Pipe Inclination Research Articles

Incomplete fluid–fluid displacement of yield-stress fluids. Part 2: Highly inclined pipes

We present results of an experimental study of buoyant miscible displacement flows of a yield-stress fluid (Carbopol) by a higher density Newtonian fluid along a long inclined pipe. We focus on the industrially interesting case where the yield stress is significantly larger than a typical viscous stress in the displacing fluid, but where buoyancy forces may be significant. We find that the slump and centre-type displacements identified in our earlier work on near-horizontal flows are in fact observed over the full range of pipe inclinations. Interestingly, the occurrence of these regimes is primarily governed by approximately the same ratio of Reynolds number to densimetric Froude number, Re/Fr, as in near-horizontal case. However, we do observe a range of exotic behaviour for slump flows at higher inclinations associated with the progressive break-up of the Carbopol layer. We give a detailed description of these secondary regimes and their formation. We also observe a third regime which we refer to as turbulent-mixed flow. In this case, despite the existence of the yield stress, the flow is very similar to that for a Newtonian displacement when the mixing is very efficient. In the absence of an imposed flow of the displacing fluid, we observe that flows may nonetheless develop under the action of buoyancy despite the yield stress. We discuss the probable mechanisms and potential implications for the plug cementing process.

Experimental investigation on the performance of CPU coolers: Effect of heat pipe inclination angle and the use of nanofluids

An experimental study of heat transfer performance of a CPU cooling heat pipe, examining the effects of inclination angle and nanofluids, has been conducted. It is shown that inclination angle of the unit has a significant effect on the cooling process, since it directly influences the operation of the evaporator. The effect is mainly due to the capillary effect and boiling limits of the heat pipe. The results demonstrate that for a given CPU temperature, there is a threshold angle at which the thermal resistance of the heat pipe increases dramatically. It is observed that as the CPU temperature increases, the threshold angle decreases from 60° to 30°. Introduction of 0.5wt% Al2O3 nanoparticles to the water coolant of heat pipe has led to a decrease in thermal resistance. It is shown that at 10W, the presence of nanofluid has reduced the thermal resistance by 15%, while at 25W, the thermal resistance has dropped by 22%.

Experimental Characterization of Slug Flow on Solid Particle Transport in a 1 Deg Upward Inclined Pipeline

This paper presents an experimental investigation on the influence of hydraulic and two phase (gas-liquid) flows on sand dune transportation resulting from a stationary flatbed, for horizontal and 1 deg upward pipe inclination. For gas-liquid conveying of solid particles, pipe inclination resulted in considerably different transport phenomena relative to those observed for horizontal orientation. Key distinguishing features such as backward bed movement and enhanced particle suspension were observed and were found to be highly gas-liquid ratio dependent. Using image processing, the solid particle suspension layer was quantified as a function of the gas-liquid flow. The measurements presented provide fundamental insights into the influence of upward pipe inclination on bed-load mode solid transportation in a closed conduit.

Miscible density-unstable displacement flows in inclined tube

We study the displacement flow of two Newtonian fluids in an inclined pipe. The fluids have the same viscosity but different densities. The displacing fluid is denser than the displaced fluid and is placed above the displaced fluid (i.e., a density-unstable configuration). Three dimensionless groups describe these flows: a densimetric Froude number Fr, a Reynolds number Re, and the pipe inclination β. Our experiments cover fairly broad ranges of these parameters: 0 ⩽ Fr ⩽ 9; 0 ⩽ Re ⪅ 2400; 0 ⩽ β ⩽ 85°. Phenomenologically, our experimental flow observations vary from well mixed fully diffusive regimes, through buoyancy-dominated inertial exchange regimes, to laminar viscous flows, all with varying degrees of stability. We characterize the different flow regimes observed in terms of the three dimensionless groups and provide leading order approximations to the velocity of the displacement front and the macroscopic diffusion in each regime.

