Experiment and Inverse Analysis to Estimate SiO₂ Aerogel Composite’s Thermophysical Properties by the Surface’s Temperature Response

Abstract

SiO₂ aerogel is a sort of nano-particles&pores porous medium possessed of excellent thermal insulation performance which is worth excavating related parameters. Based on simple experiments and simplified heat transfer equations, as many parameters as possible can be deduced under limited conditions. In this paper, the hot surface’s temperature response of SiO₂ aerogel composites with different components of fiber and opacifier are measured by experiment, and the thermal conductivity, λ, and thermal effusivity, $\sqrt {\lambda \rho c_{{\text{p}}} }$, are λ = 0.0270–0.0386 W·m⁻¹·K⁻¹ and $\sqrt {\lambda \rho c_{{\text{p}}} }$= 75.933–113.185 J·m⁻²·K·s^−0.5 at T_cold = 298 K & ΔT < 15 K, respectively. Through the inverse analysis of the Levenberg–Marquardt method, the λ, specific heat capacity, c_p, and thermal diffusivity, a, can be estimated by analyzing the above hot surface’s temperature response, which is λ = 0.0284–0.0391 W·m⁻¹·K⁻¹, c_p = 761.7–2237.3 J·kg⁻¹·K⁻¹, a = 5.575–13.570 × 10^–8 m²·s⁻¹, respectively, where the maximum deviation is no more than 6.11 %. Sensitivity coefficients of λ and c_p co-influence initial unsteady-state while λ dominates heat transfer after that. Micron SiC and SiO₂ hollow spheres inside SiO₂ aerogel will inhibit the the thermal radiation and improved the insulation performance at large ΔT.