Latent heat storage units utilizing stable supercooling of sodium acetate trihydrate (SAT) composites were tested in a laboratory. The stainless steel units were 1.5 m high cylinders with internal heat exchangers of tubes with fins. One unit was tested with 116 kg SAT with 6% extra water. Another unit was tested with 116.3 kg SAT with 0.5% Xanthan rubber as a thickening agent and 4.4% graphite powder. The heat exchange capacity rate during charge was significantly lower for the unit with SAT and Xanthan rubber compared to the unit with SAT and extra water. This was due to less convection in the thickened phase change material after melting. The heat content in the fully charged state and the heat released after solidification of the supercooled SAT mixtures at ambient temperature was higher for the unit with the thickened SAT mixture. The heat discharged after solidification of the supercooled SAT with extra water decreased over repeating charge and discharge cycles while the heat discharged from the SAT with Xanthan rubber remained stable. In both units, the solidification started spontaneously in the majority of the test cycles. This was due to the design of the unit or the method for handling the expansion and contraction of the SAT during charge and discharge.
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机译:利用三水合醋酸钠(SAT)复合材料稳定过冷的潜热存储单元在实验室中进行了测试。不锈钢单元为1.5 m高的圆柱体,带有带翅片管的内部热交换器。用116 kg SAT和6%的额外水测试了一个单元。使用116.3 kg SAT和0.5%的黄原胶作为增稠剂以及4.4%的石墨粉测试了另一个单元。与装有SAT和多余水的装置相比,装有SAT和黄原胶的装置在装料过程中的热交换容量率要低得多。这是由于熔融后增稠的相变材料中的对流较少。对于带有增稠SAT混合物的单元,在完全充电状态下的热量和过冷SAT混合物在环境温度下固化后释放的热量更高。在重复充电和放电循环后,过冷的SAT与多余的水固化后释放的热量降低,而用黄原胶从SAT释放的热量保持稳定。在这两个单元中,固化在大多数测试周期中都是自发开始的。这是由于设备的设计或在充放电期间处理SAT膨胀和收缩的方法所致。
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