A long-distance heat supply pipe network supply and demand mutation water-heat coupling dynamic simulation method and system

Abstract

The application discloses a kind of long supply and demand mutation water-heat coupling dynamic simulation method and system of heat supply pipe network, belong to central heating technical field, technical scheme is, obtaining heat supply pipe network topological structure parameter, elevation, pipe structure parameter, insulation layer structure parameter and environmental parameter;Matrix is constructed to node association, sets heat source parameter, physical property parameter, mutation working condition parameter and space step;Initial hydraulic calculation is carried out, and the flow of each pipe section of heat supply pipe network and the pressure distribution of each node are obtained;Temperature field in pipe network is calculated when supply and demand load mutation occurs Time advancing, and heat medium physical property parameter and pipe network hydraulic state are updated synchronously in temperature field calculation process, the coupling dynamic simulation of water and heat is realized;On the basis of coupling dynamic simulation, the heat storage or heat release process of heat supply pipe network under supply and demand load mutation working condition is analyzed.The beneficial effects of the application are: provide a kind of long supply and demand mutation water-heat coupling dynamic simulation method and system of heat supply pipe network.

Description

Technical Field

[0001] This invention relates to the field of centralized heating technology, and in particular to a dynamic simulation method and system for water-thermal coupling of sudden changes in supply and demand in long-distance heating pipeline networks. Background Technology

[0002] With the continuous expansion of urban centralized heating, long-distance heating pipelines are widely used in district heating systems due to their long transmission distances and wide coverage. These types of heating pipelines are typically characterized by large pipe diameters, long pipelines, and high system water capacity, which, while ensuring large-scale heating demand, also makes the system's operating characteristics more complex.

[0003] In actual operation, long-distance heating pipelines are easily affected by factors such as changes in heat source output, power grid dispatching, fluctuations in user-side load, and sudden changes in meteorological conditions, frequently resulting in sudden changes in heat supply and demand. When the load on the supply side or demand side changes abruptly, the pressure, flow rate, and temperature distribution within the pipeline will change. If not properly adjusted, this can easily lead to fluctuations in the terminal heating temperature, instability in the hydraulic system, and even affect heating safety and quality.

[0004] Existing heating network operation analysis and control technologies are mostly based on steady-state calculations, typically assuming constant system conditions, which makes it difficult to reflect the time-varying characteristics of network parameters during sudden changes in supply and demand. While some technologies incorporate dynamic analysis methods, the calculation process is complex and computationally intensive, failing to meet the requirements of computational efficiency and practicality in engineering operations. Furthermore, existing technologies often focus on heat source or user-side regulation, neglecting the inherent heat storage and buffering capabilities of long-distance heating networks, making it difficult to quantitatively analyze the heat storage and release characteristics of the network during load surges.

[0005] Therefore, how to comprehensively analyze the hydraulic characteristics, thermal response, and heat storage capacity of long-distance heating networks under sudden changes in supply and demand while ensuring computational efficiency remains an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic simulation method and system for water-thermal coupling of supply and demand changes in long-distance heating pipeline networks.

[0007] This invention is achieved through the following measures:

[0008] In the first aspect, this embodiment provides a dynamic simulation method for water-thermal coupling of sudden changes in supply and demand in a long-distance heating pipeline network, characterized in that it includes: S1, under the initial stable operating conditions of the heating system, obtaining the topological parameters, elevation, pipeline structure parameters, insulation layer structure parameters and environmental parameters of different laying methods of the long-distance heating pipeline network;

[0009] S2. Construct the node association matrix and set the pipeline network operation parameters, physical property parameters, sudden change condition parameters, and spatial step size;

[0010] S3. Initial hydraulic calculations are performed using the nodal flow method to obtain the flow rate and pressure distribution of each node in the heating network.

[0011] S4. Based on the initial hydraulic calculation results, time-progress calculations are performed on the temperature field in the pipeline network when the supply and demand loads change abruptly. During the temperature field calculation process, the physical properties of the heating medium and the hydraulic state of the pipeline network are updated synchronously to achieve coupled dynamic simulation of hydraulics and heat.

[0012] S5. Based on coupled dynamic simulation, statistical analysis is performed on the heat storage or heat release process of the heating network under the condition of sudden change in supply and demand load, and the corresponding heat storage or heat release and temperature change curves over time are obtained.

[0013] Furthermore, the pipeline structure parameters include pipeline length, pipe diameter, and pipeline thermal conductivity; the insulation structure parameters include the thermal conductivity and thickness of the insulation layer; the environmental parameters for direct burial include soil temperature and burial depth; and the environmental parameters for overhead installation include air temperature and wind speed.

[0014] Furthermore, the construction of the node association matrix includes constructing the node association matrix based on the pipe segment and node numbers and the topology of the pipeline network.

[0015] Specifically, S3 includes: S31, initial setting of pipe section flow rate;

[0016] S32. Calculate the resistance characteristic coefficient of each pipe segment based on the inner diameter and length parameters of each pipe and form a diagonal matrix of resistance characteristic coefficients;

[0017] S33. Based on the node continuity equation and through the pipe segment pressure drop calculation formula, establish a set of equations to solve the node pressure, and iteratively correct the pipe segment flow rate until the calculation accuracy is met;

[0018] S34. Calculate the pressure values ​​of each node in the pipeline network based on the set reference node pressure, and add the pump head and pressure drop to overcome the elevation difference to obtain the flow rate of each pipe section and the pressure distribution of each node.

