Large Diameter Tubes Research Articles

Development of a Process for Deformation-Thermal Production of Tube Strip Steels of Elevated Strength Categories

Physical simulation of a process of production of tube strip steels of strength category X80 for large-diameter oil and gas transportation tubes is performed. Mechanical properties of the steels are determined. Two processes (basic and alternative ones) are suggested for making strips of strength category X80.

Effects of parameters on performance of high temperature molten salt latent heat storage unit

In order to investigate the performance of high temperature molten salt latent heat storage (LHS) unit under variable conditions, the effects of heat transfer fluid (HTF) inlet temperature, velocity and tube geometric parameters on melting time, melting fraction, heat storage rate and solid–liquid interface were numerically investigated. The results show that within the studied parameters, the HTF inlet temperature has the largest effect on LHS rate. With the HTF inlet temperature increasing from 1070 K to 1110 K, the melting time reduces 53.0%. However, the larger inlet temperature will result in more non-uniform melting rate and solid–liquid interface distribution. The second important influential factor is the HTF inlet velocity. When inlet velocity increases from 10 m/s to 20 m/s, the melting time reduces 45.4%. And the effect of velocity on the solid–liquid interface distribution is uniform. LHS tube diameter has the lowest effect on performance. With outer tube radius increasing from 24.0 mm to 28.0 mm, the melting time only augments 16.3% and the solid–liquid interface distribution becomes more uniform. In a general conclusion, when the heat load of the heat source is larger, a larger HTF mass flow rate is suitable to maintain a moderate HTF temperature. And then for the LHS unit, a larger tube diameter is recommendable.

Divacancies in carbon nanotubes and their influence on electron scattering

First-principles calculations are applied to study the formation energies of various divacancy defects in armchair and zigzag carbon nanotubes of varying diameter, and the transport properties for the corresponding structures. Our explicit ab initio calculations confirm that the lateral 585 divacancy is the most stable defect in small diameter tubes, with the 555 777 divacancy becoming more stable in armchair tubes larger than (30, 30). Evaluating the electron transmission as a function of diameter and chirality for a range of defects, the strongest scattering is found for the 555 777 divacancy configuration, which is observable in electrical spectroscopy experiments. Finally, validation of an approximation relating contributions from independent scattering sites enables the study of the characteristic localization length in large diameter tubes. Despite the fixed number of channels, localization lengths increase with increasing diameter and can exceed 100 nm for typical defect densities.

Some Advances in Plastic Forming Technologies of Titanium Alloys

To satisfy the ever increasing demands of high performance and light weight in high-end equipments, the titanium components are designed to have complex shape and specific performance. Research and development of advanced plastic forming technologies are of great importance to manufacturing these titanium products with low cost and short cycle. The local loading forming technology with advantages in reducing forming load, enlarging forming size and enhancing forming limit and precision through control of unequal deformation provides a feasible way to manufacture the high performance and light weight titanium components (large-scale, integral, complex, thin-walled) widely used in aircrafts and shows a good developing prospect. This paper presents the state of the art of local loading forming technology and its applications in manufacturing titanium components in the authors’ laboratory, including the isothermal local loading forming of large-scale complex TA15 bulkhead, and heat rotary draw bending of large-diameter thin-walled titanium tube.

Preparation of large diameter and low density ZnS microtube arrays via a sacrificial template method

The uniform low density ZnS microtube arrays with a large diameter of up to 1um are prepared for the first time via a three-step approach. ZnO microrod arrays are first hydrothermally grown on fluorinated tin oxide glass as a sacrificial template, which are converted to ZnO/ZnS core/shell structures subsequently through a sulfidation process, ZnS microtube arrays are then obtained by selectively etching of ZnO cores. The unique properties of this large diameter and low density ZnS tube array are demonstrated by comparing it with those of small diameter and high density ZnS tube array for use in the hybrid film photoelectrode of dye-sensitized solar cells.

