Tube Outer Diameter Research Articles

Mechanical behavior of TOBs bolted T-stubs with thick arc-shaped flange to steel tube under tension: A numerical and theoretical investigation

The Thread-fixed One-side Bolt (TOB) is a novel fastener proposed in recent years that can easily connect steel beam to circular tubular column through an arc-shaped endplate. Based on the component method, the tension zone of the steel beam to circular column joint can be substituted by the TOBs bolted arc-shaped T-stub to circular steel tube connection. Following the experimental study on such connections in tension reported previously, the tensile behavior of the TOBs bolted T-stubs with thick arc-shaped flange to steel tube connection is further investigated numerically and theoretically in this paper. Based on a validated Finite Element (FE) model, parametric studies are conducted to explore the effects of critical parameters on the mechanical performance of the connection, including the wall thickness and outer diameter of the steel tube, bolt diameter, bolt layout, and tube length. A total of four failure modes appear in the FE analysis, which are (1) complete yielding failure of tube wall, (2) thread shear failure with yielding of tube wall, (3) thread shear failure, and (4) bolt shank failure. The diameter and wall thickness of the steel tube are the main parameters affecting the tensile behavior of the connection. In addition, based on the theoretical investigation, design methods are proposed to predict the initial stiffness, yield strength, and ultimate strength of the connection under different failure modes. The design methods are evaluated by comparing the predicted results with the FE results, which show good agreement.

The Tritube: Facilitating Upper Airway Surgery With an Ultrathin Cuffed Airway Device.

The Tritube is a narrow-bore cuffed tracheal tube (outer diameter 4.4 mm and inner diameter ~2.4 mm) that permits effective alveolar gas exchange using flow-controlled ventilation. Constant gas flow delivers physiological minute volumes, within preset pressure limits, and applies suction to the airway during expiration. The technique has attracted interest for laryngotracheal microsurgery as it provides superior surgical exposure and avoids many of the complications associated with high-frequency jet ventilation. Cuff inflation protects the lower airway and produces a motionless operating field. We describe the structure of the device, discuss its benefits, and suggest how it should be used clinically.

Optimization of heat transfer performance of a micro‐bare‐tube heat exchanger using a genetic algorithm

AbstractThis study presents the optimization of the heat transfer coefficient of a micro bare tube heat exchanger. A physical and mathematical model of a micro bare tube heat exchanger was built in Matlab using the simplified ε‐number of transfer unit method. Using a temperature of minus 30°C and a 0.5–1.0 mm tube outer diameter, a 1.7–8.0 mm longitudinal tube pitch, a 1.7–5 mm transverse tube pitch, and a 1.0–5.0 m/s velocity at minimum free flow area, with carbon dioxide as the refrigerant, a comparative variation analysis was performed to optimize the heat transfer coefficient of a micro‐bare‐tube heat exchanger. The results demonstrate that the heat transfer coefficient increases as the inlet air velocity is increased from 1.0 to 5.0 m/s, with a final gain of 93.17%. The growth rate of the heat transfer coefficient steadily decreases with increasing inlet air velocity and gradually approaches zero. The effect of the gradual decrease of the tube outer diameter from 1.0 to 0.5 mm on the heat transfer coefficient is 22.52% greater than that of the gradual decrease of the transverse tube pitch from 2.2 to 1.7 mm. The study also carried out an optimization analysis on the distribution of four different variables in the heat exchanger. With the use of a genetic algorithm, the study found an optimal distribution to maximize the heat transfer coefficient. The following parameter values resulted in the maximum heat transfer coefficient: a maximum inlet air velocity of 5.0 m/s, a minimum tube outer diameter of 0.5 mm, a 1.7 mm longitudinal tube pitch, and a 1.7 mm transverse tube pitch.

