非均匀热流下球形腔式吸热器热性能的数值研究

Thermal performance numerical investigation of spherical cavity receiver under non-uniform heat flux boundary

建立了球形腔式吸热器三维模型;以基于蒙特卡罗光线追迹法（MCRT）进行光学模拟得到的能流分布,作为吸热管壁的热边界条件;通过数值模拟研究球形吸热器的耦合传热问题;探讨吸热流体入口参数对热性能的影响。研究表明：吸热管壁的辐射能流密度分布不均匀;在相同条件下,下入口吸热器的热性能优于上入口吸热器;在吸热流体的入口速度为0.2-0.4 m/s,提高流速可明显增大吸热器热效率,入口速度大于0.6 m/s时,热效率的增大速率变得平缓;随入口温度升高,热效率几乎呈线性下降。基于非均匀热流边界条件下的吸热器三维数值模拟结果更符合实际情况,为吸热器的优化设计与推广应用提供依据和参考。

A three-dimensional model of spherical cavity receiver is established. Energy flux distribution simulated by Monte-Carlo ray tracing（MCRT） is served as the thermal boundary of heatabsorbing tube wall. A numerical simulation study on coupling heat transfer is then conducted to investigate inlet parameters＇ influence on the thermal performance of the spherical cavity receiver. The results are showed as followed. The radiant energy flow density distribution of the spherical cavity receiver is not uniform. Under the same conditions, the spherical cavity receiver with lower entrance has a better thermal performance than that with upper entrance. Within the range of 0.2-0.4 m/s, a high inlet velocity of the heat transfer medium can significantly improve the thermal efficiency, however, if the inlet velocity is larger than 0.6 m/s, the increase of inlet velocity could only slightly improve the thermal efficiency. With inlet temperature increasing, the thermal efficiency descends linearly. The 3-D simulation results based on non-uniform heat flux boundary agree with the actual phenomenon.Therefore, the investigation can provide some references for the design of spherical cavity receiver.