Tube Section Research Articles

“Ion sputtering – thermal separation” technology for spent nuclear fuel processing

The purpose of this work is to develop a new technology for spent nuclear fuel (SNF) processing, aimed at effective solution of the problem – creation of a closed nuclear fuel cycle. We offer “dry” technology “Ion sputtering - thermal separation” (IS-TS) for a spent nuclear fuel processing with its separation into elemental components by differentiation them due to individual variations in the saturated vapor temperature. Separation is provided through SNF tablets sputtering-evaporation at the high-pressure microplasma discharge (pressure about 1 atm.) in an inert gas (e.g., argon) flow with the following separation into elemental components along the diffusion tube sections maintained at the specified temperature levels. According to IS-TS technology, at the current density of 5 A/cm2 and voltage of 600 V, mass processing rate of SNF is estimated 0,01 g/sec or ∼1 kg/day. Accounting of additional effect of thermal tablet evaporation further increase processing rate value. In this way, a single block of 100 discharge-diffusion tubes, operating in parallel, is estimated to recover 30 ton of SNF per year. The microplasma high-pressure discharge in an inert gas environment used in IS-TS technology is also applied for decontamination of irradiated reactor graphite and internal surfaces of metal structures of the primary circuit of NPU.

Study on the stability behavior of 7A04-T6 aluminum alloy square and rectangular hollow section columns under axial compression

To understand the stability behavior of 7A04-T6 ultra-hard aluminum alloy rectangular hollow section tubes under axial compression, 39 specimens with square and rectangular hollow sections (SHSs and RHSs, respectively) and eight to ten relative slenderness ratios were experimentally analyzed. The initial geometric imperfections were measured prior to compression tests to investigate their impact on stability capacities. The experimental results were then used to validate a finite element (FE) model, which was then used to determine the influence of relative slenderness ratio, initial imperfections, sectional height-to-width ratio, and material properties. The test and FE results were used to assess six current design standards and methods including the Chinese National Standard (GB 50429-2007), European code (EN 1999-1-1:2007), American Aluminum Design Manual (AA-2015), the Australian/New Zealand Standard (AS/NZS-1997), the Continuous Strength Method (CSM), and the Direct Strength Method (DSM). A modified design method based on AA-2015 was proposed for predicting the buckling resistance of 7A04-T6 aluminum alloy rectangular hollow tubes under axial compression and it proved to predict the results well.

Active control behavior on the flow pattern in a circular duct

The current analysis aims to review the effectiveness of the flow regulations at Mach 1.87, a considerably large Mach number. The duct radius is11 mm, and the diameter ratio concerning the exit of the nozzle is 2.2. Tests were done at different expansion levels for eight different duct sizes. Here we are pondering in a situation where there is a considerable variation of pressure is noticed. The flow control was located at a PCD of 13 mm from the axis. The control jets of 0.001 m diameter producing a Mach unity jet, used as energetic flow control. For shorter tube sections at smaller NPRs, the pressure undertakes a minimal value. Soon After, with an increase of the tube size and expansion levels, a continuing fall in pressure owing to the decline in the level of adverse pressure and shock waves intensity. Flow fluctuations are witnessed for various duct sizes. The duct size represents a vital part while ascertaining the flow advancement in the duct. Relatively high pressure is seen for duct length L = 132 mm and L = 220 mm for nozzle pressure ratios three and five. The pressure becomes modest due to the effect of duct size. For NPR = 7, an increase in pressure is restricted by the separated zone, and atmospheric restrictions are almost accomplished. For the 10D duct, the realization of the ambient condition is additionally enhanced near the upstream.

