Method and system for calculating heat transfer coefficient of supercritical counterflow flue gas waste heat recovery device

Abstract

The application discloses a supercritical counterflow flue gas waste heat recovery device heat transfer coefficient calculation method and system, belongs to the technical field of waste heat utilization of thermal system; the method divides the waste heat recovery device into a plurality of micro-element heat exchange sections along the flow direction, and assumes constant physical properties in the micro-element; energy balance equations and micro-element heat transfer equations of hot fluid sides and cold fluid sides are respectively constructed, and a micro-element section local heat transfer coefficient expression is obtained by coupling derivation; combined with supercritical working medium thermal property discrete data, numerical integration is used for piecewise iterative solution, and the local heat transfer coefficient distributed along the heat exchange surface is obtained. The application breaks through the limitation of the traditional average method, can accurately reflect the non-uniform distribution law of the heat transfer coefficient in the pseudo-critical region, and the calculation precision is significantly better than that of the traditional method, thereby providing reliable theoretical basis and data support for the fine design, performance degradation early warning and operation optimization regulation and control of the supercritical unit flue gas waste heat recovery device.

Description

Technical Field

[0001] This invention belongs to the field of waste heat utilization technology of thermal systems, and relates to a method and system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device. Background Technology

[0002] In the fields of energy, power, and industrial production, low-temperature flue gas waste heat recovery is a core technological path to achieve energy conservation and emission reduction in coal-fired units, industrial boilers, and various waste heat utilization systems. By deploying flue gas waste heat recovery devices, the exhaust gas temperature can be effectively reduced and the system thermal efficiency improved. Currently, the thermal design, performance evaluation, and operation monitoring of such equipment generally follow traditional standards such as the "Standard Method for Thermal Calculation of Boiler Units" (1973 and 1976 editions). Its core assumption is that the thermophysical parameters of the heat exchange medium are constant along the heat transfer surface, and the heat transfer coefficient can be used as a constant for global average calculation.

[0003] The aforementioned traditional methods are highly applicable under subcritical pressure conditions. Since the specific heat, density, and thermal conductivity of water change relatively little with temperature within the subcritical parameter range, the average heat transfer coefficient method can meet engineering accuracy requirements. However, with the large-scale application of supercritical units and the development of high-pressure industrial waste heat recovery systems towards higher parameters, flue gas waste heat recovery devices generally operate in the supercritical pressure range above 22.1 MPa. Under these conditions, the working fluid's thermal properties exhibit extremely strong nonlinear characteristics: especially in the quasi-critical temperature region, the specific heat of the working fluid experiences a sudden peak, and the density and thermal conductivity also fluctuate drastically with temperature, resulting in a significant non-uniform distribution of the heat transfer coefficient along the heat exchange surface. If the traditional assumption of constant properties and the global averaging algorithm are still used, a calculation deviation of more than 10% will occur, failing to accurately characterize the true heat transfer characteristics of the equipment.

[0004] Furthermore, counter-current arrangement is the mainstream structural form of high-pressure flue gas waste heat recovery devices, which can improve heat exchange efficiency by optimizing the heat transfer temperature difference. However, the existing technology system has obvious limitations: on the one hand, current standards do not consider the dynamic impact of continuous changes in the physical properties of the working fluid under supercritical pressure on the heat transfer coefficient, and can only provide a single average heat transfer coefficient, which cannot reveal the distribution law along the process; on the other hand, traditional methods are difficult to capture the early characteristics of local heat transfer deterioration or ash accumulation and blockage, resulting in delayed early warning of equipment performance degradation and the inability to achieve precise operation control and energy efficiency optimization.

[0005] In summary, the heat transfer calculation of existing supercritical pressure flue gas waste heat recovery devices suffers from technical defects such as unreasonable property assumptions, lack of solution for parameters along the process, and insufficient basis for performance monitoring. There is an urgent need to establish a distributed heat transfer coefficient calculation method that is adapted to the variable property characteristics of supercritical systems and can reflect the distributed characteristics along the process, so as to fill the technical gap in the refined design and intelligent operation and maintenance of high-pressure waste heat recovery systems. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, so as to solve the technical problems of inaccurate calculation results of the heat transfer coefficient of the flue gas waste heat recovery device and insufficient monitoring and diagnosis basis in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, comprising the following steps: The supercritical counter-current flue gas waste heat recovery unit is divided into several continuous micro-element heat exchange sections along the flow direction. Construct the energy balance equation and heat transfer equation of the micro-element heat exchange section; By coupling the energy balance equation and the heat transfer equation of the micro-element segment, the expression for the local heat transfer coefficient of the micro-element segment is obtained. The local heat transfer coefficient distribution of the entire heat exchange surface is then solved segment by segment using the numerical integration method.

