High-performance Tube Research Articles

Numerical and experimental investigation on condensing heat transfer and flow characteristics outside horizontal dentate-fin tubes

The condensing flow and heat-transfer characteristics around dentate-fin tubes were investigated using numerical and experimental methods. Using the examined computational model, the film flow characteristics and condensing heat-transfer coefficient of the dentate-fin tubes in the circumferential and axial directions were analyzed. Comprehensive information regarding the condensation process in high-performance tubes is provided for the first time. The results showed that the circumferential and axial film thicknesses of the dentate-fin tubes increased with increasing fin density. The liquid film distribution of dentate-fin tubes with a low fin density was relatively uniform, and condensate drainage was easy. The special heat-transfer structure of dentate-fin tubes was examined, and it was found that the complex heat-transfer structure led to variations in the surface tension, which changes the liquid-film distribution. The local condensing heat-transfer coefficient of the dentate-fin tubes was very sensitive to the liquid-film distribution. The optimal fin density corresponding to the maximum overall heat-transfer coefficient was obtained, which showed that the mechanism of heat-transfer enhancement for dentate-fin tubes was a joint effect of the heat-transfer area and liquid-film thickness.

Thermal Effects on the Bearing and Ductility of Tubular Reduced Beam Section Connection: Numerical Investigation

In the present paper, an innovative fire-earthquake resistant joint called high-performance tube (HP-T) connection is presented and numerically validated. This HP-T connection improves the axial and rotational ductility as well as prevents brittle failure. Two series of models were simulated in ABAQUS software. In the first set of models, which was designed for heat simulation, a sequentially coupled thermal-stress analysis was performed to investigate the effects of different parameters such as web and flange tube thickness and the ratio of the applied load. To simulate the fire damage, two probable scenarios were considered: bottom flange tube damage and beam web damage when exposed to combined initial loading and fire. In the second set of models for seismic simulation, the failure mode, hysteretic curves, and strain distribution were analyzed. According to the results, HP-T robust connection not only provides appropriate ductility enhancement in force-variable fire conditions but also withstands at least 8% inter-story drift without considerable strength reduction.

Elastic behavior of composites reinforced by 3D printed tubular lattice braid textures

PurposeThe purpose of this paper is to introduce an innovative transversal tubular braid texture and to study the elastic behavior of its 3 D printed structure comparatively to 3 D printed longitudinal tubular braid texture (maypole) to be used as reinforcement.Design/methodology/approachRegarding the lack of proper machines for the production of the proposed texture, the structure of samples was produced as a tubular lattice braid texture using a 3 D printer with the fused deposition modeling method subsequent to simulation by Rhinoceros software. The produced specimens were composited by polyurethane resin. The composite samples were evaluated by the split disk mechanical test to obtain their hoop stress. The structures of the reinforced composites were theoretically analyzed by ANSYS software.FindingsThe results of the mechanical test and theoretical analysis showed that the composites reinforced with transversal tubular lattice braid have higher strength compared to the composites reinforced with longitudinal ones. This assured that the composite reinforced by transversal tubular lattice braid is reliable to be used as high-performance tube for different applications.Originality/valueFurther work is carried out to produce the innovated complex structure continuously by a specially designed machine and fibrous materials to reinforce tubular composites in an industrial continual process to be applied for high-pressure fluids flows.

High performance tube sensor based on PANI/Eu3+ nanofiber for low-volume NH3 detection

A novel polyaniline (PANI)/Eu3+ nanofiber sensing film was prepared in the presence of Eu(NO3)3 which serves as structure-directed agent. The morphological, component, crystallinity and electrochemical properties were carried out by using Scanning Electron Microscope (SEM), Energy-Dispersive X-ray (EDX), Fourier Transform Infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Brunauer-Emmett-Teller (BET) techniques. The results indicated the nanofiber-like network with porous structure appeared in the PANI embedded by Eu3+ ions, thereby leading to large specific surface area. Furthermore, the PANI/Eu3+ nanofibers were grown onto the inner wall of capillary glass to form the tube sensor. By the sensing measurements, this tube sensor enabled the detection of low-volume (0.3 mL) NH3 for response 435% at concentration of 0.25 ppm with a short response time (5 s) and recovery time (5 s), and the performances of reproducibility and selectivity were also excellent. The above results demonstrated the potential application of PANI/Eu3+ tube sensor for low-volume NH3 gas.

