Na2HPO4?12H2O相变储能复合材料制备及热物性

十二水磷酸氢二钠的过冷度、相分离以及热导率低等问题影响了其在低温蓄热场合的应用，因此需要对其进行相关的改性研究。本文通过成核剂和增稠剂的筛选实验及添加导热增强剂纳米氧化铁（α-Fe₂O₃），制备了质量分数为Na₂HPO₄·12H₂O+2% Na₄P₂O₇·10H₂O+1%黄原胶（GX）+0.2%α-Fe₂O₃复合相变储能材料，并对其进行了凝固放热测试、热物性测试及循环稳定性测试。结果表明：2%的Na₄P₂O₇·10H₂O抑制过冷效果最好，成核效果不随循环次数的增加而减小，过冷度维持在2℃左右；GX可以有效抑制Na₂HPO₄·12H₂O的相分离现象，且质量分数为0.75%～1.25%是较合适的剂量；α-Fe₂O₃可以有效地提高Na₂HPO₄·12H₂O的热导率，添加0.2%α-Fe₂O₃使热导率提高了90.8%；循环150次后，复合相变储能材料的相变潜热值为252J/g，相比于循环前衰减了7.4%，相变温度为35.4℃，过冷度为1.3℃，热导率为2.054W/(m·K)，相比纯材料提高了100.2%。改性后的复合相变储能材料相变温度适宜，潜热值大，热导率高，热性能稳定，可推广应用到热泵蓄热、温室生产和电子器件散热等领域。

Preparation and thermal properties of Na2HPO4·12H2O composite phase change material for thermal energy storage

Disodium hydrogen phosphate(Na₂HPO₄·12H₂O) had some problems such as supercooling, phase separation and low thermal conductivity affecting its applications in the low temperature thermal storage. Therefore, it needs to be further improved. By means of the selecting experiment of nucleating agent and thickening agent and adding thermal conductive enhancer nano-iron oxide(α-Fe₂O₃), composite phase change energy storage materials with mass ratio of Na₂HPO₄·12H₂O+2% Na₄P₂O₇·10H₂O+1% xanthan gum(GX)+0.2% α-Fe₂O₃ were prepared，and the solidification exothermic test, thermophysical properties test and cycling stability test were carried out. The results showed that the nucleating effect of adding 2% Na₄P₂O₇·10H₂O was the best and did not decrease with the increase of cycle times, and the degree of supercooling was maintained at about 2℃. GX can effectively control the phase separation of Na₂HPO₄·12H₂O, for which mass ratio of 0.75%～1.25% was much better. α-Fe₂O₃ can effectively improve the thermal conductivity of Na₂HPO₄·12H₂O, and mass ratio of 0.2% can increase by 90.8%. The latent heat of composite phase change energy storage materials was 252J/g after 150 cycles, which decreased by 7.4%. The phase change temperature was 35.4℃, while the supercooling was 1.3℃.The thermal conductivity was 2.054W/(m·K), which was 100.2% higher than that of pure materials. The modified composite materials with the suitable phase change temperature, high latent heat, high thermal conductivity and stable thermal performance can be widely used in heat pump storage, greenhouse production and heat dissipation of electronic devices.