Large Diameter Tubes Research Articles

Numerical and experimental investigations on influence of spherical hinge mandrel on deformation characteristics of large diameter tube in small-radius NC rotary bending

Numerical and experimental investigations on influence of spherical hinge mandrel on deformation characteristics of large diameter tube in small-radius NC rotary bending

Experimental study of two-phase pressure-drop in horizontal return bends with ammonia

In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (R/do ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m−2 s−1, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and R/do ratio of the bend.Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.

The prospects for the use of alternative gel formers for hydraulic fracturing

The article discusses the relevance of using alternative gel-forming agents in the preparation of fracturing fluids for hydraulic fracturing (HF). Besides the obvious tasks, such as increasing the residual conductivity of the fractures created during stimulation, it also addresses the impact of alternative gelforming agents on the treatment process. The author, supported by field data, concludes that under otherwise equal conditions, replacing traditional fracturing fluids with alternative ones significantly reduces frictional pressure losses in the pipes, which is particularly important when treating deep and extensive horizontal wells with limited internal pipe diameters. Moreover, the aforementioned impact of gel-forming agents on frictional pressure losses allows for a reserve of power in the hydraulic fracturing fleet equipment. Consequently, the treatment can be performed with higher flow rates under otherwise equal conditions, without the need for additional high-pressure pumps or the deployment of more expensive, stronger, larger-diameter tubing. Another important conclusion reached by the author is that due to the specific properties of alternative fracturing fluids, their ability to transport and retain proppant is significantly increased. This property of fracturing fluids is especially important when treating low-permeability, fractured formations and during the stimulation of long horizontal wells. On the other hand, the use of alternative gel-forming agents raises the requirements for the controlled breakdown of fracturing fluids, complicating the task of selecting a rational formulation and necessitating additional research.

Aspiration tubing diameter is a key determinant of vacuum pressure and is associated with procedural outcome in mechanical thrombectomy for large vessel occlusion: An experimental and cohort study.

We (1) evaluated the effect of aspiration tubing diameter on intraluminal pressure and (2) compared thrombectomy outcomes in patients treated using small diameter tubing versus those treated using large diameter vacuum tubing. Intraluminal negative pressure was measured in a validated benchtop set up where consistency of negative pressure (inHg) was measured between static and dynamic aspiration. Static aspiration refers to activation of vacuum once the catheter is engaged with the clot. Dynamic aspiration refers to activation of vacuum when the catheter is slightly proximal to the clot. Four different sizes of vacuum tubing were trialed. We performed a retrospective analysis of consecutive patients who underwent mechanical thrombectomy. Procedural and functional outcomes were compared. The large diameter aspiration tubing held a consistent high negative pressure in static and dynamic aspiration (p = 0.152). Tubing types I to III were associated with a significant fall off in negative pressure between static and dynamic technique (p < 0.05). Two-hundred and five patients were included in the retrospective analysis; 124 (60%) underwent thrombectomy using small diameter vacuum tubing, and 81 (40%) using the large tubing. Mean thrombectomy time was shorter with the larger tubing [25.9 (17.9) minutes] versus the small tubing [37.5 (28.5) minutes, p = 0.002]. A greater proportion of patients had a thrombolysis in cerebral infarction score ≥2b in the group treated using the large tubing (78, 99%) than those with the small tubing (96, 78%, p < 0.001). Vacuum tubing diameter is linearly associated with intraluminal aspiration pressure. These findings have clinical significance as shown by increased recanalization rates and decreased thrombectomy times when large-diameter aspiration tubing is used. Shifting the paradigm toward a flow-based technique using large-bore vacuum tubing ought to be considered.

