Three-dimensional Tube Research Articles

Experimental investigation of vapor condensation of R-600a over horizontal three-dimensional integral-fin tubes

In this study, condensation heat transfer coefficients (HTCs) of refrigerant R-600a (iso-butane) over horizontal 3-Dimensional integral-fin tubes were determined at vapor temperature of 312 K with wall sub-cooling temperatures of 3–9 K under heat flux of 33–87 kW/m2. Further, our experimental results were validated by comparing them with modified Wilson plot technique. Modified Wilson plot technique underpredicts experimental heat flux by 15–35%.

Numerical investigation of nanofluid flow characteristics and heat transfer inside a twisted tube with elliptic cross section

In the present study, turbulent flow and heat transfer inside a three-dimensional tube with elliptic and circular cross sections are simulated using finite volume method. The main aim of this study is to investigate the effects of ellipse aspect ratio and twisting of the tube wall on the flow characteristics and heat transfer. According to the obtained results, by converting the cross section from circular to elliptical and reducing the aspect ratio of elliptic tube with smooth wall, the friction factor and heat transfer increase. Investigating on the effect of wall twisting shows that, due to generation of secondary flow, the heat transfer and friction factor increase. By reducing the twist pitch, the generated vortices get merged into a large vortex and affect the flow across the whole cross section, causing the mixing to improve and heat transfer to increase. According to the obtained results, in the elliptical tube with an aspect ratio of 1.65, at twist pitches of 0.4 and 0.2, the heat transfer increases compared to a smooth tube with a similar cross section by 5% and 20%, respectively; and by a sudden reduction of twist pitch from 0.2 to 0.1 along the path, the heat transfer improves up to 30%. The effect of addition of multi-wall carbon nanotube nanoparticles to the base fluid inside the twisted elliptical tube with an aspect ratio of 1.65 on the heat transfer and flow characteristics is also analyzed, 28–32% in heat transfer for Reynolds number of 4000 and 16,000. According to the obtained results, the performance evaluation criterion (PEC) of nanofluid with low volume fraction and at lower Reynolds numbers is less than 1; however, for the flow of nanofluid with a volume fraction of 0.03, the heat transfer enhancement prevails over the increase in the pressure drop and the PEC is more than 1.

Epigallocatechin-3-Gallate Suppresses Vasculogenic Mimicry through Inhibiting the Twist/VE-Cadherin/AKT Pathway in Human Prostate Cancer PC-3 Cells.

Vasculogenic mimicry (VM) is the alternative process of forming vessel-like networks by aggressive tumor cells, and it has an important role in tumor survival, growth, and metastasis. Epigallocatechin-3-gallate (EGCG) is well known to have diverse bioactivities including anti-cancer effects. However, the efficacy of EGCG on VM is elusive. In this study, we explored whether and how EGCG affects VM in human prostate cancer (PCa) PC-3 cells. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Invasive and VM formation abilities were assessed by an invasion assay and a three-dimensional (3D) culture VM tube formation assay, respectively. Western blots were carried out. An immunofluorescence assay was performed to detect nuclear twist expression. EGCG effectively inhibited the invasive ability, as well as tubular channel formation, without affecting cell viability. EGCG significantly downregulated the expression of vascular endothelial cadherin (VE-cadherin) and its transcription factor, twist, N-cadherin, vimentin, phosphor-AKT, and AKT, but not phospho-erythropoietin-producing hepatocellular receptor A2 (EphA2) and EphA2. In addition, EGCG diminished the nuclear localization of twist. Treatment with SC79, an AKT activator, effectively rescued EGCG-inhibited VM formation. These results demonstrated for the first time that EGCG causes marked suppression of VM through inhibiting the twist/VE-cadherin/AKT pathway in human PCa PC-3 cells.

