Cross Section Of Tube Research Articles

Transportation of particulate suspension in a Newtonian fluid by dilating peristaltic waves in a tube of uniform cross-section: Application to flows in normal oesophagus

Transportation of particulate suspension in a Newtonian fluid by dilating peristaltic waves in a tube of uniform cross-section: Application to flows in normal oesophagus

Performance characteristics of shell and helically coiled tube heat exchanger under different tube cross-sections, inclination angles and nanofluids

The current research deals with an experimental and numerical inspection of the shell and helically coiled tube heat exchanger (SHCTHE) under various circular, elliptic, and square tube cross-sections. The research study strives to ameliorate the thermal-hydraulic performance with single nanofluids of Al2O3/H2O, MgO/H2O, and TiO2/H2O. Various factors were inspected to consider the heat exchanger performance under parameters, SHCTHE inclination angle, HCT diameter ratio, flow direction, the cross-section geometry shape, nanomaterials type, and nanomaterials concentration. The modeling engaging a numerical code tool of ANSYS-FLUENT 19 was accomplished with a 3D (RNG)/k–ϵ model. The mass flow rate and working fluid temperatures through the coil and shell sides were (0.05:0.2 kg/s at 80 °C and 0.05–0.2 kg/s at 10 °C, respectively. One of the most important results was that the SHCTHE with a circular tube cross-section gave the highest Nusselt number with an approximate percentage of 62.5%. The SHCTHE effectiveness and the number of transfer units were enhanced by around 19.35% and 30.78%, respectively, by the greater HCT diameter ratio and Al2O3 nanomaterials. Nusselt number, friction factor, and SHCTHE effectiveness were correlated through equations (52:55) with dimensionless factors and their limitations.

Performance improvement of photovoltaic/thermal systems by using twisted tapes in the coolant tubes with different cross-section patterns

A numerical technique is applied to study the efficacy of integrating twisted tapes to the collector of Photovoltaic/Thermal (PV/T) units on the system performance when the tubes with different cross-sections are used. Hence, computational fluid dynamics is employed to evaluate PV/T systems with and without twisted tapes when using cylindrical, rectangular, and triangular patterns for the tube cross-section. The effect of employing twisted tapes with various pitch-to-width ratios (YD) of 3, 4 and 5 is evaluated. The impact of the total inlet mass flow rate ranging from 25 to 150 Lhr is also studied. To analyze the system performance the evaluation of energy and exergy is performed. The results demonstrated that the triangular pattern is the optimum pattern for the tube cross-section without twisted tapes. However, inserting a twisted tape makes the cylindrical tube superior to other designs from electrical and thermal aspects. A collector employing a cylindrical tube with and without a twisted tape could increase the module's electrical efficiency by 7.2 and 9%, respectively. Also, it was observed that integrating twisted tape with the lowest value of pitch-to-width ratio could decrease the surface temperature by 3.2 and 17.55 K compared to the systems with cylindrical tubes and PV alone.

Investigation on the wall thickness variation of an eccentric tube in the rotary draw bending process

PurposeWhen bending a large diameter thin-walled tube, the thickn ess of outer side wall will reduce greatly, which leads to a decrease of structural strength of the tube. To solve this problem, this paper investigated the deformation principles of an eccentric tube in the rotary draw bending process, trying to find a way to reduce the wall thickness difference between inner and outer diameters.Design/methodology/approachAn finite element model is established for analyzing the deformation of an eccentric tube in rotary draw bending process. The wall thickness distribution of the formed pipe was analyzed along the axis and diameter, respectively.FindingsIt is found that there exists an optimal eccentricity between the inner and outer circle center of the tube cross-section. If the eccentricity of the tube is chosen properly, it is possible to get a bent tube with equal thickness of inner and outer side walls. In addition, it is also found the optimal eccentricity on the cross-section can be influenced by bending radius, wall thickness, diameter and bending angle. The optimal eccentricity increases greatly with the decreasing of bending radius, the increase of outer diameter and the increase of wall thickness. The influence of bending angle on the optimal eccentricity can be divided into two situations. When the bending angle is small, the optimal eccentricity increases with the increase of bending angle. When the bending angle exceeds a certain value, the pipe enters a stable forming state. The optimal eccentricity of the stable forming region does not change with the bending angle.Originality/valueSuch a research is beneficial for reducing the thickness difference between inner and outer side walls in the rotary draw bending process.

