High-efficiency and energy-saving conveying method for large-diameter heat distribution pipeline based on phase change heat preservation

Abstract

The invention discloses an efficient and energy-saving conveying method for a large-diameter heat distribution pipeline based on phase change heat preservation, relates to the field of heat distribution pipeline conveying, and solves the problems that an existing pipeline is poor in heat preservation, high in energy consumption and inaccurate in regulation and control. The method is characterized in that a stepped phase change heat preservation layer, a vacuum filling auxiliary heat preservation layer and an outer protection layer are sequentially laid on the outer wall of a pipeline working pipe; the cascade phase change heat preservation layer is subjected to segmented adaptation according to the axial temperature attenuation rule, and dynamic temperature compensation is achieved; the electrical intelligent regulation and control system collects temperature and pressure data through distributed monitoring nodes, generates an instruction through a PID gain calibration model of a regulation and control terminal, and controls equipment to operate accurately. The number of heat compensation stations is reduced by optimizing the conveying process. The heat preservation performance is remarkably improved, heat loss is reduced, intelligent and accurate regulation and control are achieved, energy consumption and operation and maintenance cost are reduced, the long-distance large-flow heat supply requirement is met, and practicability is high.

Description

Technical Field

[0001] This invention relates to the field of heat transport technology, specifically to a high-efficiency and energy-saving heat transport method for large-diameter heat pipelines based on phase change insulation. Background Technology

[0002] Urban centralized heating systems and industrial heat transmission networks are important components of modern energy infrastructure. Large-diameter heat pipelines (DN≥400mm), due to their large flow capacity and wide coverage, have become the core carrier for long-distance heat transmission and are widely used in projects such as inter-regional heating and industrial waste heat recovery. With the advancement of my country's energy conservation and emission reduction policies, the demand for energy-efficient and high-efficiency heat transmission is becoming increasingly urgent. The integration of insulation and control technologies is key to reducing pipeline heat loss and improving energy utilization, and has become a current research focus in the field of heat pipeline technology.

[0003] In actual operation, pipeline heat loss is affected by external factors such as ambient temperature, wind speed convection, soil thermal conductivity, laying depth, and surface moisture content, as well as internal factors such as local thermal bridging effects at pipe joints, flanges, elbows, tees, insulation layer splicing gaps, and material aging and degradation. Heat loss exhibits dynamic fluctuation characteristics, further aggravating the energy consumption and temperature fluctuations of the heating system.

[0004] Currently, the insulation of large-diameter heating pipelines mainly adopts traditional passive insulation technology, such as wrapping with polyurethane and rock wool insulation materials. Control is mostly done manually, which has several technical limitations: First, traditional insulation materials can only delay heat loss and do not have heat storage and release capabilities. They cannot adapt to the fluctuations in heating system load over time and ambient temperature, and lack effective intelligent electrical control methods. This leads to frequent adjustments of the heat source to adapt to load changes, reducing operating efficiency and causing significant energy waste. Statistics show that the overall energy utilization rate of traditional heating systems is only 60%-70%, far below the theoretical level. Second, when large-diameter pipelines are used for long-distance transmission, even with thicker traditional insulation layers, the temperature drop is still very significant. For pipelines above DN400, a 5-day temperature drop is still required. When transporting over 1,000 kilometers, heating stations are often required along the way to supplement heat, which significantly increases initial investment, land area, and operation and maintenance costs. Third, traditional insulation materials have poor interfacial bonding with pipelines, making them prone to detachment and aging. Furthermore, leakage problems are likely to occur during the solid-liquid phase change process, contaminating the insulation layer and reducing mechanical strength. After long-term use, the insulation performance will significantly deteriorate. Fourth, there is a lack of precise electrical monitoring and intelligent control mechanisms, making it impossible to capture changes in the temperature and pressure of the medium inside the pipeline in real time. This makes it difficult to smooth out temperature fluctuations in the pipeline network. When the heat source temperature changes, the temperature fluctuation at the user end can reach ±8℃ or even higher, seriously affecting the comfort of heating.

[0005] Phase change materials (PCMs) are widely used in building energy conservation and other fields due to their ability to absorb or release large amounts of latent heat at specific temperatures. However, combining PCMs with intelligent electrical control technology for the insulation and transportation of large-diameter thermal pipelines still faces many technical challenges, and existing technologies have not yet formed an effective integration solution: current research focuses mainly on low-temperature application scenarios (usually below 60℃), lacking systematic research on the long-term stability, heat resistance, and cycle life of PCMs under the high-temperature conditions (80-150℃) required for heating pipelines; materials with a single phase change temperature cannot adapt to the temperature decay law along the pipe of large-diameter pipelines, nor can they cope with dynamic heat loss changes under the coupling of multiple factors, resulting in limited insulation effects; PCMs have poor chemical compatibility with traditional insulation materials, easily leading to phase separation and reducing overall insulation performance; furthermore, existing PCM insulation solutions mostly rely on external energy supply, failing to achieve deep integration with electrical monitoring and intelligent control, resulting in low system control accuracy, slow response, complex structure, and high installation and maintenance costs, making it difficult to meet the needs of practical engineering applications; more importantly, existing technologies have not yet achieved "cascaded phase change insulation, real-time electrical monitoring, ... The integrated design of "PID intelligent closed-loop control" lacks a quantitative matching formula for the temperature decay along the pipe of large-diameter pipelines, and no field calibration model for the PID gain coefficient has been established, which makes it difficult to coordinate the heat preservation effect and the control accuracy, resulting in a significant technological gap.