Design of a passive residual heat removal system for the FUJI-233Um molten salt reactor system

This paper discusses the design and analysis of a passive decay heat removal system for a Molten Salt Reactor (MSR) of 450MWth. Following the disaster at the Fukushima-1 nuclear power station, it is clear that the public will demand improved safety performance if nuclear power is to be accepted as a sustainable source of CO2-free energy. In this scope, thorium-based MSRs have very promising properties in the area of passive safety, resource availability and proliferation resistance. Molten Salt Reactor (MSR) systems can be equipped with an emergency salt drain tank. Under any severe accident, all the fuel salt can be drained by gravity into the drain tank, thus, the primary system can be safely emptied of fissile materials and fission products. The ultimate safety can be assured by the integrity of the fuel salt in the drain tank or in other words, the capability of residual heat removal from the fuel salt in the drain tank. From this point of view, we investigated the feasibility of a passive residual heat removal system for the drain tank of an MSR (FUJI-233Um of 450MWth). We concluded that a system comprising a large drain tank and 60, large-diameter coolant tubes can withstand the thermal shock due to the hot fuel salt, and therefore we conclude that system is feasible.

Research on Machinability of the Shell Materials and Tools' Failure

Large cylindrical shell is a large diameter and thick wall tube part working in high temperature and high pressure environment. It is made of 2.25Cr-1Mo-0.25V high strength steel, whose machinability is special. The characteristics of cutting temperature and cutting force are researched in the cutting process by analyzing the machinability of 2.25Cr-1Mo-0.25V steel in this paper. And the main tool failure modes are analyzed in the cutting process, combining with empirical approach to compare tool failure modes under cutting different steels. The high efficiency cutting measures are proposed in tool optimization design finally, in order to provide a reference for high efficiency machining of large cylindrical materials.

Bandstructure modulation for Si-h and Si-g nanotubes in a transverse electric field: Tight binding approach

We have investigated the electronic properties of SiNTs, under the external electric field, using Tight Binding (TB) approximation. It was found that the energy levels, energy gaps, and density of states (DOS) strongly depend on the electric field strength. The large electric strength leads to coupling the neighbor subbands and induce destruction of subband degeneracy, increase of low-energy states, and strong modulation of energy gap which these effects reflect in the DOS spectrum. It has been shown that, the band gap reduction of Si g-NTs is linearly proportional to the electric field strength. The band gap variation for Si h-NTs increases first and later decreases (Metallic) or first remains constant and then decreases (semiconductor). Also we show that the larger diameter tubes are more sensitive to the field strength than smaller ones. The semiconducting metallic transition or vice versa can be achieved through an increasing of applied fields. Number and position of peaks in DOS spectrum are dependent on electric field strength.

Fabrication of large-diameter tube-like mesoporous TiO2 via homogeneous precipitation and photocatalytic decomposition of papermaking wastewater

Large-diameter tube-like mesoporous TiO2 nanotubes were synthesized via homogeneous precipitation from aqueous solutions containing titanium oxysulfate (TiOSO4) using urea. The cationic surfactant cetyltrimethylammonium bromide was used as a structure-directing agent. Prepared samples were characterized by X-ray diffraction, transmission electron microscopy (TEM), field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and N2 adsorption–desorption isotherms. Experimental results indicated that the samples exhibit tube-like structures with lengths of approximately 6μm to 8μm, large tube diameters of approximately 500nm to 600nm, and a wall thickness of approximately 450nm. TEM images and N2 adsorption–desorption isotherms showed that the tube walls of the samples have a uniform mesoporous structure. A possible mechanism for the formation of tube-like mesoporous TiO2 was proposed. The photocatalytic activities of the large-diameter tube-like mesoporous TiO2 were assessed via the photocatalytic decomposition of papermaking wastewater under ultraviolet light irradiation. The effects of different parameters such as UV light irradiation, catalyst dosage and solution pH on photocatalytic activities of tube-like mesoporous TiO2 were studied. The as-synthesized tube-like TiO2 showed higher photocatalytic activities than Degussa P25. MTS3 exhibited the highest photocatalytic activity. The chemical oxygen demand and chroma percent degradations of papermaking wastewater were approximately 73.0% and 99.5%, respectively, at MTS3 dosage of 1.0g/L and pH value of 3.0 after 12h of photodegradation.