Design and calibration of a three-dimensional localization system for automatic measurement of long and thin tube based on camera and laser displacement sensor

An integrated system consisting of robot and laser scanner is considered as a promising alternative measurement device for three-dimensional tube which is long and thin. A key to achieving automatic measurement is to locate tube accurately and robustly, which is precondition for scanning path planning. Thus, a novel three-dimensional localization system consisting of camera and laser displacement senor is proposed. When fixed on robot, the camera can search tube quickly in large view and the laser displacement sensor obtains depth information of key points. Measurement principles are presented firstly, including four main steps: camera shooting, key points extraction, laser displacement sensor shooting, and coordinate calculation. Then, the location error influenced by parameters of camera model and laser displacement sensor is analyzed and illustrated by a specific camera and laser displacement sensor. Furthermore, a scan strategy is proposed for quite thin tube localization. Location error caused by perspective is also analyzed and a compensation method is proposed for decreasing the error. Additionally, a sensor transformation calibration method is presented for identifying the relationship between camera and laser displacement sensor, which is verified with high accuracy by calibration experiments. A contrast experiment of a cylinder bar localization shows that the maximum location error of the camera and laser displacement sensor is no more than 3.5 mm, which is only one-eighth of that of Kinect sensor. The mean and maximum location errors are within 2 mm and 3 mm when locating a car brake and fuel tube with about 1300 mm long, indicating high accuracy and good robustness of designed localization system.

Morphological Transformation between Flat and Tube Structures by Coordinated Motions of Soft Pneumatic Microactuators

Microactuators are the most distinctive and challenging microdevices among micro electromechanical systems (MEMS) relative to microsensors or electronic circuits. Soft and flexible microactuators have been achieved by introducing polymers as structural materials in addition to conventional materials. Expanding the application of MEMS to the biomedical field requires particular features, such as softness and small devices. It is important to address small and fragile biological objects while satisfying the demand for minimally invasive medicine. Both MEMS and biomedical applications require three-dimensional microstructures for higher-order functions. In general, microactuators are limited to simple motions such as bending. Our group has developed an openable artificial small intestinal tract system. An array of pneumatic balloon actuators (PBAs) transforms a flat structure into a tube structure representing the small intestine. Coordination of the bending motions of the PBAs enables the formation of a three-dimensional tube structure. Each PBA is 400 μm × 1800 μm × 100 μm. The diameter of the tube structure is 1 mm. Additional higher-order functions of the artificial small intestine, such as peristaltic motion, are currently of interest for us. This paper describes the morphological transformation of a soft microstructure and further potential possibilities of coordinated motions of soft microactuators.

Temperature rise caused by adiabatic shear failure in 3D braided composite tube subjected to axial impact compression

Previous investigation on the crashworthiness of braided composite tubes did not take the relationship between adiabatic shear failure and temperature rise into account during dynamic loading. In this study, transient temperature rise caused by adiabatic effect was detected and captured for the three-dimensional braided carbon/epoxy composite specimens during axial impact compression under 600–800/s. A mesostructure model was established based on three-dimensional braided tube architecture to numerically characterize the mechanical and thermal response in material. Based on the results, non-uniform temperature distribution shows good correlation with adiabatic shear failure in the material. Key scientific issues are discovered including the position, morphology, time sequence, and response process of the temperature rise. The catastrophic shear behavior with accelerated temperature rise occurs after the peak force and accompanies the progressive failure process. Nodes having room temperature in the adiabatic shear zone indicates that some positions in plastic zone may still behave as elastic state. There exists different plastic slip distances due to shear instability in the path along or crossing the adiabatic shear band. Through this investigation, the model considering the adiabatic effect was able to show the dynamic shear mechanism involving the fracture position, morphology, and progressive thermo-mechanical response of the temperature rise, which cannot be revealed by experimental testing.

Effects of wavy wall and Y-shaped fins on solidification of PCM with dispersion of Al2O3 nanoparticle

In current modeling, solidification process within a three-dimensional triplex tube was numerically studied. In two sides, the cold water flow is used while the middle tube contains RT82. The purpose of the current article is investigating the impacts of using nanoparticles, fin, and the combination of both of them on thermal characteristics during solidification in an energy storage unit. Also, the amount of stored energy has been investigated over time, and the influences of temperature and water velocity were scrutinized. The results revealed some substantial improvements in the solidification rate by adding fins or nanoparticles. It was indicated that using a combination of these two heat transfer enhancement methods presents a better enhancement compared to when either of these two methods is employed alone.

