Three-layer Tube Research Articles

A Spectral Method Algorithm for Modeling the Dispersion of Non-Axisymmetric Modes in Fluid-Filled Elastic Tubes

In order to design a low-noise water-filled pipeline system, it is necessary to obtain knowledge of the dispersion characteristics of axial propagation modes in different water-filled elastic tubes. In this work, an algorithm is developed based on the spectral method, which has previously been used to solve the dispersion of axisymmetric modes in cylindrical structures but has not yet been applied to non-axisymmetric modes. The algorithm can obtain the dispersion characteristics, modal displacement, and stress distribution of axial propagation modes in a fluid-filled elastic multi-layer tube. The algorithm behaves well both at low and ultrasonic frequencies, and it is suitable for any tube dimensions, wall thickness and layers. The results of a water-filled PMMA tube obtained using the spectral method algorithm were verified using a COMSOL simulation, while the dispersion curves of the same tube from the literature were found to be missing some low-order modes. In addition, the dispersion curves of a water-filled three-layer tube are given. The spectral method algorithm has the advantages of fast calculation speed, less computational resources consumed, accurate results, and no modal omission.

Solar power tower plants with Bimetallic receiver tubes: A thermomechanical study of two- and three-layer composite tubes configurations

The present study numerically investigated the use of bimetallic tubes for concentrating solar energy applications. Specifically, a billboard receiver employing supercritical carbon dioxide (sCO2) as the heat transfer fluid is considered, with tubes made of stainless steel 316 and GRCop-84. Two- and three-layer tube configurations are compared, exploring the impact of more thermally conductive layer thickness and placement on temperature and stress fields. The findings demonstrate that the use of bimetallic tubes can effectively reduce temperature and stress in the receiver tubes. In light of the results, it can be concluded that the higher thermal conductivity of GRCop-84 leads to a more uniform temperature distribution, resulting in lower temperature peaks on the outer tube surface, and reduced maximum stresses. Furthermore, it has been found that the incident heat flux necessary to achieve the same temperature increment of sCO2 inside the panel is 1.7% lower in a two-layer tube configuration where GRCop-84 is placed in the outer layer. Besides, the stress in the 316 layer can be reduced up to 53.2% with the cited configuration. Nevertheless, it is observed that it is more beneficial to tube performance to place the more conductive layer inside, since it reduces stress in the GRCop-84 layer, and its compressive stress and corrosion-resistant properties help to avoid the risk of stress-corrosion-cracking. In a three-layer composite tube configuration, placing the more thermally conductive GRCop-84 layer close to the outer tube wall decreases the maximum temperature while increasing stress. The opposite effect is achieved by placing the more conductive layer closer to the inner tube wall. Overall, the results demonstrate the potential benefits of using bimetallic tubes for solar energy applications, when the layers have similar thicknesses, since their use can enhance the thermomechanical performance of conventional tubes made with one layer of 316 stainless steel. This fact has important implications for the design of efficient and reliable solar thermal systems.

Bioactive and Elastic Emulsion Electrospun DegraPol Tubes Delivering IGF-1 for Tendon Rupture Repair.

Tendon injuries can result in two major drawbacks. Adhesions to the surrounding tissue may limit the range of motion, while fibrovascular scar formation can lead to poor biomechanical outcomes. Prosthetic devices may help to mitigate those problems. Emulsion electrospinning was used to develop a novel three-layer tube based on the polymer DegraPol (DP), with incorporated insulin-like growth factor-1 (IGF-1) in the middle layer. Scanning electron microscopy was utilized to assess the fiber diameter in IGF-1 containing pure DP meshes. Further characterization was performed with Fourier Transformed Infrared Spectroscopy, Differential Scanning Calorimetry, and water contact angle, as well as through the assessment of mechanical properties and release kinetics from ELISA, and the bioactivity of IGF-1 by qPCR of collagen I, ki67, and tenomodulin in rabbit Achilles tenocytes. The IGF-1-containing tubes exhibited a sustained release of the growth factor up to 4 days and showed bioactivity by significantly upregulated ki67 and tenomodulin gene expression. Moreover, they proved to be mechanically superior to pure DP tubes (significantly higher fracture strain, failure stress, and elastic modulus). The novel three-layer tubes intended to be applied over conventionally sutured tendons after a rupture may help accelerate the healing process. The release of IGF-1 stimulates proliferation and matrix synthesis of cells at the repair site. In addition, adhesion formation to surrounding tissue can be reduced due to the physical barrier.