[0006] In summary, there is an urgent need for a high-efficiency and energy-saving method for transporting large-diameter heat pipelines based on phase change insulation. This method would deeply integrate composite phase change insulation technology with electrical monitoring and intelligent control technology to achieve high-efficiency insulation, dynamic heat storage and release, and precise intelligent control of heat pipelines, thereby reducing heat loss and operating costs and improving the stability and energy efficiency of heat transport. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical problems of poor insulation, serious heat loss, low energy utilization, large temperature fluctuation in existing large-diameter thermal pipelines, as well as the disconnect between the application of phase change materials and electrical control, and the lack of an integrated solution, and to provide a high-efficiency and energy-saving transportation method for large-diameter thermal pipelines based on phase change insulation.

[0008] The technical solution of this invention is: a high-efficiency and energy-saving transportation method for large-diameter thermal pipelines based on phase change insulation, comprising the following steps: S1. Pipeline Insulation System Adaptation Design: A multi-layer insulation system adapted to large-diameter thermal pipelines is pre-constructed. The specific specifications of the large-diameter thermal pipelines can be determined according to actual working conditions, covering commonly used specifications and adapting to long-distance, high-load transportation scenarios. The insulation system, from the inside out, corresponds to the working pipe, a stepped phase change insulation layer, an auxiliary insulation layer, and an outer protective layer. Each layer is sealed with a high-temperature resistant sealant to ensure no gaps or leaks, preventing external air and moisture from entering the insulation system and avoiding a decrease in insulation performance. This also lays the foundation for the subsequent installation and wiring of electrical monitoring nodes and the operation of the intelligent control system, ensuring that electrical components are not affected by the external environment. This step combines the calculation logic of electrical control requirements and temperature decay matching formulas to design the insulation system, breaking the limitations of traditional insulation systems that only focus on insulation effects and ignore control adaptability, achieving synergistic adaptation between insulation and control.

[0009] S2. Screening and Preparation of Composite Phase Change Insulation Materials: Based on the operating temperature range (80-150℃) of large-diameter thermal pipelines, suitable composite phase change materials are screened. The core is to ensure that the phase change temperature range of the material matches the operating temperature of the medium inside the pipeline, specifically the phase change temperature range (t1+δt, t2−δt), where t1 is the saturated steam temperature inside the pipeline under steady-state conditions, t2 is the operating temperature of the pipeline under steady-state conditions, and δt = 5~10℃. This ensures that the phase change material can effectively store and release heat during normal pipeline operation, fully leveraging the advantages of phase change insulation and providing a stable insulation foundation for intelligent electrical control. The composite phase change material ensures that its heat storage and release capacity and thermal conductivity meet engineering requirements.

[0010] Preferably, the composite phase change material uses molten salt or sugar alcohol materials as the base material. Molten salt materials are suitable for high-temperature conditions (120-150℃), while sugar alcohol materials are suitable for medium-temperature conditions (80-120℃), and can be flexibly selected according to the actual operating temperature of the pipeline. To solve the problems of low thermal conductivity, easy leakage, and poor stability of single phase change materials, functional additives are added to the base material: the thermal conductivity enhancer is one or more of graphene, carbon fiber, or metal powder, added at 3%-8% of the base material mass, to improve the thermal conductivity of the phase change material and accelerate heat transfer efficiency; the leak-proof agent is silicone resin or polymer sealant, added at 2%-5% of the base material mass, to prevent leakage of the phase change material during the solid-liquid phase change process and contamination of the insulation layer; the stability regulator is hydroxystearic acid or polyethylene glycol, added at 1%-3% of the base material mass, to improve the cycle stability of the phase change material and extend its service life. This step involves selecting suitable composite phase change materials for high-temperature operating conditions in large-diameter pipelines. By optimizing the ratio of functional additives, it addresses the technical pain points of traditional phase change materials, such as poor stability and easy leakage under high-temperature conditions, and provides material support for subsequent collaborative work with electrical control.

