空气能蓄冷用相变材料研制及热物性表征

Phase change materials with excellent performance are very important for the application of natural cooling source in building air conditioning. Composite phase change materials CA-LAFe₂O₃/EG was prepared using the CA-LA eutectic acid as phase change materials, nano-Fe₂O₃ as additive, and expanded graphite(EG) as matrix materials by chemical dispersion, ultrasonic oscillation and physical adsorption. The properties of the materials were characterized. The results showed that it was better mixing uniformity with CA-LA when the mass fraction of nano-Fe₂O₃ was 0.8%, which eliminated the supercooling of CA-LA. When the mass fraction of EG was 5.88%, it had a good adsorption on CA-LA Fe₂O₃(0.8%). FTIR spectrum revealed that there was no chemical reaction in CA-LAFe₂O₃/EG. The crystallization process showed that adding nano-Fe₂O₃ particles and EG can accelerate the cooling and crystallization process. The cooling and crystallization time was reduced 39.4% by adding only nano-Fe₂O₃ particles and 78.2% by adding nano-Fe₂O₃ and EG, which was conducive to the cold storage process. DSC results indicated that the enthalpy of CA-LAFe₂O₃(0.8%)/EG (5.88%)/EG was 124.70kJ/kg, which was 3.4% lower than that of pure CA-LA. The oneset melting temperature was 18.66℃ and the oneset crystallization temperature was 19.87℃. Compared with CA-LA the temperature range during melting and crystallization was increased and the thermal conductivity of the material was enhanced. The thermal response of shape stabilized composite phase change materials was affected by the anisotropy of expanded graphite and its thermal response was related to the compression direction. The temperature response speed in the tangential direction of compression was far greater than that in the normal direction. The anisotropy of the materials should be considered in the design of phase change energy storage heat exchangers.