Pipe Inclination Research Articles

Stop-end method for the panel connection of cut-off walls

For cut-off walls constructed by the stop-end method, the selection of the proper time and the definition of the withdrawal force for the removal of stop-end pipes are key concerns for the quality and schedule control of the entire wall. A very deep cut-off wall using stop-end technology was constructed in Tibet to control seepage in an alluvium layer at a depth over 150 m. The case study included the design, construction and quality investigation of this wall and real-time monitoring of the removal of stop-end pipes. The monitoring results revealed that the waiting time prior to the removal of the stop-end pipes is mainly controlled by the characteristics of the concrete, and should occur after the initial setting time of the concrete. Several factors have an influence on the withdrawal force of a stop-end pipe, including the self-weight of the stop-end pipe, the interaction force between the pipe–concrete and the friction between the pipe–side walls. The force is obviously affected by the inclination of the stop-end pipe, especially in the direction parallel to the wall axes.

A methodology to quantify the uncertainty in liquid holdup measurements with wire mesh sensor

The uncertainty in the holdup measurements of a capacitance based WMS with 32×32 wires has been experimentally evaluated, and a methodology for its quantification is proposed for horizontal flow. Investigation is performed in laboratory and in-situ experiments under stagnant conditions with an emphasis on the effect of the mesh grid orientation on the measurements. Also, potential impact of misalignment in the pipe inclination is explored by slightly inclining the pipe for both tests. Finally, dynamic flow conditions are tested in a high pressure (1.37MPa) facility with horizontal stratified-wavy oil/air two-phase flow for gas and liquid superficial velocity ranges of 2.8m/s≤νSg≤6.9m/s and 0.01m/s≤vSL≤0.05m/s, respectively.The angle between the phase interface and the sensor wires is ineffective while the misalignment in the pipe inclination plays a major role in the deviations of the holdup measurements. Using the proposed methodology, the measurement uncertainty from laboratory tests is shown to follow a logarithmic increase as a function of the measured holdup for smaller holdup values (HL≤15%) and to be lower than 1.5% for HL>15%. This behavior is intrinsic to WMS and a representative of the measurement uncertainty in the actual flow loop installation.Under actual flow conditions, the holdup measurements of the trapped liquid by WMS show an offset compared to the measurements via flow imaging which can be corrected by using the uncertainty quantified in the laboratory tests. However, the dynamic measurements with WMS show a good agreement with the holdup of the trapped liquid volume within the quantified uncertainty bounds.

Development of remote pipe welding tool for divertor cassettes in JT-60SA

Remote pipe welding tool accessing from inside of the pipe has been newly developed for JT-60SA. Remote handling (RH) system is necessary for the maintenance and repair of the divertor cassette in JT-60SA. Because the space around the cooling pipe connected with the divertor cassette is very limited, the cooling pipe is to be remotely cut and welded from inside for the maintenance. A laser welding method was employed to perform circumferential welding by rotating the focusing mirror inside the pipe. However, the grooves of connection pipes are not precisely aligned for welding. The most critical issue is therefore to develop a reliable welding tool for pipe connection without a defect such as undercut weld due to a gap caused by angular and axial misalignments of grooves. In addition, an angular misalignment between two pipes due to inclination of pipe has to be taken into account for the positioning of the laser beam during welding. In this paper, the followings are proposed to solve the above issues: (1) Cooling pipe connected with the divertor is machined to have a jut on the edge so as to expand the acceptable welding gap up to 0.5mm by filling the gap with welded jut. (2) Positioning accuracy of the laser beam for reliable welding is realized to be less than ±0.1mm along the circumferential target for welding by a position control mechanism provided in the tool even in the case of up to angular misalignment of 0.5° between connection pipes. Based on the above proposals, we have achieved robust welding for a large gap up to 0.5mm as well as the maximum angular misalignment of 0.5° between connection pipes by using this newly developed tool.