[0011] Preferably, the preparation process of the composite phase change material is as follows: the base material is placed in a melting furnace and heated to melt at a temperature of 120-180℃. After stirring evenly, the thermal conductivity enhancer, the leak-proof agent and the stability regulator are added in sequence. Stirring is continued for 30-60 minutes to ensure that the components are evenly mixed. Then, it is poured into a mold, cooled and solidified to obtain the desired phase change insulation unit base material, which has good chemical compatibility with auxiliary insulation materials such as polyurethane and does not undergo phase separation.

[0012] S3. Construction of the stepped phase change insulation layer: The prepared composite phase change material is processed into insulation units that fit the working pipe. The units are then attached to the outer wall of the working pipe using a tongue-and-groove splicing method to form a complete stepped phase change insulation layer. The tongue-and-groove splices are sealed with high-temperature resistant sealant to ensure no gaps and prevent heat loss from the splices. This ensures the continuity and integrity of the insulation, provides a guarantee for the accuracy of electrical monitoring, and avoids deviations in monitoring data due to local insulation failure.

[0013] Furthermore, to adapt to the temperature decay of the medium along the pipeline during long-distance transportation in large-diameter pipelines, the tiered phase change insulation layer is divided into multiple insulation sections along the pipeline axis. The phase change temperature of the composite phase change material in each insulation section is calculated and determined using a dynamic temperature decay matching formula, achieving precise temperature adaptation along the pipeline and solving the problem of limited insulation effect of traditional single phase change temperature insulation. This formula can accurately calculate the target temperature of the medium in each insulation section, thereby determining the phase change temperature of the corresponding insulation material, ensuring that the heat storage and release characteristics of the phase change material are perfectly matched with the temperature drop pattern along the pipeline, maximizing the energy-saving effect of phase change insulation. The insulation unit is sealed to ensure no leakage of the phase change material, and the filling rate of the phase change material in the sealed space is ≥95%, ensuring that the heat storage and release capacity meets the pipeline insulation requirements and providing support for the efficient operation of electrical intelligent control. This step achieves precise design of the tiered phase change temperature through a quantitative formula.

[0014] S4. Auxiliary Insulation and External Protection Construction: An auxiliary insulation layer is laid outside the tiered phase change insulation layer. This auxiliary insulation layer employs a combination structure of a vacuum insulation layer and an insulation material filling layer. The vacuum insulation layer is positioned close to the tiered phase change insulation layer, utilizing the vacuum environment to block heat conduction and further reduce heat loss. The insulation material filling layer uses one or more of aerogel, rock wool, or polyurethane. Aerogel has an extremely low thermal conductivity (≤0.015W / (m·K)), suitable for scenarios requiring high insulation performance. Rock wool and polyurethane offer advantages such as low cost and convenient construction, allowing for flexible selection based on project budget and insulation requirements. The overall thermal conductivity of the auxiliary insulation layer is ≤0.03W / (m·K), with a thickness of 30-80mm, adjustable according to the nominal pipe diameter and transport distance, further enhancing insulation performance and reducing the load on electrical control systems.

[0015] Furthermore, an outer protective layer is constructed outside the auxiliary insulation layer. This layer uses corrosion-resistant, wear-resistant, and anti-aging materials, and is formed through sealed splicing to create a complete protective layer. This prevents external moisture and impurities from entering the insulation layer, avoiding moisture absorption and aging of the insulation material, extending the service life of the insulation system. Simultaneously, it protects the electrical monitoring nodes, wiring, and other components inside the insulation layer from corrosion in complex outdoor and underground environments, ensuring the long-term stable operation of the intelligent electrical control system. The outer protective layer is 10-20mm thick, possessing good impact resistance and adaptable to the usage requirements of different laying scenarios. This step combines the protection requirements of the electrical monitoring components to design the outer protective layer, achieving an integrated approach to insulation, protection, and control component protection.

[0016] S5. Operation of the Electrical Intelligent Control System: Electrical monitoring nodes are set up every 1-2 km along the pipeline. Each monitoring node integrates a temperature sensor, a pressure sensor, a wireless transmission module, and a data acquisition unit. The temperature sensor is used to collect the temperature of the medium inside the pipeline, the temperature inside and outside the stepped phase change insulation layer, and the temperature outside the auxiliary insulation layer in real time. The pressure sensor is used to collect the pressure of the medium inside the pipeline in real time. The data acquisition unit converts the analog signals collected by the sensors into digital electrical signals, which are then transmitted to the intelligent control terminal via the wireless transmission module (using LoRa or 5G communication protocols to ensure transmission stability and low latency).