[0008] Furthermore, the energy balance equation of the micro-element heat exchange section includes the calculation formula for the micro-element heat exchange on the hot fluid side and the calculation formula for the micro-element heat exchange on the cold fluid side.

[0009] Furthermore, the formula for calculating the heat exchange capacity of the micro-element on the heat fluid side is:

[0010] In the formula, The heat exchange of the heat fluid in the flue gas waste heat recovery unit through a micro-element area dA; This represents the average specific heat of the thermal fluid at the micro-element segment; The mass flow rate of the heat fluid in the flue gas waste heat recovery unit; For the heat transfer fluid of the flue gas waste heat recovery unit in a micro-element area dA The change in temperature at that location; The heat dissipation coefficient of the flue gas waste heat recovery device.

[0011] Furthermore, the formula for calculating the heat exchange of the micro-element on the cold fluid side is:

[0012] In the formula, The heat exchange of the cold fluid in the flue gas waste heat recovery unit through a micro-element area dA; This represents the average specific heat of the cold fluid at the micro-element segment; The mass flow rate of the cold fluid in the flue gas waste heat recovery unit; For the cold fluid of the flue gas waste heat recovery unit in a micro-element area dA The amount of temperature change at that location.

[0013] Furthermore, the expression for the heat transfer equation of the infinitesimal segment is:

[0014] In the formula, Let dA be the dimensionless integral corresponding to the area of ​​the infinitesimal element, where x The value varies between 0 and 1, representing the length of the dimensionless flue gas waste heat recovery device. for the area of ​​the infinitesimal element dA The heat transfer coefficient of the flue gas waste heat recovery unit at the location; A This represents the total heat transfer area of ​​the flue gas waste heat recovery unit. ΔT ( x () represents the temperature difference between the hot and cold fluids.

[0015] Furthermore, the step of coupling the energy balance equation and the heat transfer equation of the micro-element segment to obtain the expression for the local heat transfer coefficient of the micro-element segment specifically includes: By coupling the calculation formula for the heat transfer of the cold fluid side of the infinitesimal segment's energy balance equation with the heat transfer equation of the infinitesimal segment, we obtain:

[0016] The expression for the local heat transfer coefficient of the infinitesimal segment is:

[0017] In the formula, The mass flow rate of the cold fluid in the flue gas waste heat recovery unit; For the cold fluid of the flue gas waste heat recovery unit in a micro-element area dA The amount of temperature change at that location.

[0018] Furthermore, the method also includes: calculating the equivalent heat transfer performance of the entire process based on the local heat transfer coefficient distribution of the entire heat exchange surface, and determining the heat exchange capacity level of the waste heat recovery device in combination with a preset threshold, so as to realize equipment operation status assessment and performance degradation early warning.

[0019] Secondly, the present invention provides a system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, comprising: The micro-element partitioning module is used to divide the supercritical counter-current flue gas waste heat recovery unit into several continuous micro-element heat exchange sections along the flow direction. The equation building module is used to construct the energy balance equation and heat transfer equation of the micro-element heat exchange section. The heat transfer coefficient calculation module is used to couple the energy balance equation and the heat transfer equation of the micro-element segment to obtain the expression of the local heat transfer coefficient of the micro-element segment, and then solve the local heat transfer coefficient distribution of the entire heat exchange surface segment by segment using the numerical integration method.

[0020] Thirdly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device as described above.

