Bundle Of Cylinders Research Articles

Transfer-Matrix Method for Calculus of Long Cylinder Tube with Industrial Applications

The Transfer-Matrix Method (TMM) is an original and relatively simple mathematical approach for the calculus of thin-walled cylindrical tubes presented in this work. Calculation with TMM is much less used than calculation with the Finite Elements Method (FEM), even though it is much easier to apply in different fields. That is why it was considered imperative to present this original study. The calculus is based on Dirac’s and Heaviside’s functions and operators and on matrix calculation. The state vectors, the transfer-matrix, and the vector corresponding to the external efforts were defined, which were then used in the calculations. A matrix relation can be written, which gives the state vector of the last section depending on the state vector of the first section, a relation in which the conditions of the two end supports can be set. As an application, a heat exchanger was studied, with a large cylinder subjected to a uniformly distributed internal load, and from the inner cylinder bundle, a cylinder subjected to both uniform internal and external loads was considered. For the second cylinder, two possibilities of action for the external forces were considered, a successive action and a simultaneous action, achieving the same results in both situations. The TMM is intended to be used for iterative calculus in optimization problems where rapid successive results are required. In the future, we want to expand this method to other applications, and we want to develop related programs. This is an original theoretical study and is a complement to the research in the field on thin-walled cylinder tubes and their applications in heat exchangers.

Bacterial wilt biocontrol by the endophytic bacteria Gluconacetobacter diazotrophicus in Río Grande tomato cultivar

Bacterial wilt disease caused by Ralstonia solanacearum affects a wide variety of crops, including tomatoes. Novel natural products and organisms offer opportunities for innovation in agroindustry as an alternative way to pest and pathogen controls. Gluconacetobacter diazotrophicus Pal5 (Gd) belongs to PGPBEs (Plant-Growth-Promoting Bacterial Endophytes), which facilitate plant growth via phytostimulation, biofertilization and biocontrol. In this study Río Grande tomato seedlings were inoculated with Gd to test its ability to colonize them and its protective potential against the phytopathogen Ralstonia solanacearum A21 (Rso). Gd root and stem colonization of tomato seedlings were determined. Stem height was markedly affected by the inoculation with Gd after 80 dpi and a set of biochemical and anatomical structural changes in root, stem and leaves were triggered. The resistance mechanisms elicited in the plant after inoculation with the endophytic bacteria involved reinforcement of the cell walls in the root vascular cylinder and stem vascular bundles, with the presence of an augmented number of contact cells with dense cellular content, probably pectins, lignin and tannins. Roots and stems presented thicker and more lignified xylem vessel walls. These plants showed statistically significant differences with mock inoculated plants in several quantitative variables, such as area of the xylem vessels in root and stem. Biocontrol assays without Gd showed wilting at 9 dpi with Rso. Histological analysis showed bacteria cells filled xylem vessels and dispersal through tissue degradation. In contrast, plants with Gd remained asymptomatic and phytopathogen colonization was observed to a lesser extent in the stem and root. Anatomical changes primed by Gd were enhanced upon Rso infection and the tyloses process appeared. Therefore, Gd primes the resistance mechanism in Río Grande tomato plants significantly reducing bacterial wilt caused by Rso.

Direct measurement of steady fluid forces upon a deformed cylinder in confined axial flow

This paper addresses the case of a cylinder array in axial flow at Reynolds numbers from 60000 to 110000. A comprehensive experimental and numerical study of the steady fluid forces arising from a geometrical perturbation in the array arrangement is carried out and compared with a semi-empirical model from the literature. The test rig consists of a 3x3 confined cylinder bundle with a pitch-to-diameter ratio equal to 1.33. The central cylinder can be rotated, translated or bent. Global forces and moments as well as pressure profiles at several sections are measured. Velocity profiles at both sides of the cylinder are also collected. Additionally, RANS simulations (Reynolds-averaged Navier–Stokes) are carried out. Pressure loss effects similar to the ones occurring in hydraulic pipes are found to play a major role on the velocity field. Rotation tests are in agreement with the literature: at low angles of incidence, the lift force is proportional to the angle. The supporting rod at the centre of the cylinder strongly disturbs the local lift force but does not change the global linear trend. In translation, the wake of the support generates a fluid stiffness effect. Bending tests allow to assess all terms of the semi-empirical model from the literature, which proves to be quite accurate at a sufficient distance from the ends and from the supports. In addition, the investigation provides refined quantitative measurements of local and global force coefficients of the statically deformed cylinder in rotation, translation and bending.

