Concentric Pipe Research Articles

Buckle propagation of damaged SHCC sandwich pipes: Experimental tests and numerical simulation

Sandwich pipe (SP) combining high-strength performance and thermal insulation has been considered an effective solution for oil and gas transportation in ultra-deepwater. Strain hardening cementitious composite (SHCC) is well known for its capacity to withstand both tensile load and external hydrostatic pressure. The sandwich pipe considered in the research is constituted of concentric steel pipes with SHCC annular layer. In the present research work, the SHCC was manufactured, and full scale sandwich pipes were assembled. Intact and damaged specimens were submitted to controlled external pressure in a hyperbaric chamber to obtain the collapse and propagation pressures, respectively. Modeling and simulation of the buckle propagation of the SPs were correlated with the experimental results. The results show that sandwich pipe with SHCC core has an excellent structural strength under high external pressure in both intact and damaged conditions. Moreover, the results also show that the interaction between the annular and the inner/outer pipes provides a significant contribution to the buckling resistance under propagation pressure.

An experimentation on gravity influence in concentric tube heat pipe heat exchanger using various working fluids

In present work the experimentation is carried out in the heat pipe introduce inside concentric-tube heat exchanger. Methanol, Acetone as working fluids, and water as heat transport fluid. The investigation is done by different mass flow rates and temperatures of the fluids. The effect of gravitational angles for 0° and 90° are experimented. The maximum heat transfer performance is obtained at angle is 0°. In this investigation for acetone as working fluid there is an increment of 30.42% for effectiveness, 2.5% for Reynolds number and 21.57% decrease in thermal resistance than with methanol. This experimentation clearly shows that heat pipe heat exchanger with acetone exhibits enhanced performance when related with methanol.

An experimental inquisition of waste heat recovery in electronic component system using concentric tube heat pipe heat exchanger with different working fluids under gravity assistance

In the utilizing of the waste heat in the electronic components meets the power demand and energy utilization for the industries and domestic applications. To meet out this by the understanding and optimization of the waste heat utilization by a compact and cost effective device using heat pipe heat exchanger. This paper states with the design, fabrication, development, and observation of an experimental investigation of the heat pipe introduce in the concentric tube heat exchanger. Working fluids like Methanol, Acetone and heat transport fluid as water. The investigation is further extended by varying the inclination angles, mass flow rates, and temperatures of hot and cold fluid at inlet conditions. The influence of gravitational effect on the heat pipe heat exchanger is conducted for inclination angle from 10° to 80° and the maximum performance is obtained at 60° inclination angle. It is observed while acetone as working fluid there is an increase in 29.75% for effectiveness, 79.81% as heat transfer coefficient, 39.53% as heat transfer rate, 6.70% for Reynold's number and 10.52% decrease in thermal resistance than with methanol. It is concluded that the acetone exhibits better performance when related with methanol as a working fluid. These observations show the suitability of the designed concentric tube heat pipe heat exchanger for the utilization of waste heat dissipation in electronic component system.

Verification of numerical models for seismic fluid‐structure interaction analysis of internal components in liquid‐filled advanced reactors

AbstractEarthquake shaking of a liquid‐filled advanced reactor induces fluid‐structure interaction (FSI) between the reactor vessel (tank), its internal components, and the contained liquid. Seismic design, qualification, and risk assessment of such reactors must consider fluid‐structure responses, their geometries and support conditions, and three‐directional seismic inputs, all of which require numerical simulations. Numerical models used for analysis of safety‐related nuclear equipment must be verified and validated. This paper verifies numerical models of submerged components using analytical solutions. Seismic FSI analysis of the numerical models is performed using the Arbitrary Lagrangian‐Eulerian (ALE) and Incompressible Computational Fluid Dynamics (ICFD) solvers in LS‐DYNA. Prior analytical solutions are reworked in this paper, and calculation errors are identified and corrected. The solutions address frequencies of two concentric cylindrical pipes filled with liquid: the inner pipe is a submerged component, and the outer pipe contains the liquid. A unitless frequency coefficient is defined and presented for pipes of different materials, filled with different liquids, and with a range of dimensions for application to advanced reactors. The numerical models are verified here by comparing the lateral frequencies of submerged components with those calculated using the corrected analytical solutions. Recommendations for verification of numerical models of internal components in advanced reactors for seismic FSI analysis are provided. Although the unitless frequency coefficients and verification procedures are developed for application to advanced nuclear reactors, they are broadly applicable to FSI analysis of submerged components in liquid‐filled vessels such as storage tanks, boilers, and steam generators.

