The external performance and internal flows for water and mol-ten salts in a molten salt pump were researched experimentally and numerically. As water being delivered, the H–Q, P–Q and g –Q performance curves estimated with the unsteady flow model have been compared with those measured, and the unsteady flow veloc-ity profiles near the volute tongue have been validated with the PIV observation. The relationships between the pump performance (including head, shaft power, efficiency, distribution and pulsation amplitude of velocity and pressure) and the physical properties of fluids (including viscosity and density) have been revealed. The major findings are as follows:

    (1) The numerical results agree well with the experimental results. Numerical simulation is an economical and feasible method by which the performance of molten salt pump can be predicted. The pressure distribution trend is essen-tially similar in spite of the viscosity difference. The static pressure increases from Sections I–VIII. For same viscosity, the higher the density is, the higher the pressure is in volute. The best efficiency point moves towards the high flow rate with the increase of viscosity.

    (2) The power consumption due to viscous friction increases with the increase of viscosity, which leads to the decrease of head. The shaft power increases with the increase of den-sity and viscosity. Compared with delivering water, the head and efficiency show less change for delivering low viscosity fluids ( l < 0.044 Pa?s). Therefore, the head and efficiency doesnot need to be corrected. Conversely, for delivering high viscosity fluids ( l > 0.044 Pa?s), the head and efficiency decrease significantly.

    (3) The velocity distribution in flow fields of low viscosity fluids is similar to that of water, whereas for high viscosity fluids it presents a noticed difference from that of water. The inter-ference effect of blade on the velocity is obvious, and the clo-ser the position to the impeller, the larger the pulsation amplitude of velocity. The increased viscosity of fluids can suppress the pulsation in velocity. For any viscous fluids, on Section VIII, the circumferential velocity approaches the maximum value when the blade-tongue angle is 30?, and the radial velocity reaches the maximum and minimum value when the blade-tongue angle is 40? and 18?, respec-tively. The results have reference significance on the devel-opment of pump with lower flow induced vibration.