Slurry Flows In Pipes Research Articles

Four-layer model of hydrate slurry flow in pipes considering rheological properties

With the exploitation of deep-water hydrate, the limitations and worrying safety of traditional mining methods such as depressurization gradually pronounced. Therefore, multiphase transportation of slurry draw attention rapidly. Hence, it is necessary to clarify the gas–liquid–solid flow regularity in slurry pipelines and provide accurate guidance for engineering projects. Wherefore, a steady-state four-layer model was developed from Hernandez (2006). The novelties of this model are that the rheological properties of the hydrate slurries were introduced and the effects of concentration distribution (C(y)) both on the solid diffusivity (ε) and interference settling velocity (wm) were considered during the calculation of C(y) in the heterogeneous layer. After improvement, this model can effectively predict the flow state of gas and slurry in pipelines. A comparison with the previous model showed that the prediction accuracy of the proposed model is within 25% for the apparent viscosity and pressure drop gradient in the pipe, indicating that the rheological properties of the hydrate slurries have a non-negligible effect on the flow state. Moreover, the present model improves the prediction accuracy of the hydrate particle C(y) in the heterogeneous layer by considering the interaction between the ε, wm, and C(y). The prediction results of the proposed model for the C(y) and change rate near the interface between the heterogeneous layer and the moving bed layer were in good agreement with the experimental data. Finally, the change laws of the hydrate particle concentration distribution, bed height, and pressure drop gradient under different working conditions were analyzed. Compared with the previous model, there is no flow transition in the velocity range of 0.05–0.5 m/s, and an economic mean concentration exists among the different mean concentrations (CS), which can provide guidance for engineering projects.

Parameter affecting of slurry flow in perforated pipe on fluidization method to maintenance of channel

Slurry flow in pipes is one of the techniques in developing the method of fluidization, especially in the work of sand by passing for the maintenance of estuary channel, port channel, and others. The slurry flow in the pipe determines the fluidization performance, therefore many researchers have studied the slurry flow system in various approaches. This analysis focuses on the factors that influence the flow of slurry in the perforated pipe based on literature studies. The results of the study indicate that several factors are grouped into main parameters such as pipeline parameters, liquid parameters, solid particle parameters and system parameters. All parameters are concluded through the approach of dimensionless numbers such as Reynold Numbers, Froude numbers, concentration, ratio of settling particle to pipe diameter, ratio of hydraulic gradient to mean flow velocity. These parameters have an effect on head loss, friction, drag reduction which controls the flow of slurry in the pipe media. In addition, the constant pressure distribution is a factor that affects the discharge in the slurry flow in the perforated pipe.

Numerical Investigation of the Pressure Drop Characteristics of Isothermal Ice Slurry Flow under Variable Ice Particle Diameter

Ice slurry is an advanced secondary refrigerant that has been attracting considerable attention for the past decade due to the growing concerns regarding energy shortage and environmental protection. To stimulate the potential applications of ice slurry, the corresponding pressure drop of this refrigerant must be comprehensively investigated. The flow of ice slurry is a complex phenomenon that is affected by various parameters, including flow velocity, ice particle size, and ice mass fraction. To predict the pressure drop of ice slurry flow in pipes, a mixture computational fluid dynamic model was adopted to simulate a two-phase flow without considering ice melting. The numerical calculations were performed on a wide range of six ice particle sizes (0.1, 0.3, 0.5, 0.75, 1, and 1.2 mm) and ice mass fraction ranging within 5%–20% in the laminar range of ice slurry flow. The numerical model was validated using experimental data. Results showed that the ice volumetric loading and flow velocity have a direct effect on pressure drop; it increases with the increase in volumetric concentration and flow velocity. The findings also confirmed that for constant ice mass fraction and flow velocity, the pressure drop is directly and inversely related to the particle and pipe diameters, respectively. Moreover, the rise in pressure drop is more significant for large ice particle diameter in comparison to smaller size ice particles at high values of ice concentration and flow velocity.

Analysis of Entropy Generation Rate During Non-Adiabatic Ice Slurry Flow in Pipes

The paper focuses on the entropy generation rate minimization during the flow of ethanol-based ice slurry through straight pipes with a circular and rectangular cross-section. The authors’ original equations for calculating ice slurry flow resistances and heat transfer coefficients were used to determine the impact of the mass fraction of ice, ice slurry flow velocity and heat flux density on the entropy generation rate values observed during flow through pipes. A dimensionless relationship was proposed to determine the interdependency between flow velocity and mass share of ice for which the entropy values were at the minimum level.

