehensive temperature deviation value.

7. The operation control system for a high-efficiency tubular heat exchanger according to claim 6, characterized in that: After receiving the pressure coordination intervention signal, the heat source supply and pressure stabilization module first checks the intervention conditions to confirm that its own pressure is stable and the requested intervention direction is within the safe adjustment range of the flash tank pressure setting value. Then, based on the comprehensive temperature deviation value, it makes directional fine adjustments to the flash tank pressure setting value in small fixed steps.

8. The operation control system for a high-efficiency tubular heat exchanger according to claim 4, characterized in that: The temperature and humidity compensation algorithm model is trained based on typical environmental parameters of historical environmental temperature and humidity (high temperature and high humidity in summer, low temperature and low humidity in winter) to correct the target temperature.

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