Combined effect of a corrodible material and acidic fluid on flow boiling crisis

Abstract

The heat transfer surface condition is one of the factors that greatly affects not only boiling heat transfer but also boiling crisis. In particular, in the case of a metal that is easily corroded, oxide formed on the surface of the metal during boiling may affect the critical heat flux (CHF). The oxide has conflicting effects, as it can enhance the CHF by improving the surface wettability but also simultaneously reduce it due to low thermal conductivity. In this research, CHF experiments were carried out under DI water and acidic fluid conditions using SA508 carbon steel, a metal susceptible to corrosion. In the case of pre-oxidized SA508, a 25 to 53 μm magnetite layer was formed on the surface preventing additional oxidation, resulting in a constant CHF. In addition, surface observations directly confirmed that the pre-oxidized layer remained even after a long period of boiling. Conversely, for fresh SA508, two oxide layers were found to form after the experiment. As the boiling time increased, the CHF of the fresh SA508 decreased, which is considered to be related to an increase in the thickness of the magnetite layer. © 2023 Elsevier Ltd