Numerical Modeling of Wax Deposition Using SPH

Phase change and deposition of solid particles in liquid flows are undesirable in some natural and industrial processes and can be hazardous in some cases. Considering the difficulties involved in petroleum exploitation in deep waters, precipitation and deposition of wax crystals in oil and gas pipelines are real concerns. This is due to the fact that during production, oil is exposed to more intense temperature gradients (the dominant mechanism in wax deposition) and as a result its heavier components migrate to the solid phase called deposit. According to various studies, wax layer deposited on a surface behaves like a gel with a complicated morphology. The gel behaves like a moving boundary porous media surrounding an internal flow. In order to model the presence of wax formation on the internal walls of the channel, a source term is added to the Darcy equation. It is assumed that other wax formation mechanisms such as shear dispersion and Brownian diffusion are neglected. Wax deposition simulation in channel, involves solution of the continuity, momentum, energy, species transport, and phase equilibrium equations. In the present study, the governing equations are solved using Smoothed Particle Hydrodynamics (SPH) method. Also, an algorithm for solid liquid phase equilibrium calculations is proposed and compared with the experimental Wax Appearance Temperature (WAT). Both temperature and species distributions are compared with analytical solutions available for some simplified cases.