Beryllium – A Challenge for Preparation and Mechanical Characterization

Abstract Beryllium has an extraordinary combination of material properties such as low density, high melting point, high specific heat capacity, high Young's modulus, high hardness and low atomic number. The conventional investigation of the mechanical properties of Be and Be alloys is only possible under difficult conditions due to the material's toxicity and the resulting restrictions on sample manufacturing. These limitations are avoided, at least partly, when using a depth-sensing hardness test, also called nanoindentation, where the resulting contamination with Be dusts is limited to a controllable extent. For this work, technically pure Be from X-ray exit windows of high-performance X-ray tubes was chosen and its mechanical properties were characterized by means of nanoindentation. This contribution will focus in detail on the preparation of the material as well as the following microstructural characterization by means of light microscopy and scanning electron microscopy. The mechanical results of local nanoindentation will be correlated with the microstructure and compared with known values found in the literature.

Effect of Various Parameters on Working Condition of Chiller

Abstract The present work aims to find out the effect of various parameters on evaporator, compressor and condenser in vapour compression cycle using “high performance tube manufacturer's software” for evaporator and condenser and using “compressor selection software of a reputed manufacturer” for compressor. The present work includes the effect of number of tubes, number of passes and fouling factor on saturated refrigerant temperature (SST), tube side velocity, pressure drop and temperature approach in evaporator and condenser. Effect of SST on power input to compressor, cooling capacity, condenser capacity and coefficient of performance (COP) and also effect of condensing temperature on power input to compressor, cooling capacity and condenser capacity is studied using software.

고성능 상용튜브를 사용한 태양열 가열 해양온도차발전용 열교환기 설계 최적화

고성능 상용튜브를 사용한 태양열 가열 해양온도차발전용 열교환기 설계 최적화

Numerical study on characteristics of heat transfer and friction factor in a circular tube with central slant rods

In the present work, a numerical study on the characteristics of heat transfer and friction factor of laminar water flow in a circular tube fitted with a new tube insert (central slant rod inserts) is presented. Results reveal that the new inserts can fully disturb the core flow in the tube and create multiple longitudinal vortex structures, which are confirmed to be excellent flow structures for heat transfer enhancement. In addition, we carried out stereoscopic particle image velocimetry (SPIV) measurements in exactly the same facility as that of the numerical study to validate the accuracy of our numerical study. The results show good agreement between the experiment and numerical simulation. Following this, the effects of three parameters of central slant rods, including the slant angle, pitch and length in the radial direction, are discussed numerically. The computational results indicate that a moderate slant angle ranging from 20° to 30° can obtain the largest Nusselt number; however, the effect of slant angle on the friction factor is quite limited. The Nusselt number and friction factor both increase with a decrease in rod pitch and an increase in rod length in the radial direction. The simulation results show that the Nusselt number and friction factor are enhanced by 1.81–5.05 times and 2.49–6.92 times, respectively, to that of a plain tube. The performance ratio R3 values are in the range of 1.74–4.60. Empirical formulas for Nu and f are obtained based on calculation results. All results indicate that the central slant rod is a promising high-performance tube insert for heat transfer enhancement in practical applications.

Development of High-Performance Pressure Tube Material for the Canadian SCWR Concept

The Canadian super-critical water-cooled reactor (SCWR) concept is moderated by using heavy water, while the coolant is light water at 25 MPa with an inlet temperature of 625 K and an outlet temperature of 900 K. The fuel assemblies reside in vertical pressure tubes that are the pressure boundary. The pressure tubes are insulated from the fuel assemblies and operate at temperatures near the moderator temperature, at 390 K. The zirconium alloy Excel has been selected as a candidate material for the pressure tube based on favorable properties such as high strength, resistance to radiation-induced diametral strain, and high terminal solid solubility. However, significant future effort will be required to obtain material properties and crack initiation mechanisms at super-critical water (SCW) conditions to verify that annealed Excel is a viable option as a pressure tube material in the Canadian SCWR.

