Coil Inside Research Articles

Radiofrequency Induction Heating for Green Chemicals Manufacture: A Systematic Model of Energy Losses and a Scale-Up Case-Study.

Radiofrequency (RF) induction heating has generated much interest for the abatement of carbon emissions from the chemicals sector as a direct electrification technology. Three challenges have held back its deployment at scale: reactors must be built from nonconductive materials which eliminates steel as a design choice; the viability of scale-up is uncertain; and to date the reported energy efficiency has been too low. This paper presents a model that for the first time makes a comprehensive analysis of energy losses that arise from RF induction heating. The maximum energy efficiency for radio frequency induction heating was previously reported to be 23% with a typical frequency range of 200-400 kHz. The results from the model show that an energy efficiency of 65-82% is achieved at a much lower frequency of 10 kHz and a reactor diameter of 0.2 m. Energy efficiency above 90% with reactor diameters above 1 m in diameter are predicted if higher voltage radio frequency sources can be developed. A new location of the work coil inside of the reactor wall is shown to be highly effective. Losses arising from heating a steel reactor wall in this configuration are shown to be insignificant, even when the wall is immediately adjacent to the work coil. This analysis demonstrates that RF induction heating can be a highly efficient and effective industrial technology for coupling high energy demand chemicals manufacture electricity from zero carbon renewables.

A Hybrid IPT System Implementing Misalignment Tolerance and Constant Current Output With Primary Intermediate Coil

Inductive power transfer (IPT) systems have advantages of safety, flexibility, and convenience compared to plug-in charging systems. However, in practical applications, pad misalignment is still an almost inevitable issue which may cause variation in magnetic couplings, thus affecting the power transmission and reducing the system efficiency. Therefore, IPT systems are usually expected to achieve tolerance for misalignment. To fulfill this feature, a hybrid IPT system is proposed in this article. By adopting two coils compensated by different topologies in receiver side and an additional intermediate coil in transmitter side, load-independent constant output current with improved misalignment tolerance can be achieved. In addition, when the receiver pad is very far away from the transmitter pad, the proposed system can operate safely due to the inherent limitation ability of the primary inverter current. The design process is presented to optimize the misalignment performance. Based on the experimental results of a 3.3-kW prototype, the fluctuation of the output current is less than 5% within ±300-mm misalignment in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -axis, −30- to +60-mm misalignment in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> -axis, and −80- to +60-mm misalignment in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -axis. The system efficiency is 96.7% at nominal operating point (NOP) and varies from 94.7% to 97.8% with variable loads and misalignment.

Performance Investigation of a Three Fluid Heat Exchanger Used in Domestic Heating Applications

Recent work analytically investigates the heat transfer characteristics of a three fluid heat exchanger used for domestic heating applications with respect to different design parameters, i.e. flow rate, inlet temperature, tube diameter, coil diameter, and coil pitch. The present and previous results are compared with the literature. Overall agreement among these results are observed with little variation. Afterwards, the present temperature data was verified with prior experimental data and little deviation observed in these results vary from -4.28 % to +6.68 % and -6.17% to +5.92% in parallel and counter flow configuration, respectively. It is ensued that the coil side Nusselt number increases with the rise in coil side fluid flow rate and inlet temperature, coil outside fluid inlet temperature and coil diameter respectively. The increment in coil side flow rate and inlet temperature are identified as the major contributors, with 297% and 39.5% contributions. Similarly, growth in coil outside Nusselt number is observed with the rise in coil side fluid inlet temperature and flow rate, coil outside fluid flow rate and inlet temperature, and coil pitch respectively. The coil pitch and flow rate at the coil outside are identified as major contributors with 36% and 28.5% contribution repsectively. Distinct correlations for heat transfer in the present HEx are proposed for coil inside and outside fluid flow in a turbulent flow regime. The developed correlations results are compared with the present result, and reasonable agreement is observed within the data range of +13% to -14% and +10% to -11% for coil inside and outside Nusselt number, respectively.

A tungsten external heater for BX90 diamond anvil cells with a range up to 1700 K.

Resistive heating of a sample in a diamond anvil cell (DAC) can generate a homogeneous temperature field across the sample chamber with reliable temperatures measured by a thermocouple. It is of importance in experiments aiming at exploring phase diagrams and quantifying thermoelastic properties of materials. Here, we present a ring-heater design developed for BX90 diamond anvil cells (DACs). It is made of a ring-shaped aluminum oxide holder hosting a tungsten wire coil inside and coupled with Ar + 2% H2 gas to prevent oxidation during experiment. This modular plug-and-play design enables in situ studies of samples via x-ray diffraction up to a temperature of 1700K. Temperature in the BX90 sample volume as measured through a thermocouple was calibrated using the melting point of gold. As an application of this design, we report the thermal expansion coefficient of MgO at 9.5(1) GPa.

Conceptual issues of the cold filter trap development for the sodium coolant purification in fast-neutron reactors

The paper presents the results of studying the peculiarities of heat and mass exchange in cold traps for the sodium purification of impurities in fast reactor circuits both in dedicated test areas simulating various trap components (isothermal sump, nonisothermal sump, filters, final cooling area) and in trap prototype models. As a result, a scientific rationale has been formed for developing traps of a unique design for various reactors. The impurity capacity of the traps is three to four times as high as that of the best foreign counterparts. Tests have shown these to be highly efficient in purifying sodium of oxygen and hydrogen and much less efficient in sodium purification of corrosion products and carbon. Taking into account the leakage of radioactive sodium during operation of the BN-600 reactor primary circuit traps, a decision was made to install the purification system in the reactor tank to improve the safety of the large fast reactor. It was resolved to exclude the accumulation of hydrogen in the primary circuit traps in nominal conditions. Two trap designs, with argon and sodium cooling, are discussed. It has been shown that operation of the reactor purification system with argon cooling will require 20 trap replacements during the reactor operating life and seven replacements if the deposition of hydrogen into the primary circuit cold traps is excluded. The sodium-cooled version of the trap built in the reactor tank has the same overall dimensions as the argon-cooled trap. The cooling sodium circulates in two trains: outside the jacketed working space body (up to 30% of the flow rate) and in the coil inside of the working space (up to 70% of the flow rate). Updates have been proposed to the trap design based on the calculations using the codes simulating the in-trap processes of heat and mass exchange.