Large probe arrays for measuring mean and time dependent local oil volume fraction and local oil velocity component distributions in inclined oil-in-water flows

Arrays of dual-sensor and four-sensor needle conductance probes have been used to measure the mean and time dependent local properties of upward inclined, bubbly oil-in-water flows (also known as dispersed oil-in-water flows) in a 153mm diameter pipe. The flow properties that were measured were (i) the local in-situ oil volume fraction α; (ii) the local oil velocity uo in the axial direction of the pipe (the Z direction); and (iii) the local oil velocity uY in the direction from the lower side of the inclined pipe to its upper side (the Y direction). Oil velocities in the X direction (orthogonal to the Y and Z directions) were found to be negligible. For all of the flow conditions investigated it was found that the mean value of α varied from a maximum value at the upper side of the inclined pipe to a minimum value at the lower side, and that the rate of decrease of this mean value of α with distance in the −Y direction became greater as the pipe inclination angle θ from the vertical was increased. It was also found that the mean value of uo was greatest at the upper side of the inclined pipe and decreased towards the lower side of the inclined pipe, the rate of decrease with distance in the −Y direction again becoming greater as θ was increased. For θ=45o, a water volumetric flow rate Qw=16.38m3h−1, an oil volumetric flow rate Qo=6.0m3h−1 and using a sampling period T=0.05s over a total time interval of 60s, it was found that at the upper side of the inclined pipe the standard deviation in uo was 31.6% of the mean value of uo. Furthermore for T=0.05s, θ=30o, Qw=16.38m3h−1 and Qo=6.0m3h−1 it was found that the standard deviation in the cross-pipe oil velocity component uY was approximately equal to the standard deviation in the axial velocity component uo. These large temporal variations in the local flow properties have been attributed to the presence of large scale Kelvin–Helmholtz waves which intermittently appear in the flow. It is believed that the techniques outlined in this paper for measuring the standard deviation of local flow properties as a function of the sampling period T will be of considerable value in validating mathematical models of time dependent oil–water flows. It should be noted that the principal focus of this paper is on the measurement techniques that were used and the methods of data analysis rather than the presentation of exhaustive experimental results at numerous different flow conditions.

A new method for evaluating drag reduction in gas–liquid two-phase flow based on energy dissipation

The energy dissipation is generally regarded as only contributed by the frictional pressure drop in gas–liquid two-phase flow. Based on energy dissipation analysis, a new term of energy dissipation is found in inclined gas–liquid two-phase flow. This new term is contributed by the combined effect of gravity, liquid holdup and pipe inclination. The change of liquid holdup is an indication of mechanical energy dissipation for inclined or vertical gas–liquid flows. As a result, a new method is proposed for the evaluation of drag reduction in gas–liquid two-phase flow. An experimental setup with a pipeline was established to examine the different drag reductions in gas–liquid flows by adding small amount of drag reducing agent (DRA). This pipeline has five different test segments with different inclinations. One of them was designed for horizontal single-phase liquid flow. Four of them were designed for horizontal, inclined upward, inclined downward and vertical gas–liquid two-phase flows. The inside diameter of the pipeline is 0.04m. The DRA used here is a water-soluble polymer. The experiments were conducted slightly above atmospheric pressure, using air and the water-based solution of the polymeric DRA. For horizontal gas–liquid flow, the drag reductions evaluated by this new method are identical with the results evaluated by a method usually used in multiphase flow. But for vertical and inclined gas–liquid flows, the deviations between these two methods are obvious. The maximum relative deviation is as high as 3.9 which occurs in inclined downward flow. It is found that the polymeric DRA has the maximum effect in horizontal gas–liquid flow rather than in inclined and vertical cases from the point of view of energy dissipation. The findings here provide new insights into the drag reduction occurring in gas–liquid two-phase flow, especially in inhomogeneous inclined and vertical cases.

Spatial distribution of void fraction in the liquid slug in the whole range of pipe inclinations

A wire mesh sensor was used to detect the local instantaneous cross-sectional distribution of the phases in gas-liquid slug flow. Data were obtained for a wide range of flow rates and for pipe inclinations ranging from shallow to vertical. Processing of the wire mesh sensor data yielded detailed information of the 3D void fraction distribution in the liquid slug. These results shed additional light on the hydrodynamics of slug flow, in particular, regarding the formation and distribution of dispersed bubbles in the liquid slug. Comparison with available data was carried out. The present results compared favorably with model predictions.