[0019] Furthermore, the calculation of the resistance characteristic coefficient takes into account at least the equivalent absolute roughness of the pipe wall, the pipe section length, the equivalent length of the local resistance, and the average density of the fluid medium inside the pipe.

[0020] Specifically, S4 includes:

[0021] S41. Initialize the temperature field of the pipeline network nodes; S42. Calculate the thermal resistance of the pipeline based on the inner and outer diameters and length of each pipe segment, calculate the thermal resistance of the insulation layer based on the thermal conductivity and thickness of the insulation layer, calculate the air thermal resistance based on the ambient parameters of air temperature and wind speed for overhead laying, and calculate the soil thermal resistance based on the burial depth and soil temperature for direct burial laying, and then calculate the total thermal resistance of each pipe segment; S43. Calculate the flow velocity of each pipe segment using the pipe segment flow rate from the hydraulic steady-state calculation results, and calculate the maximum allowable time step based on the CFL condition; S44. Establish the pipeline network thermal operating condition model using the method of characteristics, and use the inverse step method to separate the thermal force equation, obtain the temperature at the intersection of the characteristic line and the previous time layer through linear interpolation, obtain the finite difference equation after discretization along the characteristic line, and solve the temperature field layer by layer;

[0022] S45. Update the medium density, specific heat and other physical properties by combining the current node temperature with the initial hydraulic results, and reconstruct the diagonal matrix of the drag characteristic coefficient.

[0023] S46. Based on the nodal continuity equation, a new set of equations is established to iteratively solve the nodal pressure and pipe segment flow rate, so as to achieve synchronous updating of hydraulic and thermal states.

[0024] S47. Repeat S44-S46 until all spatial steps are completed;

[0025] S48. Determine whether the current time layer meets the requirements and whether the pipeline network is stable. Then form a system of equations to approximate the network one by one until the temperature of the pipeline network in the (k+1)th time layer is stable or exceeds the iteration time. Proceed to the next step.

[0026] S49: Take the temperature of the same time layer at different nodes to obtain the temperature distribution of the pipeline network at different times.

[0027] Furthermore, the demand surge condition includes at least one of the following adjustment methods: quality adjustment method: under the condition that the pipeline flow rate remains basically unchanged, the water supply temperature is increased to cope with the load surge, and the water supply temperature is restored after the heat storage is completed; quantity adjustment method: under the condition that the water supply temperature remains basically unchanged, the pipeline operating flow rate is increased to cope with the load surge, and the flow rate is stabilized after the heat storage is completed.

[0028] Secondly, this embodiment provides a dynamic simulation system for water-thermal coupling of supply and demand changes in a long-distance heating network, characterized in that it includes:

[0029] The system comprises the following modules: a data input module for inputting topological parameters, elevations, pipe structure parameters, insulation layer structure parameters, and environmental parameters for different laying methods of the long-distance heating pipeline network; a parameter setting module for constructing a node association matrix and setting network operation parameters, physical property parameters, parameters for sudden load changes, and spatial step size; an initial hydraulic calculation module for performing initial hydraulic calculations using the nodal flow method to obtain the flow rate of each pipe segment and the pressure distribution of each node in the heating pipeline network; a hydraulic-thermal dynamic calculation module for performing time-progressive calculations of the temperature field within the pipeline network when the supply and demand loads change abruptly, based on the initial hydraulic calculation results, and synchronously updating the physical property parameters of the heating medium and the hydraulic state of the pipeline network during the temperature field calculation process to achieve coupled dynamic simulation of hydraulics and heat; and a pipeline network analysis module for statistically analyzing the heat storage or release process of the heating pipeline network under sudden load changes, based on the coupled dynamic simulation, to obtain the corresponding heat storage or release and temperature change curves over time.

[0030] The beneficial effects of the technical solution provided by the embodiments of the present invention are: the present invention combines hydraulic and thermal dynamic analysis, which can reflect the operating characteristics of long-distance heating pipelines under sudden changes in supply and demand while ensuring calculation efficiency.

[0031] This invention achieves quantitative characterization of the heat storage, heat release, and response time of long-distance heating pipelines by synchronously updating the temperature field and operating status of the pipeline network during sudden changes in supply and demand, thus fully demonstrating the buffering capacity of the pipeline network itself.

[0032] This invention is applicable to various operating conditions such as sudden changes in supply-side load and sudden changes in demand-side load. For the demand side, it can combine different operating adjustment methods to analyze the heat storage and release situation of long-distance pipelines, providing a technical basis for the operation and regulation of heating systems. Attached Figure Description

[0033] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings listed below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the long-distance heating pipeline network topology in an embodiment of the present invention;

[0035] Figure 2 A flowchart of a dynamic simulation method for water-thermal coupling in response to sudden changes in supply and demand in a long-distance heating network, as described in an embodiment of the present invention;

[0036] Figure 3 This is a flowchart illustrating a dynamic simulation method for water-thermal coupling in response to sudden changes in supply and demand in a long-distance heating network, as described in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of a finite difference mesh;

[0038] Figure 5 This is a schematic diagram of linear interpolation;

[0039] Figure 6 It is a pressure distribution diagram;

[0040] Figure 7 It is a temperature distribution map;

[0041] Figure 8 This is a graph showing the temperature change over time at the entrance of Station #4 under different sudden operating conditions;

[0042] Figure 9 This is a graph showing the temperature changes over time between the heat source water supply and the return water temperature at Station 4 under quality regulation.

