Enable thermal insulation improvement of Al2O3 aerogels doped with graded oriented extinction phase-change fiber at large temperature differences

Abstract

Phase change materials (PCMs) play essential roles in extending transient thermal insulation in the aerospace field; however, the extinction properties variations during the phase change process have seldom been investigated. The present study presents an extinction phase-change fiber (EPCF) design, i.e., composed of extinction material shell as well as the PCM core and dispersed in Al2O3 aerogel. The extinction performance (especially after the phase transition) and the insulation performances at steady and transient states according to specific infrared radiation wavelength modulation are numerically investigated. This study reveals that the extinction characteristic of VO2@SiO2 is superior to that of SiO2 and TiO2 fiber. The extinction performance is improved by ∼8.37% after the phase transition of VO2. Besides, the time constant of VO2@SiO2 increased by ∼2.17 times the pure aerogel at the insulation aspect. Similar conclusions could be self-evidently found in some other EPCFs; furthermore, multi-layer EPCFs design is studied for spectral modulation principle combined with the transient heat transfer characteristic. Our developmental work could inspire some novel ideas on insulation material design in the future and improve the understanding of phase change insulation.