Prediction of thermal conduction of energy piles using various machine learning models

ABSTRACT The global energy crisis has led to a shift towards sustainable energy sources, such as geothermal energy, which can be efficiently used in energy piles, walls, and tunnels. This paper compares six machine learning algorithms for predicting the thermal performance of energy piles. A random 80:20 split of collected data points from the literature was used for training and testing. The input parameters were the number of tubes, inner and outer tube diameters, tube thermal conductivity, pile diameter, pile thermal conductivity, and soil thermal conductivity. The output was energy pile thermal conductance. Among all the ML models used for training and testing, the Gaussian Process Regression (GPR) model outperforms with the highest R2 value of 0.994 and RMSE of 1.886. After sensitivity analysis, the thermal conductivity of the pile was the key factor reducing energy pile thermal resistivity, followed by the number of U-tubes and pipe diameter.

Optimization of the First-Step Drawing Parameters for Platinum-Clad Nickel Bar Based on FEM Simulation

The first-step drawing process of the platinum-clad nickel composite bar was numerically simulated using DEFORM 3D finite element analysis software. The Taguchi method was used to study the effect of the first-step drawing parameters (the semi-angle of die α, the friction coefficient between the platinum tube and die μ1, the friction coefficient between the platinum tube and nickel rod μ2 and the outer diameter of the original platinum tube D) on the effective stress of platinum-clad nickel bar. Then, the optimal combination of parameters (D = 7.55 mm, μ1 = 0.2, μ2 = 0.3, α = 3°) was obtained. Furthermore, the results of the deformation behavior, cladding behavior, stress effectiveness and the distribution of the damage of the composite bar using optimization schemes were compared and analyzed with Numerical Simulations 8, which showed the worst result. Meanwhile, the experimental results were in general agreement with the simulation results of optimal combination of parameters, indicating that our simulation results are plausible. This has certain guidance significance to improve the quality of platinum-clad nickel composite wires in actual production.

A single long NiTi tube compressive elastocaloric regenerator: experimental results

Elastocaloric cooling is an environmentally friendly alternative to the current vapor-compression refrigeration technology, and the development of an efficient operation strategy is significant for its commercialization. In this article, the cooling performance including the temperature span, specific cooling power, and coefficient of performance for a novel single long NiTi tube compressive elastocaloric regenerator (tube outer diameter 5 mm, wall thickness 1 mm, and initial length 305 mm) was comprehensively characterized under different operation parameters (operation cycle time, loading/unloading time, heat transfer fluid timing, flow time, and utilization). The single long NiTi tube compressive elastocaloric regenerator achieved maximum temperature span, specific cooling power, and coefficient of performance of 5.7 K, 135 W·kg−1, and 4.7, respectively under an applied strain of 2.5%. It was found that the most important factors for obtaining a good cooling performance of the single long NiTi tube compressive elastocaloric regenerator were a short operation cycle time, a proper heat transfer fluid timing, and a proper heat transfer fluid utilization. The dependences of the temperature span on the cycle time and heat transfer fluid utilization factor were in agreement with the existing experimental data for a parallel plate tensile elastocaloric regenerator. A thinner tube wall thickness and advanced cross-section geometry for the regenerator may further improve the cooling performance of the compressive elastocaloric regenerator.

Identification of Anisotropic Coefficients in the Non-Principal Axis Directions of Tubular Materials Using Hole Bulging Test.

We propose an experimental method to identify anisotropic coefficients in non-principal axis directions of thin-walled tubes. The method involves extracting specimens from the parent tubes and machining a hole in the axial center. The specimens are then inserted into a tube without a hole. The inner diameter of the specimen is theoretically equal to the outer diameter of the inner tube. The double-layer tube undergoes free bulging under internal pressure in our self-developed experimental equipment, with the hole on the specimen expanding simultaneously. The stress states around the hole are uniaxial, and the hole deformation can reflect the anisotropic plastic flow characteristics of the tube. Furthermore, based on the information obtained from the proposed experimental method, a hybrid numerical-experimental method was used to identify the anisotropic coefficients of tubes. Through FE simulations, the relationships between the thickness, stress, and strain states around the hole, the hole shape, and anisotropic coefficients of non-principal axis directions are revealed, and the factors that affect the hole deformation are analyzed. Finally, the hole bulging experiments and FE simulations of AA6061-O extruded tube were conducted, and modeled with Hill48 and calibrated by uniaxial tensile and hoop tensile tests. Its in-plane anisotropy coefficients in any direction are given for the first time which first increase and then decrease from 0° to 90°, reaching a maximum of 1.13 in 60° and a minimum of 0.69 in 0°. This work can provide the key experimental data for establishing an accurate anisotropic plastic constitutive model of thin-walled tubes.

