Method for calculating temperature of tube wall of platen superheater of ultra supercritical boiler by assistance of numerical simulation

Abstract

The invention discloses a method for calculating the temperature of the tube wall of a platen superheater of an ultra supercritical boiler by the assistance of numerical simulation. The method comprises the steps of: step (1) modeling the whole boiler containing the platen superheater, and constructing a mathematical model of a calculating method for the temperature of the tube wall of the superheater; step (2) conducting the numerical simulation on the constructed mathematical model to obtain the smoke temperature and smoke speed distribution nearby a platen superheater calculation area, selecting calculating data which are taken as initial conditions of the thermodynamic calculation and the hydrodynamic force calculation of the platen superheater; step (3) calculating the temperature of the wall of the platen superheater by utilizing the thermodynamic calculation and the hydrodynamic force calculation; step (4) checking and calculating the obtained tube wall of the whole platen superheater; and step (5) outputting a calculated result. According to the calculation method, the advantages of both the numerical simulation and the thermodynamic calculation can be considered, the detail wall temperature distribution in the boiler can be obtained, and meanwhile, the accuracy of the temperature wall result is also improved.

Description

technical field [0001] The invention relates to a calculation method for a tube wall of a superheater in a boiler, in particular to a calculation method for the tube wall temperature of a panel superheater of an ultra-supercritical boiler assisted by numerical simulation. Background technique [0002] In my country, during the operation of power plant boilers, superheater tube burst accidents occur from time to time, and the reasons are various, which can be roughly summarized as: long-term overheating and overheating in the superheater area; low working medium flow rate in the tube, local overheating caused by uneven flow rate; Uneven distribution of smoke temperature and smoke velocity near the superheater. For superheated systems, pipe bursts are mostly caused by overheating of the pipe wall. The superheater is in a high-temperature environment, and the temperature difference between the inside and outside of the tube wall is large, and sometimes it may reach 100°C. This ...

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Problems solved by technology

[0010] Disadvantage 1: Problems in setting the wall boundary conditions of the panel superheater

[0012] In the numerical simulation process of the existing technology, the wall of the panel superheater is set as the boundary condition of heat flux, and the total heat transfer of the panel superheater is all converted into convective heat transfer for simulation, although this method reduces the complexity of the model However, the characteristics of the wall-to-wall radiation heat transfer process and convective heat transfer process are different. In order to ensure the accuracy of the simulation results, try not to convert the two heat transfer methods during the simulation process.

[0013] Disadvantage 2: Calculating the reading problem of smoke temperature and smoke velocity distribution near the heating surface

After the simulation is completed, the smoke temperature and smoke velocity distribution used in thermal calculations are only read and input manually. Due to the large amount of values, there are errors when reading values ​​manually, and the workload is large. The calculation of wall temperature Speed ​​and computational accuracy have a greater impact

[0014] Disadvantage 3: The wall temperature calculation of the existing method only considers the inhomogeneity of convective heat release and heat absorption along the circumference of the pipeline, the hydraulic inhomogeneity between the panels and the tubes with the same panel, so that the final calculated wall temperature distribution results are different from the real temperature. large error

[0015] Disadvantage 4: Repeated checking and correction of the wall temperature of the heating surface

Since the thermal calculation is a zero-dimensional model, the heat absorption of each point cannot be obtained, and only the average temperature of the entire screen area can be calculated. Therefore, the boundary condition of the screen area can only be set to the same heat flux density. There will be a large error in the distribution of smoke temperature and smoke velocity. Using this result as the initial parameter of thermal calculation will greatly affect the accuracy of the final result of wall temperature distribution.

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