Tube Shape Research Articles

Computer simulation of yielding supports under static and short-term dynamic load

Dynamic impacts that became frequent lately cause large human and economic losses, and their prevention methods are not always effective and reasonable. The given research aims at studying the way of enhancing explosion safety of building structures by means of yielding supports. The paper presents results of numerical studies of strength and deformation property of yielding supports in the shape of annular tubes under static and short-term dynamic loading. The degree of influence of yielding supports was assessed taking into account three peculiar stages of deformation: elastic; elasto-plastic; and elasto-plastic with hardening. The methodology for numerical studies performance was described using finite element analysis with program software Ansys Mechanical v17.2. It was established that rigidity of yielding supports influences significantly their stress-strain state. The research determined that with the increase in deformable elements rigidity dependence between load and deformation of the support in elastic and plastic stages have linear character. Significant reduction of the dynamic response and increase in deformation time of yielding supports were observed due to increasing the plastic component. Therefore, it allows assuming on possibility of their application as supporting units in RC beams.

ANALISA PENGARUH BENTUK PIPA KAPILER DAN KECEPATAN PUTAR (RPM) TERHADAP PRODUKTIVITAS MESIN SPINNER PENIRIS MINYAK

Spinner machine has become a secondary requirement in major cities. This is because the air temperature continues to rise each year. Spinner machine has the central point in use they can be used as air-conditioning, food preservatives, and others - others. The impact that often occurs in using of cooling machine is continuously increasing the risk of damage to the cooler. Damage often occurs in the compressor of the cooling machine. The compressor itself is the heart of the cooling system. The cause damage to the compressor is usually due to inhibition of the capillary tube crust. In this study, the writer uses a shape variation of the capillary tube like spirals, triangles, rectangles and evaporator air velocity of 200, 300, and 400 rpm, but with the same diameter capillary tube which is 0,54 mm. Based on the results of research that is conducted the best to form a capillary tube is evaporator spiral with air speed of 300 RPM, it is marked by the largest price of COP 10.5. This is due to compression levels fell to 18.6%, the effectiveness of the cooling machine would rise. Keywords: COP (Coefficient of Performance), effectiveness of the machine, Shape of capillary tube

Effect of a Inclined Tube Shape on the Settling Rate

Effect of a Inclined Tube Shape on the Settling Rate

NUMERICAL SIMULATION OF YIELDING SUPPORTS IN THE SHAPE OF ANNULAR TUBES UNDER STATIC AND SHORT-TERM DYNAMIC LOADING

Occurrence of extreme man-made impacts on buildings and structures has become frequent lately as a consequence of condensed explosives or explosive combustion of gas- vapor or air-fuel mixtures. Such accidents involve large human and economic losses, and their prevention methods are not always effective and reasonable. The given research aims at studying the way of enhancing explosion safety of building structures by means of yielding supports. The paper presents results of numerical studies (finite element, 3D nonlinear) of strength and deformability of yielding supports in the shape of annular tubes under static and short-term dynamic loading. The degree of influence of yielding supports was assessed taking into account three peculiar stages of deformation: elastic; elasto-plastic; elasto-plastic with hardening. The methodology for numerical studies performance was described. It was established that rigidity of yielding supports influences significantly their stress-strain state. The research determined that with increase of deformable elements rigidity dependency between load and deformation of yielding supports in elastic and plastic stages have linear character. Significant reduction of dynamic response and increase of deformation time of yielding supports was observed by increasing the plastic component. Therefore it allows assuming on possibility of their application as supporting units in reinforced concrete constructions

Notes on Kalanchoe rotundifolia (Haw.) Haw. (Crassulaceae) in Southern Africa: The Taxonomy of a Species Complex

Taxonomically, Kalanchoe rotundifolia (Haw.) Haw. (Crassulaceae) is one of the most complex of the southern African representatives of the genus. The expression of its vegetative morphology, especially leaf shape and plant size, is exceedingly variable. The reproductive morphology is more constant in terms of the size and shape of the corolla tube and lobes, as well as in the upper part of the corolla tube and lower part of the corolla lobes invariably becoming twisted at the post-anthesis stage. However, flower colour ranges from a yellow-infused light orange through pinkish-red to scarlet. At present we conclude that treating the species as a variable complex in southern and eastern Africa, as well as Socotra, is taxonomically the most sensible. We provide an amplified description and geographical distribution map for K. rotundifolia, and discuss and illustrate some of the remarkably variable forms. A neotype is designated for the name Kalanchoe integerrima Lange.

Modification of Tracheal Cuff Shape and Continuous Cuff Pressure Control to Prevent Microaspiration in an Ex Vivo Pig Tracheal Two-Lung Model.

