A method for initializing a thermal system simulation model

Abstract

The present invention belongs to the field of thermal simulation technology, and specifically relates to a method for initializing a thermal system simulation model. It includes: obtaining the structure and characteristic parameters of pipelines and equipment in a specified fluid network and the operating parameters of a power plant; S2 initializing the flow calculation, simplifying and restoring the specified fluid network according to the preset series-parallel rule, so as to obtain the final flow used for initialization of each measuring point and pipeline in the specified fluid network; S3 calculating other parameters; S4 importing the final pressure, final temperature, final flow, and final conductance as the initialization conditions of the simulation program. Its advantages are: automatically calculating the initial conditions of the simulation system, reducing the tedious process of manual trial calculation; process-based automatic calculation, standardizing the flow network initialization work; making full use of the pipe network structure parameters, so that the initialization result is closer to the real data; the initialization point data is strictly consistent with the power plant data.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal simulation, and in particular relates to an initialization method for a thermal system simulation model. Background Art

[0002] The systems in large-scale industrial projects are complex, such as power plants, chemical industry, aerospace, etc. Various interdisciplinary problems are often encountered in design, construction, and operation. If experimental methods are used, the cost is too high and the efficiency is low. Simulation modeling provides valuable solutions across industries and disciplines, which can solve practical problems efficiently and economically.

[0003] Graphical modeling is a typical modular modeling method. We abstract the thermal system, use network modules to describe the overall energy, momentum and mass conservation of the thermal system, use equipment modules to describe equipment characteristics, and connect network modules and equipment modules to form a simulation program for the thermal hydraulic system. Abstracting each simulation subunit into an image module allows users to model intuitively, vividly and efficiently. It is a mainstream simulation modeling method in the world. There are many mature graphical modeling software developed at home and abroad, such as GSE, MATLAB, RINSIM, etc. Graphical modeling has changed the modeling method and reduced the ability requirements for modelers.

[0004] For thermal systems, although the units are generally only set with limited flow, pressure and temperature measurement points, the state of the entire network is unique due to the constraints of energy, momentum and mass conservation within the thermal system. In traditional simulation system debugging, technicians complete the data expansion from limited measurement points to the entire network based on their own experience. This process is complex and non-standardized. Different technicians often have different performances in running simulation systems based on the same input. At the same time, the quality of the model is closely related to the level of the modeler. Therefore, in the same project, the process models debugged by different personnel have uneven quality, which will bring great difficulties to the later model debugging and maintenance work. Summary of the invention

[0005] The purpose of the present invention is to provide an initialization method for a thermal system simulation model, analyze the topological structure of a fluid network, and infer the pressure, flow rate and temperature of all boundaries, nodes and pipelines based on the limited measurement points of the unit; the method directly extracts information from structural parameters and power plant operation data, automatically completes the debugging of a graphical simulation model, and transforms the simulation model debugging work from manual debugging that relies on personnel experience to an automatic standardized process, which can effectively achieve the unification of debugging standards and reduce the difficulty of subsequent debugging and maintenance work.

[0006] The technical solution of the present invention is as follows: A method for initializing a thermal system simulation model comprises the following steps:

[0007] S1 obtains the structural and characteristic parameters of the pipelines and equipment in the specified fluid network and the operating parameters of the power plant, and maps the above parameters to the corresponding boundaries, nodes, pipelines, and equipment, where the operating parameters of the power plant include the actual pressure, temperature, and actual flow rate of the nodes and pipelines; the structural and characteristic parameters of the pipelines and equipment in the system include the heat exchange area of ​​the heat exchanger, the head curve parameters of the pump, the length L of the corresponding pipeline, the equivalent diameter d, the cross-sectional area S, and the resistance coefficient λ along the way, the temperature and pressure of the inflow boundary, and the pressure of the outflow boundary;

[0008] S2 initializes flow calculation, based on the flow sensor measurement value obtained in step S1, simplifies and restores the specified fluid network according to the preset series-parallel rule to obtain the final flow of each measuring point and pipeline in the specified fluid network for initialization;

[0009] S3 calculates other parameters, and performs initialization calculations on each node and each pipeline based on the heat exchange area of ​​the heat exchanger, the pump head curve, the pressure and temperature sensor measurements obtained in step S1, and the final flow obtained in step S2, to determine the final pressure and temperature of the node, the final temperature of the outflow boundary, the final flow conductance of the pipeline, and the final heat transfer coefficient of the heat exchange equipment;

[0010] S4 imports the final pressure, final temperature, final flow rate, and final conductance as initialization conditions for the simulation program to run.