[0043] Figure 10 This is a graph showing the temperature changes over time for the heat source water supply and the return water temperature at Station 4 under quantity regulation. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Example 1:

[0046] See Figure 2 This embodiment provides a dynamic simulation method for water-thermal coupling of sudden supply and demand changes in long-distance heating pipelines, characterized by including: S1, under the initial stable operating conditions of the heating system, obtaining the topological parameters, elevation, pipe structure parameters, insulation layer structure parameters, and environmental parameters of different laying methods of the long-distance heating pipeline network;

[0047] S2. Construct the node association matrix and set the pipeline network operation parameters, physical property parameters, sudden change condition parameters, and spatial step size;

[0048] S3. Initial hydraulic calculations are performed using the nodal flow method to obtain the flow rate and pressure distribution of each node in the heating network.

[0049] S4. Based on the initial hydraulic calculation results, time-progress calculations are performed on the temperature field in the pipeline network when the supply and demand loads change abruptly. During the temperature field calculation process, the physical properties of the heating medium and the hydraulic state of the pipeline network are updated synchronously to achieve coupled dynamic simulation of hydraulics and heat.

[0050] S5. Based on coupled dynamic simulation, statistical analysis is performed on the heat storage or heat release process of the heating network under the condition of sudden change in supply and demand load, and the corresponding heat storage or heat release and temperature change curves over time are obtained.

[0051] The pipeline structure parameters include pipeline length, pipe diameter, and pipeline thermal conductivity; the insulation structure parameters include the thermal conductivity and thickness of the insulation layer; the environmental parameters for direct burial include soil temperature and burial depth; and the environmental parameters for overhead installation include air temperature and wind speed.

[0052] The construction of the node association matrix includes constructing the node association matrix based on the pipe segment and node numbers and the topology of the pipeline network.

[0053] Specifically, S3 includes: S31, initial setting of pipe section flow rate;

[0054] S32. Calculate the resistance characteristic coefficient of each pipe segment based on the inner diameter and length parameters of each pipe and form a diagonal matrix of resistance characteristic coefficients;

[0055] S33. Based on the node continuity equation and through the pipe segment pressure drop calculation formula, establish a set of equations to solve the node pressure, and iteratively correct the pipe segment flow rate until the calculation accuracy is met;

[0056] S34. Calculate the pressure values ​​of each node in the pipeline network based on the set reference node pressure, and add the pump head and pressure drop to overcome the elevation difference to obtain the flow rate of each pipe section and the pressure distribution of each node.

[0057] The calculation of the resistance characteristic coefficient takes into account at least the equivalent absolute roughness of the pipe wall, the length of the pipe section, the equivalent length of the local resistance, and the average density of the fluid medium inside the pipe.

[0058] Specifically, S4 includes:

[0059] S41. Initialize the temperature field of the pipeline network nodes; S42. Calculate the thermal resistance of the pipeline based on the inner and outer diameters and length of each pipe segment, calculate the thermal resistance of the insulation layer based on the thermal conductivity and thickness of the insulation layer, calculate the air thermal resistance based on the ambient parameters of air temperature and wind speed for overhead laying, and calculate the soil thermal resistance based on the burial depth and soil temperature for direct burial laying, and then calculate the total thermal resistance of each pipe segment; S43. Calculate the flow velocity of each pipe segment using the pipe segment flow rate from the hydraulic steady-state calculation results, and calculate the maximum allowable time step based on the CFL condition; S44. Establish the pipeline network thermal operating condition model using the method of characteristics, and use the inverse step method to separate the thermal force equation, obtain the temperature at the intersection of the characteristic line and the previous time layer through linear interpolation, obtain the finite difference equation after discretization along the characteristic line, and solve the temperature field layer by layer;

[0060] S45. Update the medium density, specific heat and other physical properties by combining the current node temperature with the initial hydraulic results, and reconstruct the diagonal matrix of the drag characteristic coefficient.

[0061] S46. Based on the nodal continuity equation, a new set of equations is established to iteratively solve the nodal pressure and pipe segment flow rate, so as to achieve synchronous updating of hydraulic and thermal states.

[0062] S47. Repeat S44-S46 until all spatial steps are completed;

[0063] S48. Determine whether the current time layer meets the requirements and whether the pipeline network is stable. Then form a system of equations to approximate the network one by one until the temperature of the pipeline network in the (k+1)th time layer is stable or exceeds the iteration time. Proceed to the next step.

[0064] S49: Take the temperature of the same time layer at different nodes to obtain the temperature distribution of the pipeline network at different times.

