吸熱過程光—熱耦合特性及復雜非穩態傳熱機理研究

李增耀　陶于兵　魏進家　王躍社　劉德有

摘 要：太陽能熱發電是太陽能的高品位利用方式，吸熱器是太陽能熱發電系統中用于聚光太陽輻射能與熱能轉換的核心部件。根據聚光器類型、傳熱介質、運行壓力和溫度的不同，吸熱器主要有真空管式和腔體式兩種類型。該課題針對極端條件（時空分布隨機變化的高溫、高熱流密度），以提高吸熱器吸熱效率為目的，研究吸熱器內輻射-導熱-對流耦合的傳熱機理，構建設計各類吸熱器需要遵循的理論架構，設計新型高效穩定的吸熱器。該課題的研究對太陽能熱發電的規模化進程具有非常重要的意義。實現了基于蒙特卡羅光線追蹤法的自編數值模擬程序，獲得了槽式、塔式和碟式吸熱器吸熱面上的聚焦太陽能流分布，實現了蒙特卡羅光線追蹤法和用于求解流動傳熱問題的有限容積法的耦合，研究了太陽輻射由鏡場到吸熱器的一體化傳播過程。研究了槽式太陽能吸熱器內的流動換熱特性，建立了槽式DSG集熱器的穩態傳熱計算模型和動態模型，開發了兩類管內強化傳熱技術；基于DSMC方法建立真空管空氣夾層內稀薄氣體傳熱模型；耦合管內對流傳熱、管壁導熱、真空夾層稀薄氣體傳熱及輻射傳熱、管外對流傳熱及輻射傳熱，可望建立真空管吸熱器的跨尺度傳熱模型的數值預測方法。建立了腔式水工質吸熱器和腔式熔融鹽吸熱器吸熱性能的數學模型，獲取了吸熱器內部熱流密度和吸熱管道溫度的分布規律以及吸熱器的熱損失。結合腔式吸熱器熱性能的數學模型，提出了由吸熱器所需凈能量推算吸熱器開口所需太陽光能量的計算模型，發展了腔式吸熱器啟動過程性能模擬的數學模型，獲得了吸熱器啟動過程開口所需能量數據曲線，吸熱器啟動過程的效率曲線和熱損失曲線。研究了高溫高壓下空氣吸熱器內復雜耦合換熱機理，分析了安裝傾角、入口工質溫度與質量流量等重要參數對有壓腔式吸熱器換熱性能的影響；運用十四面體模型模擬多孔材料的內部結構，研究了多孔吸熱結構內的對流傳熱特性。設計了搭建了太陽能空氣吸熱器實驗平臺，采用氙燈陣列模擬太陽輻射，多孔吸熱材料表面可接受的輻射功率范圍可達10 kW，熱流密度可達2×106 W/m2；設計搭建了槽式DSG太陽能熱發電實驗研究系統，設計壓力10 MPa、溫度400 °C，利用該實驗系統除了對槽式DSG熱發電系統進行試驗研究外，還能對槽式熱發電的集熱器、聚光器的性能進行測試。

關鍵詞：真空管吸熱器 腔體式吸熱器 耦合傳熱機理 極端條件

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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