Microaspiration of subglottic secretions plays a pivotal role in ventilator-associated pneumonia. Impact of endotracheal tube cuff material and shape on tracheal sealing performance remains debated. The primary objective was to compare the tracheal sealing performance of polyvinyl chloride tapered, cylindrical and spherical cuffs. Secondary objectives were to determine the impact of continuous cuff pressure control on sealing performance and pressure variability. Prospective randomized ex vivo animal study. French research laboratory. Seventy-two ex vivo pig tracheal two-lung blocks. Blocks were randomly intubated with cylindrical (n = 26), tapered (n = 24), or spherical (n = 22) polyvinyl chloride endotracheal tube cuffs. Two milliliter of methylene blue were instilled above the cuff to quantify microaspirations, and lungs were ventilated for 2 hours. Continuous cuff pressure control was implemented in 33 blocks. Cuff pressures were continuously recorded, and after 2 hours, a microaspiration score was calculated. Tapered cuffs improved cuff sealing performance compared with spherical cuffs with or without continuous cuff pressure control. Compared with spherical cuffs, tapered cuffs reduced the microaspiration score without and with continuous pressure control by 65% and 72%, respectively. Continuous cuff pressure control did not impact sealing performance. Tapered cuffs generated higher cuff pressures and increased the time spent with overinflation compared with spherical cuffs (median [interquartile range], 77.9% [0-99.8] vs. 0% [0-0.5]; p = 0.03). Continuous cuff pressure control reduced the variability of tapered and spherical cuffs likewise the time spent with overinflation of tapered and cylindrical cuffs. Polyvinyl chloride tapered cuffs sealing enhanced performance at the cost of an increase in cuff pressure and in time spent with overinflation. Continuous cuff pressure control reduced the variability and normalized cuff pressures without impacting sealing performance.

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

This work tried to identify the influence of dosing vaporized urea solution in a selective catalytic reduction (SCR) system. In the SCR method, optimising the urea evaporation and mixing properties can significantly improve the NOx conversion efficiency in the catalyst. It can also exert a positive effect on the uniformity of NH3 concentration distribution across the catalyst face. The concept of an electrically evaporated urea-dosing system was investigated and it was found that urea pre-heating prior to introduction into the exhaust gas is favourable for enhancing NOx removal under steady-state and transient engine operation. In the urea evaporating system the heating chamber was of a cylindrical tube shape and the urea vapour was introduced into the exhaust by means of a Venturi orifice. The concept urea dosing was only a custom-made solution, but proved to be superior to the regular dosing system operating in the liquid phase.

A review on improving thermal-hydraulic performance of fin-and-tube heat exchangers

Fin-and-tube heat exchangers are one of the most common type of heat exchangers that are normally used in sectors that require small size and light weight but high heat transfer capabilities. Compact fin-and-tube heat exchangers experiences high convective thermal resistance at the air-side due to the thermo-physical properties of air. Thus, the purpose of this paper is to provide an overview of research works that are relevant to improving thermalhydraulic performance at the air-side of fin-and-tube heat exchangers. This paper covers a variety of parameters such as tube parameters like tube arrangement, tube shapes and tube inclination angles; extended surfaces such as different shapes of fins and different parameters of vortex generators like attack angles, shapes and locations. Overall, for most modifications there was increment in heat transfer but accompanied with a pressure drop penalty. However, this varies for different combinations of parameters thus this review is to help understand how every mentioned parameters influences the thermal-hydraulic performance.

Parametric study on fouling mechanism and heat transfer characteristics of tube bundle heat exchangers for reducing fouling considering the deposition and removal mechanisms

Particulate fouling on flue gas heat exchanger surfaces reduces heat transfer efficiency and increases the instability of equipment operation. It is necessary to develop a better understanding of how fouling occurs, aiming to find strategies to predict and reduce it. In this paper, a multiple mean cycle method is proposed based on a comprehensive fouling model considering the deposition and removal mechanisms, combined with the discrete phase model and dynamic mesh method, to predict the fouling morphology. Then the effects of transverse pitch, longitudinal pitch, tube shape and arrangement on fly-ash fouling and heat transfer characteristics are examined. It is found that, for aligned arrangement, the fly-ash particles are mainly deposited at the upwind stagnation region at the first row and whole windward side of the rest rows; for staggered arrangement, the fly-ash particles are deposited at the upwind stagnation region. The multiple mean cycle method can predict the fouling morphology efficiently and keep the characteristic of non-uniform fouling distribution. The fouling mass increases with the increase of relative transverse and longitudinal pitches. The elliptical tube bundle with small relative transverse and longitudinal pitches can obviously reduce the fouling mass especially for the staggered elliptical tube. Compared with the aligned circular tube arrangement, the fouling mass mf is decreased by 81.1% at 10min. In addition, the weaken degree of Nusselt number after fouling ΔNu for the staggered elliptical tube is only about 49.8% of the aligned circular tube arrangement. Consequently, using the staggered elliptical tube contributes to reduce the fly-ash fouling, decrease the soot-blowing frequency and ensure the efficiency, economy and safety of flue gas heat exchangers.