Thermo-hydraulic performance analysis of converging-diverging heat exchanger with inclined fins using computational fluid dynamics

The combination of geometric parameters for improving the overall performance of heat exchangers is a promising approach that has been widely investigated to date. The thermo-hydraulic performance of a converging-diverging shell and tube heat exchanger using hybrid geometrical parameters is numerically evaluated in this study. Although the noticeable impacts of converging-diverging channels in heat transfer improvement have been confirmed in the literature, the converging-diverging shell and tube heat exchanger with inclined fins is a topic that researchers have not looked at before. The turbulent RNG k-ε model is considered for the counter-current flow in the shell and tube sections using computational fluid dynamics. Different geometries, including four, seven, and ten convergences along the shell, number of the fins (n = 0, 2, 4, 8), and the fins inclination angles (a = 45o, 90o) are analyzed comprehensively in twenty-eight cases. The streamlines demonstrate a zigzag flow pattern in the converging-diverging shell which provides better mixing. The results based on the Colburn factor and friction factor indicate that the converging-diverging geometries present a higher heat transfer rate between 50.67%-60.86% with a 73.45%- 86.90% pressure drop penalty compared to the cylindrical heat exchangers. Also, the inclined fins enhance the heat transfer up to 21.65% compared to the vertical fins. Finally, the optimum configuration of the heat exchanger is introduced, considering the area goodness factor.

Preparation of crack-free, non-notched, flattened bamboo board and its physical and mechanical properties

Bamboo flattening technology can increase the utilization of bamboo, flattening half or third bamboo tube sections into flattened bamboo strips through steam softening, roller flattening and drying. Compared with earlier notched flattening technology, newer non-notched flattening technology does not incise or damage the culm inner surface. In this paper, we introduce a non-notched flattening method and assess the macro-and micro-mechanical properties of the flattened bamboo. Results showed that the parenchyma cells shrank and distorted and the hygroscopicity of bamboo decreased and the hygroscopicity of bamboo decreased due to the decomposition of hemicelluloses. The modulus of elasticity (MOE) and hardness were increased as a function of treatment temperature and time. The MOE increased by 25% and the hardness significantly increased by 34% after the flattening process due to the tissue densification and increased crystallinity index. The improved micromechanical properties of cell walls and increased density positively contributed to the macro-mechanical properties.

Validation of FE modeling of cold-formed tube lightweight concrete composite system

Experimental testing of composite beams takes a long time, and usually complicated, and necessitates massive testing facilities. After validation, finite element modeling can be utilized for understanding the fundamental behavior of composite beams. Unfortunately, no available experimental data has been found regarding the composite behavior of a cold-formed steel tube section and a lightweight concrete slab with a metal deck. Therefore, this study aims to validate the FE modeling for different components of the composite system by contrasting numerical results with the corresponding published experimental data for the specific component. Firstly, the FE modeling for a separate cold-formed tube beam has been validated by contrasting it to the experimental data with emphasis on the imperfection modeling and post-buckling behavior. Then an experimental data for lightweight concrete beam has been adopted to validate the FE modeling for lightweight concrete. Finally, the FE modeling for the hot-rolled composite beam has been conducted and compared with the experiments for the validation of the composite action as well as the contact between the beam and the supported slab deck.

Axial-Load Resistance of a Novel UHPFRC Grouted SHS Tube-Sleeve Connection: Experimental, Numerical, and Theoretical Approaches

Experimental, numerical, and theoretical analyses were conducted of the axial load resistance of a novel ultrahigh-performance fiber-reinforced concrete (UHPFRC) grouted square hollow section (SHS) tube sleeve connection. The experimental study tested 10 full-scale specimens with varying shear key spacings, grout thicknesses, grout lengths, and volume proportions of steel fiber in the UHPFRC. Two types of failure modes were observed: (1) for the connection with high strength of the grouted part, the failure mode was fracture of the inner tube; and (2) for the connection with lower strength of the grouted part, the failure mode was grout shear crushing with significant bond-slip between grout and steel tube. To understand further the load transfer mechanism of the connection, an advanced three-dimensional (3D) nonlinear finite-element (FE) model was built to simulate the axial load–displacement behavior, state of stress and strain, and crack development of the grout. Based on the test and FE results, a new theoretical model was derived to predict the axial-load resistance of the connection. The proposed model considers the effect of section shape and material parameters, and is applicable to UHPFRC grouted SHS tube sleeve connection with different corner radii. Validation versus the test results showed that the new model can provide reasonably effective and accurate predictions of the axial-load resistance of the novel grouted sleeve connection subjected to tension.

