Experimental study on CHF enhancement of different oxidized surfaces of low carbon steel in nanofluid

Abstract

Considerable research has been undertaken to explore the use of nanofluids for augmenting the critical heat flux in the in-vessel retention (IVR) strategy deployed in reactors, demonstrating significant improvements in CHF. However, it is important to consider the potential bias in previous studies on surface CHF due to the oxidation of low carbon steel, which is commonly used in reactor vessels, in both air and water under real-life conditions. This study represents the initial investigation into the oxidation behavior of low carbon steel in an air environment, followed by subsequent boiling in water. The results indicate that when the mild steel surface is pre-oxidized in air, the CHF value in deionized water decreases. However, this effect is not readily apparent in nanofluids. Consequently, it suggests that CHF under real operational conditions could be lower than anticipated. Additionally, nanofluids significantly increase the CHF of surface, however, the enhancement of CHF for oxidized surfaces in water is not as pronounced, a point which has never been mentioned by researchers. The mechanisms of surface oxidation and nanofluid-induced CHF enhancement are explained. Consequently, this paper provides important reference value for studying the application of nanofluids in IVR accidents.