光伏电池固液相变热管理耦合传热和混沌动力学机理研究

Photoelectric conversion efficiency and operating life cycle of photovoltaic cells can be improved by thermal management. Phase change material solid-liquid phase change cooling technology has the advantages of thermostatic heat absorption, large latent heat storage capacity, no moving parts and no external power, which has important application promise in the field of photovoltaic cell thermal management. Reported studies on solid-liquid phase change cooling technologies of photovoltaic cells were limited to the establishment of lumped models or two-dimensional numerical models under ideal constant heat flux boundary conditions. The influence of natural convection vortex structure on its performance was not clarified, and the dynamic mechanisms of temperature-time series were also not revealed. In order to reduce these shortcomings, inspired by fractal theory and chaos theory, the project firstly plans to construct fractal fins and perform experimental studies on solid-liquid phase change cooling technology of photovoltaic cells. Secondly, a mathematical model of coupled heat transfer under natural heat flux boundary conditions will be built. The model will be verified by experiments and coupled heat transfer mechanisms will be revealed. Finally, the vorticity enhanced heat transfer mechanisms and chaotic dynamics mechanisms of fractal fins will be identified from that of straight fins. The relationship among dynamic parameters under natural thermal boundary conditions, fractal fin geometric parameters, and that of dimensionless time, energy transfer and fluid flow parameters will be set up. In all, the above research can provide theoretical reference for the application of solid-liquid phase change cooling technology in the field of photovoltaic cells.

对光伏电池进行热管理，有利于提高其光电转换效率和运行生命周期，相变材料固液相变散热技术具有吸热恒温、潜热储热容量大、不需要运动部件和无需外功等优点，在光伏电池热管理领域具有重要的应用前景。已有关于光伏电池固液相变散热技术的研究，仅限于理想热流边界条件下集总数学模型或二维数值模型的建立，没有阐明自然对流涡结构对其性能的影响，也没有揭示温度时间序列蕴藏的动力学机制。为了弥补这些不足，受分形理论和混沌理论启发，本项目首先构建分形翅片和进行光伏电池固液相变散热的实验研究；然后建立自然热流边界条件下的能流耦合传递数学模型，与实验进行验证，揭示其耦合传热机理；最后识别分形翅片异于平直翅片的涡量强化传热机理和混沌动力学机理，建立“自然热边界条件动态参数、分形翅片结构参数-时间、能流传递无量纲准则数”关系式。上述研究内容可为固液相变散热技术在光伏电池领域的应用提供理论参考。

采用高效的热管理技术对光伏电池进行温度控制，有利于提高其光电转换效率和运行生命周期。基于有机相变材料的固液相变散热技术具有储热容量大、不需要运动部件和无需外功等优点，但是其导热率较低，散热性能需要进一步强化。为了提高光伏电池腔体中相变材料的传热性能，本项目对分形翅片等新型翅片作用于相变腔体中的热流传递特性开展了研究，主要研究内容包括：（1）翅片耦合相变材料用于光伏电池热管理物理模型和数值模型的构建；（2）基于分形翅片等多种翅片结构的固液相变热管理过程的传热强化；（3）相变腔内分形翅片等强化型翅片异于无翅片和平直翅片的流场行为和传热机理；（4）基于Cantor翅片的光伏电池热管理实验研究及光伏电池热管理室内外实验平台的搭建。本项目取得了以下重要结果：（1）在固液相变腔体内分区和添加翅片可以有效降低壁温，控温性能受结构参数以及导热与自然对流竞争机制的综合影响，在一定结构参数范围内，树状分形翅片相对平直翅片有更好的控温性能；（2）树状分形翅片可降低光伏电池前板温度和提升温度分布均匀度，但是抑制了自然对流，在受限空间内主要依靠空间导热网络增加传热面积进而实现总体传热性能增加，增加腔体倾角和降低腔体长宽比有助于提高光伏电池控温性能，树状分形翅片分叉角为60°时的控温性能总体最好；（3）搭建了光伏电池热管理的室内外实验测试平台，获得了Cantor集分形翅片调控热管理性能的影响规律，厘清了光伏电池温度时间序列混沌动力学的一般计算框架。本项目的研究成果可为翅片耦合相变材料在光伏电池热管理方面的潜在应用提供理论参考。