Harmonizing green energy: enhancing parabolic trough solar collectors through numerical optimization, twisted tapes, and nanofluids, with an environmental perspective

In this paper, a parabolic trough solar collector with variable heat flux depending on various twisted tapes as a swirl generator with cerium oxide, copper oxide, and multi-walled carbon nanotubes nanofluids with different volume fractions is presented. First, the impact of different twisted tapes is discussed, and the next part analyzes the influence of different volume fractions of nanofluids on improving the outlet temperature and the heat transfer coefficient. Finally, the best volume fraction of these nanofluids is used to form the hybrid nanofluid, and its effect on the turbulence thermal efficiency is numerically assessed. The obtained outcomes indicate that using a quadruple twisted tape improves the rate of heat transfer because it induces more rotational flow compared to other cases. Moreover, hybrid nanofluids of cerium oxide/copper oxide with a 2% volume fraction demonstrated the most increased thermal efficiency. Furthermore, to facilitate a broader utilization of the results, a precise relationship for the pressure drop and heat transfer coefficient in relation to alterations in terms of geometry, fluid velocity, and thermophysical properties obtained through statistical analysis is provided. Additionally, the assessed parabolic trough solar collector and a water heater with a capacity of 18,000 kcal/h were compared to evaluate the reduction in greenhouse gas emissions.