Small Diameter Tubes Research Articles

Effect of heat treatments on the structure and properties of a small-diameter thin-walled tube of a medical nickel titanium alloy

The present study examines the effect of annealing at temperatures of 300-500°C on the structure and properties of a thin-walled nitinol tube of composition Ti49.1Ni50.9 used for the manufacture of intravascular stents. Annealing temperature dependences are obtained for the martensitic transformation temperatures, the size of the structural elements of the grain-subgrain structure, phase composition, pseudo-yield stress, and ultimate strength. The effect of the Ti3Ni4 particle precipitation in aging during annealing at different temperatures on the obtained dependences is analyzed.

Longitudinal Guided Wave Inspection of Small-Diameter Elbowed Steel Tubes with a Novel Squirrel-Cage Magnetostrictive Sensor

In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.

Prediction of Heat Transfer Coefficient and Pressure Drop in Wire Heat Exchanger Working with R-134a and R-600a

An experimental and theoretical works were carried out to model the wire condenser in the domestic refrigerator by calculating the heat transfer coefficient and pressure drop and finding the optimum performance. The two methods were used for calculation, zone method, and an integral method. The work was conducted by using two wire condensers with equal length but different in tube diameters, two refrigerants, R-134a and R-600a, and two different compressors matching the refrigerant type. In the experimental work, the optimum charge was found for the refrigerator according to ASHRAE recommendation. Then, the tests were done at 32˚C ambient temperature in a closed room with dimension (2m*2m*3m). The results showed that the average heat transfer coefficient for the R-600a was higher than the R-134a, so the length of the wire tube was longer with R-134a than R-600a. The pressure drop for the smaller tube diameter was higher than the other tube. The second law thermodynamic efficiency was higher for R-600a, which reached 41%. The entropy generation minimization analysis showed that the R-600a refrigerant type and smaller tube diameter are approached the optimum point.

Ultrasonic multi-view total focusing method for weld defect detection on small-diameter austenitic stainless steel tubes

Austenitic stainless steels are widely used in the key components of major equipment and the welds can be the weakest parts of equipment made with these materials. Ultrasonic waves propagate in austenitic stainless steel welds with multiple paths and modes. This study employed a multi-view total focusing method using an ultrasonic phased array for defect detection in the welds of small-diameter austenitic stainless steel pipes. The detection capability of four different direct wave modes and eight different half-skip wave modes for typical defects were compared and analysed through numerical simulation. A fusion imaging method was developed using the preferred direct and half-skip wave modes. The process was further verified with a weld defect detection experiment carried out on small-diameter austenitic stainless steel pipes. The results show that the multi-view total focusing method can efficiently detect the defects in the welds of small-diameter tubes. Compared with the single-mode imaging method, the fusion total focusing imaging approach can not only improve the signal-to-noise ratio but can also reduce the number of image artefacts.

Motion of a single vapor Taylor bubble in the vertical tube of small diameter

An experimental study of the dynamics of the Taylor vapor bubble in water and in an aqueous solution of lithium bromide at vapor saturation pressure was carried out. The Taylor bubble was formed after boiling-up of the overheated degassed liquid in 16 mm diameter tube. The study has shown that the dynamics of the vapor cavity during boiling up leads to a qualitative difference from the dynamics of the vapor bubble in a large volume. There are also qualitative differences in the nature of motion of the vapor bubble and that of the gas bubble. This is due to the fact that the mass of the gas bubble and the temperature of the liquid do not change during the rise near the bubble, whereas the mass of the vapor bubble and the temperature of the vapor in the bubble and the liquid near the bubble can vary significantly due to evaporation of the liquid and steam condensation. This is due to the change of bubble height and level of fluid in the tube. The liquid level in the tube depends on the height of the bubbles, but the height of the liquid level in the tube depends on the volume of the bubbles.

Design, synthesis, characterization, and cytotoxicity of PCL/PLGA scaffolds through plasma treatment in the presence of pyrrole for possible use in urethral tissue engineering.

