Experimental research on the thermal hydraulic characteristics of sodium boiling in an annulus

Thermal hydraulic characteristics of sodium boiling are significant in the safety analysis for the sodium cooled fast reactor, one of the Generation IV reactors. However, the knowledge on the mechanism of sodium boiling is quite limited. In this study, boiling experiments on sodium flowing through an annulus are performed. The annulus is of 1000 mm length, 8 mm inner diameter and 12 mm outer diameter. The heat flux varies from 80 to 500 kW/m2, with inlet subcooling from 63 to 285 °C, inlet flow velocity from 0.02 to 0.5 m/s and system pressure from 3.67 to 103 kPa. The boiling phenomena, two phase friction pressure drop and boiling heat transfer coefficient are investigated. Correlations for the two-phase friction multiplier factor ϕl2 and boiling heat transfer coefficient are proposed, respectively. Predicted results show good agreement with the experimental data.