Thermo-hydraulic perspectives of non-Newtonian channel flow with active flow modulation: A CFD study

Abstract

This study aims to numerically explore the influence of active flow modulators on thermo-hydraulic characteristics of channel flow with non-Newtonian power-law fluid, also known as Generalized Newtonian Fluid (GNF). The upper and lower walls of the channel under consideration are heated isothermally, while at the inlet a channel flow with Poiseuille fluid flow profile is imposed, influenced by an active flow modulator, namely an oscillating blade positioned along the channel centreline. Within the Arbitrary Lagrangian-Eulerian framework, the associated flow and thermal fields are solved using the Galerkin finite element method. The channel's hydrodynamic state is assessed in relation to the Reynolds number variation (50 ≤ Re ≤ 150), for various non-Newtonian fluids as represented by the power-law index variation (0.6 ≤ n ≤ 1.2). Furthermore, the corresponding dimensionless oscillating frequency (N*) and channel blockage ratio (B) are changed in order to investigate the impact of the flow modulator. The evolution of temperature and flow fields as well as heat transfer performance metrics, such as local, spatially and time averaged Nusselt numbers, have all been taken into consideration while evaluating the characteristics of the system. The obtained results indicate that the Reynolds number and associated flow obstruction have a significant impact on the flow modulator's efficacy. For pseudoplastic fluids (n = 0.6), thermal oscillations can be observed, which are brought on by the oscillating modulator's periodic shedding of vortices. While pseudoplastic fluid might improve heat transfer, especially at greater blockage ratios, the situation is reversed when the associated pressure drop is taken into account.