Forced convection condensation of R134a in three-dimensional conical pin fin tubes

This paper investigates the forced convection condensation heat transfer performance of R134a in circular tubes with three-dimensional conical pin fin structures. Five conical pin fin tubes of different circumferential fin pitch (pc) and longitudinal fin pitch (pl) were fabricated by Selective Laser Melting (SLM) with the aim of enhancing the internal forced convection condensation of R134a. Experiments were performed to characterize the condensation heat transfer coefficients (href) and pressure drops (ΔP) across these enhanced tubes. These experiments were conducted at the refrigerant mass fluxes (mref) of 50 kg/m2·s to 200 kg/m2·s, average vapor qualities (xave) from 0.2 to 0.8 and saturation pressure (Psat) of 13.4 bar. The effects of xave, mref, pc and pl on href and ΔP were determined and the results were compared against a commercial Al tube, a plain tube fabricated by SLM and two SLM fabricated enhanced tubes with dome-shaped fins. It was found that href of the conical pin fin tubes increases with increasing xave and mref and these values are also significantly higher than those of the plain tubes. Both pl and pc were found to significantly affect the href values of the conical pin fin tubes whereas the ΔP values were affected only by the change in pc. An efficiency index (η1) is defined to evaluate the thermal-hydraulic performances of the enhanced tubes. The experimental results show that all the conical pin fin tubes demonstrated higher η1 than the dome-shaped fin tubes. Based on the boundary layer approach, a semi-empirical model is developed to predict the Nusselt numbers of the conical pin fin tubes. Reasonably accurate predictions were achieved with an overall mean absolute error (MAE) of 10.5%.

Utilizing modules of different functions to construct a Janus-type membrane and derivative 3D Janus-type tube displaying synchronous trifunction of conductive aeolotropism, magnetism and luminescence

The microstructures and macrostructures play a crucial role in the properties and applications of multifunctional materials. Herein, microscopic partition and macroscopic partition are combined by devising and preparing different modules that can be elaborately devised to possess specific performances. A two-dimensional (2D) 3-module Janus-type membrane multifunctionalized by conductive aeolotropism, magnetism and luminescence (defined as 3M-CML Janus-type membrane) is constructed via electro-spinning. The modular structure of 3M-CML Janus-type membrane is obtained by devising and constructing three different modules, including luminescence module (denoted as L module), conductive aeolotropism-luminescence module (marked as C-L module) and magnetism-luminescence module (named as M-L module). The results prove that almost no mutual detrimental influences exist among different modules owing to the macroscopic modular structure and Janus-type structure, which effectively avoids the negative interactions among different materials. Tb(BA)3phen/PVP nanofiber, [PMMA/Eu(BA)3phen]//[PMMA/PANI] Janus-type nanoribbon and [PMMA/Tb(BA)3phen]//[PMMA/Fe3O4] Janus-type nanoribbon are, respectively, selected as building units of the three modules, which further prevents the negative interactions among different materials and improves the versatility of 3M-CML Janus-type membrane. The luminescence, adjustable conductive aeolotropism and variable magnetism of 3M-CML Janus-type membrane are systematically discussed. Meanwhile, novel flexible four types of brand-new three-dimensional (3D) Janus-type tubes are obtained by rolling modularly devised 2D 3M-CML Janus-type membrane with different rolling schemes. As derivatives of the 2D 3M-CML Janus-type membranes, macroscopic 3D Janus-types tubes exhibit similar performances to 2D 3M-CML Janus-type membranes. The 2D Janus-type membrane and 3D Janus-type tube will have momentous applications in flexible electronics and nanodevices in the future.

Numerical simulation of sulfuric acid vapor condensation characteristics on an external three-dimensional finned tube surface

Three-dimensional external finned tube heat exchanger has been widely applied in waste heat recovery system. However, the current researches mainly focus on its fluid flow and heat transfer characteristics. The condensation of sulfuric acid and water vapors on heat exchanger surface, which can cause severe low temperature corrosion and reduce equipment efficiency, has rarely been reported. In this study, a heat and mass transfer model for flue gas on finned tube surface was developed to investigate the sulfuric acid and water vapor condensation characteristics and their distributions. The effects of flue gas velocity and temperature, acid and water vapor concentrations, and surface temperature were examined. The results show that the distribution of acid solution concentration on finned tube surface mostly depends on the distribution of fin surface temperature. At the windward side (especially near the minimum flow cross section region), both fin surface temperature and condensed acid solution concentration reaches the maximum value. Increasing velocity leads to vapors condensation rate and acid solution concentration increasing. The acid solution concentration decreases with flue gas temperature or tube wall temperature increasing. The present work could provide effective theoretical guidance for anti-corrosion design of finned tube heat exchanger.

