Horizontal Coil Research Articles

A size-distinguishing miniature electromagnetic tomography sensor for small object detection

Electromagnetic tomography (EMT) is an emerging imaging technique that presents the property distribution of conductive or magnetic materials based on signals from the coil array on the EMT sensor. However, conventional EMT researches generally involve large-size EMT sensors, which are ineffective in detecting and discerning the size of small objects due to limited spatial resolution, sensitivity and relatively high noise level. As such, this paper presents a novel miniature EMT sensor, which incorporates 8 small coils around the circumference for imaging and 2 larger horizontal coils that generate a vertical field for target size distinction. Moreover, a novel equivalent theory is proposed to approximate the effect of the horizontal coils by the cumulative effect of the 8 small coils. An EMT testing system is established with the proposed sensor array and the multi-channel instrument developed in our lab. Experiments based on multiple sample distributions and different reconstruction algorithms validate the ability of the sensor to detect and distinguish the size of small objects of different materials. Furthermore, the equivalent theory was validated through the experiments.

Potential of ground-penetrating radar to calibrate electromagnetic induction for shallow soil water content estimation

Ground-penetrating radar (GPR) and electromagnetic induction (EMI) are used to determine and map soil water content (SWC) in the agricultural landscape. While GPR provides a straightforward estimation of SWC, EMI requires site-specific calibrations mainly based on point-scale measurements such as time domain reflectometry (TDR). However, there is a significant difference in the measurement volumes between EMI and point-scale TDR measurements. This study aimed to enhance the calibration of EMI for estimating SWC in the agricultural landscape by leveraging the larger sampling volumes provided by GPR. Apparent electrical conductivity (ECa) from a multi-coil EMI sensor and dielectric constant from GPR with two center frequencies (500 MHz and 250 MHz) were collected as soil proxies along with TDR measurements. Calibration models were developed under irrigated conditions and the model evaluation was conducted under natural moisture conditions. Correlations were assessed between the proxies from GPR and EMI with TDR-derived SWCs. Simple linear regression (SLR) models were developed between EMI and GPR data to predict SWC. Strong positive correlations (r ≥ 0.80) were observed between the proxies (GPR and the shorter inter-coil spacing (0.32 m) of EMI) and TDR-measured SWC. ECa data from vertical and horizontal coil orientations of the shorter inter-coil spacings were selected to develop SLR models with GPR. The SLR models with the GPR 500 MHz frequency showed a higher coefficient of determination (R2 > 0.70) for both coil orientations of EMI. Results showed the potential of using GPR to calibrate EMI for shallow SWC estimation (below 0.5 m). Nevertheless, the EMI estimated SWCs were not effectively verified with GPR-estimated SWCs, which could be attributed to specific site conditions in the study area. Further research must focus on improving the calibration and model evaluation by incorporating the variability of other soil parameters (soil porosity, pore-water conductivity, and soil salinity) that may affect the SWC–ECa relationship.

A reconfigurable bipolar coil for wireless charging systems with interoperability and misalignment tolerance characteristics

Wireless Power Transfer (WPT) technology has been developing rapidly in recent years. Electric Vehicles (EVs), as an emerging mode of transport, also benefit from the WPT technology. Various EV manufacturers have different coupling structures, which can lead to incompatibility problems between the coils. Meanwhile, due to the human parking, misalignment between the transmitting and receiving coils may occur. To solve these problems, this paper proposes a reconfigurable bipolar coil structure with both interoperability and misalignment tolerance. A 200-W experimental prototype is built, which can achieve 84.33% and 84.76% system transmission efficiency with vertical and horizontal bipolar coils. The effectiveness of the proposed reconfigurable bipolar coil is finally verified by comparing the computational and experimental results.

