Vertical Pipe System Research Articles

Experimental study of developing free-falling annular flow in a large-scale vertical pipe

Annular flow is the primary characteristic of unsteady wastewater flow, which initiates entrained air and sets up the air pressure regime within the system - an important design consideration. This paper reports on an experimental investigation of free-falling annular flow in a vertical pipe with different inlets at extended flow ranges up to Re = 3 × 104, similar to those in Building Drainage Systems (BDS). In the experimental setup, a vertical pipe system (5 m) was used to record velocity profiles and film thickness in the developing region through Particle Image Velocimetry (PIV) measurements. Entrained droplets were collected through a separator, and the entrainment fraction was calculated at different flow conditions. The study reports on the development process of the film velocity and thickness along the vertical pipe, which agrees well with empirical predictions. The results of the droplet entrainment of a vertical annular flow show the development process to the steady state. Additionally, a Tee-junction inlet in drainage system generates a higher and different entrainment profile.

Seismic performance evaluation of a vertical pipe connected with rigid groove joints using a system and a component

Pipes are fixed to the main structures of buildings and facilities, but they are representative non-structural elements that perform a given unique function without supporting external loads. The fittings and joints of pipes are vulnerable to earthquakes, and if their relative displacement exceeds the allowable displacement owing to the deformation of the structure and collapse of the ground, damage occurs. In this study, the behavior of the fittings and joints in a vertical pipe system connected with rigid groove joints was examined when there is relative displacement of the structure, in an attempt to develop a method of evaluating their seismic performance. It was also examined whether if the behavior of a component unit that includes the fittings and joints of the piping caused by relative displacement can represent the behavior of the elements of the vertical pipe system that is vulnerable to earthquakes or not. The seismic safety of a vertical pipe system connected with rigid groove joints was also evaluated, and the seismic safety and limit states of the fittings and joints of the piping were evaluated through the component test.

Hydrate management in deadlegs: Effect of driving force on hydrate deposition

In oil and gas pipeline networks, deadlegs are sections of process pipes equipped for providing maintenance services. As they are gas-filled with stagnant water saturated gas, gas hydrates are often deposited on the pipe wall and grow into a hydrate plug, which causes severe safety risks and flow assurance problems. One strategy for hydrate mitigation is to apply external heating to the pipe wall to lower the driving force for hydrate formation. Here, we studied how hydrate deposition under water saturated gas is affected by the driving force (temperature gradient) with a 1-in. vertical pipe system. Pipe wall temperatures are varied from −10 to 15 °C, corresponding to 29 to 4 °C subcooling temperatures using a gas mixture of methane/ethane (74.2/25.8 mol%) at 100 bar. Pipe wall temperature is found to affect the temperature gradient in the pipe, and this greatly alters the hydrate kinetics. At high driving forces, most of the water droplets condensed on the pipe wall readily convert into dry hydrate deposits, which are confirmed by dielectric constant responses from a permittivity probe and visual inspection of surface morphologies. As the driving force becomes lowered, some free water remains on the wall, resulting in wet hydrate deposits due to reduced hydrate kinetics. When increasing the pipe wall temperature from −10 to 10 °C, the plug time increases from 35 to 500 h. These results demonstrate that control of the driving force is a promising strategy for hydrate management in deadlegs.

Hydrate management in deadlegs: Limiting hydrate deposition with physical restriction

In the oil/gas production and transportation systems, deadlegs are pipe sections filled with stagnant water saturated gas. Deadlegs are often uninsulated, resulting in cold pipe walls that can readily lead to the formation of gas hydrates. Hydrate deposits consequently can build up in the deadleg, and sometimes result in hydrate plug, which cause severe operational issues. In some instances, deadlegs are used for maintenance purposes, but they pose significant hydrate challenges at the same time. Establishing strategies for hydrate management in deadlegs is therefore important for economic and safety reasons. Here we applied a physical restriction to an 1-in. vertical pipe system at several different locations to verify that the restriction can limit hydrate deposition in water saturated gas. The motiviation of this study is that the presence of a physical restriction, which can also be called an orifice plate, can change water condensation and the following hydrate deposition phenomena. At a given header/pipe wall temperature condition, when the restriction is installed lower than the position where most hydrates are supposed to form, hydrate deposition is limited by changing the temperature profile in th pipe, and thus the water condensation and hydrate deposition. If the restriction is far enough from the header, it has negligible effect on hydrate deposition as the water vapor is sufficiently cooled down. The experimental results provide a demonstration that hydrate deposition in certain types of deadleg may be limited by applying a physical restriction (e.g. a valve) to the pipe or shortening the vertical pipe length.