Electrospinning has proven to be a suitable technique for the production of small diameter tubes, with diverse applications, in the field of tissue engineering. In this work, tubular scaffolds were prepared by electrospinning a polycaprolactone/polylactic-co-glycolic acid (PLGA) blend and then treated with polypyrrole plasma for a possible application with urethral tissue. Scanning electron microscopy micrographs showed that for 10% and 20% of the PLGA in the blend, the microfibers, of varying diameters, were free of defects. The elastic modulus of the tubular scaffolds was highest (19 MPa) at 30% of PLGA, while the strain to break was maximum at 10–20% PLGA. However, at 30% of PLGA, within the polycaprolactone, the mechanical synergy (strain at break) was lost. Epithelial cells and smooth muscle cells’ viability on 80/20 blends was high. When this scaffold was treated for 15 min with polypyrrol plasma, an improvement in cell viability was observed, with few polypyrrol particles being deposited and little scaffold degradation. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed the presence of NH, C–N, and C≡N groups as the chemical groups responsible of this behavior. Therefore, these scaffolds with the polypyrrole surface treatment can be used in the urethra tissue engineering.

Compressive behavior of small-diameter concrete-filled fiber-reinforced polymer tubes as internal reinforcements

Concrete infilled in a small-diameter fiber-reinforced polymer tube is strongly confined, thus having a high compressive strength and excellent deformability. Such a feature is exploited in the development of two types of high-performance hybrid members at Guangdong University of Technology, China, by incorporating small-diameter (30 to 60 mm) concrete-filled fiber-reinforced polymer tubes as internal reinforcements. Understanding the compressive behavior of small-diameter concrete-filled fiber-reinforced polymer tubes is essential to understanding the behavior of the proposed hybrid members and the development of their design approaches. This article therefore presents a systematic study on the axial compressive behavior of small-diameter concrete-filled fiber-reinforced polymer tubes with the test parameters being the thickness, diameter, and fiber type of fiber-reinforced polymer tubes and concrete strength. The test results show that the tested small-diameter concrete-filled fiber-reinforced polymer tubes have a compressive strength and an ultimate axial strain of up to 267 MPa and 10.3%, which are, respectively, about 6 and 34 times that of the corresponding unconfined specimens, demonstrating the great potential of small-diameter concrete-filled fiber-reinforced polymer tubes as internal reinforcements for use in high-performance hybrid members. The applicability of three widely accepted stress–strain models developed based on test results of fiber-reinforced polymer-confined concrete cylinders with a diameter of 150 mm or above is also examined. It is shown that the three models tend to predict a steeper second portion of stress–strain responses than the test results, revealing the need of a tailored stress–strain model for small-diameter concrete-filled fiber-reinforced polymer tubes.

Experimental study of detonation limits in methane-oxygen mixtures: Determining tube scale and initial pressure effects

In this paper, detonation limits in stoichiometric methane-oxygen mixtures with varying tube inner diameter and initial mixture pressure were investigated. Detonations in tubes with different inner diameter (D = 36 mm, 25 mm, 20 mm and 13 mm) and low initial pressure from 3.5 to 18 kPa were studied. Smoked foils were applied to observe the evolution of the detonation cellular structure for various initial conditions. An alternate length scale at the limits is examined, Ldcs, which is the maximum length from the beginning of the test section after which cellular patterns can no longer be observed. Simultaneous local velocity measurements were obtained by photodiodes to complement the Ldcs results. The study also aims to reveal relation between the near-limit detonation dynamics, the tube geometry, and the thermodynamic properties of the mixture. Past the failure limit, Ldcs decreases with decreasing initial mixture pressure for a given tube diameter, and Ldcs decreases faster in a smaller diameter tube. In the D = 13 mm tube, galloping detonation mode is observed, and the length of the galloping cycle is reduced with an increase in initial pressure. To further characterize the onset of detonation limits, a scaling analysis of Ldcs with tube inner diameter (D) and detonation cell size (λ) was performed. The experimental results show that the decrease of Ldcs/D and Ldcs/λ are more abrupt in smaller diameter tubes with decreasing initial pressure. At low initial pressure, the boundary layer displacement thickness growth is significant in the flow structure. Since the distribution of global curvature over the whole detonation front is faster in smaller tube, it thus leads to a more abrupt decrease sensitive to initial pressure. For increasing pressure closer to the critical failure limit, the boundary layer displacement thickness is becoming less comparable to the tube diameter. The failure mechanism appears to be more dominant by the rate of transverse waves attenuation or cell disappearance. Lastly, by comparing the detonation cell size and the tube scale at the critical limits condition in different tubes, λ = π⋅D is shown to be an appropriate limit criterion of detonation propagation in agreement previous studies.

