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类型 综合研究 预答辩日期 2018-03-02
开始(开题)日期 2014-06-11 论文结束日期 2018-01-22
地点 能源与环境学院动力楼422教室 论文选题来源 国家自然科学基金项目     论文字数 7.23 (万字)
题目 复合相变材料的传热特性研究
主题词 复合相变材料,多孔介质,相变传热,多尺度模拟,相变储能
摘要 复合相变材料作为存储热能的功能材料在建筑节能、太阳能热利用、宇航工程隔热保温、电力系统移峰填谷、微电子芯片散热等领域有着广泛的应用前景。由于多种材料之间相互耦合,复合相变材料中相变传热过程具有非线性的特征。目前,对复合相变材料的宏观传热特征尚未充分认识,复合相变材料的介观和微观尺度传热机理也尚未阐明。 本文首先应用分子动力学方法从微观尺度对相变材料的相变传热微观机理进行了研究。在此基础上,分别建立了复合相变材料宏观尺度和介观尺度的物理模型,并采用有限容积法、格子Boltzmann方法对相变传热过程进行了数值模拟。然后实验研究了复合相变材料的有效导热系数,并可视化观测了孔隙尺度相变传热过程。最后本文研究了集成复合相变材料的储能型太阳能集热器的集热性能。 本文的主要内容和结论如下: (1)复合相变储能材料宏观尺度数值模拟研究。建立了不同组合形式复合相变储能材料的物理模型,数值模拟了定温条件下相变材料的温度场。考虑了有效导热系数、二元相变材料融点、多孔介质孔隙率等影响因素,采用显热容方法处理相变过程,模拟了复合相变材料温度场、流场和相的分布特性。研究结果表明:复合相变材料较单一相变材料在传热和蓄热方面具有较大优势;二元组合式复合相变材料兼具蓄热良好和传热过程快的特点;多孔介质复合相变材料传热过程中温度变化最快。 (2)多孔介质复合相变储能材料介观尺度数值模拟研究。基于分形布朗运动方法和随机生成方法构建了多孔介质模型,分析研究孔隙尺度下多孔介质内部孔隙形状以及内部连通结构特性。基于局部非热平衡条件下的双分布函数模型,考虑多孔介质骨架与复合相变材料之间的传热过程,采用焓法处理相变过程,模拟了复合相变材料在孔隙结构内融化和运动形态。研究结果表明:高热导率的金属多孔骨架结构优先于复合相变材料接受来自定温壁面的传热。通过金属骨架的热传导在整个过程传热机理中起到主导作用。由于金属多孔骨架的存在,极大地抑制了液态相变材料的对流效应。 (3)相变传热微观尺度数值模拟研究。建立了固态正十八烷的分子动力学模型,应用反向非平衡分子动力学方法,分析了相变材料的微观传热机理。基于Monte Carlo方法,研究了相变过程分子位置的变化,揭示了微观尺度下相变过程分子的动力学行为。研究结果表明:基于非平衡理论的分子动力学方法可以得到相变材料温度变化特性曲线,从而可以准确预测其导热系数;使用Monte Carlo方法可以有效预测物质的相变点。 (4)复合相变材料相变传热的实验研究。设计并搭建了一套用于测定复合相变材料有效导热系数的实验装置。建立了复合相变材料导热系数的宏观理论模型,并通过实验对其进行了验证。开展了多孔介质复合相变材料相变传热的可视化实验,揭示了宏观尺度和孔隙尺度下多孔介质复合相变材料相变过程的差异,实验测试的结果验证了本文采用有限容积法和格子Boltzmann方法模拟相变传热过程结果的可靠性。 (5)集成复合相变材料的太阳能平板集热器应用研究。建立了二维太阳能平板集热器物理模型,使用二元石蜡-月桂酸复合相变材料作为储能材料,研究了在冬夏两季典型气象条件下,集热器内温度变化情况。研究结果表明,与未填充泡沫金属的相变储能平板集热器相比,泡沫金属的加入使得集热器整体温度分布更为均匀;集热器内相变材料的融化率大为提高;集热器可在冬季工况下使用,从而可用于无水箱环境下在全年提供生活热水。 本文采用理论和实验相结合的方法研究了复合相变储能材料特别是多孔介质复合相变材料的传热特性,分析了复合相变材料强化传热的影响因素,探索了复合相变储能材料在太阳能光热利用领域的应用潜力。本文研究对复合相变材料相变和热传输规律的研究具有重要价值;研究结果将进一步完善泡沫金属复合相变材料内流动与传热的理论,同时对于泡沫金属复合相变材料在太阳能储能等领域的应用提供理论指导和技术支撑。
英文题目 STUDY ON THE HEAT TRANSFER CHARACTERISTICS IN COMPOSITE PHASE-CHANGE MATERIALS
英文主题词 composite phase change materials, porous medium, phase-change heat transfer, multiscale simulation, phase-change energy storage
英文摘要 As functional materials which are used to store heat, the composite phase change materials (PCMs) are of great importance in a wide range of areas, such as building energy conservation, thermal utilization of solar energy, heat insulation in aerospace engineering, peak load leveling of power system, cooling of microelectronic chips, etc. Due to the conjugate heat transfer and the nonlinear characteristic of phase change process of the composite PCMs, the heat transfer characteristics of composite PCMs has not yet fully understand on the macroscopic scale. Besides, the exploration of the heat transfer mechanism in composite PCMs is to be carried out from the microscopic scale. Based on the molecular dynamics method, the mechanism of phase change heat transfer in microscopic scale is studied. On this basis, the mathematical and physical models in macro, meso scale are established. The finite volume method and the lattice Boltzmann method are used to simulate the phase change heat transfer process of PCMs. The thermal conductivity of the composite PCMs were then studied by experiments. In addition, the phase change heat transfer process is observed in pore scale through visual experiment. At last, the heat transfer performance of phase change energy storage solar collector was analyzed. The main contents and conclusions of this thesis are as follows: 1. Numerical study on composite PCMs in macro scale. The physical models of composite PCMs with different combination forms are established and the temperature fields of PCMs under constant temperature are simulated. Factors such as effective thermal conductivity, melting point of two element PCMs, porosity of porous medium and so on are considered. The phase transition processes are treated by means of appraent heat capacity method. The distribution characteristics of temperature field, flow field and phase in PCMs are simulated. The results show that the composite PCMs have a great advantage over the pure PCMs in heat transfer and heat storage. The two component cascaded composite PCMs have the characteristics of good heat storage and fast heat transfer process. Compared with other composite PCMs, the composite PCMs in porous medium have the fastest change in temperature during the heat transfer process. 