This study introduces a novel experimental approach to evaluate the impact of surface roughness and wettability (hydrophilicity and hydrophobicity) on the thermal performance of jet and spray cooling systems, focusing on electronic cooling applications under single-phase flow condition. Unlike previous research, which primarily emphasized fluid dynamics or system configurations, this work integrates advanced surface characterization techniques (using AFM and contact angle analysis) with the optimization of system parameters (nozzle diameter, flow rate, and heat flux) via the Taguchi method. Hydrophobic surfaces are created using Rust-oleum spray coating, while hydrophilic surfaces are treated with FeCl₃ solution. The cooling system employed four suction pipes near the surface to ensure proper fluid distribution and outflow. Experimental optimization using the Taguchi method revealed that, in jet cooling mode, increasing the nozzle diameter and fluid flow rate while reducing the nozzle height from the surface significantly improved cooling performance. Variance analysis indicated that fluid flow rate had the highest contribution to performance, accounting for 37.74 %. Spray cooling demonstrated superior efficiency, reducing surface temperature by up to 4K at high heat fluxes, owing to improved surface coverage and enhanced fluid-surface contact. Hydrophilic surfaces further enhanced heat transfer, achieving a reduction in surface temperature by about 2K, particularly under spray cooling. In contrast, hydrophobic surfaces decrease the convective heat transfer coefficient near to 50%, primarily due to reduced surface-fluid contact area and increased fluid sliding effects.

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