Abstract:

Electric thermostatic water bath and high-low temperature alternating test chamber were used to build a heat storage and release platform. Influence of 9 thickeners on the heat storage and release performance of NH₄Al(SO₄)₂·12H₂O was researched and the cycle stability of the modified NH₄Al(SO₄)₂·12H₂O was tested and analyzed. The results showed that the heat release performance of NH₄Al(SO₄)₂·12H₂O with addition of 2% xanthan gum, 1% guar gum or 1% hydroxyethylcellulose was improved respectively, and the reduction of latent heat was not significant. Under these three addition ratios, the melting point of NH₄Al(SO₄)₂·12H₂O was decreased by 1.0℃, 1.3℃, 1.3℃, respectively,the time of heat storage was increased by 94%, 35%, 9%, respectively, the time of phase change of heat storage was increased by 125%, 63%, 5%, respectively, the undercooling was decreased by 43%, 45%, 34%, respectively, the temperature variation during crystallization process was decreased by 84%, 87%, 73%, respectively, the time of heat release was increased by 27%, 11%, 50%, respectively, and the latent heat was decreased by 5.8%, 8.3%, 4.1%, respectively. The modification effect of thickener on the heat release performance of NH₄Al(SO₄)₂·12H₂O was affected by the degradation reaction, while the modification effect of 2% xanthan gum was better than the other two thickeners since the temperature variation during crystallization process of corresponding modified NH₄Al(SO₄)₂·12H₂O was always maintained above 60℃. After 60 cycles, compared with pure NH₄Al(SO₄)₂·12H₂O, the main parameters of modified NH₄Al(SO₄)₂·12H₂O changed as follows: the melting point was decreased by 0.2℃, the time of phase change of heat storage was decreased by 15%, the time of heat storage was increased by 13%, the temperature variation during crystallization process was decreased by 87%, the undercooling was decreased by 42%, the time of heat release was increased by 36%, and the latent heat was decreased by 1.6%.

Key words: phase change, undercooling, heat storage, heat release, crystallization

摘要：

利用电热恒温水槽、高低温交变试验箱搭建蓄放热实验平台，研究了9种增稠剂对NH₄Al(SO₄)₂·12H₂O蓄放热性能的影响，测试分析了NH₄Al(SO₄)₂·12H₂O改性后的循环稳定性能。结果表明，质量分数为2%的黄原胶、1%的瓜尔豆胶或1%的羟乙基纤维素均能较好改善NH₄Al(SO₄)₂·12H₂O的放热性能且对相变潜热的削弱程度不大，对应改性NH₄Al(SO₄)₂·12H₂O的主要参数变化为：熔点分别降低1.0℃、1.3℃、1.3℃，蓄热时长分别增加94%、35%、9%，蓄热相变平台分别增加125%、63%、5%，过冷度分别减小43%、45%、34%，结晶过程温度变化分别减小84%、87%、73%，放热时长分别增加27%、11%、50%，相变潜热分别减小5.8%、8.3%、4.1%。增稠剂对NH₄Al(SO₄)₂·12H₂O放热性能的改性效果会受到降解反应影响，而2%黄原胶的改性效果相对其他两种增稠剂较好，循环过程中改性材料的结晶过程温度始终保持在60℃以上。60次循环后，改性材料主要参数相比纯材料的变化为：熔点下降0.2℃，蓄热相变平台减小15%，蓄热时长增加13%，结晶过程温度变化减小87%，过冷度减小42%，放热时长增加36%，相变潜热减小1.6%。

关键词: 相变, 过冷度, 蓄热, 放热, 结晶