THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

Tamizhselvan Lakshmanan Selvamani

,

Sridharan Veerapuram

online first only

Enhancing solar collector performance: An experimental study on zigzag rectangular angled strips and nanofluid integration

ABSTRACT
Solar thermal collectors have become an increasingly popular technology for harnessing renewable energy and have gained significant attention as a sustainable solution to meet the growing global energy demands. These systems efficiently convert solar radiation into thermal energy, making them a viable option for a variety of applications across the residential, commercial, and industrial sectors. The use of nanofluids as the working fluid in solar thermal collectors has been extensively investigated as the incorporation of nanoparticles has been demonstrated to enhance the thermal properties of these systems ultimately leading to improvements in their overall efficiency. This experimental study investigates the performance of a conjugate flat-plate solar collector with the inclusion of zigzag rectangular shaped angled strips inside the absorber tube. The study also explores the use of various nanofluids such as MgO/DIW, ZnO/DIW, and Al2O3/DIW at a 1.0% volume concentration as the working fluid to determine their potential for enhancing the thermal efficiency of the solar collector. The experiments were conducted with 450 angled strips at three different pitch ratios (Y = 2.0, 3.0, and 4.0) under identical working conditions. The performance of the rectangular shaped zigzag strip enhanced collectors was systematically compared to that of plain conjugate flat-plate solar collector collectors. For a pitch ratio of 2.0, MgO/DIW, ZnO/DIW, and Al2O3/DIW improve heat transfer by 30%, 28%, and 22% at higher Reynolds numbers compared to DIW. The MgO/DIW consistently provides the highest heat transfer enhancement across all configurations and pitch ratios. The Nusselt number increases by 45%, 42%, and 40% for MgO/DIW, ZnO/DIW and Al2O3/DIW at a pitch ratio of 2.0 showed a significant enhancement in heat transfer due to nanoparticle effects and zigzag rectangular angled strip induced turbulence. The thermal efficiency reaches around 85% for MgO/DIW nanofluids compared to DIW at a lower pitch ratio of 2.0. The friction factor increases by 15% for ZnO/DIW at lower Reynolds numbers compared to DIW. The Pumping power increased by 10% for ZnO/DIW in zigzag rectangular angled strip tubes compared to plain tubes. These findings revealed that utilizing high thermal conductivity nanofluids and zigzag rectangular strip geometries with optimized pitch ratios can enhance the performance of heat transfer systems especially in applications such as solar energy collectors and heat exchangers.
KEYWORDS
Conjugate Flat plate solar collector, nanofluids, Zig Zag rectangular strip, thermal performance factor, friction factor ratio, Nusselt number ratio
PAPER SUBMITTED: 2024-07-09
PAPER REVISED: 2024-10-28
PAPER ACCEPTED: 2024-12-04
PUBLISHED ONLINE: 2025-01-09
DOI REFERENCE: https://doi.org/10.2298/TSCI240709287S
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Enhancing solar collector performance: An experimental study on zigzag rectangular angled strips and nanofluid integration