EXPERIMENTAL STUDY ON THE EFFECT OF NaOH AND Na3PO4 ON SiO2 NANOFLUID SATURATED POOL BOILING CHF

抄録

In-vessel retention through external reactor vessel cooling (IVR-ERVC) is one of the key severe accident mitigation strategies, which takes away the heat of melt through the reactor pressure vessel external cooling and prevents the leakage of the radioactive materials. Studies have shown that SiO₂ nanofluids can significantly improve the critical heat flux (CHF) of the heating surface, and applying nanofluids to external cooling of pressure vessels can reduce pressure vessel failure risk. Sodium hydroxide (NaOH) as an additive in the spray water would change the chemical environment of cooling fluid, so this work investigated the effects of NaOH and Na₃PO₄ solution at PH 9.7 on SiO₂ nanofluid saturated pool boiling CHF under different concentrations and different downward heating surface orientation angle. The experimental results show that under the same concentration, the CHF of SiO₂ nanofluid based on NaOH and Na₃PO₄ solutions are nearly the same. Compared with SiO₂/H₂O nanofluid, the reduction in CHF is 15% at 0.01vol%. Same as SiO₂/H₂O nanofluid, CHF increased with the orientation angle of heating surface in NaOH and Na₃PO₄ environment. What’s more, scanning electron microscope (SEM) images were taken on the nanoparticle deposition layer formed on heating surface. The roughness, thickness, and the pattern of the nanoparticle deposition layer was different under different chemical environment, which lead to a decrease in CHF.