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铜基金属相变储热胶囊的制备和应用基础研究
Alternative TitlePreparation and Characterization of Copper-based Macro-capsules as PCMs for High Temperature Latent
张国才
Subtype博士
Thesis Advisor陈运法
2014-04
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword铜基金属相变胶囊 封装方法 滚镀硬铬 热循环 相容性
Abstract针对高温工业余热回收和太阳能热发电系统,建立高温金属相变储能系统,将时间和空间上不匹配、间歇性的非稳态热源转化连续、均一的稳定热源。高温金属相变储能系统主要是利用金属相变材料的高储热密度和高热导率,其核心是高温金属相变储热胶囊。高温金属相变储热胶囊的研究开始于上世纪80年代,然而,由于高温金属相变材料在液相时的高腐蚀性,难以进行有效的封装。虽然国内外在高温金属相变储热胶囊的制备方面取得了一些进展,成功制备了一些金属相变储热胶囊,然而其性能指标仍远远低于高温金属相变储能系统的要求。本文以金属相变材料铜球(熔点1080?C)制备高温金属相变储热胶囊,主要是利用金属铜的高储热密度(205.36J/g)和高热导率(398W/m?K);其次,球体拥有最低的比表面积,使金属相变储热胶囊采用最少的封装材料并拥有最高的储热密度;另外,金属铜来源广泛,成本低廉,易于加工。根据封装材料的相容性要求、物理性能和热性能,选择金属铬和金属镍作为金属相变材料铜球的封装材料。本论文主要在以下几个方面取得了创新成果: (1)首次成功制备了Cu@Cr、Cu@Ni和Cu@Cr-Ni高温金属相变储热胶囊。Cu@Cr-Ni金属相变胶囊具有储热密度高、热导率高、相容性能优异、热循环性能良好、抗氧化性能良好等优点。Cu@Cr金属相变胶囊则具有储热密度高、热导率高、相容性能优异的特点。Cu@Ni金属相变胶囊则具有储热密度高、热导率高、热循环性能良好、抗氧化性能优异等优点。 (2)Cu@Cr金属相变胶囊制备成功的关键就在于独创的周期间歇式滚镀硬铬方法。其包含了两方面独特的设计:首先,独特的阴极设计能够保证金属相变材料铜球的良好导电性,避免了铬镀层的钝化,使得金属铬不断地沉积在铜球表面上;另一方面,周期性的振荡,能够保证铬镀层厚度的均匀性,电流尖端“密集聚集”效应,能够避免传统铬镀层中的裂纹和孔隙出现。Cu@Ni金属相变胶囊的制备原理比较简单,主要是金属镍离子在电化学的作用下进行沉积。Cu@Cr-Ni金属相变胶囊的制备原理则有效结合了周期间歇式滚镀硬铬和滚镀镍的机理。 (3)周期间歇式滚镀硬铬方法同时也提供了一种有效的滚镀硬铬的新方法。传统的滚镀铬装置仅能获得装饰性铬镀层(厚度为0.25μm~0.5μm),而获得硬铬层(厚度大于5μm)的滚镀铬装置仅在相关文献上有过报道,但实际并未见相关商品装置。目前,通过新方法获得的硬铬层厚度最高可达500μm,铬层厚度非常均匀,铬层厚度非常致密,且没有任何孔隙和裂纹。而传统方法获得的硬铬层均存在裂纹和空隙。另外,由于铬镀层易钝化,很难在其表面沉积金属。通过新设计的一种特殊处理方法,成功在铬镀层上获得了镍镀层。 (4)系统考察了电流波形、电场排布对电镀硬铬的影响,比较了标准镀铬液和复合镀铬液两种镀铬液的镀层性能和电镀速率,初步确立了采用复合镀铬液实现滚镀硬铬。通过对温度和电流密度进行因素设计实验,确立了复合镀铬液的使用工艺范围。针对金属相变材料铜球的封装要求,最终选定CrO3 250g/L,H2SO4 1.25g/L,H2SiF6 5g/L,55 ?C,52 A/dm2作为滚镀硬铬的配方和使用工艺。 (5)设计研制了两种滚镀硬铬装置:铜网筛振镀铬装置和周期间歇式滚镀硬铬装置。通过实验比较分析,初步确定采用周期间歇式滚镀硬铬装置进行铬封装。考察了该方法操作因素:间隔周期、面积比和电镀时间对铬封装的影响。确定最终操作工艺为间隔周期15min、面积比0.8、电镀时间8h。在此条件下获得的铬镀层厚度均匀完整,能够实现对铜球的完整封装。 (6)初选了滚镀镍溶液的国内外配方,详述了滚镀镍溶液的配制方法,并对配方中各成分的作用和功能进行了说明。考虑到添加剂对镀层性能的影响,确定了实验中所采用的滚镀镍溶液配方。简单阐明了滚镀的工作原理,详述了整套滚镀镍装置及操作程序。分析探讨了滚镀电流密度控制的三种方法:按筒计、按全部电镀面积计、按有效电镀面积计,并根据法拉第定律对不同控制方法的电镀时间进行了估算。 (7)对Cu@Cr-Ni金属相变胶囊的储热密度和热循环性能进行了优化设计。主要控制铬-镍镀层的厚度比和总厚度:设置不同的铬镀层厚度,然后在相同的铬镀层,调控不同的镍镀层厚度,滚镀硬铬时间和滚镀镍时间分别为24h、48h、72h、96h。热循环实验结果初步表明,在目前总热循环42次的情况下,获得的Cu@Cr-Ni金属相变胶囊的储热密度最高理论值为70J/g,初步实现了最大储热密度和最佳热循环性能的结合。 (8)通过对国内外目前高温金属相变胶囊的换热器模型进行分析,结合Cu@Cr-Ni金属相变胶囊的高热导率和高温特性,建立了高温填充床储热系统物理模型。模拟了1500?C和870?C两种热流体经过高温填充床储热系统物理模型的温度变化。模拟结果表明,Cu@Cr-Ni金属相变储热系统,能够将间断的、周期性的高温热流的热量快速吸收,用于预热间断的、周期性的低温热流,使热流系统的输出温度几乎保持恒定。 关键词:铜基金属相变胶囊,封装方法,滚镀硬铬,热循环,相容性
Other AbstractLatent heat storage system on the basis of high temperature metas as as phase change materials (PCMs) can be applied in high temperaturte industrial waste heat recovery and solar thermal power generation. Inermittent and unstable heat source in space and time can be converted into continuous and stable heat source. High temperature metals as PCMs are the core in high temperature metallics latent heat storage system for its high thermal conductivity and high energy density. However, high temperature metals are hard to encapsulate due to its serious corrosive properties in liquid phase. Though plenty of research about this has began in 1980s. Some metal-based macro-capsules are prepared successfully by some researchers, its some properties are low compared to desired value of high temperature metallic latent heat storage system. In this paper, copper balls (melting point 