[0021] Fourthly, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device as described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method and system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device. Based on the micro-element heat transfer theory, it approximates stable physical properties within the micro-element scale. This avoids the mathematical model divergence caused by drastic fluctuations in parameters such as the specific heat and density of the supercritical working fluid, while preserving the physical reality of property changes, thus significantly improving calculation accuracy. By constructing a coupled iterative model of the energy balance equation of the hot and cold fluids and the micro-element heat transfer equation, it breaks through the limitation of traditional methods that can only output a single average heat transfer coefficient. It can accurately reproduce the non-uniform distribution law of the heat transfer coefficient along the heat transfer surface and intuitively reflect the heat transfer enhancement or weakening characteristics near the quasi-critical region. Furthermore, this invention can infer the internal heat transfer state based solely on conventional operating parameters such as inlet and outlet temperatures and flow rates, without the need for additional measuring points. It provides a quantitative basis for identifying localized ash accumulation, scaling, and early heat transfer degradation. This invention can clearly present the true evolution trend of the heat transfer coefficient gradually decreasing from the flue gas inlet to the outlet. Compared with traditional methods, it is more in line with engineering practice and can directly serve the refined design optimization, real-time performance monitoring, and intelligent operation control of supercritical / ultra-supercritical units and high-pressure waste heat recovery systems, significantly improving equipment safety and energy utilization efficiency. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the system of the present invention; Figure 3 This is a schematic diagram illustrating the method for calculating the heat transfer coefficient of a flue gas waste heat recovery unit under supercritical operating conditions according to an embodiment of the present invention. Figure 4 This is a flowchart illustrating the method for calculating the heat transfer coefficient of a flue gas waste heat recovery unit under supercritical operating conditions according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the heat transfer process in the flue gas waste heat recovery device according to an embodiment of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] It should be understood that in the embodiments of this application, "at least one" means one or more, and "more than one" means two or more. "And / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. The character " / " generally indicates that the related objects before and after it are in an "or" relationship. "Contains A, B and / or C" means containing any one, two, or three of A, B, and C.

[0028] It should be understood that in the embodiments of this application, "B corresponding to A", "B corresponding to A", "A corresponds to B" or "B corresponds to A" means that B is associated with A, and B can be determined based on A. Determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0029] The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device provided by this invention can be executed by an electronic device, such as a terminal or a server. The terminal can be a smartphone, tablet, laptop, or other similar device. The server can be a standalone physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms. It is understood that this invention does not limit the specific entity executing the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device.

[0030] The technical solution of this application will be described in detail below through specific embodiments. It should be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments described below are used to explain the technical solution of this application and are not intended to limit actual use.

[0031] See Figure 1 and Figure 3 This invention discloses a method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, comprising the following steps: Step 1: Dividing into infinitesimal elements and basic assumptions The waste heat recovery unit is divided into several micro-element heat exchange sections along the flow direction. Within the micro-element scale, the thermal properties of the working fluid and the local heat transfer coefficient are assumed to be constant. It is assumed that the mass flow rate of the hot and cold fluids and the heat dissipation coefficient of the device remain constant along the flow path, and axial heat conduction is ignored.

[0032] Step 2, Energy Balance Equation for Infinite Elements Heat fluid in a micro-element area Heat exchange at the point: (1) In the formula: The heat exchange capacity (kW) of the heat fluid in the flue gas waste heat recovery unit through a micro-element area dA is denoted as heat exchange fluid. The average specific heat of the thermal fluid at the micro-element segment, kJ / (kg) ℃); The mass flow rate of the heat fluid in the flue gas waste heat recovery unit is kg / s; For the heat transfer fluid of the flue gas waste heat recovery unit in a micro-element area dA Temperature change at a location, in °C; The heat dissipation coefficient of the flue gas waste heat recovery device.

[0033] Cold fluid in a micro-element area Heat exchange at the point: (2) In the formula: The heat exchange capacity (kW) of the cold fluid in the flue gas waste heat recovery unit through a micro-element area dA; The average specific heat of the cold fluid at the micro-element segment, kJ / (kg) ℃); The mass flow rate of the cold fluid in the flue gas waste heat recovery unit is kg / s; For the cold fluid of the flue gas waste heat recovery unit in a micro-element area dA The change in temperature at a given location, in °C.

[0034] Step 3, Heat transfer equation of infinitesimal segment The heat exchange of the micro-element segment satisfies the basic heat transfer equation: (3) In the formula: Let dA be the dimensionless integral corresponding to the area of ​​the infinitesimal element, where x The value varies between 0 and 1, representing the length of the dimensionless flue gas waste heat recovery unit. for the area of ​​the infinitesimal element dA Heat transfer coefficient of the flue gas waste heat recovery unit at the location, W / m² ℃; A The total heat transfer area of ​​the flue gas waste heat recovery unit is in m².

