Tube Separation Research Articles

Experimental studies on the Hartmann tube

Abstract The effect of tube depth, the separation distance between the tube and nozzle exit, and the nozzle pressure ratio on the characteristics of the flow coming out of the Hartmann tube was studied experimentally. The configuration used in this work consists of an underexpanded sonic jet emanating from a convergent nozzle directed into a closed-ended cylindrical tube of the same diameter (D) as the nozzle exit. The nozzle was operated at two levels of underexpansion corresponding to nozzle pressure ratio (NPR) 3 and 5. The distance (S) from nozzle exit and tube inlet was varied from 0.4D to 4D. Discrete high-amplitude tones (the jet regurgitant, JRG) were produced, only at certain (periodic) intervals (near the shock-cell terminations) of spacing for NPR 3, while for NPR 5 the JRG tones are produced at all points beyond the first shock-cell. For locations other than these, high-frequency tones (screech mode) were observed. The connection between the jet structure and operating modes revealed that the location of standoff shock ahead of the tube with respect to the jet structure plays a dominant role in the observed ‘modes’ rather than the nozzle tube separation. The results reveal that the frequency response of longer tubes in JRG mode approaches their quarter wave frequencies. The high-frequency oscillations observed in the screech mode showed independency with cavity (pipe) depth, contrary to the available literature, the transition between ‘different modes’ oscillation is a function of cavity depth.

An Investigation on Reduction of Calcium Added Bauxite Residue Pellets by Hydrogen and Iron Recovery through Physical Separation Methods

This study investigates the properties of H2-reduced calcium-added bauxite residue, self-hardened pellets, and the feasibility of iron recovery through electrostatic and magnetic separation methods. The oxide pellets are prepared via a mixing of bauxite residue, calcite, and quicklime. The self-hardened pellets are reduced at 1000 °C with hydrogen gas flow for 120 min. The chemical composition, phase identification, and microstructural observations are executed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. The porosity and strength of the self-hardened pellets are performed by the Mercury intrusion porosimetry and tumbling tests, respectively. The separation of iron is examined through a dry electrostatic technique, and in wet conditions, i.e., via Davis Tube and low-intensity magnetic separation (WLIMS). The effect of the magnetic field (0.1, 0.25, and 0.32 T) is tested on two different particle size fractions (−212 + 106 µm and −106 + 74 µm). It is found that most of the iron oxide in the bauxite residue is converted to metallic iron, which corresponds well with both XRD and SEM results. The Carpco electrostatic tests indicate that this approach is inefficient for the studied type of material because of the intensive association of iron with the rest of the components leading to transferring it to the middling rather than to conductive product. However, both the Davis Tube and WLIMS approve a reasonable improvement in the Fe content from 22% to 37% with acceptable recoveries. The results of the Davis Tube show that there is an optimum magnetic field and particle size for maximization of Fe grade and recovery. Finally, further suggestions are highlighted for the physical beneficiation of studied bauxite residue with the purpose of maximizing iron grade and recovery.

Properties and mechanism of SBS/crumb rubber composite high viscosity modified asphalt

Previous studies have shown that traditional modified asphalt is difficult to meet the requirements of road quality at the requirements of permeable pavement quality at complex service environments. SBS/crumb rubber composite high viscosity modified asphalt(SBS/CR) was prepared by adding tackifying resin and other modifiers. Standard tube separation tests and rheological results showed that the SBS/CR has better high-temperature performance and storage stability. Atomic force microscopy (AFM) results concluded that the modifiers formed a stable network structure in asphalt system, restricting the free movement and diffusion of asphalt molecules. Asphalt molecules undergo phase changes in a small range, resulting in a "Bee structure" with a large number, small area, and uniform distribution, which improved its surface roughness. Fourier infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyses confirmed the modification mechanism includes both chemical reaction and physical modification. The tackifying resin was mainly combined with the asphalt binder in the form of physical fusion. Compared with matrix asphalt, the internal structure of the SBS/CR was more stable, the heat absorption area became smaller, and the thermal stability was improved.