Monte Carlo Simulation and Experimental Studies of CO2, CH4 and Their Mixture Capture in Porous Carbons.

Adsorption of carbon dioxide and methane in porous activated carbon and carbon nanotube was studied experimentally and by Grand Canonical Monte Carlo (GCMC) simulation. A gravimetric analyzer was used to obtain the experimental data, while in the simulation we used graphitic slit pores of various pore size to model activated carbon and a bundle of graphitic cylinders arranged hexagonally to model carbon nanotube. Carbon dioxide was modeled as a 3-center-Lennard-Jones (LJ) molecule with three fixed partial charges, while methane was modeled as a single LJ molecule. We have shown that the behavior of adsorption for both activated carbon and carbon nanotube is sensitive to pore width and the crossing of isotherms is observed because of the molecular packing, which favors commensurate packing for some pore sizes. Using the adsorption data of pure methane or carbon dioxide on activated carbon, we derived its pore size distribution (PSD), which was found to be in good agreement with the PSD obtained from the analysis of nitrogen adsorption data at 77 K. This derived PSD was used to describe isotherms at other temperatures as well as isotherms of mixture of carbon dioxide and methane in activated carbon and carbon nanotube at 273 and 300 K. Good agreement between the computed and experimental isotherm data was observed, thus justifying the use of a simple adsorption model.

Gas Flow at Very High Pressure and Speeds

This article was created on the basis of long-term practical experience with the flow of compressed gases in pipelines and fittings. In areas of low pressures, up to about 0.4 MPa, the physical phenomena regarding the outflow of gas from pressure systems are relatively consistent with theoretical calculations. The higher the pressure in the pressure reservoir system (most often a container or a bundle of pressure cylinders), the greater the difference between the theoretical calculation and the actual behavior of the discharged gas. The data for this article are based on the calculation of the flow of compressed natural gas during uncontrolled discharge from a pressure container with a volume of 2 500 m3 and a pressure of 30 MPa.

Research of hydrodynamics and heat transfer during the transverse air flow of a row of cylinders with screw grooves

Cylinder cross-flow is a common phenomenon in many fields of technology. Technological simplicity of tubular structures makes them attractive, especially when using working bodies that are under different pressure values. However, the cylinders belong to the category of «poorly streamlined» bodies, and there are many opportunities to improve their hydrodynamics and heat transfer. For a circular cylinder, there is a speed range in which its hydraulic resistance can decrease due to the deformation of the cylinder surface. This phenomenon can be used for the rational design of heat exchangers. In the open-type wind tunnel, heat transfer coefficients and hydraulic resistances of single-row cylinder bundles with several types of spiral grooves on the outer surface have been determined. The largest increase in heat transfer (64 %) was shown by the cylinder with the smallest pitch of the groove (10 mm), the second place was taken by the cylinder with a relatively large step – 40 mm. Using the best spiral groove allowed reducing the hydraulic resistance by 19 %. Visualization and computer simulation have been used to explain the effects. The conformity of computer simulations to the experimental results was determined by comparing the average heat transfer coefficient (calculated and determined using an ice calorimeter). As a result, the turbulence model RNG_ke has been chosen, which provides a better fit of the experimental model. Computer simulations have explained the physical picture of the flow around cylinders with spiral grooves, including their mutual influence with a different axial orientation in the bundle. It has been shown that the presence of a spiral groove, which on the one hand increases heat transfer and on the other hand reduces hydraulic resistance, can significantly increase thermohydraulic efficiency (Reynolds analogy factor).

