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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° to 7°. 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. [ABSTRACT FROM AUTHOR]

An experimental study of nucleate pool boiling is conducted on the GNP/Ni-Al2O3 (GNP-graphene nano particle) nano-composite coated copper surfaces at atmospheric pressure using distilled water (DI) as boiling fluid. The microporous coated surfaces are fabricated using hybrid method (electrochemical deposition of GNP and nano-composite coating of Ni-Al2O3). A modified surface structure is generated as a result of this deposition, and different surface morphological parameters of this modified structure, such as surface structure, roughness and wettability, are investigated. Results show the enhancement in boiling heat transfer coefficient (BHTC) and critical heat flux (CHF) in nano-composite coated surfaces compared to the bare Cu surface. The improvement in boiling performance is mostly attributable to the enhancement of roughness and wettability as well as the higher thermal conductivity of the GNP/Ni-Al2O3 nano-coating. The highest CHF of 2217 (kW/m2) and BHTC of 112.83 (kW/m2K) is found in case of composite nano-coated superhydrophilic (CNCS) surfaces, which are 104% and 123% more than the bare Cu surface. High-speed visualization is used to conduct a quantitative investigation of the dynamics of bubble, including active bubble site density, emission frequency of the bubble, bubble departure diameter and their impact on the performance of pool boiling heat transfer. [ABSTRACT FROM AUTHOR]