Three-Dimensional Double-Walled Ultrathin Graphite Tube Conductive Scaffold with Encapsulated Germanium Nanoparticles as a High-Areal-Capacity and Cycle-Stable Anode for Lithium-Ion Batteries.

The demand for lithium-ion batteries with both high power and high-energy density has attracted widespread attention as energy-storage devices for the increasing demand of consumer electronics, electric vehicles, and grid-scale storage. However, the fabrication of an advanced electrode architecture with high areal capacity, excellent cycling stability, and superior rate performance remains a long-term challenge in the development of advanced electrochemical energy-storage devices. Herein, we design an effective and general strategy to spontaneously encapsulate Ge nanoparticles into a three-dimensional double hydrophilic N-doped ultrathin graphite/void/hydrophobic ultrathin graphite tube network (Ge@3D-DHGT) with control over the position for large specific capacity (1338 mA h g-1), high rate performance (752 mA h g-1 at 40 C), and superior cycling stability (up to 1000 cycles). Toward the practical application, the as-prepared Ge@3D-DHGT electrode showed a large areal capacity (10 mA h cm-2 under 8 mA cm-2), which provides a highly promising anode with both high capacity and high rate performance. Importantly, this work provides an approach to fabricate high-areal-capacity anodes with long cycling stability and rapid charge-discharge properties with practical applications in advanced rechargeable batteries.

Experimental studies on the compound thermo-hydraulic characteristics in a 3D inner finned tube with porous copper fiber inserts

A novel easy-to-manufacture porous copper fiber sintered cylinder insert (PCFSCI) is designed to enhance the convective heat transfer performance in a three-dimensional inner finned tube (3D-IFT). The compound heat transfer enhancement of the PCFSCI and 3D inner fins is investigated at the Reynolds number ranging from 3921 to 14,290. The results show that the combination of PCFSCI and 3D-IFT creates a synergistic effect and a maximum performance evaluation criterion (PEC) value of 2.29. Moreover, the effect of porosity, diameter and spacing of the PCFSCI on heat transfer performance is investigated. The results show that the Nusselt number and friction factor increase with the decrease of porosity. The PCFSCI with a diameter of 8 mm presents a better PEC than PCFSCI with diameters of 12 mm and 10 mm. The spacing has a slight effect on the PEC, but a great influence on the Nusselt number and friction factor. These phenomena can be attributed to the fluid mixing between the core flow and the flow in the annular region, as well as the local vortexes and the changing of velocity gradient produced in the annular region.

Influence of geometric parameters on the gas-side heat transfer and pressure drop characteristics of three-dimensional finned tube

Three-dimensional fin tubes have been used in efficient compact heat exchangers for many years. To further improve the heat transfer efficiency, the Taguchi method is used to study the influence of the structural parameters of three-dimensional finned tubes on the heat transfer and pressure drop characteristics in the air cross-flow. The effects of the fin height, fin width, axial fin pitch and circular fin pitch have been studied, and the contribution ratios of each structural parameter on the thermo-hydraulic performance are given. The results show that the influence of the fin height on the heat transfer and flow resistance is the largest, which should be considered as the preferential factor in the design of three-dimensional finned tubes. The effects of multi-parameters on heat transfer and flow resistance are analyzed. Then, empirical correlations are developed for the Nusselt number and friction factor in the experimental ranges. Finally, the performance evaluation criterion of three-dimensional finned tube is revealed to be 2.7–2.9 times greater than that of the smooth tube. Meanwhile, the order of the four structural parametric effectiveness for the performance evaluation criterion is obtained as fin height > axial fin pitch > circular fin pitch > fin width.

