相变材料导热系数强化及相变特性数值模拟研究

发布时间：2018-05-28 22:01

本文选题：泡沫金属 + W-P模型　；参考：《华北电力大学(北京)》2017年硕士论文

【摘要】：泡沫金属广泛应用于热沉,换热器以及储能蓄热系统。泡沫金属热物性主要受其微观拓扑结构的影响,本文根据泡沫金属的微观结构特点,分别建立了两种微观结构的泡沫金属模型,W-P模型和3DVoronoi模型来预测其整体有效导热系数。W-P模型为理想规则周期性模型,而3DVoronoi模型则与实际结构接近。基于以上两种模型,论文对不同泡沫金属中填充石蜡相变材料的整体有效导热系数进行了模拟。研究结果表明,孔隙率不是影响泡沫金属有效导热系数的唯一因素,3DVoronoi模型预测结果相比于W-P模型更为准确,因为其孔径分布的不均匀性以及骨架结构与真实微观结构更为接近。在孔隙率非常高的情况下,泡沫金属也能非常有效的提高石蜡相变材料的有效导热系数。为了更好的理解泡沫金属中固-液相变材料的传热机理,在孔隙尺度上探索新的实验方法和理论方法是非常必要的。本文结合表征单元法(W-P模型)以及有限元法研究了基于孔尺度泡沫金属/石蜡复合相变材料的相变融化过程。研究结果表明,泡沫金属可以强化石蜡相变传热过程,并且主要受其微观结构的影响。靠近热源与泡沫金属骨架的石蜡最先融化。石蜡的融化速率随着时间逐渐减小并且融化相界面有与泡沫金属骨架结构相平行的趋势。采用数值模拟的方法,我们可以迅速并且有效的得到石蜡相变材料在复杂结构中的相变传热过程。预期结果给研究人员提供了一种更为直接的了解多孔介质内部传热机理的研究方法,而且可以通过优化泡沫金属结构参数使得其在实际应用过程中可以实现更为高效的传热。
[Abstract]:Foam metal is widely used in heat sink, heat exchanger and energy storage system. The thermal properties of foam metals are mainly affected by their microstructure. Two kinds of microstructural foam metal models, the W-P model and the 3DVoronoi model, are established to predict the global effective thermal conductivity. The W-P model is an ideal regular periodic model, while the 3DVoronoi model is close to the actual structure. Based on the above two models, the effective thermal conductivity of paraffin phase change materials filled with different foam metals is simulated. The results show that porosity is not the only factor affecting the effective thermal conductivity of foamed metal. The prediction results of DVoronoi model are more accurate than those of W-P model, because the pore size distribution and the skeleton structure are closer to the real microstructure. In the case of very high porosity, foam metal can also improve the effective thermal conductivity of paraffin phase change materials. In order to better understand the heat transfer mechanism of solid-liquid phase change materials in foam metals, it is necessary to explore new experimental and theoretical methods on pore scale. In this paper, the melting process of phase change based on porous scale foam metal / paraffin composite phase change materials is studied by means of characterization unit method (W-P model) and finite element method (FEM). The results show that foam metal can enhance the phase change heat transfer process of paraffin wax and is mainly affected by its microstructure. Paraffin wax near the heat source and foam metal skeleton is the first to melt. The melting rate of paraffin wax decreases with time and the interface of melting phase is parallel to the structure of foam metal skeleton. By means of numerical simulation, the phase change heat transfer process of paraffin phase change materials in complex structures can be obtained quickly and effectively. The expected results provide researchers with a more direct understanding of the mechanism of heat transfer in porous media, and can optimize the structural parameters of foam metal to achieve more efficient heat transfer in practical applications.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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