Helical Wire Research Articles

Characterization of the oil water two phase flow in a novel microchannel contactor equipped with helical wire static mixer

This study investigates an oil/water two-phase system to assess the potential efficacy of a novel passive mixer in enhancing the liquid-liquid interfacial area within a micro-channel contactor. In this system, two fluids are introduced into a microchannel with a diameter of 800 μm and a length of 20 cm, which is equipped with a stainless-steel helical wire measuring 250 μm in diameter. Throughout the experiments, both fluids are supplied at equal flow rates, and the dominant forces, including attachment and detachment forces, are examined. The results reveal a critical Weber number of 3.8 × 10−³, at which the first detachment occurs. A comparison between microchannels with and without the passive micromixer demonstrates that greater slug breakup occurs in the system incorporating the helical wire micromixer. This innovative configuration results in a significant reduction in slug/droplet size compared to a microchannel without a barrier, decreasing from approximately 600 μm to 390 μm at a flow rate of 0.8 mL/min. Additionally, a flow map is presented, illustrating three distinct flow regimes: flow contains long slug, Slug-droplet flow, and droplet flow regimes, with the droplet flow regime covering the largest area. The findings indicate that the implementation of this innovative passive mixer substantially increases the interfacial area, providing significant advantages for mass transfer applications.

Fabrication and Application of ZIF-8 Derived In2O3-ZnO Nanocomposites for Ultra-Sensitive NO2 Sensing under UV Irradiation at Room Temperature

Nitrogen oxide (NO2) is common by-products of industrial production, posing significant health risks to workers. Therefore, real-time monitoring of NO2 is crucial. In this study, innovative In2O3-ZnO nano-materials were prepared by combining In2O3 with ZIF-8 via electrospinning, for detecting trace amounts of NO2 at room temperature (RT). Compared to pure In2O3, the In2O3-ZnO nano-materials (V2) with a 10% weight ratio of ZIF-8 exhibited a significantly higher response (389.99) and a faster response time (16.9s) to NO2 under ultraviolet (UV) irradiation at RT. The superior gas sensing performance of the V2 nano-materials is attributed to the formation of n-n heterojunctions, enhanced optical absorption, increased oxygen vacancy ratio, and excellent dispersion among the nano-materials. The results demonstrate that V2 nano-materials can detect NO2 at parts-per-billion (ppb) levels at RT, making them suitable for monitoring trace amounts of NO2 in open environments. Furthermore, a portable real-time NO2 monitoring device was constructed using V2 as the sensing material, an LM358-based amplifier circuit for data acquisition, an STM32F103C8T6 microcontroller as the main control unit, and a buzzer as an alarm device. Compared to devices using a helical Ni-Cr wire as an indirect heat source, this integrated NO2 detection device offers real-time alarms with lower energy consumption. This application not only enhances worker health and safety in industrial environments but also demonstrates higher energy efficiency in practical application.

ID: 344721 Removal Procedure of a Helical Wire Structure Electrode from Benchtop and Chronic Porcine Models

ID: 344721 Removal Procedure of a Helical Wire Structure Electrode from Benchtop and Chronic Porcine Models

A Helicene‐Based Single‐Molecule Inductor and Capacitor with Frequency‐Dependent Charge‐Transport Pathways

Despite extensive studies has been explored on single‐molecule switches and rectifiers, the design of single‐molecule inductors has not been explored due to the experimental challenges in the investigation of frequency‐dependent charge transport at the single‐molecule scale. In this study, we synthesized a helicene‐based helical molecular wire and carried out meticulous single‐molecule conductance measurements, combined with current‐voltage (IV) studies with varying frequencies using the scanning tunneling microscope break junction (STM‐BJ) technique. Our results reveal the formation of a single‐molecule junction and highlight the unique behavior of the molecular wire in response to different alternating current (AC) varying frequencies. The transport of charges occurs selectively either through the coiled backbone of the conjugated helical structure or vertically via π‐π stacking, depending on the frequency of the applied AC. Notably, our investigation demonstrates the functionality of the wire as an inductor at low frequencies, and a capacitor at high frequencies. This work lays the foundation for a systematic approach to designing, fabricating, and implementing single‐molecule logic devices such as inductors and wave filters.