A new mechanistic model to predict liquid loading in inclined natural gas wells

Accurately predicting the critical gas velocity and inclination angle is crucial for gas field development. However, the mechanism of liquid loading remains elusive due to insufficient attention given to the multivaluedness of flow structures and phase non-uniformity. This paper theoretically studied the flow pattern and gas-liquid configuration in wellbore based on the minimum energy principle. The Kelvin-Helmholtz instability of liquid film was analyzed, and a new correlation for the interfacial friction factor was proposed based on wave properties. The results indicated that the flow pattern transitioned from stratified to annular flow as the inclination angle increased. The gas-liquid interface presented a curved shape, with the interface curvature being influenced by various factors such as fluid properties, tube diameter, inclination angle, and gas and liquid velocities. As the inclination angle increases, the critical gas velocity first increases and then decreases, reaching a peak between 44° and 59°, aligning well with experimental and conventional results. Larger tube diameter, higher liquid density, and viscosity result in a higher critical gas velocity. Waves are more prone to develop in inclined pipes, and capillary waves can break up liquid film due to instability, leading to a discontinuous flow in inclined tubes. Film instability is exacerbated by a smaller diameter, higher liquid holdup, or greater inclination angle. Finally, a new model was devised to predict liquid loading in inclined natural gas wells, demonstrating better performance than existing models. In practice, the present model can achieve real-time prediction of critical gas velocity and continuously monitor the location of liquid accumulation in gas wells over the lifespan.

Multi-objective shape characterization of airside performance in sinusoidal wavy fin-and-tube heat exchangers with large-diameter tubes using CFD

Multi-objective shape characterization of airside performance in sinusoidal wavy fin-and-tube heat exchangers with large-diameter tubes using CFD

Bending of bimetallic steel sheet on three-roll mills in the production of large diameter tubes

Bending of bimetallic steel sheet on three-roll mills in the production of large diameter tubes

Effect of vacancy defect on the structural and electrical properties of single-walled silicon nanotube

The effect of vacancy defects on zigzag and armchair single-walled silicon nanotubes (SiNTs) has been investigated using the self-consistent charge density functional tight-binding (SCC-DFTB) method. The findings indicate that the introduction of defects leads to the inability of the smaller-diameter tube to uphold its tubular structure and cluster. Conversely, the larger-diameter tube undergoes an elliptical transformation, yet retains tubular characteristics and hexagonal structures displaying specific symmetry. The double vacancy defect alters the atomic arrangement on the side opposite the defect. The stability of single-walled SiNTs is related to defect type and chiral index. In addition, the single vacancy defect increases the binding energy and stability of the zigzag tube, while causing a rapid decrease in stability of the armchair tube (7,7). The spin polarization phenomenon manifests within the defect tube, resulting in the splitting of the initial degenerate energy band and a significant decrease in its degeneracy. The existence of electronic interaction, results in a prominent manifestation of vacancy-induced magnetism in armchair and zigzag defect tubes. This phenomenon gives rise to localized spin-up bands situated below the Fermi level, as well as localized spin-down bands positioned above the Fermi level. In the energy band structure of most nanotubes, there are conduction bands or valence bands passing through the Fermi level, leading to a transition from semiconductor to semimetal or metal properties.

PULMONOLOGIST’S SATISFACTION WITH THE USE OF I-GEL LARYNGEAL MASK AIRWAY (LMA) FOR BRONCHOSCOPY IN DR. WAHIDIN SUDIROHUSODO MAKASSAR CENTRAL GENERAL HOSPITAL