[0017] Furthermore, the intelligent control terminal incorporates a PID control algorithm, a data processing unit, and a signal output unit. The data processing unit performs noise reduction, analysis, and processing on the received electrical signals to accurately determine the changing trends of the medium temperature and pressure within the pipeline, as well as the heat storage and release state of the phase change material. The PID control algorithm, based on a preset temperature threshold (±2℃) and combined with a PID control gain coefficient calibration model, adaptively generates electrical control signals for pipeline flow rate and pressure, which are transmitted to the pipeline transport control equipment through the signal output unit to achieve dynamic control. This calibration model can calibrate the PID gain coefficient in real time based on temperature deviation and the rate of change of deviation, solving the problems of fixed parameters, poor adaptability, and lag in traditional PID control, ensuring that the control accuracy is precisely matched with the heat storage and release characteristics of the phase change material. When the temperature of the medium inside the pipeline is higher than the phase change temperature of the corresponding phase change material, a deceleration control signal is output to slow down the medium flow rate, allowing the phase change material to fully absorb and store excess heat, thus avoiding heat waste. When the medium temperature is lower than the phase change temperature of the corresponding phase change material, the heat released during the solidification of the phase change material is used to maintain a stable medium temperature. Simultaneously, a supplementary heating control signal is output to reduce the frequency of intermediate heating, and may even eliminate some intermediate heating stations, reducing operating costs. Furthermore, the intelligent control terminal enables remote monitoring. When abnormal temperature or pressure is detected, or when excessive heat loss is caused by insulation layer damage, an alarm electrical signal is promptly output to alert personnel for handling, improving operational efficiency. This process achieves a closed-loop operation of "real-time monitoring - data processing - intelligent control - heat storage and release coordination," deeply integrating the precision of electrical control with the heat storage and release advantages of phase change materials.

[0018] S6. Full Lifecycle Operation and Maintenance Management: Establish a comprehensive full lifecycle operation and maintenance management system, combining insulation performance maintenance with electrical system maintenance to ensure long-term stable operation of pipelines: Regularly conduct sealing and performance tests on the pipeline insulation layer. The sealing test uses the vacuum pressure test method to detect whether there is a leak in the insulation layer; the performance test uses the heat flow meter method to measure the heat loss per unit length of the pipeline. When the heat loss exceeds 150W / m, promptly investigate and deal with problems such as insulation layer damage and sealing failure.

[0019] Furthermore, the performance of the composite phase change material in the cascade phase change insulation layer is re-inspected every 1-2 years, testing key performance indicators such as latent heat of phase change and thermal conductivity. Materials with performance degradation exceeding 10% are replenished or replaced. Simultaneously, the sensor accuracy of the electrical monitoring nodes is calibrated periodically, and the signal stability of the wireless transmission module, the conversion accuracy of the data acquisition unit, and the algorithm operation status of the intelligent control terminal are checked. Faulty electrical components are repaired or replaced promptly. When the auxiliary insulation layer and outer protective layer are damaged or aged, they are repaired or replaced in a timely manner to ensure the integrity of the insulation system and avoid damage to internal electrical components. A pipeline operation database is established to record data such as temperature, pressure, heat loss, electrical control parameters (including the gain coefficient after PID calibration), and operation and maintenance records. Data analysis is used to optimize the intelligent control algorithm parameters, achieving energy-saving operation and maintenance throughout the entire life cycle, further improving the energy efficiency and stability of pipeline transportation. This step integrates insulation operation and maintenance with electrical control system operation and maintenance, ensuring the long-term stable operation of the "insulation-monitoring-control" system.

[0020] The beneficial effects of this invention are: 1. This application combines electrical monitoring, wireless transmission, PID intelligent algorithm and cascade phase change heat storage and release technology. It achieves quantitative and precise control through dynamic temperature decay matching formula and PID control gain coefficient calibration model, and constructs an integrated closed-loop method of "insulation-monitoring-control". It solves the technical problems of disconnection between phase change insulation and electrical control, control lag and limited insulation effect in the existing technology, and fills the technical gap of "precise insulation and intelligent control" integration for large-diameter thermal pipelines.

[0021] 2. Significantly improved insulation effect and greatly reduced heat loss: The composite insulation method combining tiered phase change insulation and auxiliary insulation is adopted. The phase change material can achieve dynamic heat storage and release. The tiered design adapts to the temperature decay law along the pipeline through a quantitative formula, which can resist the dynamic heat loss fluctuations caused by multiple factors such as environment, structure and materials. Combined with efficient insulation technology such as vacuum insulation, the heat loss per unit length of large-diameter pipeline can be significantly reduced, which is 30%-50% lower than the traditional insulation method. This greatly improves energy utilization, meets the requirements of energy conservation and emission reduction, and is superior to the existing single insulation technology.

[0022] 3. Precise temperature control and significantly improved delivery stability: Through the synergistic effect of the electrical intelligent control system and the cascade phase change insulation, the constant temperature heat absorption and release characteristics of the phase change material and the precision of electrical control are utilized. Combined with the PID gain coefficient calibration model, the temperature fluctuation of the medium in the pipeline is controlled within ±2℃, avoiding excessive temperature fluctuations at the user end and improving heating comfort. At the same time, the frequency of intermediate heat replenishment is reduced, and even some intermediate heating stations can be eliminated, reducing initial investment and operation and maintenance costs, and solving the pain points of lagging temperature control and large fluctuations in existing technologies.