[0035] Combining equations (2) and (3), we obtain: (4) Step 4: Integral model of process heat transfer coefficient For both sides of equation (4) simultaneously in the infinitesimal segment Integrating, we get: (5) From equation (5), we obtain the economizer micro-element segment. The heat transfer coefficient at that point is: (6) Given the boundary conditions such as flue gas inlet temperature, working fluid inlet and outlet temperatures, mass flow rate, and total heat transfer area, numerical integration is used to solve the problem piece by piece, obtaining the local heat transfer coefficient of each micro-element segment, thus realizing distributed computing throughout the entire process.

[0036] Step 5, preferably, calculates the equivalent heat transfer performance of the entire process based on the local heat transfer coefficient distribution of the entire heat exchange surface, and determines the heat exchange capacity level of the waste heat recovery unit by combining it with a preset threshold, so as to realize the equipment operation status assessment and performance degradation early warning.

[0037] Calculation example: see Figure 4A counter-current flue gas waste heat recovery unit for a 600MW supercritical once-through boiler ( Figure 5 Taking a boiler operating at 100% BMCR as an example: Inlet flue gas temperature of the waste heat recovery unit is 564℃, inlet working fluid temperature is 282℃, outlet working fluid temperature is 336.8℃, M1 = 531.3889 kg / s, M2 = 682.1892 kg / s, and total heat transfer area A = 17590.33 m². The specific heat of the working fluid is obtained from the steam thermodynamic properties table, and the working fluid pressure is 29 MPa.

[0038] By solving equations (1) to (5) simultaneously, the heat transfer coefficient of the flue gas waste heat recovery device corresponding to a 1℃ change in working fluid temperature is obtained by numerical integration. The calculation results are shown in Table 1.

[0039] Table 1 Calculation results of heat transfer coefficient of micro-element segment

[0040] The average heat transfer coefficient obtained by the traditional standard method of thermal calculation (1973 and 1976 editions) is 52.0735.

[0041] As shown in Table 1, after dividing the flue gas waste heat recovery unit into 55 micro-segments, the heat transfer coefficients of each segment are different, and they gradually decrease from the flue gas inlet to the flue gas outlet. Traditional methods can only provide the average heat transfer coefficient and cannot reflect the variation along the process. The method of this invention effectively solves the problem of accurately calculating the heat transfer coefficient of the heating surface under supercritical pressure, and provides a reliable theoretical basis for the heat transfer calculation and performance monitoring of supercritical pressure counter-current flue gas waste heat recovery units.

[0042] See Figure 2This invention discloses a system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, comprising a micro-element partitioning module, an equation construction module, and a heat transfer coefficient calculation module. The micro-element partitioning module divides the supercritical counter-current flue gas waste heat recovery device into several continuous micro-element heat exchange sections along the flow direction. The equation construction module constructs the energy balance equation and heat transfer equation for each micro-element heat exchange section. The heat transfer coefficient calculation module couples the energy balance equation and heat transfer equation of each micro-element section to obtain an expression for the local heat transfer coefficient of the micro-element section, and then uses numerical integration to solve for the local heat transfer coefficient distribution across the entire heat exchange surface segment by segment. The micro-element partitioning module of this system is configured to discretize the complex physical heat transfer surface into several interconnected micro-element heat transfer segments along the fluid flow direction, based on the heat exchange tube length and node discretization requirements, thereby constructing the geometric basis for numerical calculations. The equation construction module is used to establish the energy balance equations for the hot fluid side and the cold fluid side, including heat dissipation loss terms, within each micro-element segment, and simultaneously construct the micro-element segment heat transfer equation based on the fundamental laws of heat transfer, thus locking the thermophysical parameters at the micro-element scale and avoiding global nonlinearity problems. The heat transfer coefficient calculation module, as the core processing unit of the system, is configured to execute a coupled iterative algorithm, that is, by simultaneously solving the energy equations for the hot and cold fluids and the heat transfer equations, deriving the coefficient of heat transfer based on the cold fluid flow. This invention provides an expression for the local heat transfer coefficient, using specific heat, rate of temperature change, and local temperature difference as variables. It employs a numerical integration method, starting with known inlet and outlet boundary conditions, and iteratively solves the problem segment by segment along the flow direction. This outputs a continuously distributed local heat transfer coefficient curve along the heat exchange surface, rather than a single average value. This invention not only achieves precise tracking of the drastic fluctuations in the physical properties of supercritical working fluids in the quasi-critical region through modular design, significantly improving the physical fidelity of heat transfer calculations, but also intuitively identifies the location of local heat transfer deterioration or ash accumulation blockage through the output distributed data. Therefore, it provides a high-precision, quantifiable, and logically rigorous engineering calculation tool for optimizing the heating surface design, formulating soot blowing strategies, and monitoring online energy efficiency of supercritical units.