Lateral crushing behavior of tubular lattice structures with triply periodic minimal surface architectures

Tubular lattice structures had attracted significant attention due to their remarkable mechanical performance and lightweight, but there had been few research on their lateral crushing behaviors. In the present work, a novel tubular lattice structure with triply periodic minimal surface (TPMS), named TPMS-T, was manufactured to examine its energy absorption characteristics under lateral crushing through experiments and finite element (FE) simulations, with three types of unit-cell configurations considered for comparison. The numerical predictions of deformation modes and energy absorption responses were in good agreement with the corresponding experimental results. The energy absorption characteristics of three types of TPMS-T were further compared against the single circular tube (SCT) and typical nested tube systems with the same mass and outer size. It was found that TPMS-T exhibited superior crashworthiness performance than the corresponding SCT and typical nested tube system counterparts. The specific energy absorption (SEA) of three types of TPMS-T exceeded that of corresponding SCT by 70% to 133%, and fourfold-tube nested system (FT) by 24% to 61%, respectively. The influence of the relative density, tube thickness and tube outer diameter on the crushing behaviors of TPMS-T was numerically investigated to further understand the crushing mechanism of TPMS-T under lateral crushing. Results showed that the energy absorption performance exhibited an increase trend with increasing the relative density, and crashworthiness indicators could be expressed as a power function of the relative density. Moreover, the tube thickness and tube outer diameter had a large influence on the energy absorption capacity of TPMS-T. Finally, the multi-objective optimization design was further performed to obtain optimized TPMS-T configurations subjected to lateral crushing. The present work was expected to provide researchers and engineers with insights into the design of TPMS-T for structural crashworthiness applications.

Structural and electronic properties of double-walled zigzag and armchair Zinc oxide nanotubes

• Stability and electronic properties of DWZnONTs based on DFT investigated. • (4,4)@(n,n) and (5,5)@(n,n) and (7,0)@(n,0) and (6,0)@(n,0) DWZnONTs considered. • (n,n)@(n+5,n+5) and 8, (n,0)@(n+8,0) with inter-wall distance of about 4.6 and 4.3 Å are the most stable structures. • All zigzag and armchair nanotubes are semiconductors having a direct bandgap. • Bandgap increases by increasing inner and outer tube diameters and inter-wall distances. • The bandgap of double-walled ZnO nanotubes is smaller than that of their single-walled nanotubes. In this paper, we have investigated the stability and electronic properties of double-walled ZnO nanotubes (DWZnONTs) based on density functional theory (DFT) with the SIESTA package. The calculation have been performed on the armchair (4,4)@(n,n) and (5,5)@(n,n) DWZnONTs with (n=9 to15) and the zigzag (7,0)@(n,0) and (6,0)@(n,0) with (n=14 to 20). The stability calculation of DWZnONTs shows that the armchair and the zigzag DWZnONTs with difference chirality of 5, (n,n)@(n+5,n+5) and 8, (n,0)@(n+8,0) and inter-wall distance of about 4.6 and 4.3 Å are the most stable structures, respectively. Considering the electronic band structure points that all zigzag and armchair nanotubes are semiconductors having a direct bandgap. Moreover, it is revealed that the value of the bandgap increases by increasing inner and outer tube diameters and inter-wall distances, and the process of change at higher inter-wall distances be almost constant. Our results show that the inter-wall coupling diminishes the energy gap in semiconducting DWZnONTs. We found that the energy gap of DWZnONTs depends on the structure of the inner and outer walls. The consequences of this investigation can certainly be helpful in future experimental studies.