CFD Modelling of Dispersed Bubble Two-Phase Flow in a Concentric Annulus Pipe

CFD Modelling of Dispersed Bubble Two-Phase Flow in a Concentric Annulus Pipe

Fully developed forced convective Jeffrey fluid flow through concentric pipes annular duct

The purpose of present study is to determine the influence of constant pressure gradient on flow and heat transfer rate of Jeffrey fluid through concentric pipes annular sector duct. Finite volume method and strongly implicit procedure are used to simulate the governing system of partial differential equations. The results are estimated both in graphical and tabular forms for different values of the parameters. The favorable results have been observed in the case of friction factor, when we increase the value of ratio of relaxation to retardation times, $$\lambda $$ , however, forced convective heat transfer rate almost remains invariant in the absence of viscous dissipation. With the increase in value of Brinkman number, Br, the effect of viscous dissipation becomes favorable upto 9.64 $$\%$$ on heat transfer rate for higher value of $$\lambda $$ at ratio of radii, $$\hat{\xi }=0.25$$ and apex angle, $$\beta =\pi /6$$ of the concentric pipes annular sector duct.

Structure of stationary gas slug in an annular channel

Experimental study of liquid flow structure around a stationary gas slug in an annular channel was performed. The channel consisted of two concentric pipes with the diameters of 32 and 10 mm. Slug was produced in a downward liquid flow in an annular channel. Wall shear stress distribution was measured in both walls of the channel using an electrodiffusional technique. It was shown that the shape of the slug in the annular channel differs significantly from that in a circular pipe. The distribution of wall shear stress along the slug was presented for different angular positions in the channel.

Effects of radius ratio on turbulent concentric annular pipe flow and structures

The effects of radius ratio on fully-developed turbulent concentric annular pipe flow and structures are investigated using direct numerical simulations (DNS). In order to study the radius ratio effects on the flow, four radius ratios of a concentric annular pipe (for Ri∕Ro=0.1–0.7) are compared at a fixed Reynolds number. Here, Ri and Ro are the radii of the inner and outer pipes, respectively. It is observed that the radius ratio influences the interaction of two boundary layers developed over the inner and outer cylinder surfaces, and has a significant impact on the turbulent flow structures and dynamics. The characteristics of the flow field are investigated in both physical and spectral spaces, which include the analyses of the first- and second-order statistical moments, budget balance of the transport equation of Reynolds shear stress, two-point correlation coefficients, and premultiplied spectra of velocity and vorticity fluctuations.

Thermal and Flow Characteristics in a Concentric Annular Heat Pipe Heat Sink

A concentric annular heat pipe heat sink (AHPHS) was proposed and fabricated to investigate its thermal behavior. The present AHPHS consists of two concentric pipes of different diameters, which create vacuumed annular vapor space. The main advantage of the AHPHS as a heat sink is that it can largely increase the heat transfer area for cooling compared to conventional heat pipes. In the current AHPHS, condensation takes place along the whole annular space from the certain heating area as the evaporator section. Therefore, the whole inner space of the AHPHS except the heating area can be considered the condenser. In the present study, AHPHSs of different diameters were fabricated and studied experimentally. Basic studies were carried out with a 50 mm-long stainless steel AHPHS with diameter ratios of 1.1 and 1.3 and the same inner tube diameter of 76 mm. Several experimental parameters such as volume fractions of 10–70%, different air flow velocity, flow configurations, and 10–50 W heat inputs were investigated to find their effects on the thermal performance of an AHPHS. Experimental results show that a 10% filling ratio was found to be the optimum charged amount in terms of temperature profile with a low heater surface temperature and water as the working fluid. For the methanol, a 40% filling ratio shows better temperature behavior. Internal working behavior shows not only circular motion but also 3-D flow characteristics moving in axial and circular directions simultaneously.

