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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

EXPERIMENTAL INVESTIGATION OF COMBINED CONDUCTIVE AND RADIATIVE HEAT TRANSFER IN SILICA AEROGEL COMPOSITE AT HITH TEMPERATURES

Hua Liu
Harbin Institute of Technology, No. 92 West Dazhi Street, Nangang District, Harbin, 150001, China

Xin-Lin Xia
Harbin Institute of Technology

Jing Wang
Harbin Institute of Technology, No. 92 West Dazhi Street, Nangang District, Harbin, 150001, China

Zicheng Jin
Harbin Institute of Technology, No. 92 West Dazhi Street, Nangang District, Harbin, 150001, China

Abstract

Silica aerogel composites have shown strong development in numerous practical insulation applications, the knowledge of their conductive and radiative properties is of primary importance in the process of designing and evaluating the insulation systems. This paper presents an inverse method for predicting the temperature-dependent true thermal conductivity of highly porous silica aerogel composite from measured transient temperature data for temperature from ambient temperature to elevated temperature up to 1100 K and various gas pressures between 0.01 Pa and 100 kPa. It was achieved by combining a forward method solving coupled conductive and radiative heat transfer and an optimization method based on genetic algorithm (GA). The radiative properties used to solve combined conduction and radiation were theoretically predicted from Lorenz-Mie theory. The true thermal conductivities fell within 0.013-0.031 W/(m·K) for the temperature and gas pressure ranges considered, increased nonlinear with increasing gas pressure, and increased almost linear with increasing temperature. The contributions of radiative and conductive heat transfer in silica aerogel composite were predicted form the predicted radiative properties and the retrieved true thermal conductivity, the radiative heat transfer contribution increased with increasing temperature, but decreased as the gas pressure increased. Heat conduction always dominates in the SAC specimen for all gas pressures and specimen temperatures investigated.

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