Numerical Study of the Influence of Coupling Interface Emissivity on Aerogel Metal Thermal Protection Performance

Lou, Fengfei; Dong, Sujun; Ma, Yanying; Qi, Bin; Zhu, Keyong

doi:10.3390/gels7040250

Cited by 3 publications

(2 citation statements)

References 26 publications

(40 reference statements)

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“…As shown in Figure 13 , it is the radiation heat transfer process inside the aerogel medium. The radiative intensity within aerogel is governed by the radiative transport equation (RTE) [ 58 ], and the RTE is shown in Formula (25).

where

are the extinction, absorption and scattering coefficients, respectively;

is the radiative intensity emitted by a black body;

represents the radiative intensity of space position r and transmission direction

, which is a vector;

is the scattering phase function, which is the ratio of the scattering intensity in the s direction caused by incident radiation in the

direction to the average scattering intensity in the 4π scattering space.…”

Section: Characterization Methods Of Thermal Insulation Performancementioning

confidence: 99%

“…The reliability and accuracy of steady state method are ideal, but the long measurement period is considered to be the most outstanding feature. Especially when the thermal physical properties of insulation materials are measured, the size of the sample is generally required to be large enough to reduce the influence of the surrounding environment [ 58 , 87 ]. Because the thermal conductivity of thermal insulation materials is very low, it will take a long time to establish a stable temperature gradient in the thickness direction of the sample, which is more obvious when measuring at high temperature.…”

Section: Test Methods Of Thermal Insulation Performancementioning

confidence: 99%

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Thermal Insulation Performance of Aerogel Nano-Porous Materials: Characterization and Test Methods

Lou

Dong

Zhu

et al. 2023

Gels

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Due to the extremely high porosity and extremely low density of nano-porous thermal insulation materials, the characteristic size of the pores inside the materials and the characteristic size of the solid skeleton structure are on the nanometer scale, which leads to the obvious nanoscale effect of the heat transfer law inside the aerogel materials. Therefore, the nanoscale heat transfer characteristics inside the aerogel materials and the existing mathematical models for calculating the thermal conductivity of various heat transfer modes at the nanoscale need to be summarized in detail. Moreover, in order to verify the accuracy of the thermal conductivity calculation model of aerogel nano-porous materials, correct experimental data are required to modify the model. Because the medium is involved in radiation heat transfer, the existing test methods have a large error, which brings great difficulties to the design of nano-porous materials. In this paper, the heat transfer mechanism, characterization methods, and test methods of thermal conductivity of nano-porous materials are summarized and discussed. The main contents of this review are as follows. The first part introduces the structural characteristics and specific application environment of aerogel. In the second part, the characteristics of nanoscale heat transfer of aerogel insulation materials are analyzed. In the third part, the characterization methods of thermal conductivity of aerogel insulation materials are summarized. In the fourth part, the test methods of thermal conductivity of aerogel insulation materials are summarized. The fifth part gives a brief conclusion and prospect.

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where

are the extinction, absorption and scattering coefficients, respectively;

is the radiative intensity emitted by a black body;

represents the radiative intensity of space position r and transmission direction

, which is a vector;

is the scattering phase function, which is the ratio of the scattering intensity in the s direction caused by incident radiation in the

direction to the average scattering intensity in the 4π scattering space.…”

Section: Characterization Methods Of Thermal Insulation Performancementioning

confidence: 99%

Section: Test Methods Of Thermal Insulation Performancementioning

confidence: 99%

Thermal Insulation Performance of Aerogel Nano-Porous Materials: Characterization and Test Methods

Lou

Dong

Zhu

et al. 2023

Gels

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Temperature-Dependent Thermal Parameter Identification of Ceramic Nanorod Aerogels Composite in the Ultrahigh Temperature Environment

Shi

et al. 2023

Int. J. Appl. Mechanics

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The identification of the thermal properties of advanced materials is of great importance in engineering application. In this work, an inverse scheme is proposed to identify the temperature-dependent thermal parameters of ceramic nanorod aerogels (CNRAs) composite in the ultrahigh temperature environment up to 1873[Formula: see text]K. The feasibility of the proposed method is successfully tested by an analytical solution for CNRAs with known material properties. Furthermore, the temperature-dependent thermal properties of CNRAs are successfully obtained using the experimental data acquired from the heat conduction experimental testing for a CNRAs plate. Lastly, the obtained thermal properties are used to simulate an arc-heated wind tunnel (AHWT) test of a receiving satellite antenna assembly using the FEM method. The simulated temperature at measured data has a very good agreement with the experimental data. This further demonstrates the strong capability of the proposed inverse method. In summary, the proposed approach provides an important approach for the identification of nonlinear and temperature-dependent thermal properties of advanced materials.

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Study on Ground Experimental Method of Stagnation Point Large Heat Flux of Typical Sharp Wedge Leading Edge Structure

Wang,

Lou,

et al. 2023

Aerospace

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In this paper, aimed at the problem of large temperature gradient thermal testing with the typical sharp wedge leading edge structure of a hypersonic vehicle, a subsonic high-temperature combustion gas heating (SHCH) test device is used to conduct a series of experiments on the heat flux simulation ability of subsonic high-temperature combustion gas in the stagnation point region. Firstly, for a hypersonic vehicle with a flying height of 24 km and Mach number range of 4~6.5, the stagnation point heat flux in the head area is obtained by numerical calculation of a typical leading edge structure, which is used as the experimental target of the thermal structure test. Secondly, an experimental specimen with a Gardon heat flux meter is designed with the same shape and size as the specimen in the numerical simulations to prepare for the subsequent SHCH test. Thirdly, a method to determine the combustion gas temperature based on a Kriging surrogate model is proposed. CFD numerical simulation is conducted using the SHCH test model, and the numerical calculation results are used as the training dataset. The Kriging surrogate model is used to establish an approximate fitting relationship between the stagnation point heat flux and experimental parameters under SHCH conditions. The corresponding combustion gas temperature values are found, respectively, with the hypersonic aerodynamic heat flux at Mach 5.0~5.4 as the target value. Finally, stagnation point heat flux testing of low-speed and high-temperature combustion gas is performed at different combustion gas temperatures. The experimental and target values obtained from hypersonic aerodynamic thermal simulations are compared and analyzed to verify the heating capacity of SHCH and the feasibility of hypersonic aerothermal simulation testing.

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Numerical Study of the Influence of Coupling Interface Emissivity on Aerogel Metal Thermal Protection Performance

Cited by 3 publications

References 26 publications

Thermal Insulation Performance of Aerogel Nano-Porous Materials: Characterization and Test Methods

Thermal Insulation Performance of Aerogel Nano-Porous Materials: Characterization and Test Methods

Temperature-Dependent Thermal Parameter Identification of Ceramic Nanorod Aerogels Composite in the Ultrahigh Temperature Environment

Study on Ground Experimental Method of Stagnation Point Large Heat Flux of Typical Sharp Wedge Leading Edge Structure

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