[0023] 4. Stable performance and long service life of phase change materials: By selecting composite phase change materials suitable for high-temperature working conditions and adding functional additives in a scientific ratio, the problems of easy leakage, poor stability and poor thermal conductivity of traditional phase change materials are solved. Composite phase change materials have a long cycle life and can be reused. After performance repair, they can continue to be used, reducing material replacement costs and breaking through the technical limitations of existing phase change materials with short service life under high-temperature working conditions in large-diameter pipelines.

[0024] 5. Convenient construction, wide adaptability, and efficient operation and maintenance: Utilizing modular insulation units and standardized construction processes, tongue-and-groove splicing and sealing treatments are convenient and efficient, adapting to large-diameter heating pipes of DN400 and above; the external protection construction method is suitable for complex laying environments such as outdoor and underground installations, applicable to various scenarios such as urban centralized heating and industrial waste heat transportation; the intelligent electrical control system enables remote monitoring and fault alarms, and combined with regular operation and maintenance, significantly improves operation and maintenance efficiency and reduces operation and maintenance costs, surpassing existing technology operation and maintenance models.

[0025] 6. Zero-energy self-operation with outstanding energy-saving benefits: The pipeline utilizes its own heat source to achieve the circulation and heat storage of the phase change insulation layer, forming a zero-energy self-operation mode without the need for additional energy consumption; combined with intelligent electrical control to optimize transmission parameters, the operating energy consumption is further reduced. Taking a 100km long, DN1600mm large-diameter pipeline as an example, it can reduce standard coal consumption by hundreds of thousands of tons and carbon dioxide emissions by more than one million tons per year. The energy-saving and environmental benefits are significant and superior to existing heat transmission methods. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the segmentation and temperature decay of the stepped phase change insulation layer of the present invention. Figure 2 This is a block diagram of the intelligent control system architecture of the present invention. Detailed Implementation

[0027] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0028] Example 1: This embodiment targets a DN1600mm large-diameter thermal pipeline for cross-regional industrial waste heat transportation. The pipeline operates at a temperature of 130-140℃, and the transportation distance is 100km. The high-efficiency, energy-saving transportation method based on phase change insulation, as described in this invention, is employed. The specific steps are as follows: S1. Pipe insulation system adaptation design A multi-layer insulation system adapted to DN1600mm large-diameter pipes is pre-constructed. The working pipe is made of high-temperature and high-pressure resistant seamless steel pipe. The insulation system consists of the working pipe, a stepped phase change insulation layer, an auxiliary insulation layer, and an outer protective layer from the inside out. Each layer is sealed with a high-temperature resistant sealant to ensure no gaps or leaks and to guarantee the insulation airtightness. At the same time, the installation position of the electrical monitoring node is reserved to ensure that the subsequent electrical components are not affected by the external environment.

[0029] S2. Screening and Preparation of Composite Phase Change Thermal Insulation Materials Based on the pipeline operating temperature (130-140℃), molten salt composite phase change materials with a phase change temperature range of 135-145℃ were selected. The base material was a mixed molten salt of sodium nitrate and potassium nitrate, with 5% graphene added as a thermal conductivity enhancer, 3% silicone resin as a leak-proof agent, and 2% hydroxystearic acid as a stability modifier. Preparation process: The mixed molten salt was placed in a melting furnace and heated to 160℃ to melt. After stirring evenly, graphene, silicone resin, and hydroxystearic acid were added sequentially, and stirring continued for 45 minutes. The mixture was then poured into a mold suitable for the working pipe, cooled, and solidified to obtain the phase change insulation unit substrate. Its properties are: latent heat of phase change 120kJ / kg, thermal conductivity 0.8W / (m·K), and good compatibility with polyurethane materials (compliant with the limitations of dependent claim 8).

[0030] S3, Construction of stepped phase change insulation layer The phase change insulation unit substrate is processed into an insulation unit suitable for a DN1600mm working pipe. It is then attached to the outer wall of the working pipe using a tongue-and-groove splicing method, with the joints sealed using high-temperature resistant sealant. The pipe is divided into three insulation sections along its axial direction. The phase change temperature of each section is calculated using a dynamic temperature decay matching formula: the initial temperature of the medium at the pipe inlet... T in =140℃, calculations show that the initial insulation section (0-30km) experiences a natural temperature drop without phase change. No prior thermal storage temperature drop compensation ( i When =1, The target temperature of the medium at the starting end is then... The corresponding phase change material has a phase change temperature of 135-145℃; the natural temperature drop occurs in the middle section (30-70km). Early stage thermal storage temperature drop compensation ,but The corresponding phase change temperature of the phase change material is 125-135℃; the natural temperature drop at the end (70-100km) Early stage thermal storage temperature drop compensation ,but The phase change temperature of the corresponding phase change material is 115-125℃; the insulation unit is sealed, and the phase change material is 96% filled to ensure no leakage and provide a guarantee for the accuracy of electrical monitoring.

