Abstract:

One of the greatest challenges in the application of organic phase change materials (PCMs) is to increase their thermal conductivity while maintaining high phase change enthalpy. To prepare nano-organic composite PCMs for air-conditioning cool storage, nanomaterials with high thermal conductivity, including multi-walled carbon nano-tubes (MWNTs), Al₂O₃ and Fe₂O₃, were respectively added into the organic composite PCMs of caprylic acid/myristyl alcohol (with mass ratio of 73.7 to 26.3), developed previously in this study. The thermal properties of nano-organic composite PCMs were analyzed by measuring their thermal conductivity coefficient. The kinds and concentrations of nano-materials are key influencing factors. The experiments showed that heat conductivities increased obviously when mass fractions of MWNTs, Al₂O₃ and Fe₂O₃ nanomaterials were less than 0.3%, 0.4% and 0.8%, respectively. Compared with the original PCMs, heat conductivity increased by 26.3% when mass fraction of MWNTs was 0.3%; heat conductivity increased by 13.1% when mass fraction of Al₂O₃ was 0.4%; the heat conductivity increased by 32.1% when mass fraction of Fe₂O₃ was 0.8%. The thermal conductivity enhancement effects were in the order of Fe₂O₃, MWNTs and Al₂O₃ at a specific mass fraction (e.g., 0.7%) of nanomaterials. The nano-organic composite PCMs prepared had a limited influence on phase change temperature and phase change enthalpy of the original PCMs, fluctuation of phase change temperature was less than 0.4℃, and the greatest fluctuation range of phase change enthalpy was 1.4%.

Key words: organic phase change materials, cool storage in air-conditioning, nanomaterials, thermal properties, heat transfer enhancement, heat conduction, preparation

摘要：

针对目前空调用有机相变蓄冷材料热导率低的问题,将具有高导热性的纳米材料(MWNTs、Al₂O₃、Fe₂O₃)添加到所开发制备的二元复合有机蓄冷材料(质量比73.7:26.3的辛酸/肉豆蔻醇)中,从纳米材料的种类和浓度两方面,研究其对复合有机蓄冷材料热物性的影响。实验发现:对于MWNTs、Al₂O₃、Fe₂O₃ 3种纳米材料,当其质量分数分别小于0.3%、0.4%、0.8%时,对应纳米复合材料热导率随纳米材料浓度的增加幅度较为明显;与原二元复合有机相变蓄冷材料相比,添加0.3%的MWNTs,热导率提高26.3%;添加0.4%的Al₂O₃,热导率提高13.1%;添加0.8%的Fe₂O₃,热导率提高32.1%;当在一定纳米材料质量分数(如0.7%)下,加入纳米颗粒的复合材料导热性能效果依次为Fe₂O₃>MWNTs>Al₂O₃。不同纳米粒子的添加对原蓄冷材料的相变温度和相变潜热影响很小,相变温度变化波动最大为0.4℃,相变潜热变化波动范围最大为1.4%。

关键词: 有机相变材料, 空调蓄冷, 纳米材料, 热物性, 强化传热, 热传导, 制备