[0011] The step S2 comprises:

[0012] S21 estimates the conductance of each node in the designated fluid network according to the pipeline structure parameters as an estimation basis for the initialization flow;

[0013] S22 obtains a designated fluid network graphical file, performs n folding operations on the fluid network in the graphical file according to preset serial connection rules and parallel connection rules, each folding operation includes a set of serial folding and a set of parallel folding to simplify the fluid network to the simplest state, records the folding path, and calculates the conductance and flow rate of each pipeline in the new pipe network formed after each folding according to the conductance of each pipeline and the flow rate of the measuring point obtained in step S21;

[0014] S23 traverses the nodes in the simplest pipe network to calculate the inflow and outflow balance until the flow of all pipes is calculated;

[0015] S24 reversely restores the fluid network according to the folded path, and calculates the flow rate and conductance of each pipeline in the new pipeline network formed by each restoration; until the fluid network is restored to its original state, and all pipeline flows are obtained as final flows.

[0016] In step S21, the conductance of each pipeline is estimated according to the following formula:

[0017]

[0018] Among them, adf is the flow conductance of the pipe, ρ is the liquid density, L is the length of the pipe, d is the equivalent diameter, S is the cross-sectional area, and λ is the resistance coefficient along the way.

[0019] In step S22, each group of series conversion includes:

[0020] (A) traversing all nodes in the pipeline network to be folded, and obtaining the first group of pipelines in series relationship in the pipeline network to be folded;

[0021] (B) The two pipelines that are judged to be in a series relationship are converted into a new pipeline.

[0022] (C) Repeat steps AB until no more pipes in series are found.

[0023] In step (A), the determination of the series relationship includes the following steps: obtaining the node corresponding to the minimum number of this time; traversing and querying from the minimum node, obtaining the number i of all pipeline roots starting from the node, and recording the pipeline number if i=1; obtaining the number j of all pipeline roots ending at the node, and recording the pipeline number if j=1; if i=1 and j=1, the two pipelines are considered to be in a series relationship and recorded;

[0024] In step (B), the folding method is that if pipeline A and pipeline B are in a series relationship, pipeline A starts at node N1 and ends at node N2; pipeline B starts at node N2 and ends at node N3. Then pipelines A and B are merged to form pipeline C, which starts at node N1 and ends at node N3.

[0025] In step S22, each group of parallel conversion includes:

[0026] (a) Traversing all pipelines in the pipeline network to be converted, and obtaining all pipelines in the pipeline network to be converted that are in a parallel relationship;

[0027] (b) converting each group of pipelines judged to be in a parallel relationship into a new pipeline;

[0028] In step (a), if the start and end node numbers of the n pipelines are equal, the n pipelines are considered to be in a parallel relationship.

[0029] In the step S22, calculating the pipeline flow conductance in the new pipeline network formed after each conversion includes:

[0030] For the new pipeline after the n series pipelines are converted, the converted flow conductance is:

[0031]

[0032] For the new pipeline after the n parallel pipelines are converted, the converted flow conductance is:

[0033]

[0034] For n series-connected pipelines, if the flow rates of m pipelines (m≥1) are known, the converted pipeline flow rate is:

[0035]

[0036] For a new pipeline formed by combining n parallel pipelines, if the flow rates of the n pipelines are all known, the combined pipeline flow rate is:

[0037]

[0038] In step S22, the simplest state judgment includes: if the new pipe network obtained by this folding has the same structure as the new pipe network obtained by the previous folding, it is judged to be the simplest state; or if there is no series relationship or parallel relationship in the pipeline during the current folding operation, it is judged to be the simplest state.

[0039] In step S23, traversing the nodes in the simplest pipe network to perform inflow and outflow balance calculation includes:

[0040] Traversing the nodes in the simplest network, if there are n pipelines starting or ending at this node, and only one of them has an unknown flow, then the flow of this pipeline is:

[0041] Q=|∑Q in -∑Q out |

[0042] After the traversal is completed, the flow rates of all pipes in the simplest pipe network can generally be calculated. If the flow rate still cannot be solved, it needs to be given manually until the flow rates of all pipes in the simplest pipe network are known.

[0043] In step S24, the flow rate of each pipeline in the new pipeline network formed by each restoration is calculated according to the following rules:

[0044] If a reduced pipeline with a flow rate of Q is reduced to n series pipelines, the flow rate of each series pipeline is Q

[0045] Q i =Q

[0046] If a reduced pipeline with a flow rate of Q is reduced to n parallel pipelines, where the flow rates of m pipelines are known, then the flow rate of each unknown pipeline is

[0047]

[0048] The final pressure calculation of the pipeline includes: traversing all pipelines in the graphical file; if any one of the inlet pressure or outlet pressure of the pipeline is known, solving the other unknown pressure: checking whether all boundary and node pressures are known, if there are still unknown pressures, repeating the traversal of the pipeline, and ending if all pressures are known;

[0049] The final pressure calculation formula is:

[0050] G 2 =adf*(P in +HP out )

[0051] Where G is the flow rate of the pipeline, P in is the pipeline inlet node pressure, P out is the pipeline outlet node pressure, H is the pump head:

[0052] For pipelines with pumps:

[0053] H=k 1 *n 2 +k 2 *n*G+k 3 *G 2

[0054] Where n is the normalized speed, k 1 , k ，2 , k ，3 It is the parameter representing the pump head curve. For pipeline without pump: H=0.