Suggestion of a design method for horizontal spiral coil type ground heat exchangers

The need of geothermal energy is constantly increasing for economical and environmental benefits. Horizontal ground heat exchangers (GHEs) can reduce the installation cost and they can also compromise between increasing in efficiency and costs. There are many kinds of GHEs, and it is known that slinky and spiral coil type GHEs show high thermal performance in the horizontal system. However, there is no adequate guideline to design the spiral coil type GHEs even though there is a design program for the slinky type GHEs. Therefore, this paper presents a design module for the horizontal spiral coil type GHEs. Dried Joomunjin standard sand was filled in a steel box including a horizontal spiral coil type GHE of which the size was 5m x 1m x 1m and thermal response tests (TRTs) were conducted for 30 hours to evaluate heat exchange rates. Based on the experimental results, a modified design module, that includes a scheme to properly evaluate design parameters such as ground thermal resistance and borehole thermal resistance used in the Kavanaugh theory for designing a spiral coil type GHE, was suggested.

An isothermal constant surface area horizontal helical coil under natural convection and radiative heat loss: A CFD study

This paper presents a numerical analysis of a horizontally oriented constant surface area isothermal helical coil under natural convection heat transfer and surface radiation. Numerical computationsare carried out in the laminar regime of Rayleigh number (104 ≤ Ra ≤ 108), surface emissivity (0 ≤ ε ≤ 1), and geometrical parameters of the helical-coil, like diameter of the coil (8 ≤ D/d ≤ 24), pitch (3 ≤ p/d ≤ 7.5), and coil height (40 ≤ H/d ≤ 60) to study the heat transfer characteristics. This study is used for effectively designing the helical coils, which are typically manufactured at an extremely high temperature. The numerical computation has been validated by comparing the average Nusselt number (Nu) with the previous experimental results. Temperature-dependent fluid properties are incorporated to achieve precise results over a wide range of temperatures. The effect of the geometrical parameters on the heat transfer characteristics has been depicted graphically in terms of average Nu, relative convection and radiation heat transfer rate, and the temperature profile. It is found that the relative contribution of radiative heat transfer is 87.8% at an emissivity of 0.9 and Ra of 10(Ali, 19944), whereas, for an emissivity of 0.1 and Ra of 10(Moawed, 20058), the relative contribution of radiation heat transfer is only 6.4%. Lastly, a correlation has been developed for the average Nu based on all the pertinent parameters which can be beneficial to the engineers in the industry and also academic researchers. The developed correlation has been used to predict the cooling curve of the helical coil in certain situations.

A novel magnetic circuit and structure for magnetic levitation ruler

The single axis linear displacement measurement system of CMM is composed of grating ruler, servo motor and linear motion mechanism. Although the measuring accuracy of grating ruler is high, the accuracy of servo motor and linear motion mechanism is low. Therefore, the complex structure limits the measurement accuracy of the linear displacement measurement system. This paper introduces a novel linear displacement measurement system named magnetic levitation ruler. According to the working principle of grating ruler and the characteristics of magnetic levitation technology, the magnetic circuit design and structural design of magnetic levitation ruler are completed in this paper. The mover core of the magnetic levitation ruler is in the stable working magnetic field provided by the stator yoke. The horizontal control coil wound on the mover core can obtain more stable ampere force to improve the control accuracy of the mover core displacement. Therefore, the mover core can be moved in step mode, and the length of each step is fixed. Each step is the minimum scale of the magnetic levitation ruler. Therefore, the mover core can implement displacement measurement while moving in a linear motion. This paper analyzes the working principle of levitation, horizontal motion, and displacement measurement of magnetic levitation ruler, and determines the structural materials and parameters of magnetic levitation ruler with the help of finite element analysis software. The simulation results show that the levitation force of the magnetic levitation ruler is proportional to the current passing through the levitation coils, and the thrust of the horizontal control coil is less disturbed by the magnetic field. Compared with the linear displacement measurement system with rotational servo motor or permanent magnet synchronous linear motor as the core, the magnetic levitation ruler has stable magnetic field, strong controllability, high integration, and is easier to achieve high-precision control.

Integrated Digital Microfluidics NMR Spectroscopy: A Key Step toward Automated In Vivo Metabolomics.