Bronchoscopy is a type of endoscope used to examine internal organs in the body. This examination is performed by competent physicians, by examining the bronchi or the branches for diagnostic or therapeutic purposes. The use of the LMA for airway management during Fiberoptic Flexible Bronchoscopy (FFB) was first introduced in 1989 and was described as a safe and favorable tool for airway control during bronchoscopy in both adult and pediatric populations. The advantage of an LMA over an endotracheal tube is that it is equipped with a larger diameter tube, allowing for better visibility and flexibility. The I-gel LMA is the most frequently used type of LMA. This study aimed to determine the satisfaction of pulmonologists with the use of LMA I-gel when performing bronchoscopy in Dr. Wahidin Sudirohusodo Central General Hospital Makassar. The research employed probability sampling with an experimental design, using questionnaires for data collection. There were 36 patients underwent bronchoscopy from June ? December 2023. Demographic data were collected (age, sex, body mass index, and American Society of Anesthesiologists physical status), assessment based on the first successful attempt of fiberoptic insertion with a value of p = 0,06, quality of visualization, flexibility of the scope, size of the fiberoptic that can be used, and limitations of performance during bronchoscopy with a value of p &lt; 0,05. It was found that pulmonologists were satisfied with the use of I-gel LMA during bronchoscopy. However, this result was also influenced by the experience of pulmonologists in performing the procedure. Keywords: Bronchoscopy, LMA I-gel, Satisfaction

Airside heat transfer analysis using Wilson plot method of three analogous serpentine tube heat exchangers for aero-engine cooling

This research investigates the design, manufacture and heat transfer characteristic evaluation of three types of heat exchangers (HXs) serving for modern aero-engines. In the field of heat transfer system, previous research has concentrated on large-diameter tubes, whereas estimation for heat transfer in small-diameter tubes commonly relies on correction factors. However, small-diameter heat exchangers offer extensive applicaiton prospects in aero-engines utilizing cooled cooling air (CCA) technology, benefiting from their high heat transfer efficiency and lightweight. Hence, directly investigating compact small-diameter HXs is significant. In this paper, three analogous serpentine tube bundle HXs with different tube diameters (OD: 2.2/1.8/1.4 mm with 0.2 mm thickness) were designed by the Logarithmic Mean Temperature Difference method (LMTD). A series of comparative experiments were conducted to explore the effects of the tube diameter and flow rates on the airside heat transfer under different fuel flow conditions. The results indicate that in the case of turbulent fuel flow, decreasing the tube diameter assists in enhancing total heat transfer, whereas the trend is opposite in laminar fuel flow. In addition, during turbulent fuel flow, heat transfer capacity rises with the increase of flow rates on both sides, while variations in air flow rate have minimal impact on airside heat transfer in laminar fuel flow. Finally, the calculated heat transfer rate exceeds the experimentally measured value by no more than 15%, with this deviation escalating as the reduction of tube diameter. Subsequently, an airside Nu-Re correlation suitable for small-diameter HXs is fitted based on experimental data, with 94.1% of the data points locate in the 5% error band, providing guidance for the design and validation of aero-engine HXs in future.

Improvement of Formability in Parallel Double-Branched Tube Hydroforming Combined with Pre-Forming and Crushing Processes.

In hydroforming of parallel double-branch tubes, the material entering the branch zone is obstructed by material accumulation in the main tubes and corners, which decreases the branch height. A tube hydroforming approach is combined with pre-forming and crushing (THPC) to mitigate this problem. A larger diameter tube blank is flattened for pre-forming and then subjected to radial compression for crushing. In the next step, hydroforming forms the parallel double-branch tubes. Experiments and numerical simulations are then carried out to analyze the effect of traditional tube hydroforming (TTH) and the proposed THPC process on the formability of parallel double-branch tubes. The results show that for tubes obtained via THPC, the tube burst pressure increases by 27.5% and the branch height increases 2.37-fold compared to TTH. Additionally, the flattening, pre-forming, and crushing stages cause work hardening of the tube when using the TPHC process. Flattened tubes undergo radial compression to improve the material flowing into the branch tube. The formability of parallel double-branched tubes can be improved by using the TPHC process. Consequently, tube hydroforming, combined with pre-forming and crushing, has been confirmed as a feasible forming process for fabricating parallel double-branch tubes.

