Loss of solar rays in linear Fresnel concentrators (LFCs) through the width difference of primary reflectors and absorber tube led the scientists to add secondary reflectors to these concentrators. This secondary reflector increases the optical efficiency, as it is mentioned in the literature. In this paper, the effect of the secondary reflector on energy and exergy efficiencies was investigated. To find the most efficient design, four orientations of secondary reflectors including circular, flat, few segmented, and parabolic were studied. The reference values for the thermodynamic properties for all types of secondary reflectors were considered, and the systems were simulated in the EES environment by applying the supposed parameters at the base point. The results showed that lack of secondary reflectors decreased the thermal efficiency of the system. It is found that the flat geometry increased the energy and exergy efficiencies, while the cost was increased. However, the low manufacturing cost makes it acceptable as it was appropriate in optical aspects. The energy and exergy efficiencies were enhanced in circular and parabolic designs less than that in the flat design. The few flat segmented model has the most energy efficiency. However, much increment in efficiencies justifies growth in costs. The parabolic secondary reflector had the least cost increment. Effects of the variations of the temperature of the inlet flow to the collector, the pressure of the inlet flow to turbine, and the pressure of the inlet flow to the first pump on the design parameters were investigated. The results demonstrated that the only benefit increasing the temperature of the inlet flow to the collector and the pressure of the inlet flow to the first pump is cost reduction. Also, the increment of the pressure of the inlet flow to the turbine increases the exergy efficiency.

中文翻译：

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二次反射器对应用于有机朗肯循环的线性菲涅耳聚光器影响的火用和火用经济学研究

由于初级反射器和吸收管的宽度差异导致线性菲涅耳聚光器 (LFC) 中太阳光线的损失，导致科学家们为这些聚光器添加了次级反射器。正如文献中提到的那样，该次级反射器提高了光学效率。在本文中，研究了二次反射器对能量和火用效率的影响。为了找到最有效的设计，研究了二次反射器的四个方向，包括圆形、平面、少分段和抛物线。考虑了所有类型的二次反射器的热力学特性的参考值，并通过在基点应用假定的参数在 EES 环境中模拟系统。结果表明，缺少二次反射器会降低系统的热效率。发现平坦的几何形状增加了能量和火用效率，同时增加了成本。然而，低制造成本使其可以接受，因为它在光学方面是合适的。与平面设计相比，圆形和抛物线设计的能量和火用效率提高较少。少数扁平分段模型具有最高的能效。然而，效率的大幅提高证明了成本的增长是合理的。抛物面二次反射器的成本增加最少。研究了收集器入口流的温度、涡轮入口流的压力和第一台泵的入口流压力对设计参数的影响。结果表明，提高收集器入口流温度和第一泵入口流压力的唯一好处是降低成本。此外，涡轮机入口流压力的增加提高了火用效率。