Toxicity testing is currently undergoing a paradigm shift from examining apical end points such as death, to monitoring sub-lethal toxicity in vivo. In vivo nuclear magnetic resonance (NMR) spectroscopy is a key platform in this endeavor. A proof-of-principle study is presented which directly interfaces NMR with digital microfluidics (DMF). DMF is a "lab on a chip" method allowing for the movement, mixing, splitting, and dispensing of μL-sized droplets. The goal is for DMF to supply oxygenated water to keep the organisms alive while NMR detects metabolomic changes. Here, both vertical and horizontal NMR coil configurations are compared. While a horizontal configuration is ideal for DMF, NMR performance was found to be sub-par and instead, a vertical-optimized single-sided stripline showed most promise. In this configuration, three organisms were monitored in vivo using 1H-13C 2D NMR. Without support from DMF droplet exchange, the organisms quickly showed signs of anoxic stress; however, with droplet exchange, this was completely suppressed. The results demonstrate that DMF can be used to maintain living organisms and holds potential for automated exposures in future. However, due to numerous limitations of vertically orientated DMF, along with space limitations in standard bore NMR spectrometers, we recommend future development be performed using a horizontal (MRI style) magnet which would eliminate practically all the drawbacks identified here.

Effect of helical coil orientation on flow boiling process

The flow boiling process in helical coils is investigated experimentally to analyze the effects of the orientation of the helical coil on the local heat transfer distribution, pressure drop and critical heat flux. The literature review suggests that little information is available on the influence of the orientation on the heat transfer distribution, pressure drop and critical flux during flow boiling in helical coils. Experiments are performed on horizontal and vertical helical coils with R123 as the working medium. SS-304 tubes of 5.5 mm and 7.5 mm diameter with a coil diameter of 150 mm are chosen in this study. Non-intrusive thermal imaging technique is used to measure the wall temperature. The differential pressure transmitter is used to measure the pressure drop across the test section. The two-phase pressure drop is not affected significantly by the orientation of the helical coils. The wall temperature, heat transfer distribution and the critical heat flux are affected by the orientation of the helical coil. The local and average heat transfer coefficient is higher in vertical oriented helical coils than the horizontal oriented helical coils. The value of heat flux at the burnout is higher in vertical orientation compared to horizontal orientation in both the coils.

Optimization of Robust LMI-Control Systems for Unstable Vertical Plasma Position in D-Shaped Tokamak

The paper is devoted to the synthesis, comparison, and optimization of robust LMI-control systems for the vertical plasma position in a D-shaped tokamak, specifically the T-15MD tokamak (Kurchatov Institute, Moscow, Russia). The novelty of this work is to find out the possibilities of LMI robust control systems, according to the criteria of the robust stability radius and control power peak at the rejection of a minor disruption type disturbance and a reference step signal using a unique unstable first-order plasma model. The plant under control consists of the connected in series plasma model with additive disturbance containing plant uncertainties, horizontal field coil (HFC), and actuator model as a multiphase rectifier. A set of robust controllers was designed by Linear Matrix Inequalities (LMI) method with pole placement in the LMI regions, state H2/H∞ performance, and output signal performance. The LMI theorems of the paper are directed to design the robust controllers and study the systems with the aim of eliminating the gap between theory and practice. The main achievement of this work consists in the optimization of robust control systems of the unstable plant with uncertain disturbance on the set of LMI synthesis approaches. The control systems have original quality criteria, such as control power and robust stability radius. The best control system on the basis of two criteria, namely, Dα,r,ϑ control system provides stabilization of the vertical plasma position on the real-time digital control testbed.

Study on the recovery characteristics of disc-type superconducting fault current limiter coils from the perspective of boiling heat transfer and bubble behaviors

