Exergy and energy amelioration for parabolic trough collector using mono and hybrid nanofluids

Abstract

Energy and exergy efficiency amelioration of the parabolic trough has taken high interest since recent years, especially when nanofluid used as an enhancement category. This paper aimed to improve LS-2 parabolic trough model and compare the enhancement effect that occurred using different mono and hybrid nanofluids. Inserting mono nanoparticles of Al2O3, CeO2, CuO, and hybrid combinations of Al2O3 with CeO2, or CuO nanoparticles in a Syltherm 800 was investigated by five different cases. The investigation was presented under total volume fraction 4% for all nanofluids and mixing fraction 50:50 for the hybrid types in order to facilitate the analysis and compare various results at the same conditions. Those cases and their comparisons were solved using MATLAB Symbolic tools under turbulent flow regime and variable inlet temperature to present wide domain behavior for the energy and exergy efficiency, Nusselt number, heat transfer coefficient, and pressure drop, whereas the analytical solution of the energy balance equation was taken from the literature and improved to cover the mentioned cases. Moreover, the results were compared with previous researches that used different thermal fluid and showed high accuracy behavior with low deviation. Therefore, the findings showed that Al2O3 and CeO2 hybrid nanofluids were more efficient than using of both Al2O3 and CuO hybrid nanofluids and any mono nanofluids contain the same nanoparticles. The maximum enhancement of thermal and exergy efficiency of using Al2O3 and CeO2 hybrid nanofluids was 1.09% and 1.03%, respectively, whereas it was enhanced by 167.8% and 200.7% for the Nusselt number and heat transfer coefficient, respectively. Also, the hybrid nanofluids have higher advantage over the mono nanofluids by presenting lower pressure drop values. Finally, the assessment of efficiency variation affected by thermal properties of the nanoparticle was presented under optimum temperature equal to 575 K.