Unsteady study of molten salt pump conveying mediums with different viscosities

•A modeling scheme is proposed to solve the difficulty of high temperature test.•The pump loss mechanism for conveying different viscosity medium is proposed.•The relationship between unsteady flow field and pump performance are revealed. Molten salt pumps are key equipment used in solar high-temperature heat transfer and heat storage systems. As it is difficult to use the high-temperature molten salts for experimental tests, and significant changes in the molten salt viscosity affect the pump performance, a modeling scheme is proposed and verified in this study. An unsteady flow field simulation inside the pump is conducted for molten salt pump conveying mediums with different viscosities. To study the unsteady characteristics of the flow field inside the pump, the angle α between the blade and the volute tongue is defined. It is found that the shape of the pressure curve at the volute tongue is related to the medium viscosity as α changes. The position of the blade affects the velocity distribution inside the volute significantly. Moreover, the shapes of the performance curves H-Q, N-Q, η-Q are greatly affected by the viscosity of the molten salt. The mechanism of flow loss with different viscosities mediums inside the pump is revealed. The research results provide an important reference for the further studies of molten salt pump.