Inner Wall Of Tube Research Articles

Increased hydraulic resistance in tubes of once-through boiler due to fouling: A case study of 650 MWe ligite fired unit

The analysis of pressure changes in water and steam flow along the entire once-through steam boiler tube system at the 650 MWe lignite fired Unit was carried out after the long operational period of almost 30 years without a chemical cleaning of the pipe system. A significant increase of the hydraulic resistance was recorded in comparison to the design values in the evaporator tubes, both in the water heating zone and in the evaporation zone with the two-phase mixture flow. The cause of this adverse effect is the formation of a wavy surface of the magnetite layer deposited on the inner wall of tubes. The significantly increased absolute roughness on the inner wall of tubes was determined on the basis of measured pressure drops at sections of the tube system and numerical calculation performed with a thermal-hydraulic model of single-phase and two-phase water and steam tube flows. The model is based on the steam-water two-fluid model with mass, momentum and energy balance equations and mechanistic correlations for the steam-water interface transfer processes. The model is suitable for the single and two-phase flow parameters prediction in the span from subcritical to supercritical and near critical pressure conditions. Conducted calculations provide detailed insight in the fluid pressure, velocity and temperature change in the boiler tube system. After the long operational period the pressure drop in evaporating tubes almost doubles in comparison to the design values. The presented results are a support to boiler's design, operational procedures and maintenance.

Failure analysis of sulphidation-oxidation corrosion of Incoloy 800HT superheater tube

The burst of an Incoloy 800HT superheater tube, operating at 160–690 °C steam was investigated using metallographic inspection and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). It was observed that the analyzed fracture surface has an intergranular cracks morphology. Corrosion product deposits were also found on the inner wall of the failure tube. The microstructure analysis of the tube samples showed that the inner wall of the tube was covered by a layer of loose oxide and intergranular cracks propagated from the inner surface towards the outer wall of the tube. The elemental EDS results of the corroded tube samples showed a sulfur-rich layer between the matrix and oxide layer, and the sulfur was also found in the white corrosion depositions. The performed test results revealed that the tube burst was caused by a local overheat-induced sulfidation-oxidation process. Finally, the failure mechanism was discussed and suggestions were made to prevent occurrence of similar failures.

Endothelialized microvessels fabricated by microfluidics facilitate osteogenic differentiation and promote bone repair

In bone tissue engineering, vascularization is one of the critical factors that limit the effect of biomaterials for bone repair. While various approaches have been tried to build vascular networks in bone grafts, lack of endothelialization still constitutes a major technical hurdle. In this study, we have developed a facile technique to fabricate endothelialized biomimetic microvessels (BMVs) from alginate-collagen composite hydrogels within a single step using microfluidic technology. BMVs with different sizes could be readily prepared by adjusting the flow rate of microfluids. All BMVs supported perfusion and outward penetration of substances in the tube. Endothelial cells could adhere and proliferate on the inner wall of tubes. It was also found that the expression of CD31 and secretion of BMP-2 and PDGF-BB were higher in the rat umbilical vein endothelial cells (RUVECs) in BMVs than those cultured on hydrogel. When co-cultured with bone marrow mesenchymal stem cells (BMSCs), endothelialized BMVs promoted the osteogenic differentiation of BMSCs compared to those in acellular BMV group. In vivo, markedly enhanced new bone formation was achieved by endothelialized BMVs in a rat critical-sized calvarial defect model compared to those with non-endothelialized BMVs or without BMVs. Together, findings from both in vitro and in vivo studies have proven that endothelialized BMVs function to facilitate osteogenesis and promote bone regeneration, and therefore might present an effective strategy in bone tissue engineering. Statement of significanceIn bone tissue engineering, limited vascularization is one of the critical factors that limit the effect of biomaterials for bone repair. In this study, we developed a facile technique to fabricate endothelialized biomimetic microvessels (BMVs) from alginate-collagen composite hydrogels within a single step using microfluidic technology. Both in vitro and in vivo studies have proven that endothelialized BMVs function to facilitate osteogenesis and promote bone regeneration, and therefore might present an effective strategy in bone tissue engineering.