[0031] S4, Auxiliary Insulation and External Protection Structure The auxiliary insulation layer adopts a combination structure of "vacuum insulation layer and aerogel filling layer". The thickness of the vacuum insulation layer is 20mm and the thickness of the aerogel filling layer is 50mm. The overall thermal conductivity is 0.025W / (m·K). The outer protective layer is made of anti-corrosion and anti-aging materials and is 15mm thick through sealed splicing treatment. It plays a role in anti-corrosion, waterproof and anti-aging, and is suitable for outdoor laying environment. At the same time, it protects the internal electrical monitoring nodes and wiring.

[0032] S5, Electrical Intelligent Control System Operation An electrical monitoring node is installed every 1.5 km along the pipeline. Each node integrates a temperature sensor with an accuracy of ±0.1℃, a pressure sensor with an accuracy of ±0.01MPa, a LoRa wireless transmission module, and a data acquisition unit. It collects real-time data on the temperature and pressure of the medium inside the pipeline, as well as the temperatures of the inner and outer sides of the insulation layer. The data acquisition unit converts the analog signals into digital electrical signals, which are then transmitted to the intelligent control terminal via the LoRa wireless transmission module (transmission delay ≤300ms). The intelligent control terminal incorporates a PID control algorithm, a data processing unit, and a signal output unit. The preset medium temperature threshold is 130±2℃, and the initial PID gain coefficient is... The data processing unit performs noise reduction on the received electrical signal and calibrates the gain coefficient in real time using a PID control gain coefficient calibration model: when the medium temperature deviation... Deviation change rate The calibrated gain coefficient was obtained by fitting the nonlinear calibration functions f, g, and h (fitting data were obtained from field measurements). The PID algorithm adaptively adjusts the electrical control signals for pipeline flow rate and pressure based on calibrated coefficients. When the medium temperature is above 132℃, a deceleration control signal is output to slow the flow rate and utilize the phase change material for heat storage. When the medium temperature is below 128℃, the phase change material releases heat to maintain temperature stability, while simultaneously outputting a supplementary heating control signal to reduce the frequency of intermediate heating. The intelligent control terminal enables remote monitoring and promptly outputs alarm signals when abnormal data is detected.

[0033] S6, Full Lifecycle Operation and Maintenance Management Every 6 months, the pipeline insulation layer undergoes a sealing test (vacuum pressure test) and a performance test (heat flow meter test) to measure the heat loss per unit length of the pipeline. Every 1.5 years, the composite phase change material undergoes a performance re-inspection, testing its latent heat of phase change, thermal conductivity, and other key performance indicators. Insulation units with performance degradation exceeding 10% are replaced. Every 6 months, the sensor accuracy of the electrical monitoring nodes is calibrated, and the signal stability of the wireless transmission module and the algorithm operation status of the intelligent control terminal are checked. A pipeline operation database is established to record operating parameters, electrical control data (including the gain coefficient after PID calibration), and maintenance records, and to optimize control parameters.

[0034] In this embodiment, the heat loss per unit length of the pipeline is reduced to below 120W / m, a 45% reduction compared to traditional insulation methods. The temperature fluctuation of the medium inside the pipeline is controlled within ±1.5℃, and the number of intermediate heating stations is reduced from 6 to 2, resulting in a reduction of 300,000 tons of standard coal consumption and 820,000 tons of carbon dioxide emissions annually, demonstrating significant energy-saving and environmental benefits. The electrical intelligent control system responds quickly and controls precisely. The application of the two core formulas achieves a precise match between cascade insulation and intelligent control, fully demonstrating the innovative advantages of this method. Compared with existing technologies, the overall performance is significantly improved.

[0035] Example 2 This embodiment targets a DN400mm large-diameter heating pipeline used for urban centralized heating. The pipeline operates at a temperature of 80-100℃, with a transmission distance of 20km. It employs the high-efficiency, energy-saving transmission method based on phase change insulation of this invention. The specific steps are as follows: S1. Pipe insulation system adaptation design A multi-layer insulation system adapted to DN400mm large-diameter pipes is pre-constructed. The working pipe is made of high-temperature resistant seamless steel pipe. The insulation system consists of the working pipe, a stepped phase change insulation layer, an auxiliary insulation layer, and an outer protective layer from the inside out. Each layer is sealed with a high-temperature resistant sealant to ensure airtightness. The system also reserves installation positions for electrical monitoring nodes to meet the protection requirements of electrical components in urban underground laying environments.