In-situ measurements of temperature and strain fields of large-diameter concrete-filled steel tube columns and the refined finite element modeling

Concrete-filled steel tube (CFST) columns are prevalent in transmission towers and arch bridges due to their cost-effectiveness and superior mechanical performance. The growing megastructures lead to large-diameter CFST components, which are exposed to the risk of early-age thermal concrete cracking. In this study, temperature and strain fields of two 2.1 m-dia. CFST columns were monitored in-situ. Within 30 h, the peak temperature and tensile strain at the centroid reached 97.0°C and 400 με, respectively. Meanwhile, temperature fields of eight scaled CFST columns were also monitored and compared. In addition, ultrasonic pulse velocity test was performed to detect the early-age thermal cracking. To predict the temperature and strain evolutions accurately, a refined numerical model is proposed, considering coupled mechanical, hydration and thermal processes. It is revealed that the model could accurately predict the temperature and strain evolutions of CFST columns. Furthermore, experiments and numerical simulations illustrate that thermal cracking would likely be triggered in CFST components with diameter greater than 1.2 m.

FLOW AND HEAT-TRANSFER CHARACTERISTICS IN SMALL-DIAMETER TUBE BUNDLES WITH A STAGGERED LAYOUT: AN EXPERIMENTAL STUDY

While past research has primarily focused on heat transfer in larger diameter tubes, the capabilities of small-diameter tubes have often been estimated using correction factors. However, with the evolution of compact heat exchangers, conducting dedicated studies on small-diameter tube bundles has become increasingly crucial to achieve more precise conclusions. An experimental research on flow and heat-transfer characteristics of staggered tube bundles with different tube diameters (2, 3, and 5 mm) is conducted. In the experiment, the number of rows (4-12), the mass rate of the air (0.06-0.18 kg/s), and the transverse tube pitch (&lt;i&gt;S&lt;/i&gt;&lt;sub&gt;1&lt;/sub&gt;/&lt;i&gt;d&lt;/i&gt; &amp;#61; 2, &lt;i&gt;S&lt;/i&gt;&lt;sub&gt;1&lt;/sub&gt;/&lt;i&gt;d&lt;/i&gt; &amp;#61; 3) are variables to study the characteristics of the airside flow resistance and heat transfer. The three main conclusions of the experimental results are as follows: (1) Under the same conditions, the smaller tube diameter leads to the larger airside convective heat-transfer coefficient. Besides, the deviation between the Nusselt number of the experiment and the empirical correlation of &amp;Zcaron;ukauskas is in the range between -14 and -10&amp;#37;; (2) The effect of transverse distance on heat transfer is not obvious, but the convective heat-transfer coefficient increases significantly with the increase of row number; (3) The external pressure drop of the tube exhibits an exponential increase with the air-flow rate. Particularly in the experimental samples with smaller diameters, the outflow resistance of the tube is noticeably higher compared to other tubes. Finally, new empirical correlations of the airside convection heat transfer for the small-diameter staggered tube bundles are fitted according to the experimental data, and it is hoped to provide a reference for the more accurate design of tube-bundle heat exchangers.

The impact of deposits in cylindrical pipes on hydrodynamics and heat transfer

The paper deals with the problems of shell-and-tube heat exchangers operation taking into account the influence of scale and corrosion deposits on heat transfer efficiency. On the basis of numerical modeling performed in the ANSYS CFX program complex, research of various geometrical characteristics of heat exchangers, as well as deposit thicknesses on the heat transfer efficiency was carried out. The simulation results showed that the increase in fouling thickness worsens heat transfer in heat exchangers with large tube diameters, while in heat exchangers with small diameters the heat transfer fluid velocity increases, compensating for the additional thermal resistance. The influence of various parameters on the operation of heat exchanger equipment is evaluated and recommendations on optimization of its operation and frequency of cleaning are offered.