Natural convection heat transfer from a bundle of heated circular cylinders with staggered arrangement immersed in molten solar salt

A two-dimensional steady-state natural convection heat transfer from a bundle of closely spaced isothermally heated cylinders in a staggered arrangement immersed in molten solar salt was investigated in this study for a laminar flow regime using numerical analysis. The flow and temperature fields and heat transfer from the cylinder bundle were predicted as functions of tube spacing and flow conditions. It was determined that flow patterns and heat transfer are strongly affected by the transverse and longitudinal cylinder-to-cylinder spacing ST and SL, Rayleigh number and thermo-physical properties of the heat storage fluid. Performance maps in the form of contour diagrams for the average Nusselt number Nu and dimensionless heat transfer volumetric density are presented for a staggered bundle of circular horizontal cylinders immersed in a molten solar salt.The variation of the heat transfer enhancement for the staggered bundle of horizontal cylinders shows that there is an optimal transverse cylinder spacing resulting in the highest heat transfer enhancement. The heat exchanger geometry was optimized by determining the optimal set of the tube (cylinder) spacings SL/D and ST/D in the bundle resulting in the maximum volumetric heat transfer rate q ̃, and smallest size, and lowest cost of a heat exchanger. A set of correlations were developed for the maximum and optimum dimensionless heat transfer volumetric densities as functions of the Rayleigh number RaD. The analyzed geometries are important in the solar heating and storage technology, nuclear reactor safety, and waste heat recovery applications.

Macroscopic model of fluid structure interaction in cylinder arrangement using theory of mixture

In the framework of the theory of mixture, the dynamic behaviour of solid cylinder bundles submitted to external hydrodynamic load exerted by surrounding viscous fluid flow is described. Mass conservation and momentum balance formulated on an elementary domain made of a given volume of mixture give rise to a system of coupled equations governing solid space-averaged displacement, fluid velocity and pressure provided that near-wall hydrodynamic load on each vibrating cylinder is expressed as a function of both fluid and solid space-averaged velocity fields.Then, the ability of the macroscopic model to reproduce over time an averaged flow surrounding vibrating cylinders in a large array in the context of small magnitude displacements is pointed out. Numerical solutions obtained on a two-dimensional configuration involving an array of several hundreds of cylinders subjected to an impulsional load are compared to those provided by averaged well-resolved microscopic-scale solutions. The relative error is less than 3% in terms of displacement magnitude and 5% for frequency delay.The proposed macroscopic model does not include any assumption on relative effect contributions to mechanical exchanges occurring in the full domain. Therefore it features interesting properties in terms of fluid solid interaction prediction capabilities. Moreover it contributes to a significant gain in terms of computational time and resources. Further developments are now required in order to extent the formulation to large magnitude displacements including three-dimensional effects. This could be recommended for investigations on fuel assembly vibration risk assessment in Pressure Water, Fast Breeder reactors at a whole core scale or any other large-scale mechanical system involving some kind of periodic geometry.

Characterizing complex flows using adaptive sparse dynamic mode decomposition with error approximation

SummaryDynamic mode decomposition (DMD) is a powerful data‐driven method for analyzing the coherent structures of dynamical systems. This work develops an adaptive sparse DMD with error approximation for the sparse reconstruction of complex flow fields. First, we propose a new sparse DMD model by redefining the penalty function, where adaptive weights are assigned to penalize different DMD modes. With the adaptive weights, the sparse DMD model is more capable of extracting important DMD modes and discarding unimportant ones. Second, we develop a novel error prediction model for the proposed sparse DMD. The key idea is to construct a multiple regression model between the sparse model and its error by employing the partial least squares regression. The error of the sparse DMD model can be reduced by integrating the error prediction model. Finally, we assess the proposed method by means of test cases, including a nonlinear parameterized function, a cylinder bundle flow, and the transient state of square cylinder flow. The results show that the proposed method can be used to capture the dominant modes and substantially increase the accuracy of flow reconstruction.