The Effect of Inclination on the Stability of Foam Systems in Drilling and Well Operations

SummaryTo minimize fluid loss and the associated formation damage, foam is a preferred fluid to perform cleanout operations and reestablish communication with an open completion interval. Because of their high viscosity and structure, foams are suitable cleanout fluids when underbalanced well-cleanout operations are applied. Although several studies have been conducted to better understand foam-flow behavior and hydraulics, investigations performed on foam stability are very limited. Specifically, very little is known regarding the impact of wellbore inclination on the stability of foams. Unstable foams do not possess high viscosity, and as a result, they are not effective in cleanout operations, especially in inclined wellbores. Predicting the downhole instability of foam could reduce the number of drilling problems associated with excessive liquid drainage, such as temporary overbalance, formation damage, and wellbore instability. The objectives of this study are to investigate the effects of wellbore inclination on the stability of various types of foams and develop a method to account for the effect of inclination on foam stability in inclined wells.In this study, foam-drainage experiments were performed using a flow loop that consists of a foam-drainage-measurement section and pipe viscometers. To verify proper foam generation, foam viscosity was measured using pipe viscometers and compared with previous measurements. Drainage experiments were performed with aqueous, polymer-based, and oil-based foams in concentric annulus and pipe under pressurized conditions. Tests were also conducted in vertical and inclined orientations to examine the effect of wellbore inclination on the stability of foams. The foam-bubble structure was examined and monitored in real time using a microscopic camera to study bubble coarsening. The foam quality (i.e., gas volume fraction) was varied from 40 to 80%.Results show that the drainage rates in the pipe and annular section were approximately the same, indicating a minor effect of column geometry. More importantly, the drainage rate of foam in an inclined configuration was significantly higher than that observed in a vertical orientation. The inclination exacerbated foam drainage and instability substantially. The mechanisms of foam drainage are different in an inclined configuration. In inclined wellbores, drainage occurs not only axially but also laterally. As a result, the drained liquid quickly reaches a wellbore wall before reaching the bottom of foam column. Then, a layer of liquid forms on the low side of the wellbore. The liquid layer flows downward because of gravity and reaches the bottom of the test section without facing the major hydraulic resistance of the foam network. This phenomenon aggravates the drainage process considerably.Although foam-drainage experiments have been reported in the literature, there exists only limited information on the effects of geometry and inclination on foam drainage and stability. The information provided in this paper will help to account for the effect of inclination on foam stability and subsequently improve the performance of oilfield operations involving foam as the working fluid.

Microwave Holographic Imaging of Nonmetallic Concentric Pipes

Recently, nonmetallic materials, which are resilient to corrosion, low cost, and lightweight, have been exploited in many industrial sectors such as oil and gas field. A common application of them is in the form of pipes. Despite the advantages, these pipes can be damaged by delamination, defects, holes, and erosion, which may lead to major production failures or even environmental catastrophes. To prevent these issues, nondestructive testing (NDT) of these pipes is required to replace these components in a timely manner. Due to the fact that the traditional NDT methods are mostly effective for metallic pipes, microwave holographic imaging is proposed for inspection of multiple concentric nonmetallic pipes. Besides, standardized minimum norm (SMN) is used to mitigate the depth biasing problem in the proposed imaging technique. To reduce the complexity of the imaging system, we aim at using the narrowest possible frequency band using an array of receiver antennas. The performance of the proposed NDT method is validated through simulation and experimental data in two scenarios including the antennas placed outside the pipes and inside the pipes.

Development of Unidirectional Cellular Structure with Multiple Pipe Layers and Characterisation of Its Mechanical Properties.

This study is concerned with the development of a new unidirectional cellular (UniPore) copper structure with multiple concentric pipe layers. The investigated UniPore structures were grouped into three main types, each having a different number of pipes (3, 4, and 5 pipes per transversal cross-section) and different pore arrangements. The specimens were fabricated by explosive compaction to achieve tightly compacted structures with a quasi-constant cross-section along the length of the specimens. The bonding between copper pipes was observed by a metallographic investigation, which showed that the pipes and bars were compressed tightly without voids. However, they were not welded together. The mechanical properties were determined by quasi-static compressive testing, where the typical behaviour for cellular materials was noted. The study showed that porosity significantly influences the mechanical properties, even more so than the arrangement of the pipes.