New Technology and Experimental Research on Thick-Walled Tube Fatigue Impact Loading Precision Separation

Traditional separation methods for thick-walled metal tubes include turning and sawing, which suffer from wasted raw material and low efficiency. In view of this, this paper proposes a new process of using impact load to promote crack generation and tube separation. Based on the principles of radial repeated impact load, stress concentration effect and fatigue fracture, the rapid initiation and stable expansion of tube fatigue crack are promoted. In addition, the crack initiation mechanism of the tube V-notch root cracks under radial repeated load when the tube is in a restrained state. For the experimental study of the GCr15 steel tube, a multistep decline frequency time tube separation control curve with an initial frequency from 4 Hz to 31 Hz and termination frequency from 1 Hz to 8.5 Hz was designed, and the precision tube separation device is loaded by pneumatic fatigue shock to achieve tube precision separation. In addition, a tube fracture quality evaluation method is proposed. According to the test results, the stress concentration effect of V-notch can significantly reduce the average stress in the process of tube fatigue separation and accelerate the generation of microcracks. Under the continuous action of repeated impact load, the loading method of multistep decline can effectively control the rapid crack initiation and stable expansion of the GCr15 tube V-notch root crack. Moreover, the tube final fracture region has relatively small defects, which can obtain good fracture quality.

Study on the influence of tube surface notch on crack initiation during blanking

In the process of precision tube separation, according to the prefabricated notches on the outer surface of the tube, the notch effects of different types of notches are studied, and the influence of the stress field at the root of the annular V-shaped notch is analyzed. It is determined that the notch angle, notch depth and the radius of the bottom angle of the notch root are the three main parameters that affect the stress field at the root of the notch, and the mathematical expression of the V-notch parameters suitable for tube separation is derived. The design of tube precision separation notch is put forward, and four different notches are numerically simulated. It is concluded that 45° asymmetric V-shaped notch and annular V-shaped notch facing the cutting end are the two notches which are more suitable for the blanking method in this paper. An experimental study is carried out on the crack propagation caused by the notch, and the experimental results are consistent with the numerical simulation results.

Electrochemically Reduced Titania Nanotube Synthesized from Glycerol-Based Electrolyte as Supercapacitor Electrode

In this paper the synthesis of self-organized Titania nanotubes (TNTs) by a facile potentiostatic anodization in a glycerol-based electrolyte is reported. The optimized TNTs were subsequently reduced through a cathodic reduction process to enhance its capacitive performance. FESEM and XRD were used to characterize the morphology and crystal structure of the synthesized samples. XPS analysis confirmed the reduction of Ti4+ to Ti3+ ions in the reduced Titania nanotubes (R-TNTs). The tube diameter and separation between the tubes were greatly influenced by the applied voltage. TNTs synthesized at voltage of 30 V for 60 min exhibited 86 nm and 1.1 µm of tube diameter and length, respectively and showed high specific capacitance of 0.33 mF cm−2 at current density of 0.02 mA cm−2. After reduction at 5 V for 30 s, the specific capacitance increased by about seven times (2.28 mF cm−2) at 0.5 mA cm−2 and recorded about 86% capacitance retention after 1000 continuous cycling at 0.2 mA cm−2, as compared to TNTs, retained about 61% at 0.01 mA cm−2. The charge transfer resistance drastically reduced from 6.2 Ω for TNTs to 0.55 Ω for R-TNTs, indicating an improvement in the transfer of electrons and ions across the electrode–electrolyte interface.

Experimental characterization of storage stability of crumb rubber modified bitumen with warm-mix additives

One of the main drawbacks of crumb rubber modified bitumen (CRMB) is the storage stability issue. The storage instability of CRMB impedes its further application. This study aims to develop a robust methodology to evaluate the storage stability of CRMB binders using both mechanical and morphological tests. The effects of rubber contents (0, 5%, 10%, 15%, 22% by weight of bitumen) and different non-foaming warm-mix additives (wax-based and chemical-based additives) on the storage stability of CRMB were investigated. Laboratory tests were also performed on the constituents of CRMB to have a deep understanding of the mechanism of storage instability. Standard tube separation tests were conducted on different binders. Both rheological tests and X-ray computed tomography (CT) scan tests were performed on the binder samples collected from different parts of the tube test. Separation indices were developed based on the difference in mechanical property and rubber content from the tube samples respectively. Results show that CRMB with a higher rubber content is more storage stable than that with a lower rubber content. The addition of warm-mix additives is detrimental to the storage stability of the studied CRMB. Rheological tests were performed on the individual constituents of CRMB (i.e., bitumen phase and rubber phase) to understand better the dynamic asymmetry potentially existing within the unstable CRMB binder. Results show that the residual bitumen becomes stiffer while the swollen rubber becomes softer after interaction because of the preferential absorption of light components of bitumen by rubber. The dynamic asymmetry existing between the bitumen phase and the rubber phase of CRMB results in storage instability. When the bitumen phase has similar dynamic properties as the rubber phase, the resulted binder system will be stable. It is possible to manipulate raw material properties and interaction conditions to achieve the desired crossover between two phases of CRMB and hence obtain a storage-stable CRMB blend.

