硬脂酸/膨胀石墨复合相变储热的动力学研究

采用真空吸附法制备硬脂酸(SA)/膨胀石墨(EG)复合相变储热材料,利用差示量热扫描法(DSC)研究SA及SA/EG复合材料的非等温熔化和结晶过程动力学。运用Kissinger和Ozawa两种动力学数据处理方法对样品的非等温熔化DSC曲线进行处理,应用Mo法分析各样品的非等温结晶动力学特性。结果表明:SA/EG复合材料具有储热密度大、导热系数高且相变过程中无液相物质泄漏的优点;EG多孔结构的物理吸附作用会阻碍SA分子链段的扩散,使其熔化过程中的表观活化能升高;但EG的异相成核和传热强化作用能促进SA的相变,有利于降低其过冷度,提高其相变速率。

Kinetics Study of Phase Change on Stearic Acid/Expanded Graphite Composite as Heat Storage Material

Using the method of vacuum infiltration,the porous structure expanded graphite(EG) serving as conductive filler was combined with stearic acid(SA) to obtain the SA/EG composite phase change material.The non-isothermal fusion and crystallization kinetics of SA and SA/EG composite were studied by means of DSC.Kissinger and Ozawa methods were employed to calculate the DSC curve of non-isothermal fusion,and the Mo method was utilized on analysing the non-isothermal crystallization kinetics of all the samples.Results showed that the SA/EG composite possesses high thermal storage density and thermal conductivity as well as the available form-stable performance.The diffusion of SA molecular link segments were inhibited by EG with porous structure,which resulted in the increase of non-isothermal fusion activation energy.The phase transition of SA was promoted by the EG additive which functioned as a kind of heterogeneous nucleation centers during the non-isothermal crystallization process.Consequently,the super-cooling degree of SA was decreased,and the phase transition rate of SA was increased.