A Helicene-Based Single-Molecule Inductor and Capacitor with Frequency-Dependent Charge-Transport Pathways.

Despite extensive studies has been explored on single-molecule switches and rectifiers, the design of single-molecule inductors has not been explored due to the experimental challenges in the investigation of frequency-dependent charge transport at the single-molecule scale. In this study, we synthesized a helicene-based helical molecular wire and carried out meticulous single-molecule conductance measurements, combined with current-voltage (IV) studies with varying frequencies using the scanning tunneling microscope break junction (STM-BJ) technique. Our results reveal the formation of a single-molecule junction and highlight the unique behavior of the molecular wire in response to different alternating current (AC) varying frequencies. The transport of charges occurs selectively either through the coiled backbone of the conjugated helical structure or vertically via π-π stacking, depending on the frequency of the applied AC. Notably, our investigation demonstrates the functionality of the wire as an inductor at low frequencies, and a capacitor at high frequencies. This work lays the foundation for a systematic approach to designing, fabricating, and implementing single-molecule logic devices such as inductors and wave filters.

A generalized Bouc–Wen model for simulating the quasi-static and dynamic shear responses of helical wire rope isolators

This research investigates the mechanical behavior of a helical wire rope isolator deforming along its shear direction. In particular, we present the results of an extensive experimental campaign including both quasi-static and dynamic tests. The former provide hysteresis loops characterizing the device quasi-static behavior; the latter, performed by using an electro-mechanical shaker, furnish frequency response curves describing the dynamic behavior of a rigid block supported by the tested device. To simulate such a complex behavior, we adopt a generalized Bouc–Wen model and identify its parameters on the basis of the quasi-static test results. Subsequently, such a model is employed to reproduce the frequency response curves of the isolated rigid block. Since the results of the dynamic tests suggest the presence of rate-dependent hysteresis phenomena in the isolated system, the generalized Bouc–Wen model is enhanced by introducing a linear viscous component. Finally, to substantiate the model validation, the experimental results obtained by applying a series of white noise signals are compared with those obtained numerically to demonstrate the model capability of reproducing the device behavior in non-stationary response conditions.

Mixing behavior and mass transfer of liquid–liquid two-phase flow in an annular microchannel with helical wires

Combining the advantages of high efficiency, low-pressure drop, and large throughput, the pore array-enhanced tube-in-tube microchannel (PA-TMC) is a promising microreactor for industrial applications. However, most of the mass transfer takes place in the upstream pore region, while the contribution of the downstream annulus is limited. In this work, helical wires were introduced into the annulus by adhering to the outer surface of the inner tube. Mixing behavior and mass transfer of liquid–liquid two-phase flow in PA-TMC with different helical wires have been systematically studied by a combination of experiments and volume of fluid (VOF) method. The introduction of helical wires improves the overall volumetric mass transfer coefficient KLa by up to 133% and the mass transfer efficiency E by up to 117%. The simulation results show that the helical wire brings extra phase mixing regions and increases the specific interface area, while accelerating the fluid flow and expanding the area of enhanced turbulent dissipation rate. Influences of helical wires in various configurations are compared by the comprehensive index I concerning the pressure drop and mass transfer performance simultaneously and a new correlation between KLa and specific energy consumption φ is proposed. This research deepens the understanding of the mixing behavior and mass transfer in the PA-TMCs and provides practical experience for the process intensification of microchannel reactors.

