Study on paraffin modifying inorganic composite phase change heat storage system
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摘要: 水合盐相变储热材料普遍存在的过冷和相分离现象是影响其热稳定性和热性能的关键问题。以中低温水合盐相变储热材料MgCl2∙6H2O(MCH)和MgSO4∙7H2O(MSH)为研究对象,以活性炭(ACC)为添加剂,采用熔融共混法制备了MCH-MSH-ACC混合体系,并以石蜡(PA)为调节剂,制备了MCH-MSH-ACC/PA复合材料相变体系。研究了PA对复合相变体系的相变焓、相变温度、过冷度及相分离的影响。结果表明:微量PA的添加有助于提升MSH-MCH-ACC/PA体系的相变储热性能,和其他PA含量体系相比较,PA含量为0.5wt%的体系在储热阶段所需时间最短,而放热阶段持续时间最长,其初始相变焓值可达到321.75 kJ/kg,循环试验后相变焓稳定在310.25 kJ/kg。所制备的新型共混MSH-MCH-3wt%ACC/0.5wt%PA复合相变体系具有良好的储热性能和循环稳定性能。Abstract: The supercooling and phase separation of hydrated salt phase change heat storage materials are two key issues which affect its thermal stability and thermal performance. MgCl2∙6H2O (MCH) and MgSO4∙7H2O (MSH) are used as the research materials, which are the phase change heat storage materials at moderate and low tempera-tures, and activated carbon (ACC) is used as the additive, The MCH-MSH-ACC composite phase change system was prepared by the melt blending method, then, the MCH-MSH-ACC/PA composite phase change system is prepared with paraffin (PA) as the modifier. The effects of PA on the phase change enthalpy, phase change temperature, subcooling degree and phase separation phenomenon of the composite phase change materials were studied. The re-sults show that the addition of trace PA is beneficial to improve the phase change heat storage performance of the MSH-MCH-ACC/PA system. Compared with other PA content systems, the system with 0.5wt% PA perform the shortest time in the heat storage stage and the maximum heat release time in the exothermic phase, whose initial phase change enthalpy value reach 321.75 kJ/kg, and the stable enthalpy is 310.25 kJ/kg after the cycle tests. The prepared new blend MSH-MCH-3wt%ACC/0.5wt%PA composite material has good heat storage property and good thermal cycle stability.
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Key words:
- composite material /
- heat storage property /
- subcooling degree /
- thermal cycle stability /
- paraffin
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表 1 不同ACC浓度下MCH-MSH-ACC系统的过冷度数值
Table 1. Subcooling value of the MCH-MSH-ACC system under different ACC concentrations
Sample Undercooling/℃ MCH-MSH 6.63 MCH-MSH-1wt%ACC 4.74 MCH-MSH-2wt%ACC 1.12 MCH-MSH-3wt%ACC 0 MCH-MSH-4wt%ACC 0 表 2 不同PA含量的MCH-MSH-ACC/PA复合材料的相变特性
Table 2. Phase change properties of MCH-MSH-ACC/PA composite PCMs with different PA contents
Condition Sample Onset temperature
Tm/℃Peak temperature
Tp/℃End temperature
Te/℃Before cycle MCH-MSH-ACC 88.87 97.82 115.98 MCH-MSH-ACC/0.5wt%PA 82.16 91.78 111.96 MCH-MSH-ACC/1.0wt%PA 85.30 93.29 115.31 MCH-MSH-ACC/1.5wt%PA 93.11 100.69 117.33 MCH-MSH-ACC/2.0wt%PA 92.07 101.03 119.82 After cycle MCH-MSH-ACC 98.46 109.77 117.14 MCH-MSH-ACC/0.5wt%PA 83.62 93.15 111.70 MCH-MSH-ACC/1.0wt%PA 96.12 105.17 115.21 MCH-MSH-ACC/1.5wt%PA 98.83 107.17 114.30 MCH-MSH-ACC/2.0wt%PA 101.36 108.01 115.11 -
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