Active optimization design theory and method for heat transfer unit and its application on shape design of cylinder in convective heat transfer

When heat transfer enhancing technology is applied to design heat transfer unit, the improvement of heat transfer will usually accompanied with a dramatically increase of flow resistance. The main objective of present paper is to propose an optimization design theory and develop a corresponding approach to design heat transfer unit, in which the heat transfer and flow resistance will be considered simultaneously. As an example, this paper shows how to obtain a high performance tube in convective heat transfer by optimizing the shape profile using the theory and approach. A 2-D model is used in a direct problem solver, which is solved by finite element software and provides the numerical results in the optimization. Power consumption of flow field Pf is used to measure the flow resistance while generalized thermal resistance Rh is used to measure the thermal resistance. Meanwhile, genetic algorithm (GA) and simplified conjugate-gradient method (SCGM) are applied in this study to optimize the objective function composed by these two aspects. Based on the results of numerical calculation, the optimal velocity field with 61.93% decrease in Pf and 17.13% increase in Rh is obtained. Subsequently, the performances at different inlet velocities Vi are investigated. It is found that the shape profile obtained at Vi=0.1m/s always has a better performance than the circular one, even if it is not the ideal shape. Finally, the further optimizations based on different Vi and objective functions are discussed. The results prove that the proposed optimization method is effective in designing the shape of tube.

Numerical study on heat transfer enhancement characteristics of tube inserted with centrally hollow narrow twisted tapes

In this study, a new tube insert, named centrally hollow narrow twisted tape, is developed and its effect on the heat transfer enhancement performance of a tube under laminar flow conditions is numerically simulated. The model defines two study variables—hollow width and clearance—and then incorporates the concept of a unilateral twisted tape; the effect of the number of unilateral twisted tapes on the tube heat transfer performance is then examined. The results show that the tube with cross hollow twisted tape inserts has the best overall heat transfer performance for different hollow widths of the tape. Compared with the conventional twisted tape, the optimum overall heat transfer performance of the new type of tape increases by 28.1%. Clearance, which is defined as the width between the tube and twisted tape, also affects the heat transfer performance. The smaller the clearance, the better is the overall heat transfer performance. For different Reynolds numbers, the number of unilateral twisted tapes that gives the optimum overall heat transfer performance is different. If the Reynolds number increases over 600, the tube can achieve the best overall heat transfer performance when the number of unilateral twisted tapes is 4. Empirical formulas for Nu and f are obtained based on calculation results. The results show that under laminar flow conditions, the cross hollow twisted tape is a very promising high-performance tube insert.

Condensation heat transfer on single horizontal smooth and finned tubes and tube bundles for R134a and propane

For the refrigerants 1,1,1,2-tetrafluoroethane (R134a) and propane (R290), the condensation heat transfer was investigated on coated and uncoated horizontal smooth, standard finned and high performance tubes by experiments and computational fluid dynamics (CFD)-simulations. Measurements were carried out at a saturation temperature of 37°C varying the heat flux between 4kWm−2 and 102 kWm−2. In comparison to the Nußelt theory, enhancement factors of 12.8 to 30.2 were experimentally found for single standard finned and single high performance tubes. For both refrigerants, the high performance tubes showed a larger bundle effect than the standard finned tubes, although the latter show a lower heat transfer performance. In general, experimental results for coated tubes show a slightly lower heat transfer performance and no improvements of the condensate drainage could be observed for the modification. CFD-simulations were used to predict the condensation heat transfer on single tubes for the first time. Our experimental data and CFD-simulations were compared with analytical models available in the literature.