Design, construction and test of small-diameter Muon Drift Tube chambers (sMDT) for the Phase-1 upgrade of the ATLAS muon spectrometer

The ATLAS muon spectrometer consists of an efficient muon trigger system and precision muon tracking chambers providing high momentum resolution up to the TeV scale. Yet, in the regions between the inner barrel and endcap of the muon spectrometer the trigger selectivity is limited. Furthermore, at the future High-Luminosity LHC the efficiency of the resistive plate trigger chambers (RPCs) will decrease due to ageing effects. Therefore, additional RPCs will be installed at the ends of the inner barrel layer of the muon spectrometer in the current long shutdown for the Phase-1 upgrade of the LHC in 2019 and 2020. In order to free space for them, the current Muon Drift Tube (MDT) chambers will be replaced by small-diameter Muon Drift Tube (sMDT) chambers with 15 instead of 30 mm tube diameter, which will be integrated with thin-gap RPCs. Due to their higher background rate capability, the new sMDT chambers are also suitable precision muon tracking detectors at future hadron colliders. An overview of the design and production of the new ATLAS sMDT chambers, their performance and their mechanical integration with the RPCs is given. The construction of these new chambers also serves as a pilot project for the replacement of half of the barrel inner layer in the Phase-2 upgrade of the ATLAS detector.

In-orbit micro-propulsion demonstrator for PICO-satellite applications

Delft University of Technology is currently developing the pico-satellite platform Delfi-PQ, based on the PocketQube standard, in pursuit of a new generation of satellites with lower cost, flexibility and short development time. A technology demonstration payload expected to fly in one of the first Delfi-PQ satellites is a dual thruster micro-propulsion system based on the use of water as propellant. Two different micro-resistojet concepts will be demonstrated in the same satellite flight: one based on vaporization, heating and expansion in a nozzle of pressurized liquid water (Vaporizing Liquid Micro-resistojet); the other based on heating and acceleration in slots with simple geometry of molecules of vapour under transitional or free molecular flow regime (Low Pressure Micro-resistojet).The demonstrator is based on a common propellant storage for the two micro-propulsion concepts, based on the use of the capillarity properties of water in a small diameter tube connected to the two separate MEMS thruster chips with their own dedicated valves. This paper describes the requirements and design of the complete micro-propulsion demonstrator as well as its expected operational envelope for in-orbit functional testing, based on the currently validated performance characteristics of the two thrusters.

Void fraction characteristics of adiabatic one-component vertically upward two-phase flows in circular and non-circular small diameter tubes.

Evaporating and condensing heat transfer and pressure loss characteristics strongly depend on interfacial structure of gas-liquid two-phase flows. Cross-sectional average void fraction is important parameter on the one-dimensional analysis. Recently, since channel diameter becomes smaller, the effect of surface tension on the flow behaviors would become stronger. This study deals with void fraction characteristics of adiabatic two-phase flows using FC-72 as the working fluid. Crosssectional average void fraction was measured by capacitance sensor. Circular, square and triangular tubes with the hydraulic diameter of 2 mm were used. Vertically upward flow was selected to evaluate for axially symmetric phase distribution. From the results, it was confirmed that for the square and triangular tube, void fraction became lower than the circular tube because liquid was accumulated in the corner by surface tension. Although the lower void fraction leads to larger slip velocity, the gas-liquid interface of liquid film became smoother.