Finite element analysis of Steel – Concrete – Steel double skin tubular columns under axial loading

Composite construction with columns made of double-skin steel tubulars filled with concrete (CFDST) which have a concrete infill between the exterior and interior tubes made of steel. The thickness of steel tube, hollow section ratio and the concrete stress–strain are the variables that affect the axial load behaviour of Steel-Concrete-Steel Double Skin Tubular Columns. This study's goal is to use the Abaqus 6.20 software to examine the axial behaviour of CFDST columns. The hollow section ratio is explored by altering the inner diameters (26.9 mm, 33.7 mm, and 43.4 mm) while maintaining a constant outer tube diameter of 114.3 mm in the parametric investigation on the columns. The hollow section ratio of 0.24 proves to be most effective and has increased load carrying capacity.

Convective condensation of R134a and R1234ze(E) inside microfin tube

Environmental concerns are forcing the replacement of the commonly used refrigerants and finding new fluids is a top priority. The hydro-fluoro-olefin (HFO) R1234ze(E), because of its smaller global warming potential (GWP) and shorter atmospheric lifetime, replaced R134a. Accordingly, for HVAC systems design, a detailed knowledge of the thermo-fluid-dynamic characteristics of the fluids and reliable predictive models are required. To improve the understanding, R134a and R1234ze(E) were employed in convective condensation experiments (saturation temperature Tsat = 35°C, mean quality xm = 0.1~0.9, quality changes Δx = 0.05~0.6, mass flux G = 43~444 kg·m−2s−1) inside a microfin tube (outer diameter D = 9.52 mm, fin number n = 60, fin height H = 0.2 mm). The results were used for two goals: the former is the comparison of the heat transfer features of the two fluids, while the latter aims at testing the performance of prediction models available in the open literature. At the saturation temperature T = 35°C, the two fluids show small differences in the thermal properties so that, as expected, the experiments highlighted a very similar behavior in the typical operating conditions of HVAC systems. In fact, for all the operating conditions marginal differences were observed in the pressure drop, the heat transfer coefficient and the flow pattern maps. The issue of prediction reliability, however, is still open. Actually, not all the models achieving good results for R134a show the same performance for R1234ze(E), especially for the pressure drop.

Buckling prevention of a single long NiTi tube compressive elastocaloric regenerator

Superelastic NiTi tubes have been used in elastocaloric coolers due to the good balance between mechanical stability and heat transfer efficiency, and the tube length increase is crucial to the driving force reduction and total cooling power increase of the coolers. The key challenge to adopt long superelastic NiTi tubes in compressive elastocaloric coolers is to prevent long tubes from buckling. In this article, a buckling prevention method of entraining a single long tubular material into a rigid and thick outer shell was proposed. The enhancement in the maximum compression load of a single long tubular material with an outer shell compared with the bare material was derived using the energy method. The proposed buckling prevention method was validated by compression experiments using a single long stainless-steel tube and outer shells of different materials and outer diameters. The buckling prevention method was successfully applied to a single long polycrystalline superelastic NiTi tube (outer diameter 5 mm, wall thickness 1 mm, and initial length 305 mm) in a layered-structured compressive elastocaloric regenerator. Several stress rise-drop-recover processes due to the friction and sliding of the tube were observed in the training, and the dependences of the stress-strain response of the tube on the applied stress and strain rate were also investigated. An elastocaloric cooler based on the single-long-tube compressive elastocaloric regenerator was constructed and it reached the highest temperature span, specific cooling power, and COP values of up to 5.7 K, 150 W∙kg−1, and 4.0, respectively. The results of the article are significant for developing large-power elastocaloric coolers.

Utilizing waste heat gasoline engine in the design and fabrication of a fin and tube evaporator for the Organic Rankine Cycle (ORC)

The excessive consumption of fossil fuels is causing environmental problems, which can be addressed by utilizing renewable energy sources such as hydro energy, biomass, solar heat, geothermal, and waste heat. In particular, the exhaust gas from gasoline engines presents an opportunity for energy recovery, as only 25% of the energy is utilized while the remaining 75% is wasted. A fin and tube type evaporator was designed, manufactured, and tested to utilize this exhaust gas in an Organic Rankine Cycle (ORC) system. The evaporator was designed with an outer tube diameter of 9.525 mm and a total tube length of 41.4 m, featuring 90 tubes and 135 fins with a total area of 14,325 m2. It achieved an average effectiveness of 94.33%. The results showed that the waste heat from the exhaust gas of a gasoline engine could be used as a source of energy in an ORC system with an efficiency of 2.13%. It results in 7.02 kJ/s of energy absorbed by the evaporator and a net power generated of 0.15 kJ/s. This research demonstrates the potential for utilizing waste heat from gasoline engines as an energy source to generate electricity.

