Experimental investigation on nanofluid saturated pool boiling CHF with different chemical additives

The effect of the chemical additives on nanofluid saturated pool boiling Critical Heat Flux (CHF) for downward facing surface is investigated through a series of experiments. When NaOH or Na₃PO₄ solutions at a pH of 9.7 are utilized as the base fluid, there is a 10 % decrease observed in the CHF of SiO₂ nanofluid. However, these solutions have minimal effect on the CHF of TiO₂ and Al₂O₃ nanofluids. To further explore the mechanisms of how chemical additives impact the nanofluid's CHF, the particle size distribution and zeta potential of nanofluid, the morphology and size of the nanoparticle, and the morphology, roughness and thickness of nanoparticle deposition layer were measured in the chemical environment. The findings demonstrate that the chemical environment decreases both roughness and thickness of the SiO₂ nanoparticle deposition layer, thereby lowering its wickability and nucleation site density, ultimately leading to a decrease in CHF. It is recommended to use Na₃PO₄ as a chemical additive of the nuclear reactor spray system and Al₂O₃ nanofluid as the heat transfer fluid to improve the safety of nuclear reactors.