Natural convection heat transfer from a bundle of in-line heated circular cylinders immersed in molten solar salt

A two-dimensional steady-state natural convection heat transfer from a bundle of closely spaced isothermally heated cylinders in the in-line arrangement was investigated in this study for a laminar flow regime using numerical analysis. It was determined that flow patterns and heat transfer are strongly affected by the transverse and longitudinal cylinder-to-cylinder spacing ST and SL, Rayleigh number, and thermo-physical properties of the heat storage fluid. Performance maps in the form of contour diagrams for the average Nusselt number Nu and dimensionless heat transfer volumetric density q ̃, and corresponding correlations are presented for an in-line bundle of 9 × 5 horizontal cylinders immersed in a molten solar salt.The variation of the heat transfer enhancement for the in-line bundle of horizontal cylinders shows that there is an optimal cylinder spacing resulting in the highest heat transfer enhancement. The heat exchanger geometry was optimized by determining the optimal set of the tube (cylinder) spacings SL/D and ST/D in the bundle resulting in the maximum volumetric heat transfer rate q ̃, and smallest size and lowest cost of a heat exchanger. A set of correlations were developed for the maximum and optimum dimensionless heat transfer volumetric densities as functions of the Rayleigh number RaD. The analyzed geometries are important in the solar heating and storage technology, nuclear reactor safety, and waste heat recovery applications.

Numerical investigation on the interactions of flow induced vibrations among neighboring cylinders in a cylinder bundle

Flow induced vibrations of one single cylinder have been investigated widely, however, many failures have been observed in multi-neighboring-vibrating cylinders rather than one isolated cylinder. Thus, the interactions of flow induced vibrations among neighboring cylinders and the corresponding coupling mechanisms were investigated in this study. The unsteady flow through normal triangular cylinder arrays with multi cylinders undergoing self-excited oscillations was simulated with a closely CFD/CSD coupled method. Lifts, displacements and velocities of the target cylinder were compared. The results show that vibrations of the target cylinder have been suppressed by interactions of neighboring flexible cylinders, it is conservative and feasible to investigate the flow induced vibration of a cylinder bundle with only one flexible cylinder instead of plenty of neighboring oscillating cylinders in the current configuration.

Heat transfer of a tube bundle in a pulsating flow

In the present paper, we report on the results of an experimental study of the transfer of heat and flow structure in the inter-tube space of in-line and staggered tube (cylinder) bundles in a pulsating external flow. For two values of the relative pitch in the bundles, the average heat transfer of a cylinder, and the distributions of the components of flow velocity and rms pulsations of that velocity in the inter-tube space, were measured. It is found that the change in the heat transfer of a bundle cylinder under forced flow unsteadiness correlates well with the level of the energy of velocity pulsations in the cylinder wake. The possibility of enhancement of heat transfer in a cylinder bundle using forced flow oscillations is demonstrated.

Investigation of shedding patterns and its influences on lift performances of a cylinder bundle in cross flow

Shedding vortices in cross flow are of much practical importance in the analysis of flow induced vibrations of a steam generator. However, studies of shedding vortex are still few in present, especially in shedding patterns and its influences on lift performances. In this paper, five basic shedding patterns were investigated by numerical simulations of a 2D unsteady flow around a bundle with 253 cylinders. The numerical results clearly demonstrated that flow in line is the most common pattern. On the hand, the other four shedding patterns, cross in line, cross near line near, cross near line far and cross far line near, appear randomly. Influences of shedding vortices on lift performances were concluded as lift enhancement, lift pit and lift lag. These numerical results can provide a basic knowledge of shedding vortices for cylinders and can precisely quantify their influences on unsteady lift performances.