2. Numerical study on composite PCMs in porous medium under meso scale. The porous media models are constructed based on the fractal Brown motion method and random generation method. The pore shape and the connectivity of the skeleton and pore of the model is analyzed. The dual distribution function model is based on local non thermal equilibrium condition. The heat transfer process between porous medium skeleton and composite PCMs is considered. The phase transition processes are treated by enthalpy method. The melting and motion patterns of composite PCMs in the pore structure are simulated. The results show that: The porous metal skeleton with high thermal conductivity has priority over the composite PCMs in receiving the heat transfer from the fixed temperature wall.The heat transfer in the metal skeleton plays a leading role in the heat transfer mechanism of the composite PCMs. Due to the existence of the metal skeleton in the porous composite PCMs, the convection effect of the PCMs in the cavity has been greatly suppressed. 3. Numerical study on phase change heat transfer in micro scale. A molecular dynamics model of solid n-octadecane is established. The microcosmic heat transfer mechanism of phase change materials is analyzed through reverse non-equilibrium molecular dynamics. Based on the Monte Carlo method, the change of molecular position in the phase transition process is studied. The kinetic behavior of the molecules in the microscale phase transition process is revealed. The results show that: The non-equilibrium molecular dynamics method can be used to obtain the temperature variation curve so as to predict the thermal conductivity of the material accurately. The Monte Carlo method can be used to predict the phase transition point of simple substance. 4. Experimental study on phase change heat transfer of composite PCMs. The testing platform of thermal parameters of composite PCMs was designed and built. The macro theoretical thermal conductivity model of composite PCMs is established and verified by experiments. The process of phase change heat transfer about the composite PCMs in porous medium was studied by visual experiment. The difference of phase change process under macro scale and pore size about the composite PCMs in porous medium is revealed. The experimental results show that the finite volume method and the lattice Boltzmann method are reliable in simulating the phase change heat transfer process. 5. Application study on the solar flat-plat collector integrated with composite PCMs. The two dimensional physical model of solar flat-plat collector is established. The binary mixture of paraffin and lauric acid is used as energy storage material. The temperature changes in heat exchanger during typical winter and summer weather conditions are studied. The results show that: Compared with a phase change energy storage plate collector without foam metal, the temperature distribution of the collector is even more uniform and the melting rate of the PCMs in the collector is greatly improved by the addition of foam metal. The collector with foam metal can be used in winter conditions and it can be used to provide hot water for the whole year in the environment without water tank. In this work, the heat transfer characteristics of composite PCMs, especially in porous media, are studied using the combined method of theory and experiment. The inflence factors of heat transfer enhancement of composite PCMs are analyzed. The application potential of composite PCMs in the field of solar heat utilization is explored. Research of the phase transition rule and the law of heat transfer happens in composite PCMs has important value. The research provides an effective supplement for the theory of flow and heat transfer in the foam metal composite PCMs. At the same time , it provides theoretical and technical support for the application of metal foam in the field of solar energy storage.
学术讨论
主办单位时间地点报告人报告主题
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工程热物理研究所 2015.2.2 东南大学动力楼 马强 多孔建材VOC 迁移及静电场对其行为影响研究
工程热物理研究所 2016.5.21 东南大学动力楼 吕楠 地表水水源热泵空调系统的热力性能仿真及节能运行研究
工程热物理研究所 2017.6.19 东南大学动力楼 郑功航 环状疏水泡沫金属管壁冷凝传热实验研究进展
工程热物理研究所 2014.11.18 东南大学动力楼 黄欣鹏 复合相变材料传热数值模拟研究
工程热物理研究所 2014.11.24 东南大学动力楼 黄欣鹏 相变储能换热器开发研究
工程热物理研究所 2016.12.25 东南大学动力楼 黄欣鹏 复合相变材料的传热研究
工程热物理研究所 2014.6.9 东南大学动力楼 施娟 多孔泡沫金属表面池沸腾相变传热过程研究
     
学术会议
会议名称时间地点本人报告本人报告题目
中国工程热物理学会 2016 北京 Study on the mechanism of heat transfer in composite phase change materials
IAQVEC2016 2016 韩国仁川 Numerical study on heat transfer performance of integrated phase change materials
     
代表作
论文名称
泡沫铝和石蜡复合相变材料的传热特性分析
Simulation of Solid-Liquid Phase Transition Process in Aluminum Foams Using the Lattice Boltzman
Experimental study on heat transfer performance of vacuum tube heat collector with thermal stora
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
茅靳丰 正高 教授 博导 陆军工程大学
黄护林 正高 教授 博导 南京航空航天大学
张小松 正高 教授 博导 东南大学
陈亚平 正高 教授 博导 东南大学
张辉 正高 教授 硕导 东南大学
杜垲 正高 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
施娟 其他 讲师 东南大学