The effect of surfactants on upward air–water pipe flow at various inclinations

In this work, we extend our previous efforts on the effect of surfactants on air-water flow in a vertical pipe by also considering pipe inclinations between 20° (with respect to horizontal) and vertical. For air–water flow, independent of the inclination, there is a regular annular flow at large gas flow rates, and an irregular churn or slug flow at low gas flow rates. Closely related to the transition between regular and irregular flow, although not necessarily coinciding with it, there is a minimum in the pressure gradient as a function of the gas flow rate. In gas wells, surfactants are used to shift this minimum to lower gas flow rates, which allows a stable gas production up to lower reservoir pressures. In this work, we investigate how the pipe inclination affects air–water flow without and with surfactants. Surfactants generate foam, which decreases the density and increases the thickness of the film at the pipe wall. For vertical flow, we previously established that surfactants increase the pressure gradient at high gas flow rates, decrease the pressure gradient at low gas flow rates, shift the minimum in the pressure gradient to lower gas flow rates, and shift the transition between regular and irregular flow to lower gas flow rates. The new results described in this paper show that for large gas flow rates, both the flow with and without surfactants is unaffected by the inclination. At low gas velocities, however, in inclined pipes the surfactants are much less effective at shifting the transition between irregular flow and regular flow and at shifting the minimum in the pressure gradient than in vertical pipes. The foam causes a regular film morphology at the top wall of the pipe, but is unable to make the morphology of the bottom liquid film regular. As a result, at low gas flow rates the relative decrease of the pressure gradient due to surfactants is smaller for smaller inclinations from horizontal. This larger relative decrease for vertical flow compared to inclined flow is related to an increased foam formation and therefore a smaller mass density of the film in vertical flow.

CFD-DEM simulation of the hole cleaning process in a deviated well drilling: The effects of particle shape

We investigate the effect of particle shape on the transportation mechanism in well-drilling using a three-dimensional model that couples computational fluid dynamics (CFD) with the discrete element method (DEM). This numerical method allows us to incorporate the fluid–particle interactions (drag force, contact force, Saffman lift force, Magnus lift force, buoyancy force) using momentum exchange and the non-Newtonian behavior of the fluid. The interactions of particle−particle, particle−wall, and particle−drill pipe are taken into account with the Hertz–Mindlin model. We compare the transport of spheres with non-spherical particles (non-smooth sphere, disc, and cubic) constructed via the multi-sphere method for a range of fluid inlet velocities and drill pipe inclination angles. The simulations are carried out for laboratory-scale drilling configurations. Our results demonstrate good agreement with published experimental data. We evaluate the fluid–particle flow patterns, the particle velocities, and the particle concentration profiles. The results reveal that particle sphericity plays a major role in the fluid–solid interaction. The traditional assumption of an ideal spherical particle may cause inaccurate results.

Characteristics of stratified laminar flows in inclined pipes

Exact solutions for laminar stratified flows in inclined pipes are presented. These include all possible configurations of stratified flows with concave and convex interfaces. The exact solution is used to study the effect of the flow geometry and pipe inclination on the holdup and pressure gradient. In particular, the possibility of reducing the pressure gradient of a viscous fluid in upward inclined flows by adding a lubricating phase is investigated. It is shown that independently of the density of the lubricant, namely, whether it is lighter or heavier than the viscous fluid, the effect of hydrostatic pressure gradient always adversely affects the possibility to reduce the pumping requirement for the flow of the viscous phase. In addition, the countercurrent flow limits and the boundaries of the multiple solution regions in concurrent inclined flow are identified and discussed. The susceptibility of the system to the Ledinegg instability when using separate pumps for each of the fluids is also examined.

Gas/shear-thinning liquid flows through pipes: Modeling and experiments

In chemical and oil industry gas/shear-thinning liquid two-phase flows are frequently encountered. In this work, we investigate experimentally the flow characteristics of air/shear-thinning liquid systems in horizontal and slightly inclined smooth pipes. The experiments are performed in a 9-m-long glass pipe using air and three different carboxymethyl cellulose (CMC) solutions as test fluids. Flow pattern maps are built by visual observation using a high-speed camera. The observed flow patterns are stratified, plug, and slug flow. The effects of the pipe inclination and the rheology of the shear-thinning fluid in terms of flow pattern maps are presented. The predicted existence region of the stratified flow regime is compared with the experimental observation showing a good agreement. A mechanistic model valid for air/power-law slug flow is proposed and model predictions are compared to the experimental data showing a good agreement. Slug flow characteristics are investigated by the analysis of the signals of a capacitance probe: slug velocity, slug frequency, and slug lengths are measured. A new correlation for the slug frequency is proposed and the results are promising.

An Empirical Model to Predict the Transition Between Stratified and Nonstratified Gas–Liquid Two-Phase Flow in Horizontal and Downward Inclined Pipes

The specific objective of this work is to develop an empirical model to predict the existence of stratified flow in horizontal and downward inclined gas-liquid two-phase flow. The proposed model is in nondimensional form and attempts to emulate the qualitative trend of the Taitel and Dukler mechanistic model. The key advantage of the proposed method is that it is explicit in nature and, unlike Taitel and Dukler, it does not require use of a graphical or iterative solution. The empirical parameters used in the proposed model account for the effect of pipe diameter, pipe orientation, and the liquid density on the transition line between stratified and nonstratified flow. The accuracy of the proposed model is verified against the flow visualization data collected from more than 16 data sources consisting of 8 fluid combinations, pipe diameter in a range of 8.9 to 300 mm, liquid density in a range of 780 to 1420 kg/m3, and all downward pipe inclinations including horizontal.