Effects of Tube Structure on the Aerodynamic Characteristics of Evacuated Tube Transport System

The tube structure is an important guarantee for the dynamic stability of the high temperature superconducting maglev-evacuated tube transport (HTS Maglev-ETT) system, it is necessary to conduct relevant research on it. Based on simulation calculations with the FLUENT software, this paper studied the influences of different tube section forms on the aerodynamic drag of maglev train in tube, as well as the pressure distribution in the tube system. In addition, the effects of the setting of cross aisle on the aerodynamic drag of maglev train and pressure fluctuation of flow field in tube were also studied. It was found that the difference in the section forms of tube has little effect on the aerodynamic drag of maglev train and pressure distribution of the tube system under low pressure; the setting of cross aisle can be helpful to reduce the aerodynamic drag of maglev train and the pressure fluctuation around the train to a certain extent. Therefore, the design of cross aisle is recommended for the HTS Maglev-ETT system.

Flexural Strength of Internally Stiffened Tubular Steel Beam Filled with Recycled Concrete Materials.

The flexural strength of Slender steel tube sections is known to achieve significant improvements upon being filled with concrete material; however, this section is more likely to fail due to buckling under compression stresses. This study investigates the flexural behavior of a Slender steel tube beam that was produced by connecting two pieces of C-sections and was filled with recycled-aggregate concrete materials (CFST beam). The C-section’s lips behaved as internal stiffeners for the CFST beam’s cross-section. A static flexural test was conducted on five large scale specimens, including one specimen that was tested without concrete material (hollow specimen). The ABAQUS software was also employed for the simulation and non-linear analysis of an additional 20 CFST models in order to further investigate the effects of varied parameters that were not tested experimentally. The numerical model was able to adequately verify the flexural behavior and failure mode of the corresponding tested specimen, with an overestimation of the flexural strength capacity of about 3.1%. Generally, the study confirmed the validity of using the tubular C-sections in the CFST beam concept, and their lips (internal stiffeners) led to significant improvements in the flexural strength, stiffness, and energy absorption index. Moreover, a new analytical method was developed to specifically predict the bending (flexural) strength capacity of the internally stiffened CFST beams with steel stiffeners, which was well-aligned with the results derived from the current investigation and with those obtained by others.

High-sensitive fiber-optic pressure sensor based on Fabry-Perot interferometer filled with ultraviolet glue film and Vernier effect

A high sensitivity fiber-optic pressure sensor based on Fabry-Perot interferometer filled with ultraviolet (UV) glue film and Vernier effect was proposed and demonstrated. The sensor is composed of a sensing Fabry-Perot (FP) cavity and a reference FP cavity in parallel. The sensing cavity is fabricated by splicing a section of silica tube (ST) to the lead-in single-mode fiber (SMF), and filling a thin layer of UV glue at the end-face of the ST. The reference cavity is made by sandwiching a section of ST between two SMF. The parallel cavities generate the Vernier effect due to a similar free spectrum range, which significantly improves the sensitivity of the sensor. The proposed sensor with good repeatability and reliability was used to monitor the change of air pressure, and provided a high sensitivity of −38.3 nm/MPa. The sensor exhibited the potential applications in the fields of aerospace industry, biological diagnostics and environmental monitoring.

A High-Sensitive Fiber-Optic Fabry-Perot Sensor With Parallel Polymer-Air Cavities Based on Vernier Effect for Simultaneous Measurement of Pressure and Temperature

A novel high-sensitive fiber-optic Fabry-Perot sensor with parallel polymer-air cavities based on Vernier effect was proposed and demonstrated for simultaneous measurement of pressure and temperature. The sensor is composed of two parallel Fabry-Perot cavities both are fabricated by splicing a section of silica tube to the single-mode fiber. One cavity is filled with polydimethylsiloxane, and the other cavity is filled with a thin layer of ultraviolet glue at the end-face of silica tube, ensuring that the free spectrum ranges of two Fabry-Perot cavities are similar and generate the Vernier effect. The Fabry-Perot interferometer filled with polydimethylsiloxane was found to be sensitive to pressure as well as temperature, whereas the Fabry-Perot interferometer filled with a thin layer of ultraviolet glue was sensitive to pressure only. Owing to the different features of two Fabry-Perot interferometers, the sensor achieved simultaneous measurement of pressure and temperature. Combined with Vernier effect, the sensor provided a pressure sensitivity of −36.93 nm/MPa and a temperature sensitivity of 10.29 nm/°C, respectively. The sensor has exhibited potential applications in fields of medical diagnostics, environmental monitoring, and biological sensing.