A new method for polishing the inner wall of a circular tube with a soft abrasive rotating jet

There are limitations on the tool size and geometric constraints when the inner wall of a tube is polished by the traditional polishing method. This paper proposes a new soft abrasive rotating jet polishing (SARJP) method to polish tubes. A new tool with a stepless adjustable incident angle of the polishing fluid was designed to perform an experimental study on the inner wall of a stainless-steel tube. This study also proposes to combine the Taguchi method and response surface technique to improve the speed and quality of the optimization of the polishing process. In this paper, some mathematical statistics and graphs tools were used to comprehensively access the influence of various factors on the roughness of the inner wall of the tube. Under these optimum conditions, the average surface roughness of the inner wall decreases from 1.05 μm to 0.212 μm, and the surface roughness improvement rate is 79.8%.

Mathematical Model Represents the Effect of Flexible Endoscopy on Suspension Fluid Flow

In this manuscript, peristaltic transport induced by a sinusoidal traveling wave in the case for a viscous incompressible Newtonian fluid mixed with rigid spherical particles in the presence of a flexible inner tube, where the inner tube is also moving with a sinusoidal traveling wave of moderate amplitude is studied. The governing equations of the mixture (fluid-particle suspension) are written in two-dimensional cylindrical coordinates. The long-wavelength approximation is used to simplify the system of equations (d<<1). The velocities distribution for both fluid and particles are obtained and evaluated numerically with discussion for special cases. The flow rate, pressure drop, friction forces and shear stress at the outer and inner walls of tubes are derived and represented graphically. In the urinary system, peristalsis is due to involuntary muscular contractions of the ureter wall which drives urine from the kidneys to the bladder through the ureters. A mathematical analysis of peristaltic flow with application to the ureter in presence of flexible endoscopy (Peristaltic Endoscope) is taken as a real application in this study. Finally, conclusions of the research and recommendations for future work are discussed. The results obtained may be relevant to the transport of other physiological fluids and industrial applications in which peristaltic pumping is used.

Investigation of cold drawing process of thin-walled ribbed steel tube

Cladding tube is an important part of nuclear power components. This paper presents a simulation and experimental study on the cold drawing process of one kind of cladding tubes, namely thin-walled ribbed steel tube. Three kinds of drawing processes are studied: single pass drawing, tube sinking and fixed-plug combined drawing process, and two pass fixed-plug drawing process. The finite element (FE) simulation model considering Johnson-Cook constitutive equation is established to analyze the effective stress, effective plastic strain, and contact force in different drawing processes. Different out diameter (OD) and wall thickness (WT) 316L stainless steel (SS) tubes are used to investigate the forming process of the ribbed tube. Furthermore, experiments with the same parameter settings are compared with the simulations. It is found that the simulation and experimental results are in good agreement, the ribs height highly depends on the tube OD and WT. The results show that the formation of tube ribs is caused by the extrusion of the drawing die. In addition, during the forming of the tube ribs, inner grooves will be formed on the inner wall of tube, and the fixed-plug drawing process can effectively reduce the depth of the inner groove. Finally, the microstructure and hardness of the ribbed tube at different position are investigated. This work provides a reference for the integrated forming process of the ribbed tube.

Facile Repair of Anti‐Corrosion Polymeric Composite Coatings Based on Light Triggered Self‐Healing

SELF-HEALING MATERIALS Frontispiece: In article number 2100106 by Liang Fang, Chunhua Lu, and co-workers, light induced self-healing composite coatings are prepared and used for inner walls of tubes. Silane-modified epoxy chains facilitate crack closure before healing due to reversible crosslinking based on the Diels–Alder reaction. CeO2 nanoparticles are grown on graphene nanosheets for both photothermal effects and anti-corrosion.

Homogeneous surface hydrophilization on the inner walls of polymer tubes using a flexible atmospheric cold microplasma jet

AbstractThe intrinsic hydrophobic nature of polymer tubes limits their applications in biomedical and mechanical fields. In this paper, homogeneous hydrophilization on the inner surfaces of polytetrafluoroethylene tubes was realized by directly inserting a flexible atmospheric cold microplasma jet (FμPJ) into the tubes. The water contact angle, surface morphologies, and chemical compositions of the treated inner surfaces were investigated to characterize the plasma hydrophilization. Results demonstrated that the wettability of the inner walls of the tube was well improved and the wettability could be retained at a low value even after 30 days of storage. Notably, homogeneous hydrophilization was achieved along the axial and circumferential directions of the tube. The results indicated that FμPJ shows great potential for uniform inner surface modification of polymers tubes.