[0055] The final conductance determination includes: recalculating the conductances of all pipelines according to the final pressure, the initialization flow rate and a preset formula, replacing step S21 with comparing the node conductances obtained based on the structural parameters to perform conductance correction and obtain the final conductance of the fluid network.

[0056] The final heat transfer coefficient acquisition includes the following steps:

[0057] (1) According to the specific heat capacity C p , flow rate Q and tube inlet and outlet temperature T tout T tin Calculate the heat transfer capacity Q;

[0058] Q=G*C p *(T tout -T tin );

[0059] (2) According to the inlet and outlet temperature T tout T tin , shell side inlet and outlet temperature T sout T sin Calculate the logarithmic mean temperature difference LMTD

[0060] Backflow

[0061] Downstream

[0062] (3) Calculate the heat transfer coefficient K based on the heat transfer amount Q, the average temperature difference LMTD, and the heat transfer area A

[0063]

[0064] The beneficial effects of the present invention are as follows: the present invention calculates the following parameters of four types of components in the pipe network by extracting valid data from the structural parameters and operating data of the power plant, and performing data mapping, data expansion, data accounting and other steps: equipment: heat exchange area and heat exchange coefficient of the heat exchanger; head curve of the pump; boundary: pressure, temperature; node: pressure, temperature; pipeline: flow rate, flow conductance; the calculated results should meet the following requirements: the measurement point data is strictly consistent with the unit data. Conform to the laws of conservation of mass, energy and momentum. Truly reflect the structure and characteristics of the equipment and pipelines. When the calculated results are then brought into the graphical simulation model as initialization conditions for operation, the model will accurately and stably match the operating conditions of the unit, thus completing the debugging of the graphical model. According to the fluid network initialization method shown in the present invention, the specific technical effects are as follows:

[0065] 1) Automatically calculate the initial conditions of the simulation system, reducing the tedious process of manual trial calculation;

[0066] 2) Process-based automatic calculation standardizes the flow network initialization work;

[0067] 3) Make full use of the pipe network structure parameters to make the initialization results closer to the real data;

[0068] 4) The measured point data after initialization is strictly consistent with the power plant data. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a flow chart of the simulation automatic modeling method in the present invention;

[0070] Figure 2 is the original pipe network diagram;

[0071] Figure 3 This is the pipe network diagram after the first parallel connection;

[0072] Figure 4 This is the pipe network diagram after the first parallel connection + series connection;

[0073] Figure 5 This is the pipe network diagram after the second parallel connection;

[0074] Figure 6This is the pipe network diagram after the second parallel + series connection;

[0075] Figure 7 Restore the pipe network diagram once;

[0076] Figure 8 This is the pipeline network diagram after restoration twice. DETAILED DESCRIPTION

[0077] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and does not limit its content.

[0078] like Figure 1 and Figure 8 As shown, the present invention discloses a method for initializing a thermal system simulation model, comprising the following steps:

[0079] S1 obtains the structural and characteristic parameters of the pipelines and equipment in the specified fluid network and the operating parameters of the power plant, and maps the above parameters to the corresponding boundaries, nodes, pipelines, and equipment, where the operating parameters of the power plant include the actual pressure, temperature, and actual flow rate of the nodes and pipelines; the structural and characteristic parameters of the pipelines and equipment in the system include the heat exchange area of ​​the heat exchanger, the head curve parameters of the pump, the length L of the corresponding pipeline, the equivalent diameter d, the cross-sectional area S, and the resistance coefficient λ along the way, the temperature and pressure of the inflow boundary, and the pressure of the outflow boundary;

[0080] S2 initializes flow calculation, based on the flow sensor measurement value obtained in step S1, simplifies and restores the specified fluid network according to the preset series-parallel rule to obtain the final flow of each measuring point and pipeline in the specified fluid network for initialization,

[0081] like Figure 1 As shown, the following steps are included:

[0082] S21 estimates the conductance of each node in the designated fluid network according to the pipeline structure parameters as an estimation basis for the initialization flow;

[0083] For each pipeline in the fluid network, the length L, equivalent diameter d, cross-sectional area S, and pipeline material of the pipeline are obtained according to step S1, and the resistance coefficient λ along the pipeline is obtained by checking the Mody diagram according to the Darcy formula:

[0084]

[0085] Where G is the flow rate of the pipeline, ρ is the density, which can be treated as a constant for liquid water. ΔP is the pipeline head loss ΔP=P in -P out .P in is the pipeline inlet node pressure, P outis the pipeline outlet node pressure.

[0086] make:

[0087] Then we have:

[0088] G 2 =adf*(P in -P out ) (3)

[0089] adf is the conductance of the pipe, which characterizes the flow capacity of the pipe. It can be preliminarily estimated based on the structural parameters of the pipe.

