年間 18 号発行
ISSN 印刷: 1064-2285
ISSN オンライン: 2162-6561
Indexed in
MICROSCALE NATURAL CONVECTION IN FIBROUS INSULATION
要約
Fibrous thermal insulation materials are vastly employed in the system of thermal protection of recoverable space vehicles. The accurate determination of their apparent thermal conductivity allows for an adequate sizing of the thermal protection system (TPS) of space vehicles, with effects on the weight, structural strength, manufacture, and launching costs. This property is strongly dependent on the pressure of the gas within the porous and current models for estimating the thermal conductivity in rarefied gases within fibrous thermal insulation at various pressures that present some increasing discrepancy as the pressure rises. The objective of this work is to improve the accuracy of a well-established model for estimating the equivalent thermal conductivity of fibrous insulation materials filled with gas at various pressures. After a sensitivity analysis of every term in the current model, some modifications are tested and proposed. A microscale convection term is modeled and included in the modified model. The results of both versions of the model are compared with experimental data for an alumina foam fibrous insulation and with the modified version presenting better agreement than the original model at higher pressures. The model was also tested in a compact alumina fibrous insulation, and the results showed that in this case the benefits are discreet when compared to the foam.