Enhanced pool boiling heat transfer characteristics on microstructured copper surfaces coated with hybrid nanofluid

High heat flux devices necessitate efficient heat dissipation systems, with pool boiling emerging as a promising method. Leveraging advancements in nanoscience, this study investigates the enhancement of heater surface characteristics for pool boiling through experimental means. Three bare copper surfaces are coated with a hybrid nanofluid comprising copper-based carboxylic functionalized multi-walled carbon nanotubes and distilled water at concentrations of 0.3, 0.6, and 1.0 mass% using the spin coating technique. Contact angle measurements reveal superhydrophilicity across all surfaces, ranging from 14 degrees to 7 degrees. The 1.0 mass% coated surface exhibits significant improvements in boiling heat transfer coefficient and critical heat flux, reaching 143 W m-2 K-1 and 2206 W m-2 K-1, respectively, representing increments of 324% and 204%. Visualization of bubble dynamics demonstrates enhanced surface roughness and active nucleation sites, leading to early bubble detachment under low heat flux conditions. Bubble sizes ranging from 0.6 to 1.6 mm indicate smaller diameters compared to bare copper surfaces, facilitating rapid heat dissipation due to more nucleation sites and proper nanofluid adhesion. The microporous surfaces prepared exhibit exceptional performance, offering potential applications in boilers, heat pipes, and various heat transfer systems.