Optimization and debugging of a low-toxic combustion chamber with the use of numerical modeling of intrachamber processes

In recent years, there has been a trend towards an increase in demand for microturbines. The microturbine application area is very wide. These are hybrid power plants for transport and specialized equipment, as well as power plants for providing electricity to homes, towns, businesses. When developing advanced gas turbine units, it is necessary to take into account sufficiently high requirements for economic and operational indicators. To improve the performance of microturbines, it is necessary to optimize and refine the basic elements. In particular, to reduce the emission of harmful substances, it is necessary to develop low-toxic combustion chambers. In this paper, we present the results of optimization and fine-tuning of a low-toxic combustion chamber with the use of numerical modeling of intra-chamber processes. The applied models of flow, combustion, radiation, NOx emission are described. The main parameters of the computational grid built for ¼ of the full-size combustion chamber are given. The boundary conditions necessary for the development of mathematical modeling of the flow and combustion processes are formulated. The results of comparison of the initial and optimized geometry of the combustion chamber in the form of patterns of temperature distribution, velocities, total pressure in the swirler, and the distribution of the mass fraction of nitrogen oxides NOx are presented. According to the results of optimization calculations, it can be concluded that relatively small changes in the size, shape and number of secondary air holes, the shape and dimensions of the flame tube, the diameter of the blade swirler and the shape and size of the nozzles of the gas injector have a significant effect on such indicators of the working process as: form, volume and location of the combustion zone; location and intensity of the mixing zone, which, as a consequence, greatly affects the integral parameters of the combustion chamber.

Manfreda occidentalis (Agavoideae, Asparagaceae) a new species from western Mexico

The genus Manfreda (Asparagaceae) contains 35 species. A species complex includes plants similar to M. gutttata, which are characterized by the protrusion of the ovary into the perigone tube. This feature was found in specimens recently collected in western Mexico. After a morphological analysis, we found that some of the plants differ from the other species in this complex. Hence, we describe a new species named M. occidentalis morphologically similar to M. planifolia but can be distinguished from it by the oblong-ovoid corm, channeled leaves, which are papillate on both sides, perigone 1.8–2.5 cm long, funnel-shaped, yellowish and light purple striate, perigone tube 0.3–0.7 × 0.2–0.4 cm, filaments adnate to the perigone and arising 0.3–0.7 cm above the ovary apex, anthers 0.9–1.1 cm long, and style 2.1–3.5 cm long, exceeding the perigone tube by 1.8–3 cm at anthesis. Manfreda occidentalis also resembles M. chamelensis; however, phenologic asynchrony is a notable difference between them as well as the shape of the leaves and the length and shape of perigone tube and lobes. A distribution map, photographs, and a key to identify species of Manfreda which grow in western Mexico accompany the description.

Dynamic axial crushing of bitubular tubes with curvy polygonal inner-tube sections

Bitubular structural configurations, where the outer tube is circular, square and curvy square in shape while the inner-tube section is curvy triangular, square and hexagonal in different proposed configurations, are numerically crushed under dynamic axial loading. The crashworthiness effectiveness for changing inner-tube polygonal cross-section for each of the outer tube sections is studied and compared with changing outer tube shape. The deformation plots and energy absorption (EA) parameters such as peak crushing force (PCF) mean crushing force (MCF), energy absorption and crush force efficiency for each case are evaluated. Most of the configurations showed ovalization with low PCF and MCF and moderate crush force efficiency. Afterwards, effects of [Formula: see text] and [Formula: see text] on deformation modes and EA are demonstrated by selecting one of the configurations from each group using published experimental results.

