关键词: 复合相变材料, 相变储能, 十水硫酸钠, 十二水磷酸氢二钠, 碳纳米纤维, 相变行为, 潜热容量, 导热系数

Abstract: For the purpose of rapid and effective heat exchange between phase change materials and the external environment, carbon nanofibers (CNFs) were introduced to improve the thermal conductivity of composite phase change materials. In this paper, Na₂SO₄·10H₂O and Na₂HPO₄·12H₂O were prepared into eutectic salt phase change materials by melt blending method, three-dimensional polymer network encapsulation phase change materials were constructed with sodium polyacrylate, and CNFs were used to improve the thermal conductivity of the composites. The changes of oxygen functional groups on the surface of CNFs treated by high energy ball milling and wet chemical oxidation were investigated by Raman and XPS; the effects of CNFs on the chemical compatibility, phase transition behavior, thermal stability, latent heat capacity and thermal conductivity of the composites were analyzed by Raman, DSC, Hot disk and TG. The results show that after functionalization of CNFs, the atomic ratio of oxygen and carbon increases to 0.140, and the oxidation effect is remarkable. The introduction of CNFs into composite phase change materials has good chemical compatibility among the components in the system. When the addition amount of CNFs reaches 3% (mass fraction), the solid thermal conductivity of the composites reaches 1.05 W/(m·K), and the liquid thermal conductivity is 0.88 W/(m·K). Compared with the composites without CNFs, the solid-liquid thermal conductivity increases by 69.4% and 60.0%, respectively. After 1 000 cycles, the melting enthalpy of the composite decreases by 56.2% and the crystallization enthalpy decreases by 65.3% compared with that before cycles. The phase change system still has a certain heat storage capacity, indicating that embedding phase change materials into three-dimensional network structure is an effective packaging strategy.

Key words: composite phase change material, phase change energy storage, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, carbon nanofiber, phase transition behavior, latent heat capacity, thermal conductivity