[0065] Demand surge conditions include at least one of the following adjustment methods: quality adjustment: under the condition that the pipeline flow rate remains basically unchanged, increase the water supply temperature to cope with the load surge, and restore the water supply temperature after heat storage is completed; quantity adjustment: under the condition that the water supply temperature remains basically unchanged, increase the pipeline operating flow rate to cope with the load surge, and stabilize the flow rate after heat storage is completed.

[0066] Example 2:

[0067] Figure 1 A schematic diagram of a long-distance heating network is presented. The network includes a heat source power plant, a pipeline network, four relay pumping stations, and a virtual load of the urban network. The heating network includes supply and return water pipelines. The pipeline segments and nodes of the long-distance heating network are numbered. Each pumping station has a pressure gauge at its inlet and outlet and a node. A virtual load is set at the end, which does not extend to the urban network. A hydraulic and thermal dynamic model integrating heat source, long-distance network, and load is established.

[0068] See Figures 2-8 A dynamic simulation method for water-thermal coupling of sudden supply and demand changes in long-distance heating pipeline networks is characterized by including: S1, under the initial stable operating conditions of the heating system, obtaining the topological parameters, elevation, pipe structure parameters, insulation layer structure parameters and environmental parameters of different laying methods of the long-distance heating pipeline network;

[0069] Pipeline topology parameters, including pipe segment connections and node distribution, are shown in [link to relevant documentation]. Figure 1 There are a total of 18 nodes and 17 pipe sections, with upstream supply and downstream return. ① is the heat source outlet, ② is the inlet of station #0, ③ is the outlet of station #0, and so on. The area between ⑨ and ⑩ represents the heat source, and the area between ⑨ and ⑩ represents the virtual urban pipe network load.

[0070] Pipeline structural parameters include pipe length, pipe diameter, and pipe thermal conductivity; insulation structural parameters include the thermal conductivity and thickness of the insulation layer; the entire pipeline network is directly buried, and environmental parameters include soil temperature and burial depth. See Table 1 for details.

[0071] Table 1 Pipeline Parameters

[0072]

[0073] The pipe is made of L360 steel with a thermal conductivity of 40 W / (m). K); The thermal conductivity of the insulation material at the operating temperature is taken as 0.033 W / (m²). K) calculation; pipeline burial depth 1.5m, natural ground temperature 8℃.

[0074] S2. Construct the node association matrix and set the pipeline network operation parameters, physical property parameters, sudden change condition parameters, and spatial step size;

[0075] The construction of the node association matrix includes constructing the node association matrix based on the pipe segment and node numbers and the topology of the pipeline network.

[0076] The pipeline operation parameters include parameters such as heat source temperature, pressure, and pump station pressure; the physical property parameters include hot water density and specific heat; the sudden change condition parameters include the sudden change condition type, sudden change load magnitude, and duration.

[0077] The spatial step size is used to discretize the nodes of each pipe segment in the pipeline network.

[0078] Based on the previous operating data of the pipeline network, with a heating load of 800MW, supply and return water temperatures of 100℃ / 45℃, heat source pressure of 1.8MPa, and pipeline flow rate of 13000 m³ / h as the baseline operating conditions, the following settings are adopted: supply water pressure of 1.8MPa, supply water temperature of 100℃, and pipeline flow rate of 13000 m³ / h. The pressure of each pump station is set according to the operating conditions; the hot water density is 944 kg / m³. 3 Specific heat is .

[0079] For the pipeline along the axial direction, an equal-distance dispersion method was adopted, and spatial step sizes of 200m, 150m, 100m, and 50m were selected respectively to examine the differences between the model and the simulation results under different spatial step sizes, as shown in Table 2. Finally, 100m was selected as the model spatial step size.

[0080] Table 2. Models with different spatial step sizes

[0081]

[0082] S3. Initial hydraulic calculations are performed using the nodal flow method to obtain the flow rate and pressure distribution of each node in the heating network.

[0083] S3 includes: S31, firstly setting the flow vector of each pipe segment. ;

[0084] S32. Calculate the resistance characteristic coefficient of each pipe segment based on the inner diameter and length parameters of each pipe and form a diagonal matrix of resistance characteristic coefficients;

[0085]

[0086]

[0087] In the formula, This is a diagonal matrix of drag characteristic coefficients. The resistance characteristic coefficient of each pipe section , Let m be the equivalent absolute roughness of the pipe wall. For heating pipes, generally... =0.0005m; The inner diameter of the pipe is in meters (m). , These are the length of the calculated pipe segment and the equivalent length of local resistance in the pipeline network, respectively, in meters; The average density of the fluid medium inside the pipe. m represents the number of pipe sections.

[0088] S33. Based on the node continuity equation and through the pipe segment pressure drop calculation formula, establish a set of equations to solve the node pressure, and iteratively correct the pipe segment flow rate until the calculation accuracy is met;

[0089] The system of equations is as follows:

[0090]

[0091]

[0092]

[0093] By combining the above three equations, we can obtain the system of equations for solving the nodal pressures:

[0094]

[0095] In the formula, For the pipeline network Order node correlation matrix; For elements The node diagonal matrix formed ; Pipeline flow vector ; Nodal pressure vector ; Node flow vector ; Pipeline pressure drop vector ; This is the resistance characteristic coefficient matrix of the pipe section (an m-order diagonal matrix). .