Axial development of air–water annular flow with swirl in a vertical pipe

Annular flow with swirl induced by a swirler has been widely used in industry. Swirl decay which closely related to working performance and length of the flow is significantly important for its application in industry. Axial development of annular flow with and without swirl has been investigated in this work by means of experimentation and modelling. A vertical pipe system with 11 m long and 62 mm inner diameter was carried out to investigate axial development of flow pattern, void fraction and pressure drop in the annular flow with and without swirl. The experimental results show that a swirling annular flow with swirling streak and less disturbed waves is observed downstream of the swirler. Void fraction decreases, total pressure drop increases and the PDF (probability density function) of pressure drop becomes more concentrated in the annular flow with swirl, compared with these in the annular flow without swirl. However, swirling annular flow is gradually transformed to annular flow without swirl along the streamwise direction. To qualitatively predict the decay in an annular flow with swirl, a simplified theoretical model was developed here. The results calculated with the theoretical model were in agreements with experimental results. The obtained results can be used in predicting working performance and length of devices, such as separators and heat exchangers.

Hydrate Management in Deadlegs: Detection of Hydrate Deposition Using Permittivity Probe

Formation of gas hydrates in oil/gas pipelines has to be properly managed as they can often lead to plugging, primarily by deposition, causing safety issues and significant expenses for repair and recovery. Early detection of hydrate deposition is thus critical for managing such risks and establishing stratagies for hydrate mitigation and remediation. Here, a permittivity probe is applied to an 1-inch vertical pipe system in order to detect hydrate deposition. The vertical pipe system simulates a deadleg, which is a pipe section used for intermittent services and maintenance in hydrate management. Hydrate deposition under water saturated gas environment is monitored by measuring the dielectric constant of the hydrate layer, which is considered as a three-component mixture of hydrates, gas, and water. The permittivity responses upon hydrate formation and dissociation are observed, and their physical interpretations are also provided. By applying appropriate models, thickness, wetness, and porosity of hydra...

Similarities and differences in churn and annular flow regimes in steady-state and oscillatory flows in a long vertical tube

This study investigates the effects of induced-low-frequency flow oscillations on gas–liquid two-phase flows using a 42-m long, 0.048-m ID vertical pipe system. This work uses the experimental data set from a previous study on the effect of forced flow oscillations on churn and annular flow. However, in this previous study, the similarities and differences between flows in steady-state and under induced-low-frequency oscillations were not discussed. The time variation of liquid holdup, frequency of large liquid structures, and pressure gradient were analyzed under two superficial liquid velocities (0.017 and 0.3 m/s), and superficial gas velocities ranging from 4 to 21 m/s. The impact of flow oscillations in two-phase flow regime transitions is also investigated. The observations of flow regimes under oscillatory flow showed significant differences compared to the ones expected in steady-state flow under similar conditions. For higher pressures and oscillatory flow, churn flow regime was observed, when annular flow regime is expected in steady-state flow. Annular flow regime was not observed for higher superficial liquid velocities and high inlet pressure for oscillatory conditions. Surprisingly, the pressure gradient for oscillatory flow is significantly lower than in steady-state flow. However, this lower pressure gradient effect is only observed for low superficial gas and liquid velocities at the pipe inlet and outlet. This experimental observation is attributed to the formation of large liquid waves at the pipe inlet, which is a consequence of the induced-low-frequency flow oscillations.

Hydrate Management in Deadlegs: Hydrate Deposition Characterization in a 1-in. Vertical Pipe System

Deadlegs are the pipe sections used for specific services in production and transportation of oil and gas, and they often encounter hydrate management challenges. Despite stagnant fluids in deadlegs, warm water vapor readily condenses on the cold pipe wall, resulting in a risk of hydrate blockages by deposition. Proper management of hydrates in deadlegs is therefore required for economic and safety reasons. Here, we discuss the development of an 1-in. vertical pipe system that is designed to study hydrate deposition from water saturated gas. From a series of hydrate formation and dissociation, the hydrate deposits are characterized to obtain gas/water consumption, thickness/volume hydrate deposit distribution, hydrate morphology, and hydrate porosity and wetness. These characteristic properties are correlated with the header temperature and the time duration for hydrate deposition. Qualitative and quantitative information obtained from the present study contribute to our understandings of hydrate depositi...