The disc-type superconducting fault current limiter (SFCL) encapsulated by yttrium barium copper oxide (YBCO) superconducting material has broad application prospects in the current limiting field. However, the difficulty to recover quickly and safely after quench remains the bottleneck of the disc-type SFCL. Existing work on the SFCL mainly focused on the resistance recovery while the bubble behavior and distribution, which are important factors affecting the temperature distribution of the superconducting tape, are rarely noticed. In this paper, a visualization platform for the superconducting tape impulse experiment is built, and the dynamic behavior and distribution characteristics of bubble clusters are analyzed by image processing technology. Two arrangements (vertical and horizontal) disc-type coils are comparatively studied. Firstly, the huge differences in the recovery performance of the superconducting tape at different positions are observed and compared. In the vertical coil, the fastest one can recover in 1.414 s and the slowest one takes 2.426 s to recover to the superconducting state. The maximum temperature difference of superconducting tapes at different positions in the coil is up to 10.8 K. In the horizontal coil, the recovery times of the two samples are 1.497 s and 1.595 s, respectively, indicating that the recovery is significant uniform. The whole process of bubble generation, merging and detachment in the transient boiling process is comprehensively and qualitatively analyzed with the help of the high-speed camera. Secondly, it is observed a phenomenon of bubble retention is common in the vertical coil while the horizontal coil is not, which is not conducive to the safe operation of the system. Therefore, the bubble recovery is as important as the resistance and the temperature as a recovery reference. In summary, the horizontal coil is superior to the vertical coil in terms of safe recovery and uniform cooling based on the experimental results in this paper, the coupling analysis of bubble dissipation behavior and thermodynamic characteristics of superconducting tape during quench and recovery is of theoretical significance to the future research work on accelerated recovery and the SFCL structural design.

Simulation of Concrete Pumped in Horizontal Coil and Super High-Rise Building Based on CFD

Simulation of Concrete Pumped in Horizontal Coil and Super High-Rise Building Based on CFD

An Empirical Analysis of Heat Expulsion and Pressure Drop Attribute in Helical Coil Tube Using Nanomaterials

Water nanofluids were examined in a horizontal helical coil tube with constant temperature limitations for Dean values between 1000 and 10,000 to determine the rate of thermal radiation transmission and pressure drop characteristics. When conducting the tests, a variety of Al2O3 water nanofluid requirements were used, including varying mass flows, heat exchange rates for various nanoparticle volume concentrations, and changes in coil‐side drop in pressure versus coil‐side Dean number. Since nanoparticles have enhanced heat capacity, nanoparticles are developing as a transitional beginning of heat transfer fluids with significant potential in thermal management applications. Many applications require nanofluids to be used as heat transfer fluids; thus, scientists are concentrating their efforts on these fluids. The Reynolds values on the coil and shell were in the 1000 to 7000 range on either side of the wire. This paper discusses the impact of particle volume density on shell‐side flow temperatures, heat expulsion rate, and thermal conduction. The result shows that the average heat transfer rises by 13% and 17% when nanoparticle volume fraction percentage density is 0.1%, 0.2%, and 0.3 percent. The results demonstrate that reducing the mass flow by an increase in particle volume density, pipe diameter, and coil radius improves heat exchanger performance. The efficiency of the model is enhanced by increasing the diameter of the tube while simultaneously decreasing the diameter of the coil.

Comparison Study of Power Supplies in Real-Time Robust Control Systems of Vertical Plasma Position in Tokamak

The article is devoted to a comparative study of VIs (Voltage Inverters) in the RAO (Relay Auto-Oscillatory) mode and in the multilevel PWM (Pulse Width Modulation) mode as actuators in closed-loop control systems of vertical plasma motion in the T-15MD tokamak. The new digital multilevel PWM controller was developed. Both systems were put under equivalent conditions in terms of the same response to external signals. The discrete robust controller is single for both control systems and has been designed by LMI (Linear Matrix Inequalities) approach using the LPV (Linear Parameter Varying) plant model. The main criteria for comparison are the control power and signal spectrum on the HFC (Horizontal Field Coil). The simulations were performed on the real-time test bed consisting of two real-time target machines connected in a feedback loop “Plant Model – Controller”, to basically bring the system as close to reality as possible. The comparison results have showed the significant superiority of the 9-level PWM VI over the VI in RAO mode according to the selected criteria.

