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

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