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第3報-自然熱回収および強制熱回収の実験

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第3報-自然熱回収および強制熱回収の実験

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第4報-家屋温度・土壌温度・蓄熱効率および熱回収率の数値計算

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第4報-家屋温度・土壌温度・蓄熱効率および熱回収率の数値計算

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第1報-研究の目的・方法および札幌の地温特性,管温度

太陽熱による垂直管方式の長期地中蓄熱の特性と暖房への応用に関する研究 : 第1報-研究の目的・方法および札幌の地温特性,管温度

Upward gas–liquid two-phase flow after a U-bend in a large-diameter serpentine pipe

We present an experimental study on the flow behaviour of gas and liquid in the upward section of a vertical pipe system with an internal diameter of 101.6mm and a serpentine geometry. The experimental matrix consists of superficial gas and liquid velocities in ranges of 0.15–30m/s and from 0.07 to 1.5m/s, respectively, which cover bubbly to annular flow. The effects on the flow behaviours downstream of the 180° return bend are significantly reduced when the flow reaches an axial distance of 47 pipe diameters from the U-bend. Therefore, reasonably developed flow is attained at this development length downstream of the bend. Other published measurements for large-diameter film thickness show similar trends with respect to the superficial gas velocity. However, the trends differ from those of small-diameter pipes, with which the film thickness decreases much faster with increasing gas flow. As a result, only a few of the published correlations for small pipe data agreed with the experimental data for large pipe film thickness. We therefore modified one of the best-performing correlations, which produced a better fit. Qualitative and statistical analyses show that the new correlation provides improved predictions for two-phase flow film thickness in large-diameter pipes.

Effect of forced flow oscillations on churn and annular flow in a long vertical tube

An experimental study has been carried out to investigate the effects of periodic forced flow oscillations on gas-liquid two-phase flows using a 42m long, 0.05m ID vertical pipe system. From the knowledge of the authors, there is no experimental work available in the literature on the forced flow oscillations for churn flow regime. Therefore, the main objective of this paper is to experimentally characterize churn and annular flows in a long vertical tube. The time variation of liquid holdup, pressure drop and pressure gradient were analyzed under two superficial liquid velocities (0.017 and 0.3m/s), and superficial gas velocities oscillations ranging from 4m/s to 21m/s. The impact of flow oscillations in two-phase flow regime transitions is also investigated.The observations of flow regimes under oscillatory conditions showed significant differences compared to the ones expected in steady-state flow under the same conditions. Under oscillatory conditions, the local liquid holdup and the amplitude of its waves decreased with the distance from the inlet. For the experimental runs with oscillatory gas flow and low superficial liquid velocities (Uls=0.017m/s), the liquid holdup at the bottom of the tube decreased while the gas flow rate was lowered, whereas in steady-state conditions the liquid holdup should increase while reducing superficial gas velocities. This process is described in this study by the formation of large waves in the bottom of the pipe as a consequence of the flow oscillations.

Numerical investigation of the gel barrier formation with vertical injection pipe

Permeation grouting is the injection of a fluid grout into ground and production of a solidified mass to carry increased load and/or fill voids to control water flow. This study examined a technology of constructing horizontal gel barrier by the permeation grouting through multiple vertical injection pipes. Colloidal Silica (CS) solution was used as a gelling liquid to be injected and solidified in the unsaturated soil. Formation of a gel bulb was simulated and the results were compared with those obtained from the sleeve pipe injection with horizontal pipes. The gel bulb generated from the injection method employing vertical pipe showed greater sensitivity of the bulb’s lateral extent to variations in operating conditions compared to the sleeve pipe injection. Although in the limited numbers, in all examined cases, the vertical-pipe system appeared to consume a larger volume of CS solution than the horizontal-pipe system to form an equivalent horizontal gel barrier. This result supports our intuition that the injection with the horizontal pipes may be more effective than the one with vertical pipes in constructing horizontal gel barrier.

The Use of Drag Reduction Agent and a Detergent for Drag Reduction in Circulatory Vertical Pipe Flow

ABSTRACT This paper describes the results of an experimental study of drag reduction in a circulatory vertical pipe system for both upward and downward flows using a drag reduction agent, corrosion inhibitor, and a cheap detergent (washing-up liquid) with various concentrations for different flow rates. It was found that the corrosion inhibitor did not produce any drag reduction effect for both upward and downward flows while the drag reduction agent was effective for both flows; whereas, the detergent was effective only for upward flow. A comparison of the effectiveness of the drag reduction agent against the detergent showed that the effectiveness of the drag reduction agent is much higher than that of the detergent. The effect of liquid detergent is only noticeable if a large concentration is used. A 1000-ppm of detergent produces the same results as 25 ppm of drag reduction agent, which undermined the lower cost of the detergent. Over the range of Reynolds numbers tested the maximum drag reduction for upward flow is 35% while for the downward flow is 42%.

Study of Seasonal Ground Heat Storage of Solar Energy Using a Vertical Pipe System : Part 2-Experiment and Simuration of a Single Vertical Pipe

Study of Seasonal Ground Heat Storage of Solar Energy Using a Vertical Pipe System : Part 2-Experiment and Simuration of a Single Vertical Pipe