Technology Focus: Coiled Tubing Applications (June 2013)

Technology Focus In the two previous JPT coiled-tubing features, I commented on the remarkable growth the coiled-tubing industry has seen in North America, resulting largely from the shale revolution. This growth attracted numerous new players into the industry, in addition to the capacity additions made by the existing service providers. Regrettably, such unrestrained growth is rarely accompanied by a matching level of service quality. This concern about performance prompted the selection of the first paper in this feature. Although this is just one service provider’s history of stuck pipe, it likely mirrors the performance of the industry at large and serves as a reminder to all operators of the risks inherent in being too rigorous in adopting a cookie-cutter approach to certain coiled-tubing operations. The authors are to be commended for their frank reporting of the issues. In fact, the gallop toward ever-larger coiled-tubing strings has not been mirrored by increasing the size of the reels on which they are spooled. The result is that, in addition to increasing the hoop stress resulting from ever-increasing injection pressures, coiled tubing is being subjected to levels of strain that have not been encountered previously. This places strenuous demands on the bias welds in the strings and requires more-rigorous attention to string-fatigue management. This continues to be a focus of the industry, as does the slightly greater susceptibility of bias welds to pitting corrosion from recirculated formation water of varying origins. While I am still on the subject of large-diameter coiled tubing, the second paper focuses on another aspect of the industry and highlights the level of engineering detail required of many coiled-tubing activities and is especially typical of large multiwell offshore projects. It serves as an example of the level of planning and professionalism required for multidisciplinary operations but also reminds us that many superficially basic well-intervention operations are never as simple as they might appear. Finally, I could not resist a paper of a more theoretical nature because it addresses an activity of increasing importance to the industry—namely, extended reach—which, in turn, is the primary driver behind the use of larger sizes of coiled tubing. We need technology and the science behind it if we are ever going to come close to approaching the lateral reach available to the drillers. Recommended additional reading at OnePetro: www.onepetro.org. SPE 162797 New Coiled-Tubing-Deployed Multizone Stimulation Method Increases Reservoir Access by Tyson Dunlop, Halliburton, et al. SPE 163910 Coiled-Tubing-Jet-Cutting Multiple-Stage Fracture Treating Improves Fracture-Treatment Techniques To Unlock Bypassed Reserves in Cotton Valley Sands, Dorcheat Macedonia Field, Magnolia, Arkansas by R.W. Pomrenke, Bonanza Creek Energy, et al. SPE 163884 Development of a New Coiled-Tubing Life-Tracking Process by Kenneth R. Newman, KNewman Engineering

Selective growth of single-walled carbon nanotubes over Co–MgO catalyst by chemical vapor deposition of methane

The selective synthesis of SWCNTs with narrow chirality and diameter distribution by methane decomposition over a Co–MgO catalyst is reported. Raman spectroscopy, temperature programmed oxidation (TPO), UV–Vis–NIR absorption spectroscopy, and nitrogen physisorption were used to probe SWCNTs morphology, reaction selectivity, SWCNTs chirality and diameter distribution, and carbon yield. The catalyst was examined by nitrogen physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), and UV–Vis-diffuse reflectance spectroscopy to elucidate the structure and chemical state of the species responsible for SWCNT growth. The results established a clear link between the degree of dispersion of Co species inside the MgO lattice and the catalyst activity and selectivity for SWCNT growth. High dispersion and stabilization of Co species influenced catalytic activity for methane decomposition and the high SWCNT selectivity. The yield of carbon and SWCNT selectivity increased with an increase in temperature, however, SWCNTs diameter distribution shifts to larger diameter tubes as synthesis temperature was increased.

