Thermal performance and pressure drop for solar Particles

Abstract

Particle-based heat transfer fluids offer transformative potential for next-generation Concentrated Solar Power (CSP) systems but face unresolved challenges in balancing thermal efficiency against hydraulic losses. This study experimentally characterizes the thermal performance and pressure drop of three industrially relevant particles—silica sand, sintered bauxite, and engineered ceramic mix—under concentrated irradiance (800–1000 W/m²) and flow velocities (0.5–3.0 m/s). A modular solar simulator facility measured Nusselt numbers (Nu) and dynamic pressure drops (ΔP) while controlling particle mass flow (5 g/s) and air velocity, with instrumentation uncertainties rigorously quantified per GUM guidelines. Results demonstrate bauxite’s thermal superiority, achieving 142.6 Nu at Reynolds number 4500—63.5% higher than silica sand—due to its high conductivity (0.35 W/m·K) and spectral absorptivity (0.92). The ceramic mix delivered optimal hydraulic performance, reducing ΔP by 35.2% versus bauxite at 1.5 m/s through enhanced sphericity (0.94). A novel correlation Nu = 0.597Re⁰·⁶⁵⁴ψ⁰·²⁰¹ predicted experimental data within ±0.23% error, resolving morphology-dependent heat transfer previously unaddressed by classical models. Trade-off analysis revealed bauxite maximizes efficiency at high irradiance (78.2% at 1000 W/m²), while ceramic mix achieves Pareto-optimality at medium flux (71.5% efficiency, 810 Pa ΔP). For commercial deployment, bauxite is recommended for power towers (>800°C), ceramic mix for parabolic troughs, and sub-200μm particles should be avoided to control pressure losses. This work provides the first physics-based selection framework for particle receivers, advancing toward cost-competitive CSP with thermal storage