Energy and exergy analyses of nanofluid-filled parabolic trough solar collector with acentric absorber tube and insulator roof

Abstract

Increasing the energy demands has encouraged the development of novel archetypes solar receiver employed in sustainable energies. Parabolic trough solar collectors (PTSCs) attract researchers due to high thermo-hydraulic performance. The main goal of the present investigation is to design an efficient PTSC filled with nanofluid numerically using the finite volume method. The other aim is to compare the obtained numerical results of nanofluid simulation in PTSC the using single-phase mixture model (SPM) and the two-phase mixture model (TPM). In the first step, influences of using SPM or TPM on nanofluid simulation in absorber tube are investigated. Then, the influences of using an insulator roof and an acentric absorber tube on energy and exergy efficiency are studied. Consequently, in this step the optimum configuration is introduced. In the last step, effect of different nanofluid parameters (different volume fraction and various nanoparticles diameters) on the optimum configuration is investigated using TPM. Based on obtained results, for both conventional and novel PTSC, the obtained Nusselt number employing TPM simulation is more than that of SPM simulation. Also, it is found that using the novel PTSC leads to higher Nusselt number, energy efficiency, performance evaluation criteria, and outlet temperature for all studied Reynolds numbers. According to the results, the energy and exergy efficiencies of novel PTSC with an insulator arc angle of 70° and acentric value of 20 mm filled with nanofluid having a diameter of 20 mm and nanoparticles volume fraction of 1% are about 73.10 and 31.55% and are the maximum obtained efficiencies in the present study.