Thermo-viscous influence on the mechanical seal performance in a reactor coolant pump (RCP)

Abstract

The mechanical seal performance in reactor coolant pump (RCP) is of great importance for the efficient and safe operation of primary loop in nuclear power plant. The sealing medium filling inside the seal encounters strong thermal gradient. In this paper, thermo-viscous effect on sealing characteristics with two typical mechanical seal faces, namely the tapered-end-face and wave-tilt-dam, is numerically studied, by introducing the temperature-viscosity equation according to the real physical properties of the sealing medium. Performance of mechanical seal with two different temperature-viscosity equations are compared. In addition, the influence of thermo-viscous effect on cavitation is also analyzed. It is revealed that the temperature-viscosity variation significantly influences the internal flow field, temperature field, two-phase distribution, and the opening force as well. With low base film thickness, the temperature difference will reduce 58% as considering the thermal effect on viscosity, and the difference in leakage may be as high as 43%. Also, the prediction of cavitation under small film thickness indicates that the thermo-viscous effect decreases the cavitating area. This work contributes to the mechanical seal design and performance prediction by assessing the thermal influences on viscosity of seal medium, and meanwhile revealing the effect on the possible cavitation event.