Breaking through the bending limit of Al-alloy tubes by cryogenic effect controlled mechanical properties and friction behaviours

Aluminium alloy (Al-alloy) tubes, especially large-diameter thin-walled tubes with a tough bending radius, have been widely utilised in different industrial clusters owing to their high strength-to-weight ratio and good corrosion resistance. However, achieving such extreme specifications is challenging because severe and nonuniform bending deformation may cause tension and compression instabilities, such as overthinning, cracking, and wrinkling. Considering possible improvements in mechanical properties and friction behaviours of Al-alloy at cryogenic temperature (CT), the cryogenic bending potential of the 6061-O tubes with an extreme ratio of D/t of 89 (diameter/wall thickness) was explored at different deformation temperatures, including room temperature (RT) 20 °C, −60 °C, −120 °C, and −180 °C. First, the cryogenic mechanical properties and friction behaviour of the tubes were characterised. It was found that the overall mechanical properties of the Al-alloy tube were improved because of sub-grain formation and a more uniform distribution of dislocations at CT. The coefficient of friction between the tube and tooling exhibited a varying degree of reduction owing to the sensitivity of the tubes and the lubricant to CT. Subsequently, an innovative experimental platform for cryogenic bending was designed, and a finite element model of cryogenic bending was established. Third, cryogenic tube bendability and mechanism were explored. It was found that 6061-O tube formability can be effectively improved by cryogenic bending; however, there is no monotonic relationship between the bendability improvement and temperature decrease. The temperature to obtain the best bendability is −60 °C, at which the average wrinkle height is decreased by 81.4 %, and the average wall thickness reduction rate is reduced by 23.8 %. The bending limit represented by the bending radius is reduced from a 3.0D bending radius at RT to 1.0D at −60 °C, which is realised by the different or even opposite effects of the mechanical properties of tubes and the friction coefficient between the multiple contact interfaces on wall thinning and wrinkling.

Influence of Anodizing Parameters on the Morphological Characteristics of TNTAs

TiO2 nanotubes arrays (TNTAs) were synthesized using the anodization method in ethylene glycol (EG)-based electrolyte with different percentages of ammonium fluoride (0.3, 0.4, and 0.5 wt.%) and water content (2.5, 5, and 7.5% vol%). All the samples were ultrasonically cleaned in acetone, ethanol, and deionized water, then dried in air and kept in an etching solution for a while before anodization. The two-step anodization was carried out, followed by thermal treatment at 450°C for the crystallization. The nanotube samples were characterized using FE-SEM analysis. The FE-SEM results showed that the largest tube diameter was 87.74±1.89 nm of the TNTAs prepared in the EG electrolyte with a composition of 7.5% water content and 0.5% ammonium fluoride. The longest tube length analyzed was around 5.3 µm of the TNTAs prepared in the ethylene glycol electrolyte with the composition of 2.5% water content and 0.4% ammonium fluoride percentage, exhibiting a highly ordered, compact honeycomb structure and thick single-walled structure.

Compression-shear fracture of nickel-based superalloy during rotary tube piercing

Large-diameter nickel-based superalloy seamless tubes are the key component of pipeline transmission system in nuclear power, thermal power and petroleum industries. The rotary tube piercing (RTP) process is suitable to prepare large-diameter seamless tubes. However, the high temperature dynamic compression-shear fracture, also known as separation layer defect (SLD), is inevitable in the RTP process of nickel-based superalloy. In the study, the SLD was systematically studied by the combination of simulation and experiment. Firstly, the isothermal compression-shear experiments were designed to study the fracture behaviors. The results reveal that the plasticity of Inconel 718 alloy decrease with the increase of temperature and strain rate within the range of temperature 1080-1160℃ and strain rate 5–40/s, and the shear angle has significant effects on the fracture behavior. Secondly, based on the isothermal compression-shear experiment results, the SLD was explored by RTP experiments. The results reveal that the compression-shear deformation extent has significant effects on the SLD, and the folding defect is generated before the SLD is observed. The fracture morphology further confirms that the SLD belongs to typical shear fracture, which is generated under specific strain and stress state. Finally, the formation mechanism of SLD is revealed by combining finite element simulation and experiment. It is found that the formation of SLD includes crack initiation and crack propagation. Crack initiation is related with the maximum shear strain and maximum shear stress, and the crack propagation is controlled by radial deformation gradient.