Investigation of hydrate slurry flow behaviors in deep-sea pipes with different inclination angles

The marine area is the main direction of the development of oil and gas resources in the world. The pipeline transportation technology of natural gas hydrate slurry plays an important role in the exploitation of marine oil and gas and the exploitation of marine gas hydrate resources. In order to study the influence of pipe inclination on pipeline transportation, population balance model based on hydrate particle aggregation dynamics was coupled with the Eulerian–Eulerian two-fluid multiphase flow model to simulate the flow behaviors of hydrate slurry flow in pipes with different inclination angles. In the study, three variables of inclination, flow rate and initial particle size were considered. The results show that tilted pipes are beneficial to hydrate slurry transport rather than harmful. Meanwhile, higher flow rates and lower initial particle sizes are beneficial for promoting the flow safety of hydrate slurry transport. However, the flow pressure drop of the hydrate slurry increases with the increase of the flow rate and the decrease of the initial particle size, which is not conducive to the economics of mining. The research results in this paper can provide reference for the research of hydrate slurry flow safety and parameter guidance for hydrate solid fluidized mining.

A CFD-PBM approach for modeling ice slurry flow in horizontal pipes

Understanding the flow characteristics of ice slurry is very important for designing and controlling its transportation system. In this study, a CFD-PBM approach consisting of a population balance model (PBM) and a CFD model was established to investigate ice slurry flow in the horizontal pipes. The pressure drops from the CFD-PBM approach are in good agreement with the experimental data. The numerical flow characteristics obtained from the CFD-PBM approach and the CFD approach were quantitatively compared. The results showed that the simulations from these two approaches present the same distribution features, and they are exactly similar in the main flow region. But the ice particle size, ice slurry velocity near the wall region are different, especially there is an obvious difference existing in the ice volume fraction distribution, indicating that the ice size has an obvious impact on the flow characteristics of ice slurry. The CFD-PBM approach has a unique ability to describe ice slurry flow in pipes according to the actual ice size distribution, thus the simulation by the CFD-PBM approach is more efficient. The CFD-PBM approach was also performed under various boundary conditions of ice slurry flow. The results could also correspond to the actual features. Therefore, the proposed CFD-PBM approach is more appropriate to simulate the flow behavior of ice slurry.

Mathematical and experimental investigation on pressure drop of heterogeneous ice slurry flow in horizontal pipes

Ice slurry as an advanced secondary refrigerant has attracted much attention due to the growing concern about energy shortage and environment protection. To promote the practical applications of ice slurry, an extensive knowledge of the pressure drop of ice slurry flow in pipes is beneficial. The available research mainly focuses on the pressure drop of ice slurry flow without considering the non-uniform distribution of ice particles within. Furthermore, the impact of the carrier fluid and ice particles on the pressure drop of ice slurry is not well documented. This investigation combined numerical, analytical and experimental methods to analyze the distributions of concentration, velocity and pressure drop in heterogeneous ice slurry flow. An analytical pressure drop model was developed based on multiphase flow dynamics to quantify the pressure drop of each phase of ice slurry flow. Experiments for laminar and turbulent ice slurry flow in horizontal pipes were used to evaluate the proposed model. The analysis revealed good agreement between the proposed model and experimental data. Moreover, the proposed analytical model is computationally efficient, which can be applied to estimate the pressure drop of ice slurry flow for most practical applications.

The heterogeneous to homogeneous transition for slurry flow in pipes

Models for modeling slurry flow present difficulties on long lines with large pipe diameters and with broad graded sands or gravels. In order to get more insight into the slurry flow process, the Delft Head Loss & Limit Deposit Velocity Framework has been developed that integrates the 5 main flow regimes of slurry transport: fixed or stationary bed transport, sliding bed transport, heterogeneous transport, homogeneous transport and sliding flow transport. Additional models for; the limit deposit velocity, the holdup function, the bed height, the concentration distribution and graded sands and gravels, complement the Framework. The Framework is based on constant spatial volumetric concentration curves for uniform sands and gravels. The models for the flow regimes and the limit deposit velocity are based on energy considerations.At line speeds near the transition of the heterogeneous and homogeneous flow regimes however, there is no sharp transition between the two flow regimes for medium sized particles. The limits of medium sized particles depend on the solid and liquid properties and on the pipe diameter. It is often observed that the hydraulic gradient lies in between the Equivalent Liquid Model (ELM) and the pure liquid Darcy Weisbach model at higher line speeds, resulting in the conclusion that at higher line speeds the pure liquid hydraulic gradient is approached. Based on energy considerations however, it is shown that the heterogeneous hydraulic gradient collapses due to turbulent near wall lift neutralizing the particle submerged weight and collisions with the pipe wall, while at higher line speeds the turbulent eddies integrate particles, resulting in a hydraulic gradient approaching a reduced ELM (RELM). For medium sized particles in large diameter pipes there is a gap between the moment the heterogeneous hydraulic gradient collapses and the homogeneous hydraulic gradient builds up, resulting in a hydraulic gradient approaching the RELM hydraulic gradient. The model for this transition is described and derived and experimental evidence is given.

