Numerical investigation of a tree-like mini-channel disperser guided by constructal design with laminar nanofluid flow
摘要
In this numerical study, we investigate the simultaneous augmentation of a mini-channel heat sink by using constructal theory based branching and a graphene nanoplatelet (GNP) nanofluid. Five levels of branching are compared in reference to a smooth channel under fixed global constraints and a constant heat flux. We examine the Nusselt number (Nu), the friction factor (f), and the Thermal Performance Factor (TPF)methods for water and in a nanofluid and quantify the thermo-hydraulic trade-offs. This mini-channel heat sink, having a base geometry of 100 mm × 75 mm and channel width and height of 3 mm and 1.5 mm, respectively, and a constant inlet hydraulic diameter of 2 mm, was created in SolidWorks and simulated in ANSYS Fluent at constant-state, laminar flow rate (Re = 100–1500). Constructal scaling applied with a width and length reduction factor of 2–1/3, developed four constructal configurations of progressively scaled channels. For the case of water alone, the optimized constructal configuration yielded a peak Nusselt number (Nu) of around 780 at Re ≈1500, or a 35% increase compared to a smooth channel baseline (≈580). Addition of nanoparticles at the optimum concentration of 0.1% further increased the convective efficiency: Nu by a further 12–15% and the Thermal Performance Factor (TPF) by 25–30% at moderate Re (500–800), though the friction factor (f) increased by 5–7% due to enhanced effective viscosity. Entropy generation analysis revealed that, at greater Re, the total entropy production was down by around 12%, and the optimised constructions had an 8% decrease in the entropy generation number (Ns) in addition to a rise in the Bejan number. Flow field visualizations ensured improved temperature uniformity and streamlined velocity distribution in spite of some localized hotspots being present. Overall, the results show that the combined use of constructal geometry and nanofluids considerably boosts both the heat transfer and the second-law performance of mini-channel dispersers, hence promising new directions in high-performance, physically compact thermal management systems.