A lightweight concrete composite material with improved EMI shielding by using a chiral particle array

This paper proposes a structure for concrete composite materials for electromagnetic interference shielding applications. It comprises an array of helical-shaped conductive particles as chiral additives. Unlike the previous studies using large quantities of conductive additives, this study provides a lightweight concrete composite due to the utilization of a small number of additives with a high level of shielding effectiveness in a wide frequency range. The heart of the proposed structure lies in leveraging the evanescent wave propagation in a circular waveguide, resulting in considerable shielding effectiveness. Under particular conditions, the helical particles can imitate a below-cutoff cylindrical waveguide and its dominant mode surface current on the helical wire. This phenomenon significantly attenuates the transmitted power from the array of helical particles in its resonance frequency range. Besides presenting the composition that exploits the magnetoelectric properties of the particles, this paper compares it with a traditional concrete composite, including randomly distributed sinusoidal steel rods. This second approach is examined using both experimental measurement and full-wave simulation methods. The results of this study indicate that the appropriate geometry of the conductive additives, in this case, chiral particles, and their arrangement in a regular array rather than a random distribution can enhance the efficiency of the conductive additives. This idea paves the way for more robust, efficient, and lightweight concrete composite materials, thanks to the recent advances in modern civil engineering manufacturing methods.

Multi-layer, torsional, highly-integrated yarn with outstanding orientation selective sensing ability for vertical-stress detected intelligent fabric

The multi-scale structure of yarns and fabrics is expected to provide unlimited possibilities for the integration of different performances and functions, which is expected to open up new opportunities for more complex and variable intelligent scenarios in the future. However, how to customize multi-functions through effective regulation and stabilization of several different units and composites in a highly integrated way still remains a great challenge. Herein, a torsional highly-integrated yarn with outstanding orientation selective sensing ability and robustness was achieved through a large-scale multi-unit friction spinning technology. Owing to the cooperative torsion structure of core layer (highly-stretchable spandex), middle layer (tight helical conductive metal wire) and the shell layer (polyester microfiber network massively composite with carbon nanotubes), the integrated yarn possesses outstanding orientation selective sensing ability. Different from directly coating strategies, the multilayer yarns with tight helical metal wire could be reversibly stretched up to 300 % with an almost consistent resistance (only varies 2.11 %), while which is highly sensitive to the vertical stress (5 kPa with 98.4 %) owing to the series–parallel behaviors between different layers. The sensitivity of the developed yarn in wind and sand monitoring and friction collision sensing endows it with a broad application prospect for protecting and early warning of human body and precision equipment. This work may provide a valuable integrated-solution for future intelligent fabric design for complex scenes.

Effect of spring-wire turbulators with different shapes on heat transfer improvement of solar air heaters; A numerical simulation

This study evaluates the heat transfer and performance characteristics of a solar air heater (SAH) equipped with spring-wire turbulators using a 3D verified CFD simulation process. Five different shapes of spring-wire (as shown in the graphical abstract) are investigated and compared to a flat SAH (without turbulator). The effects of helical diameter, pitch, and wire diameter on the performance of the system are comprehensively analyzed for all five mentioned geometries. The results reveal that the turbulator significantly enhances the thermal efficiency of the SAH within the absorber section. Rectangular cross section shape shows higher enhanced Nu number compared to the other cross section shapes. However, considering both heat transfer and pressure drop, the circular turbulator exhibits the optimal performance. Larger helical diameter, helical pitch and wire diameter, augments, decreases and increases the value of Nu/Nus respectively. Generally, higher increased Nu number also shows higher pumping power as well and that is why thermohydraulic performance parameter (THPP) is considered as well. Larger helical diameter, and helical pitch decreases and increases thermohydraulic performance respectively. For instance, the circular turbulator's THPP rises by approximately 17.5% as the pitch increases from 50 mm to 250 mm. However, the impact of wire diameter on THPP does not show a unified curve trend and depends on the shape of the turbulator. This study is remarkably useful for optimizing the performance of SAHs with turbulators, paving the way for enhanced device efficiency.

