Bi-directional integral pumping devices for dual mechanical seals: Influence of mesh type on accuracy of numerical simulations

Abstract

A numerical study is conducted to simulate the performance of barrier fluid flow through a bi-directional dual mechanical seal with an integral radial pumping ring. Standard K-ε model is implemented as a turbulence model. Multiple Reference Frame approach is implemented to model the rotation of the pumping ring. The present study is a sequel to a previous companion work done in the area of visualization of barrier fluid flow. Improvements to the previous work depended on two aspects. First, a multi-block hybrid (tetra, prism and hexa) mesh is used where it is aimed to reduce numerical false diffusion by orienting the cells to be aligned with flow direction as much as possible. Second, expanding model’s boundaries to include inboard sealing faces. The numerical results are validated against Q-ΔP curves produced from experimental tests where an experimental setup is constructed, and appropriate instrumentation is employed to measure the pressure, temperature, and flow rate of the barrier fluid.Moreover, implementation of two spatial discretization schemes is illustrated to verify the numerical performance of each method. Second order Upwind and QUICK (Quadratic Upstream Interpolation for Convective Kinematics) schemes are used for the discretization of convective terms. The validity of implementation of each method is investigated since higher-order methods are known to be more computationally expensive but their accuracy are higher. The results by the hybrid mesh indicate that the use of the Second-order scheme provides more accurate prediction of Q-ΔP curves than the previous companion work. Moreover, the impact of using the QUICK scheme is the increased computational time while providing slightly more accurate Q-H curve relative to the second-order scheme.Finally, expanding model’s boundaries to include inboard sealing faces revealed that closed barrier fluid circulation takes place in the vicinity of the inboard sealing faces indicating poor renewal of the barrier fluid contained within this zone compared to the outboard sealing faces. Keywords: Integral pumping device, Dual mechanical seals, Barrier fluid flow, Hybrid mesh, CFD