Using sharp wedge-shaped porous media in front and wake regions of external nanofluid flow over a bundle of cylinders

PurposeThe purpose of this study is to analyze a new idea for external flow over a cylinder to increase the heat transfer and reduce pressure drop. Using wedge-shaped porous media in the front and wake regions of the cylinder can improve its hydrodynamic, and the rotating flow in the wake region can enhance the heat transfer with increased porous–liquid contact. Permeability plays a vital role, as a high-permeable medium improves heat transfer, whereas a low-permeable region improves the hydrodynamic.Design/methodology/approachTherefore, in the current research, external forced convection of nanofluid laminar flow over a bundle of cylinders is simulated using a two-phase mixture model. Four cases with different porous blocks around the cylinder are assessed: rectangular porous; wedge shape in trailing edge (TEP); wedge shape in leading and trailing edges (LTEP); and no porous block case. Also, three different lengths of wedge-shaped regions are considered for TEP and LTEP cases.FindingsResults are presented in terms of Nusselt (Nu), Euler (Eu) and the performance evaluation criterion (PEC) numbers for various Reynolds (Re) and Darcy (Da) numbers.Originality/valueIt was found that in most situations, LTEP case provides the highest Nu and PEC values. Also, optimal Re and porous medium length exist to maximize PEC, depending on the values of Da and nanofluid volume fraction.

Experimental study of the dryout of a 2D heat-generating model porous medium

Dryout experiments are performed in a quasi two-dimensional heat-generating model porous medium, with bottom flooding. The test section is composed of an array of heating cylinders placed between two ceramic plates. It is held vertically and a liquid (HFE-7000) is injected from bottom at a controlled flow rate, pressure and temperature. Dryout incipient power is investigated by applying an increasing thermal power to a bundle of heating cylinders until a dry zone is detected. The liquid inlet mass fluxes range from 1.0kgm-2s-1 to 10.5kgm-2s-1 and the heat fluxes are between 195kWm-2 and 1086kWm-2. Two kinds of dryout phenomenology are observed. First, at low liquid injection rate (below 4.2kgm-2s-1 inlet mass flux), reaching the dryout power results into a liquid front receding from the top of the test section to the upper limit of the heated zone, while downstream the heated zone, the porous medium is vapour-saturated. Second, at higher flow rate (over 5.2kgm-2s-1 inlet mass flux), the boiling crisis happens at the surface of a single heating element, resulting in a local film boiling, whereas a two-phase flow still go through the whole test section. In both cases, high-speed visualizations allow characterizing 8 boiling/flow regimes, depending on the inlet mass flux, the power released by the heated zone, and the location inside the porous medium. In particular, when reaching the dryout incipient power, the existence of a pulsed flow regime is highlighted. Such a characterization of boiling/flow regimes might be helpful in improving dryout models.

Analysis of flow behavior and fluid forces in large cylinder bundles by numerical simulations

This paper presents a numerical investigation of the three-dimensional flow around an in-line cylinder arrangement with up to twenty-five cylinders under confinement, with a subcritical Reynolds number, in the context of flow-induced vibrations. Flow characteristics and patterns, as well as the force coefficients of the cylinders and Strouhal numbers were evaluated numerically with the large eddy simulation approach and validated against previously published experimental data. Two values for both the transversal (T/D = 1.5 and 3) and longitudinal (L/D = 2 and 4) spacing ratios were considered and combined to generate four different arrangements. The velocity distributions obtained in the simulations were in good agreement with the experimental data. Fluctuations in the force coefficients were characterized for each arrangement and found to be directly proportional to the turbulence kinetic energy upstream of each cylinder. Depending on the flow pattern, certain rows are subjected to greater flow force fluctuations. The dominant frequency, expressed by the Strouhal number, was also mapped throughout the arrangements and its distribution was characterized according to the observed flow patterns. Although the spacing ratios have a combined effect, their separate influence on the general behavior and distribution of fluid forces could be identified, as these are linked to the flow regimes. This knowledge allowed for the contribution to an already existing in-line tube bundle classification, which is useful in the diagnosis of flow-induced vibrations and the design of heat exchangers and other industrial equipment.

Butle i wiązki acetylenowe w warunkach pożaru

The purpose of this article is to present fire and explosion properties of acetylene, the requirements for storing and transporting this gas, and to present the results of tests conducted on single acetylene cylinders and on cylinder bundles. Hazardous area coverage during rescue operations involving acetylene cylinders in open areas should be at least 300 m. Care must be taken when handling rescue operations and all available safety measures should be used.

