Abstract:

A gradient-absorption-packed solar receiver (GSR) comprising quartz glass balls and silicon nitride balls was proposed to increase the penetration depth of the incident solar radiation and decrease the re-radiation loss. Considering the incident solar radiation, the high-temperature coupled heat transfer model of the GSR was set up using the particle scale method. The high-temperature heat absorption characteristics of the GSR were investigated by employing numerical heat transfer and experimental verification. Results show that for the single-absorption-packed solar receiver (SSR), the thermal efficiency increases with decreasing the diameter of the silicon nitride balls. In contrast, the comprehensive efficiency (Q/ΔP) increases with increasing the diameter of the silicon nitride balls. For the GSR with D/d=5, the GSR filled with two layers of quartz glass balls yields the highest thermal efficiency when the mass flow rate is below 7.5g/s, and when the mass flow rate exceeds 7.5g/s, the GSR filled with one layer of quartz glass balls produces the highest thermal efficiency. Under the same D/d and mass flow rate conditions, the thermal efficiency and comprehensive efficiency of the GSR are higher than that of the SSR. Furthermore, the amplification increases as the working temperature increases, which suggests that the GSR is particularly suitable for high-temperature solar thermal applications.

Key words: solar energy, packed bed, solar receiver, heat transfer, thermal efficiency

摘要：

为增加聚集太阳光穿透深度，降低红外辐射散热损失，提出了一种由石英玻璃小球和氮化硅小球组成的梯度吸热颗粒堆积床太阳能吸热器（gradient-absorption-packed solar receiver，GSR）。采用颗粒尺度方法，建立了聚集太阳光辐射加热作用下GSR的高温耦合传热模型。结合实验测量验证，对GSR的高温吸热规律进行研究分析。结果表明，对单一吸热颗粒堆积床太阳能吸热器（single-absorption-packed solar receiver，SSR），颗粒直径越小，热效率越高，但是吸热量与压降之比的综合效率越低。对粒径比为5的GSR，在低质量流量范围（质量流量小于7.5g/s），二层石英玻璃小球的GSR热效率最高，而在高质量流量范围（质量流量大于7.5g/s），一层石英玻璃小球的GSR热效率最高。在相同粒径比和流量条件下，GSR的聚集太阳光穿透深度大，热效率和综合效率均高于SSR，且温度越高，增幅越大，说明GSR尤其适合高温吸热，具有重要的应用潜力。

关键词: 太阳能, 填充床, 吸热器, 传热, 热效率