Pre-stress evaluation for steel strand based on energy leakage ratio of ultrasonic guided wave

Accurate prediction of the effective pre-stress in steel strands is of great importance for service performance assessment in pre-stressed structures. In this study, a new parameter for characterizing the pre-stress in steel strand is proposed, named energy leakage ratio (αEL) of ultrasonic guided wave (UGW). Firstly, the propagation of UGW between wires of the strand was theoretically analyzed. Then, finite element (FE) models of steel strand were established and laboratory experiments were conducted to verify the effectiveness and accuracy of the proposed αEL-based pre-stress evaluation approach. Results show that αEL increases linearly with inter-wire contact width. αEL can be taken as a new parameter for strand pre-stress identification, it shows a high linear correlation with pre-stress level, no matter whether the excitation position is located in core or helical wire. In terms of numerical and experimental results, the αEL-based pre-stress evaluation errors are within 3% and 4% respectively. Compared with the acoustoelastic effect based and nonlinear ultrasonic based approaches, the αEL-based approach showed the advantage in pre-stress identification accuracy.

Micro-crack localization for steel strands using nonlinear vibro-acoustic modulation based on modified signal bispectrum analysis

Under continuous environmental erosion and long-time high tension, fatigue micro-cracks of bridge cables appear frequently to challenge the reliability of cables. The vibro-acoustic modulation analysis is adopted because of its sensitivity to contact-type defects, especially fatigue cracks. In this paper, using multiple sets of low-frequency vibration and high-frequency ultrasonic excitation, the propagation of the ultrasonic wave in the steel strands is studied. Then, the modulated signal bispectrum is proposed to improve the detection reliability of nonlinear modulation components in the nonlinear vibro-acoustic modulation signal of the contact-type defect. The numerical simulations and laboratory tests of straight wire, helical wire, and multi-wire strands are carried out for micro-crack detection to verify the robustness of the proposed method. Compared with the traditional method, the modulated signal bispectrum can still produce clearer peak detection under high noise conditions. The results show that it provides a promising, dynamic and rapid cable defect detection technique.

Enhancing the efficiency of a double tube heat exchanger via a novel vibrating woven wire turbulator combined with a helical coiled wire; an experimental study

Vibrating turbulators have emerged as innovative methods for enhancing heat transfer in heat exchangers over the past two years. Previous studies have mainly employed string or strip configurations for turbulator construction. In this research, a novel vibrating turbulator, known as the vibrating woven wire turbulator, is introduced to enhance the thermal efficiency of heat exchangers. This study proposes the first-ever application of a turbulator with this unique geometry. This turbulator consists of intertwined metallic wires, providing a lightweight design with a substantial contact surface area for the fluid. Experiments are conducted for Reynolds numbers ranging from 1000 to 8500, covering both laminar and turbulent flow regimes. The findings demonstrate that this turbulator significantly enhances heat transfer by up to 236 %, while only resulting in a marginal increase in pressure drop. This remarkable improvement in heat transfer, while keeping the pressure drop within acceptable limits, gives rise to an impressive thermal enhancement factor (TEF) of 2.45. To achieve an even higher TEF, this study investigates the synergistic combination of the vibrating woven wire turbulator with a helical coiled wire turbulator. Experiments are conducted on coils with diameters ranging from 0.5 to 1.5 mm. The simultaneous utilization of both turbulators leads to a significant improvement in heat transfer coefficient and pressure drop, with an increase of 545 % and 320 %, respectively, resulting in a high TEF of up to 3.13.

Numerical study on entropy minimization in pipes with helical airfoil and CuO nanoparticle integration

Abstract In this study, minimizing entropy generation in a horizontal pipe is numerically investigated through two passive techniques: in the first mode, the helical wire inserts in the pipe were placed at three various ratios of pitch ratio. The second mode is adding cupric oxide nanoparticles at various volume concentrations. Experiments were conducted for Reynolds numbers ranging from 4,000 to 14,000 under a uniform heat flux scenario of 25,000 W/m2. The study utilized the ANSYS 14.5 software, employing the K-omega standard model, which involves three primary governing equations: continuity, momentum, and energy. According to the data, it was determined that the helical wire placed inside the pipe with a small pitch ratio decreased the entropy generation number. Cupric oxide nanoparticles also have a substantial impact on the entropy generation number. The higher volume concentration models had lower entropy generation numbers and Bejan numbers than the other models. Comparative analyses further emphasize the substantial advantages of using cupric oxide nanofluids and helical-wire inserts, with efficiency gains ranging from 5.08 to 11.7%.