PBTTT-C16 sol-gel transition by rod associations and networking.

A low-molecular-weight poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (designated as Lw-pBTTT-C16) in a fair solvent (chlorobenzene, CB) displays peculiar structural, mechanical, and electronic features during sol-gel transition. Using comprehensive (multiscale) dynamic/static analysis schemes, the Lw-pBTTT-C16/CB solution (10 mg mL-1) is shown to capitalize on rod associations and networking to form a gel, in stark contrast with its high-molecular-weight companion previously reported to form gels through hierarchical colloidal bridging. The present study reveals, however, that the molecular weight of pBTTT-C16 has a subtle impact on the gelation behaviors through the rarely recognized, contrasting supramolecular conformations (rod-like vs. wormlike) of the aggregate clusters fostered in the pristine solution. The ac conductivity nearly doubles as a result of improved (mesoscale) packing of cylindrical aggregates near the gel state as well as enhanced backbone rigidity of the constituting chains. Other distinguishing features include: (1) there is no real crossover of the dynamic moduli (G' and G'') upon increasing the temperature from gel (T = 15 °C) to solution (T = 80 °C) states. (2) The gel is about a hundredfold softer in dynamic modulus, yet more resilient with a fivefold increase in the yield strain. Both viscoelastic features are expected to greatly benefit the gel processability. (3) The coexistent microgels and cylinder (aggregate) bundles form a peculiar gel network that has not been reported previously with polymer or colloidal gels. The overall findings provide new mechanistic insight into the phenomenological effects of molecular weight for the pBTTT-Cn series in solution, sol, gel, and thin film.

On the number of tubes required to study oscillating vortices and frequency spectrums of tube arrays in cross flow

The oscillating vortices are of much practical importance in the analysis of the fluid-induced vibrations in cross-flow of a steam generator. However, the investigations on the vortex shedding, unsteady lifts, frequency spectrums, and the required number of tubes to study the phenomenon are very limited. In this work, a series of numerical experiments of a triangular array of tubes with a pitch ratio of 1.633 have been performed. The lift coefficients of the tubes were monitored to examine the effects of the numbers of tube rows and columns on the flow and fluid dynamics. The Fast Fourier Transform (FFT) method was used to figure out frequency spectrums of lifts of the cylinder bundle. Results show that the oscillating vortices generated by the tube arrays have greatly enriched the frequency spectrums. On the basis of the investigation of the unsteady lift performances, vortex shedding of tube arrays, eleven columns and eight rows were recommended. Furthermore, the fluid induced vibrations of a cylinder were investigated, and a fluid dynamics enhancement was observed.

Orthotropic hydraulic permeability of arrays of parallel cylinders.

Approximate analytical methods are presented to calculate the overall orthotropic hydraulic permeability of a flow with low Reynolds number, passing through a bundle of parallel circular cylinders. Two particular distributions are considered: (i) arrays with ordered rectangular lattices and (ii) irregular nonrandom distributions for which the unit cell cross sections are elliptical. The standard unit cell models, originally developed by Happel and Kuwabara for a random distribution of cylinders, are adapted to the case of nonrandom distributions. The drag force on a representative cylinder in a direction perpendicular to its axis is obtained based on the standard unit cell model: the actual unit cell of rectangular or elliptical cross section is replaced with an "equivalent" cylindrical unit cell of diameter equal to the maximum width of the actual unit cell. Using the obtained drag forces and referring back to the original geometry of the unit cell, closed-form approximate expressions for the overall permeabilities in the perpendicular directions are obtained. Numerical comparisons with more sophisticated approaches confirm the good efficiency of the presented approach, especially in the range of low solid volume fraction, i.e., of high porosity. Previous studies have revealed that, for the parallel fluid flow, the variation of permeability with aspect ratio (or in general the lateral arrangement) of parallel cylinders is generally weak. These observations suggest that Happel's model for parallel permeability in a random distribution of cylinders could be a good approximation for parallel permeabilities in nonrandom distributions with the same volume fraction.