Formation and Evolution Mechanism of the Inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in Seamless Steel Tube Steel

Herein, the formation and evolution mechanism of inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in seamless steel tube steel are investigated. In the long strip defects on the longitudinal cross section of the steel tube after the rolling bar piercing, the defect is mainly formed by Al2O3·SiO2·CaO·MgO inclusions and Al2O3·SiO2·CaO·inclusions dotted with·CaS inclusions after the rolling. The typical inclusions in the different steelmaking stages are mainly composed of CaS, Al2O3·(SiO2), CaO·(SiO2), MnS·(TiN), Al2O3·SiO2·CaO·(CaS)·(MnS), Al2O3·SiO2·CaO·MgO·(MnO), Al2O3·SiO2·CaO·MgO·(CaS)·(MnS), etc. In the billet, the average sizes of Al2O3·SiO2·CaO‐based and Al2O3·SiO2·CaO·MgO‐based inclusions are much larger than those of the other types of inclusions. Part of SiO2 in the deoxidized products SiO2 can be reduced by [Al], resulting in the formation of the Al2O3·SiO2 composite inclusions. The SiO2 in Al2O3·SiO2 inclusions can continuously be reduced by the dissolved [Ca] to form the Al2O3·SiO2·CaO composite inclusions. The SiO2 in the Al2O3·SiO2·CaO inclusions can be reduced by the dissolved [Mg] to form the Al2O3·SiO2·CaO·MgO composite inclusions. Another formation process of Al2O3·SiO2·CaO·MgO inclusions is the entrapment of ladle slag in the vacuum degassing (VD) stage, due to the strong agitation of the rising Ar bubbles in the vacuum condition of the VD stage.

Interphase Mechanical Energy Transfer of Gas-Liquid Flow in Variable Cross-Section Tubes

The use of gas energy includes a wide range of applications to directly accelerate the liquid in a pipeline without the aid of mechanical equipment, such as marine gas-liquid jet propulsion. To clarify the characteristics of energy transfer by interphase forces for gas-liquid flows in variable cross-section tubes, two-fluid models of annular flow, bubbly flow and homogeneous flow were adopted, respectively, along with four newly elaborated coefficients, which are the work factor of gas fg, reflecting the relative ability of gas to power liquid, the interface work transfer coefficient kg (representing the relative magnitude of mechanical work received by liquid from gas), the interphase work-to-energy conversion coefficient kl (denoting the capability of energy transfer through work performed by interphase forces) and the interphase mechanical efficiency ηw. The results reveal the interphase work transfer is strongly influenced by the structural parameters of the tubes (or nozzles), and an optimized design is necessary to improve the performance. The higher the degree of gas dispersion in the liquid, the more advantageous the conversion of gas work into the liquid’s mechanical energy. Of these three flow patterns, annular flow has the lowest kl and ηw (kl = 0.0797, ηw = 0.9885 in present example), while homogeneous flow displays the limit of interphase mechanical energy conversion because the gas-liquid momentum coupling reaches the maximum (kl = 0.9979, ηw = 1).

The thermal performance of ground-coupled heat exchanger with different geometrical shapes – a numerical study

ABSTRACT The thermal performance of different cross-sectional areas of a U-shape ground-coupled heat exchanger (GCHE) is numerically investigated for summer and winter conditions in the present paper. The four different cross-sectional tubes, viz. square, circular, triangular, and rectangular, of fixed hydraulic diameter and length are considered. Numerical simulations are carried out for different velocities ranging from 2 m/s − 5 m/s using K-epsilon turbulent model. It is found that the rectangular cross-sectional area GCHE provides a more stable air temperature for both summer and winter conditioning, and a maximum temperature drop/rise is observed at a shorter length in this condition. The temperature drop of 14.2 K is observed at a length of 12.6 m in the case of GCHE with rectangular cross-section, while the same drop is reported at 19.2 m, 17.4 m, and 16.5 m for circular, square, and triangular cross-sectional areas, respectively. A maximum temperature rise of 8.3 K is reported at 14.8 m, 20.7 m, 18.2 m, and 17.5 m in rectangular, circular, square, and triangular cross-sectional GCHE for heating conditions. Therefore, the rectangular cross-section GCHE may be preferred for space constraints. The net temperature difference is found to be dependent on inlet air temperature. It increases with an increase in the inlet air temperature for summer cooling conditions and reverses in winter conditions. The inlet velocity greatly influences the thermal performance of GCHE, and optimum performance is found at a lower velocity of 2 m/s due to the more settling time. The effectiveness is found to increase initially along the length, and it attains a maximum value at a shorter length in the case of rectangular cross-section compared to other sections. The maximum effectiveness is achieved between 14 m to 15 m length of the pipe for the case of rectangular cross-sectional GCHE.

