D. R. Kaushal

Solids concentration profiles and pressure drop in pipeline flow of multisized particulate slurries

Abstract Concentration profiles for six particle sizes ranging from 38 to 739 μm were measured using a traversing mechanism and isokinetic sampling probe at nine levels in the vertical plane for multisized particulate zinc tailings slurry flowing through 105 mm diameter horizontal pipe. Experiments were conducted at three flow velocities of 2, 2.75 and 3.5 m/s using five efflux concentrations ranging from 4% to 26% by volume for each velocity. Solids concentration profiles were found to be a function of particle size, velocity of flow and efflux concentration of slurry. Solids concentration varied with the vertical position, except for particle size of 38 μm. Experimental data for pressure drop were also collected at five efflux concentrations ranging from 4% to 26% at flow velocities ranging from 1.2 to 4.0 m/s for each efflux concentration. Karabelas model for solids concentration profiles and Wasp model for pressure drop have been modified by alleviating some of the restrictive assumptions used in the models. The modified models are compared with the experimental data collected in the present study and show good agreements. Comparison of pressure drop data with the predictions by two layer model is also satisfactory.

Concentration at the pipe bottom at deposition velocity for transportation of commercial slurries through pipeline

In commercial slurries, the solids being transported are multisized and their size may span three orders of magnitude. The minimum operating velocity is usually kept as 0.5 m/s more than the deposition velocity. Deposition velocity is the flow velocity at which the deposition of solids occurs. In the present study, Kaushal [D.R. Kaushal, Prediction of particle distribution in the flow of multisized particulate slurries through closed ducts and open channels, PhD Thesis, Department of Applied Mechanics, I.I.T. Delhi, 1995], Mukhtar [A. Mukhtar, Investigations of the flow of multisized heterogeneous slurries in straight pipe and pipe Bends, PhD Thesis, Department of Applied Mechanics, I.I.T. Delhi, 1991] and Seshadri et al. [V. Seshadri, R.C. Malhotra, S. Anand, Hydraulic transportation of mineral ores, a state of the art report, Internal Report, Fluid Mechanics Laboratory, I.I.T. Delhi, 1975; V. Seshadri, R.C. Malhotra, Rheological properties of iron ore slimes slurries at high concentrations, Internal Report, Fluid Mechanics Laboratory, I.I.T. Delhi, 1980] data with multisized particulate iron ore slimes, copper tailings and zinc tailings slurries flowing through 105 and 55 mm diameter pipelines have been considered. Based on extensive analysis of experimental data, the Karabelas [AIChE J. 23 (1977) 426] model for prediction of concentration profile has been modified. On the basis of predicted concentration profiles, it is concluded that solid concentration at the pipe bottom reaches approximately 3.0 times the product of efflux concentration and static settled concentration by volume at deposition velocity.

Prediction of concentration and particle size distribution in the flow of multi-sized particulate slurry through rectangular duct

Abstract The analytical model proposed by Karabelas [AICHe J. 23 (4) (1977) 426] has been modified and upgraded to predict the concentration profile and particle size distribution across the cross-section of rectangular duct for the flow of multi-sized particulate slurry. The predictions have been compared with the experimental data reported by Kaushal [Prediction of particle distribution in the flow of multi-sized particulate slurries through closed ducts and open channels, 1995]. The limitations of the original model have been identified and modifications incorporated to take into account the effect of solid concentration on settling rate and particle diffusivity. The predictions by the modified model are in good agreement with the experimental results.

Prediction of Concentration Distribution in Pipeline Flow of Highly Concentrated Slurry

The Kaushal and Tomitas (2002a) model, which has already been found satisfactory for broadly graded multisized particulate zinc tailings slurry with moderate concentration up to 26%, flow velocity up to 3.5 m/s in 105 mm diameter pipe, mean diameter 140 μm, and geometric standard deviation of particles of 4.0, is tested for concentration distribution data collected by Kaushal et al. (2005) on two sizes of glass beads, of which mean diameter and geometric standard deviation are 440 μm and 1.2, and 125 μm and 1.15, respectively, with concentration up to 50% and flow velocity up to 5 m/s in 54.9 mm diameter pipe. Kaushal and Tomitas (2002a) model gives more asymmetric concentration distributions. A modified model is proposed by alleviating some of the restrictive assumptions used in the existing model. Comparison of experimental data by Kaushal et al. (2005), Gillies and Shook (1994), and Matousek (2009) with the proposed model is satisfactory.

Three-Dimensional CFD Modeling for Optimization of Invert Trap Configuration to Be Used in Sewer Solids Management

Flow field prediction and optimization of invert trap configuration have been carried out by using three-dimensional computational fluid dynamics (CFD) modeling with the help of FLUENT software using renormalization group (RNG) k-ϵ along with the discrete phase model (DPM). A hexagonal/tetrahedral shape and map-type nonuniform grid were chosen to discretize the entire computational domain, and a control volume finite difference method was used to solve the governing equations. In the present study, five different invert trap configurations (rectangular with and without lid on both sides, trapezoidal, trapezoidal with rectangular base, and rectangular with trapezoidal base with lid on both sides) have been simulated for the flow of three different inert sediment types (sand, styrocell, and plastic beads) at six flow rates (0.35, 0.70, 1.05, 1.35, 4.55, and 9.95 Lps) for each trap. The discharges selected in the present study cover the entire range of discharge expected in channels during dry weather flow and monsoon. The simulation results are capable of showing particle trajectories and the effect of flow rate and trap geometry on the flow patterns developed within the trap. Based on 3-D CFD modeling and experimental measurements, it has been concluded that the invert trap having a rectangular shape with trapezoidal base with lids on both sides is the most efficient trap configuration with highest sediment retention ratio.

