One-dimensional model of hydrogen distribution in confined space based on Froude number

Abstract

Some hydrogen mitigation study programs have been conducted to figure out the hydrogen distribution characteristics and provide useful information for codes development and validation. However, there is a lack of models with direct relations between hydrogen distribution and a non-dimensional parameter which governs the hydrogen flow, such as Froude number. This deficiency will lead to lack of understandings of the dominated force regimes. Therefore, in this paper, one-dimensional model of hydrogen distribution is built, based on Froude number. With theoretical study and fitting method, a semi-empirical formula is given, which is verified by experimental data obtained from pure plume conditions and buoyant jet conditions. Finally, this newly-built model is employed in typical accidents analysis. Three typical Froude numbers which are based on PANDA and TOSQAN study, are selected to get much closer to the real accidents. According to the evolution of helium concentration and concentration distinction, it can be found that obvious stratification may take place in the middle part and lower part of the containment model, while it turns to be more uniform in the top, corresponding to these three Froude numbers of 3.8, 17 and 280. Moreover, the higher the buoyancy is (Fr = 3.8), the more uniform the helium distribution throughout the containment model will be. The medium momentum will lead to significant stratification, which needs to be paid much attention in reactor design and accident mitigation.