Suspended solid removal efficiency of plate settlers and tube settlers analysed by CFD modelling.

Removal of suspended solids from raw water is an essential process in water treatment plants. Conventional sedimentation tanks in water treatment plants occupy a large area and become expensive in urban areas. The use of plate settlers or tube settlers in sedimentation tanks to increase the efficiency and hence reduce the footprint of sedimentation tanks is an economical solution in water treatment. This study investigated the effectiveness of plate and tube settlers compared to conventional settlers in a water treatment plant. A three-dimensional Computational Fluid Dynamics (CFD) model was set up using ANSYS-CFX 17.2. Seven cases (a conventional settler, three plate settlers and three tube settlers) were analysed to compare the settler performances. The maximum removal efficiencies of all solid classes were approximately equal in plate and tube settlers with the same plate spacing and tube depth: around 100%, 67%, 28% and 9% for the solid classes with particle diameters of 41, 17, 9.5 and 5.0 µm, respectively. The settling efficiency remained unchanged with the increase of the plate settling area beyond 60% of the conventional settler area under the given tank and flow conditions. The tube cross-section shape does not affect the particle removal efficiency of a tube settler.

Comparison of geometric optics and «aperture» methods for calculation of the electromagnetic radiation caused by charged particles flying by dielectric objects

Calculation of the electromagnetic field exited by a charged particle flying close to dielectric object is one of the important problems of charged particle radiation theory. In some cases, geometric optics area is preferable for calculations. In the article, two methods of solution of such problem with dielectric prism possessing large size (in comparison with the wavelength under consideration) are considered. One of them is based on geometric optics method, another one is based on asymptotics of «aperture» integrals. It is shown that, in geometric optics area, the first method has a series of advantages. For example, ray tube cross-section expression obtained within geometric optics method allows one to find caustics or to show their abscence, which is demonstrated in the article for three objects of various shapes.

Numerical analysis of a heat exchanger with curved segmental baffle and Cassini oval cross-section tubes in various bundle arrangements

Numerical analysis of a heat exchanger with curved segmental baffle and Cassini oval cross-section tubes in various bundle arrangements

Exponential horn revisited: wave equation, normal modes and experimental measurements

In this work, a theoretical analysis is first presented to find the wave equation corresponding to the propagation of disturbances in the air contained inside a tube of variable cross section. In particular, the case of a tube with a circular cross section whose area varies exponentially as a function of the axial coordinate is studied. The hypotheses of the model used are discussed and the solutions of the wave equation obtained are presented. Secondly, and with the aim of validating the model used, measurements are made on a tube such as the one described, built using a 3D printer.

Environmentally assisted cracking of a single crystal nickel-based superalloy

ABSTRACT Single crystal material, of CMSX-4® alloy composition, was cast and secondary orientation was controlled at the machining stage, to produce c-ring cross-section tubes with known crystallographic orientations. The c-ring tubes were coated with NaCl before being subject to loading up to 700MPa and heated for durations of up to 2 hrs at 550°C in flowing environments containing air and SO2. No cracking was observed in short term tests that were run in the absence of either NaCl, or SO2, indicating a symbiotic interaction is required to initiate cracking. Experiments confirm the presence of oxygen, chlorine and sulphur at the crack tips, formed along {001} crystallographic planes, however, they were distributed discretely, with several oxide and sulphide phases observed. In this work, we image, analyse and identify the phases formed during the cracking and corrosion of CMSX-4® superalloy and hypothesise on the complex chemical interactions that take place during crack initiation.

