摘要:
五水硫代硫酸钠（Na2S2O3·5H2O）相变储能材料具有较高的相变潜热、储能密度等，但Na2S2O3·5H2O存在过冷和相分离，性能较不稳定。添加成核剂K2SO4、CaSO4·2H2O、Na4P2O7·10H2O和强化传热材料膨胀石墨（EG）进行改性，制备得到性能稳定的EG/Na2S2O3·5H2O相变储能复合材料。测试结果显示：K2SO4对Na2S2O3·5H2O的成核性较差，CaSO4·2H2O、Na4P2O7·10H2O均有较好的成核作用，可明显降低Na2S2O3·5H2O过冷度，但CaSO4·2H2O体系不稳定，添加3.0%质量分数的Na4P2O7·10H2O可使Na2S2O3·5H2O过冷度降低至1℃以内，0.5%~2.0%质量分数的EG可使其过冷度降低至2℃左右，7.0%质量分数的EG可完全消除体系的相分离。复合相变材料的较优组成为7.0%的EG、3.0%的Na4P2O7·10H2O和90.0%的Na2S2O3·5H2O。此时，EG/Na4P2O7·10H2O/Na2S2O3·5H2O复合材料相变潜热为192.5 kJ·kg-1，相变时无液态泄露，无相分离，储热时间比纯物质缩短22.3%，放热较快。
Abstract:
Sodium thiosulfate pentahydrate(Na2S2O3·5H2O) phase change energy storage material has high phase change latent heat, energy storage density, etc. However, Na2S2O3·5H2O has undercooling and phase separation, the performance is unstable. Adding the nucleating agent K2SO4, CaSO4·2H2O, Na4P2O7·10H2O and enhance heat transfer material expanded graphite(EG) could improve the performance, EG/Na2S2O3·5H2O phase change energy storage composite with stable properties was prepared. Test results show that the nucleation performance of K2SO4 for Na2S2O3·5H2O is worse, both CaSO4·2H2O and Na4P2O7·10H2O have better nucleation performance, which could significantly reduce the undercooling degree of Na2S2O3·5H2O. However, the CaSO4·2H2O system is unstable, adding the mass fraction 3.0% of Na4P2O7·10H2O could reduce the undercooling degree of Na2S2O3·5H2O to within 1℃, adding mass fraction 0.5%-2.0% of EG could reduce the undercooling degree to about 2℃, and mass fraction 7% of EG can completely eliminate phase separation of the system. Therefore, the optimal composition for phase change materials is 7.0% of EG, 3.0% of Na4P2O7·10H2O, and 90.0% of Na2S2O3·5H2O. The latent heat of EG/Na4P2O7·10H2O/Na2S2O3·5H2O composite is 192.5 kJ·kg-1. No liquid leakage and no phase separation when the phase transition. The thermal storage time is shorter 22.3% than pure substance, and heat release faster.
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