MHD flow and heat transfer analysis of fractional Oldroyd-B nanofluid between two coaxial cylinders

In previous study on the flow of fractional viscoelastic fluid between two coaxial cylinders, due to the complexity of computation, researchers commonly assume that the flow area is a rectangular pipe. This paper studies two-dimensional magnetohydrodynamic (MHD) flow and heat transfer of fractional Oldroyd-B nanofluid between two coaxial cylinders with variable pressure. The boundary layer fractional cylindrical governing equations are firstly formulated and derived. Meanwhile, the numerical solutions are obtained by using the newly developed finite difference method combined with L1-algorithm, whose validity is confirmed by the comparison with the exact solution constructed. Results show that the fractional derivative parameters α1, β and exponent parameter δ related to the wall temperature have significant effects on velocity and temperature fields. Specifically, the velocity decreases with the augment of α1, but increases as β rises up. The temperature profiles intersect each other for different δ. Meanwhile, increasing δ leads to an increase in temperature near the wall of inner tube, but a decline near the outer cylinder, which demonstrates increasing exponent parameter can enhance heat transfer.

Cell Repellent Coatings on Inner Walls of Tubes by Means of Transporting Discharge in Atmospheric Pressure

We report a method to obtain biocompatible PEG copolymer coatings inside high density polyethylene and Pyrex tubes, which was successfully developed by using a transporting discharge. The latter being a dry process, it is easier to apply as compared to the conventional multistep wet chemical techniques. The results presented in this paper show that for a 70 cm tube good cell repellent properties as compared to the control was obtained for the entire length of the tube. The best nonfouling properties with respect to CT-26 (colon cancer) were obtained for coatings presenting the best retention of ether functionalities from the DEGME monomer i.e. between 5 and 25 cm downstream of the tube. These results are interesting for surface modification of biomaterial and biomedical devices, which present hollow bodies.

Numerical Investigation of Shell and Tube Heat Exchanger with Twist Annular

Twist geometry of the annular of shell with circular tube heat exchanger was studied numerically. The analysis includes 3-D simulation for two models using profitable software ANSYS FLUENT 16.0. The analysis conditions for the models which solved was considerd constant of temperature for wall of inner tube, whereas the shell outer wall was insulated. First model involves a straight annular, whereas the second model involves a twist annular. Water was used as fluid flow for both models. Different Reynolds number for annular of heat exchanger namely (500- 6000 with step increase by 500) were employed for both models. The consequences showed annular form is important efficacious preceding the thermal presentation and enhancement with all consequences of twist regime when associated with straight regime excluded growing in input-output temperature of 24.2%, outlet annular temperature of 5.8%, whereas the increasing in Nusselt number was 30.3%, and the enchainment in pressure drop is 28.2% due to centrifugal forces.

Evaluation of biomarkers for haemocomopatibility of polymer biomaterials

Tubes are indispensable in our daily life, mechanical engineering and biomedical fields. However, the practical applications of tubes are sometimes limited by their poor wettability. Reported herein is hydrophilization of the tube inner wall by transferred atmospheric pressure plasma (TAPP). An Ar atmospheric pressure plasma jet (APPJ) is used to induce He TAPP inside polytetrafluoroethylene (PTFE) tube to perform inner wall surface modification. Optical emission spectrum (OES) is used to investigate the distribution of active species, which are known as enablers for surface modification, along the TAPP. Tubes’ surface properties demonstrate that after TAPP treatment, the wettability of the tube inner wall is well improved due to the decrease of surface roughness, the removal of surface fluorine and introduction of oxygen. Notably, a deep surface modification can significantly retard the aging of the obtained hydrophilicity. The results presented here clearly demonstrate the great potential of TAPP for surface modification of the inner wall of tube or other hollow bodies, and thus a uniform, effective and long-lasting surface modification of tube with any length can be easily realized by moving the tube along its axis.