[0090] S22 obtains a designated fluid network graphical file, performs n folding operations on the fluid network in the graphical file according to preset serial connection rules and parallel connection rules, each folding operation includes a set of serial folding and a set of parallel folding to simplify the fluid network to the simplest state, records the folding path, and calculates the flow rate and conductance of each pipeline in the new pipe network formed after each folding according to the conductance of each pipeline and the flow rate of the measuring point obtained in step S21;

[0091] Preferably, each group of series conversion includes: (A) traversing all nodes in the pipeline network to be converted, and obtaining all two pipelines in the pipeline network to be converted that are in a series relationship; B) converting each group of two pipelines determined to be in a series relationship into a new pipeline. (C) repeating steps A and B again until no two pipelines in a series relationship can be found in the current pipeline network.

[0092] Furthermore, in step (A), the determination of the series relationship includes the following steps: obtaining the node corresponding to the smallest number this time; starting the query from the node with the smallest number this time, obtaining the number i of all pipes starting from the node, and recording the pipe number if i=1; obtaining the number j of all pipes ending at the node, and recording the pipe number if j=1; if i=1 and j=1, the two pipes are considered to be in a series relationship and recorded. In step (B), the method of folding is that if pipe A and pipe B are in a series relationship, pipe A starts at node N1 and ends at node N2; pipe B starts at node N2 and ends at node N3, pipes A and B are merged to form pipe C, which starts at node N1 and ends at node N3.

[0093] Preferably, each group of parallel conversion includes: (a) traversing all pipelines in the pipeline network to be converted, and obtaining all pipelines in the pipeline network to be converted that are in a parallel relationship; (b) converting each group of pipelines judged to be in a parallel relationship into a new pipeline; further, in step (a), if the start and end node numbers of the n pipelines are equal, then the n pipelines are considered to be in a parallel relationship.

[0094] Preferably, the simplest state judgment includes: if the new pipe network obtained by this folding has the same structure as the new pipe network obtained by the previous folding, it is judged to be the simplest state; or if there is no series relationship or parallel relationship in the pipeline during this folding operation, it is judged to be the simplest state.

[0095] Preferably, calculating the pipeline conductance and flow rate in the new pipeline network formed after each conversion includes:

[0096] For the new pipeline after the n series pipelines are converted, the converted flow conductance is:

[0097]

[0098] For the new pipeline after the n parallel pipelines are converted, the converted flow conductance is

[0099]

[0100] For n series pipes, if the flow rates of m pipes (m ≥ 1) are known, the pipe flow rate after conversion is:

[0101]

[0102] For a new pipeline after converting n parallel pipelines, if the flow rates of the n pipelines are all known, the converted pipeline flow rate is:

[0103]

[0104] Traversing the nodes in the simplest network, if there are n pipelines starting or ending at this node, and only one of them has an unknown flow, then the flow of this pipeline is:

[0105] Q=|∑Q in -∑Q out | (8)

[0106] After the traversal is completed, the flow rates of all pipes in the simplest pipe network can generally be calculated. If there are still flow rates that cannot be solved, they need to be given manually until the flow rates of all pipes in the simplest pipe network are known.

[0107] S24 reversely restores the fluid network according to the folded path, and calculates the pipeline flow and flow conductance in the new pipeline network formed by each restoration; until the fluid network is restored to the original state, and the corresponding pipeline flow is obtained as the final flow;

[0108] Furthermore, the flow rate of each pipeline in the new pipeline network formed by each restoration is calculated according to the following rules:

[0109] If a reduced pipeline with a flow rate of Q is reduced to n series pipelines, the flow rate of each series pipeline is Q

[0110] Q i =Q (9)

[0111] If a reduced pipeline with a flow rate of Q is reduced to n parallel pipelines, the flow rate of each pipeline is

[0112]

[0113] S3 parameter calculation, based on the heat exchange area of ​​the heat exchanger obtained in step S1, the pump head curve and the final flow obtained in step S2, each node and each pipeline are initialized and calculated to determine the final pressure, final conductance, and final temperature of the pipeline and the final heat transfer coefficient of the heat exchange equipment.

[0114] Preferably, the final pressure calculation of the pipeline includes: traversing all pipelines in the graphical file; if either the inlet pressure or the outlet pressure of the pipeline is known, the other unknown pressure can be solved according to Formula 3: checking whether all boundary and node pressures are known, if there are still unknown pressures, repeating the traversal of the pipeline, and ending if all pressures are known.

[0115] Furthermore, for a pipeline with a pump, the final pressure calculation formula is:

[0116] G 2 =adf*(P in +HP out )

[0117] Where G is the flow rate of the pipeline, P in is the pipeline inlet node pressure, P out is the pipeline outlet node pressure, H is the pump head:

[0118] For pipelines with pumps:

[0119] H=k 1 *n 2 +k 2 *n*G+k 3 *G 2

[0120] Where n is the normalized speed, k 1 , k ，2 , k ，3 The parameter representing the pump head curve for a pipeline without a pump: H = 0.

