CFD Modeling of Pulsed Disc and Doughnut Column: Prediction of Axial Dispersion in Pulsatile Liquid–Liquid Two-Phase Flow

Abstract

Numerical simulations of liquid−liquid counter-current two-phase flow in pulsed disc and doughnut columns (PDDCs) are performed. The simulation methodology comprises two steps. In the first step, the Euler−Euler method is used to obtain turbulent two-phase flow field. Turbulence is simulated by using standard k-ε mixture model. The dispersed phase is assumed to be monodispersed. The second step comprises solution of species transport equation together with flow equations to obtain residence time distribution (RTD) of the continuous phase. The RTD is used to estimate the axial dispersion coefficient or Peclet number of the continuous phase. Experimental data of RTD for different operating conditions (pulsing velocity, dispersed phase velocity, continuous phase velocity) and different geometries (diameter of the column, spacing between the discs) are used for validation. Estimates of the Peclet number by the CFD model are better than the same obtained from previously reported empirical correlations.

Study on Dispersed-Phase Axial Dispersion in an Agitated–Pulsed Solvent Extraction Column with a Step Tracer Injection Technique

“…Different RTD interpretation methods including the moment method ,, and the optimal fitting method ,, have been used in various types of columns to calculate the axial dispersion coefficient from the one-dimensional axial diffusion model by assuming that the axial dispersion coefficient is a constant value along the height of the column. As shown in Figure , by taking the flow direction of phase i as positive, the ADM for both the dispersed and continuous phases can be expressed as where V i is the superficial velocity of phase i and E i is its axial dispersion coefficient.…”

Augmented CFD–PBM Simulation of Liquid–Liquid Two-Phase Flows in Liquid Extraction Columns with Wettable Internal Plates

“…The drag force is the dominant one in liquid−liquid two-phase flows. 33 In the present work, it is calculated via the drag model proposed by Ishii and Zuber. 34 A detailed description of this drag model was provided in our previous work.…”

“…The k –ε turbulent model is used to calculate the turbulent viscosity as adopted by numerous researchers. ,, F ij ⃗ is the interphase interaction force from phase i to phase j, which includes the drag force, lift force, and virtual mass force, and so forth. The drag force is the dominant one in liquid–liquid two-phase flows . In the present work, it is calculated via the drag model proposed by Ishii and Zuber .…”

Nanofluid-Enhancing Shell and Tube Heat Exchanger Effectiveness with Modified Baffle Architecture

“…The shell and tube heat exchanger mainly comprise of shell, tubes, front head, rear head, baffles, and nozzle. For high performance shell and tube heat exchanger, which shows high effectiveness (ε), several parameters affecting the heat and mass transfer process should be optimized, including the working fluid and material selection, flow rate, temperature, heat transfer rate, pressure drop, shell and tube dimension and composition, as well as baffle distance and cut, and pitch range [8][9][10][11][12][13][14]. Considering the architecture of heat exchanger, baffles arrangement is one of the important parameters that will increase the heat transfer and hence the effectiveness.…”

“…Other practical problem arising in industry is that the heat exchanger frequently faces unfavorable thermal properties of its working fluid, i.e. water, ethylene glycol, or oil, leading to the lower heat transfer effectiveness [14]. Therefore, it is necessary to improve the thermal properties of working fluids, one of which is by adding functional nanoparticles into the working fluid [15][16][17].…”