Effect of vertical heat exchange tube/tube-bundle condensation on aerosol diffusiophoretic deposition

During a severe accident, substantial amounts of radioactive aerosols are released into the containment. Upon activation of the Passive Containment Cooling System, these aerosols are driven by diffusiophoresis toward condensing heat exchange surfaces, thereby altering the distribution of radioactive inventory within the containment. This study experimentally investigates aerosol diffusiophoresis under single-tube and tube-bundle condensation conditions. A series of experiments on aerosol diffusiophoresis were conducted under systematically varied steam mole fractions, condensation rates, and system pressures, with real-time monitoring of the spatial aerosol concentration. The results indicate that particle size has a negligible effect on the diffusiophoresis velocity, an increased steam condensation rate enhances the deposition, while a reduction in steam mole fraction inhibits it. A higher steam density inhibits the diffusiophoresis velocity. Furthermore, the study investigates diffusiophoresis under both single-tube and tube-bundle condensation conditions. The effective deposition area coefficient (α), correlated with condensation rate and steam mole fraction, is proposed to modify the classical model, thereby improving its predictive accuracy. The study proposed the effective deposition area coefficient α, related to both the steam condensation rate and steam mole fraction, to modify the classical diffusiophoresis model. This correction effectively reduces the deviation between experimental data and model predictions, significantly improving the accuracy of diffusiophoresis decay constant forecasts under strong heat-sink tube-bundle condensation conditions. The findings provide essential experimental data and a refined model for assessing post-accident radioactivity distribution within the containment.