[0121] Preferably, the final conductance determination includes: recalculating the conductances of all pipelines according to the final pressure, the initialization flow rate and the preset formula 3, replacing step S21 with the node conductance comparison obtained based on the actual pressure value to perform conductance correction and obtain the final conductance of the fluid network;

[0122] Preferably, obtaining the final heat transfer coefficient includes the following steps:

[0123] (1) According to the specific heat capacity C p , flow rate Q and tube inlet and outlet temperature T tout T tin Calculate the heat transfer capacity Q;

[0124] Q=G*C p *(T tout -T tin );

[0125] (2) According to the inlet and outlet temperature T tout T tin , shell side inlet and outlet temperature T sout T sin Calculate the logarithmic mean temperature difference LMTD

[0126] Backflow

[0127] Downstream

[0128] (3) Calculate the heat transfer coefficient K based on the heat transfer amount Q, the average temperature difference LMTD, and the heat transfer area A

[0129]

[0130] S4 imports the boundary, the final pressure, the final temperature, the final flow rate, and the final conductance as initialization conditions for the simulation program to run.

[0131] The following combination Figures 2 to 8 The fluid network shown further illustrates the working principle of the method shown in the present invention.

[0132] Figure 2 This is a pipe network that needs to be initialized. The pipe network has a pump 001PO, a heat exchanger 001RF (tube side), two flow measurement points (001 / 002MD), two pressure measurement points (001 / 002MP) and one temperature measurement point (001MT). The pipe network has one inflow boundary and two outflow boundaries. The pressures of the three boundaries are known, the temperature of the inflow boundary is known, and the shell side inlet and outlet temperatures of the heat exchanger are known.

[0133] Step S1, obtaining the structural and characteristic parameters of the pipelines and equipment in the specified fluid network and the power plant operation parameters, and mapping the above parameters to the corresponding boundaries, nodes, pipelines, and equipment,

[0134] Among them, the length L, equivalent diameter d, cross-sectional area S, and resistance coefficient λ of the relevant pipelines are collected according to the power plant design data, and the flow conductance of each pipeline is estimated according to formula 2. Figure 2The red font in the figure is the estimated flow conductance of the corresponding pipe.

[0135] Collect the heat exchanger heat transfer area and pump head curve from the design data and map them to relevant simulation variables, which may include: traversing all heat exchangers in the graphical file; querying the heat exchanger equipment number; reading the heat exchanger heat transfer area from the design file according to the equipment number; assigning the heat transfer area to the heat exchanger heat transfer area attribute; traversing all pumps in the graphical file; querying the pump equipment number; reading the pump head curve coefficients K1, K2, K3 from the design file according to the equipment number; assigning K1, K2, K3 to the pump's K1, K2, K3 attributes.

[0136] Obtain the operating values ​​of 001MD / 002MD / 001MP / 002MP / 001MT from the power plant operating data, and map them to the pressure and flow variables of the corresponding nodes and pipelines. This may include: traversing all pressure sensors in the graphical file, reading the sensor number; querying the sensor connection node number; reading the sensor operating value from the power plant data interface module; assigning the read value to the pressure attribute of the numbered node; traversing all temperature sensors in the graphical file, reading the sensor number; querying the sensor connection node number; reading the sensor operating value from the power plant data interface module; assigning the read value to the temperature attribute of the numbered node; traversing all flow sensors in the graphical file, reading the sensor number; querying the sensor connection pipeline number; reading the sensor operating value from the power plant data interface module; assigning the read value to the flow attribute of the numbered pipeline.

[0137] S2 initializes flow calculation, simplifies and restores the specified fluid network according to the preset series-parallel rule to obtain the final flow of each measuring point and pipeline in the specified fluid network for initialization, including the following steps:

[0138] S21 estimates the conductance of each node in the designated fluid network according to the pipeline structure parameters as an estimation basis for the initialization flow;

[0139] For a pipeline, we collect the length L, equivalent diameter d, cross-sectional area S, and pipeline material of the pipeline, and then check the Mody diagram to obtain the resistance coefficient λ along the pipeline. According to the Darcy formula, it is:

[0140]

[0141] Where G is the flow rate of the pipeline, ρ is the density, which can be treated as a constant for liquid water. ΔP is the pipeline head loss ΔP = P in -P out .P in is the pipeline inlet node pressure, P out is the pipeline outlet node pressure.

[0142] make:

[0143] Then we have:

[0144] G 2 =adf*(P in -P out )

[0145] adf is the conductance of the pipe, which characterizes the flow capacity of the pipe. It can be preliminarily estimated based on the structural parameters of the pipe.