Potential of gear-ring turbulator in three-dimensional heat exchanger tube from second law of thermodynamic viewpoint

Purpose This paper aims to use the second law of thermodynamic to evaluate the potential of gear-ring turbulator in a three-dimensional heat exchanger tube. Accordingly, a numerical simulation is performed to obtain the irreversibilities in a three-dimensional heat exchanger tube equipped with some gear-ring turbulators for turbulence regime. Design/methodology/approach A numerical simulation is performed to obtain the irreversibilities in a three-dimensional heat exchanger tube equipped with some gear-ring turbulators for turbulence regime. The analysis is carried out based on shear stress transport (SST) k-ω turbulent model. The influences of different parameters containing tooth number, free-space length ratios and Reynolds number on frictional and thermal irreversibilities and Bejan number are discussed. Findings The results indicated that the thermal irreversibility reduces by decreasing the tooth number. For example, the thermal entropy generation decreases about 25.81 per cent by decreasing the tooth number in the range of 24 to 0 at Re = 6,000. Moreover, the frictional entropy generation decreases by increasing the tooth number as the gear with more tooth number causes a lower flow disturbance. Originality/value The present study arranged a numerical work to study the potential of a gear-ring turbulator in a heat exchanger tube from first and second laws of thermodynamic viewpoint. The turbulent flow is considered for this problem. The literature review showed that the usage of a gear-ring turbulator in a heat exchanger tube is not investigated from the second law of thermodynamic viewpoint by previous studies. As a result, the influences of different parameters containing tooth number, free-space length ratios and Reynolds number on frictional and thermal irreversibilities and Bejan number are discussed.

Effect of Forming Parameters on Flexible-Bending of Three-Dimensional Tubes

Flexible-bending is an advanced bending method, especially suitable for small batch production of tubes. The shape of forming parts is mainly related to the offset of the bend die instead of the geometry of it. Based on flexible-bending technology, 3D bending of tubes was carried out by finite element method and the effects of primary parameters on the bending results were studied. The analysis results showed that3D continuous bending of tubes can be obtained by flexible-bending process; die offset, offset speed and feeding speed of tube have a great influence on the bending effect. Bending experiments of 3D tube were carried out by flexible-bending equipment and bending radii of the forming part were measured, the results were very close to that of simulations which proved the effectiveness of simulation.

Fabrication of 3D Tubular Hydrogel Materials through On-Site Surface Free Radical Polymerization

Constructing tubular hydrogel materials with desirable structures based on their functional application is a big challenge. Here, we report a simple but effective method to prepare tubular hydrogels with complex geometries by surface radical polymerization, in which an iron wire acts as both catalyst and template for the formation of a gel layer with controllable thickness. The formed hydrogel layer can be easily peeled off from the template after secondary cross-linking to obtain hollow hydrogel tubes which exhibit extraordinary and tunable tensile strength, good elasticity, and pressure-bearing capability. The method can be generalized to construct a series of complex three-dimensional hydrogel tubes with versatile components for building up fluidic channels or biocompatible 3D cell culturing platform for tissue engineering. Such a method is a great advance in the field of hydrogel materials. It is anticipated that this innovation would open up the door for developing functional 3D tubular hydrogel mate...

Numerical simulation of the flow and heat-transfer characteristics of an aligned external three-dimensional rectangular-finned tube bank

Finned-tube heat exchangers are commonly used for air conditioning, refrigeration, and utility boilers to enhance the energy efficiency of heat transfer. Compared with the 2D continuous finned tube, the 3D discrete finned tube heat exchangers have more outstanding performance on enhancement of heat-transfer. Especially, the 3D rectangular fin is believed to have better heat-transfer performance compared with common 3D fins.In this study, the flow and heat-transfer characteristics of an aligned external rectangular-finned tube bank with six rows of tubes were numerically investigated. The performances of an external rectangular-finned tube bank and a smooth tube bank were firstly compared. This was followed by an analysis of the effects of the geometric parameters (transverse tube pitch, longitudinal tube pitch, fin height, fin width, and fin pitch in the axial direction) and the Reynolds number on the flow and heat-transfer characteristics of an aligned external three-dimensional rectangular-finned tube bank.The results indicated that the heat transferability and friction loss of the aligned external three-dimensional rectangular-finned tube bank were higher than those of the smooth tube bank, while the comprehensive performance of external rectangular finned tube bank was not always superior. In addition, increasing the longitudinal tube pitch, fin height and fin width or decreasing the transverse tube pitch and fin pitch in the axial direction caused the heat-transfer capability and flow loss of the external rectangular-finned tube bank to increase, which can provide theoretical guidance for the design of a 3D finned-tube heat exchanger. The correlations of the Nusselt number (Nu) and the friction factor (f) for the six-row tube bank were presented, which can be helpful to engineering applications of heat exchanger for clean gas situations.

