Circle Cross-section Research Articles

Comparisons on the thermal and entropic performance of helical tubes with varying cross-sections with constant wall temperature

This study investigates the thermal-hydraulic behavior of helical tubes with different cross-section types. The flow was considered to be in a turbulent flow regime, and the wall temperature of the tube was considered to be constant. Circle, horizontal oval, vertical oval, square, horizontal rectangle, vertical rectangle, equilateral triangle, and hexagons were eight cross-section types assessed in this study. Findings demonstrated that across the evaluated range of mass flow rates, cases with triangular cross-sections had the highest friction factor values. Also, it was observed that these cases have the largest and the most intense vorticity among all other cases. It was revealed that cases with sharp regions include vortices that increase the loss of kinetic energy. In circular cross-section and triangular cross-section examples, the Nu number was most varied. There is a 58% difference between maximum Nu values for circular and triangular cross-sections. The case with a circular cross-section and a mass flow rate of 2 kg/s exhibited the highest PEC factor value of approximately 1.001. Finally, it was determined that a circle cross-section is the best according to the first law of thermodynamics, but a triangular cross-section performed 52% better when compared to other cross-section forms according to the second law of thermodynamics.

Design and thermal analysis of the BPM-bellows assembly front-end photon block for Hefei Advanced Light Facility

The BPM-bellows front-end photon block with ellipse cross-sections has been designed for Hefei Advanced Light Facility (HALF). Such structure has lower longitudinal coupling impedances than the photon block with commonly-used circle cross-sections. In addition, two types of cooling structures have been designed, which are shared water-cooling pipe (cooling structure 1, CS1) and independent water-cooling tank (cooling structure 1, CS2), respectively. The CS1 is simple and space-saving, while the CS2 has better heat dissipation capability. In order to calculate power density on complex light-receiving surfaces, the Monte Carlo simulation tool, Synrad, was applied. By building finite element models and importing power density data from Syrand, the temperature and thermal stress distributions of photon blocks with two different cooling structures were calculated. The thermal analysis indicates that the maximum temperature (37.73°C) is located at CS1, but the maximum stress (16.28 MPa) is on CS2 due to the difference in structure and heat dissipation capability. Moreover, the maximum temperature and thermal stress values are far below the material criteria of CuCrZr. Therefore, the simple and space-saving CS1 is more suitable for HALF, which can reduce manufacturing costs and better satisfy the compact layout in the storage ring.

Research on the influence of different obstacle structures on the energy distribution characteristics of pulse detonation gas

In order to improve the gas energy conversion efficiency at the outlet of the pulse detonation combustor, numerical calculation methods were used to study the influence of three different cross-section obstacle structures of square, circle and trapezoid on the distribution characteristics of gas pressure potential energy, kinetic energy and internal energy in a single cycle at the outlet of pulse detonation combustor. The results show that: the expansion of pulse detonation gas mainly includes three-stages: primary expansion, secondary expansion, and over-expansion. Gas pressure potential energy, kinetic energy, and internal energy increase during the primary and secondary expansion stages, and decrease during the over-expansion stage. Pulse detonation combustor with trapezoidal cross-section obstacle structure has the smallest proportion of gas energy at the outlet of the combustor during the over-expansion stage and the highest proportion during the secondary expansion stage. Compared with square and circle cross-section obstacle structures, the gas energy distribution at the outlet of the pulse detonation combustor with trapezoidal cross-section obstacle structure is the easiest for turbomachinery to convert the gas energy.