Description of a novel technique for surgical placement of gastrostomy tubes in dogs.

Early enteral nutrition in dogs with critical illnesses, including septic peritonitis, has been shown to have a positive influence on patient outcome. Surgical placement of a gastrostomy tube (GT) is one option for providing early enteral nutrition. Complications, including premature tube removal or separation of the stomach from the body wall, can result in leakage of gastric contents into the abdominal cavity and subsequent peritonitis. A safe and reliable technique for the placement of a GT is desirable to minimize such complications. A modified method for surgical placement of a GT is described. A thoracic trocar catheter (TTC) with an attached Pezzer tube is inserted through a gastrotomy incision and exited through the left gastric body and body wall. A left-sided tube gastropexy is performed using an interlocking box (ILB) pattern. GT placement using a TTC is efficient, requiring minimal additional anesthesia time. The gastric defect created by the TTC conforms well with the Pezzer tube. As such, placement and utilization of the ILB suture pattern enables removal of the GT in the early postoperative period, if appropriate.

Energy Output Efficiency of Shielded Mild Detonation Cord in Cylinder Structures

Expanding tube separation device is a commonly used linear separation device, whose energy resource is a shielded mild detonation cord (SMDC). In this research, the SMDC is a mild detonation cord sheathed in flat polyethylene. Two experiments were achieved to discuss the energy output efficiency of the SMDC. In the first experiment, the SMDC was inserted into 1060 aluminum cylinder directly. While in the other experiment, the SMDC was insert into aluminum cylinder after contained within a flat steel tube. The velocity and displacement of the characteristic points on the outer surface of the aluminum cylinder during explosion were measured by photonic Doppler velocimetry (PDV). The simulation results with Ls-dyna fluid-solid coupling algorithm correspond well with the experimental results. According to the simulation analysis, the distribution of total energy of explosives were obtained. The plastic strain energy of the aluminum cylinder corresponds to the ability of the SMDC to do external work. The result shows that, 39.3% of the total energy in the explosive is output to aluminum cylinder with SMDC acting on it directly, while the energy output efficiency turns to 20.8% after passing through the flat tube.

Two-phase modeling of nanofluid forced convection in different arrangements of elliptical tube banks

PurposeThe purpose of this study is two phase modeling of Water/Cu nanofluid forced convection in different arrangements of elliptical tube banks in a two-dimensional space.Design/methodology/approachThe arrangements of tube banks have been regarded as equal spacing triangle (ES), equilateral triangle (ET) and the rotated square (RS). The obtained results indicate that, among the investigated arrangements, the RS arrangement has the maximum value of heat transfer with cooling fluid. Also, the changes of Nusselt number and the local friction factor are under the influence of three main factors including volume fraction of slid nanoparticles, the changes of fluid velocity parameters on the curved surface of tube and flow separation after crossing from a specified angle of fluid rotation.FindingsIn Reynolds number of 250 and in all arrangements of the tube banks, the behavior of Nusselt number is almost the same and the separation of flow happens in almost 155-165 degrees from fluid rotation on surface. In RS arrangement, due to the strength of vortexes after fluid separation, better mixture is created and because of this reason, after the separation zone, the level of local Nusselt number graph enhances significantly.Originality/valueIn this research, the laminar and two-phase flow of Water/Cu nanofluid in tube banks with elliptical cross section has been numerically investigated in a two-dimensional space with different longitudinal arrangements. In this study, the effects of using nanofluid, different arrangements of tube banks and the elliptical cross section on heat transfer and cooling fluid flow among the tube banks of heat exchanger have been numerically simulated by using finite volume method.