Bubble shape in horizontal and near horizontal intermittent flow

This paper presents an experimental study of the shape of isolated bubbles in horizontal and near horizontal intermittent flows. It is found that the shapes of the nose and body of bubble depend on the Froude number defined by gas/liquid mixture velocity in a pipe, whereas the shape of the back of bubble region depends on both the Froude number and bubble length. The photographic studies show that the transition from plug to slug flow occurs when the back of the bubble changes from staircase pattern to hydraulic jump with the increase of the Froude number and bubble length. The effect of pipe inclination on characteristics of bubble is significant: The bubble is inversely located in a downwardly inclined pipe when the Froude number is low, and the transition from plug flow to slug flow in an upward inclined pipe is more ready to occur compared with that in a downwardly inclined pipe.

Performance analysis of cylindrical heat pipe using nanofluids – An experimental study

The present work analyzes the thermal performance of a cylindrical copper mesh wick heat pipe using water based CuO nanofluids. The studies are extended further by varying the heat pipe inclination angle and heat input. Thermophysical properties of CuO/DI water nanofluids are also effectively analyzed. The reduction in thermal resistance ratio is about 23.83% and 10.43% respectively for 1.0 and 1.5wt.% of CuO nanofluid compared with low concentration. Evaporation and condensation heat transfer coefficient ratios are improved by the use of CuO nanofluid and the maximum enhancement obtained is 30.50% and 23.54% respectively for an optimum tilt angle of 60°. Thermal efficiency of heat pipe tends to increase with the heat load and inclination angle and an improvement of 33.34% is observed for 120W heat load at 60° inclination angle compared with the horizontal heat pipe. After the experimentation, characterizations of mesh wick structures are carried out. It is found that the deposition of CuO nanoparticles creates a thin coating layer on the wick surfaces in evaporator section. This increases the surface wettability and enhances the thermal performance of heat pipe.

ICONE23-1410 SCALING OF THE STEADY STATE BEHAVIOUR OF RECTANGULAR SINGLE-PHASE NATURAL CIRCULATION WITH INCLINING HEAT SOURCE

In the present study, the steady state performance of a natural circulation loop with inclined heat source is investigated. The rectangular single phase natural circulation loop consists of a vertical cooling pipe, an inclined heating pipe and two horizontal pipes made of steel, connected by means of four 90° bends. The loop has an imposed heat flux in the heating section. The parameters investigated were: power transferred to the fluid, mass flow rate and inclinations of heating pipe. The generalized dimensionless groups are established which are useful in comparing the performances of different loops and to extend data from small scale loops to the prototype. The capability of the computer code ATHLET, developed by GRS, for predicting the stable behavior of single phase natural circulation loops is tested by simulating rectangular NCLs facilities. Then, the dimensionless groups of the present apparatus are developed based on Vijayan's model taking into account of the heating pipe inclinations. The steady-state analysis results show a good agreement with the correlation developed by this study, which suggests that simulation of the steady state flow in single phase NCLs can be well achieved by the non-dimensional parameter Re, Gr_m and N_G.

Interfacial waves in stratified viscous oil–water flow

The analysis of the interfacial wave properties is an important point in understanding of many aspects of separated-flow patterns (annular and stratified). One may cite flow pattern stability, pressure drop and heat transfer as characteristics affected by the wave properties. Previous studies have shown that the phenomenon of flow pattern transition in stratified flow can be related to the interfacial wave structure (problem of hydrodynamic instability). The study of the wavy stratified flow pattern requires the characterization of the interface, i.e., average wave shape, wave speed, amplitude and wavelength as a function of flow properties. Studies on waves in stratified liquid–liquid flow are scanty, even more when related to viscous oils. This article offers new experimental data on interfacial waves collected in a glass test line of 12m and 0.026m i.d., oil (density and viscosity of 854kg/m3 and 0.3Pas at 20°C, respectively) and tap water as the working fluids; the stratified flow was filmed with a high speed video camera at several inclinations from horizontal (−5°, 0°, 5°, 10°). New experimental data and available literature data of interfacial waves in oil–water flow were collected, analyzed and correlated to the flow properties by dimensionless numbers of Reynolds, Froude and Weber. A second-order Fourier series is proposed to model the wave shape. The correlations can be used to predict the average wave geometry and wave speed of typical oil–water interfacial waves within a significant range of superficial velocities and pipe inclinations. Considering the simplicity of the proposed correlation, the agreement between data and predicted wave is encouraging.