Imbibition of Newtonian Fluids in Paper-like Materials with the Infinitesimal Control Volume Method

Paper-based microfluidic devices are widely used in point-of-care testing applications. Imbibition study of paper porous media is important for fluid controlling, and then significant to the applications of paper-based microfluidic devices. Here we propose an analytical approach based on the infinitesimal control volume method to study the imbibition of Newtonian fluids in commonly used paper-like materials. Three common paper shapes (rectangular paper strips, fan-shaped and circular paper sheets) are investigated with three modeling methods (corresponding to equivalent tiny pores with circle, square and regular triangle cross section respectively). A model is derived for liquid imbibition in rectangular paper strips, and the control equations for liquid imbibition in fan-shaped and circular paper sheets are also derived. The model is verified by imbibition experiments done using the mixed cellulose ester filter paper and pure water. The relation of imbibition distance and time is similar to that of the Lucas−Washburn (L−W) model. In addition, a new porosity measurement method based on the imbibition in circular paper sheets is proposed and verified. Finally, the flow rates are investigated. This study can provide guidance for the design of different shapes of paper, and for better applications of paper-based microfluidic devices.

Design-eligibility study of solar thermal helically coiled heat exchanging system with annular dimples by irreversibility concept

This is a numerical research that aims to design several helically grooved coils for solar water heating systems and compare them based on the irreversibility concept. To this end, helical coils with circle, square, horizontal elongated circle (HEC), and vertical elongated circle (VEC) cross-sections were annularly grooved for enhancing heat transfer rate. The Second law analysis in this study was performed based on several variables including flow rate (1–6 lit/min), geometrical, temperature (283–323K), and type of working fluid. Depth and distance of grooves were considered as geometrical parameters. Water, EG (CH2OH)2 (IUPAC name: ethane-1,2-diol), and Theminol-55 were used as heat transfer fluids. Selected fluids make a Pr range of 3.35–744. Various entropy-based indicators were used to select the most optimum condition. Moreover, the interactions between triple thermodynamic domains (energy, entropy, and exergy) were conceptualized. Results demonstrated that for all cases the highest entropy generation can be achieved in the higher flow rates (6 lit/min), also when groove depth and distance are, respectively, 1.3 mm and 20 mm. Case ''VEC'' has the lowest ratio of grooved dimensionless entropy to un-grooved dimensionless entropy.

Effect of Flow Channel Cross Section Shape on the Performance of Heat Storage Structure

A numerical simulation is carried out for the thermal storage process in a heat storage device with magnesia bricks as thermal energy storage medium. Three types of cross section shapes (square, hexagon, circle) of the flow channel are considered with the inlet air temperature as high as 1023K. The perssure drop, temperature distribution and temperature uniformity of the flow channel are obtained. The results show that the pressure drop of the flow channel with circle cross section is the lowest when the Reynolds number is less than 2300 (in this case the inlet velocity is 5m/s), While when the Reynolds number is more than 2300, the flow channel with square cross section has the lowest pressure drop. The thermal storage time of the heat storage device decreases with the increase of air velocity. The temperature distribution of the flow channel indicates that the flow channel with hexagon cross section has the best comprehensive performance.

BENDING WITH TORSION OF FIBER REINFORCED CONCRETE BEAM OF CIRCULAR CROSS SECTION

The article provides information about the tests of circle cross-section reinforced concrete beams made of high-strength steel-fiberconcrete on combined torsion and bending. Given information contains the main results: a diagram of the cracks with an indication of their opening width, the values of support reactions at the moment of cracking and at the moment before destruction. It was found that as the load is applied in beams made of high-strength steel-reinforced concrete, in the case of several cracks at the firststage, there is one crack increases. The beams are modeled in the design complex and given description of the main design parameters. The results of the calculation are presented and a comparative analysis of the results obtained with the experiments results. It is noted that the adopted models in the computational complexes require the development of subroutines and refinement

Analysis of a twisted double-pipe heat exchanger with lobed cross-section as a novel heat storage unit for solar collectors using phase-change material