Axial load behavior and strength of tube-confined steel-reinforced short columns with ultra-high-strength concrete

This article elaborates on experimental and analytical studies on the behavior of tube-confined steel-reinforced ultra-high-strength concrete short columns subjected to axial compressive load. A total of 22 specimens were fabricated and tested to investigate the failure mode and axial load behavior of tube-confined steel-reinforced concrete columns. The parameters for the tests include the following: (1) tube shape, (2) the shape of inner steel, (3) the thickness of the steel tube, and (4) tube tensile strength. The test results indicate that the confinement effect of the circular tube is greatly superior to that of the square tube, because the circular tube can prevent the ultra-high-strength concrete from brittle failure more efficaciously. The O-shape of the steel exhibited better mechanical performance than other shapes of the steel. The larger the area of the concrete that could be constrained by the steel shape, the better the performance it could provide. Elastic–plastic analysis of the tube was utilized to investigate the mechanism of tube-confined steel-reinforced concrete columns under axial compression. A bearing capacity formula for tube-confined steel-reinforced concrete columns was proposed based on the test results, which can be used as a reference for further study and guideline for engineering application.

Multi modality of hollow tube Gd2O3:Eu3+ nanoparticles by using nonpolar solvent

Gd2O3:Eu3+ is useful material in physics, chemical and biomedicine which can be applied to the magnetic resonance imaging (MRI) brightness, X-ray computed tomography (CT) as contrast agent and luminescence phenomenon as phosphor. In this paper, Gd2O3:Eu3+ was synthesized by one-step low cost solvothermal reaction with different ratio of solvents (De-ionized water (DI)/toluene (TL)). The alteration of solvent ratios affects the morphology (rod to hollow tube shape) and size of Gd2O3:Eu3+ which induce the property variation such as luminescence intensity, MR imaging and CT imaging brightness. The luminescence intensity of Gd2O3:Eu3+ nanoparticles with DI 40/TL 0 is much higher than the 1.48, 1.68, 1.73 and 1.75 times by others (DI 0/TL 40, DI 10/TL 30, DI 20/TL 20 and DI 30/TL 10), MR images of Gd2O3:Eu3+ with DI 0/TL 40 were shown to be 2.5 times brighter than that of the commercial contrast agent (Dotarem) and CT images of Gd2O3:Eu3+ with DI 0/TL 40 was 1.68 times brighter than Dotarem. Gd2O3:Eu3+ prepared with different solvent ratios can be selectively applied for potential applications as MRI, CT and FI multimodal imaging agent.

Assessment of laryngopharyngeal reflux and the shape of the Eustachian tube should be considered in chronic rhinosinusitis with nasal polyps and chronic otitis media

Assessment of laryngopharyngeal reflux and the shape of the Eustachian tube should be considered in chronic rhinosinusitis with nasal polyps and chronic otitis media

Design optimization and validation of high-performance heat exchangers using approximation assisted optimization and additive manufacturing

The airside thermal resistance of air-to-fluid heat exchangers dominates the overall thermal resistance. On conventional heat exchanger's, fins are required to address such challenges; but their benefits are not limitless and are bound mainly by the tube size and shape. The reduction of the tube characteristic length has favorable impact on compactness and heat transfer. Conventional tubes are typically limited to round, elliptical or flat shapes which result in particular thermal-hydraulic characteristics. The current article has three main objectives. First, discuss the importance of fins on typical air-to-fluid heat exchanger's and how they become unattractive at smaller characteristic lengths with numerical analyses to support this argument from different perspectives. Second, present a proof-of-concept design with small finless tubes and a novel shape that can outperform a microchannel heat exchanger. Third, present a comprehensive analysis with shape optimization leveraging automated computational fluid dynamics simulations and approximation assisted optimization techniques. Optimum designs can achieve more than 50% reduction in size, material, and pressure drop compared to the baseline microchannel heat exchanger. The method is validated with the experimental validation of a metal three-dimensional printed prototype of the NTHX-001. The numerical simulations agreed within less than 5% in capacity, 10% in air heat transfer coefficient, and 15% in air pressure drop.

Numerical study to predict optimal configuration of fin and tube compact heat exchanger with various tube shapes and spatial arrangements

The study aims at numerically evaluating the thermal hydraulic performance of fin tube heat exchangers with circular, oval and flat tubes having inline and staggered arrangement. Three performance evaluation criteria (PECs), namely, area goodness factor (PEC1), heat transfer rate per unit fan power consumption (PEC2) and heat transfer rate per unit total power consumption (PEC3) are considered. Furthermore, the MOORA (multi-objective optimization on the basis of ratio analysis) method is employed to obtain the order of performance and that order is compared with the conventional PECs (performance evaluation criteria), showing good agreements. From the overall optimization study finally, it has been observed that the oval tube having highest axes ratio is the optimum configuration based on the considered PECs. It shows an increase in heat transfer coefficient by 13.99% at lower airside Reynolds number of (Re=400) and 4.99% at higher airside Reynolds number (Re=900). Also, the pressure drop is reduced by 39.94% at higher Reynolds number (Re=900) compared to the circular tube shape with the inline arrangement.

