Study on the deposition of impurities and thermal-hydraulic coupling characteristics in the cross-flow of LBE tube bundles

Impurity deposition is a critical operational challange in lead - bismuth (LBE) cooled fast reactors (LFRs). Notably, the LBE cross-flow across the tube bundle represents the local flow pattern in shell-and-tube heat exchangers or helical coiled tube steam generators. To address the lack of numerical models for impurity deposition and its thermal-hydraulic effects in LBE heat exchangers, a DPM-based numerical method is developed to simulate impurity deposition in the cross-flow of tube bundles. The proposed model incorporates both particle deposition and removal processes while accounting for the influence of the deposition layer on heat transfer. Based on the validated numerical method, the influence of working conditions and geometric parameters on the deposition process is compared. The global characteristics and local distribution of the deposition layer thickness are analyzed. The thickness distribution of the deposition becomes more uniform with the increase of the inlet temperature. The inline tube-bundle arrangement and a larger tube pitch will lead to a significant increase in deposition thickness. The maximum thermal resistance at the local position can reach 11.57·10⁻⁶ m²·K/W. Regarding the deposition layer distribution, the average deposition thickness of the first two rows of tubes is significantly higher than that of tubes in other layers. The present study provides theoretical support for the design and safety assessment of LBE heat exchangers.