In this paper, a twisted double-pipe heat exchanger containing phase change material is designed and analyzed as an energy storage unit in solar collectors. Since solar heat exchangers cannot store energy, a study of such devices is essential. The governing equations solving and numerical simulation were performed by Ansys 19 software in a 3D model based on enthalpy–porosity method and PRESTO! scheme. The effects of several parameters like pipe's position, twisting, and cross-section on the PCM melting in the storage unit have been investigated, which was unprecedented. The outcomes illustrate that vertical heat exchangers are less efficient and have 15.3% more melting time than horizontal ones. And, 3-lobed cross-sections comparing to circle cross-sections enhance the PCM melting by 6%. Moreover, a double-pipe helical coil or twisted pipe heat exchanger with a 3-lobed cross-section decreases the melting time. The reduction for the helical coil is 10%, while it is 14.6% for twisted pipe heat exchangers. Finally, we examined the twisted inner pipe with 2, 3, 4, and 5-lobed cross-sections. The achievements demonstrated that the 3-lobed twisted cross-section has the highest heat transfer surface and the melting time for 3-lobed is 1.5%, 5%, and 6% less than 2-lobed, 4-lobed, and 5-lobed.

Numerical analysis of ultimate load and crack propagation in a concrete beam with longitudinal small hole

This analytical study aims to investigate the flexural behavior of simply supported RC beams having longitudinal hole with circle cross section under monotonic two point loads. The commercial FE program ABAQUS was used for simulating and implementing the specimens behavior that tested experimentally in previous researches. The overall specimens investigated were thirteen RC rectangular beam specimen, the first one was solid while the others with longitudinal circular hole. The specimens with holes divided into three groups, each one has a specified hole diameter 25 mm, 40 mm, and 50 mm. The distance from center of hole to the top section face was variable where the hole would be completely in the stress block, below it, or partially within it. The validity of the simulated model were verified by comparing the available load deflection data with the implemented one, where good agreement were noticed. The simulated models could introduce the ultimate load, first cracking load and its propagation in addition to the maximum attended deflection. It is concluded that the existence of a longitudinal hole with a percentage of diameter to beam depth ratio below 20% with different positions from top surface of the cross-section to the center of the hole values caused decreasing in ultimate load not exceeding 5% compared with the solid beam.

Green methane production: Kinetic and mass transfer modeling in a batch process

One of the major issues in biomethanation studies, especially a batch strategy without mixing, is gaseous substrate mass transfer between gas and liquid phases. The strategy can be assumed as a simplified form of a stagnant underground gas reservoir. Hydrogen gas, as the limiting substrate, plays significant role in biomethanation. Being informed of hydrogen content diffused within the liquid phase for calculating percentage of active volume, help researcher to make a proper decision on bioreactor design or adjusting process parameters. For this purpose, a mass transfer modelling was developed which strengthened with a set of optimized biokinetic parameters. Parameter optimization was accomplished with the help of a predefined optimization algorithm and using a set of experimental data with the source of literature. Active volume calculation was successfully performed via the verified model and response surface methodology was served for maximizing it under variety of process conditions. It was found that the bioreactor height to width ratio significantly affected on active volume followed by pressure and temperature. In addition, working with a bioreactor with a circle cross section, in comparison with a square one, improved the maximum active volume up to 43% due to providing higher surface area for mass transfer. Sensitivity analysis verified the previous findings and revealed that higher pressures and temperatures linearly increased the active volume while increasing the bioreactor height to width ratio exponentially decreased the response. Furthermore, a wide bioreactor have potential to promote active volume up to 72% rather than a vertical one.

Influence of Geometry and Separation Walls on The Behaviours of Pull-out Pipe Piles Embedded in Sandy Soil

Predicting of piles capacity and their behavior is always an important and serious problem for a safe geotechnical engineering design. In the present study, experimental model tests have been conducted on a single steel pipe piles driven in sandy soil and subjected to pull-out force. The experimental tests were conducted on vertical open-ended piles with circular and square cross-sectional area and three various diameters 3 cm, 4 cm and 5 cm in a steel soil box have been used. The tested pile’s model has embedment with three penetration ratios (PR=L/D) of 10, 15 and 20. All tests were done in medium density soil (Dr = 50%) with open ended pipe pile to study the effect of pile geometry on pile behavior, and three other tests were conducted on the 5cm diameter and 10 penetration ratio in medium soil density to study the importance of addition of separating wall. The study discovered that the capacity of single piles with circle cross-section area under pull-out force increasing by 211% and 458% with the increasing of pile diameter (width) from 3cm to 4cm and 5cm respectively, and increasing by 210%, 448% and by 112%, 288%. Also, by 79% and 211% with increasing penetrating ratio (PR) from 10 to 15 and 20 for diameters 3cm, 4cm and 5cm respectively, with respect to reference pile. And the same behavior for square cross-section pipe pile, when the pull-out capacity increasing with the increase of pile width and penetration ratio due to the increasing in the friction area. Besides that, It was also found that the separation walls increased the coefficient of lateral pressure in addition to the friction area. At the same time, there are an optimum number of separation walls that can be used to increase the pile pull-out capacity and that when using three separation walls.