Structural performance of a novel combined nested bolted joint for aluminum alloy mega-latticed structures

A novel steel-aluminum joint system is first presented for aluminum alloy mega-latticed structures. This joint can be effectively applied to the connection of large-diameter tube members with complex spatial locations in space structures. The joint's finite element model is examined and validated, followed by a case study of one joint, including static analysis and an analysis of the bending moment-rotation curve. According to the moment-rotation curve, the joint is classified as a type of semi-rigid joint. Furthermore, the analysis considers key parameters that impact the joint's bending, axial, and torsional performance, such as the number of bolts per ring, the rings of bolts, and the thickness of the joint zone. Two simplified formulas for joint stiffness are proposed to evaluate the overall structural stability. Finally, a stability analysis of an aluminum alloy mega-latticed structure is conducted, incorporating this joint and the proposed simplified formulas. The ultimate load of the mega-latticed structure with the joints is found to be about 0.7 of that with ideal rigid joints with the same parameters. This paper presents a potential solution for appropriate connections in large-span aluminum alloy mega-lattice structures, thereby serving as a reference for the design of the joints in related space structures.

S-CO2 flow in vertical tubes of large-diameter: Experimental evaluation and numerical exploration for heat transfer deterioration and prevention

Heat transfer deterioration (HTD) problems can undermine the thermal safety of heating tubes for supercritical carbon dioxide (S-CO2) flows. Relevant experimental evidence is highly desired, but most cases were investigated for small tube diameters (below 10 mm) and under limited operation parameters, far from the industry-scale applications. In the present work, large tubes (24 mm) are investigated experimentally with pressures of 7.5–15 MPa, mass flow rates of 100–1200 kg·m−2·s−1 and heat fluxes of 30–350 kW·m−2. The seriousness of HTD in large tubes was experimentally confirmed, and the mechanism is explored via a carefully-designed comprehensive comparison between present numerical simulations and experimental tests. Detailed analysis of vapor-like film development inspires us to mitigate the problem using structured-inner-surface, from the viewpoint of “supercritical pseudo-boiling”. This inspiration is further evaluated numerically: five types of enhancement structures are proposed to interfere with the development of vapor-like film. It was found that the proposed methods can fully prevent HTD problems, and especially the conical strips can achieve a high heat transfer performance (with performance evaluation criteria PEC of 1.21–1.35) and are thus recommended for HTD prevention in vertical large-diameter tubes under near-critical conditions. Overall, the experimental tests and numerical explorations can deliver more evidence on the theory and applications of supercritical fluid flow and heat transfer.

Numerical study on the effect of co-current gas flow on the falling film flow characteristics outside the horizontal tube

Gas-liquid interactions are a ubiquitous feature of falling film exchangers in the nuclear industry. In the current research, a 2D model is established to explore the impact of co-current gas flow on the hydrodynamic characteristics of the falling film outside the horizontal pipes. This study examines different factors, including film flow rate, tube diameter, co-current gas flow velocity, transverse pitch ratio, distributor height, and inlet liquid temperature. The results revealed that the co-current gas flow significantly reduces the film thickness in the strong gas-liquid interaction zone and intensifies the fluctuating motion in the weak portion. Lead to the location of the minimum film thickness shifting upwards to around 90°, which highlights the need to monitor this region to prevent the occurrence of film rupture or dry spots that negatively impact heat transfer performance. When the gas flow velocity is constant, the lower liquid film flow rate, the larger tube diameter, and the distributor height enhance the impact of gas flow velocity on the falling film, resulting in reduced liquid film thickness. A film thickness correlation applicable to both with and without co-current gas flow is established, and 91% of 900 prediction data fell within ±15% of the numerical results.