[0096] Solve the system of equations to find the nodal pressure vector P, based on the pressure drop across the pipe section. Calculate the flow vector of the pipe section ; Determine the maximum error in pipe section flow rate If the requirements are met, then correct them. =( + ) / 2 ( For the k-th iteration correction of pipe segment i Then, a system of equations is formed to approximate the problem step by step until the (k+1)th iteration satisfies the required accuracy or the number of iterations (k+1) > 1000, at which point the next step is initiated.

[0097] S34. Based on the set heat source pressure, calculate the pressure values ​​of each node in the pipeline network, and then add the pump head and the pressure drop to overcome the elevation difference to obtain the flow rate of each pipe section and the pressure distribution of each node, and further output the results. Pressure and flow vectors.

[0098] S4. Based on the initial hydraulic calculation results, time-progress calculations are performed on the temperature field within the pipe network. During the temperature field calculation process, the physical properties of the heating medium and the hydraulic state of the pipe network are updated synchronously to achieve coupled dynamic simulation of hydraulics and heat. Specifically, this includes:

[0099] S41. Initialize the temperature field of the pipeline network nodes; S42. Calculate the thermal resistance of the pipeline based on the inner and outer diameters and length of each pipe segment, calculate the thermal resistance of the insulation layer based on the material and thickness of the insulation layer, calculate the air thermal resistance based on the ambient parameters of air temperature and wind speed for overhead laying, and calculate the soil thermal resistance based on the ambient parameters of burial depth and soil type for direct burial, and then calculate the total thermal resistance of each pipe segment; S43. Calculate the flow velocity of each pipe segment using the pipe segment flow rate from the hydraulic steady-state calculation results, and calculate the maximum allowable time step based on the CFL condition;

[0100]

[0101] In the formula, For time step, ; Spatial step size, ; For the flow rate of the pipe section, ; For cross-sectional area, m represents the number of pipe sections.

[0102] S44. Use the method of characteristics to establish a thermal working model of the pipeline network, and use the inverse step method to separate the heat dissipation force equation. Obtain the temperature at the intersection of the characteristic line and the previous time layer through linear interpolation, obtain the finite difference equation after discretization along the characteristic line, and solve the temperature field layer by layer.

[0103] The characteristic line method differs from the conventional finite difference method in that it does not pre-define the mesh within the solution domain. Instead, it gradually forms the mesh using approximate characteristic lines over time. The characteristic line method for solving one-dimensional unsteady flow problems can be used to construct various finite difference meshes and global step algorithms, such as... Figure 4 As shown.

[0104] Starting from the fluid energy conservation equation, neglecting the influence of axial heat conduction on the temperature field distribution, and assuming that heat transfer mainly occurs radially, with the insulation layer structure and its thermal resistance parameters remaining constant during the calculation, a hyperbolic governing equation for the pipe's thermal operation can be obtained. Its simplified form along the characteristic line is the characteristic line trajectory equation:

[0105]

[0106] In the formula, This represents the increase in heat per unit surface area of ​​a controlled volumetric fluid per unit time (positive for exothermic reactions, negative for endothermic reactions). ; For fluid density, ; For specific heat of fluid, ; The inner diameter of the pipe. .

[0107] like Figure 5 As shown, when using the inverse step method to obtain the heat dissipation force equation, linear interpolation is needed to obtain the intersection temperature of the characteristic line and the previous time layer. The positions of the solution points of the previous time layer (such as points 3, 4, and 5) are predetermined, usually equidistant points within the same time layer. The trajectory intersecting at point 6 is extended forward to intersect the line corresponding to the previous time layer to determine the position of the initial data point. The calculation of the flow parameters at the initial data points (such as points 1 and 2) requires interpolation using the previous solution points (such as points 3, 4, and 5). The intersection temperature of the characteristic line and the previous time layer is obtained through linear interpolation. The linear interpolation formula is:

[0108]

[0109] In the formula, Temperatures at points 1, 3, and 4, in Kelvin; The coordinates of points 1, 3, and 4 are shown in meters. The velocity inside the pipe is m / s.

[0110] Solving the equations of the characteristic lines using a forward explicit difference scheme with first-order Taylor series expansion points, and then discretizing along the characteristic lines, yields the finite difference equations:

[0111]

[0112] Therefore, we can conclude that:

[0113]

[0114] In the formula, i is the pipe segment number; j is the node number; and k is the time layer.

[0115] S45. Update the medium density, specific heat, and other physical properties using the current node temperature combined with the initial hydraulic results, and reconstruct the diagonal matrix of the drag characteristic coefficients. Pressure waves in the pipe propagate at the speed of sound, while temperature changes propagate at a speed close to the flow velocity within the pipe. The propagation speed of pressure waves is much greater than the rate of temperature change. Therefore, after calculating the temperature of each node, update the hydraulic conditions of the entire pipe network. Similar to step S3, set the flow vector from the initial hydraulic calculation as the initial flow vector. By combining the current node temperature with updated medium density, specific heat and other physical properties, the diagonal matrix of drag characteristic coefficients is reconstructed.