1080?C) are selected as PCMs for its high therml conductivity (398W/m?K), high energy density (205.36J/g), low cost and easy handle. Ball has the lowest surface to volume ratio, leading to the least encapsulating material required and the highest energy density of copper macro-capsule.In addition, chromium and nickel were selected as encapsulating materials accoding to requirements in compatibility, physical and thermal properties. Some innovative results can be concluded in the following text. (1) Cu@Cr macro-capsule, Cu@Ni macro-capsule and Cu@Cr-Ni macro-capsule were successfully prepared firstly. Cu@Cr macro-capsule, Cu@Ni macro-capsule and Cu@Cr-Ni macro-capsule were characterized by thermal property, thermal cycles property, compatibility property and oxidation resistance property. The results showed that Cu@Cr macro-capsule has high energy density, good compatibility property, thermal cycles and poor oxidation resistance property. Cu@Ni macro-capsule has high energy density, good thermal cycles, excellent oxidation resistance property and poor compatibility property. Cu@Cr-Ni macro-capsule has lower energy density, the best thermal cycles property, good compatibility property and excellent oxidation resistance property. (2) Cu@Cr macro-capsules were successfully parepared due to two distinctive designs of hard chromium periodic-barrel plating method. Distinctive cathode design can avoid outage and subsequent passivation of electrodeposited chromium layer, then can assure hard chromium can be electrodeposited all the time in whole process. Periodic viabration can assure that chromium layer gained is unifrom and integrity under the effect of aggregation on tips for direct current. Preparation mechanism of Cu@Ni macro-capsule is simple that nickel was electrodeposited on copper balls’ surface through nickel barrel plating method. Preparation mechanism of Cu@Cr-Ni macro-capsule is combination of Cu@Cr macro-capsule and Cu@Ni macro-capsule. (3) Chromium periodic-barrel plating method also provides an effective method of hard chromium barrel-plating. Hard chromium gained is uniform and its thickness can be up to 500 μm. Compared to traditional hard chromium layer with more or less pores and flaws, chromium layer is very dense without any pores or flaws. It was only reported in literatures about decorative chromium barrel-plating equipments, but that can not be found on market. It was not any report about successful hard chromium barrel-plating method. In addition, it has never heard that nickel layer can be electrodeposited on chromium layer successfully. A novel method was designed that nickel layer can be electrodeposited on chromium layer successfully. The bond of nickel layer and chromium layer is tight and powerful (4) Direct current waveform and electric field distribution were investigated in hard chromium electroplating process. Compared to properties of electroplated layer and electroplating rate on standard chromium solution and compound chromium solution, compound chromium solution was confirmed. The applied filed of compound chromium solution
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15536
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
张国才. 铜基金属相变储热胶囊的制备和应用基础研究[D]. 中国科学院研究生院,2014.
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