Wear damage and effects of graphene-based lubricants/coatings during linear reciprocating sliding wear at high contact pressure

The present study reports on the ‘wear damages’ caused at inner surfaces (and sub-surfaces) of extruded zircaloy-4 tube specimens (as half cylinders) during interactive linear reciprocating sliding against outer surfaces of D2 steel half cylinders for different durations (up to 120s) at high contact pressures (of ~ 1GPa) in the absence/presence of mineral oil lubricant (having chlorinated extreme pressure additives) and graphene-based lubricants/coatings [viz., CVD-grown films of well-ordered few layers graphene (~ 7 layers) and thicker graphite (~ 1400 layers)]. The tests were conducted using a custom-made friction-and-wear tester, which also replicates the conditions (in terms of contact geometry, pressure, stroke length and frequency) relevant to the tribological phenomena occurring at the inner walls of tubes subjected to cold pilgering process. Even though none of the lubricants/coatings had any effect on coefficient of friction, presumably because of ‘boundary lubrication’ at such high contact pressures, only the graphene-based lubricants/coatings slowed down the evolution of surface roughness and wear damage. Observations of worn (top)surfaces and cross-sections indicate that ‘wear damages’ at such contact pressures are primarily caused by severe sub-surface deformation and defect/crack initiation/propagation, followed by lateral chipping/delamination; which could be suppressed by the graphene-based lubricants/coatings (but not by the oil-based lubricant).

Numerical investigation of erosion of tube sheet and tubes of a shell and tube heat exchanger

Abstract The failure of shell and tube heat exchangers caused by solid particle erosion has been a major problem in the oil and gas and other industries. Predicting erosion is still a developing art, an accurate simulation method is then significant to analyze the erosion characteristics in such complex geometry and determine erosion rate of metal surface. In this work a physical model was proposed to simulate the erosion of two-pass shell and tube heat exchangers with computational fluid dynamics. The simulation was performed for different feed fluid rates and a range of sand particle sizes from 0.1 to 1000 μm. The erosion rates of tube sheet, tube ends in the inlet plenum and the inner wall of tubes were monitored and the influences of flow pattern, particle size and particle behaviors on erosion were studied. The predictions are compared with the earlier studies and a good agreement was found. The particles can be classified into three groups based on the dependence of erosion rates of tube sheet and tubes on the particle size. The large particles (>200 μm) exhibited a near-linear influence on the erosion rates. The small particles (about 50–200 μm) produced approximate size-independence facet-average erosion rate of tubes, but the maximum local erosion rates of the tubes and tube sheet sharply increased with the decrease of particle size. The fine particles (

Three-dimensional inverse heat conduction modeling of a multi-layered hollow cylindrical tube using input estimation algorithm and thermal resistance network

High-temperature gas flow can cause melt, crack, erosion, and wear of tubes. In order to reduce these side effects, the inner wall of a hollow cylindrical tube is generally coated with a resistive material, for example, a steel pipe coated with a chrome layer. In addition, it is important to know heat flux applied to the tube wall and temperature distribution in the tube wall for appropriate design of the hollow cylindrical tube. In this study, three-dimensional inverse heat conduction modeling of a multi-layered hollow cylindrical tube was conducted. The thermal resistance network (TRN) scheme was employed to solve the heat conduction in the tube. The temperature distribution in the tube was estimated from a measured temperature on the outer wall of the tube by Kalman filter. At the same time, unknown heat flux on the inner wall of the tube was calculated by the recursive least squares algorithm.