Laminar flow and heat transfer in an internally-cooled hexagonal parallel-plate membrane channel (IHPMC)

A internally-cooled hexagonal parallel-plate membrane contactor has been proposed and employed for liquid desiccant air dehumidification, which contains a series of internally-cooled hexagonal parallel-plate membrane channels (IHPMC) for the liquid desiccant stream. Several cooling tubes are installed in the solution channel to take away the absorption heat swiftly. The friction factors and heat transfer coefficients in the complex IHPMC are necessary for the structural design and energy analysis. This study will be focused on the influences of the channel structural parameters on the product of mean friction factors and Reynolds number (fRe)m and Nusselt numbers (Num) in the IHPMC, instead of on the coupled heat and mass transports. The laminar flow and heat transfer in the solution channel are studied based on a unit cell containing the sandwiched domain outside the cooling tubes between two neighboring membranes. The momentum and thermal transport governing equations are built up together with a uniform wall temperature boundary condition and solved by a finite volume approach. The mean (fRe)m and Nusselt numbers (Num) are calculated and analyzed. Influences of the tube numbers (N), tube outer diameters (do), tube distributions, Reynolds number (Re), and tube shapes on the (fRe)m and Num are studied. It can be found that when the do is equal to 0.002m, the (fRe)m rises with an increase in the N, while the Num decrease with the N increasing. When the N is fixed as 3, the (fRe)m increase with the do increasing, and the Num decrease with the do increasing. The results are useful for the performance evaluation, structural design of the membrane contactors formed by the IHPMC used for liquid desiccant air dehumidification.

Sandwich Plate System (SPS) with Polyurethane Elastomer for Submerged Floating Tunnel (SFT)

Submerged Floating Tunnel (SFT) i.e. Archimedes Bridge (AB) is a tubular structure that floats at a certain depth below the surface of the water carrying capacity exploiting derived from Archimedes lift. Various studies have been conducted on SFT but but no SFT has been constructed yet. The most important for design and build for SFT is the section. Research for the tube section of SFT has been doing for oval and circle shape with steel and concrete for the material, the conclusion is the section of the steel material with a circle is better than the cross section of the concrete. The section of SFT, which is identical to the vessel so that it is suitable when applied methods used on ships. One method that was developed in the vessel is Sandwich Plate System (SPS). SPS is a lightweight material that consists of two steel plates separated by a core in the form of elastomer. Elastomers which began much studied at the SPS is polyurethane. SPS advantage with polyurethane as the core has many advantages such as resistance to chemical reactions seawater, vibration and noise as well as strong against explosions.The tube shape is circle where inside diameter is 5 m, length is 150 m. Wave height is 5 m and wave period is 1.2 s with seabed -20m. Wave load will be applied to the tube as hydrostatic wave load arround the tube and dynamic wave load to the one side. Anlysis using Abaqus 6.14 and obtain the maximum and minimum stresses in x, y and z direction occure to the hole of cable in the belt and yied at the point. Maximum deflection in z direction is 83.466 mm in the same direction of load and y direction is 9.83 mm to the up side. Increament the step time makes the displacement is increase too.

Mechanical and Durable Properties of Ni-YSZ Electrode Under High Temperature for Solid Oxide Electrolysis Stack

Many researches based on SOFC development and high temperature electrolysis (HTE) have been reported in the last couple of decades. HTE is one of the most clean and efficient technologies for manufacturing large amounts of hydrogen from water with oxygen. The processing and structure of HTE is closely related to the knowledge and concept of solid oxide fuel cells (SOFCs). Specially, it is very important to evaluate the durability’s properties of oxide electrolysis stacks under high temperature as well as steam environment to apply HTE. Unfortunately, no study has been reported the durable properties of oxide electrolysis stacks at high temperature as well as steam environment. For the reason, the aim of this work is to realize the durable properties (ex, high temperature strength fatigue and creep) at high temperature of 600°C~850°C for oxide electrolysis stacks which consists of 55%NiO-45%YSZ(8mol%Y2O3) composition. NiO-YSZ cathode supports were prepared in the shape of flat tubes by extrusion method. The pre-sintered NiO-YSZ flat tubes were dip-coated in YSZ slurry to secure the interconnector area with a masking fluid and then were sintered at 1400°C for 3h. The creep properties showed decreasing tendency with increasing applied load in range of 40~80MPa and temperature in range of 600°C~800°C. The life time of fatigue at 850°C under Ar-4%H2O environment was decreased with increasing applied load.