Numerical investigation of electrocoalescence-induced fluid demixing between parallel plates

Abstract

The efficient separation of dispersed phase droplets from a continuous phase in multiphase flow systems is essential for industries such as petroleum refining, pharmaceuticals, and food production. Conventional methods, relying on gravitational and buoyancy forces, are often inadequate for small droplets due to their weak influence. Electrocoalescence, utilizing electrical forces to enhance droplet coalescence, has gained attention as a promising alternative. However, most studies have focused on simplified models, limited electrical potentials, or axis-symmetric configurations, overlooking the effects of varying electrical potentials on droplet behavior in complex flows. This study bridges that gap by developing a numerical solver that couples the phase-field method with the Navier-Stokes equations to simulate electrocoalescence of two-dimensional droplets in laminar phase flow between parallel plates. The solver provides detailed insights into multiphase flow dynamics, including contact line behavior and interface tracking under different electrical potentials. The novelty of this work lies in its systematic evaluation of how varying electrical potentials affect droplet deformation, separation time, and interface dynamics, which are often not fully addressed by standard commercial solvers. The findings indicated that increasing electrical potentials from 50 kV to 100 kV leads to droplet deformation, with the droplet deformation index (DDI) increasing from 0.35 to 0.52. Additionally, phase separation time decreases by 20%, from 0.15 seconds to 0.12 seconds, as electrical potential increases. The increasing electrical potentials lead to asymmetric droplet shapes and instability, accelerating separation by disrupting the formation of stable liquid bridges. These findings offer valuable insights into optimizing electrocoalescence processes for industrial applications. In this study, a multi-objective optimization process was conducted using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), with the aim of minimizing droplet deformation and phase separation time. The optimization results revealed that the ideal initial contact angle for minimizing deformation was 123.45°, while the optimal contact angle for minimizing separation time was 145.67°. These results highlight the potential of optimizing system parameters to improve the efficiency and stability of electrocoalescence processes in various industrial applications.The current study provides a deeper understanding of the interaction between electrical forces and multiphase flow dynamics, laying the groundwork for advancements in phase separation technologies across various industries.

Keywords

• multiphase flow
• electrocoalescence
• phase separation
• numerical modelling
• phase field method

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