Dual blockade of VEGFR1 and VEGFR2 by a novel peptide abrogates VEGF-driven angiogenesis, tumor growth, and metastasis through PI3K/AKT and MAPK/ERK1/2 pathway

BackgroundNeutralization of vascular endothelial growth factor receptor 1 (VEGFR1) and/or VEGFR2 is a widely used means of inhibiting tumor angiogenesis. MethodsBased on the complex X-ray structures of VEGFA/VEGFR1, VEGFA/VEGFR2, and VEGFB/VEGFR1, a peptide (referred to as VGB) was designed to simultaneously bind to VEGFR1 and VEGFR2, and binding, antiangiogenic and antitumor properties of the peptide was investigated in vitro. ResultsVGB bound to both VEGFR1 and VEGFR2 in human umbilical vein endothelial cells (HUVECs) and 4 T1 mammary carcinoma tumor (MCT) cells, and inhibited the proliferation of HUVE, 4 T1 MCT, and U87 glioblastoma cells. Through abrogation of AKT and ERK1/2 phosphorylation, VEGFA-stimulated proliferation, migration, and two- and three-dimensional tube formation in HUVECs were inhibited more potently by VGB than by bevacizumab. In a murine 4 T1 MCT model, VGB strongly inhibited tumor growth without causing weight loss, accompanied by inhibition of AKT and ERK1/2 phosphorylation, a significant decrease in tumor cell proliferation (Ki-67 expression), angiogenesis (CD31 and CD34 expression), an increase in apoptosis index (increased TUNEL staining and p53 expression and decreased Bcl-2 expression), and the suppression of systematic spreading of the tumor (reduced NF-κB and MMP-9 and increased E-cadherin expression). ConclusionThe dual specificity of VGB for VEGFR1 and VEGFR2, through which the PI3K/AKT and MAPK/ERK1/2 signaling pathways can be abrogated and, subsequently, angiogenesis, tumor growth, and metastasis are inhibited. General significanceThis study demonstrated that simultaneous blockade of VEGFR1 and VEGFR2 downstream cascades is an effective means for treatment of various angiogenic disorders, especially cancer.

Local convective condensation heat transfer in horizontal double-layer three-dimensional dimple-grooved tubes

An experimental study on local condensation heat transfer characteristics in two three-dimensional double-layer dimple-grooved tubes (2EHT tubes) and a smooth tube is performed using refrigerant of R410A. The smooth tube has an outer diameter of 12.7 mm and inner diameter of 11.07 mm. The 2EHT tubes have a nominal outer diameter of 12.7 mm and wall thickness of 0.8 mm. The enhanced surface areas of two 2EHT tubes are 1.02 and 1.03 times of the smooth tube, respectively. The present experiments are conducted to measure the local wall temperature when the mass flux ranges from 65 kg/(m2·s) to 210 kg/(m2·s), heat flux ranges from 10 kW/m2 to 35 kW/m2 and vapor quality ranges from 0.9 to 0.1. The saturation temperature is maintained at 40 °C. 248 experimental HTC data points are obtained and compared with six correlations. The results show that the measured local HTCs increase with increasing mass fluxes and decrease with increasing heat fluxes, and that the present correlations have a good predictability with smooth tube but cannot predict the HTC of 2EHT tubes. The proposed condensation correlation for 2EHT tubes is validated, and it predicts all experimental points within an error band of ±30%, and 94.25% of all test points within an error band of ±20%.

Ruled Strips with Asymptotically Diverging Twisting

We consider the Dirichlet Laplacian in a two-dimensional strip composed of segments translated along a straight line with respect to a rotation angle with velocity diverging at infinity. We show that this model exhibits a "raise of dimension" at infinity leading to an essential spectrum determined by an asymptotic three-dimensional tube of annular cross-section. If the cross-section of the asymptotic tube is a disk, we also prove the existence of discrete eigenvalues below the essential spectrum.