Dynamic characteristics and stability of pipe-in-pipe system conveying two-phase flow in thermal environment

Pipe-in-pipe (PIP) systems are utilized widely in modern petroleum industry owing to their good insulation effect. In present work, a novel mathematical model for the free vibration of the fluid-conveying cantilevered PIP system considering thermal effect and two-phase flow is proposed. The insulation layer connecting two concentric pipes is simplified as the distributed springs and dampers here. The governing equation of the pipe system is then derived using Hamilton's principle based on Euler-Bernoulli beam theory. Then the Galerkin method is applied to the free vibration analysis. In the numerical section, parametric analysis is performed to elucidate the effects of different physical factors, such as environment temperature, equivalent stiffness and damper of the insulation layer, structural damping, two-phase flow, and axial load on the dynamic characteristic and stability of the PIP system through the forms of Argand diagram, stability map, and time history diagram. The results show that the PIP system has an advantage over a single fluid-conveying pipe in terms of stability considering thermal effect, axial load, and structural damping. Besides, different from single pipe, two different frequencies are found for each vibration mode, and two-pipe coupled flutter instability occurs to the PIP system as the fluid velocity exceeds the critical fluid velocity. The theoretical work is helpful to improve the analysis and design of the PIP system with consideration of internal two-phase flow and environmental temperature.

Effect of vibrator position and frequency on heat transfer enhancement in counter flow concentric pipe heat exchanger

Purpose This paper aims to deal with heat transfer enhancement because of transverse vibration on counter flow concentric pipe heat exchanger. Experiments were performed at different vibrator positions with varying amplitudes and frequencies. Design/methodology/approach Tests are carried out at 4 different vibration frequencies (20, 40, 60 and 100 Hz), 3 vibration amplitudes (23, 46 and 69 mm) and at 3 vibrator positions (1/4, 1/2 and 3/4 of pipe length) with respect to hot water inlet under turbulent flow condition. Findings Experimental results indicate that Nusselt number is enhanced to a maximum extent of 44% with vibration when compared to Nusselt number without vibration at a frequency of 40 Hz, an amplitude of 69 mm and at a vibrator position of one-fourth of pipe length with respect to hot water inlet. Originality/value Empirical correlation is developed from experimental data to estimate the heat transfer coefficient with vibration for experimental frequency range with an error estimate of approximately ±10%.

Entropy Analysis of a Variable Viscosity MHD Couette Flow Between Two Concentric Pipes with Convective Cooling

This paper addresses the combined effects of the magnetic field, thermal buoyancy force, viscous dissipation, Joule heating and temperature-dependent viscosity on the Couette flow of an incompressible conducting fluid between two concentric vertical pipes. It is assumed that convective cooling occurs at the surface of the outer moving pipe while the surface of the inner fixed pipe is maintained at a constant temperature. The nonlinear equations for momentum and energy are obtained and solved numerically using a shooting method coupled with the Runge-Kutta-Fehlberg integration procedure. Relevant results depicting the effects of embedded thermophysical parameters on the velocity and temperature profiles, skin friction, the Nusselt number, entropy generation rate and the Bejan number are presented graphically and discussed. It is found that an increase in the magnetic field intensity boosts the entropy generation rate while an increase in convective cooling lessens it.

Emissions down the drain: Balancing life cycle energy and greenhouse gas savings with resource use for heat recovery from kitchen drains

Although the food service sector is a major user of water, the potential for heat recovery from commercial kitchens’ drain water remains largely unexplored. For the first time, we compare the life cycle environmental burdens of producing and installing a heat recovery system with the environmental credits arising from energy savings for a restaurant case study, and for the entire UK food service sector. Life Cycle Assessment was applied to determine the impacts of heat recovery systems made from different materials and comprising a heat exchanger in the shape of a concentric double-walled pipe, pipework and fittings. The design option with the smallest environmental footprint combined a heat exchanger made out of polypropylene-graphite (PP-GR) with polyethylene pipework, exhibiting 80–99% less environmental impact compared with components made out of (35% recycled) copper. Contrasting the environmental impacts of two heat recovery set-ups with energy savings shows that a PP-GR based system pays back all burdens of the seven assessed environmental impact categories, within two years, while payback times for the copper-based system vary depending on the replaced energy source, and can exceed the 10 year operational lifetime of the system. When looking at typical flow-rates in UK food outlets, net environmental savings can be realised across all analysed impact categories above a threshold water consumption of 555 L/day, using current technology. Extrapolation to the UK food service sector indicates annual greenhouse gas emission mitigation potential of about 500 Gg CO2 equivalent.