Sodium receiver designs for integration with high temperature power cycles

A variety of tube materials and geometries are considered in an analysis that identifies suitable sodium receiver designs for integration with next-generation thermodynamic power cycles. Sodium is capable of delivering outlet temperatures of >750∘C, however the net power output diminishes with rising temperatures due to tube material limitations on allowable flux density and increasing heat losses. Small tube diameters facilitate large thermal efficiencies and heat fluxes for all materials, however a large pressure drop penalty can somewhat mitigate these advantages. Traditional heat exchanger alloys perform quite poorly in comparison to Inconel 617 and Haynes 230, with allowable heat flux decreasing significantly as temperatures are increased beyond 600∘C. Multi-pass concepts offer greater control of flow-path exposure to the heat flux boundary condition than straightforward single-pass designs. A triple-panel design with small diameter Inconel 617 tubes balances thermal, hydraulic, and mechanical performance most effectively across all temperatures. For all candidate materials, sodium can augment power plant efficiency when integrated with a high temperature cycle (>600∘C). A combined receiver and power cycle efficiency percentage point improvement of 1.5% is possible using Ni-based superalloys at ∼650−700∘C compared to a baseline outlet temperature of 550∘C, resulting in a solar-to-electric power output increase of over 4%.

Performance Assessment and Improvement of Central Receivers Used for Solar Thermal Plants

In this work, the energy status and supply plans of Saudi Arabia are discussed with a focus on concentrated solar power (CSP) technologies. Subsequently, optimal designs for a 20 MWe solar power plant external receiver, combined with a 15 h thermal energy storage unit, operating under the weather conditions of Neom City, located in northeast Saudi Arabia, is proposed. The effects of receiver tube diameters, tube thicknesses, tube thermal conductivity and receiver’s performance are studied in detail and compared to those used in a well know operational CSP plant. Results show that a smaller tube diameter and thickness give higher receiver thermal efficiency but increase the annual cost of pumping energy. However, that increment in cost is negligible compared to the total energy gained. Furthermore, the aspect ratio is investigated and it was found that a higher aspect ratio gives a higher thermal efficiency. The thermal efficiency of the optimised receiver was increased by about 1% more than the reference plant. In addition, the new design decreases the total estimated cost of tube material by approximately 43%. It is anticipated that the reported results could pave the path for more efficient solar thermal power plants.

Hydrodynamic performance improvement on small horizontal axis current turbine blade using different tube slots configurations

Vortex generators are used extensively as a passive flow control devices to delay or remove the boundary layer separation, which affects the hydrodynamic performance of the hydrofoil. In this paper, a new approach is introduced to overcome the boundary layer separation on the NACA S1210 hydrofoil. The outcome of tube slots combination in the S1210 hydrofoil on the boundary layer separation are numerically investigated. The performance is compared with respect to the force coefficients and glide ratio. The effects of tube slot inlet positions with different diameters on S1210 hydrofoil are presented here. The results show that the smaller diameter tube slots starting near the leading edge improves the hydrodynamics performance of the hydrofoil.

Scale-up of NiTiHf shape memory alloy tubes with high torque capability

High-torque, NiTiHf high-temperature shape memory alloy tubes were examined by means of constant-torque thermal cycling experiments. The alloy, with a Ni-rich composition of Ni50.3Ti29.7Hf20 (at%), was hot worked via extrusion from large ingots to produce final rods with an outer diameter of 25.4 mm. After aging at 550 °C for 3 h and air-cooling, the manufactured torque tubes were subjected to shear stresses from 0 to 500 MPa (torques of 0–1400 N m) and thermally cycled 20 times under stress, and twice after stress removal to evaluate the two-way shape memory effect. A transformation shear strain of 6% was obtained, and a maximum work output of 27.5 J cm−3. Two-way shear strains approached 3% strain without any extended training or cycling. The strain values obtained for the first time in this large-diameter, high-torque tube consistently matched smaller diameter tubes previously reported. This highlights the successful production and scale-up of both the material and the component level in torque tubes without degrading the actuation response, while providing much higher torque capability.

