共查询到19条相似文献,搜索用时 343 毫秒
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以相变芯材为核心的复合相变材料的潜热储存技术,对解决可再生能源间歇性问题有着关键作用.本研究以天然竹木为原材料,使用高温碳化方法得到碳化竹木,并使其分别吸附氧化石墨烯和还原氧化石墨烯,最终与聚乙二醇(PEG2000)复合形成稳定的复合相变材料.实验结果表明,还原氧化石墨烯可以达到很好的包封率、热导率和光热转换效率提升效果.碳化竹木/还原氧化石墨烯/聚乙二醇三元复合相变材料包封率高达81.11%,熔化潜热为115.62 J/g,凝固潜热为104.39 J/g,热导率大幅提升至1.09 W/(m·K)(纯PEG2000的3.7倍),光热转换效率大幅提高至88.35%(纯PEG2000的3.1倍). 相似文献
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石墨烯/石蜡复合材料的热物理性能研究 总被引:1,自引:0,他引:1
郭美茹周文周天孙志强周子民 《工程热物理学报》2014,(6):1200
为改善相变蓄热用石蜡的导热性能,通过向石蜡基材中掺杂微量的石墨烯制备石墨烯/石蜡复合材料。采用扫描电子显微镜、热传导分析仪和差式扫描量热仪等获取了复合材料的表观形貌、热导率、熔点和相变潜热等关键热物性参数,讨论了石墨烯质量分数对这些参数的影响。通过动态热响应实验,揭示了石墨烯质量分数和热源温度对复合材料热响应速率的影响规律。结果表明,与纯石蜡相比,石墨烯/石蜡复合材料的热导率得到显著提高。当石墨烯的质量分数由0.2%升至2.0%,复合材料的热导率由0.266 W·m~(-1)·K~(-1)提高到0.346 W·m~(-1)1·K~(-1)。复合材料的相变潜热与纯石蜡相比并未减小,且其热响应速率高于纯石蜡。 相似文献
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《工程热物理学报》2021,42(9):2345-2351
相变蓄热(LHTES)系统利用相变材料(PCM)的潜热可有效地提高系统的储热能力。通常,PCM的导热系数低,使LHTES系统的应用受到了限制。本文通过向十五烷中添加膨胀石墨提高导热系数,分别采用纯十五烷和含有质量分数为30%膨胀石墨的复合十五烷,在不同水流量下,对管壳式LHTES系统的储热特性进行了实验研究。实验结果发现:当储能介质为质量分数为30%膨胀石墨的复合十五烷时,放冷过程中有效储热系数和相对储热率在Re=4298时出现明显峰值,换热效率与储热能力达到相对平衡。并且,当Re=4298,采用含有质量分数为30%膨胀石墨的复合十五烷与纯十五烷相比,系统的有效储热系数可最高提升336.84%。 相似文献
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低温纳米复合相变蓄冷材料热物性研究 总被引:4,自引:0,他引:4
低温相变蓄冷的关键是蓄冷材料的开发.本文针对啤酒工艺对冷源温度的要求,选择BaCl2共晶盐水溶液为相变蓄冷材料基液,在基液中添加粒径为20nm的TiO2纳米粒子,形成具有蓄冷功能的纳米复合材料.对其热物性如导热系数、相变潜热、相变温度、过冷度及粘度进行了实验测量和分析.结果表明,在TiO2纳米粒子的质量分数为1%的情况下,纳米复合蓄冷材料的导热系数比基液提高了11.28%,过冷度从3.97℃降为1.21℃,同时粘度增加了21.7%,相变潜热略有降低. 相似文献
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氧化石墨烯膜各向异性热传输特性研究 总被引:1,自引:0,他引:1
氧化石墨烯膜是一类新型的层状材料。本文报道了氧化石墨烯膜的面内和垂直于面方向的热扩散率和热导率,发现垂直于面方向的热导率比面内热导率低一个数量级,展示了明显的各向异性特征。氧化石墨烯膜的导热系数远低于单层石墨烯的导热系数,其原因主要是由于氧化石墨烯膜间的接触热租和氧化石墨烯膜本身导热系数较低造成的。 相似文献
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为从微观尺度探寻相变材料的热物性变化机理, 本文采用分子动力学的方法, 构建了由正二十二烷组成的无定形结构的相变材料体系, 采用周期性边界条件以及COMPASS力场对相变材料的比热以及导热系数进行了模拟, 并对纯正二十二烷进行了DSC测试. 结果表明, 模拟所得的相变材料热容与文献实验值的偏差是6.5%, 熔点与DSC实验值的偏差是0.98%. 当温度为288–318 K时, 相变材料的导热系数在0.1–0.4 W·m-1·K-1 范围内波动, 且随着压力增大略呈下降趋势.