Experimental investigation of corroded CHS tubes in the artificial marine environment subjected to impact loading

Tubular structure is the main structure form of offshore platform. With the increase of service life, the corrosion of steel tube in the platform, especially in the spray splash area, is increasing day by day. At the same time, the spray splash area is also the part of offshore platform which is threatened by the impact of external loads. In this paper, the behavior of corroded circular hollow section (CHS) tubes under impact loading was studied. (1) A kind of test instrument to simulate marine environment was developed, which realizes the automatic operation of tide, wave and temperature. The scheme of electric accelerated corrosion test in artificial marine environment was designed. The corrosion tests of six CHS tubes at different times were carried out, and the corrosion depths of CHS tubes were measured by high-precision 3D scanner. The results show that the varying trend of corrosion area morphology and corrosion rate is similar to that of natural corrosion, and the artificial corrosion test has achieved good results. (2) The impact tests of corroded CHS tubes were carried out. The failure modes, impact force versus time history curves, displacement versus time history curves and strain versus time history curves of all specimens were obtained. The results show that the limited local corrosion has little effect on the overall failure modes of test specimens. The corrosion defects resulted in the pre-yielding of upper surface of CHS tubes and weakened the elastic recovery ability. The serious stress concentration phenomenon in the corrosion area can be inferred from the analysis of the strain versus time history curves.

Analysis and Design of Stadium with Truss System and Shell Roof Subjected to Wind and Seismic Loading

In this paper Analysis and Design of different Structural elements of the football stadium are presented, with particular emphasis on the Combination of Steel Truss without and with Shell roof cover and its interȧction with the underlying reinforced concrete structures. The Football stadium considered for the study is of rectangular plan, with 85 m width and 140 m length and height of 19.5 m. The plan of Football Stadium is generated in AutoCAD 2016 software. The Stadium structure is composed of special moment – resisting framed. Wind velocity is taken as 39 mph and Seismic zone IV in this study. The proposed stadium is analysed using Equivȧlent static and dynamic ȧpproach by Reṣponse ṣpectrum ȧnd Time Hiṣtory ȧnȧlysis. In anȧlysing the ṣtructure, 21 load combinations are used. The grandstand ṣtructure is made of reinforced concrete and the roof is of ṣtructural steel using Pipe and Tube sections. Deȧd loȧdṣ, live loȧdṣ, wind ȧnd ṣeismic loȧdingṣ data are considered bȧsed on IS-875 (PART 1-3) 1987 ȧnd IS:1893 (Part 1):2016. IS456:2000 and SP16:1987 code is used for Design of R.C.C components such as Beȧm, Column, Seating Platform, Footing and IS 800:2007 code is used for Design of End Beȧring Plate connection with Truss member. Analysiṣ of truss and other elements is carried out with software program of Staad. Pro V8i SS6 and also the designs are carried out as per provisions of relevant Indian standards. On introduction of Shell-like roof for Open Stadium which is used not only to protect the Game from Glare of Sunshine and Rain but also appears unique and attractive. From the obtained results it is observed that the displacement due to Wind action in both X and Z direction reduces significantly by the introduction of Shell roof. Also, due to RSA and THA there is reduction in the displacement on introduction of Shell-like roof to an Open Stadium.

