Performance analysis of mechanical seal of residual heat-removal pump based on thermal-fluid-structure coupling

BackgroundThe Residual Heat-removal Pump (RRA pump) is a key component of the nuclear reactor, which is responsible for removing decay heat from the reactor core and maintaining thermal equilibrium in the primary loop during reactor shutdown. Its sealing performance and structural integrity directly impact the safe and stable operation of the nuclear power system. Therefore, it is essential to assess the sealing performance of the RRA pump's mechanical seal under thermal shock conditions.PurposeThis study aims to evaluate the leakage characteristics of the mechanical seals on the RRA pump using numerical simulation methods.MethodsA three-dimensional model of the RRA pump and its mechanical seals for a specific nuclear power plant was established. The RRA pump was a single-stage horizontal centrifugal pump with a rated speed of 1 495 r·min-1 and a medium design temperature of 15~180 ℃. The advanced unstructured polyhedral mesh technology of the commercial software Fluent Meshing was employed to discretize the RRA pump and mechanical seal. Conjugate heat transfer calculations were then performed using ANSYS Fluent to obtain the flow field and temperature field distributions within the RRA pump and mechanical seals under specific operating conditions. Finally, based on a one-way fluid-structure interaction methodology within the ANSYS Workbench platform, the analysis of the mechanical seal was conducted to obtain the axial deformation of the mechanical seal. and the leakage characteristics in the primary sealing regions were further investigated.ResultsDue to the frictional heat generation between the faces of the stator and rotator, along with the erosion caused by the cooling water, the temperature on the sealing faces of the rings increases and then decreases radially. This leads to a leakage path with a shape that is narrow in the middle and wider at both ends. Given that the maximum clearance width is 1.24 μm, the calculation yields a conservatively estimated leakage rate of 1.41 drops per minute.ConclusionsThe calculated leakage rate of the mechanical seal in this study shows well agreement with the actual operational conditions of the nuclear power plant, and this study provides a numerical simulation method for accurately analyzing the sealing performance and leakage of the RRA pump in the reactor primary loop, offering significant practical engineering implications.