Transkritik Soğutma Çevrimlerinde Gaz Soğutucu Geometrisinin Sayısal Optimizasyonu

Traditional halocarbon – based refrigerants tend to considerably increase global warming and ozone depletion factors. Therefore, CO2 is fast becoming a key instrument as a natural refrigerant which was widely applied and attracted the consideration of the research community. The gas cooler is an important component in the CO2 transcritical refrigeration system and plays a key role in the performance due to the determination of operating pressure consequently power consumption. In this research, the performance characteristics of a CO2 gas cooler having wavy fin geometry, which is currently used in industries such as air conditioning, automotive and aviation, was determined experimentally in a calorimetric test room. The experimental results was used as benchmark data to validate the three – dimensional numerical model. Laminar model and realizable k - ɛ turbulent model were employed for analyses. Moreover, the second order upwind scheme was considered to discretize momentum and energy equations. Accordingly, a multi-objective optimization process has been performed employing Response Surface Method (RSM) to determine the optimum wavy fin geometry in CO2 transcritical refrigeration system. Four geometrical parameters namely longitudinal pitch, half transverse pitch, tube outer diameter, and fin pitch of the gas cooler were optimized. According to results, the new optimized CO2 gas cooler exhibited lesser pressure drop and higher heat transfer capacity in comparison with the tested gas cooler geometry used in the industry. It was found that the overall heat transfer coefficient enhancement is between 5.4 – 12.2 % while pressure drop decreases about 175.08 – 188.58 % for three different inlet velocities.

Thermo-hydrodynamic performance of tubular pulsating heat pipes with integral sintered powder wicks

The untraditional copper tubular pulsating heat pipes with integral inner-wall sintered powder wicks (PHPWWs) were fabricated to improve the thermal performance of the traditional pulsating heat pipes with no wicks (PHPWNWs). An experiment was performed to investigate the start-up and quasi-steady thermo-hydrodynamic characteristics of the PHPWWs and compare them with the PHPWNWs. The results indicate that, the wicks can improve the nucleation boiling in the evaporator to enhance the thermal driving force and provide additional capillary action to facilitate the liquid backflow to the evaporator. Consequently, differing from the PHPWNWs, the PHPWWs are able to work at the horizontal orientation, and their internal fluid flow motions ‘abnormally’ become smoother with decreasing inclination angle from 90° to 0°. In addition, PHPWWs has the lower start-up and quasi-steady-operation evaporator temperature as well as better thermal performance and gravity adaptability when compared with the PHPWNWs with similar inner and outer tube diameter. The operating principle of the PHPWW, especially the driving principle of the internal fluid, is determined by the cooperation and competition between those of the traditional PHPWNW and the conventional sintered wick heat pipe, which is affected by the inclination angle and particularly the tube inner diameter.

Behavior of thread-fixed one-side bolts bolted T-stubs with arc-shaped flange to steel tube under tension

Tensile tests and Finite Element (FE) analysis were conducted on the Thread-fixed One-side Bolts (TOBs) bolted T-stub with arc-shaped flange to steel tube in this paper. Critical parameters were determined as the thickness of tube wall, the outer diameter of steel tube, the thickness of arc-shaped flange, and the center angle between bolts. Test results revealed that the connection would encounter three typical failure modes, which were: failure mode 1, thread shear failure with yielding of tube wall; failure mode 2, complete yielding failure of tube wall; failure mode 3, thread shear failure with yielding of T-stub arc-shaped flange. Developed FE models are verified and used to analyze the yield line pattern of tube wall, the hoop stress distribution of cross-section of tube wall, and the shear acting on bolt shank. Based on the experimental and numerical results, preliminary analytical models and design methods are proposed to estimate the tensile yield strength of specimens under different failure modes.