Thermo-fluidic characteristics and performance in a distribute heating bubble pump generator

In some thermally driven two-phase natural circulation systems, bubble pumps serve as the key driving powers for the cycles. Recently a type of distribute heating bubble pump generator (BPG) is gradually receiving attention due to its compact structure and great potentials to utilize solar energy and low-grade waste heat recovery. The BPG provides a variety of promising features (e.g., passive heat transfer, enhanced reliability), which can benefit the advancing of heat transfer technology. For the primary study, we performed an experiment in a distributed heating BPG. Through utilizing multiple lift tubes and partial visualization configurations, it provides accesses to observe the flow pattern transition and monitor the flow instability, and thus to explore some of the underlying mechanisms affecting BPG performance.Results showed that heat input and immersion height were crucial parameters to enable the operation of distribute heating BPG. With low heat input or high inlet water subcooling level, the flow within the pump was unstable with intermittent flow interruptions. As the heat input increased, the fluid flow became more stable, the vapor generation increased linearly, while the lifted liquid flow rate initially increased then decreased. Correspondingly, the flow pattern at the outlet section of lift tubes gradually changed from slug flow to churn flow, and then to annular flow. The higher of the immersion was, the higher heat input was needed for the flow pattern transition. It was in the churn flow regime at the outlet of lift tubes for the BPG to lift a maximum liquid. At lower immersion level, liquid reflux in the lift tubes was obvious and affected the flow stability as well as the lifting performance. At higher immersion level, the fluid flow was more stable and faster, which lifted more liquid while generated less vapor depending on the inlet subcooling. In general, the BPG showed better performance (both the lifted liquid and vapor generation increased) at smaller inlet subcooling level or lower system pressure. This study highlights the flow pattern evolution and flow stability, which is helpful to the reliable design and effective operation of the distributed heating BPG.

Effect of single tube sections on the structural safety of Chinese solar greenhouse skeletons

In recent years, the use of single-tube skeletons for the construction of Chinese solar greenhouses has increased. As a consequence, during the selection of the construction materials, the safety of these structures has become an important issue. The single tube section has various forms, but there is no scientific theory to guide the selection process. To the best of our knowledge, the scientific analysis of the impact of single pipe cross section on the safety of greenhouse skeleton has not been addressed so far. In this context, the finite element analysis software was used to calculate and analyze the stress elements, displacement of round tube, Ω tube, elliptic tube and square tube under the same load conditions. We used the Chinese Standard values as a reference and analyzed structural features of different sizes and thicknesses of the greenhouse steel skeleton sections under non-uniform snow load. The results showed that, under the same load condition, the maximum stress in the four skeleton materials was all located at the connection of the transverse tension bar and the front roof. In addition, under same load condition, the greenhouse skeleton with elliptic tube presented the smallest cross-sectional displacement between the different materials tested. The effect of increasing the size of the greenhouse frame was better than that of increasing the greenhouse material thickness. All this work will provide theoretical guidance to the material selection of this structure.

Experimental study on the compression mechanical behaviour of steel pipes with mechanically induced pitting corrosion

Pitting damage severely degrades the mechanical properties of the main force-bearing member of a circular tube; it can also change its failure mode. Offshore high-strength seamless steel pipes with steel grade X52Q certified by ABS were selected for a pressure test and research. The constraint conditions of one hinged end and one fixed end were adopted to investigate the effect of the bending moment of the nodes so that any section of the circular tube can be subjected to the superposition of axial force and bending moment. Pitting craters were generated using mechanical processing methods; the effect of pitting parameters such as diameter, depth, and distribution on the mechanical properties and failure modes of circular pipes was explored. Pitting corrosion damage caused local stress concentration and the local cross-section weakening of the tube. In addition to the decline of the bearing capacity under the action of axial compression load, the failure mode of the pitting corrosion damage tube also showed differences. Increased local damage caused by the increase in the diameter of the pitting corrosion was likely to cause plastic hinges on the pits of the tube, and this changed stress conditions, failure modes, and failure locations of the components. An increase in the depth of the pitting craters resulted in a significant drop in the overall load-bearing capacity caused by local buckling. The location of pitting corrosion had negligible effect on the mechanical performance of the tube; the end distribution was more unfavourable than the centre distribution. The stress–strain distribution characteristics of the pitting area of the specimen were considerably different, and the stress concentration on the inner side of the pitting corrosion were serious and uneven. The results of the experimental analysis and several numerical examples indicated that pitting corrosion causes the pressure-bearing circular pipes with lower strength buckling to more likely suffer from an instability failure.