New horizontal and vertical field coils with optimised location for robust decentralized plasma position control in the IGNITOR tokamak

The paper deals with the improvement of the poloidal system of the IGNITOR tokamak, and the design and simulation of the robust decentralised control systems of the plasma’s vertical and horizontal position. The results were obtained on a linear model that is constructed from the circuit equations for the coils, plasma, and vacuum vessel (VV) currents, and from the force balance equations for the plasma. Two new coils that are located close to the VV have been introduced in the IGNITOR poloidal system; specifically, a Horizontal Field Coil (HFC) that is designated for the plasma vertical position control and a Vertical Field Coil (VFC) that is used for the horizontal position control. For the first time in the design of D-shaped tokamaks poloidal systems, the location of the HFC was optimised to achieve the maximum size of the plasma controllability region in the vertical direction and the location of the VFC was determined from the optimisation of the plasma position response to the voltage step function. Although the ideal position of the VFC with fast response time is on the equatorial plane, its location usually is occupied by the other devices such as ports, diagnostic system, and heating systems, so the separated two-section VFC is used. Careful calculation shows the performance is degraded by only 20 % in this layout. For the improved IGNITOR poloidal system, the new robust decentralised plasma position control systems were designed by means of two robust approaches: H∞-optimisation and Linear Matrix Inequalities (LMI). The results of the simulation of the control systems with two types of actuator models as the multiphase thyristor rectifier and the voltage inverter in Pulse- Width Modulation (PWM) mode for the new IGNITOR poloidal system are presented.

Characterization of soil drainage using electromagnetic induction measurement of soil magnetic susceptibility

As a physical property of soil, magnetic susceptibility (MS) has been widely used to delineate soil drainage conditions over the past two decades, where all MS values were derived from laboratory measurements. In this paper, the ability of an electromagnetic induction (EMI) instrument, Geonics EM38, in in-field measurements of apparent magnetic susceptibility (MSa or κa) of topsoil was tested on six selected soil profiles having different drainage conditions. The MSa data, measured in both vertical and horizontal coil configurations of EM38, were then inverted using an iterative 1-D inversion procedure to calculate real volume MS of soil layers up to 1 m depth. Moreover, volume and mass-specific MS of the soil profiles were directly measured in laboratory by employing Bartington MS2C and MS2B sensors applied on core and dried soil samples, respectively, collected at the soil profiles. Comparing the results revealed that volume MS profiles derived from inversion of MSa data were positively correlated with MS profiles measured in laboratory, especially at topsoil. It was also found that MS values in poorly drained soil profile were lower than those of a well-drained profile. So, considering that EMI methods are fast, precise and cost-efficient, they would be preferred over conventional methods for delineating soil drainage conditions if using soil MS assessment is considered as soil drainage criteria.

METHOD AND RESULTS OF HYDRAULIC CALCULATION OF THE HEAT EXCHANGE SURFACE OF THE ONCE-THROUGH STEAM GENERATOR

Ukraine with her developed machine-building potential can take the deserving place in the production of small modular reactors. One of basic elements of small modular reactors equipment is steam generator. Among different types a deserving place is occupied by once-through steam generator. small modular reactors can exemplify to transport nuclear installation, for example KLT-40S. The calculation of hydraulic resistance is included in designing of steam generators, that it is necessary for the choice of pumps and optimization of structural parameters. In the presented article methodology of hydraulic calculation of once-through steam generator is examined with the coiling surface of heating. As a result of analysis of literature formulas were selected for the calculation of hydraulic resistance for four modes of flow: transverse flow of the coolant over horizontal coils, movement in bent tubes of a single-phase working fluid, boiling water and superheated steam. Results over of calculation of steam generators are brought by power 45 МВт with different structural parameters: diameter of coils, horizontal and vertical pitches of coils location in a bunch, speed of feedwater and coolant. The got results were verified by comparing to data of calculation on the code of ASPEN-TECH. It was found out as a result of research that increase of diameter of coils, as well as the increase of pitches of coils location in a bunch does not reduce hydraulic resistances, as expected, but increases them as a result of worsening of heat exchange and, accordingly, increase of heat-exchange surface. The increase of speed of coolant results in the height of resistance on the side of coolant and does not influence on resistance of working body. The increase of speed of feedwater increases resistance on the side of working fluid and does not influence on resistance of coolant.