Energy absorption and deformation pattern analysis of carbon fibre reinforced composite crash box under frontal load model

Crash boxes as a passive safety system in vehicles had been developed to produce high energy absorption performance. This study investigates the influence of cross-section geometry and fibre orientation angle on the composite crash box design to determine deformation pattern and energy absorption performance. The cross sections studied are circles and squares with variations in fibre orientation angles 0°, 15°, 30°, 45°, 60° and 75°. Carbon Fibre Epoxy CFS003 / LTM25 Prepegs with the type of plain woven fibre used to model crashbox structures. The computer simulation test model was carried out using a frontal load model with velocity of 7.76 m s−1. The results showed a circle cross-section at each variation of the orientation angle has a higher energy absorption than a square cross-section. Deformation patterns in each model show different characteristics including fragmentation mode, lamina bending, brittle fracturing, and local buckling as well as a combination of several patterns. The highest energy absorption obtained in the C60 model was 3.664 kJ with Specific Energy Absorption (SEA) of 36.799 kJ kg−1 and a CFE value of 0.59. While the lowest energy absorption occurs in the S45 model with 1.287 kJ which has a SEA value of 12.667 kJ kg−1with a CFE of 0.49. The CFE value indicates that the model with a circular cross section has better crushing stability than a squarecross section.

Refinement of the Maxwell formula for a composite reinforced by circular cross-section fibres. Part II: using Pad\xe9 approximants

The effective properties of the fiber-reinforced composite materials with fibers of circle cross section are investigated. The novel estimation for the effective coefficient of thermal conductivity refining the classical Maxwell formula is derived. The method of asymptotic homogenization is used. For an analytical solution of the periodically repeated cell problem the Schwarz alternating process (SAP) was employed. Convergence of this method was proved by S. Mikhlin, S. Sobolev, V. Mityushev. Unfortunately, the rate of the convergence is often slow, especially for nondilute high-contrast composite materials. For improving this drawback we used Padé approximations for various forms of SAP solutions with the following additive matching of obtained expressions. As a result, the solutions in our paper are obtained in a fairly simple and convenient form. They can be used even for a volume fraction of inclusion very near the physically possible maximum value as well as for high-contrast composite constituents. The results are confirmed by comparison with known numerical and asymptotic results.

How does the shape and surface energy of pores affect the adsorption of nanoconfined fluids?

AbstractWe report a systematic molecular simulation study of the behavior of Lennard–Jones fluids inside nanopores of diverse shapes, focusing on the effect that the pore geometry and the local energetic environment have on the adsorption isotherms. Infinitely long pores with polygon (triangle, square, pentagon, hexagon, octagon, decagon, and circle) cross sections are considered. Three different pore sizes commensurate with the molecular diameters along with three different values of fluid–solid energy interactions are chosen to perform Grand Canonical Monte Carlo simulations at a subcritical temperature. Overall, the effect of nanoconfinement on the adsorption of fluids is seen to be a delicate balance between the geometric packing restrictions imposed by the hard cores of the molecules and the surfaces, the excess adsorption induced by the presence (or absence) of energetically favored “hot spots” and the overall ratio of surface/bulk fluid volume present in the pore.