Design optimization of lightweight structures inspired by the rostrum in Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae)

The rostrum of Cyrtotrachelus buqueti Guer has excellent mechanical properties, such as high-specific strength and high-specific stiffness, and it is an example of successful evolution in nature. In this paper, based on the biological structural characteristics of the rostrum, bionic variable-density lightweight structures of varying layer number are designed, and their mechanical properties are analyzed under different helix angles. The results show that when the helix angle is greater than or equal to 40°, the maximum compressive load borne by the three-layer tube is 30.75 N, which is 1.89 times that of the single-layer tube. Through calculation, at a helix angle of 15°, the torsion lightweight coefficient of the single-layer, double-layer, and three-layer structures is 0.99 ± 0.03 N·M g−1, 1.75 ± 0.05 N·M g−1, and 2.32 ± 0.06 N·M g−1, respectively, where that of the three-layer structure was approximately 2.34 times that of the single-layer structure. Further calculations show that the bending lightweight factor of the single-layer, double-layer, and three-layer tubes is 17.89 ± 0.20 N g−1, 33.16 ± 0.45 N g−1, 41.33 ± 0.55 N g−1, respectively, where that of the three-layer tube is 2.31 times that of the single-layer tube. In addition, this paper also investigates the cushioning energy absorption characteristics of the bionic lightweight tubes by using an impact testing machine. The results show that under the same conditions, as the number of layers of the lightweight tube increases, the buffering energy absorption also increases. The total energy absorption and specific energy absorption of the three-layer lightweight tube are approximately 10 times those of the single-layer tube. Finally, a response surface-based optimization method is proposed to optimize the bionic structures under a combined compression-torsion load. The results lay the foundation for the lightweight design of thin-walled tube structures.

Analytical Study on the Resonance Frequency of Tunable Surface-Wave-Excited Plasma Antennas

In this article, an accurate analytical model for the calculation of the resonant length of a surface-wave-excited plasma antenna based on the distribution of the plasma density along the column is presented. In the proposed method, the propagation and attenuation constants for a surface-wave-excited plasma column are derived by solving the surface wave propagation problem on a three-layer tube, and as a result, the distribution of the plasma density along the column is investigated. Specifically, it is shown that a plasma column acts as a slow wave medium. Therefore, the resonant length of a plasma antenna is less than the resonant length of its metallic counterpart. For the experimental validation of the presented model, an efficient coupling structure for feeding the excitation wave to the plasma antenna is proposed that allows frequency tunability and reconfigurability of the antenna. A prototype of the proposed structure has been designed and fabricated. Good agreement between the analytical, numerical, and measurement results validates the proposed model.

Influence of internal stresses on stability of multilayer micropolar tubes

Within the nonlinear Cosserat continuum, the stability of a compressed multilayer tube under internal and external hydrostatic pressures is studied. The tube is formed by attaching to each other N hollow cylinders that have been subjected to preliminary deformations of axial extension-compression and contains internal stresses. For the model of a physically linear micropolar material, the system of linearized equilibrium equations is derived, which describes the behavior of a multilayer cylindrical tube in a perturbed state. Using a special substitution, the stability analysis is reduced to solving a linear homogeneous boundary-value problem for a system of 6N ordinary differential equations. In the case of a three-layer tube made of dense polyurethane foam, the stability regions were constructed in the planes of loading parameters (the relative axial compression and the relative external or internal pressure) for different preliminary deformations of inner and outer layers (coatings). According to the results obtained, the preliminary extension of both the outer and inner coatings generally stabilizes the considered deformations of the three-layer tube, while the effect of their preliminary compression is negative. It should be noted here that the pre-stressed outer coating has a more significant influence on the tube stability than the pre-stressed inner coating. In addition, the described effects of preliminary deformations are more pronounced for tubes with thicker coatings.

Analysis of Heat Exchange Performance of Heat Exchange Tubes of Evaporative Heat Exchanger Based on Fluent

In order to study the influence of the heat exchange tubes length of the evaporative heat exchanger on the heat exchange performance of the organic Rankine cycle technology (ORC) in automobile exhaust heat recovery, four kinds of three-layer tube heat exchange tube models with the length of 500mm, 800mm, 1100mm and 1400mm are designed by DM modeling software, and they are simplified into a quarter calculation domain model. The simulation calculations of the coupling heat exchange of four different lengths of heat exchange tubes are performed by using the Couple algorithm of Fluent fluid simulation software and the κ-ε model. Through the simulation calculation of the heat exchange of the four three-layer heat exchange tubes, it can be seen that the temperature in the three-layer heat exchange tubes changes along the Z axis direction. The heat exchange performance of different lengths of heat exchange tubes can be obtained by analyzing the temperature cloud diagrams of the XY plane at both ends of the heat exchange tubes and the temperature change curve along the Z axis direction. The heat exchange simulation analysis results of the four three-layer heat exchange tubes show that under the set parameter model, only the inlet and outlet boundary temperature is considered, and the three-layer heat exchange tube with a length of 1400mm has better heat exchange performance.

