Annular Flow

Experimental data are reported for fully developed laminar flow of a shear-thinning liquid through both a concentric and an 80% eccentric annulus with and without centrebody rotation. The working fluid was an aqueous solution of 0.1% xanthan gum and 0.1% carboxymethylcellulose for which the flow curve is well represented by the Cross model. Comparisons are reported between numerical calculations and the flow data, as well as with other laminar annular-flow data for a variety of shear-thinning liquids previously reported in the litera- ture. In general, the calculations are in good quantitative agreement with the experimental data, even in situations where viscoelastic effects, neglected in the calculations, would be expected to play a role.

Mixtures of xanthan and guar gum in aqueous solution were studied in two flow situations: simple shear and porous media. In addition, solids transport in vertical annular flow of sand suspensions was explored. The zero shear rate viscosity of the solutions displayed a pronounced synergy: the viscosity of the mixture is higher than that of the polymer solutions in a wide range of relative concentrations of the two polymers, in agreement with previous literature. However, at relatively high shear rates, the viscosity approaches the value of the more viscous xanthan gum solutions at mass fractions of xanthan gum between 0.1 and 0.15, and the degree of synergy substantially decreases. Stress relaxation experiments in simple shear indicate that the polymer mixtures exhibit a well-defined yield stress after relaxation that is absent in solutions of pure polymers. In porous media flow experiments, a synergistic behavior mimicking the shear flow results was obtained for the polymer mixtures at low shear rates. However, at a critical shear rate, the apparent viscosity in porous media flows exceeds the shear viscosity due to the elongational nature of flow in the pores. The solids transport capacity in annular flows is well-represented by trends in shear viscosity and stress relaxation behavior. However, the lack of viscosity synergy at high shear rates limits the applicability of the mixtures as a way to improve solids suspension capacity in annular flows.

There is a strong tendency for two immiscible fluids to arrange themselves so that the low viscosity constituent is
in the region of high share. Therefore, it may be possible to introduce a beneficial effect in any flow of a very viscous liquid by
introducing amount of a fluid lubricated as liquid-liquid oil-water flow. Two main classes of flows are seen, annular and small
bubble in all experimental results. The pressure drop and mean heat-transfer coefficients were observed to depend strongly on
the flow patterns. A correlation of the two-phase mean heat-transfer coefficients, based on a simple model of liquid flow, with a
Reynolds number based on the actual mean velocity of the liquid mixture two-phase flow, were developed. An experimental
rig facility has been designed and constructed, to enable measurements of local parameters in oil-water flow in the developing
region of the flow in a 32 mm ID 6 m long pipe. The large discrepancies between model predictions and experimental data are
reported in the literature review that the physics of oil-water flow is complex and not yet fully understood. The flow patterns
that appear are classified in flow pattern maps as functions of either mixture velocity and water cut or superficial velocities.
From these experiments a smaller number of annular flows are selected for studies of velocity and turbulence. The theoretical
study was executed using software Fluent program, a modified turbulent diffusion model is presented. Simulation results
carried out with the model show more physical predictions with respect to the particle deposition process and concentration
profile. The theoretical results represent the pressure gradient distribution, velocity and mean heat transfer coefficient, pressure
contours, velocity vectors, streamlines, and also velocity profiles. It was found that the methods with more restrictions (in
terms of the applicable range of void fraction, liquid superficial Reynolds number) give better predictions.

The purpose of this study was to simplify and improve the mechanistic model developed by Taitel and Dukler (1976) for estimating the liquid holdup in horizontal two-phase flow. An experimental study was first conducted to develop a data bank used for evaluation and ...

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Three-dimensional CFD modeling of two-phase slurry flows is demonstrated in this paper. The flow domain consists of a vertically oriented annular pipe with outer and inner diameter of 0.125 m and 0.025 m, respectively. A mixture velocity range of 0.0738– 0.197 m/s and overall volumetric concentration range of 0.8%–1.8% with 0.23 mm grain size (dp) are used for the simulation. Eulerian model with Reynolds Stres Model (RSM) for turbulence closure is adopted to analyze the monodispersed sand particles of varying granular diameters. The objective of this work is to study the slurry flow using CFD simulation and validating the simulation with experimental studies available in the literature. The simulated pressure losses are found to be in good agreement with experimental results at different conditions. Pressure drop per meter or pressure gradient increases with flow velocity of mixture but after a peak point pressure gradient decreases with the increasing velocity. This phenomena in ve...