An Improved Method for Predicting Pressure Drop along Slurry Pipeline

Based on extensive analysis of experimental data, the Kaushal and Tomita (2002) model for composite and solids concentration profiles is modified by considering the effect of particle size and efflux concentration on particle diffusivity. Using a modified model, the ratio of the homogeneously and heterogeneously distributed portion of each particle size is calculated. Pressure drop is predicted by summing the pressure drops due to homogeneously and heterogeneously distributed portions of different particle sizes. Comparison with experimental data for pressure drop shows that the proposed model gives better predictions than the models available in literature. The root-mean-square differences between predicted and measured values of pressure drop in percentage of the mean of measured values are for Wasp the et al. (1977) model: 5.0-21.8%; for the Gillies et al. (1991) model: 6.0-9.2%; for the Kaushal and Tomita (2002) model: 1.7-3.5%; and for the proposed model: 1.6-2.0%.

Modeling of sand-water slurry flow through horizontal pipe using CFD

Abstract The paper presents three-dimensional CFD analysis of two-phase (sand-water) slurry flows through 263 mm diameter pipe in horizontal orientation for mixture velocity range of 3.5-4.7 m/s and efflux concentration range of 9.95-34% with three particle sizes viz. 0.165 mm, 0.29 mm and 0.55 mm with density 2650 kg/m3. RNG k-ε turbulence closure equations with Eulerian multi-phase model is used to simulate various slurry flows. The simulated values of local solid concentration are compared with the experimental data and are found to be in good agreement for all particle sizes. Effects of particle size on various slurry flow parameters such as pressure drop, solid phase velocity distribution, friction factor, granular pressure, turbulent viscosity, turbulent kinetic energy and its dissipation have been analyzed.

Analysis of Effect of Grain Size on Various Parameters of Slurry Flow through Pipeline Using CFD

The paper shows three-dimensional CFD modeling of two-phase (water–sand) slurry flows through 53.2 mm diameter horizontal pipe for mixture velocity range of 1.8–3.1 m/s and overall volumetric concentration range of 15–45% with four grain sizes viz. 0.18, 0.29, 0.55, and 2.4 mm. Eulerian model with RNG k–ϵ turbulence closure is adopted to analyze the monodispersed sand particles of varying granular diameters and density 2650 kg/m3. Effects of grain size on various slurry flow parameters have been studied. The simulated local solid concentration values are found to be in good agreement with experimental results at solid concentrations and velocities for smaller grain sizes viz. 0.18 and 0.29 mm. Deviations between these values are recorded in the lower half of the cross-section just near the wall for bigger grain sizes viz. 0.55 and 2.4 mm only. Pressure drop per meter increases with increase volumetric concentration for all grain sizes. The same at any particular volumetric concentration increases with increase in grain size. This increase is approximately 3 to 6 times for 2.4 mm grain as compared to 0.18 mm grain. Qualitative aspects of this analysis have also been presented in the paper.

A comparative study of friction factor correlations for high concentrate slurry flow in smooth pipes

Abstract A number of correlations for friction factor determinations in smooth pipes have been proposed in the past decades. The accuracy and applicability of these friction factor formulas should be examined. Based on this notion the paper is designed to provide a comparative study of friction factor correlations in smooth pipes for all flow regimes of Bingham fluids. Nine models were chosen. The comparisons of the selected equations with the existing experimental results, which are available in the literature, were expressed through MARE, MRE+, MRE-, RMSE, Ѳ, and S. The statistical comparisons were also carried out using MSC and AIC. The analyses show that the Wilson-Thomas (1985) and Morrison (2013) models are best fit models to the experimental data for the Reynolds number up to 40000. Within this range, both models can be used alternately. But beyond this Re value the discrepancy of the Wilson-Thomas model is higher than the Morrison model. In view of the fact that the Morrison model requires fewer calculations and parameters as well as a single equation is used to compute the friction factor for all flow regimes, it is the authors’ advice to use this model for friction factor estimation for the flow of Bingham fluids in smooth pipes as an alternative to the Moody chart and other implicit formulae.

FLOW CHARACTERISTICS OF SECTOR ORIFICE PLATES

ABSTRACT The results of an experimental investigation concerning the characteristics of flow through sector orifice plates in a circular pipe have been reported. Experiments were conducted in a pipe line having diameter of 40 mm and using sector orifice plates with ratios of orifice area to pipe area a/A = 0.20,0.35,0.50,0.65 and 0.80, and having corresponding central angle values θ = 72°, 126°, 180°, 234° and 288°. The data collected in the present study indicate that for clear water flow through sector orifice plates, location of vena contracta is a function of area ratio a/A or central angle θ. The discharge coefficient Cd depends on a/A (or θ), orifice Reynolds number Rd (= 4VR/μ) and pipe Reynolds number RD (= UD/μ). For Rd greater than 1.0 × 105, the value of Cd depends only on a/A or θ- Analysis of the data collected in the present study has been carried out and the discharge equation Q = 3.857 × 10−3 (a/A)1.18 (Δ H)0 50 or Q = 4.41 × 104 (θ)1.18 (Δ H)0.50 for sector orifice plates has been obtaine...