Drug carrier three-layer nanofibrous tube for vascular graft engineering

Currently available synthetic grafts demonstrate moderate success at the macrovascular level, but there are still challenges at small vascular scale (inner diameter of less than 6 mm). In this paper, silk fibroin (SF)/polyurethane (PU)/SF three-layer drug carrier nanofibrous tubes were developed for blood vessel repair with several advantages over existing designs. Our design consisted of a bionic three-layer microtube that was synthesized from the drug carrier SF and oligomeric proanthocyanidin nanofibers as the inner layer, PU nanofibers as the middle layer, and SF nanofibers as the outer layer. The results suggested that these three-layer tubes are attractive biocompatible materials for use as vascular grafts.

Proving the viability of manufacturing of multi-layer steel/vanadium alloy/steel composite tubes by numerical simulations and experiment

Vanadium alloys are promising structural materials for fuel cladding tubes for fast-neutron reactors. However, high solubility of oxygen and nitrogen in vanadium alloys at operating temperatures of 700 °C limits their application. In this work, we present a novel composite structure consisting of vanadium alloy V-4Ti-4Cr (provides high long-term strength of the material) and stainless steel Fe-0.2C-13Cr (as a corrosion resistant protective layer). It is produced by co-extrusion of these materials forming a three-layered tube. Finite element simulations were utilised to explore the influence of the various co-extrusion parameters on manufacturability of multi-layered tubes. Experimental verification of the numerical modelling was performed using co-extrusion with the process parameters suggested by the numerical simulations. Scanning electron microscopy and microhardness measurements revealed a defect-free diffusion layer at the interfaces between both materials indicating a good quality bonding for these co-extrusion conditions.

Heat transfer and pressure drop characteristics of two-phase propane flow in shell side of LNG spiral wound heat exchanger

For designing LNG spiral wound heat exchangers (SWHE), the boiling heat transfer and pressure drop characteristics of two-phase hydrocarbon refrigerant flowing downward at shell side should be known. In this study, an explosion-proof experimental rig was established for observing flow patterns and measuring heat transfer coefficients and pressure drops. The test section contained three-layer tube bundles to emulate the actual structure and flow conditions of a SWHE. Propane as one main component of shell-side refrigerant was used as the tested fluid. Through the experimental analysis, the influence laws of vapor quality, mass flux on flow pattern, heat transfer and pressure drop of propane are obtained. As the vapour quality increases, the heat transfer coefficient in the shell side of LNG SWHE initially increases and then decreases, representing a maximum at a vapour quality of 0.8~0.9. The flow patterns in the shell side of LNG SWHE present to be the column falling film flow, droplet falling film flow, shear flow, mist flow and gas flow as the vapour quality increases from 0.2 to 1.0.

Experimental investigation on downward flow boiling heat transfer characteristics of propane in shell side of LNG spiral wound heat exchanger

For designing LNG spiral wound heat exchangers (SWHE), the boiling heat transfer mechanism of two-phase hydrocarbon refrigerant flowing downward in shell side should be known. In this study, an explosion-proof experimental rig was established for measuring heat transfer coefficients (HTC) and observing flow patterns. The test section contains three-layer tube bundles to emulate the actual structure and flow conditions of an SWHE. Propane as one main component of shell-side refrigerant is used as the tested fluid. The experimental conditions cover heat fluxes of 4~10 kW⋅m−2, mass fluxes of 40~80 kg (m2⋅s)−1 and vapor qualities of 0.2~1.0. The results indicate that HTC initially increases and then decreases with the increment of vapor quality, representing a maximum at a vapor quality of 0.8~0.9; the effect of heat flux on HTC increases with the increment of heat flux. A correlation of HTC was developed covering 98% of the experimental data within a deviation of ±20%.

Analytical prediction of forming pressure for three-layered tube hydroforming

Tube hydroforming is a special manufacturing process that uses high-pressure fluid to flow the material into a die cavity. This process has been used mostly in automobile and aerospace industries. Compared to the conventional metal forming processes, it has the advantages of weight reduction, less tooling cost, fewer secondary operations, and improved structural strength and stiffness. In special working environments, multi-layered tubes with combined material properties, high strength, and corrosion resistance are required to satisfy conflicting requirements. In this study, an analytical model for predicting the forming pressure range of a three-layered tube is developed and experimentally verified. Fundamental theories for calculation of the pressure for the inner, center, and outer tubes are proposed. Forming pressures are obtained from equilibrium equations for the action and reaction forces on the contacting walls of the tubes. In order to validate the proposed model, free bulge experiments are performed with stainless steel/aluminum alloy/copper alloy and stainless steel/carbon steel/copper alloy three-layered tubes. The measured forming pressures are in reasonable agreement with those obtained from the analytical model.