[0116] S46. Based on the nodal continuity equations, a new set of equations is established and iteratively solved to obtain the nodal pressure and pipe segment flow rate, achieving simultaneous updates of hydraulic and thermal states. A new set of equations is established and iterated to solve for the new nodal pressure vector. The new flow vector is calculated based on the pressure drop of the pipe section. This enables synchronous updates of hydraulic and thermal states, with each node updating... As the initial flow vector for the next hydraulic condition. ;

[0117] S47. Repeat S44-S46 until all spatial steps are completed;

[0118] S48. Determine whether the current time layer meets the requirements and whether the pipeline network is stable. Then form a system of equations to approximate the network one by one until the temperature of the pipeline network in the (k+1)th time layer is stable or exceeds the iteration time. Proceed to the next step.

[0119] S49: Take the temperature of the same time layer at different nodes to obtain the temperature distribution of the pipeline network at different times.

[0120] Among them, such as Figure 6 , Figure 7 As shown, under stable operating conditions, the hydraulic model is basically consistent with the actual data, with pipe section pressure drop error ≤2.5% and node pressure error ≤5%. The thermal model is basically consistent with the actual data, with pipe section temperature drop and node temperature error both ≤2.5%.

[0121] S5. Based on the coupled dynamic simulation, set the sudden change of supply and demand load, and perform statistical analysis on the heat storage or heat release process of the heating network to obtain the corresponding heat storage or heat release and temperature change curves over time.

[0122] Example 3:

[0123] Based on Example 2, for the setting of the supply-side load change condition, under the condition of stable system operation, the output of the supply-side heat source is set to change suddenly at a certain moment, and the change amplitude is set to 25%, 35% and 50% of the rated heating load, respectively, and the change duration is set to 6 hours.

[0124] After a sudden change occurs, the user-side load remains unchanged, and only the output conditions of the supply-side heat source are changed to simulate the sudden change in supply-side load caused by heat source scheduling, power system constraints, and other reasons in actual operation.

[0125] Then when setting When the supply-side load changes abruptly, the heat source temperature decreases, the initial operating conditions stabilize, and the node temperature... At that time, output the temperature response time of each node. .

[0126]

[0127] In the formula, For response time, ; The number of layers for response time; Time step.

[0128] Statistical analysis was then performed on the changes in heat release within the pipeline network during sudden changes in supply-side load.

[0129]

[0130] In the formula, L is the length of the pipe; The temperature of the pipeline network when heat release is complete; This refers to the initial temperature of the pipeline network. The velocity inside the pipe is denoted as .

[0131] like Figure 8 It can be seen that under the three operating conditions of sudden load changes on the supply side, the response time of the inlet temperature of relay energy station #4 is relatively small, and the magnitude of the sudden change has little impact on the starting time of the temperature change at the terminal. Meanwhile, due to its long pipeline length and large water capacity, the long-distance pipeline network has a significant heat storage effect; the hot water stored in the network can continuously release heat after a sudden load change, thus buffering the impact of changes in heat source output on the terminal. Specific data on the temperature response time of relay energy station #4 and the heat release of the pipeline network are shown in Table 3.

[0132] Table 3 Temperature response time and heat release of pipeline network at Station #4 under different load changes.

[0133]

[0134] Example 4:

[0135] Based on Example 2, for the setting of demand-side load change conditions, under the condition of stable system operation, a load change of 100MW is set to simulate the demand-side load change conditions caused by low temperature weather or concentrated start-up and shutdown by users.

[0136] To further analyze the impact of different operating adjustment methods on system stability under demand-side load surge conditions, one of the adjustment methods is used for regulation:

[0137] 1. Quality adjustment method

[0138] Under quality regulation conditions, the pipeline operating flow rate is kept basically constant, and the temperature response time is adjusted in advance. To cope with sudden changes in demand-side load, the water supply temperature on the heat source side should be increased continuously. The temperature is restored and heat storage is completed in a timely manner, such as Figure 9 As shown, based on the pipeline delay, 9 hours in advance The heat source temperature is continuously increased to 107℃, and heat is stored using the pipe network. The temperature is adjusted according to the time of abrupt changes. The temperature recovery and heat storage are completed, with a heat storage capacity of 3240 GJ. When the load suddenly changes, the return water temperature of the No. 4 relay energy station returns to normal level in a timely manner. The system can return to normal in a timely manner after sudden changes in temperature. The pipeline network is designed to operate at 125°C. Under current conditions, it can handle sudden changes in load of 361MW, with a heat storage capacity of 11696.4GJ. The quality regulation method has a certain margin of adjustment.

[0139] Based on coupled dynamic simulation, a statistical analysis was conducted on the changes in heat storage inside the pipeline network under the quality regulation mode during the sudden change of demand-side load.

[0140]

[0141] In the formula, This refers to the pipeline temperature when heat storage is complete. This refers to the initial temperature of the pipeline network. The velocity inside the pipe is denoted as .

[0142] 2. Quantity adjustment method

[0143] Under flow regulation conditions, the water supply temperature is kept constant, and the temperature response time is adjusted accordingly. To cope with sudden changes in demand-side load, the method of constantly increasing the operating flow rate of the pipeline network is to address these issues. The flow rate remains stable and heat storage is complete.

