繊維質断熱材の熱伝導率の推算

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  • Prediction of Thermal Conductivity of Ceramic Fibrous Insulator
  • センイシツ ダンネツザイ ノ ネツ デンドウリツ ノ スイサン

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The thermal conductivity of alumino-silicate fibrous insulators with various bulk densities was measured by the transient hot wire method under various reduced pressures in order to propose a simple equation for predicting their thermal conductivities. The results obtained were summarized as follows:<br>(1) The thermal conductivity of ceramic fibrous insulators with various bulk densities decreased gradually with decreasing pressure ranging from 760 to 10mmHg and converged to an extremely low constant value under 10-2mmHg after a sharp decrease between 10 and 10-1mmHg, due to the pressure dependence of thermal conductivity of air. Their thermal conductivity increased with increasing bulk density all over the pressure range covered in the thermal conductivity measurement.<br>(2) The thermal conductivity of ceramic fibrous insulators in helium, oxygen and freon-12 gas atmospheres also increased with an increase in bulk density, and their thermal conductivity in a gas atmosphere having high thermal conductivity such as helium was higher than those in gases with lower thermal conductivity such as freon-12.<br>(3) In alumino-silicate fibrous insulators, the following experimental relation among λ (thermal conductivity of insulator), λs (that of fiber: 1.07W/m·K), λf (that of gas being filled between fibers) and φ (volume fraction of fiber) was obtained.<br>λ=aλs+bλf+(1-a-b)λsλf/(1-y)λs+yλf<br>a=0.169φ1.57<br>b=(1-φ)1.16<br>y=0.81-0.043lnφ<br>This equation enabled us to calculate the thermal conductivity of the fibrous insulators in various gas atmospheres (-0.2W/m·K) at room temperature within the error of about ±10%.

収録刊行物

  • 窯業協會誌

    窯業協會誌 95 (1105), 893-898, 1987

    公益社団法人 日本セラミックス協会

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