Comparative studies on micro cogeneration, micro cogeneration with thermal energy storage and micro trigeneration with thermal energy storage system using same power plant

Present work deals with the three modes of power generation i.e. cogeneration (or combined heating and power), cogeneration with thermal energy storage and trigeneration with thermal energy storage and their comparison. Stationary compression ignition engine of 4.4 kW was used for power generation and all three modes were experimentally investigated. Cogeneration was achieved by coupling the engine with concentric tube or double pipe type heat exchanger. For cogeneration with thermal energy storage mode above setup was coupled with an erythritol filled shell & tube type heat exchanger and trigeneration with thermal energy storage mode was achieved by the addition of vapour absorption refrigeration system. Experiments were carried out for all three modes and comparative results are reported in this paper. Maximum useful energy output for trigeneration with thermal energy was 7.27 kW at an engine load of 4.4 kW. Reduction in emissions of CO2 in kg/kWh in case of trigeneration with thermal energy storage was 54.92% at a load of 4.4 kW as compared to single generation.

On the rise characteristics of Taylor bubbles in annular piping

A three-dimensional phase-field lattice Boltzmann method has been applied to investigate the rise of Taylor bubbles within annular pipes. The approach couples the conservative phase-field model with a velocity-based lattice Boltzmann scheme. The implementation uses 27 discrete velocities to resolve both the interfacial dynamics and the hydrodynamics. To assist numerical stability for the high-density ratio, two-phase flows a weighted multiple-relaxation-time collision operator is employed. This paper makes contributions in three areas. First, the model is employed to capture the behaviour of Taylor bubbles in five combinations of vertical annular pipes, with results compared to experimental findings from the literature for air-water flows. From this, shortcomings were identified in the ability of existing correlations to accurately predict rise velocities for bubbles in various liquids. Second, the effect of pipe inclination on the rise behaviour of the bubbles was investigated. From the findings, a preliminary correlation describing the rise velocity was proposed. The first two components of the study were conducted with the Taylor bubble rising in stagnant fluid. The final component of this study imposed liquid flow in a concentric annular pipe to determine the impact of this on the bubble’s dynamics. The liquid velocity was defined through a Reynolds number based on the average inlet velocity up to an absolute value of 10. The viscosity was varied to examine Morton numbers from 2.56e-3 to 6.55e-5. To this end both co- and counter-current flow was analysed and a distribution parameter proposed to capture the liquid-gas interaction. To extend this work, future investigations will look to extend the parameter range assessed to ensure the universality of the correlations identified.

Design and Development of Solar-biogas Hybrid Dryer for Onion Drying

A solar-biogas hybrid dryer was designed, developed and tested for onion drying with a capacity of 8 kg/batch. Solar energy was utilized as primary energy for onion drying in a greenhouse type drying chamber (direct solar) and biogas powered air heater used as a supplementary heat source for continuous operation. The hybrid dryer consists of greenhouse type drying chamber, concentric pipe air heater and biogas burner. The greenhouse type drying chamber has floor area of 1300 mm×900 mm and collector area of 3 m2. The dryer was operated as a solar dryer during normal sunny day and hybrid mode whenever sunlight is insufficient to maintain desired 60°C inside the drying chamber. The results indicated that the moisture content of onion slices reduced from 80.06% (wb) to 9.88% (wb) in 12 hours in hybrid mode drying. A biogas powered air heater operated for 3 hours in a day with effectiveness of 0.87 and biogas burner efficiency of 47.59%. The dryer was techno-economically feasible with a benefit cost ratio of 1.12 and payback period of 2.1 years.

Influence of domain size on direct numerical simulation of turbulent flow in a moderately curved concentric annular pipe

Direct numerical simulation (DNS) of turbulent flow in a concentric annular pipe was performed using a pseudo-spectral method computer code. In order to study the effects of computational domain size on the turbulence statistics, 12 test cases of different domain sizes are compared. The characteristics of the velocity field are examined at two different Reynolds numbers. It is observed that the predictive accuracy of the first- and second-order statistics is sensitive to the axial and azimuthal domain sizes. It is also found that the scales and dynamics of turbulence structures vary with the surface curvature of the concave and convex walls. The characteristic length scales of the turbulence structures are identified through a spectral analysis, and it is observed that a minimum computational domain is required in order to accurately capture the near-wall streaky and hairpin structures of a concentric annular pipe flow using DNS.