Numerical investigation of hydrothermal performance and entropy production rates of rGO-CO3O4/H2O hybrid nanofluid in wavy channels using discrete phase model

Abstract

This work investigates numerically the turbulent hydrothermal performance and the entropy production rate (EPR) of rGO-CO3O4/H2O hybrid nanofluid “reduced-graphene oxide/cobalt oxide (rGO-CO3O4) nanoparticle with water as a base fluid” flow in two-dimensional straight, serpentine, and furrowed wavy channels. Both discrete phase and k−ω models were used in ANSYS Fluent package to simulate the turbulent hybrid nanofluid flow based on the finite volume method. The effect of Reynolds number (5.0×103≤Re≤3.0×104), nanoparticle volume ratio (0≤VR≤0.2%), amplitude (0.2≤A*≤0.6), and wavelength (0.7≤λ*≤1.4) on the hydrothermal and EPR were examined. The results revealed that the average Nusselt number (Nu), pressure drop (dP), and EPR due to the viscous dissipation in terms of viscous entropy production rate (VEPR) in wavy channels are higher than that of the straight channel and decrease with increasing λ*. However, the opposite is the case for EPR due to temperature gradient in terms of thermal entropy production rate (TEPR). The normalized (referencing straight channel) dP,Nu, TEPR, and VEPR in the serpentine wavy channel at Re=1.5×104, λ*=0.7 and A* = 0.2 are 16.83, 1.59, 0.76, and 5.93, respectively. The corresponding values at Re=1.5×104, λ*=1.4 and A* = 0.2 are 7.70, 1.34, 0.85, and 3.67, respectively. Furthermore, Nu,dP, and VEPR increase with increasing A*. However, the opposite is the case for TEPR. Finally, the thermal effectiveness number due to geometry modification (Igeo) obtained from combined first and second thermodynamic laws shows that the wavy channels are more effective compared with the straight channel.