相变材料蓄热特性的模拟研究

发布时间：2018-03-25 11:27

本文选题：相变蓄热　切入点：数值模拟　出处：《湖南科技大学》2013年硕士论文

【摘要】：能源紧张已经成为21世纪全世界面临的重大难题。相变材料相变过程中能蓄存或释放大量热量，，具有蓄能密度高、易匹配、易控制等众多优点，这可以用于解决热能供需双方时间上的不一致问题，具有重要的实用价值。相变蓄能技术研究和应用受到了全世界的广泛关注。由于相变换热过程中同时存在导热与对流的作用，导致相变换热问题的求解相当复杂，一般要借助数值模拟进行求解。本文采取Fluent软件对影响相变传热因素进行模拟分析，并对肋片强化换热效果进行模拟优化。主要研究内容包括: （1）在第一类边界条件下，利用焓法，建立了相变蓄热装置的数学和物理模型。在模型水平和竖直放置两种情况下，分析了不同壁面温度下相界面移动规律，完成熔化/凝固所需时间以及液相率的变化等情况。分析了自然对流在相变材料蓄热与放热过程中的作用，在融化过程中，自然对流影响很大，大大加快融化速度；而在凝固过程中，自然对流的作用较弱，对完成凝固所需时间影响较小，并且对凝固速率有轻微抑制作用。 (2)在相变蓄热装置中添加翅片，对相变蓄热系统进行强化换热。论文对多种不同几何尺寸肋片结构的相变蓄热器进行了模拟，重点分析了蓄热系统中肋片个数、肋片高度以及肋片厚度对相变完成时间的影响。结果显示：肋片管的换热效果明显好于光管，能大大缩短熔化时间，提高换热效率。肋片的几何尺寸对换热系统的换热效率影响很大，增加肋片个数、厚度和高度能有效提高换热速度，完成相变蓄热或放热的时间都有所缩短。增加肋片高度对强化换热效果最好；肋片个数和厚度的增加，对提高换热效果的趋势会渐趋平缓。
[Abstract]:Energy shortage has become a major problem facing the world in the 21st century. Phase change materials can store or release a lot of heat in the process of phase change, which has many advantages, such as high energy storage density, easy matching, easy control and so on. This can be used to address the time gap between the supply and demand of heat energy, The research and application of phase-change energy storage technology have attracted worldwide attention. Due to the effect of heat conduction and convection in the process of phase change heat transfer, the solution of phase transformation heat problem is very complicated. In this paper, the factors affecting the heat transfer of phase change are simulated and analyzed by Fluent software, and the heat transfer effect of rib is simulated and optimized. The main research contents are as follows:. 1) under the first boundary condition, the mathematical and physical models of phase change heat storage device are established by using enthalpy method. In the case of horizontal and vertical placement of the model, the law of phase interface movement at different wall temperatures is analyzed. The effect of natural convection on the heat storage and exothermic process of phase change materials is analyzed. In the solidification process, the effect of natural convection is weak, the effect of natural convection on the time required to complete solidification is small, and the solidification rate is slightly inhibited. In this paper, the phase change accumulator with different geometric sizes is simulated, and the number of fins in the system is analyzed. The effect of rib height and rib thickness on the completion time of phase transformation shows that the heat transfer effect of ribbed tube is better than that of smooth tube, and the melting time can be shortened greatly. The geometric dimension of the rib has a great influence on the heat transfer efficiency of the heat transfer system. Increasing the number, thickness and height of the rib can effectively improve the heat transfer rate. The effect of heat transfer is best with the increase of the height of the rib, and the increase of the number and thickness of the rib will gradually slow down the trend of improving the heat transfer effect.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TB34;TU551

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