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LM correction method for identification of heat conductivity changing along with temperature

A thermal conductivity, temperature-dependent technology, applied in the field of thermal conductivity identification

Inactive Publication Date: 2016-08-17
DALIAN UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The Levenberg-Marquardt (LM) method is a gradient method that is widely used in optimization and back analysis. For example, the literature "Ukrainczyk N. Thermal diffusivity estimation using numerical inverse solution for 1D heat conduction [J]. International Journal of Heat and MassTransfer ,2009,52:5675-5681." and literature "Xie T, He YL, Tong ZX, et al.An inverse analysis to estimate the endothermic reaction parameters and physical properties of aerogel insulating material[J].Applied Thermal Engineering,2015,87 :214-224." The LM method was used to identify the thermophysical parameters, but the difference method was used to calculate the coefficients of the sensitivity matrix. Therefore, the above-mentioned problems of the general gradient method also existed

Method used

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  • LM correction method for identification of heat conductivity changing along with temperature
  • LM correction method for identification of heat conductivity changing along with temperature
  • LM correction method for identification of heat conductivity changing along with temperature

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Experimental program
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Embodiment 1

[0036] In Example 1, the thermal conductivity as a function of temperature has a functional form, so only constant coefficients in the functional form are identified. according to figure 1 The steps shown are calculated as follows:

[0037] S1: Read the input data from the input file, including the temperature information of the measuring point, geometric conditions, initial conditions, boundary conditions and the imaginary initial value of each coefficient in the functional form of thermal conductivity y=(y 1 ,y 2 ,...,y N );

[0038] S2: By inputting data, solve the transient nonlinear heat conduction forward problem, and obtain the calculated value t(y) of the measuring point temperature;

[0039] S3: Calculate the optimization objective function:

[0040] S ( y ) = Σ i = 1 M ( ...

Embodiment 2

[0053] In Example 2, the thermal conductivity as a function of temperature does not have a functional form, therefore, the thermal conductivity at a specified temperature is identified. according to figure 1 The steps shown are calculated as follows:

[0054] S1: Read the input data from the input file, including the temperature information of the measuring point, geometric conditions, initial conditions, boundary conditions and the hypothetical initial value of the thermal conductivity at the specified temperature y=(y 1 ,y 2 ,...,y N );

[0055] S2: By inputting data, solve the transient nonlinear heat conduction forward problem, and obtain the calculated value t(y) of the measuring point temperature. It should be noted that the thermal conductivity at other temperatures is given by y=(y 1 ,y 2 ,...,y N ) is characterized by linear interpolation;

[0056] S3: Calculate the optimization objective function:

[0057] S ( y ...

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Abstract

The invention discloses an LM correction method for identification of heat conductivity changing along with the temperature. The method comprises the following steps that input data is read from an input file; the measurement physical quantity temperature or the heat flux calculation value is obtained; an optimized objective function is calculated; whether convergence is conducted or not is checked; the identification parameter update value is obtained; an identification result is output after multi-time iteration. A traditional LM method is introduced through a complex variable derivation method, coefficients of a sensitivity matrix are accurately calculated, accordingly, high-precision identification of heat conductivity changing along with the temperature is achieved, and the precision and the stability of the traditional LM method in the process of identification of heat conductivity changing along with the temperature are improved. The complex variable derivation method is a very promising method. Compared with a traditional finite difference method, a first-order partial derivative only needs to be directly calculated, truncation errors are avoided, and the method does not depend on the space step length.

Description

technical field [0001] The invention relates to thermal conductivity identification technology in aerospace field, iron and steel industry, chemical industry field and material preparation and characterization, in particular, a thermal conductivity identification method of new material / structure changing with temperature. Background technique [0002] In order to meet the higher and higher Mach number requirements, it is necessary to continuously develop new low thermal conductivity insulation materials, whose thermal conductivity varies with temperature and has a nonlinear relationship. It is very difficult to determine the thermal physical parameters of thermal insulation materials with temperature changes, because: the thermal conductivity value is very small, between 0.0001 and 0.1; the temperature range is large, between 0 and nearly 2000 ° C, which needs to be determined There are many thermophysical parameters that change with temperature. Taking 0 to 1200°C as an exa...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50
CPCG06F30/367G06F2119/08
Inventor 崔苗高效伟杨恺冯伟哲王胜东张永存
Owner DALIAN UNIV OF TECH
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