Characterizing thermal efficiency and entropy generation of Sisko nanofluids in parabolic trough solar collectors: A comparison between three carbon-based nanoparticles

The primary objective of this work is to compare the effect of adding three different carbon-based nanoparticles (graphene, graphene oxide, and SWCNT) on the parabolic trough solar collector (PTSC)’s efficiency by considering Sisko nanofluids with ethylene glycol taken as the base fluid. The mathematical modelling took into consideration the impact of viscosity dissipation, solar thermal radiation, heat source/sink, and a constant slanted magnetic field. The controlling PDEs and the bounding constraints are attenuated into an ODE system upon the application of an appropriate similarity transformation. A numerical solution to the obtained ODE system is found by using the shooting technique via bvp4c. The effects of different parameters controlling the flow of the Sisko nanofluids are studied on the nanofluid’s velocity, temperature, entropy, skin friction coefficient, and local Nusselt number. It is found that the skin friction coefficient is increased with the Sisko material parameter, nanoparticle concentration, and decreased with the power-law index. While, the local Nusselt number is increased with the power-law index, nanoparticle concentration and is decreased with the Sisko material parameter. Numerical investigations show that the relative increase in the maximum temperature of graphene, graphene oxide, and SWCNT Sisko nanofluid was found to be 8.7308%, 38.4100%, and 47.7266%, respectively. The SWCNT–ethylene glycol Sisko nanofluid was determined to have the highest thermal performance enhancement among the three nanofluids herein.