A Comparative Study of Standard PCNL vs Tubeless PCNL at a Tertiary Care Hospital

Introduction The role of percutaneous nephrostomy tube for drainage after percutaneous nephrolithotomy (PCNL) procedure has come under scrutiny in recent years. The procedure has been modified to use of small diameter tubes and tubeless PCNL. Aim & Objectives This study was done to evaluate perioperative characteristics, postoperative analgesic requirement, length of hospital stay and post-surgical complications between standard PCNL and tubeless PCNL. Methodology This prospective comparative study was conducted in department of surgery and radiodiagnosis of Rama Medical College, Hapur from June 2017 to September 2018 on 80 patients of nephrourolithiasis, who were randomly divided into two groups of 40 patients each, group A underwent standard PCNL while group B underwent tubeless PCNL. Post operatively, the efficacy of the operative procedure was analyzed based on the outcome of the procedure, duration of patient stay and post-operative complications. Result Majority of patient who had underwent PCNL were in age group of 21–60 years (mean age- 36.78 years) with a male predominance (M:F= 69:11). Operative time for tubeless PCNL (mean time ± SD = 59.97 ± 26.40 minutes) was shorter than for standard PCNL (mean time ± SD = 67.55 ± 28.00 minutes) but it was statistically insignificant (p value = 0.73462). 26 patients (65%) of tubeless PCNL were discharged within 48 hours while 33 patients (82.5%) of standard PCNL had to stay in hospital for a longer duration of 3–4 days. Post-operative analgesia requirement (Inj. Diclofenac) was significantly high in standard PCNL group (mean dose ± SD = 136.84 mg ± 39.12 mg) than in tubeless PCNL group (mean dose ± SD = 119.74 mg ± 36.13 mg, p value = 0.0026). Post-operative complications such as hematuria, urosepsis and leakage were also much less in tubeless PCNL (n=11, 27.5%) than in standard PCNL (n= 17, 42.5%). Conclusion Tubeless PCNL is a safe and effective technique and is associated with decreased pain, low analgesic requirement, less operating time and faster recovery. However it has its own limitation that precludes secondary procedure for the treatment, removal of internal stent, dysuria and need to visit hospital for subsequent removal of internal stent.

Convective boiling of R-410A in 5.0 and 7.0 mm outer diameter microfin tubes

ABSTRACTAlthough microfin tubes are widely used in refrigeration and air-conditioning industries, relatively little data are available for small diameter tubes. In the present study, 7.0 and 5.0 mm outer diameter (O.D.) microfin tubes were tested for a range of mass flux (from 50 to 250 kg/m2s) and vapor quality (from 0.2 to 0.8). The saturation temperature was 8°C and the heat flux was 3.0 kW/m2. This heat flux is quite small, and existing investigations have not been gone to this low heat flux. Results showed that an optimum behavior was observed for the enhancement factor. It increased as mass flux increased up to 150 kg/m2s, and then decreased with a further increase of mass flux. The penalty factors were larger than 1.0 except at the lowest mass flux of 50 kg/m2s. Possible reasoning was provided based on flow patterns of the microfin and the smooth tube. The enhancement factor ranged from 1.24 to 1.93 for the 7.0 mm microfin tube, and 1.63 to 3.26 for the 5.0 mm microfin tube. The penalty factor ranged from 0.82 to 1.11 and from 0.48 to 1.39 for the 7.0 mm and the 5.0 mm microfin tube, respectively. Larger high fin height of the 5.0 mm microfin tube may be responsible for the larger enhancement and penalty factor of the 5.0 mm microfin tube. Comparison with predictions by existing correlations revealed that 7.0 mm microfin tube data were reasonably predicted. However, 5.0 mm microfin tube data were generally underpredicted, probably due to the large fin height of the 5.0 mm microfin tube.