[0146] S22 obtains a designated fluid network graphical file, performs n folding operations on the fluid network in the graphical file according to preset serial connection rules and parallel connection rules, each folding operation includes a set of serial folding and a set of parallel folding to simplify the fluid network to the simplest state, records the folding path, and calculates the conductance and flow rate of each pipeline in the new pipe network formed after each folding according to the conductance and flow rate measurement points of each pipeline obtained in step S21;

[0147] observe Figure 2 In the original pipe network, there are only two flow measurement points in the entire pipe network, and the topological structure of the pipe network is relatively complex, so it is impossible to directly calculate the flow. At this time, the relationship between series and parallel pipes can be folded to simplify the flow network.

[0148] Parallel equivalent:

[0149] Traverse all pipelines in the graph file

[0150] Record the front and back node numbers of the pipeline

[0151] If the start and end node numbers of n pipelines are equal, then the n pipelines are considered to be in parallel relationship.

[0152] The n pipes are converted into a new pipe, and its conductance is calculated according to formula (5).

[0153] Taking the two pipes between node 3 and node 4 as an example, their conductance is both 1. Then the new pipe starts from node 3 and ends at node 4 after conversion. Its conductance is calculated as 4 according to formula 5.

[0154] Serial reduction:

[0155] Traverse all nodes in the graph file

[0156] Query the number of all pipelines starting from this node i. If i = 1, record the pipeline number

[0157] Query the number j of all pipelines ending at this node. If j=1, record the pipeline number.

[0158] If i=1 and j=1, the two pipelines are considered to be in series relationship.

[0159] The two pipes are combined into a new pipe, and the conductance is calculated according to Formula 4

[0160] Re-traverse all nodes until no more series relationships are found

[0161] Taking the pipelines from node 10 to 11 and from node 11 to boundary 3 as examples, their conductance is both 9. The new pipeline starts from node 10 and ends at boundary 3. According to formula 4, the reduced conductance is 4.5.

[0162] The pipeline network is converted into one group in parallel and one group in series, and the result is Figure 3 , at this time, calculate Figure 3 The reduced flow conductance and flow rate in the virtual pipeline are marked, where the parallel pipeline group of this group includes Figure 2 The pipe numbers shown in the figure are (5, 6), (8, 9), and (13, 14). The new pipe numbers after parallel connection correspond to Figure 3 The pipes shown are numbered 5, 8, and 14.

[0163] The series pipeline groups in this group include Figure 3 The pipeline numbers (1, 2), (10, 11), (12, 14, 15, 16), and (4, 5, 7, 8) shown in the figure correspond to Figure 4 The pipeline numbers shown in the figure are 1, 10, 12, and 4. The pipeline network is converted into one group in parallel and one group in series again, and the result is Figure 5 At this time, calculate the attached Figure 5 The reduced conductance and flow rate in the group. Among them, the parallel reduction of this group includes Figure 4 The pipeline numbers (3, 4) shown in the figure correspond to the pipeline numbers (3, 4) after folding. Figure 5 The pipe number shown in the figure is 4. The series equivalent of this group includes Figure 5 The pipe numbers shown in the figure are (4,10). After folding, the pipes correspond to the attached Figure 6 Pipe number 4 is shown in FIG.

[0164] The pipe network was folded again according to the preset rules, and it was found that no folding could be performed and the pipe network was still Figure 6 state, it can be judged that the pipeline network has been reduced to the simplest state and cannot be further simplified.

[0165] S23 traverses the nodes in the simplest pipe network to calculate the inflow and outflow balance:

[0166] Perform flow balance calculation on node 2. The flow of pipeline 4 can be calculated. The flow of all pipelines in the simplest pipeline network is now known. Figure 6 middle.

[0167] S24: reversely restore the fluid network according to the folded path, and calculate the flow rate of each pipeline in the new pipeline network formed by each restoration; until the fluid network is restored to the original state;

[0168] First, the pipeline network is restored once in series and once in parallel, and the result is Figure 7 After restoration, the flow rate is restored according to formulas 9 and 10.

[0169] Then the pipeline network is restored once in series and once in parallel, and the Figure 8 , and calculate the flow rate according to formulas 9 and 10 to obtain Figure 8 The flow of corresponding nodes and pipelines.

[0170] At this point, the pipeline network has been restored to its original state, and the flow rates of all original pipelines have been calculated.

[0171] S3 parameter calculation, based on the heat exchange area of ​​the heat exchanger obtained in step S1, the pump head curve and the final flow obtained in step S2, each node and each pipeline are initialized and calculated to determine the final pressure, final conductance, and final temperature of the pipeline and the final heat transfer coefficient of the heat exchange equipment.

