Thermal enhancement of parabolic trough collector with internally finned absorbers

• Published in: Solar energy 2017-11, Vol.157, p.514-531
• Main Authors: Bellos, Evangelos, Tzivanidis, Christos, Tsimpoukis, Dimitrios
• Format: Article
• Language: English
• Subjects: Absorbers; Finned absorber; Fins; Fluid flow; Heat; High temperature; Inlet temperature; Nusselt number; Pressure; PTC; Solar energy; Thermal efficiency; Thermal energy; Thermal enhancement index; Thermodynamic efficiency
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2017.08.067

•The use of internal longitudinal fins in the absorber is examined for the LS-2 PTC.•Twelve different fins are investigated and compared with the smooth absorber case.•Higher thermal enhancement and higher pressure drop are found for larger fins.•The final evaluation of the fins is based on the thermal enhancement index.•The fin with 20mm length and 4mm thickness is found to be the optimum choice. Parabolic trough collector is one of the dominant emerging solar technologies for producing heat at high temperatures (usually 200–400°C). The objective of this study is to investigate the thermal performance of internally finned absorbers. Twelve different fin geometries are examined and compared with the smooth absorber case for various operating scenarios. More specifically, the investigated internal fins have thicknesses 2mm, 4mm and 6mm, while their lengths are 5mm, 10mm, 15mm and 20mm. The examined parameters for the evaluation of the internally finned absorbers are the thermal efficiency, the Nusselt number, the pressure losses, as well as the thermal enhancement index. According to the final results, higher fin thickness and length lead both to higher thermal performance and simultaneously to higher pressure losses. The impact of the length on the results is found to be more intense than the thickness. According to the thermal enhancement index, the case with 20mm length and 4mm thickness is found to be the optimum case. For this absorber, the increase in the thermal efficiency and the thermal enhancement index are found 1.27% and 1.483 respectively for 600K inlet temperature, while the Nusselt number is proved to be 2.65 times greater than in the smooth case.