Analyzing separation capacity efficiency of a binary hydrocarbon system (Cyclohexane - N-Pentane) with the help of two distinct methods: Utilizing A Vortex Tube Separator and An Equilibrium Flash Stage (EFS)

The fundamental objective of this preliminary investigation was to simulate the desired separation in a commercially available vortex tube, using a system of hydrocarbons as a surrogate for air. A bench-scale system was constructed, a mixture of 21% cyclohexane and 79% n-pentane was selected, and a parametric study was devised to evaluate the effect of feed conditions on vortex tube separation performance. The desired separation was not achieved using the commercial vortex tube, a unit which was designed for air flow rates much higher than we were using in the bench scale environment. Modifications were made to the equipment in an effort to compensate for the lower flow rates; however, these modifications did not improve attempts to achieve the desired separation. All of the data seem to indicate that the best separations achieved in this study were only equivalent to one equilibrium flash stage. Many of the separations did not even match the equilibrium flash case, which suggests that the action of the commercial vortex tube used in this study produced mixing, entrainment, of other processes which serve to reduce the separation when compared to that of an equilibrium flash.

Combined recurrent laryngeal nerve monitoring and one-lung ventilation using the EZ-Blocker and an electromyographic endotracheal tube

BackgroundIntraoperative neuromuscular monitoring (IONM) is a widespread procedure to identify and protect the recurrent laryngeal nerve (RLN) during thyroid surgery. However, for left thoracic surgery with high risk of RLN injury, both reliable recurrent laryngeal nerve monitoring and one-lung ventilation could interfere.MethodsIn this prospective study, a new method for IONM during one-lung ventilation combining RLN monitoring with an electromyographic (EMG) endotracheal tube (ETT) and lung separation using the EZ-Blocker (EZB) is described and its clinical feasibility and effectiveness were assessed.ResultsA total of 14 patients undergoing left upper lobe surgery and left upper mediastinal lymph node dissection were enrolled. The EZB was introduced and positioned without any problems and sufficient lung collapse was achieved in all patients. No tracheobronchial injuries or immediate complications occurred. A stable EMG signal was present in all patients and no RLN palsy and no negative side effects of the NIM EMG ETT or the EZB were observed postoperatively.ConclusionsThe described method is technically feasible, easy to apply and save. It provides both reliable IONM and independent lung separation for optimal surgical exposure. The combined use of the EZB and the NIM EMG ETT might reduce the risk for RLN palsy and impaired lung separation during left thoracic surgery with high risk for RLN injury.

Natural convection mass and heat transfer at a horizontal spiral tube heat exchanger

The free convection mass and heat transfer (by analogy) behavior of a spiral tube was studied by an electrochemical technique which involved measuring the limiting current of the cathodic deposition of copper from acidified CuSO4. Variables studied were tube diameter (d), tube separation (s) and physical properties of the solution. The data were correlated for the conditions 1.4×106<Sc⋅Gr<5.74×108 by the equation: Sh=0.01 Sc⋅Gr0.29sd−0.5.A comparison of the present data with the data previously obtained for helical tubes and horizontal tubes was made. The importance of the present work for predicting the rate of diffusion controlled metal finishing processes which may be performed on the spiral tube during fabrication such as electroplating, etching, electroless plating and electropolishing was highlighted. Also potential application of the present data for predicting the rate of heat transfer at the outer surface of the spiral tube heat exchanger under stagnant conditions or under weak forced convection where natural convection contributes a great deal to the rate of transfer was pointed out.

Hollow-core fiber with nested anti-resonant tubes for low-loss THz guidance

A hollow-core fiber with nested anti-resonant node-free cladding tubes suitable for broadband THz guidance with low transmission losses is proposed. It is shown that the tube separation and tube thickness of the inner elements have a significant effect on the confinement loss and effective material loss of the fiber in the THz band. Using TOPAS copolymer, the proposed fiber was optimized for operation at 1 THz and it is predicted from numerical simulations that loss can be reduced to as low as 0.05 dB/m with a 0.6 THz wide dispersion flattened bandwidth.

Study and Build-Up of Deformation Zone at Cutting of Thin-Walled Tube by Torsion

Intensive development of Russian aviation and aerospace industries put an emphasis to the problem of quality of using materials and workpieces and to the value of technical and economical indexes in the context of planned production level [1, 2]. Waste-free technologies are preferred. Cutting by torsion or cutting by shear are preferable technologies if thin-walled tube cutting is the main blanking operation. Build-up of workpiece deformation zone plays an important role in the cutting process. Deformation zone determines stability of details during further processing and exploitation. An extended research was conducted about tube separation process using torsion with an active counterpressure. Some parameters was defined in the result of research, in particular: distribution of deformation zone along length and thickness of workpiece, angular deflection and compression force and workpiece heating temperature impact on build-up of whisker disposition in the cut zone. It allows identifying optimum compression force range and temperature conditions. Compliance with recommended practices allows conducting thin-walled tube separation simultaneously with build-up on the workpieces whisker structure that is fortunate for further pressure treatment and exploitation.