[0172] Preferably, in this step, according to formula 3 and known pressure, the pressure of other nodes or the final pressure can be calculated and marked on Figure 8 Traversing all pipelines in the graphical file includes the following steps:

[0173] If either the inlet pressure or the outlet pressure of the pipeline is known, the other unknown pressure can be solved according to Formula 3:

[0174] Check if all boundary and node pressures are known. If there are still unknown pressures, repeat the traversal of the pipeline. If all pressures are known, end

[0175] It should be noted that the pump head needs to be considered in the pump pipeline. Correspondingly, the pressure calculation formula is as follows:

[0176] G 2 =adf*(P in +HP out )

[0177] Where H is the pump head:

[0178] H=k1 *n 2 +k 2 *n*G+k 3 *G 2

[0179] Preferably, all pipe conductances are recalculated based on the pressure and final flow rate that have been calculated and Formula 3. As mentioned above, all pressures can be calculated by knowing only the pressure of one node or boundary in the pipe network. In this embodiment, since there are five known pressures in the pipe network, that is, there are four redundant information in the conductance obtained in step S21, and therefore there are four conductances that need to be corrected. The four conductances obtained in step S21 are replaced with the conductances obtained in this calculation. Figure 8 Marked in.

[0180] Preferably, the temperatures of other nodes are calculated based on the temperature of the inflowing working fluid and the temperature of the 001MT measuring point. Assuming that the insulation measures of the pipeline are very good and the heat dissipation of the pipeline to the environment is ignored, in the pipeline network, the temperature of node 8 and boundary 3 is 40℃ after heat exchange, and the temperature of the remaining boundaries and pipeline networks is all 20℃, and marked on Figure 8 middle.

[0181] Preferably, the heat transfer coefficient of the heat exchanger is calculated according to the following process based on the obtained inlet and outlet temperatures, flow rate, and heat exchange area of ​​the heat exchanger.

[0182] According to the specific heat capacity C p , flow rate Q, and tube inlet and outlet temperatures T tout T tin Calculate the heat transfer Q

[0183] Q=G*C p *(T tout -T in )

[0184] According to the tube inlet and outlet temperature T tout T tin , shell side inlet and outlet temperature T sout T sin Calculate the logarithmic mean temperature difference LMTD

[0185] Backflow

[0186] Downstream

[0187] Calculate the heat transfer coefficient K based on the heat transfer amount Q, the average temperature difference LMTD, and the heat transfer area A

[0188]

[0189] At this point, the pressure, temperature, flow rate and conductance of all boundaries and nodes are all known. This is used as the initialization condition of the simulation program and imported into the operation. The pipeline network can quickly stabilize at the calculated value and operate stably.

[0190] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Based on the scheme of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for initializing a thermal system simulation model, characterized in that: The steps include: S1 obtains the structural and characteristic parameters of the pipelines and equipment in the specified fluid network and the operating parameters of the power plant, and maps the above parameters to the corresponding boundaries, nodes, pipelines, and equipment, where the operating parameters of the power plant include the actual pressure, temperature, and actual flow rate of the nodes and pipelines; the structural and characteristic parameters of the pipelines and equipment in the system include the heat exchange area of ​​the heat exchanger, the head curve parameters of the pump, the length, equivalent diameter, cross-sectional area, and resistance coefficient of the corresponding pipeline, the temperature and pressure of the inflow boundary, and the pressure of the outflow boundary; S2 initializes flow calculation, based on the flow sensor measurement value obtained in step S1, simplifies and restores the specified fluid network according to the preset series-parallel rule to obtain the final flow of each measuring point and pipeline in the specified fluid network for initialization; The step S2 comprises: S21 estimates the conductance of each node in the designated fluid network according to the pipeline structure parameters as an estimation basis for the initialization flow; S22 obtains a designated fluid network graphical file, performs n folding operations on the fluid network in the graphical file according to preset serial connection rules and parallel connection rules, each folding operation includes a set of serial folding and a set of parallel folding to simplify the fluid network to the simplest state, records the folding path, and calculates the conductance and flow rate of each pipeline in the new pipe network formed after each folding according to the conductance of each pipeline and the flow rate of the measuring point obtained in step S21; S23 performs inflow and outflow balance calculation on the nodes in the simplest pipe network until the flow of all pipes is calculated; S24 reversely restores the fluid network according to the folded path, and calculates the flow rate and conductance of each pipeline in the new pipeline network formed by each restoration; until the fluid network is restored to the original state, and the flow rate of all pipelines is obtained as the final flow rate; S3 calculates other parameters, and performs initialization calculations on each node and each pipeline based on the heat exchange area of ​​the heat exchanger, the pump head curve, the pressure and temperature sensor measurements obtained in step S1, and the final flow obtained in step S2, to determine the final pressure and temperature of the node, the final temperature of the outflow boundary, the final flow conductance of the pipeline, and the final heat transfer coefficient of the heat exchange equipment; S4 imports the final pressure, final temperature, final flow rate, and final conductance as initialization conditions for the simulation program to run.

2. A method for initializing a thermal system simulation model as claimed in claim 1, characterized in that: In step S21, the conductance of each pipeline is estimated according to the following formula: Among them, adf is the flow conductance of the pipe, ρ is the liquid density, L is the length of the pipe, d is the equivalent diameter, S is the cross-sectional area, and λ is the resistance coefficient along the way.