Improving efficiency of application foam sheets to remove liquid from gas wells

During the late stage of gas field development, the solution of specific issues is required to increase the flow rates of wells and reduce their water cut. The accumulated experience in the development of gas and gas condensate fields indicates that the most effective way to remove water accumulating in wells is to introduce foaming compositions based on surfactants to the bottom of the wells. The most technologically advanced application was the use of solid and liquid surfactants. The installation of smaller diameter tubing in the wells ensured the removal of fluid from the bottom of the well, but after several months of operation the conditions for removing the liquid from the bottom of the well deteriorate. Technologies for using concentric elevator systems and plunger elevators are used on a single number of wells. The main technology for removal of liquid from the bottom of gas wells is currently the technology for processing bottom holes with solid surfactants.

Carbon films deposition as protective coating of titanium alloy tube using PIII&D system

The purpose of this work is to deposit carbon films inside titanium alloy tube of small diameter, in order to increase the corrosion resistance of its inner surface. The use of carbon films as protective coating can increase the lifetime of the tubes used in propulsion and thermal control systems of satellites. They can also inhibit the permeation of corrosive species, originated from the fuels and the cooling fluids, between the film-metal interface. Titanium alloy tube with 11 mm diameter and 150 mm length, with one side closed configuration was placed inside a vacuum chamber and pulsed to a high energy voltage. Carbon film deposition was performed by using a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The hollow cathode discharges (HCD) were produced with pulses of 2 kV, 15 A, 20 μs, and 500 Hz of repetition rate, using a RUP-6 pulser. The maximum temperature measured at the surface of tubes was about 1000 °C. The as-deposited carbon films were analyzed in terms of their microstructure, chemical composition, surface morphology and thickness. The surface characterization of the carbon films were carried out by means of Raman Spectroscopy, Field Emission Gun Scanning Electron Microscopy (FEG-SEM), Atomic Force Microscopy (AFM) and Potenciodynamic Polarization tests. The experimental results show an interesting change on the chemical structure of the as-deposited carbon films, when the deposition time varied from 30 min to 240 min, resulting in thicker and quite adhered films on the inner surface of tubes. In addition, the changes on the microstructure, seen by SEM analysis, as well as the ID/IG variation indicate that nanocrystalline graphite (NC-G) films can be deposited on the inner surface of titanium tubes by using this type of PIII&D system.

Optimum fin geometries on condensation heat transfer and pressure drop of R1234ze(E) in 4-mm outside diameter horizontal microfin tubes

This study experimentally investigated the condensation heat transfer and pressure drop characteristics of R1234ze(E) inside horizontal small-diameter (4.0-mm) microfin tubes with three different types of fin geometries. The three fin geometries were as follows: 40 fins with a fin height of 0.18 mm and a helix angle of 18°, 50 fins with a fin height of 0.15 mm and a helix angle of 12°, and 50 fins with a fin height of 0.12 mm and a helix angle of 25°. The experiments were carried out for a range of mass velocities from 50 to 400 kg m−2 s−1 and at a saturation temperature of 35 °C. The heat transfer coefficient of the microfin tubes was compared to those of smooth tubes and was evaluated in terms of the heat transfer enhancement factor. The effects of different fin geometry parameters, such as the number of fins, fin height, and helix angle, on the heat transfer and pressure drop were investigated. The heat transfer coefficient increased at 50 kg m−2 s−1 as the number of fins increased. Fin height exerted the greatest influence on heat transfer enhancement at 200 kg m−2 s−1. The measured heat transfer coefficient and pressure drop were compared with previous correlations, and the practical effectiveness of the results was verified in terms of the previous our correlations for small-diameter microfin tubes.