Thermal property in phase-change units and improvement for supercoiling of sodium acetate trihydrate

doi:10.11949/j.issn.0438-1157.20161393

Abstract

Abstract:

Taking sodium acetate trihydrate (CH₃COONa·3H₂O)as basic material for heat storage,this paper reports that the use of nucleating agents, vibration, and mixing can be as several ways to improve the supercooling properties of CH₃COONa·3H₂O.Melting-freezing experiments were made in units made of stainless steel, which is used to imitate the heat accumulators in daily life.By cooling curve and DSC test, the change of supercooling and ability to store heat were investigated.As a result, when an optimal amount of Na₂HPO₄·12H₂O and SiO₂ were added to CH₃COONa·3H₂O, the degree of supercooling was low to approximately 2-3℃ or blow 2.5℃.After introducing ultrasonic vibratory, the degree of supercooling can be as low as 0.7℃.What's more, after stirring the melt for 15 min, the degree of supercooling would be under 2℃, and releasing heat for a long time.At the same time, the last two ways, i.e.,ultrasonic vibratory and stirring can solve the problem of phase separation.At last, this paper analyzes the merits and demerits of above methods for nucleating.In order to improve supercooling in practical application and research, it is suitable to choose a best method according to the size of accumulators and economy.

Key words: phase change, sodium acetate trihydrate, nucleation, silica, vibration, stirring

摘要：

以三水合乙酸钠（CH₃COONa·3H₂O）为储热基料，研究了改善其过冷度的几种措施——添加剂、振动法、搅拌法对于其成核过程的影响。以不锈钢单元体模拟日常生活中的蓄热器，进行融化-凝固实验。绘制步冷曲线以及DSC测试，观察其过冷度及蓄、放热特性的变化。结果发现，成核剂Na₂HPO₄·12H₂O以及纳米成核剂SiO₂分别将过冷度降至2~3℃以及2.5℃以下。超声振动作用使得CH₃COONa·3H₂O的过冷度仅为0.7℃左右。引入15 min机械搅拌作用，过冷度降到了2℃以下，并且放热平台持续时间较长。超声振动和机械搅拌的作用还会有效解决CH₃COONa·3H₂O的相分离现象，同时也保持了较高的蓄热能力。最后，对比分析了各种成核手段的优缺点，在实际应用或者研究中应根据蓄热器的尺寸、经济性等选择合适的办法改善过冷度。

关键词: 相变, 三水合乙酸钠, 成核, 二氧化硅, 振动法, 搅拌法

CLC Number:

TK02

CUI Wenlong, YUAN Yanping, SUN Liangliang, CAO Xiaoling, XIANG Bo. Thermal property in phase-change units and improvement for supercoiling of sodium acetate trihydrate[J]. CIESC Journal, 2016, 67(S2): 149-158.

崔文龙, 袁艳平, 孙亮亮, 曹晓玲, 向波. 三水合乙酸钠在相变单元的传热特性及其过冷度改善[J]. 化工学报, 2016, 67(S2): 149-158.

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