Thermodynamic analysis and performance evaluation of PTC receiver with external annular fins

Aketch, Jacob Mator

Thermodynamic analysis and performance evaluation of PTC receiver with external annular fins

Thesis / Dissertation

2024

Publisher

University of Cape Town

Department

Department of Mechanical Engineering

Faculty

Faculty of Engineering and the Built Environment

Abstract

Since the advent of industrial revolution, the main source of energy has been fossil fuels, and it has resulted in adverse environmental impacts. With the depletion of fossil fuels and greenhouse effect, the utilization of solar energy has attracted increasing attention owing to the distinct advantages, including cleanliness, sustainability, inexhaustibility. This has motivated extensive research and innovation to foster a shift to renewable energies, of which concentrated solar power presents itself as the most promising option. Given the unrivalled abundance of solar energy, the source has a potential to meet a substantial portion of future energy demand. This research investigates the influence of external annular fins on the thermal and thermodynamic performance of parabolic trough collector receiver. The objective is achieved by developing thermal and fluid flow model with geometry of varied fin length and fin numbers in different range of Reynolds number and inlet temperature. The model was implemented in commercial ANSYS Fluent software and validated with existing literature—Forristall (2003) that yielded significant agreement. The results showed that introduction of fins increases thermal efficiency of the receiver. An increase of 2.26 percent for Tin = 350 K, 2.21 percent for Tin = 400 K and 2.22 percent for Tin = 500 K was recorded for varying Reynolds numbers. Also, the thermal efficiency in t = 10 mm was higher than t = 5 mm with values in the range of 88 - 90.5 percent while smooth receiver fell in the range of 84 - 86 percent. Additionally, thermal enhancement factor showed slight improvement. i What's more, exergy efficiency showed an improvement with introduction of fins. It was noted that the enhancement increased the exergy efficiency by 2.44 percent for Re = 5000, 2.30 percent for Re = 10000, and 2.30 percent for Re = 20000. Similarly, entropy generation reduced with fins variations. The entropy generation rate decreases with increasing fin length. The smooth absorber tube has the highest entropy generation rate whereas the absorber tube with largest fin length has the lowest. Heat transfer irreversibility has been found to be dominant at lower turbulence and variation of annular fin length and numbers reduces it. In summary, the introduction of passive enhancement of external annular fins was shown by the results to be thermally and thermodynamically favourable, regardless of the degree of improvement. Therefore, this enhancement technique can be combined with other methods to design a high performing PTC receiver—an endeavour that will contribute to implementation of a stand-alone reliable PTC power plants

Keywords

Engeneering

Reference:

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Masters

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