关键词:
扩散系数
比热
导热系数
分子动力学 相似文献
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Microscale graphite (Gr) and nanoscale multi-walled carbon nanotubes (MWCNTs) were chosen to modify the organic phase change material (PCM) of myristic acid (MA). The Gr/MA and MWCNTs/MA composite PCMs were prepared by adding the carbon materials at different mass fractions into MA. The experimental results indicated that both Gr and MWCNTs could enhance the thermal conductivity of MA. For the 3?wt% loading, the solid thermal conductivity of MA increased by 37.42% with Gr and 62.26% with MWCNTs. The FT-IR spectra showed that the reactions between carbon materials and MA were physical. The DSC results illustrated that the phase change latent heats of the composite PCMs decreased gradually with the additives increasing. Gr and MWCNTs strengthened the thermal stability of MA. The heat release rates of the composite PCMs accelerated. Three hundred thermal cycles of the chosen composite PCMs revealed that the prepared composite PCMs presented good thermal cycling stability. 相似文献
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N-octadecane/expanded graphite composite phase-change materials were prepared by absorbing liquid n-octadecane into the expanded graphite. The n-octadecane was used as the phase-change material for thermal energy storage, and the expanded graphite acted as the supporting material. Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal diffusivity measurement were used to determine the chemical structure, crystalline phase, microstructure and thermal diffusivity of the composite phase-change materials, respectively. The thermal properties and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results indicated that the composite phase-change materials exhibited the same phase-transition characteristics as the n-octadecane and their latent heat increased with the n-octadecane content in composite phase-change materials. The SEM results showed that the n-octadecane was well absorbed in the porous network of the expanded graphite, and there was no leakage of the n-octadecane from the composites even when it was in the molten state. 相似文献
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空调蓄冷材料研究现状及其新进展 总被引:4,自引:0,他引:4
分析了空调蓄冷材料研究现状及存在的一些问题 ,提出研制一种新型空调复合蓄冷材料 ,通过实验 ,分析该蓄冷材料的融点、融解热等热学性能。并通过实验研究寻找到了一种新型空调蓄冷材料 ,测试结果表明该蓄冷材料具有较高的相变潜热、适宜的相变温度和较好的热稳定性 ,因此可被应用于蓄冷空调系统中。 相似文献
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In order to enhance the thermal energy storage efficiency of phase change materials, in this paper, expanded graphite (EG), multi-layer graphene nanoplatelet (MGN), graphite powder (GP) and multi-walled carbon nanotube (MWCNT) as the effective heat transfer promoters in different mass fraction (0.1, 0.5, 1.0, 1.5 and 2.5 wt.%) were added into the paraffin. The chemical properties, latent heat capacities, thermal conductivities and heat storage performances of paraffin and the composites were investigated. The results showed that the addition of EG, MGN, GP and MWCNT could increase the thermal conductivity of paraffin. At 20 °C, the thermal conductivity of the paraffin was increased by 61.04%, 51.2%, 12.18% and 10.22% with 2.5 wt.% EG, MGN, GP and MWCNT, respectively. In addition, with the same mass fraction, the heat storage and release time of the composite were 56.03% and 54.26%, respectively, shorter than that of paraffin when the additive was EG. 相似文献
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采用分子动力学方法模拟了纳米金属铝在粒径为0.8-3.2 nm 时的熔点、密度和声子热导率的变化, 研究了粒径为1.6 nm的铝纳米颗粒的密度、比热和声子热导率随温度的变化. 采用原子嵌入势较好地模拟了纳米金属铝的热物性及相变行为, 根据能量-温度曲线和比热容-温度曲线对铝纳米颗粒的相变温度进行了研究, 并利用表面能理论、尺寸效应理论对铝纳米颗粒熔点的变化进行了分析. 随着纳米粒径的不断增大, 铝纳米颗粒的熔点呈递增状态, 当粒径在2.2-3.2 nm时, 熔点的增幅减缓, 但仍处于递增趋势. 随着纳米粒径的增大, 铝纳米颗粒的密度呈单调递减, 热导率则呈线性单调递增, 且热导率的变化情况符合声子理论. 随着温度的升高, 粒径为1.6 nm的铝纳米颗粒的密度、热导率均减小. 该模拟从微观原子角度对纳米材料的热物性进行了研究, 对设计基于铝纳米颗粒的相变材料具有指导意义. 相似文献
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