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平板太阳能集热器是太阳能热利用系统中常见的核心部件,其传热性能的优化对于提高能源利用效率具有重要意义.现有平板集热器大多采用厚度均匀的金属吸热板来吸收太阳辐射,将(火积)理论应用于吸热板导热过程的分析,在吸热板材料总体积一定的前提下对其厚度布局作优化设计,使其传热性能最优.首先,从理论上建立了吸热板集热性能与损失之间的对应关系,进而提出集热器性能优化的约束极值问题,并利用变分方法从理论上得到温度梯度场均匀的优化准则.最后,根据优化准则,通过数值模拟的方法对吸热板的厚度布局作优化设计.模拟结果显示,当太阳辐射强度为800W/m2、环境温度为300K、风速为3m/s时,优化后的集热器效率比优化前提高8.8%,等效节省铜材达30%.将风速为3m/s时的优化厚度布局在不同风速条件下作传热性能分析,其集热效率与均匀厚度吸热板相比亦有明显提高.
Flat-panel solar collectors are the common core components in solar thermal systems, and the optimization of heat transfer performance is of great significance to improve the energy efficiency.At present, flat-panel collectors mostly adopt the uniform thickness of metal heat-absorbing panels to absorb solar radiation , The theory of (fire product) is applied to the analysis of the heat conduction process of the heat absorption plate, and the thickness distribution of the heat absorption plate material is optimally designed to optimize the heat transfer performance.Firstly, The corresponding relationship between the heat collecting performance and the loss of the heat absorbing plate is given, and then the constrained extreme value problem of the collector performance optimization is put forward, and the optimization criterion of the temperature gradient field is obtained theoretically by using the variational method.Finally, according to the optimization criterion , The thickness layout of the heat sink is optimized by numerical simulation.The simulation results show that when the solar radiation intensity is 800W / m2, the ambient temperature is 300K and the wind speed is 3m / s, the optimized collector efficiency ratio The optimization of the pre-optimization 8.8%, the equivalent savings of 30% of copper.When the wind speed of 3m / s, the optimized thickness distribution under different wind speed conditions for heat transfer performance analysis, the collector efficiency compared with uniform thickness heat-absorbing panels There have also been marked improvements.