八水合氢氧化钡复合相变材料的制备及热力学性能研究
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摘要
采用两步法制备了八水合氢氧化钡/碳酸钡/纳米铁复合相变蓄热体系。八水合氢氧化钡是一种质量储热密度较大的低温相变材料,其熔点温度为78℃,相变潜热为264kJ/kg,但其在相变过程中存在过冷且导热性能差的问题。通过在八水合氢氧化钡中添加碳酸钡为成核剂,纳米铁粉作为添加剂改善其热力学性能。实验结果表明,复合蓄热体系添加质量分数为1.0%的碳酸钡和0.2%的纳米铁时效果最优。通过DSC测试以及导热系数测量,其相变潜热为276.4J/g,导热系数为1.368 W/(m·K),比八水合氢氧化钡溶液上升11.7%。添加BaCO3后,过冷问题得到有效解决,也没有出现化学降解问题。
Barium hydroxide octahydrate/barium carbonate/nano iron composite phase change heat storage system was prepared by a two-step method.Barium hydroxide octahydrate possesses a larger mass heat storage capacity among low temperature phase change materials.Its latent heat is 264kJ/kg,and its melting temperature is 78 ℃.It had a serious super-cooling degree and poor thermal conductivity during its phase change period.Barium hydroxide octahydrate was used as a phase change material,barium carbonate was used as a nucleating agent,and nano-iron was added to improve the thermal conductivity in the composite heat storage system.Results showed that optimal performance was obtained when the mass ratio of barium carbonate and nano-iron was 1.0% and 0.2%.Thermal performance of the composites was investigated by a differential scanning calorimetry and a thermal constant analyzer.The results showed that the latent heat of the composites was 276.4J/g.The thermal conductivity of the composites was1.368 W/(m·K),increased by 11.7% compared with pure barium hydroxide octahydrate.The results also showed that the problem of super-cooling was effectively improved by adding barium carbonate and chemical degradation of composites didn′t occur.
Barium hydroxide octahydrate/barium carbonate/nano iron composite phase change heat storage system was prepared by a two-step method.Barium hydroxide octahydrate possesses a larger mass heat storage capacity among low temperature phase change materials.Its latent heat is 264kJ/kg,and its melting temperature is 78 ℃.It had a serious super-cooling degree and poor thermal conductivity during its phase change period.Barium hydroxide octahydrate was used as a phase change material,barium carbonate was used as a nucleating agent,and nano-iron was added to improve the thermal conductivity in the composite heat storage system.Results showed that optimal performance was obtained when the mass ratio of barium carbonate and nano-iron was 1.0% and 0.2%.Thermal performance of the composites was investigated by a differential scanning calorimetry and a thermal constant analyzer.The results showed that the latent heat of the composites was 276.4J/g.The thermal conductivity of the composites was1.368 W/(m·K),increased by 11.7% compared with pure barium hydroxide octahydrate.The results also showed that the problem of super-cooling was effectively improved by adding barium carbonate and chemical degradation of composites didn′t occur.
引文
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2 方贵银.蓄能空调技术[M].北京:机械工业出版社,2006:146
3 Pielichowska K,Pielichowski K.Phase change materials for thermal energy storage[J].Prog Mater Sci,2014,65(10):67
4 宋纤纤,陈仕国,刘泽华,等.复合相变建筑材料的研究与应用[J].江苏建材,2011(3):16
5 刘中良,马重芳,孙旋.相变潜热随温度变化对固-液相变过程的影响[J].太阳能学报,2003,24(1):53
6 聂光华,李耀华,张志英.九水合硝酸铝和八水合氢氧化钡导热系数的实验研究[J].能源研究与信息,2004,20(1):46
7 盛强,邢玉明,罗恒.八水氢氧化钡相变材料储热性能实验[J].北京航空航天大学学报,2014,40(5):635
8 章学来,王为,李志伟,等.一种相变蓄热材料及其蓄热热回收的实验研究[J].制冷技术,2014,32(2):15
9 高淳,王国华,张天时,等.汽车余热利用蓄能材料及其释热特性试验研究[J].汽车技术,2011(8):38
10 石海民,梁德青,李栋梁,等.CH3COONa·3H2O相变蓄热性能研究[J].制冷学报,2009,30(2):8
11 李晶.相变蓄热材料及其相变特性的研究[D].北京:北京工业大学,2005
12 Zhong L,Zhang X,Luan Y,et al.Preparation and thermal properties of porous heterogeneous composite phase change materials based on molten salts/expanded graphite[J].Solar Energy,2014,107:63
13 吴淑英,朱冬升,杨硕.Al2O3-H2O纳米流体的相变蓄冷实验研究[J].工程热物理学报,2009,30(6):981
14 曾翠华,张仁元.无机水合盐相变储热材料的过冷性研究[J].能源研究与信息,2005,21(1):44
15 Tyagi V V,Buddhi D.Thermal cycle testing of calcium chloride hexahydrate as a possible PCM for latent heat storage[J].Solar Energy Mater Solar Cells,2008,92(8):891
16 沈卫东,曾丹苓.车用潜热贮热器相变贮热材料Ba(OH)2·8H2O的成核[J].工程热物理学报,1996,17(Z):5
17 丁益民,阎立诚,薛俊慧.水合盐储热材料的成核作用[J].化学物理学报,1996(1):83