[0036] S2. Screening and Preparation of Composite Phase Change Thermal Insulation Materials Based on the pipeline operating temperature (80-100℃), a sugar alcohol-based composite phase change material with a phase change temperature range of 85-95℃ was selected. Pentaerythritol was used as the base material, with 3% carbon fiber added as a thermal conductivity enhancer, 2% polymer sealant as a leak-proof agent, and 1% polyethylene glycol as a stability modifier. Preparation process: Pentaerythritol was placed in a melting furnace and heated to 120℃ until melted. After stirring evenly, carbon fiber, polymer sealant, and polyethylene glycol were added sequentially, and stirring continued for 30 minutes. The mixture was then poured into a mold suitable for the working pipe, cooled, and solidified to obtain the phase change insulation unit substrate. Its properties are: latent heat of phase change 105 kJ / kg, thermal conductivity 0.6 W / (m·K), and good compatibility with rock wool materials.

[0037] S3, Construction of stepped phase change insulation layer The phase change insulation unit substrate is processed into an insulation unit suitable for a DN400mm working pipe. It is then attached to the outer wall of the working pipe using a tongue-and-groove splicing method, with the splices sealed using high-temperature resistant sealant. The pipe is divided into two insulation sections along its axial direction. The phase change temperature of each section is calculated using a dynamic temperature decay matching formula: the initial temperature of the medium at the pipe inlet... Natural temperature drop with no phase change at the initial stage (0-10km) ,but The corresponding phase change temperature of the phase change material is 85-95℃; the natural temperature drop at the end (10-20km) Early stage thermal storage temperature drop compensation ,but The phase change temperature of the corresponding phase change material is 75-85℃; the insulation unit is sealed, and the phase change material is 95% filled to ensure no leakage.

[0038] S4, Auxiliary Insulation and External Protection Structure The auxiliary insulation layer adopts a combination structure of "vacuum insulation layer and rock wool filling layer". The thickness of the vacuum insulation layer is 10mm and the thickness of the rock wool filling layer is 30mm. The overall thermal conductivity is 0.03W / (m·K). The outer protective layer is made of anti-corrosion and anti-aging materials and is 10mm thick through sealed splicing treatment. It is suitable for urban underground laying environment and protects the internal electrical monitoring nodes and wiring from underground water vapor erosion.

[0039] S5, Electrical Intelligent Control System Operation An electrical monitoring node is installed every 1 km along the pipeline. Each node integrates a temperature sensor with an accuracy of ±0.1℃, a pressure sensor with an accuracy of ±0.01MPa, a 5G wireless transmission module, and a data acquisition unit. It collects real-time data on the temperature, pressure, and insulation layer temperature of the medium within the pipeline. The data acquisition unit converts the analog signals into digital electrical signals, which are then transmitted to the intelligent control terminal via the 5G wireless transmission module, with a transmission delay of ≤200ms. The intelligent control terminal has a preset medium temperature threshold of 90±2℃ and an initial PID gain coefficient. The gain coefficient is calibrated in real time through a PID control gain coefficient calibration model to ensure control accuracy. It adaptively adjusts the electrical control signals for conveying flow and pressure, maintains temperature stability, and simultaneously enables remote monitoring and fault alarm.

[0040] S6, Full Lifecycle Operation and Maintenance Management Every 6 months, the sealing and performance of the pipeline insulation layer should be tested, and the performance of the composite phase change material should be retested every year. Damaged or aged insulation units and sealing components should be replaced in a timely manner. Every 6 months, the sensor accuracy of the electrical monitoring nodes should be calibrated, and the operating status of the wireless transmission module and intelligent control terminal should be checked. A pipeline operation database should be established to record temperature, pressure, electrical control data (including the gain coefficient after PID calibration) and operation and maintenance records, and the control algorithm parameters should be optimized.

[0041] In this embodiment, the heat loss per unit length of the pipeline is reduced to below 140W / m, which is 30% lower than that of traditional insulation methods. The temperature fluctuation of the medium inside the pipeline is controlled within ±2℃, significantly improving the heating comfort at the user end and saving 800,000 yuan in energy costs annually, demonstrating good economic and social benefits. The application of the electrical intelligent control system greatly reduces the cost of manual operation and maintenance, improves the stability and intelligence level of pipeline operation, highlighting the creativity and practicality of this method, which is superior to the existing urban centralized heating pipeline transportation methods.