Experiment on Heat Exchanger Using Innovative Coils and Phase Change Material/MXene Nanofluids

The utilization of innovative coiled wire turbulators along with phase change material (PCM; improving heat capacity) or MXene (having good dispersion stability) dispersed nanofluid in tubular heat exchangers may boost performance; however, it has not been explored yet. In the current analysis, experimental research is done on various mono-nanofluids and hybrid nanofluids flowing in a double-pipe heat exchanger with tapered, coiled wire turbulators to examine the hydrothermal aspects. Four coiled wire turbulators (conventional helical, conversing tapered, diverging tapered, and converging–diverging tapered) and four nanofluids (Al2O3/water, PCM/water, Al2O3+PCM/water and MXene/water) are utilized in the heat exchanger with all possible combinations. The effects of fluid types, turbulator types, total nanoparticle volumetric fraction, and nanofluid volume flow rate are investigated. Two thermal parameters (heat transport coefficient and Nusselt number), two hydraulic parameters (drop of pressure and friction coefficient), and two hydrothermal parameters (ratio of heat transport coefficient and drop of pressure, and generation of entropy) are considered objective functions. The study reveals that the diverging tapered, coiled wire yields significantly higher performance as compared to the conventional helical coiled wire as an insert. MXene/water has higher thermal performance; however, PCM-dispersed hybrid nanofluid yields better hydrothermal performance than other studied fluids.

Performance evaluation of a parabolic trough collector with a uniform helical wire coil flow insert

Solar energy is an extremely useful and dependable renewable energy source for meeting our society's diverse energy demands. Solar concentrator-based energy systems are currently the most efficient methods of using solar energy. Among these technologies, the parabolic trough collector is a mature and effective concentrating solar power technology with a wide range of real-world applications using solar alone or in combination with other energy sources. Flow insert is a potential approach for improving parabolic trough solar collector performance through enhanced heat transfer and heat absorption. The purpose of this study is to determine the feasibility of using a uniform helical wire coil flow insert in the LS-2 parabolic trough solar collector module. A computational fluid dynamic model developed in Ansys 18.1 is used in the current investigation. A uniform helical wire coil flow insert is modeled and compared with the plain tube without any insert inside it. Flow analysis, overall efficiency, exergy efficiency, and thermal efficiency are compared in the evaluation process. The overall efficiency and exergy efficiency of the parabolic trough collector are the most critical criteria in determining its performance. The parabolic trough collector is examined using a range of inlet fluid temperatures ranging from 303 K to 603 K and a volumetric flow rate of 50 L per minute to 250 L per minute. The pumping work is found to be the lowest, indicating that the increase in pressure drop has a negligible effect on the overall system performance. For the flow rate of 50 L per minute and inlet heat transfer fluid temperature of 303 K, the overall, exergy and thermal efficiency using a uniform helical wire coil flow insert are found to be 2.07 %, 2.1 %, and 2.2 %, respectively.

Analytical Estimation and Experimental Validation of the Bending Stiffness of the Transmission Line Conductors

The bending stiffness of transmission line conductors can vary significantly, ranging from maximum stiffness when behaving monolithically to minimum stiffness when wires behave loosely. This large range makes it challenging to estimate stiffness accurately at intermittent bending stages. To address this issue, a mathematical model that accounts for both frictional forces between wires in the same layer and the clenching effects of helical wires from preceding layers is proposed in this paper. The proposed model estimates cable bending stiffness as a function of axial load and curvature for multilayered strands by considering slip caused by wire behavior. To evaluate the bending stiffness, experiments were conducted on Panther and Moose Indian Power Transmission line conductors. The proposed slip model considers Coulomb frictional effects and clenching effects caused by Hertzian contact forces, filling the void in the estimation procedure. Additionally, the model considers the wire stretch effect, a parameter not previously accounted for in cable research. The predicted numerical results of the proposed model were found to vary within a maximum of 7% from the experimental tests. The proposed mathematical model thus offers a more accurate and comprehensive way of estimating the bending stiffness of transmission line conductors, addressing the existing limitations in the estimation procedure.