Multi-scale analysis of solute dispersion in non-Newtonian flows in a tube with wall absorption

This study presents the two-dimensional concentration distribution of a solute cloud for non-Newtonian fluid in a tube flow with wall absorption. The non-Newtonian fluid models, such as the Carreau–Yasuda and Carreau fluid models, are helpful in investigating solute dispersion in the bloodstream and have also been effective in understanding hemodynamics. The multi-scale method of homogenization is used here to analyze the dispersion of solute through a straight tube for Carreau–Yasuda and Carreau fluids, which represents the shear-thinning nature. Most of the previous studies are mainly focused on determining the dispersion coefficient and mean concentration distribution for non-Newtonian fluids. Apart from those in our study, we also derived analytical expressions for the two-dimensional concentration distribution for Carreau–Yasuda and Carreau fluids. As the exact peak position of the two-dimensional concentration is a concern in real-life applications rather than that of mean concentration, the effects of wall absorption parameter (α*), the Weissenberg number (We), Yasuda parameter (a), and power-law index (n) on solute concentration distribution are discussed. Comparison between the present results and previous results of solute dispersion for non-Newtonian as well as Newtonian fluids are also enclosed in this study. Results reveal that the mean concentration decreases with increasing values of We because of an increase in the dispersion coefficient. Carreau–Yasuda and Carreau fluids act like Newtonian fluid for very small values of We. At the initial stage, the solute concentration exhibits transverse non-uniformity and then becomes uniform over a larger timescale. The effects of non-Newtonian parameters such as We, a, and n on transverse variation are also studied. It is noted that parameters n, We, and a have no significant impacts on the non-uniformity of the transverse concentration variation on both sides of the tube centroid, but that is not the case for the wall absorption parameter. It is observed that wall absorption results in significant transverse concentration non-uniformity across the tube cross section even after large times.

Numerical study on heat transfer characteris tics of supercritical water in straight and helical tubes

The subcritical steam generators in high-temperature gas-cooled reactor pebble-bed modules can be replaced by supercritical steam generators to improve thermal efficiency. The axial and circumferential nonuniform flow and heat transfer characteristics of supercritical water in straight and helical tubes with varying inclinations (0–90°) are simulated to investigate the combined effects of tube structure, flow direction, thermophysical properties, property variations, buoyancy, and centrifugal forces. With heat fluxes of 233–930 kW/m2 and inlet mass fluxes of 225 or 1260 kg/(m2 s) under a working pressure of 24.5 MPa, the friction coefficients, turbulent kinetic energy, secondary flow, temperature, and heat transfer coefficients are studied in the cross section of variable structure tubes. The wall temperature and heat transfer coefficients of four regions are compared in straight and helical tubes; the maximum heat transfer coefficient appeared before the pseudo-critical point. The heat transfer coefficients are the greatest at the bottom of the straight tubes, where fluidity was high, and at the outer of the helical tubes, where the fluid velocity was high under centrifugal force. The secondary flow in the helical tubes causes a nonuniformity in the wall temperature, causing the circumferential maximum wall temperature to move.

Interplay between salt precipitation, corner liquid film flow, and gas–liquid displacement during evaporation in microfluidic pore networks

Visualization experiments with microfluidic pore networks are performed in this work to disclose interplay between salt precipitation, the corner liquid film flow, and gas–liquid displacement during evaporation. Two forms of salt precipitation are revealed: aggregated polycrystalline structures and large bulk crystals. It is found that gas bubbles can be formed because of imbibition of liquid into aggregated polycrystalline structures. The length of a corner liquid film can affect the direction of growth of the aggregated polycrystalline structures connected to the corner liquid film. Discontinuous corner liquid films can be transformed to continuous ones when they are touched by growing aggregated polycrystalline structures. The “sleeping” aggregated polycrystalline structures at the open surface of a microfluidic pore network, i.e., efflorescence, can grow again if they are touched by growing aggregated polycrystalline structures inside the microfluidic pore network, i.e., subflorescence. Because of efflorescence, the evaporation rate from a microfluidic pore network can increase first and then decrease. Moreover, a theoretical model is developed for the coupled transport of vapor diffusion in the gas zone and liquid flow as well as transport of dissolved salt in the corner liquid films in a capillary tube of square cross section so as to disclose the key parameters controlling the transport processes.

Experimental Study on Strength Deformation Behavior of Large Diameter Thin-Walled Aluminium Alloy Tubes Subjected to CNC Bending

The strength deformation behavior of thin walled aluminium alloy 6063 tubes under flexure has been presented. The effects of deformation, thinning, thickening of the tube wall surfaces, ovalness of the tube and springback angleat critical cross sections of the aluminium tubes are studiedunder different computer numerical control (CNC) bending conditions. Aluminium alloy tubes of 25mm outer diameter, 390 mm length and varying thickness of 1, 1.5 and 3mm have been used for testing. It is observed that, thinning and thickening of inner and outer bend of tube gradually rises with increase in the bend angle and meantime surface flattening and non-circularity of tube in terms diameters also upsurges for the increase in bend angle.Furthermore, experimental outcome of deformed tube is compared and characteristic result for effect of experimental parameters is found to be in good agreement with literature values.

