Pressure drop caused by two‐phase flow of oil/water emulsions through sudden expansions and contractions: a computational approach

Abstract

Purpose -The purpose of this paper is to compute the pressure drop through sudden expansions and contractions for two-phase flow of oil/water emulsions. Design/methodology/approach -Two-phase computational fluid dynamics (CFD) calculations, using Eulerian-Eulerian model, are employed to calculate the velocity profiles and pressure drops across sudden expansions and contractions. The pressure losses are determined by extrapolating the computed pressure profiles upstream and downstream of the expansion/contraction. The oil concentration is varied over a wide range of 0-97.3 percent by volume. The flow field is assumed to be axisymmetric and solved in two dimensions. The two-dimensional equations of mass, momentum, volume fraction and turbulent quantities along with the boundary conditions have been integrated over a control volume and the subsequent equations have been discretized over the control volume using a finite volume technique to yield algebraic equations which are solved in an iterative manner for each time step. The realizable per phase k-1 turbulent model is considered to update the fluid viscosity with iterations and capture the individual turbulence in both the phases. Findings -The contraction and expansion loss coefficients are obtained from the pressure loss and velocity data for different concentrations of oil-water emulsions. The loss coefficients for the emulsions are found to be independent of the concentration and type of emulsions. The numerical results are validated against experimental data from the literature and are found to be in good agreement.Research limitations/implications -The present computation could not use the surface tension forces and the energy equation due to huge computing time requirement. Practical implications -The present computation could compute realistically the two-phase pressure drop through sudden expansions and contractions by using a two-phase Eulerian model and hence this model can be effectively used for industrial applications where two-phase flow comes into picture. Originality/value -The original contribution of the paper is in the use of the state-of-the-art Eulerian two-phase flow model to predict the velocity profile and pressure drop through industrial piping systems.

CFD Numerical and Experimental Investigation of Two-Phase Flow Development After an Expansion Device in a Horizontal Pipe

“…In the gas-liquid flow regime, there are different flow patterns such as bubbly flow, droplet flow, slug flow, stratified wavy flow and stratified flow [22]. Many numerical simulations of gas-liquid two-phase flow have used the Eulerian model in different geometries including sudden expansion [23] and flow in a horizontal tube [24] because it has proven to be more accurate than the VOF and Mixture models [23]. In the Eulerian approach, the liquid phase and vapour phase are both treated as separate continuous phases determined by the volume fraction for each phase [25,32].…”

“…In the Eulerian approach, the liquid phase and vapour phase are both treated as separate continuous phases determined by the volume fraction for each phase [25,32]. The Eulerian two-phase model solves a set of two-phase differential equations for each phase, so it is the most complex of the two-phase models [23]. Consequently, the computational effort required for the solution of the Eulerian model is higher than that in the VOF and Mixture models because the number of transport equations that need to be solved in Eulerian model is higher than that in VOF and Mixture models [30].…”

Computational and Experimental Investigation of using an Extractor in the Vertical Gravitational Flash Tank Separator

“…The Eulerian model is appropriate for the gas-liquid two-phase flow [18]. Many numerical simulations of gas-liquid two-phase flow have used the Eulerian model in different geometries including sudden expansion [19] and flow in a horizontal tube [20], [21] because it is more accurate than the Volume of Fraction (VOF) and Mixture models [19]. In the Eulerian approach, the liquid phase and vapour phase are both treated as a continuous phase by using the volume fraction for each phase [22].…”

“…In the Eulerian approach, the liquid phase and vapour phase are both treated as a continuous phase by using the volume fraction for each phase [22]. The Eulerian two-phase model solves a set of two-phase differential equations for each phase, so it is the most complex of the two-phase models [19]. Consequently, the computational effort required for the solution of the Eulerian model is higher than that in the VOF and Mixture models because the number of transport equations that need to be solved in Eulerian model is higher than that in the VOF and Mixture models.…”

Simulation of the double emulsion formation through a hierarchical T-junction microchannel

“…A model of unsteady mass transfer which takes into account the mass exchange between the microspheres and continuous phase inside the droplets is proposed by Wroński et al (2012). Roul and Dash investigated the flow through sudden contraction and expansion with oil-water emulsions by using two-phase flow model in an Eulerian scheme (Roul and Dash, 2009). The drop-based microfluidic devices are used to encapsulate single mammalian cells in distinct pico liter sized droplets to isolate them in their own microenvironment by Köster et al (2008).…”