[0043] In one embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in the operation of a method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device.

[0044] This invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device in the above embodiments.

[0045] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0046] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0047] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0048] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, characterized in that, Includes the following steps: The supercritical counter-current flue gas waste heat recovery unit is divided into several continuous micro-element heat exchange sections along the flow direction. Construct the energy balance equation and heat transfer equation of the micro-element heat exchange section; By coupling the energy balance equation and the heat transfer equation of the micro-element segment, the expression for the local heat transfer coefficient of the micro-element segment is obtained. The local heat transfer coefficient distribution of the entire heat exchange surface is then solved segment by segment using the numerical integration method.

2. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, The energy balance equation of the micro-element heat exchange section includes the calculation formulas for the heat exchange of micro-element on the hot fluid side and the heat exchange of micro-element on the cold fluid side.

3. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, The formula for calculating the heat exchange capacity of the micro-element on the heat fluid side is: In the formula, The heat exchange of the heat fluid in the flue gas waste heat recovery unit through a micro-element area dA; This represents the average specific heat of the thermal fluid at the micro-element segment; The mass flow rate of the heat fluid in the flue gas waste heat recovery unit; For the heat transfer fluid of the flue gas waste heat recovery unit in a micro-element area dA The change in temperature at that location; The heat dissipation coefficient of the flue gas waste heat recovery device.

4. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, The formula for calculating the heat exchange capacity of the micro-element on the cold fluid side is: In the formula, The heat exchange of the cold fluid in the flue gas waste heat recovery unit through a micro-element area dA; This represents the average specific heat of the cold fluid at the micro-element segment; The mass flow rate of the cold fluid in the flue gas waste heat recovery unit; For the cold fluid of the flue gas waste heat recovery unit in a micro-element area dA The amount of temperature change at that location.

5. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, The expression for the heat transfer equation of the micro-element segment is: In the formula, Let dA be the dimensionless integral corresponding to the area of ​​the infinitesimal element, where x The value varies between 0 and 1, representing the length of the dimensionless flue gas waste heat recovery device. for the area of ​​the infinitesimal element dA The heat transfer coefficient of the flue gas waste heat recovery unit at the location; A This represents the total heat transfer area of ​​the flue gas waste heat recovery unit. ΔT ( x () represents the temperature difference between the hot and cold fluids.

6. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, The step of coupling the energy balance equation and the heat transfer equation of the micro-element segment to obtain the expression for the local heat transfer coefficient of the micro-element segment specifically includes: By coupling the formula for calculating the heat transfer of the cold fluid side of the infinitesimal element in the energy balance equation of the infinitesimal element segment with the heat transfer equation of the infinitesimal element segment, we obtain: The expression for the local heat transfer coefficient of the infinitesimal segment is: In the formula, The mass flow rate of the cold fluid in the flue gas waste heat recovery unit; For the cold fluid of the flue gas waste heat recovery unit in a micro-element area dA The amount of temperature change at that location.

7. The method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device according to claim 1, characterized in that, Also includes: Based on the local heat transfer coefficient distribution of the entire heat exchange surface, the equivalent heat transfer performance of the entire process is calculated. Combined with a preset threshold, the heat exchange capacity level of the waste heat recovery unit is determined, thereby realizing equipment operation status assessment and performance degradation early warning.

8. A system for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device, characterized in that, include: The micro-element partitioning module is used to divide the supercritical counter-current flue gas waste heat recovery unit into several continuous micro-element heat exchange sections along the flow direction. The equation building module is used to construct the energy balance equation and heat transfer equation of the micro-element heat exchange section. The heat transfer coefficient calculation module is used to couple the energy balance equation and the heat transfer equation of the micro-element segment to obtain the expression of the local heat transfer coefficient of the micro-element segment, and then solve the local heat transfer coefficient distribution of the entire heat exchange surface segment by segment using the numerical integration method.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for calculating the heat transfer coefficient of a supercritical counter-current flue gas waste heat recovery device as described in any one of claims 1-7.

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