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Fracking (fracturing) is of great importance for enhancing oil and gas production from low permeability reservoirs. Since in fracking fluid, suspension of sand particles are used, the erosion failure of fracturing equipment has become an increasing concern. Accordingly, investigation of erosion of commonly used fittings such as ball seats in order to decrease its adverse consequences has attracted considerable attentions. Although the erosion wear of gas-solid flows in the pipe sudden expansion was investigated in the literature, the effect of particle size, ball seat shape and the contraction configurations on the erosion-induced wear is not fully understood. This study is aimed to explore the most erosion-resistant configuration of a ball seat under various operational conditions. A CFD model is used and a wide range of geometries are investigated. The studied configurations are categorized in three main groups including single cone, double cone and curved cone. In each category, different cone angles and curve styles are considered. The results showed that, among the single cone ball seats, the cone angle of 15° is the most erosion-resistant configuration. It was also shown that the third-order curve style cone has the best erosion performance.

Since curved pipes are widely used in industrial equipment, predicting multiphase flows in these geometries is of great importance. In the present study, a computational model for predicting the velocity profile is developed and used to study the developing turbulent gas-liquid flows in curved pipes. In order to discretize and solve the three-dimensional steady-state momentum equations, the finite volume scheme on staggered grids besides central difference and QUICK scheme have been used. Moreover, the k-ε model is employed to reflect the nature of turbulence in the flow. In order to address the needs for sooner convergence and convenient mapping of the physical domain, the computations have been performed in a new toroidal coordinate system. Particle tracking has been done using Lagrangian approach in which two-way coupling regime is considered. In terms of validation, the numerical simulation results for the straight duct (infinite curvature), have been compared with the analytical solution and previous experimental results. Moreover, injection of particles through the flow indicates that, in each section of the bend, trade-off between centrifugal and pressure gradient forces plays a key role on particles motion. In last section, the effects of particle diameter and bend curvature on particle motion have been examined.

Sand particle erosion is the main cause of the failure of bends in the natural gas pipelines. The rapid progress of computational power and modern numerical methods has provided the opportunity for developing realistic simulation of the erosion process. The goal of this paper is to predict the sand erosion rates with the use of computational fluid dynamics in the gas/solid flows in the plugged tees and standard elbows. For this purpose, the Eulerian-Lagrangian approach was used. To simulate the flow, the SIMPLE algorithm and the k-ω SST turbulence model were used. Particles were injected into the inlet pipe with different sizes. To predict more realistic results the Grant and Tabakoff stochastic rebound model was applied and the Oka model was used to calculate erosion. The results showed that, the use of plugged tee instead of a standard elbow would reduce the erosion rate only for fine particles. Also, for them, by increasing the plugged length the pipe will experience less erosion. For coarser particles, however, the vortex created in the plugged section did not affect the particles velocity; therefore, the erosion rate was not reduced.