EXPERIMENTAL INVESTIGATIONS ON HEAT TRANSFER ENHANCEMENT FOR HORIZONTAL HELICAL COIL HEAT EXCHANGER WITH DIFFERENT CURVATURE RATIOS USING CARBOXYMETHYL CELLULOSE-BASED NON-NEWTONIAN NANOFLUIDS

EXPERIMENTAL INVESTIGATIONS ON HEAT TRANSFER ENHANCEMENT FOR HORIZONTAL HELICAL COIL HEAT EXCHANGER WITH DIFFERENT CURVATURE RATIOS USING CARBOXYMETHYL CELLULOSE-BASED NON-NEWTONIAN NANOFLUIDS

Depth Sensitivity of Apparent Magnetic Susceptibility Measurements using Multi-coil and Multi-frequency Electromagnetic Induction

Apparent magnetic susceptibility (MSa) as recorded by electromagnetic induction (EMI) instruments could offer relevant information about non-soil subsurface features. It is less affected by natural soil properties than its prominent counterpart, i.e., apparent electrical conductivity (ECa). Hence, MSa is generally a promising approach to investigate artificial inclusions and structures in soil. However, while the origin depth of EMI based ECa is widely accepted, the depth sensitivity (DS) of MSa measurements remains poorly understood. The depth interpretation of MSa is particularly challenging due to negative values especially for objects that are randomly distributed over different depths. Here we assessed the performance of both multi-coil (MC) and multi-frequency (MF) EMI sensors for identifying and determining the DS of MSa measurements in shallow soils through detection of buried small targets of known conductivity. Two experiments were conducted in a sandy loam podzolic soil in western Newfoundland, Canada. Materials of different conductivities, including metal and plastic targets, were buried at depths between 20 and 80 cm. Three inter-coil separations (32, 71 and 118 cm) of the MC sensor and four factory-calibrated frequencies (18, 38, 49 and 80 kHz) of the MF sensor were tested in both horizontal and vertical coil orientations. The MC sensor clearly detected all four metal targets from three coil separations in both coil orientations while the MF sensor identified more anomalies than targets limiting its information value. Based on the measurements from MC and the theoretical DS function, a criterion was developed and validated to assess the potential depth origin of MSa. We found that negative or less than the background values occur, if the depth of the target is shallower than 0.36 times the coil distance of the employed EMI sensor. According to this criterion, the depth origins of metallic targets were correctly identified under the assumption of low induction numbers, even if values were negative.

Plasma Control in Tokamaks

The plasma magnetic control systems for ITER (International Thermonuclear Experimental Reactor) are presented. The systems comprise original engineering solutions for plasma position, current and shape control for the two versions of ITER: ITER-1 and ITER-2, including those designed in V. A. Trapeznikov Institute of Control Sciences of the RAS. It is noted that in ITER-1 the plasma position and shape were controlled by all PF-coils and robust H∞-controllers, while to decrease peaks of control power for suppressing minor disruptions the additional nonlinear circuit was used without significant changes in displacements of the gaps between the plasma separatrix and the first wall. In ITER-2 the special circuit with a fast voltage rectifier was used for plasma vertical speed stabilization about zero, while for plasma current and shape control the special cascade control systems were designed with and without the control channels decoupling, with robust H∞-controllers and predictive model, and with adaptive stabilization of the plasma vertical position as well. To increase the plasma controllability region in the vertical direction the additional horizontal field coils were introduced into the ITER-2 vacuum vessel and the capabilities of the system with the new circuits to control the plasma vertical position at the noise presence were investigated.

Experimental and numerical study on heat transfer intensification in turbulent flow of CuO–water nanofluids in horizontal coil

This work presents experimental and CFD simulation results of heat transfer for water and CuO-water nanofluid flow systems stabilized by capping agents. The experiments were carried out in a helically coiled tube in the range of turbulent flow regime with Reynolds numbers from 6000 to 21,968, for practical applications importance. Nusselt number enhancement with regard to host liquid was observed, up to 18–35 % for nanofluids under investigation. Numerical calculations were performed using the ANSYS® Fluent® package employing homogenous single-phase model with the assumption of constant wall temperature condition. The k-ε Realizable Turbulence and Enhancement Wall Treatment models were applied in all analyzed cases. New type stabilizer CTAC was employed which lead to enhanced heat transfer in coil in obtained nanofluids.