Synergistic and Antagonistic Effects of Nanoparticle Deposition in Low-Concentration Mono and Hybrid Nanofluids for Pool Boiling Heat Transfer

The ever-increasing heat dissipation requirements of modern high-performance electronics critically demand advanced cooling techniques beyond conventional fluids. Nanofluids have emerged as a next-generation solution for enhanced boiling heat transfer. This study experimentally investigates the pool boiling performance of mono- and hybrid nanofluids at a low volume concentration of 0.01% on a smooth copper surface under saturated conditions using deionized water (DIW) as the base fluid. Three mono nanofluids (Al₂O₃/DIW, Ag/DIW, and GNPs/DIW) and three compositions of hybrid nanofluids with a constant mixing ratio of 50:50 (Al₂O₃-Ag/DIW, Al₂O₃-GNPs/DIW, and Ag-GNPs/DIW) were prepared. The critical heat flux (CHF) and heat transfer coefficient (HTC) were systematically analyzed. All nanofluids enhanced boiling performance compared with deionized water. Among the mono nanofluids, GNPs/DIW achieved the highest enhancement, increasing CHF and HTC by 40.55% and 164.8%, respectively. The hybrid nanofluid Ag-GNPs/DIW exhibited the better overall performance, enhancing CHF and HTC by 53.63% and 209.8%, respectively. Conversely, the Al₂O₃-GNPs/DIW hybrid nanofluid exhibited decreasing heat transfer performance compared with Mono-GNPs/DIW, indicating opposite deposition effects caused by the Al₂O₃ added. Characterization of the surface using SEM, EDS, XRD, contact angle, and porosity detects that GNP deposition creates a protective graphitic layer that minimizes copper oxidation and enhances surface porosity and cavity radius, consequently enhancing boiling heat transfer. In contrast, Al₂O₃ encourages oxide formation and partial pore blockage, which reduced HTC. These results provide new insights into synergistic and antagonistic nanoparticle deposition mechanisms that control the enhancement of boiling in mono- and hybrid nanofluids.