Thermo-hydraulic performance assessment of mono and hybrid ceramic nanofluids in flat plate solar collectors: a CFD-based study

Ceramic nanoparticles have shown great potential in enhancing renewable energy systems and thermal management systems. This study investigates the thermo-hydraulic performance of mono and hybrid nanofluids synthesized by dispersing Titanium diboride (TiB₂), Boron carbide (B₄C), and a hybrid TiB₂: B₄C blend (20:80 weight ratio) into propylene glycol-water (PG: W, 20:80 wt.%) base fluid, with a fixed nanoparticle concentration of 2 wt.%. The thermophysical properties of the nanofluids were evaluated at three inlet temperatures: 298.15 K, 308.15 K, and 318.15 K. A three-dimensional numerical model was developed using ANSYS 2021R1 to simulate flow behavior over a Reynolds number range of 100–900. Key performance indicators included outlet and surface temperatures, heat transfer coefficient (h_tc), Nusselt number (Nu), pressure drop (ΔP), absorbed heat (Q_abs), and energy efficiency (η_eng). At 298.15 K, the TiB₂: B₄C hybrid nanofluid demonstrated a 4.38 % improvement in thermal conductivity over the base fluid (PG:W) and a 26.3 % reduction in viscosity compared to B₄C, demonstrating a balanced enhancement of thermal and flow properties. While B₄C exhibited the highest heat transfer coefficients (12–19 % above PG:W and 4.8–10.4 % higher than TiB₂:B₄C), its high viscosity resulted in increased pumping demands. In contrast, the hybrid nanofluid achieved energy efficiency up to 10 % higher than PG:W while remaining within 2–5 % of B₄C's performance. With increasing temperature, all nanofluids exhibited a ∼78 % reduction in pumping power due to decreased viscosity, with TiB₂:B₄C consistently requiring the lowest pumping energy, up to 60 % less than B₄C. These results highlight the TiB₂:B₄C hybrid nanofluid as a thermally efficient and energy-saving alternative for practical heat transfer systems.