An Efficient Drift-Flux Closure Relationship to Estimate Liquid Holdups of Gas-Liquid Two-Phase Flow in Pipes

The reliable predictions of liquid holdup and pressure drop are essential for pipeline design in oil and gas industry. In this study, the drift-flux approach is utilized to calculate liquid holdups. This approach has been widely used in formulation of the basic equations for multiphase flow in pipelines. Most of the drift-flux models have been developed on an empirical basis from the experimental data. Even though, previous studies showed that these models can be applied to different flow pattern and pipe inclination, when the distribution parameter is flow pattern dependent. They are limited to a set of fluid properties, pipe geometries and operational conditions. The objective of this study is to develop a new drift-flux closure relationship for prediction of liquid holdups in pipes that can be easily applied to a wide range of flow conditions. The developed correlation is compared with nine available correlations from literatures, and validated using the TUFFP (Fluid Flow Projects of University of Tulsa) experimental datasets and OLGA (OiL and GAs simulator supplied by SPTgroup) steady-state synthetic data generated by OLGA Multiphase Toolkit. The developed correlation performs better in predicting liquid holdups than the available correlations for a wide range of flow conditions.

Prediction of pressure gradient and holdup in wavy stratified liquid–liquid inclined pipe flow

Pressure gradient and holdup data are presented for oil–water flow in a horizontal and inclined 0.026m i.d. pipe (borosilicate glass, 15.5m length and pipe inclinations of −10°, −20° and +10°). A wavy stratified flow in the laminar-turbulent regime with no dispersion whatsoever at the interface was observed. The relatively high-viscosity oil flow (280mPas) dominates the friction and the low Eötvös number indicates the existence of a wavy and curved interface. A new closure relation for the interfacial friction factor is suggested. Recent interfacial wave amplitude data are used for the proposition of a correlation for the interfacial friction factor based on the equivalent-sand-roughness concept. An explicit equation for the interface shape based on the constant-curvature-arc model is proposed, which is a function of the Eötvös number, holdup and contact angle. A discussion on the typical contact angles observed in liquid–liquid flow in pipes of different materials is carried out. It was found that for the slower lighter phase (oil) the effective wall friction factor is significantly lower than the single-phase friction factor, corresponding to an increase of the respective hydraulic diameter. CFD simulations provided an estimate of the cross-sectional wave shape and delivered holdup and pressure gradient results. The phenomenological model is validated against data from the literature and its predictions are compared with present data, models from the literature and CFD results. The favorable comparisons and simplicity of the proposed closure relations are promising, aiming to practical application.

LNGC 디젤기관 크랭크 챔버용 액체질소 불활성가스 시스템에 관한 연구

It is necessary to install the inert gas system(IGS) for preventing fire and explosion in LNGC main diesel engine crankcase besides oil mist detector(OMD) unit with CO₂ gas injector. Therefore, to design the liquid nitrogen IGS, analytical work is conducted for predicting the heat input load of liquid nitrogen heater with two-phase stratified flow model. This paper also presents the effects of changes in pipe diameter, saturated pressure, and inclination angle by ship’s movement on cryogenic two-phase stratified flows. It is found that the stratified model gives reasonable predictions, and the model is effective to predict the heat input load of liquid nitrogen IGS.

Liquid Entrainment in Annular Gas/Liquid Flow in Inclined Pipes

Summary Entrainment fraction is one of the key parameters in many applications, including wellbore and flowline design, separator design, wellbore loading, and corrosion inhibition. This study provides the first comprehensive entrainment data and their critical analysis for a full range of inclination angles ranging from horizontal to vertical in 76.2-mm-internal-diameter (ID) pipes. Experiments were conducted to investigate the effect of pipe inclination on entrainment fraction in air/water annular flow with inclination angles of 0, 10, 20, 45, 60, 75, and 90° from horizontal. Two techniques were used to measure the entrainment fraction: film removal and isokinetic sampling. The experimental results were compared with existing models and correlations, and the best predicting methods were determined for all flow orientations. An inclination effect on entrainment fraction was observed. This effect occurred at low superficial gas velocities and was more prominent for higher superficial liquid velocities. Using the present study data, the Paleev and Filipovich (1966) correlation was found to be the most accurate in predicting entrainment fraction. On the basis of all available data, the Pan and Hanratty (2002b) correlation performed the best in predicting entrainment fraction in all pipe orientations. For vertical annular flow, the Oliemans et al. (1986) correlation predicted entrainment fraction more accurately. The Pan and Hanratty (2002b) correlation was the most accurate in predicting entrainment fraction for horizontal annular flow. The Wallis (1969) correlation and the mechanistic model developed by Mantilla (2008) most accurately predicted the entrainment fraction for inclined annular flow.