Analytical and numerical study for oscillatory flow of viscoelastic fluid in a tube with isosceles right triangular cross section

Abstract A theoretical investigation is carried out to analyze the oscillatory flow of second-grade fluid under the periodic pressure gradient in a long tube of isosceles right triangular cross section in the present study. The analytical expressions for the velocity profile and phase difference are obtained. The numerical solutions are calculated by using the finite difference method with Crank–Nicolson (C–N) scheme. In comparison with the Newtonian fluid (λ = 0), the effects of retardation time, Deborah number and Womersley number on the velocity profile and phase difference are discussed numerically and graphically. For smaller Womersley number, the behavior of second-grade fluid is dominated by viscosity. For larger Womersley number α = 20, the flow becomes more difficult to be generated under periodic pressure gradient with increasing retardation time. Furthermore, the analytical expressions of the mean velocity amplitude and phase difference are given explicitly for discussing.

Prediction of axial compression behavior of rectangular RCFST columns with confining ties

A numerical investigation has been conducted to predict the peak axial strength, post-peak behavior and confined stress-strain characteristics of reinforced concrete-filled steel tubular (RCFST) columns of rectangular cross-sections under axial compression loading. Finite element analyses are carried out using a computer software ABAQUS to evaluate the axial behavior of RCFST columns. A parametric study has been conducted on rectangular RCFST columns for width-to-depth (aspect) ratios varying between 1 and 2, tube slenderness ratio ranging between 10 and 266), percentage of longitudinal reinforcement varying between 0.87 and 6.21%, five different arrangements of internal ties and volumetric ratios of ties ranging from 0.13 to 3.19%. It is observed that the RCFST columns, even with a slender tube section, showed a significant increase in strength and ductility when effectively confined with internal transverse ties. The results obtained from the numerical study are compared with the analytical confinement models and the design equations of building codes. Based on this study, suitable modifications are proposed for existing design equations to consider the effect of confining reinforcements.

Slender FRP-confined steel-reinforced RAC columns under eccentric compression: Buckling behavior and design calculation models

To extend the structural use of recycled aggregate concrete (RAC) in civil construction, this study has been concerned with the buckling behavior of FRP-confined steel-reinforced concrete (FCSRC) columns under eccentric compression, having RAC infilled between FRP tube and steel section to improve the mechanical and durability performance of RAC. The effects of FRP confinement level, load eccentricity, column height, and replacement ratio of recycled coarse aggregate (RCA) were investigated. The test results revealed that the replacement ratio of RCA had little influence on the buckling behavior of slender FCSRC columns except for the ultimate load-carrying capacity which was mainly governed by the load eccentricity. Besides, a new relative slenderness ratio was recommended for such columns to define their slenderness, and two design calculation models were proposed to determine the secant flexural stiffness and ultimate load-carrying capacity, respectively. A comparison between test and predicted results indicated that design calculation models are applicable to evaluate the buckling behavior of RAC characterized FCSRC columns under eccentric loads, including lateral deflection, second-order bending moment, and the ultimate load-carrying capacity, which facilitates the structural use of RAC in FCSRC hybrid columns.

Experimental Investigation of Heat Transfer of Nanofluid in Elliptical and Circular Tubes

The paper presents experimental comparison of forced convection for steady state turbulent flow of nanofluid (Al2O3-distilled water) inside circular and elliptical (aspect ratio of 0.75) cross section tubes of identical circumference and tube surface area. Convection coefficient, pressure change, and fiction factor were compared at different Reynolds number (3,000-9,230) with different nanoparticles volume concentration (0.5%, 1.0%, and 1.5%). The results showed that Nusselt number increases with increasing Reynolds number and nanoparticle volume concentration. The pressure drops and friction factor of nanofluid are higher than the distilled water and are increasing as the volume concentration increases. Furthermore, the elliptical tube provided small increase in Nusselt number compared to that of circular cross sectional tube. However, the friction factor in the elliptical tube was slightly higher.