Optimizing heat transfer in a solar parabolic trough collector absorber

This research focuses on optimizing the thermal performance of solar parabolic trough collector (SPTC) systems that are specifically tailored to Thailand’s unique climatic and economic conditions. The study combines experimental and numerical methodologies to evaluate innovative designs for solar absorber tubes through Computational Fluid Dynamics (CFD) simulations. The research focuses on two key optimization approaches to improving the efficiency of solar absorber tubes: external fined solar absorber tubes and looped solar absorber tubes. A prototype SPTC system was designed and constructed using locally sourced materials and labor, and it was tested under real-world conditions in Thailand. The system incorporates a solar tracking mechanism, a 300-mm focal length, a 6.3-m² aperture area, and uses water as the heat transfer fluid (HTF). The first optimization approach explored the impacts of external fins on solar absorbed tubes. Results revealed that finned tubes significantly outperformed smooth tubes in thermal efficiency across all Reynolds numbers. Increasing the number of fins enhanced thermal performance, with smaller fin diameters proving more effective than larger ones. Notably, a finned tube with nine fins per inch and a fin diameter of 22 mm demonstrated over a 55% improvement in thermal efficiency compared to smooth tubes. The enhanced surface area provided by the fins facilitated improved heat absorption, underscoring the value of this design modification. The second optimization approach investigated looped solar absorber tubes, which demonstrated superior thermal efficiency compared to straight tubes at all Reynolds numbers. Efficiency gains were more pronounced at higher Reynolds numbers, with double-loop configurations delivering the best performance, achieving over a 65% improvement compared to straight tubes. The extended residence time of the heat transfer fluid within the looped tubes enabled greater heat absorption. Additionally, the study revealed the significant role of flow rate in influencing the temperature gradient between the inlet and outlet, further impacting the thermal performance of the absorber tubes. Furthermore, the research presents a prototype of the SPTC system featuring an appropriately designed structure and solar tracking mechanism with an aperture area of 6.3 m² and a focal length of 300 mm; the system demonstrated the ability to efficiently capture and convert solar radiation into thermal energy. Beyond its technical merits, the system achieved annual CO₂ emissions reductions of over 270 kilograms, highlighting its environmental benefits and supporting the economic feasibility of domestically produced solar concentrating technologies. Finally, this study provides a comprehensive framework for enhancing SPTC systems through innovative absorber tube designs tailored to Thailand’s context. By integrating cost-effective, locally sourced components, the research supports the development of sustainable energy solutions for both community and industrial applications. The findings contribute to advancing Thailand’s renewable energy objectives, reducing reliance on imported technologies, and promoting technological self-sufficiency.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2025

Author dc:creator

• Limboonruang, Teerapath

Licence

• https://dora.dmu.ac.uk/bitstreams/8070073f-13c7-4b3b-837c-028c9904ab2b/download