Sand Transportations and Deposition Characteristics in Multiphase Flows in Pipelines

Sand management strategies become an important study to be performed as part of multiphase flow assurance assessments during oil and gas project life and especially for subsea multiphase flow network. This paper presents experimental works to investigate the sand transport characteristics and identify the sand minimum transport condition (MTC) in sand–water and sand–air–water flows in a horizontal and + 5 deg inclined pipelines. The used sand volume fraction, Cv, ranged from 1.61 × 10−5 up to 5.38 × 10−4. The sand minimum transport velocity in single-phase water flow was obtained visually and then compared with that calculated by previous correlations for slurry transport. It was found that in sand–water flow, the pipeline inclination had negligible effect on the minimum sand transport velocity. However, the transport characteristics of sand particles were found changed significantly by changing the pipe inclination, which could result in the change of air–water flow regime. It was observed that sand particles transport more efficiently in terrain slug than stratified wavy flow in +5 deg inclined pipes. The sand transport and settling boundary for different air–water flow regimes were generated for horizontal and +5 deg inclined pipeline.

Estimation of volume fraction and flow regime identification in inclined pipes based on gamma measurements and multivariate calibration

A combination of gamma measurements and multivariate calibration was applied to estimate multiphase flow mixture density and to identify flow regime. The experiments were conducted using recombined hydrocarbon fluids sampled from an onshore receiving terminal including hydrate thermodynamic inhibitors (monoethylene glycol and methanol (MeOH)). These hydrate inhibitors were added to deionised water at 60% concentration by volume. The experiments were conducted at a temperature of 0 °C and a 75‐bar pressure, comparable with deep water production on the Norwegian continental shelf. Two angles of inclination (1° and 5°) and two water cuts (15% and 85%) were investigated. A single‐energy gamma densitometer was installed on the test facility for measuring the mixture density, whereas the dual‐energy gamma densitometer was traversed linearly from the bottom to the top of the pipe for multivariate calibration and prediction. Seventy partial least square prediction models were calibrated based on single‐phase experimental data. These models were used in estimating the mixture density and identifying the flow regime in all the experiments. The estimated mixture densities were accurate as compared with those from the single‐energy gamma densitometer with the root mean square error of prediction of 13.6 and 9.7 kg/m3 for 1° angle of inclination and 17 and 26.6 kg/m3 for 5° pipe inclination. The models were also able to identify the flow regimes investigated for both 1° and 5° angles of inclination. Copyright © 2012 John Wiley & Sons, Ltd.

Influence of surfactant on two-phase flow regime and pressure drop in upward inclined pipes

The influence of a surfactant on the two-phase flow regime and the pressure drop in upward inclined pipes is investigated for various gas/liquid flow rates. The air/water and air/100 ppm sodium dodecyl sulphate aqueous solution are used as the working fluids. The influence of the surfactant on the two-phase flow regime in upward inclined pipes is investigated using the electrical tomographic technique. For 0°, 2.5° and 5° pipe inclinations, the surfactant has obvious effect on the transition from the stratified wavy flow to the annular flow, and the range of the stratified smooth flow regime is also extended to higher gas velocities. For 10° pipe inclination, no stratified flow regime is observed in the air/water flow. In the air/surfactant solution system, however, the stratified flow regime can be found in the range of USH = 10m/s−28m/s and USL = 0.07m/s−0.2m/s. For all inclination angles, the changes of the pressure gradient characteristics are accompanied with the flow pattern transitions. Adding surfactant in a two-phase flow would reduce the pressure gradient significantly in the slug flow and annular flow regimes. In the annular flow regime, the pressure gradient gradually becomes free of the influence of the upward inclined angle, and is only dependent on the property of the two-phase flow.

Drag Reduction of Gas-Liquid Two-Phase Flow in Steel Pipes with Different Inclination Geometry

It is significant to make researches on drag reduction in two-phase transport pipeline because two-phase flow has high energy dissipation. API X 52 steel pipe with diameter of 40mm is used in this paper to simulate pipeline with different inclination geometry including horizontal, up-inclined and vertical sections. The up-inclined section has an inclination angle of eight degree. Experiments and theoretical analysis are carried out to study the drag reduction characteristics of gas-liquid two-phase flow in these three sections. The drag reducing agents used here is polyacrylamide. It is found that two-phase drag reduction varies with pipe inclination geometry. The largest drag reduction efficiency occurs in horizontal pipes and which is up to seventy percent. Drag reduction efficiency in up-inclined section is up to sixty percent. Drag reduction in vertical section is the lowest and which can be up to about thirty percent. A mechanistic drag reduction model is proposed to predict drag reduction in gas-liquid two-phase flow. The results predicted are in good agreement with the experiment data.