Unified drift velocity closure relationship for large bubbles rising in stagnant viscous fluids in pipes

This study investigates the effects of oil viscosity, pipe diameter, and pipe inclination angle on drift velocity. Experiments were conducted for medium viscosity oils using a 0.0508-m ID pipe for inclination angles between 0° and 90°. In these experiments, it was observed that as the liquid viscosity increased, the drift velocity decreased. Drift velocity displayed a convex parabolic behavior with respect to the inclination angle. For all liquid viscosities, a maximum velocity value was observed between 30° and 50° inclinations from horizontal. A unified dimensionless closure relationship for drift velocity is proposed. It was developed using data acquired in this study and available data from literature with a pipe diameter range of 0.0373–0.178 m.

Thermal performance and efficiency of a thermosyphon heat pipe working with a biologically ecofriendly nanofluid

Thermal performance of a wickless thermosyphon heat pipe charged with a biologically-produced ecofriendly working fluid is experimentally studied. Biologically dependable process is a cheap and promising way for obtaining the high quality nanoparticles. Thus, in the present work, using the green synthesis, silver nanoparticles are produced from the aqueous silver nitrate and the fresh tea leaf extract. The formation of Ag nanoparticles was observed by the change of color from colorless to dark brown by the addition of silver nitrate into the leaf extract and proved by SEM, TEM and XRD quality tests. Performing the two-step method, nanofluids at different weight concentrations were prepared, stabilized and used as working fluid inside the thermosyphon. The heat pipe was fabricated from the smooth copper tube with inner and outer diameters of 10.7 and 12mm respectively and total length of 280mm. Uniform heat flux was applied into the evaporator section using electrical cartridge heater and the condenser section was constantly cooled using ethylene glycol/water cooling jacket. Influence of different operating parameters such as applied heat flux to the evaporator section, filling ratio of working fluid, heat pipe inclination, nanoparticle concentration and response time on the thermal performance and efficiency of heat pipe was also experimentally studied and briefly discussed. Results showed that using the nanoparticles leads to the reduction in temperature distribution and enhances the thermal performance of heat pipe.

Flow and Heat Transfer Characteristics of Two-Phase Fluid in Inclined Pipes on a Rotation Platform

A rotating platform was used to create dynamic load, and the mixture air–water two-phase flow and boiling steam–water two-phase flow were obtained in an inclined test pipe. By changing the parameters, such as inclination of the test pipe, rotational speed, inlet temperature, flow rate, and so on, the experiments for two-phase flow in the pipe at inclination of 0°, 45°, and 66° were conducted, respectively. The effects of acceleration and inclination on their flow and heat transfer characteristics were investigated. The two-phase flow patterns in inclined pipes under rotation conditions were caught with a video camera. The images show that the impact mixed flow and churn flow were found in this research. The results show that the acceleration and pipe inclination significantly influence the flow characteristic and heat transfer of the two-phase pipe flow. As the directions of the dynamic load and the gravity are opposite to the flow direction, the greater the dynamic load and inclination, the higher the pressure drop and the heat emission, and the lower the flow rate, the void fraction, and the fluid temperature. Therefore, the dynamic load and gravity will improve the flow resistance, enhance heat emission and reduce the heat gained by the fluid.

Two-Phase Upward Flow in a Slightly Deviated Pipe

This study was undertaken to look at the effect of a slight inclination of pipe on upward flow characteristics especially at 10 deg from vertical position. Air-silicone oil flows in a 67 mm diameter pipe have been investigated using a capacitance wire mesh sensor (WMS) and electrical capacitance tomography (ECT). They provide time and cross-sectionally resolved data on void fraction. Superficial gas and liquid velocities of 0.05–1.9 and 0.05–0.5 were studied. Statistical methods and visual observation methods were used to characterize the fluid flows obtained into different flow patterns. From the output results from the tomography instruments, flow patterns were identified using both the reconstructed images as well as the characteristic signatures of Probability density function (PDF) plots of the time series of cross-sectionally averaged void fraction. Bubbly, cap bubble, slug, and churn flows were observed when the pipe was deviated by 10 deg from vertical pipe for the range of superficial gas velocities considered.