TiO2 Nanotubes Formed in Aqueous Media: Relationship between Morphology, Electrochemical Properties and the Photoelectrochemical Performance for Water Oxidation

The effect of voltage and electrolyte composition on the formation of TiO2 nanotube films over its morphology, semiconductor properties and photoelectrochemical performance for water oxidation was studied. TiO2 nanotube films were formed by potentiostatic anodization in 0.1 M H2SO4/0.05 M HF and 0.1 M H2SO4/0.05 M NH4F during 1 h at four different voltages. SEM images showed a more significant chemical attack when NH4F was employed, evidenced by larger tube diameters and thinner films. The semiconductor properties were altered by the nature of the counterEion utilized during film growth, obtaining films with a higher density of donor and less positive flat band potential in NH4F electrolytes. The films formed in NH4F showed higher photopotentials and photocurrent related to the modification of their morphology and semiconductor properties; attaining a maximum at formation voltage of 15 V.

Spontaneous Partition of Carbon Nanotubes in Polymer-Modified Aqueous Phases

The distribution of nanoparticles in different aqueous environments is a fundamental problem underlying a number of processes, ranging from biomedical applications of nanoparticles to their effects on the environment, health, and safety. Here, we study distribution of carbon nanotubes (CNTs) in two immiscible aqueous phases formed by the addition of polyethylene glycol (PEG) and dextran. This well-defined model system exhibits a strikingly robust phenomenon: CNTs spontaneously partition between the PEG- and the dextran-rich phases according to nanotube's diameter and metallicity. Thermodynamic analysis suggests that this chirality-dependent partition is determined by nanotube's intrinsic hydrophobicity and reveals two distinct regimes in hydrophobicity-chirality relation: a small diameter (<1 nm) regime, where curvature effect makes larger diameter tubes more hydrophobic than small diameter ones, and a large diameter (>1.2 nm) regime, where nanotube's polarizability renders semiconducting tubes more hydrophobic than metallic ones. These findings reveal a general rule governing CNT behaviors in aqueous phase and provide an extremely simple way to achieve spatial separation of CNTs by their electronic structures.

TiO2 Nanotubes Formed in Aqueous Media: Relationship between Morphology, Electrochemical Properties and Photoelectrochemical Performance for Water Oxidation

This paper studies the effect of voltage and electrolyte composition on the morphology of TiO2 nanotube films, their semiconductor properties and photoelectrochemical performance for water oxidation. TiO2 nanotube films were formed by potentiostatic anodization in fluoride containing electrolytes (using either HF or NH4F) during 1 h at four different voltages and were heat treated at 450°C to obtain anatase polymorph. SEM images showed a more significant chemical attack when NH4F was employed, which was evidenced by larger tube diameters and thinner films. UV-vis reflectance spectra showed that the TiO2 films formed in aqueous electrolyte were highly defective, presenting various broad absorption peaks in the visible region attributed to the sub-bandgap energy states. The semiconducting properties were modified by the nature of the counter-ion utilized during film growth, resulting in films with a higher donor density and a lower flatband potential in NH4F electrolytes. The films formed in NH4F showed higher photopotentials and photocurrents related to the modification of their morphology and semiconducting properties, attaining a maximum at a formation voltage of 15 V.

Use of light wand as an adjunct during intubation of patient with large epiglottic cyst

Use of light wand as an adjunct during intubation of patient with large epiglottic cyst

Effect of flame spray coating on falling film evaporation for multi effect distillation system

Horizontal tube falling film evaporators find various applications like multi effect distillation for sea water desalination, power and process applications, refrigeration applications, etc. In this system, latent heat released inside the tube due to condensation is transferred to the falling film on the tube surface resulting in convective evaporation. Among many heat transfer enhancement techniques, thermal spray coatings enjoy diverse applications with economic advantage for commercial applications. This paper focuses on Computational Fluid Dynamic(CFD) analysis of falling film evaporation of water on horizontal tubes under the influence of gravity at vacuum. ANSYS Fluent with VOF two-phase model is used for the falling film studies on the horizontal tube. Half section of the tube is modeled with gravitational flow of sea water from the top. This model is used to predict the enhancement in convective evaporation on thermal spray coated tube surface with varying roughness. These CFD results are validated with published experimental data available in the literature. From this study, it is observed that heat transfer coefficient is increased by 10–15% due to increased roughness for laminar convective film boiling under vacuum. The film coefficient enhancement is higher for the larger diameter tubes. The tubes in the tube bank located beneath the top tube exhibit reduction in performance, which may be due to partial drying out of film on tube surface or due to evaporation and maldistribution of flow. At high heat flux and low feed rate, the decrease in film coefficient is more predominant. The effect of feed rate, tube diameter, wall temperature, heat flux, tube arrays, etc. on the heat transfer characteristics is studied and presented in this paper.

Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes

The critical heat flux look-up table was applied to a large diameter tube, namely 67 mm inside diameter tube, to predict the occurrence of the phenomenon for both vertical and horizontal uniformly heated tubes. Water was considered as coolant. For the vertical tube, a diameter correction factor was directly applied to the 1995 critical heat flux look-up table. To predict the occurrence of critical heat flux in horizontal tube, an extra correction factor to account for flow stratification was applied. Both derived tables were used to predict the effect of high heat flux and tube blockage on critical heat flux occurrence in boiler tubes. Moreover, the horizontal tube look-up table was used to predict the safety limits of the operation of boiler for 50% allowable heat flux.

Enhanced electrical properties of vertically aligned carbon nanotube-epoxy nanocomposites with high packing density

During their synthesis, multi-walled carbon nanotubes can be aligned and impregnated in a polymer matrix to form an electrically conductive and flexible nanocomposite with high backing density. The material exhibits the highest reported electrical conductivity of CNT-epoxy composites (350 S/m). Here, we show how conductive atomic force microscopy can be used to study the electrical transport mechanism in order to explain the enhanced electrical properties of the composite. The high spatial resolution and versatility of the technique allows us to further decouple the two main contributions to the electrical transport: (1) the intrinsic resistance of the tube and (2) the tunneling resistance due to nanoscale gaps occurring between the epoxy-coated tubes along the composite. The results show that the material behaves as a conductive polymer, and the electrical transport is governed by electron tunneling at interconnecting CNT-polymer junctions. We also point out the theoretical formulation of the nanoscale electrical transport between the AFM tip and the sample in order to derive both the composite conductivity and the CNT intrinsic properties. The enhanced electrical properties of the composite are attributed to high degree of alignment, the CNT purity, and the large tube diameter which lead to low junction resistance. By controlling the tube diameter and using other polymers, the nanocomposite electrical conductivity can be improved.

Temperature Field and Extrusion Load in Needle Piercing Extrusion Process Based on Ingot Billet for Large 7075 Aluminum Alloy Tube

Abstract. The change rules of the billet temperature field and extrusion load are the significant basis for the optimal design of the needle piercing extrusion process based on ingot billet for the manufacture of large-diameter thick-walled tube. Taking the needle piercing extrusion process of a 7075 aluminum alloy tube with sizes of Φ500mmx400mm/6000mm as study object, we developed a precise FE model for the process under DEFORM-2D environment, then numerically revealed the distributions and evolution rules of the billet temperature field, and obtained the effects of the extrusion speed and initial billet temperature on the billet temperature filed and extrusion load. The results show that the peak extrusion load decreases linearly with the increase of initial billet temperature but is insensitive to the extrusion speed, and that the peak temperature rises with the increase of the extrusion speed and initial billet temperature, and always locates on the surface of the initially extruded tube close to the exit of the cavity die.

Measurement of Voidage of Sinter Ores in the Tubes

An industrial vertical tank (cost $200,000) was produced to recover the heat of sinter ores in our laboratory, the voidage along the height direction needs to be studied in order to determine the best height of sintering layer in it. In this paper, the bulk bed voidage of sinter ores in cylindrical polyvinylchloride tube (PVC-U) was measured by the cross-section image analysis method. The large-diameter tube was used to minimize the wall effects so that we could measure the bulk bed voidage in the center of the tube. The results show that the new method is useful, the voidage increases at lower height and fluctuates slightly between 0.36 and 0.43 in a stable stage, the voidage increases as particle size increases, decreases as the shape factor increases, and increases as the tube to particle diameter ratios decreases. These provide significant voidage data for the study of a vertical tank.