Crashworthiness of CFRP/aluminum alloy hybrid tubes under quasi-static axial crushing

Carbon fiber reinforced plastic (CFRP)/aluminum alloy hybrid tubes is a lightweight and energy absorption structure in the automobile design. In this paper, simulations and tests are conducted to study the crashworthiness of the hybrid tubes under the quasi-static axial crushing. According to the research on the effect of cross section shapes on the crashworthiness, it can be found that the specific energy absorption (SEA) and the crushing force efficiency (CFE) of the circle cross section are the largest. For the CFRP/aluminum alloy hybrid tubes with the circle cross section, the finite element analysis (FEA) model under the quasi-static axial crushing are built, and the specimens for tests are manufactured. The affecting factors on the crashworthiness are studied including the length, the thickness ratio of the aluminum alloy to the CFRP (tm/tc), the layer number, the fiber direction and the proportion of the axial fibers to the circumferential fibers. The load–displacement curves and the crashworthiness indicators of the different affecting factors are obtained, and how the factors affect the crashworthiness are discussed. In addition, the process of the quasi-static axial crushing, the failure modes and the energy absorption mechanisms are analyzed. This study provides a reference for the application of the CFRP/aluminum alloy hybrid tubes in the automobile lightweight and crashworthiness design.

Multi-objective crashworthiness optimization of thin-walled multi-cell tubes with different wall lengths

Thin-walled tubes are extensively used in the automotive industry because of their high energy absorption capacity and lightweight advantages. These structures are expected to have high energy absorption and low peak force during any collision. In this study, to obtain low peak crushing force, different wall lengths have applied to the thin-walled tubes. Different wall lengths have investigated using doubly-walled walled, inner multi-cell walled and multi-cell walled tubes obtained from square, hexagon, octagon and circle cross-sections. To evaluate crashworthiness performance dynamic impact analyses at a constant velocity are carried out using the non-linear explicit Finite Element (FE) code Radioss. According to the FE results, tubes with different wall lengths give lower peak crushing force (PCF) of up to 36% compared to normal tubes. On the other hand, in tubes with different wall lengths, there is a decrease of up to 6% in specific energy absorption (SEA) compared to normal tubes. Thus, considering the decrease of the PCF, the advantage of tubes with different wall lengths is presented. Optimization studies have carried out for the second type octagonal tube with different wall lengths (O2G) and the third type octagonal tube with different wall lengths (O3G) which give better SEA and PCF values between all tubes.

Comparison Of Energy Absorption And Pattern Of Deformation Material Crash Box Of Three Segments With Bilinear And Johnson Cook Approach

The study aimed to find out the comparison of energy absorption and pattern of deformation material crash box of three segments using software simulation FEM-Based (finite element method) and bilinear and Johnson cook approach. The crash box made with a three-segment circle cross section using Al 6063-T5 material, 1.2 mm thick, 162 mm length and chamfer angle between 45º segments. Simulation on the crash box was done by frontal direction collision simulation using an impact factor of 200 kg and impact speed of 7.67 m / s. The findings showed that the value of energy absorption in the crash box material with bilinear approach was higher of 8954 J compared to the crash box with the Johnsoncook approach of 8859 J. The patterns of deformation of bilinear crash box tended to form concertina and mixed patterns (concertina + diamond).

The Effect Of Material Exposure Variations On Energy Absorption Capability And pattern Of Deformation Material Of Crash Box Of Three Segments

AbstrakCrash box is part of the supportingcomponents on vehicle safety, especially cars. The crash boxis designed to reduce the occurrence of driver’s injuries due to collisions. This study aimed to determine the capability of energy absorption and deformation patterns in the crash box using a three-segment circle cross-section. The research method was quasi-experimental with a simulation using Finite Element Method software. The crash box simulation carried out with a 200 kg impactor on a speed of 7.67 m/s. The independent variable in this study is the material exposure variation in the crash box using steel-aluminum-steel and aluminum-steel-aluminum. The dependent variables were energy absorption, force reaction and deformation patterns occurring in the crash box. Based on the simulation results, the values ofenergy absorption was 82452 J and force reaction was 1127700 N in the crash box of steel-aluminum-steel material. Meanwhile, the crash box material of aluminum-steel-aluminum has an energy absorption value of 236210 N, force reaction of 12432 J and a better and more stable on deformation pattern.