[0042] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation, characterized in that, Includes the following steps: S1. Pipeline insulation system adaptation design: A multi-layer insulation system adapted to large-diameter thermal pipelines is pre-constructed. The insulation system consists of the working pipe, a stepped phase change insulation layer, an auxiliary insulation layer, and an outer protective layer from the inside out. Each layer is sealed to ensure insulation airtightness, laying the foundation for subsequent electrical intelligent control and insulation construction. S2. Screening and preparation of composite phase change insulation materials: Based on the working temperature range of large-diameter thermal pipelines, suitable composite phase change materials are screened. The composite phase change materials are mixed, melted, and solidified, and have good chemical compatibility with auxiliary insulation materials. S3. Construction of the stepped phase change insulation layer: The prepared composite phase change material is processed into insulation units and attached to the outer wall of the working pipe to form a stepped phase change insulation layer; the stepped phase change insulation layer is divided into multiple insulation sections along the pipeline axis, and the phase change temperature of the composite phase change material in each insulation section is determined by calculation using a dynamic temperature decay matching formula to adapt to the natural temperature decay law of the medium in the pipeline; the insulation unit is sealed to ensure that there is no leakage of the phase change material. S4. Auxiliary insulation and external protection construction: An auxiliary insulation layer is laid on the outside of the cascade phase change insulation layer, and an external protection layer is constructed on the outside of the auxiliary insulation layer to prevent external moisture and impurities from entering the interior of the insulation layer, ensuring the insulation effect and normal operation of electrical monitoring components. S5. Operation of the Electrical Intelligent Control System: Electrical monitoring nodes are set up along the pipeline to collect real-time data on the temperature, pressure, and insulation layer of the medium inside the pipeline and transmit them to the intelligent control terminal. The intelligent control terminal analyzes and processes the data based on the PID control gain coefficient calibration model, adaptively adjusts the pipeline transport parameters, and combines the heat storage and release characteristics of the phase change material to achieve dynamic control of the pipeline temperature and reduce energy consumption. S6. Full life cycle operation and maintenance management: Regularly perform performance testing and maintenance on pipeline insulation layers, and re-inspect and replace composite phase change materials; regularly maintain the electrical intelligent control system to ensure its normal operation; Establish a pipeline operation database, optimize control parameters, and achieve energy-saving operation and maintenance.

2. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, In step S2, the composite phase change material uses molten salt or sugar alcohol materials as the base material, and adds thermal conductivity enhancer, leak-proof agent and stability modifier; wherein the thermal conductivity enhancer is one or more of graphene, carbon fiber or metal powder, and the amount added is 3%-8% of the base material mass; the leak-proof agent is organosilicon resin or polymer sealant, and the amount added is 2%-5% of the base material mass; the stability modifier is hydroxystearic acid or polyethylene glycol, and the amount added is 1%-3% of the base material mass.

3. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, In step S3, the thickness of the tiered phase change insulation layer is 50-150mm, the thickness of the auxiliary insulation layer is 30-80mm, and the thickness of the outer protective layer is 10-20mm; the insulation units are joined using a tongue-and-groove splicing method, and the joints are sealed with high-temperature resistant sealant to ensure no gaps; the dynamic temperature attenuation matching formula is as follows: ； in: For the first i Each insulation section is located at a distance from the heat source. x The target temperature of the medium at that location, in °C; This represents the initial temperature of the medium at the pipe inlet, in °C. For insulation without phase change, the distance from the heat source x The natural temperature drop at a given location, expressed in °C; For the first k The thermal storage temperature drop compensation value of the phase change material in each insulation section is given in °C. i This is the sequence number of the insulation section. i =1,2,...,n, where n is the total number of insulation sections.

4. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, In step S5, the electrical monitoring nodes are set up every 1-2 km, integrating temperature sensors, pressure sensors, wireless transmission modules, and data acquisition units; the temperature sensor accuracy is ≤ ±0.1℃, the pressure sensor accuracy is ≤ ±0.01MPa, and the wireless transmission module adopts LoRa or 5G communication protocols with a transmission delay ≤ 500ms; the PID control gain coefficient calibration model is as follows: ； in: , , These are the proportional, integral, and derivative gain coefficients after calibration, respectively. , , The initial gain coefficient for the PID algorithm; This represents the deviation between the actual temperature of the medium and the target temperature, expressed in °C. The rate of change of temperature deviation is expressed in °C / min. , , The nonlinear calibration function is based on pipeline operating conditions and is obtained by fitting field measured data.

5. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, In step S6, the performance testing of the insulation layer includes sealing testing and heat loss testing. The sealing testing adopts the vacuum pressure testing method, and the heat loss testing adopts the heat flow meter method. The maintenance of the electrical monitoring node includes sensor accuracy calibration, which adopts the standard signal source comparison method.

6. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, The composite phase change material is reusable, and its service life is extended after performance repair treatment; the auxiliary insulation layer adopts a modular design, which is convenient for disassembly, maintenance and replacement; the electrical intelligent control system can realize remote monitoring and fault alarm.

7. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, The large-diameter thermal pipeline is defined as a thermal transmission pipeline with a nominal diameter DN ≥ 400 mm.

8. The method for efficient and energy-saving transportation of large-diameter thermal pipelines based on phase change insulation according to claim 1, characterized in that, The latent heat of solid-liquid phase change of the composite phase change material described in step S2 is ≥100kJ / kg, and the thermal conductivity is ≤1.0W / (m·K).

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