多孔材料对相变蓄热性能的强化研究
摘 要
在当今这个飞速发展的社会当中，能源问题始终是各行各业的决定性因素。同时，随着人们物质生活的进一步丰富，人们开始对环保问题也越来越重视。而造成环境污染的的主要原因就是能源的不合理使用及肆意的排放能源使用后产生的各种废物。伴随着能源的使用，就会涉及到能源的储存和释放问题。而能源的存储技术可以协调能源的供应与使用在空间和时间上的分歧，使得能源得到最大化的利用，进而在一定程度可以缓减能源对环境的污染。而在蓄热技术中，由于相变蓄热技术所具有的独特优点越来越受到学者们的重视，成为近年来研究的热点。
由于传统相变蓄热才材料存在导热系数低的缺点，限制了相变蓄热技术的实际应用。而在相变材料中添加高导热的多孔材料制成复合相变材料有效的解决了上述难题。本文采用FLUENT软件对纯共晶盐相变材料以及添加石墨泡沫和泡沫铜的复合相变材料的相变过程进行了数值模拟，并且进行了对比分析。同时，通过改变热流体的进口速度和温度等参数分别进行了模拟，并对比分析了这些参数对相变过程的影响。此外，本文还对相变装置中的温度分布进行了模拟研究。
关键词：相变蓄热；泡沫铜；石墨泡沫；共晶盐；FLUENT
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Abstract
Now, in the rapid development of the society, energy is the decisive factor in all walks of life. At the same time, with people's life better and better, people began to pay more attention to the environmental protection. The main reasons of environmental pollution are irrational use of energy and discharge all kinds of waste generated by burning energy. When we use energy, we will be faced with the problem of the energy storage and release. The energy storage technology can coordinate the difference in space and time when we using energy.
Because of the unique advantages of phase change technology, more and more people pay attention to it. The thermal conductivity of traditional phase change material is very low and this make the application of phase change heat storage technology limited. Add in the phase change material with high thermal conductivity of the porous material can solve this problem. In this paper, we used numerical simulation to study the phase change process of the eutectic salt phase change material and the composite phase change material which is adding graphite foam or copper foam in the eutectic salt. We use FLUENT to complete those numerical simulations. At the same time, I have changed the inlet velocity and temperature of the heat fluid and the porosity of the composite phase change material to study the impact of these parameters on the phase change process. In addition, I also have studied the temperature distribution in the device.
Keywords: phase change heat storage; copper foam; graphite foam; eutectic salt;
FLUENT
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目 录
摘 要 ................................................................................................................................. I Abstract ............................................................................................................................. II 目 录 ............................................................................................................................. III 1 绪论 ............................................................................................................................... 1
1.1 选题的目的和意义 ............................................................................................. 1 1.2 国内外对相变蓄热技术的研究 ......................................................................... 2
1.2.1 国内相变蓄热技术研究进展 ................................................................... 2 1.2.2 国外相变蓄热技术研究进展 ................................................................... 3 1.3 国内外对强化相变蓄热的研究 ......................................................................... 4
1.3.1 在相变材料中添加高导热填充物 ........................................................... 4 1.3.2 在相变装置中添加金属翅片结构 ........................................................... 5 1.3.3 通过对相变蓄热装置的结构进行优化改进来强化传热 ....................... 5 1.4 本课题的研究内容 ............................................................................................. 6 2 相变蓄热理论与数值计算方法 ................................................................................... 7
2.1 相变材料种类 ..................................................................................................... 7 2.2 相变储能材料的选择原则 ................................................................................. 8 2.3嵌入泡沫金属的复合相变材料的研究及制备 .................................................. 8
2.3.1 嵌入泡沫金属的复合相变材料的简介 ................................................... 8 2.3.2 泡沫铜\\共晶盐复合相变材料的制备及热物性测定 .............................. 9 2.4 相变传热的特点与数学模型 ............................................................................. 9
2.4.1 相变传热的特点 ....................................................................................... 9 2.4.2 相变蓄热过程的数学模型 ..................................................................... 10 2.5 相变传热问题的数值求解方法 ....................................................................... 12 2.6 本章小结 ........................................................................................................... 12 3 FLUENT软件介绍及数学物理模型的建立 .............................................................. 13
3.1 FLUENT软件介绍及凝固/融化模型 ............................................................... 13
3.1.1 FLUENT软件介绍 .................................................................................. 13 3.1.2 凝固/融化模型 ........................................................................................ 13 3.2 物理模型的建立 ............................................................................................... 15 3.3 数学模型的建立 ............................................................................................... 16 3.4 FLUENT软件设置和模型边界条件的确定 .................................................... 18 3.5模型算法验证 .................................................................................................... 19
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3.6 本章小结 ........................................................................................................... 20 4 数值模拟结果分析 ..................................................................................................... 20
4.1 加入多孔材料前后共晶盐的相变过程与数值结果分析 ............................... 20 4.2 管内流体温度对相变过程的影响分析 ........................................................... 25
4.2.1 管内流体温度对纯共晶盐相变过程的影响 ......................................... 25 4.2.2 管内流体温度对泡沫铜/共晶盐复合相变材料相变过程的影响 ........ 30 4.2.3 管内流体温度对石墨泡沫/共晶盐复合相变材料相变过程的影响 .... 35 4.3 流体速度对相变过程的影响分析 ................................................................... 39 4.4 装置内部温度分析 ........................................................................................... 41
4.4.1 单点温度变化分析 ................................................................................. 41 4.4.2 多点温度变化分析 ................................................................................. 42 4.5 换热管外形尺寸对相变过程的影响 ............................................................... 43
4.5.1 改变换热管外径 ..................................................................................... 43 4.5.2 改变换热管高度 ..................................................................................... 44 4.6 多孔材料孔隙率对相变过程的影响 ............................................................... 44 4.7 本章小结 ........................................................................................................... 45 5 总结与展望 ................................................................................................................. 47 致谢 ................................................................................................................................. 48 参考文献 ......................................................................................................................... 49 外文翻译 ........................................................................................ 错误！未定义书签。
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