吸热过程光―热耦合特性及复杂非稳态传热机理研究
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摘 要：太阳能热发电是太阳能的高品位利用方式，吸热器是太阳能热发电系统中用于聚光太阳辐射能与热能转换的核心部件。根据聚光器类型、传热介质、运行压力和温度的不同，吸热器主要有真空管式和腔体式两种类型。该课题针对极端条件（时空分布随机变化的高温、高热流密度），以提高吸热器吸热效率为目的，研究吸热器内辐射-导热-对流耦合的传热机理，构建设计各类吸热器需要遵循的理论架构，设计新型高效稳定的吸热器。该课题的研究对太阳能热发电的规模化进程具有非常重要的意义。实现了基于蒙特卡罗光线追踪法的自编数值模拟程序，获得了槽式、塔式和碟式吸热器吸热面上的聚焦太阳能流分布，实现了蒙特卡罗光线追踪法和用于求解流动传热问题的有限容积法的耦合，研究了太阳辐射由镜场到吸热器的一体化传播过程。研究了槽式太阳能吸热器内的流动换热特性，建立了槽式DSG集热器的稳态传热计算模型和动态模型，开发了两类管内强化传热技术；基于DSMC方法建立真空管空气夹层内稀薄气体传热模型；耦合管内对流传热、管壁导热、真空夹层稀薄气体传热及辐射传热、管外对流传热及辐射传热，可望建立真空管吸热器的跨尺度传热模型的数值预测方法。建立了腔式水工质吸热器和腔式熔融盐吸热器吸热性能的数学模型，获取了吸热器内部热流密度和吸热管道温度的分布规律以及吸热器的热损失。结合腔式吸热器热性能的数学模型，提出了由吸热器所需净能量推算吸热器开口所需太阳光能量的计算模型，发展了腔式吸热器启动过程性能模拟的数学模型，获得了吸热器启动过程开口所需能量数据曲线，吸热器启动过程的效率曲线和热损失曲线。研究了高温高压下空气吸热器内复杂耦合换热机理，分析了安装倾角、入口工质温度与质量流量等重要参数对有压腔式吸热器换热性能的影响；运用十四面体模型模拟多孔材料的内部结构，研究了多孔吸热结构内的对流传热特性。设计了搭建了太阳能空气吸热器实验平台，采用氙灯阵列模拟太阳辐射，多孔吸热材料表面可接受的辐射功率范围可达10 kW，热流密度可达2×106 W/m2；设计搭建了槽式DSG太阳能热发电实验研究系统，设计压力10 MPa、温度400 °C，利用该实验系统除了对槽式DSG热发电系统进行试验研究外，还能对槽式热发电的集热器、聚光器的性能进行测试。
关键词：真空管吸热器 腔体式吸热器 耦合传热机理 极端条件
Abstract：Solar thermal power generation is a way of high-grade solar energy utilization. Solar receiver is the key component of solar thermal power generation system， through which the concentrated solar radiation can be converted into thermal energy. In the present study， the fluid flow and heat transfer characteristics in deferent thermal receivers are investigated to improve the thermal receiving efficiency of receivers under transient and extreme conditions of high temperature and heat flux with space-and time-randomness. The present research has very important significance to the large-scale utilization solar thermal power.The concentrated solar energy flux distribution on the thermo-receiving surfaces parabolic solar collector receiver， cavity receiver and dish receiver is obtained by self-coded Monte Carlo Ray-Trace Method （MCRT Method）. The coupled MCRT-FVM method is proposed and the integrated process of ray-concentration， thermal-receiving and the energy conversion is investigated. The fluid flow and heat transfer characteristics in parabolic trough solar receiver are performed numerically. The steady and transient heat transfer models for DSG trough receiver are established. The rarefied gaseous heat transfer in the vacuum annulus is conducted with the self-coded direct simulation Monte Carlo （DSMC） method. The multi-scale heat transfer model and its numerical method will be proposed with coupling the interior convective heat transfer， the heat conduction in the solid wall， the rarefied gaseous heat transfer and thermal radiation in vacuum annulus and the outer convection and radiation. A combined calculation method for evaluating the thermal performance of the solar cavity receiver is raised. The surface heat flux inside the cavity， the wall temperature of the boiling tubes， and the heat loss of the solar receiver are obtained and validated with an iterative solution. By combining the MCRT and the finite volume method （FVM）， the complicated heat transfer in the pressurized volumetric receiver （PVR） in high pressure and temperature condition are revealed. The unit-cell model of tetrakaidecahedron for simulating the porous SiC structure is adopted to investigate the flow and heat transfer. The experimental rigs for solar air receiver and DSG solar power are designed and established.
Key Words：Parabolic trough tube receiver；Cavity/Volumetric receiver；Coupled hear transfer mechanism；Extreme conditions
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