ТЕПЛООБМЕН ВО ВРАЩАЮЩЕМСЯ ГЛАДКОМ КРУГЛОМ КАНАЛЕ И ВЛИЯНИЕ НА ЕГО ИНТЕНСИВНОСТЬ ВИХРЕВОГО ТЕЧЕНИЯ

The paper deals with the analysis of heat transfer intensity in a rotating smooth channel, which simulates a cooling channel of rotating blade of the gas turbine engine. A circle cross-section channel with a diameter of 6 mm and length of 80 mm was chosen as the base variant. The calculations of heat transfer in rotating and stationary channels were carried out, which allows estimating the influence of vortex flow on the intensity of heat transfer. Rotation of the channel was simulated by means of domain rotating. The rotation speed of the test channel is 7400 rev/min. Axis of rotation is at a distance of 0.49 m from the inlet section of the channel. Pressure and temperature were specified as inlet boundary conditions: 1040000 Pa and 733 K, respectively. The mass flow rate of 0.02 kg/s was specified as outlet boundary conditions. The computations were performed by solving the Reynolds-averaged Navier-Stokes equations (RANS method) using an SST (Shear Stress Transport) turbulence model. The air ideal gas was used as the working medium. The calculation was performed taking into consideration the Buoyancy effect. Verification of heat exchange calculation model in the rotary channel of the gas turbine engine rotor blade according to experimental data is carried out. The boundary conditions at the input and output of the channel were set in such a way that the flow parameters in the calculation corresponded to the experimental characteristics. The resulting numerical calculations of the temperature distribution and Nusselt Numbers are qualitatively and quantitatively consistent with the experiment. The distribution of Nusselt Numbers on the front and back walls for rotating and non-rotating channels, as well as the dependences of the relative tangential velocity on the relative channel length, were estimated. It has been shown that average Nusselt Number on the leading wall of the rotating channel is the same with the wall of the static channel, but detail Nu distribution over rotating leading wall undergoes considerable modification. Average Nusselt Number on the trailing wall of the rotating channel is higher than on the wall of the static channel, but the detail Nu distribution pattern on the rotating trailing wall generally follows the static result.

Apparent permeability model for shale oil transport through elliptic nanopores considering wall-oil interaction

The shale oil transport mechanisms in inorganic matrix (iOM) and organic matrix (OM) nanopores are still not well understood, and the shape of nanopores is complex and diverse. Therefore, it is of critical importance to clarify the oil transport mechanisms in nanopores with different cross-sectional shapes. In this study, a model for oil transport is proposed to analyze the apparent permeability and flow enhancement based on the Hagen–Poiseuille equation. The proposed model takes into account the near-wall oil flow in iOM nanopores and the adsorbed oil flow in OM nanopores. In addition, the effects of different circular and elliptical cross-sections of nanopores and size of nanopores are considered. The proposed model is validated with the simulation data of non-equilibrium molecular dynamics and the Lattice Boltzmann method. The results indicate that: (1) the flow enhancement in iOM and OM nanopores first decreases rapidly and then stabilizes with an increasing length of semi-major axis a and semi-minor axis b because of the decreasing wall-oil interaction, and the apparent permeability of iOM increases as the axis a and axis b increase. When axis b is 2 nm, the permeability of OM increases with an increase in length of axis a, as length of axis b becomes larger, the permeability first decreases and then increases; (2) in iOM and OM nanopores, with a constant cross-sectional area, compared to nanopores with circle cross-sections, the flow enhancement becomes greater in nanopores with elliptical cross-sections, and the higher the ratio ω of the length of axis a to that of axis b, the greater the flow enhancement. The permeability of iOM nanopores decreases with an increasing ratio ω, while the permeability of OM nanopores first decreases and then increases. When the cross-sectional area is small, the permeability of OM nanopores increases with an increase in ratio ω, and as the cross-sectional area becomes greater, the permeability decreases with an increasing ratio ω. The proposed model demonstrates that elliptical cross-sections of nanopores can provide theoretical support for the development of shale oil reservoirs.