Characteristics of Composite Silicon Carbide Fuel Cladding after Irradiation under Simulated PWR Conditions

Silicon carbide possesses a high melting point, low chemical activity, no appreciable creep at high temperatures, and a low neutron absorption cross section, making it an attractive material to investigate for use as fuel cladding in light water reactors. The cladding design investigated herein consists of three layers: an inner monolith of SiC, a central composite layer of SiC fibers infiltrated with SiC, and an outer SiC coating to protect against corrosion. The inner monolith provides strength and hermeticity for the tube, and the composite layer adds strength to the monolith while providing a pseudo-ductile failure mode in the hoop direction. The tube may be sealed by bonding SiC end caps to the SiC tube. A number of samples were irradiated in a test loop simulating pressurized water reactor coolant and neutronic conditions at the Massachusetts Institute of Technology research reactor. Postirradiation hoop stress testing via internal pressurization revealed 10% to 60% strength reduction due to physical properties mismatches between the three layers and corrosion. Weight loss measurements indicated that some irradiation-assisted corrosion occurred. Scanning electron microscope analysis allowed determination of the fracture mechanisms for specimens ruptured during hoop testing. The thermal diffusivities of the as-fabricated three-layer tube samples were measured to be roughly three times lower than those of the as-fabricated monolith layer. With irradiation, the thermal diffusivities decreased by factors of 14 and 8 for the monolith and three-layered samples, respectively. This change may be attributed to radiation damage and the formation of a silica layer on the sample surface. Anisotropic swelling of the bonded α-SiC blocks was sufficient to fail five of the six bond test specimens after a 1.5-month irradiation. Two of each of the calcium aluminate and Ti foil bonded samples failed. One of two TiC/SiC bond samples survived.

Discrete layer hydroforming of three-layered tubes

Discrete layer forming proposed in this study is a hydroforming process which can selectively deform the outer tube to a desired shape without any deformation of the inner tube by piercing small holes in the inner tube. A three-layered tube is assembled from inner, middle, and outer tubes, from either similar or dissimilar materials, and deforms simultaneously when internal pressure and axial feed are applied to the tube. In special working environments, multi-layered tubes with combined material properties, high strength, and corrosion resistance are required to satisfy conflicting performance requirements. The feasibility of proposed discrete layer forming process of three-layered tube was evaluated by a tube hydroforming experiment and process analysis was performed. An optimal loading path to prevent wrinkling around holes was developed by an analytical model and was experimentally verified. The results show that the proposed discrete layer forming process can be successfully applicable to hollow forming of non-axisymmetric multilayered tubes for structural purposes.

Stress Analysis and Structural Optimization of a Three-Layer Composite Cladding Tube Under Thermo-Mechanical Loads

A general solution for the stress and strain fields in a three-layer composite tube subjected to internal and external pressures and temperature changes is first derived using thermo-elasticity. The material in each layer is treated as orthotropic, and the composite tube is regarded to be in a generalized plane strain state. A three-layer ZRY4-SiCf/SiC-SiC composite cladding tube under a combined pressure and thermal loading is then analyzed and optimized by applying the general solution. The effects of temperature changes, applied pressures, and layer thickness on the mechanical behavior of the tube are quantitatively studied. The von Mises’ failure criterion for isotropic materials and the Tsai-Wu’s failure theory for composites are used, respectively, to predict the failure behavior of the monolithic ZRY4 (i.e., Zircaloy-4) inner layer and SiC outer layer and the composite SiCf/SiC core layer of the three-layer tube. The numerical results reveal that the maximum radial and circumferential stresses in each layer always occur on the bonding surfaces. By adjusting the thickness of each layer, the effective stress in the three-layer cladding tube under the prescribed thermal-mechanical loading can be changed, thereby making it possible to optimally design the cladding tube.

Theoretical investigation of TiB2 nanotubes

We investigated the energetic and electronic properties of zig-zag titanium diboride (TiB2) nanotubes through ab initio density functional theory. It is determined that an isolated (6,0) bilayered TiB2 nanotube has a semiconductor character, with an energy gap of 1.32eV. The strain energy to form the (6,0) TiB2 nanotube is calculated to be 0.26eV per unit formula. The electronic density of states of a three-layer tube ((6,0) TiB2+(12,0) B tube) shows a metallic behavior for this system, which is consistent with previous calculations on similar hypothetical nanotubes.