硫酸钠水合盐相变蓄冷材料的制备及性能优化

针对空调系统应用场合，提出一种以十水硫酸钠（sodium sulfate decahydrate，SSD）为主材的相变蓄冷材料新型制备配方，并对材料的各方面性能加以优化。首先采用步冷曲线法确定成核剂比例，消除材料过冷现象，在此基础上研究分析了不同种类、含量的增稠剂聚丙烯酸钠（PAAS）、聚丙烯酰胺（PAM）、羧甲基纤维素（CMC）、聚阴离子纤维素（PAC）、黄原胶（XG）]对材料相分离及相变潜热的影响，接着加入熔点控制剂氯化铵、氯化钾改变十水硫酸钠的相变温度，调配出满足空调温区的相变材料，最后加入膨胀石墨（expanded graphite，EG）进一步改善材料的导热性和稳定性，并进行了热循环测试。结果表明：添加质量分数3%的硼砂对降低材料过冷度效果最佳；添加质量分数1.0%~2.0%的PAAS可以消除材料的相分离现象，且对材料的相变潜热影响较小。SSD-BPA∶EG质量比为93∶7时材料具有较高的导热性和形状稳定性。经优化后复合相变蓄冷材料的相变温度为7.4℃，相变潜热为117.4J/g，热导率为1.876W/(m·K)，经200次循环后材料的相变温度保持稳定，潜热衰减率为14.05%。

Preparation and performance optimization of phase change cold storage materials with sodium sulfate hydrate salt

A new formulation for the preparation of phase change cold storage materials based on sodium sulfate decahydrate (SSD) was proposed for air-conditioning system applications, and all aspects of the material's performance were optimized. The nucleating agent ratio was first determined using the step-cooling curve method to eliminate subcooling of the material. On this basis, the effect of different types and levels of thickening agents sodium polyacrylate (PAAS), polyacrylamide (PAM), carboxymethyl cellulose (CMC), polyanionic cellulose (PAC) and xanthan gum (XG)] on the phase separation and latent heat of phase change of the material was investigated and analyzed. Then, the melting point controller ammonium chloride and potassium chloride were added to change the phase change temperature of sodium sulfate decahydrate, and the phase change material was formulated to meet the air-conditioning temperature zone. Finally, expanded graphite (EG) was added to further improve the thermal conductivity and stability of the material, and the thermal cycling tests were carried out. The experimental results showed that the addition of 3% (mass fraction) borax was the most effective in reducing the subcooling of the material. The addition of 1.0%—2.0% (mass fraction) PAAS could eliminate the phase separation phenomenon of the material and had the less effect on the latent heat of phase change of the material. The material had a high thermal conductivity and shape stability when the mass ratio of SSD-BPA∶EG was 93∶7. The phase change temperature of the optimized composite phase change storage material was 7.4℃, the latent heat of phase change was 117.4J/g and the thermal conductivity was 1.876W/(m·K). The phase change temperature of the material remains stable after 200 cycles and the latent heat decay rate was 14.05%.