纯纤维芯材孔隙尺度确定法对气相热导率影响

Influence of Pore Size Determination Methods of Pure Fiber Core Material on Gas-phase Thermal Conductivity

总结相关文献对纯纤维芯材(真空绝热板芯材)孔隙尺度确定方法(分别定义为文献法1、文献法2、文献法3),提出一种新的孔隙尺度确定方法(定义为新方法)。采用控制变量法(变量选取空气温度、空气压力、纤维直径、纤维在纯纤维芯材中的体积分数),分析孔隙尺度确定方法对气相热导率计算结果的影响。在空气温度、空气绝对压力、纤维直径、纤维在纯纤维芯材中的体积分数(以下简称纤维体积分数)分别为300 K、10 Pa、6μm、15%时,由4种孔隙尺度确定方法(文献法1、文献法2、文献法3、新方法)计算的气相热导率分别为5. 1×10^(-5)、4. 9×10^(-5)、26. 6×10^(-5)、9. 1×10^(-5)W/(m·K)。在相同设定条件下,由新方法计算得到的气相热导率适中,认为这种确定孔隙尺度的方法可信。在其他设定条件不变的前提下:由不同方法计算的气相热导率均随空气温度(变化范围为253～323 K)的升高而下降。由不同方法计算的气相热导率随空气压力(变化范围为0. 1 Pa～100 kPa)的变化趋势均基本一致,在空气压力较低的情况下,气相热导率基本保持不变,随着压力升高,气相热导率急剧升高,且最终趋于相等。由不同方法计算的气相热导率均随纤维体积分数(变化范围为0. 01～0. 40)的增大而降低。由不同方法计算的气相热导率均随纤维直径(变化范围为2～24μm)的增大而增大。

The methods for determining the pore size of pure fiber core material in the related literatures （defined as literature method 1,literature method 2 and literature method 3 respectively） are summarized. A new method for determining the pore size （defined as the new method） is proposed. The influence of pore size determination methods on the calculation result of gas-phase thermal conductivity is analyzed by the control variable method （variables are air temperature,air pressure,fiber diameter and the volume fraction of fiber in pure fiber core）. When the air temperature,air pressure,fiber diameter and the volume fraction of fiber in pure fiber core （hereinafter referred to as fiber volume fraction） are 300 K,10 Pa,6 μm and 15% respectively,the gas-phase thermal conductivities calculated by 4 kinds of methods （literature method 1,literature method 2,literature method 3 and new method） are 5.1×10 -5 ,4.9×10 -5 ,26.6×10 -5 and 9.1×10 -5 W/（m -1 ·K -1 ） respectively. Under the same setting conditions,the gas-phase thermal conductivity calculated by the new method is moderate,and it is believed that this method for determining the pore size is credible. Under the premise that other setting conditions are unchanged,the gas-phase thermal conductivities calculated by different methods decrease with the increase of air temperature （the variation range is 253 to 323 K）,and the variation trends of gas-phase thermal conductivities calculated by different methods with the air pressure （the variation range is 0.1 Pa to 100 kPa） are basically the same. In the case of low air pressure,the gas-phase thermal conductivity basically remains unchanged,and as the pressure increases,the gas-phase thermal conductivity rises sharply and eventually tends to be equal. The gas-phase thermal conductivities calculated by different methods decrease with the increase of the fiber volume fraction （the variation range is 0.01 to 0.40）. The gas-phase thermal conductivities calculated by different methods increase with the increase of the fiber diameter （the variation range is 2 to 24 μm）.