月桂酸-硬脂酸/SiO2复合相变材料的实验研究

相变蓄热技术能够收集太阳能等低品位热源形成稳定的“能量池”,为建筑保温蓄热或末端能量利用提供稳定的热源。本文选取月桂酸和硬脂酸作为基本有机相变材料,采用步冷曲线法测量并绘制了两种材料的二元平衡相图,得到二者最小共熔点混合质量比例是月桂酸为70%,硬脂酸为30%,此时混酸的相变温度为31.2℃,相变潜热为264.3 kJ/kg;为增强相变材料的热稳定性和导热性能,预防或缓解在熔解-凝固热循环中出现的蠕流分层现象,以质量比为70%月桂酸和30%硬脂酸形成的混酸为基本材料,添加具有三维网络结构的SiO2硅溶胶进行复合材料的调制和测试,结果表明,当SiO2在复合材料中所占质量比例为35%时,混酸完全被四面体状的SiO2所包覆固定,形成稳固的相变主体。多次循环实验显示,复合相变材料的相变温度为30.8℃,相变潜热值为104.1 kJ/kg,虽然相变潜热值有所降低,但热稳定性大大增强。

Experimental Study on Composite Phase Change Materials of Lauric Acid- Stearic Acid/Silicon Dioxide

The phase change materials can collect fluctuant solar energy and other low-grade energy to form a stable energy source for building insulation and the terminal equipment of the buildings.In this study,lauric acid and stearic acid were selected as the basic phase change materials.The binary equilibrium phase diagram was completed based on the step cooling curve method according to experimental tests data.The results showed that the phase transition temperature of the mixed acid at the lowest eutectic point was 31.2℃,and the latent heat value was 264.3 kJ/kg when the mixing ratio was 70%for lauric acid and 30%for stearic acid.Secondly,in order to improve the thermal stability and thermal conductivity of the mixed acid,silicon dioxide with a three-dimensional network structure was added to the mixed acid.The experimental results showed that when the proportion of the silicon dioxide in the hybrid materials was 35%,the mixed acid could be completely wrapped up by tetrahedral silica to form a stable phase unit change.Multiple cyclic experiments showed that the phase transition temperature of the hybrid phase change material was 30.8℃and its latent heat value was 104.1 kJ/kg.Although the latent heat decreased,the thermal stability was greatly enhanced.