Numerical simulation of single elongated bubble propagation in inclined pipes

Volume of Fluid (VOF) method was applied to investigate the hydrodynamics of single elongated bubble propagation in inclined pipes. Specially, a moving reference frame attached to the bubble nose was implemented in ANSYS FLUENT. The CFD model was validated with experimental data on the bubble rising speed in inclined pipes with stagnant liquid. The model performance with various turbulence models was studied. The effects of pipe inclination on bubble shape, propagation speed, velocity profile and wall shear stress distribution were analysed. The effect of flowing liquid on the bubble propagating hydrodynamics was also investigated.

Effect of Inclination Angle in Heat Pipe Performance Using Copper Nanofluid

An experiment was carried out to study the thermal efficiency enhancement of the heat pipe using copper nanofluid as the working fluid. The copper nanoparticles are uniformly suspended with the de-ionized water using ultrasonic homogenizer to prepare the copper nanofluid. The average particle size of the copper is 40nm and the concentration of copper nanoparticle in the nanofluid is 100mg/lit. The study discusses about the effect of heat pipe inclination, type of working fluid and heat input on the thermal efficiency and thermal resistance. The experimental results are evaluated in terms of its performance metrics and are compared with that of DI water.

Normal-Force Control for an In-Pipe Robot According to the Inclination of Pipelines

To move freely, in-pipe robots must be able to adapt to the various geometric changes of pipes. Previously, we described an in-pipe robot that can adapt to changes in diameter and curvature of center curves. This robot is able to estimate the forces exerted on the inner surface of the pipes and balance its posture inside the pipe using angular sensors attached to its rotational joints. In this paper, a method is proposed to estimate the relative attitude between the robot's main body and the pipe using the angular sensors attached to a pantograph mechanism. The use of angular sensors makes the structure of the robot simpler and more effective than the use of force or vision sensors because the normal forces and attitude can be estimated from measured angle information. This geometric estimation of attitude relative to the pipes enables the robot to recognize the inclination of the pipes. The PAROYS-II robot can control its normal force according to the variation in pipe inclination. Thus, the proposed method could reduce power consumption and stress on the robot's parts. The algorithm has been validated by multiple experiments.

Friction factors for hydraulic calculations considering presence of cuttings and pipe rotation in horizontal/highly-inclined wellbores

Pressure loss calculations have a vital role for determining hydraulic horsepower requirements and to predict bottomhole treating pressure. One of the major concerns in developing hydraulic programs is to estimate the frictional pressure losses while cuttings are present in the annulus during pipe rotation. An experimental work has been carried out in a cuttings transport flow loop capable of operating at various inclinations. The pressure drop in the test section was recorded for variable flow rates, cuttings concentrations, pipe inclinations and rotation speeds. Existence of cuttings increase the pressure drop due to decrease in flow area inside the wellbore. As there are cuttings in the system, pipe rotation decreases the frictional pressure loss considerably in particular if the pipe is making an orbital motion in the eccentric annulus. Cuttings bed thickness defined as the ratio of cuttings bed area to the wellbore area is expressed in terms of dimensionless parameters obtained from dimensional analysis. Empirical expressions and charts for friction factor are proposed for low and high viscosity fluids in terms of combined Reynolds number and stationary cuttings bed thickness.

Effect of Fluid Properties on Flow Patterns in Two-Phase Gas−Liquid Flow in Horizontal and Downward Pipes†

This paper investigates the effect of gas density and surface tension on flow pattern transitions in horizontal and near-horizontal pipes. Experiments were conducted at atmospheric conditions in a 12.75-m long pipe with a diameter of 0.024 m and downwardly pipe inclinations of 0°, 0.25°, and 1°. The effect of gas density was examined using CO2 and He gases and the effect of surface tension was examined using aqueous solutions of normal butanol. The various transitions were identified visually and by statistical analysis of film height measurements. Gas density strongly affects the transition to 2-D and K−H waves, whereas the transition from stratified to slug flow remains rather unchanged. Both wave transitions can be described satisfactorily by existing models in the literature with some modifications. A reduction in surface tension causes the transitions to 2-D waves to be shifted to much lower gas rates. For downward flows, as previously reported in the literature, even a small inclination can cause an...