저열유속에서 상변화를 수반하는 메탄의 유동거동특성

A liquefied natural gas(LNG) in cryogenic liquid is converted back into gaseous form for distribution to residential and industrial consumers. In this re-gasification process, LNG supplies a plenty of cold thermal energy about 83.7×10 kJ/kg. The LNG cold thermal energy is utilized for the re-liquefaction process of cryogenic fluids such as Nitrogen, Hydrogen and Helium, and ice manufacturing process and air-conditioning system in some advanced countries. Therefore, it is also necessary to establish the recovery systems of the LNG cold thermal energy around Incheon, Pyungtaek and Tongyung LNG import terminals in our country. Methane is used as working fluid in this paper, which is the major component of LNG over 85 % by volume, in order to investigate the flow behavior characteristics of LNG with phase change at low heat flux. This paper presents the effects of pipe diameters, pipe inclinations and saturation pressures on the flow boundaries of methane flowing in a cryogenic heat exchanger tube, together with those of nitrogen, propane, R11 and R134a. The outcomes obtained from this theoretical researches are also compared with previous experimental data. It was also found that the effect of pipe inclination on the methane flow boundaries was significant.

Friction forces of particulate plugs moving in vertical and horizontal pipes

This paper presents a comprehensive theoretical and experimental analysis of the friction forces of particulate plugs. Friction forces of particulate plugs play a key role in the estimation of the pressure gradient over a pneumatic conveying pipeline. Therefore, a theoretical model to calculate those forces for variable orientations of the pipe inclination (0≤α≤90) was developed. In particular, were analyzed the behavior of various parameters such as plug length, plug diameter, internal friction of the material, wall friction, the pressure gradient due to airflow through the plug, and the stress transmission coefficient. The agreement of the new correlations was found to be in the range of ±15% for the stress ratio values. Moreover, by substituting these correlations into the newly developed theoretical model and comparing its values to experimental results, an agreement of ±30% for the plug friction force calculation was achieved. The present study enables a better understanding of the characteristics of the two-phase (gas–solids) plug flow regime.

Исследование рабочих характеристик тепловых труб для светодиодных осветительных приборов

New energy-saving technologies for lighting is a promising trend in lighting technology. To this end, during the recent decade, have been actively developed and implemented lighting units based on LED modules. Reliability of such devices is largely dependent on the ensuring of cooling of the LEDs. Heat pipes are being used with ever increasing frequency for increasing an efficiency of cooling of powerful LEDs within a lightening device. Results of experimental modeling of thermal characteristics of two aluminum heat pipes with grooved capillary structure and ammonia used as a heat transfer agent, designed for application as a heat transfer elements in designs of powerful LED lightening device with forced air cooling are presented in this paper. It is shown that for the heat flux range of 50 to 100 W and for incident flow speed in the range of 0.8 to 2.1 m/s the temperature in the heating zone of the heat pipe falls into the range of 31.0 to 52.5 °C. In this case the temperature difference along the heat pipe is between 0.9…1.7 °C, when a minimal value of the fed heat flux is 50 W, and 1.7…3.1°C, when a maximum value of the heat flux is 100 W. The value of heat transfer resistance of the heat pipes was in the range of 0.012 to 0.044 °C/W. The key factors influencing the thermal characteristics of the heat pipes are: the value of the fed heat flux, the speed of cooling air flux, heat pipe inclination angle with respect to the horizon. By using five such heat pipes within the powerful LED lightning device it is possible to achieve an elimination of the total heat flux from LED modules up to 500 W. At an efficiency factor of LEDs of about 75% this is equivalent to intake power 665 W. Taking into account that luminous efficiency of modern LEDs is about 10 times as high as those of incandescent lamps, proposed lightning device will produce a luminous flux which is equivalent to the luminous flux of a lightening device with incandescent lamps with a power of 6650 W, so that this will allow reducing an input power of the lightening device by 5985 W.

Cuttings Transport with Gas in the Highly-Deviated Horizontal Wells

Gas drilling has been widely used due to its advantages of protecting and finding oil and gas reservoir, reducing lost circulation and pipe sticking, extending the bit life, and improving rate of penetration (ROP). Cuttings transport in highly-deviated and horizontal segment is considered as an important part of the design of hydraulic parameters. In this case, poor cuttings transport will lead to stuck pipe, higher drag and torque, slower ROP, bad cementing quality, and other problems. In this study, a two-layer steady model was developed to depict cuttings transport behavior, and the sensitivity analyses were conducted. The simulations show the ratio of bed area and annular area and pressure drop decrease with the increase of pipe eccentricity or inclination, and increase with the increasing gas density or gas viscosity. But the inclination, gas density and viscosity have a minor effect on cuttings transport.