3. The method for initializing a thermal system simulation model according to claim 1, characterized in that: In step S22, each group of series conversion includes: (A) traversing all nodes in the pipe network to be folded, and obtaining the first group of two pipes in a series relationship in the pipe network to be folded; (B) converting the two pipelines that are judged to be in a series relationship into a new pipeline; (C) Repeating steps A and B again until no two pipes in series relationship can be found in the current pipe network; In step (A), the determination of the series relationship includes the following steps: obtaining the node corresponding to the minimum number of this time; traversing and querying from the minimum node, obtaining the number i of all pipeline roots starting from the node, and recording the pipeline number if i=1; obtaining the number j of all pipeline roots ending at the node, and recording the pipeline number if j=1; if i=1 and j=1, the two pipelines are considered to be in a series relationship and recorded; In step (B), the folding method is that if pipeline A and pipeline B are in a series relationship, pipeline A starts at node N1 and ends at node N2; pipeline B starts at node N2 and ends at node N3. Then pipelines A and B are merged to form pipeline C, which starts at node N1 and ends at node N3.

4. The method for initializing a thermal system simulation model according to claim 1, characterized in that: In step S22, each group of parallel conversion includes: (a) Traversing all pipelines in the pipeline network to be converted, and obtaining all pipelines in the pipeline network to be converted that are in a parallel relationship; (b) converting each group of pipelines judged to be in a parallel relationship into a new pipeline; In step (a), if the start and end node numbers of the n pipelines are equal, the n pipelines are considered to be in a parallel relationship.

5. The method for initializing a thermal system simulation model according to claim 1, characterized in that: In step S22, the simplest state judgment includes: if the new pipe network obtained by this folding has the same structure as the new pipe network obtained by the previous folding, it is judged to be the simplest state; or if there is no series relationship or parallel relationship in the pipeline during the current folding operation, it is judged to be the simplest state.

6. A method for initializing a thermal system simulation model as claimed in claim 1, characterized in that: In step S22, calculating the flow rate and conductance of each pipeline in the new pipeline network formed after each conversion includes: For the new pipeline after the n series pipelines are converted, the converted flow conductance is: For the new pipeline after the n parallel pipelines are converted, the converted flow conductance is: For n series pipes, if the flow rates of m pipes (m ≥ 1) are known, the pipe flow rate after conversion is: For a new pipeline after converting n parallel pipelines, if the flow rates of the n pipelines are all known, the converted pipeline flow rate is:

7. A method for initializing a thermal system simulation model as claimed in claim 1, characterized in that: In step S23, the nodes in the simplest pipe network are traversed to perform inflow and outflow balance calculation: Traversing the nodes in the simplest network, if there are n pipelines starting or ending at this node, and only one of them has an unknown flow, then the flow of this pipeline is: Q=|∑Q in -∑Q out |。 8. A method for initializing a thermal system simulation model as claimed in claim 1, characterized in that: In step S24, the flow rate of each pipeline in the new pipeline network formed by each restoration is calculated according to the following rules: If a reduced pipeline with a flow rate of Q is reduced to n series pipelines, the flow rate of each series pipeline is Q Q i =Q If a reduced pipeline with a flow rate of Q is reduced to n parallel pipelines, where the flow rates of m pipelines are known, then the flow rate of each unknown pipeline is 9. A method for initializing a thermal system simulation model as claimed in claim 1, characterized in that: The final pressure calculation of the pipeline includes: traversing all pipelines in the graphical file; if any one of the inlet pressure or outlet pressure of the pipeline is known, solving the other unknown pressure: checking whether all boundary and node pressures are known, if there are still unknown pressures, repeating the traversal of the pipeline, and ending if all pressures are known; The final pressure calculation formula is: G 2 =adf*(P in +H-P out ) Where G is the flow rate of the pipeline, P in is the pipeline inlet node pressure, P out is the pipeline outlet node pressure, H is the pump head: For pipelines with pumps: H=k1*n 2 +k2*n*G+k3*G 2 Where n is the normalized speed, k1, k ，2 , k ，3 It is the parameter representing the pump head curve. For pipeline without pump: H=0.

10. The method for initializing a thermal system simulation model according to claim 1, characterized in that: The final conductance determination includes: recalculating the conductances of all pipelines according to the final pressure, the initialization flow rate and a preset formula, replacing step S21 with comparing the node conductances obtained based on the structural parameters to perform conductance correction and obtain the final conductance of the fluid network.

11. The method for initializing a thermal system simulation model according to claim 1, characterized in that: The final heat transfer coefficient acquisition includes the following steps: (1) According to the specific heat capacity C p , flow rate Q and tube inlet and outlet temperature T tout T tin Calculate the heat transfer capacity Q; Q=G*C p *(T tout -T tin ); (2) According to the inlet and outlet temperature T tout T tin , shell side inlet and outlet temperature T sout T sin Calculate the logarithmic mean temperature difference LMTD Backflow Downstream (3) Calculate the heat transfer coefficient K based on the heat transfer amount Q, the average temperature difference LMTD, and the heat transfer area A

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