Behaviour and confinement-based direct design of concrete-filled cold-formed stiffened steel tubular short columns

The advantages of concrete-filled square steel tubular columns are currently being widely utilised in various applications, especially in marine and ocean structures. However, the use of slender cross-sectional tubes significantly reduces the concrete core confining effect due to the local buckling (LB) phenomenon of these tubes. Accordingly, welded stiffeners have been proposed to generate stiffened steel tubes to reduce the effect of LB. But due to welding, residual stress causes significant initial imperfections in the columns. This has resulted in the emergence of the concrete-filled cold-formed stiffened steel tubular (CFSST) columns that consist of cold-formed longitudinal stiffeners embedded in the concrete core. The literature shows that studies into the response of these columns are relatively limited. Accordingly, finite element (FE) modelling of CFSST columns with cold-formed steel tubes is used herein to increase the data bank of these columns. First, available test results on such columns using carbon steels were used to validate the FE models. Then, parametric studies were generated to suggest an innovative lateral confining pressure. These studies were also used to explore the effect of the depth-to-thickness ratio of the outer steel tube, concrete cylindrical strength and stiffener depth on the resistance and behaviour of the square CFSST columns with cold-formed steel tubes. It was found that increasing the cylindrical concrete strength is the most effective way to increase the ultimate strength of the columns, although it decreases the ductility of the columns. In addition, the strengths of CFSST short columns with cold-formed steel tubes were compared with the Japanese, British, European and Chinese codified strengths, which were found to provide conservative predictions. Finally, a new strength was provided for the CFSST short columns with cold-formed steel tubes based on a proposed linear law formula for the lateral confining pressure caused by the stiffened cold-formed tubes.

Dryout quality prediction in helical coils based on non-uniform liquid film thickness distribution: A model study

Dryout occurrence has an adverse effect on the thermal efficiency of helically coiled steam generators used in thermal energy storage systems. In this study, a mechanistic model based on the non-uniform annular liquid film thickness distribution was developed to evaluate the quality of dryout occurrence in helical coils. The inner-side and outer-side liquid films were investigated, including the local effects of entrainment, deposition, and dryout, while the film interface profile in the tube cross-section was simplified as a half-ellipse. The deposition correlations reported in the literature were modified by considering the centrifugal effect. The entrainment correlations were compared and optimized to improve the dryout prediction. The proposed model achieved satisfactory agreement on a boiling crisis dataset of 994 test points with a mean absolute error of 35.2%, which is better than existing models. The current work can be used in thermohydraulic design and performance prediction for thermal energy storage systems.

Transient dynamics of pressure-driven encroachment in narrow conduits with rate-dependent body force

We analytically explore the flow of a Newtonian liquid forced to encroach a narrow tube of uniform cross section, by an unsteady pressure gradient, assisted by an encroachment-rate dependent external force. This novel problem is thought to have interesting implications. For instance in medicine where narrow tubes like syringes and needles are typically used to administer medication and in the printing industry. Using an unsteady eigenfunction expansion, the velocity distribution is accurately defined to yield unsteady profiles, contrasting with the classical Poiseuille parabola. We subsequently used our unsteady spectral decomposition to properly capture the kinematics and dynamics hidden in the models. By a detailed comparison between rectangular and circular channels, we show that such model ducts yield interesting similarities that can inform the choices of channels. Moreover, we obtain short and long-time dynamic behaviors, captured using a robust perturbation scheme that elegantly highlights the early and long-time characteristics. In the end, we present plots for encroachment depth and rate and the early and long-term asymptotic approximations and appropriately their graphical trends.

Desenvolvimento de um modelo numérico para simular o comportamento de conectores em chapa aplicados a pilares mistos preenchidos com concreto de seção esbelta

Abstract The cross-section of concrete-filled steel tube (CFST) columns is classified according to the local slenderness of the steel tube as slender, non-compact, or compact. There are analytical models to determine the axial force of locally slender CFST columns, however studies on load transfer from beams connected to these columns are scarce. This paper presents the process of the development and validation of a numerical model to simulate the behavior of Crestbond connectors applied to CFST columns with slender steel tubes, based on the results of experiments carried out. The numerical model presented can be used for the analysis and design of the load transfer in slender columns using connectors known as composite dowels.