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In the present study two-phase flow within the effervescent atomizer has been simulated by the volume of fluid interface tracing model using 0.08%, 0.32%, 1.24%, and 4.9% gas-to-liquid mass ratios and 0.38 L/min liquid flow rate. The purpose of this simulation is to study two-phase flow regimes within the effervescent atomizer and their effect on the atomization quality. This study also considers the gas-liquid interface instabilities in different two-phase flow regimes inside the atomizer. The compressibility of gas phase which is rear in literature survey included in gas-to-liquid mass ratios of 1.24% and 4.9%, due to the high gas phase velocity in constant liquid flow rate and high gas-to-liquid mass ratios. The effect of gravitational force is considered in all simulations. The results of the simulation indicate that by increasing the gas-to-liquid mass ratio, the two-phase flow regime inside the discharge passage transfers from bubbly flow regime with long bubbles to annular flow regime. In addition to decreasing the liquid film thickness coming out from discharge orifice (during transform of the flow regime from bubbly flow to annular flow), the liquid interface instabilities increase in the annular flow regime and besides, where segregated ligaments from the liquid interface become shorter, thinner and more unstable. This type of regime is the most efficient flow behavior for the effervescent atomizer.

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The purpose of this research was to investigate the hydraulic parameters affecting the performance of the distillation column and the hydrodynamic characteristics of the flow field on the industrial scale-sieve tray using numerical simulation. Computational fluid dynamics method was used for analyzing and predicting flow behavior. The desired geometry including the space between two trays of the distillation column and the down comer region was considered. After plotting geometry, three dimensional grids were generated in Gambit software and the analysis of the flow field was traced in Fluent software. The Eulerian-Eulerian approach was applied to simulate two-phase flow and k-ε RNG model for turbulence modeling. Validation of the results was done successfully using Solari and Bell experiment data and the correlation presented by Colwell. The velocity distribution and volume fraction of liquid and gas in different zones were determined. The influence of inlet volumetric flow rate of liquid and gas, as well as the geometry of the weir, on parameters related to the tray performance such as clear liquid height and froth height were investigated. The results indicated that a better separation would occur in lower gas and liquid loads.