Advanced ceramic matrix composites for high energy x-ray generation

High energy x-ray targets are the anodes used in high performance tubes, designed to work for long operating times and at high power. Such tubes are used in computed tomography (CT) scan machines. Usually the tubes used in CT scanners have to continuously work at high temperatures and for longer scan durations in order to get maximum information during a single scan. These anodes are composed of a refractory substrate which supports a refractory metallic coating. The present work is a review of the development of a ceramic metal composite based on aluminium nitride (AlN) and molybdenum for potential application as the substrate. This composite is surface engineered by coating with tungsten, the most popular material for high energy x-ray targets. To spray metallic coatings on the surface of ceramic matrix composites dc blown arc plasma is employed. The objective is to increase the performance and the life of an x-ray tube. Aluminium nitride-molybdenum ceramic matrix composites were produced by uniaxial hotpressing mixtures of AlN and Mo powders. These composites were characterized for their mechanical, thermal, electrical and micro-structural properties. An optimized composition was selected which contained 25 vol.% of metallic phase dispersed in the AlN matrix. These composites were produced in the actual size of an anode and coated with tungsten through dc blown arc plasma spraying. The results have shown that sintering of large size anodes is possible through uniaxial pressing, using a modified sintering cycle.

Effect of Cross Section Reduction on the Mechanical Properties of Aluminium Tubes Drawn With Variable Wall Thickness

Variable thickness tube drawing is a new process for the production of high performance tubes. In this study, experiments were conducted to evaluate the effect of cross section reduction on the microstructure and mechanical properties of variable thickness aluminium tubes drawn using two different position controlled mandrel techniques. Various tubes with three different outer diameters were subjected to cold drawing at room temperature from 11% to 41% cross section reduction. The local mechanical properties were determined from tensile tests carried out on specimens cut from different positions in the tubes parallel to their axes. The distributions of the Vickers hardness over the surfaces at 0 deg and 90 deg to the drawing direction were examined. It was found that the microhardness, yield strength, and ultimate tensile of the deformed samples increase and the corresponding elongation decreases with the increase of cross section reduction. Also, the anisotropy in microstructure and mechanical properties is more significant with increasing of cross section reduction. The evolution of mechanical properties of drawn tubes versus cross section reduction depends on the mandrel shapes and initial tube outer diameter. This study helps to further understand the microstructure and mechanical properties evolutions during tube drawing process with variable thickness.

冷間ロール成形FEM技術の開発と新FFXミルの実用化

冷間ロール成形FEM技術の開発と新FFXミルの実用化

Innovative push-fit high-performance tube connector

Parker Instrumentation has unveiled a radical new tube connector it claims will deliver huge cost savings to builders of industrial equipment involving fluids.

Spiral CT angiography of aortic dissection

Spiral CT angiography (CTA) is one of the newest imaging techniques used for the evaluation of aortic dissection. Current spiral CT scanners with high-performance tubes and subsecond scanning allow increased regions of coverage. Large volumes of data are rapidly acquired through the aorta during maximum contrast enhancement. Multiplanar reformat (MPR), curved planar reformat (CPR), and 3-D rendering techniques including shaded surface display (SSD) and maximum intensity projection (MIP) are then applied to the data to generate CT angiographic images of the aorta. Emergent spiral CTA may be performed in patients with suspected aortic dissection who are hemodynamically stable. Postprocessing is performed immediately following data acquisition and can provide additional information for aortic dissection diagnosis and clinical management. The technique, applications, and limitations of spiral CTA for the evaluation of aortic dissection will be discussed relative to the role of other imaging modalities.

4951742 Refractory heat exchange tube : John Keyes assigned to High Performance Tube Inc

4951742 Refractory heat exchange tube : John Keyes assigned to High Performance Tube Inc

New possibilities for an all-electrostatic camera tube with a single-and-positive lens system

In order to develop extremely compact camera tubes which feature low power consumption comparable to solid-state imagers, we have developed an all-electrostatic camera tube based on electron optics characterized by a single-and-positive lens system composed of disk and cylinder electrodes. The new system was found to be very useful in producing compact high-performance camera tubes, due to its simple configuration and lack of negative lens component.

High-performance elastic tube splice

High-performance elastic tube splice