[0144] Through the pipeline heat storage analysis unit, statistical analysis is performed on the changes in heat storage within the pipeline network under the quantity adjustment mode during sudden changes in demand-side load, such as... Figure 10 As shown, under the flow regulation condition, the pressure wave propagates at a speed of 1300 m / s in hot water, which can transfer additional heat to the user side in about one minute. When there is a sudden change in load, increase the pipeline circulation flow rate to 14600 m³ / h. 3 / h, in When the sudden change ends, the pipeline flow rate is restored, and the pipeline heat storage is 3240 GJ. The system temperature response speed is significantly faster than that of the quality regulation method. However, the rapid increase in flow rate will lead to a significant increase in pipeline pressure drop, raising it by 1.15 MPa, which will adversely affect the operating conditions of the pumps and the hydraulic stability of the system. The pipeline design flow rate is 15800 m³ / h. 3 / h, under current operating conditions, it can only cope with a maximum load change of 172MW, with a heat storage limit of 4458.24GJ, leaving limited room for adjustment.

[0145]

[0146] In the formula, This is the flow rate when heat storage is complete; This represents the initial flow rate of the pipeline network.

[0147] Comprehensive analysis shows that the quality regulation method has a large heat storage capacity, a certain regulation margin, stable operation, and little disturbance to the hydraulic system, but the response speed is relatively slow; the quantity regulation method responds quickly, but is greatly limited by the pipeline network's transmission capacity and hydraulic constraints, and has limited regulation room.

[0148] Example 5:

[0149] Based on Embodiment 1 or Embodiment 2, this embodiment provides a dynamic simulation system for water-thermal coupling of supply and demand changes in a long-distance heating network, characterized in that it includes:

[0150] The data input module is used to input the pipeline topology parameters, elevation, pipe structure parameters, insulation layer structure parameters, and environmental parameters for different laying methods under the initial stable operating conditions of the heating system. The parameter setting module is used to construct the node association matrix and set the heat source parameters, physical property parameters, sudden change condition parameters, and spatial step size. The initial hydraulic calculation module is used to perform initial hydraulic calculations using the nodal flow method to obtain the flow rate of each pipe segment and the pressure distribution of each node in the heating network. The hydraulic-thermal dynamic calculation module is used to perform time-progressive calculations of the temperature field within the network when the supply and demand loads change abruptly, based on the initial hydraulic calculation results, and to synchronously update the physical property parameters of the heating medium and the hydraulic state of the network during the temperature field calculation process, so as to achieve coupled dynamic simulation of hydraulics and heat. The network analysis module is used to perform statistical analysis of the heat storage or release process of the heating network under sudden change conditions of supply and demand loads, based on the coupled dynamic simulation, to obtain the corresponding heat storage or release and temperature change curves over time. The specific functions of each module are described in the relevant descriptions of the above method embodiments, and will not be repeated here.

[0151] Example 6:

[0152] This embodiment provides an electronic device, characterized in that it includes: a processor and a memory, wherein the processor is used to execute a program stored in the memory for a dynamic simulation method of water-thermal coupling for sudden changes in supply and demand in long-distance heating pipelines, so as to realize the dynamic simulation method of water-thermal coupling for sudden changes in supply and demand in long-distance heating pipelines.

[0153] An electronic device includes at least one processor, memory, at least one network interface, and other user interfaces. The various components of the electronic device are coupled together via a bus system. It is understood that the bus system is used to enable communication between these components. In addition to a data bus, the bus system also includes a power bus, a control bus, and a status signal bus.

[0154] The user interface may include a display, keyboard, or clicking device (e.g., mouse, trackball, touchpad, or touchscreen). It is understood that the memory in this embodiment may be volatile memory or non-volatile memory, or may include both.

[0155] In this embodiment of the invention, the processor executes the method steps provided in each method embodiment by calling a program or instruction stored in the memory, specifically a program or instruction stored in an application program.

[0156] In some implementations, the memory stores elements such as executable units or data structures, or subsets thereof, or extended sets thereof: operating systems and applications.

