膨胀石墨/石蜡相变复合材料有效导热系数的数值计算

通过膨胀石墨粉与石蜡混合制备相变复合材料可有效提高该储能材料的传热性能。为研究膨胀石墨/石蜡相变复合材料的导热机制,提出了膨胀石墨粉与石蜡混合后的3尺度层次固体有效导热系数计算方法。然后,通过数值模拟计算得到了具有不同体积分数和不同导热系数的膨胀石墨导热颗粒的膨胀石墨/石蜡相变复合材料的有效导热系数。结果表明:膨胀石墨能够有效地提高石蜡的导热性能,当膨胀石墨的体积分数为10%时,膨胀石墨/石蜡相变复合材料的有效导热系数是纯石蜡的9倍。此外,提高底层尺度的石墨片与石蜡的混合程度及降低底层尺度石墨的体积分数都能有效提高膨胀石墨/石蜡相变复合材料的有效导热系数。所得结论为探究膨胀石墨粉提高相变复合材料导热系数的机理奠定了基础。

Numerical calculation of effective thermal conductivity coefficients of expanded graphite/paraffin phase change composites

Preparing phase change composites by mixing expanded graphite powders and paraffin can improve the heat transfer performance of the energy storage materials effectively. In order to investigate the thermal conductivity mechanism of expanded graphite/paraffin phase change composites, the calculation method of the effective thermal conductivity coefficients of three scales solid after the mixture of expanded graphite powders and paraffin was put forward. Then, by numerically simulation calculation, the effective thermal conductivity coefficients of expanded graphite/paraffin phase change composites containing expanded graphite thermal conductive particles with different volume fractions and different thermal conductivity coefficients were obtained. The results show that expanded graphite can improve the heat conduction performance of paraffin greatly, and when the volume fraction of expanded graphite is 10%, the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composite is as high as 9 times of the pure paraffin. In addition, improving the mixing degree of graphite sheets and paraffin in bottom scale and reducing the volume fraction of the bottom scale graphite both can improve the effective thermal conductivity coefficient of expanded graphite/paraffin phase change composites effectively. The conclusions obtained lay a foundation for the investigation of the mechanisms of expanded graphite powders improving the thermal conductivity coefficients of phase change composites.