Numerical Prediction of Particle Distribution of Solid-Liquid Slurries in Straight Pipes and Bends

Turbulent solid-liquid slurry flows in pipes are encountered in many engineering fields, such as mining. In particular, the distribution of the solids is a serious concern to engineers, but its determination involves considerable technical and economic difficulties. A two-fluid model for the numerical prediction of this parameter is presented. The model is robust and numerically stable, and requires relatively short computer time to provide a converged steady-state solution. The novelty of the proposed model and its better performance compared to similar ones reside in the method of accounting for some key physical mechanisms governing these flows, namely turbulent dispersion, interphase friction, and viscous and mechanical contributions to friction. The model is first validated by comparison with many experimental data available in literature regarding the horizontal pipe case over a wide range of operating conditions: delivered solid volume fraction between 9 and 40%; slurry velocity between 1 m/s and 5.5 m/s; and pipe diameter between 50 and 160 mm. A further comparison was performed with respect to recent experiments concerning a horizontal 90° bend.

Development and Application of Slurry Transport Database

The transport conditions of solids in slurry pipelines cause the flow behavior of solid-liquid mixture to vary strongly and affect the hydraulic gradients in the systems. Since any transport design or correlation for slurry transport should be confirmed by a wide range of data, experiments in various flow regimes have been carried out over the years by different researchers. This study was, therefore, aimed at developing a slurry transport database for accumulation, input, editing, sorting, storing of the data available in literature and displaying the results in graphical form for comparison. A basic processing procedure was adopted for the design of the program. Then a flowchart of the program was developed to process the data. The flowchart consisted of three subflowcharts: input-for the input and addition of data; editing-for modifying and standardizing all the data into the Excel CSV form; and graph displays of the data-for comparison of the researchers' data on log-log graphs. Star graphs were used to give a clear description of the transport conditions for each researcher. The database was applied for the verification of proposed correlations for predicting the hydraulic gradients of slurry flow in pipes.

ERT algorithms for quantitative concentration measurement of multiphase flows

Abstract A quantitative image reconstruction algorithm for electrical resistance tomography (ERT) has been developed to visualize multiphase flows, like slurry flows in pipes. Based on image reconstruction techniques from literature, a generalized iterative algorithm (GIA) has been derived to solve the ERT inverse problem. Performance of this algorithm has been studied for synthetic and experimental test cases representing rods and solid particle beds in a pipe. Quantitative images have been obtained for each test case and a suitable strategy for the image reconstruction has been identified. In particular, it was found that convergence of the GIA can be ensured using Landweber or Tikhonov iterations, an efficient forward problem solver and an appropriate relaxation factor. Finally, experimental calibration curve of concentration of solid particle beds in a horizontal pipe has been done using the GIA. Results show the capability of ERT to produce quantitative concentration measurements of multiphase flows.

Experimental Study on Flow Characteristics of Ice-Water Slurries in a Horizontal Pipe.

The pressure loss and the particle velocity profiles for ice-water slurry flows in a pipe were experimentally investigated. The pressure loss was larger than that for clear water flows at lower velocities. On the other hand, it was a little smaller than that for clear water flows at higher velocities. The particle velocity profile at lower velocities was distorted by the friction between the ice particle layer and the pipe wall. However, it approximately agreed with that of turbulent clear water flows at higher velocities.A simplified model was proposed to examine the pressure loss for ice-water slurry flows in pipes at higher velocities. This model gave satisfactory results with experiments.

Slurry Flow in Pipes and Pumps

One of the most effective ways to transport solid material is in the form of slurries. Although the technology of solids pipelining is quite advanced the underlying principles have not yet been formulated past the semiempirical stage. In this paper new approach to slurry flow both in laminar and turbulent regimes is outlined with emphasis on the approach for turbulent slurry flow without deposits which does not rely on subdivisions of slurries into arbitrary groups and which is based on identifiable mechanisms of energy loss. Some aspects of slurry systems and pumps are discussed.