[0157] The operating system includes various system programs, such as the framework layer, core library layer, and driver layer, used to implement various basic business functions and handle hardware-based tasks. The application programs include various applications, such as media players and browsers, used to implement various application functions. The program implementing the method of this invention can be included in the application programs.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dynamic simulation method for water-thermal coupling of supply and demand changes in long-distance heating pipeline networks, characterized in that, include: S1. Under the initial stable operating conditions of the heating system, obtain the topological parameters, elevation, pipe structure parameters, insulation layer structure parameters, and environmental parameters of different laying methods of the long-distance heating pipeline network. S2. Construct the node association matrix and set the pipeline network operation parameters, physical property parameters, sudden change condition parameters, and spatial step size; S3. Initial hydraulic calculations are performed using the nodal flow method to obtain the flow rate and pressure distribution of each node in the heating network. S4. Based on the initial hydraulic calculation results, time-progress calculations are performed on the temperature field in the pipeline network when the supply and demand loads change abruptly. During the temperature field calculation process, the physical properties of the heating medium and the hydraulic state of the pipeline network are updated synchronously to achieve coupled dynamic simulation of hydraulics and heat. S5. Based on coupled dynamic simulation, statistical analysis is performed on the heat storage or heat release process of the heating network under the condition of sudden change in supply and demand load, and the corresponding heat storage or heat release and temperature change curves over time are obtained. The pipeline structural parameters include pipeline length, pipe diameter, and pipeline thermal conductivity; the insulation layer structural parameters include the thermal conductivity and thickness of the insulation layer; the environmental parameters for direct burial include soil temperature and burial depth; the environmental parameters for overhead installation include air temperature and wind speed. The construction of the node association matrix includes constructing the node association matrix based on the pipe segment and node numbers and the topology of the pipe network; S3 includes: initial setting of the pipe section flow rate; Calculate the resistance characteristic coefficient of each pipe segment based on the inner diameter and length parameters of each pipe, and form a diagonal matrix of resistance characteristic coefficients; Based on the node continuity equation and the pipe segment pressure drop calculation formula, a set of equations for solving the node pressure is established, and the pipe segment flow rate is iteratively corrected until the calculation accuracy is met; The pressure values ​​of each node in the pipeline network are calculated based on the set reference node pressure, and the pump head and pressure drop to overcome the elevation difference are added to obtain the flow rate of each pipe section and the pressure distribution of each node. The calculation of the resistance characteristic coefficient takes into account at least the equivalent absolute roughness of the pipe wall, the length of the pipe section, the equivalent length of the local resistance, and the average density of the fluid medium inside the pipe. S4 includes: S41. Initialize the temperature field of the pipeline network nodes; S42. Calculate the thermal resistance of the pipeline based on the inner and outer diameters and length of each pipe segment, calculate the thermal resistance of the insulation layer based on the thermal conductivity and thickness of the insulation layer, calculate the air thermal resistance based on the ambient parameters of air temperature and wind speed for overhead laying, and calculate the soil thermal resistance based on the burial depth and soil temperature for direct burial laying, and then calculate the total thermal resistance of each pipe segment; S43. Calculate the flow velocity of each pipe segment using the pipe segment flow rate from the hydraulic steady-state calculation results, and calculate the maximum allowable time step based on the CFL condition; S44. Establish the pipeline network thermal operating condition model using the method of characteristics, and use the inverse step method to separate the thermal force equation, obtain the temperature at the intersection of the characteristic line and the previous time layer through linear interpolation, obtain the finite difference equation after discretization along the characteristic line, and solve the temperature field layer by layer; S45. Update the medium density and specific heat using the current node temperature and the initial hydraulic results, and reconstruct the diagonal matrix of the drag characteristic coefficients. S46. Based on the nodal continuity equation, a new set of equations is established to iteratively solve the nodal pressure and pipe segment flow rate, so as to achieve synchronous updating of hydraulic and thermal states. S47. Repeat S44-S46 until all spatial steps are completed; S48. Determine whether the current time layer meets the requirements and whether the pipeline network is stable. Then form a system of equations to approximate the network one by one until the temperature of the pipeline network in the (k+1)th time layer is stable or exceeds the iteration time. Proceed to the next step. S49: Take the temperature of the same time layer at different nodes to obtain the temperature distribution of the pipeline network at different times; Demand surge conditions include at least one of the following adjustment methods: quality adjustment: under the condition of constant pipeline flow, increase the water supply temperature to cope with load surges, and restore the water supply temperature after heat storage is completed; quantity adjustment: under the condition of constant water supply temperature, increase the pipeline operating flow to cope with load surges, and stabilize the flow after heat storage is completed.

2. A dynamic simulation system for water-thermal coupling of supply and demand changes in a long-distance heating pipeline network, implementing the dynamic simulation method of claim 1, characterized in that, include: The data input module is used to input the pipeline topology parameters, elevation, pipe structure parameters, insulation layer structure parameters, and environmental parameters for different laying methods under the initial stable operating conditions of the heating system; the parameter setting module is used to construct the node association matrix and set the pipeline operating parameters, physical property parameters, sudden change condition parameters, and spatial step size; the initial hydraulic calculation module is used to perform initial hydraulic calculations using the nodal flow method to obtain the flow rate of each pipe section and the pressure distribution of each node in the heating pipeline network; The hydraulic-thermal dynamic calculation module is used to perform time-progression calculations on the temperature field in the pipeline network when the supply and demand loads change abruptly, based on the initial hydraulic calculation results. During the temperature field calculation process, the physical property parameters of the heating medium and the hydraulic state of the pipeline network are updated simultaneously to achieve coupled dynamic simulation of hydraulics and heat. The pipeline analysis module is used to perform statistical analysis on the heat storage or heat release process of the heating pipeline under the condition of sudden change in supply and demand load, based on coupled dynamic simulation, and to obtain the corresponding heat storage or heat release and temperature change curve over time.

3. An electronic device, characterized in that, include: A processor and a memory, the processor being configured to execute a program stored in the memory for a dynamic simulation method of water-thermal coupling in response to sudden changes in supply and demand in long-distance heating networks, in order to implement the dynamic simulation method of claim 1.

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