Turbulent Transport Characteristics and Mechanistic Insights into Particle Suspensions with Distinct Photoresponses: A Comparative Investigation

An accurate comprehension of the transport laws governing particle-laden fluids holds substantial significance for efficient energy transfer and conversion processes. Nevertheless, current researches exhibit an ambiguous understanding of the transport characteristics of particle suspensions with varying response ranges under photoirradiation, particularly at high shear rates, necessitating further clarification. Herein, in a horizontal continuous pipe, the evolution of flow resistance characteristics of particle suspensions with varied light responses (i.e., TiO₂, ZnO, and SiO₂) was carefully investigated. The effects of the particle type, concentration, Reynolds number, and light irradiation time on turbulent transport resistance were analyzed. Additionally, with reference to engineering practice, the transport processes of particles in mixtures containing various sacrificial reducing agents (i.e., CH₃OH, C₂H₅OH, C₆H₅Na₃O₇, and C₆H₁₂O₆) were further discussed. By integrating analyses of particle morphology, interfacial physicochemical properties, sensible heat conversion, and agglomeration kinetics, it was concluded that the drag reduction mechanisms of particle suspensions differ significantly under nonirradiation and photoirradiation conditions. The former is dominated by the particle size effect, which modulates the dissipation rate of turbulent kinetic energy. The latter, by contrast, induces variations in particle interfacial wettability and temperature elevation within the particle suspension under continuous photoirradiation, thereby further impacting transport energy consumption and pressure drop. It is anticipated that our findings could offer a theoretical guidance for efficient energy transfer and material conversion in chemical reactions involving the transport of photoresponsive particle suspensions.