Study of Preanalytic and Analytic Variables for Clinical Next-Generation Sequencing of Circulating Cell-Free Nucleic Acid

Detection of mutations in plasma circulating cell-free DNA (cfDNA) by next-generation sequencing (NGS) has opened up new possibilities for monitoring treatment response and disease progression in patients with solid tumors. However, implementation of cfDNA genotyping in diagnostic laboratories requires systematic assessment of preanalytical parameters and analytical performance of NGS platforms. We assessed the effects of peripheral blood collection tube and plasma separation time on cfDNA yield and integrity and performance of the Ion PGM, Proton, and MiSeq NGS platforms. cfDNA from 31 patients with diverse advanced cancers and known tumor mutation status was deep sequenced using targeted hotspot panels. Forty-five of 52 expected mutations and two additional mutations (KRAS p.Q61H and EZH2 p.Y646F) were detected in plasma through a custom bioinformatics pipeline. We observed comparable cfDNA concentration/integrity between collection tubes within 16 hours of plasma separation and equal analytical performance among NGS platforms, with 1% detection sensitivity for cfDNA genotyping.

Extension of staggered-grid-based AUSM-family schemes for use in nuclear safety analysis codes

To overcome the numerical difficulties of the density-based method for low-Mach-number two-phase flow, this paper adopts the AUSM+ and AUSMDV schemes based on a staggered-grid arrangement. The water faucet, air-water shock tube, oscillating manometer and air-water phase separation problems are used as benchmark tests to validate the implementation of the generic four-equation two-fluid model. The present results reveal the advantages of using staggered-grid-based AUSM+ and AUSMDV schemes over the collocated-grid-based counterpart. With a staggered-grid arrangement, odd-even decoupling issues can be avoided. Thus, no sound speed scaling or additional diffusion terms are needed when using AUSM+ and AUSMDV schemes for low-Mach-number two-phase flow. Furthermore, since the pressure and void fraction are already stored at the interface of the velocity control volume, no interpolation of interfacial pressure is needed for momentum equations. Finally, this study will help integrate AUSM+ and AUSMDV schemes into staggered-grid-based thermal hydraulic codes, e.g. CATHENA, used in the nuclear industry. Moreover, to tackle the stiffness issues in relation to phase appearance and disappearance, we propose a new staggered-grid-based scheme referred to as AUSMFVS, which combines the accuracy of AUSM+ and the stability of FVS.

Development and Enhancement of Thin-Walled Tube Separation Methods

The correct choice of a metal separation method, in particular for thin-walled tubes, is vital for technical and economical performance indices in aircraft building. The most important selection criteria are separation quality, the amount of waste, possibility to consolidate operations and equipment efficiency. These factors require ongoing development &amp; enhancement of tube separation methods. Waste-free technological processes like torsion tube sectioning are preferred. As the result of the extended research of tube separation process using torsion with active counterpressure, particularly the effect of structural parameters on cut quality, optimum tolerance for clearance fit between dies was defined. Compliance with recommended practices during equipment manufacturing will let cut quality reach the value peculiar to the quality value of sectioning method of separation using metal-cutting equipment. Herewith manufacturing becomes waste-free and quarantines calibration of sections adjacent to the cut.

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations.

In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces.

Tube radial distribution phenomenon with a two-phase separation solution of a fluorocarbon and hydrocarbon organic solvent mixture in a capillary tube and metal compounds separation.

A fluorocarbon and hydrocarbon organic solvent mixture is known as a temperature-induced phase-separation solution. When a mixed solution of tetradecafluorohexane as a fluorocarbon organic solvent and hexane as a hydrocarbon organic solvent (e.g., 71:29 volume ratio) was delivered in a capillary tube that was controlled at 10°C, the tube radial distribution phenomenon (TRDP) of the solvents was clearly observed through fluorescence images of the dye, perylene, dissolved in the mixed solution. The homogeneous mixed solution (single phase) changed to a heterogeneous solution (two phases) with inner tetradecafluorohexane and outer hexane phases in the tube under laminar flow conditions, generating the dynamic liquid-liquid interface. We also tried to apply TRDP to a separation technique for metal compounds. A model analyte mixture, copper(II) and hematin, was separated through the capillary tube, and detected with a chemiluminescence detector in this order within 4 min.