DESIGN OF HEAT EXCHANGER FOR THE PRODUCTION OF SYNTHESIS PbO PARTICLES

This study aims to develop and analyze the design of heat exchangers (HE) in the synthesis of PbO particles using a single precursor method. This type of HE shell and tube one-pass is designed to be simple. The specifications of HE equipment are shell length 1.5200 m, shell diameter 0.1361 m, outer tube diameter 0.0334 m, and thickness 0.0243 m. Then the calculation is done manually using the Microsoft Excel application. The results showed that the HE shell and tube design with the one pass type has a laminar flow, with an effective value of 84.66%. Therefore, this heat exchanger with shell and tube one meets the requirements and standards based on effectiveness, but without considering the fouling factor. The results of this analysis can be used as a learning medium in the design process, analysis of heat exchanger performance, and operating mechanisms.

Study on performance of working model of heat exchangers

The most often utilized heat exchangers are tubular heat exchangers. Kern Method is one of the ways for thermally designing a shell and tube heat exchanger. A small scale 1, 2-shell and tube heat exchanger is fabricated after designing, in this paper. The experimental value of the overall coefficient of heat transfer is validated with the experimental value computed using the Kern Method, as well as to values found in the literature. The effects of tube outer diameter and tube thickness on the various parameters of a 1–2 tubular heat exchanger were investigated. The fluctuation of coefficients of heat transfer on the tube and shell sides, Reynolds numbers, drop in pressure, and overall heat transfer heat transfer coefficients are found.

Shell and tube heat exchanger design for production graphene oxide nanoparticles from agricultural waste

Heat exchangers are used to transferring energy (heat), using fluids or gases, both hot and cold, from one area to another due to temperature differences. Almost all agricultural wastes serve as carbon products which are essential to produce graphene oxide, it is very possible to get graphene oxide by synthesizing it from agricultural waste which is expected to reduce the amount of waste on the earth. After carrying out the synthesis, it is necessary to test the characterization of the resulting product. The characterization stage requires a sintering process (20oC to 98oC) until the product is completely solidified. This research aims to design a heat exchanger that is highly effective in assisting the sintering process. For the design to be well-directed, several things must be done, such as calculating the main components (shell and tube) and designing a heat exchanger. Based on the TEMA standard and the use of simple calculations that refer to the attached calculation formula using Ms. Excel, hot and cold fluids used in this heat exchanger design are ethylene glycol and water. The length of the shell and tube as a whole is 5 m, the inner and outer shell diameters are 254 mm and 279.4 mm; the inner and outer tube diameters are respectively 22.09 mm and 25.40 mm. The calculation results show an excellent design effectiveness value of 86.14%. Continuous innovation in the design and materials of the heat exchanger can increase the effectiveness value to close to 100% so that it can help the graphene oxide synthesis process to make it cheaper and more efficient.

A statistical approach in the FEM simulation analysis of geometrical product specification during the cold tube drawing process

The cold drawing process produces high-quality tubes with precise dimensions, good surface quality, and higher strength due to cold forming. The tube drawing is used to reduce the cross section of the produced tubes. Depending on the reduction size, the outer diameter and wall thickness of the final tube changes. Due to the fact that cold drawing of tubes is mostly the last operation of production, it is necessary to pay attention to the process parameters and geometry of the forming tools. This paper presents a statistical evaluation of the influence of the wall thickness of the pre-tube, die diameter, and pre-tube diameter on the measured responses, which were the outer diameter and wall thickness of final tube, after the FEM simulations of the drawing process. For these purposes, a factorial design with three input factors was implemented. The goal of using the simulations was also to investigate whether the single-pass type of tube drawing would guarantee useful statistical results that could lead to significant time and cost reductions. The FEM simulations were executed using DEFORM software of Scientific Forming Technologies Corporation with Design of Experiment application module of this software. A factorial design of experiment has been processed in Minitab v. 17 software. The results show that most of the factors significantly influenced the response variables.