Surface modification of tube inner wall by transferred atmospheric pressure plasma

Tubes are indispensable in our daily life, mechanical engineering and biomedical fields. However, the practical applications of tubes are sometimes limited by their poor wettability. Reported herein is hydrophilization of the tube inner wall by transferred atmospheric pressure plasma (TAPP). An Ar atmospheric pressure plasma jet (APPJ) is used to induce He TAPP inside polytetrafluoroethylene (PTFE) tube to perform inner wall surface modification. Optical emission spectrum (OES) is used to investigate the distribution of active species, which are known as enablers for surface modification, along the TAPP. Tubes’ surface properties demonstrate that after TAPP treatment, the wettability of the tube inner wall is well improved due to the decrease of surface roughness, the removal of surface fluorine and introduction of oxygen. Notably, a deep surface modification can significantly retard the aging of the obtained hydrophilicity. The results presented here clearly demonstrate the great potential of TAPP for surface modification of the inner wall of tube or other hollow bodies, and thus a uniform, effective and long-lasting surface modification of tube with any length can be easily realized by moving the tube along its axis.

The Characteristic of Inner Surface Coating on Porous Al<sub>2</sub>O<sub>3</sub> Tube by Electrophoretic Deposition

The nano-porous Al2O3 layer was performed onto inner surface of micro- porous Al2O3 tube by using electrophoretic deposition (EPD). Initially, Polypyrrole (Ppy) was applied on inner wall of tube to make conductive surface. The Al2O3 deposition was carried out in Al2O3 suspension with 5 wt % solid content in ethanol medium system using various applied voltages. Thickness of the deposited layer depends on applied voltages, after sintering at 1400oC the morphology of the deposited layer was investigated by FE-SEM. The good deposited surface without cracks and peeling has been prepared under applied voltage condition of 10 V.

822 準大気圧プラズマCVDによるDLC円管内面コーティング

822 準大気圧プラズマCVDによるDLC円管内面コーティング

Platinum-modified SiO2 with tubular morphology as efficient membrane-type microreactors for mineralization of formic acid

SiO2 amorphous tubes with the internal diameter ranging between 5 and 170 nm and having the aspect ratios typically >50, were prepared using DL-tartaric acid as inorganic template. The tubular SiO2 was impregnated with a platinum precursor (H2PtCl6), dried and then reduced with H2. The TEM, XPS, FTIR characterization methods revealed that platinum species were located preferentially on the inner walls of tubes having diameter smaller than 100 nm. The walls of SiO2 nanotubes proved to be amorphous and highly porous, the diameter of pores covering a wide range of radii. The macroporosity of the SiO2 tubes originated from the open ends of the tubes with the diameter ≥100 nm, whereas the pores located in the walls of tubes were responsible for the meso and microporosity. Finer Pt nanoparticles (0.9 nm average size) were obtained after the catalyst was dried in air in mild conditions compared to the catalytic material reduced with H2 (5.3 nm mean size) According to FTIR results, strong metal-support interaction was evidenced between platinum nanoparticles and inner walls of SiO2 nanotubes. In order to observe the effect of Pt nanoparticle morphology on catalytic behavior, the activity of platinum-modified SiO2 tubes (1 wt% Pt/SiO2) for the oxidation of formic acid to CO2 was investigated in the 20–75 °C temperature range. The catalytic activity–morphology relationship of Pt/SiO2 nanotubes was studied and the results were explained in light of experimental results. The catalytic experiments revealed for the first time that SiO2 nanotubes with highly permeable walls behave as efficient membrane-type microreactors for the oxidation of formic acid to CO2. This type of morphological-dependent catalysis may prove to be an efficient tool in near future for the abatement of pollutants in liquid phase.

Characteristics of Nonequilibrium Plasma Flow and Its Sterilization Efficacy in a Tube at Atmospheric Pressure

A nonequilibrium plasma flow produced uniformly in a tube was developed in this paper. The plasma was generated in polyvinyl chloride tube, 3 mm in inner diameter and 100 mm in length, between a wire electrode, 0.2 mm in diameter, and a grounded flat electrode located at the bottom of the tube. We investigated the spectrum, temperature, and ozone concentration of this plasma flow and its sterilization efficacy against Geobacillus stearothermophilus. The temperature in the tube showed uniformity along the wire electrode and increases as applied voltage was increased. With a wire electrode temperature of 337 K at a peak-to-peak applied voltage of 10 kVpp in the sine wave and a frequency of 6 kHz, sterilization of 105 cells was obtained. This result suggests the potential of the application of plasma flow rather than ethylene oxide for sterilization of the inner wall of tubes, such as catheters and artificial blood vessels.