Response Characteristics and Suppression of Vortex-Induced Vibration of the Flexible Cable

To investigate the vortex-induced vibration (VIV) of a flexible cable in the uniform flow, experiments were conducted using a flexible cable with an external diameter of 80[Formula: see text]mm and a length of 10.48[Formula: see text]m in the wind tunnel. The characteristics of multi-modal VIV, time-frequency and traveling wave behavior of the flexible cable were analyzed. Moreover, the effects of twist direction, diameter and the single/double helical wire on the VIV characteristics of the flexible cable were investigated. It is found that the flexible cable experiences single and multi-modal VIVs in uniform flow at different incoming wind speeds, respectively. For the multi-modal VIV of the flexible cable, the vibration over the time history is dominated by two adjacent modal frequencies and shows a phenomenon of beat vibration. The multi-modal VIV responses of the flexible cable show a mix of standing and traveling wave behaviors, in which the effects of standing wave are more pronounced near both ends and the effects of traveling wave are more dominant in the middle region of the flexible cable. The twist direction of the helical wire has little effect on the VIV responses of the flexible cable. The VIV amplitudes of the flexible cable can be reduced by a single helical wire. With the diameter of the helical wire increases, the suppression effects of the single or double helical wire on the VIV of the flexible cable can be improved. Particularly, the double helical wire with diameter 0.10D can effectively suppress the VIV of the flexible cable.

Influence of idler misalignment fault on contact and dynamic characteristics of helical gear

Due to the advantages of stable helical gear transmission, it is widely used in industry, agriculture, and national defense. Shaft misalignment has a great influence on the vibration, bearing capacity, and life of gear transmission. Based on the idler wheel drive system as the research object, according to the principle of gear meshing, the helical gear time-varying contact wire length model was deduced. The dynamic model of the gear transmission system with faults is established considering the faults of the idler's center distance error and angle error, and the influence law of idler misalignment fault on the vibration of the idler transmission system is revealed. On this basis, the finite element model under angle error is established to analyze the contact stress of the tooth surface under different faults and reveal the contact stress distribution law of the tooth surface. The results show that the misalignment fault will change the length of the helical gear contact line. When the gear shaft misaligns, it will increase the axial force of the gear and increase the axial vibration of the gear. Moreover, the angle error will cause uneven load distribution on the tooth surface of the helical gear, which will reduce the contact area of the gear and increase the contact stress. The phenomenon of off-load of gear accelerates the wear of the gear tooth surface and shortens the life of the gear. The study of idler misalignment fault is of great significance for prolonging the life of gear and providing the basis for gear fault diagnosis.

Improving the thermal performance of the heat exchanger through simultaneous utilization of novel magnetic turbulators and helical coil wire turbulators

In this study, the effect of simultaneously using two active and passive methods, namely the magnetic turbulator and the helical coil wire (HCW) turbulator, on the hydrothermal parameters of a double tube heat exchanger is being evaluated for the first time. The results are also being compared with those of a simple heat exchanger, a heat exchanger equipped with a magnetic turbulator, and a heat exchanger with a HCW turbulator insert. Finally, the most optimal option is selected using TEF. Tests have been conducted using different pitch ratios of the HCW turbulator (ranging from 2.5 to 10) and fluid flow rates (ranging from 0.5 to 4 l/min). According to the results, the usage of the HCW turbulator, magnetic turbulator, and the simultaneous use of both turbulators increases heat transfer by 237 %, 262 %, and 491 %, respectively. Additionally, the pressure drop in the presence of these two methods is 3.8 times that of a simple heat exchanger. Furthermore, with the help of TEF, the heat exchanger armed with both turbulators is chosen as the optimal option, achieving a TEF of 3.78.