Effect of Tungsten Carbidization on Gas Activation in Synthesis of Diamond Structures

With the aim of developing a gas-jet technique for depositing diamond structures, the flow of a hydrogen–methane mixture through hot coaxial tungsten cylindrical channels with a tungsten coil inside has been investigated. Emphasis has been placed on tungsten surface carbidization during gas-jet deposition and the influence of carbidization on the deposition rate and morphology of applied coatings. Several experiments on tungsten surface carbidization under different conditions for hydrogen–methane mixture supply have been conducted. Simulation of the mixture flow by direct simulation Monte Carlo method has been performed. Possible ways of how methane and its fragments fall on the surface of the coil has been discussed.

Thermal characteristics of evacuated tube solar collectors with coil inside: An experimental study and evolutionary algorithms

In this paper, the thermal characteristics of an evacuated tube solar collector for different volumetric flow rates of the fluid (10, 30 and 50 l/h) was experimentally improved by using copper oxide/distilled water (Cu2O/DW) nanofluid, and parabolic concentrator. Moreover, the effect of different volume fractions of the utilized nanofluid on the fluid properties, such as convective heat transfer coefficient, Nusselt number, and the useful gain of the collector was experimented. Finally, three artificial intelligence (AI) techniques namely, multi-variate adaptive regression spline (MARS), model tree (MT) and gene-expression programming (GEP) have been employed to predict the energy efficiency (ηІ) and inlet-outlet water temperature difference (ΔT). The input variables were volume of the storage tank (V), volume fraction of the nanofluid (VF), and mass flow rate of the fluid (M˙). The proposed AI methods presented robust formulations for prediction of ηІ and ΔT with an acceptable level of precision. The statistical results of AI models demonstrated that the MARS method can make a more accurate prediction of the collector performance than GEP and MT. It was also concluded that increase in both flow rate, and concentration of the nanofluid, lead to an increase in the thermal performance of the solar collector.

Evaluation study on an integration method for a DDQP using LCC and series compensation topologies for inductive power transfer

Nowadays, inductive power transfer is of great interest to the system working with electric power by virtue of its safety, reliability, and convenient characteristics. In fact, efficiency and compactness are the two parameters which play an important role in recharging electric vehicles. Double-D quadrature pad (DDQP) is a suitable magnetic structure that due to the use of an additional coil, can enhance the X-axis tolerance. Although there are several compensation methods to boost the efficiency, series and inductor-capacitor-capacitor (LCC) compensation types seem to be more practical and optimal. In this study, the LCC and series compensations are used together in the DDQP as the receiver side and calculated the value of the primary capacitor for enhancing the efficiency. Moreover, it is shown that, in the misaligned position which compensation has a better performance when utilising in the quadrature coil. Also, it is demonstrated that for making a system more compact, the quadrature and compensated coils integrated with the main coil in the secondary side do not have any significant effect on each other, neither on the other coils. Finally, the double-D pad transmitter and DDQP receiver with the integrated LCC compensation method is prototyped to verify the results.

Design, Simulation and Fabrication of A MEMS-based Double-layer Spiral Planar Inductor with Patterned Permalloy as Magnetic Layers

There have been significant efforts to boost the inductance value by adopting the sandwich structures using permalloy magnetic shielding layers. However, this structure will introduce high ac conductor losses and high eddy currents. In order to solve these problems, patterned permalloy can solve this problem effectively. According to the simulation results based on the application of finite element method in the frequency domain, the optimum permalloy pattern is which the blank of the permalloy are perpendicular to the coil inside. The double-layer planar inductor has a size of l5×1.5×0.1mm consisted of 13-turn spiral Cu coil for each layer and a 20μm-thick patterned permalloy magnetic shielding layer. The inductor shows a higher inductance than the traditional planar inductor. The patterned permalloy made the inductor more stable in high frequency than the none-patterned. And the inductor has an inductance of 1.3μH and quality factor of 2.8 at 1.5MHz, with an inductance per unit of 578nH/mm2, which is much higher than that in the reported literatures.

Optimal frequency for powering millimeter-sized biomedical implants inside an inductively-powered homecage.

This paper presents the optimal design and operation frequency (f) of an inductively-powered homecage for powering biomedical devices with millimeter (mm) dimensions, implanted inside the body of freely-behaving small animal subjects, for longitudinal behavioral neuroscience and electrophysiology experiments. In order to improve the power transmission efficiency (PTE) for powering mm-sized implants, the geometry of the multi-coil inductive links in the form of 3- and 4-coil links as well as fp need to be co-optimized. A simplified equation for the PTE of 3-coil inductive links for powering mm-sized implants has been derived, based on which the optimal geometries and fp of a 3-coil link have been found using a commercial field solver (HFSS). In simulations, the optimized 3-coil inductive link achieved a significant PTE of 2.56% at the optimal fp of 40 MHz for powering a 1 mm3 implant coil at the nominal height of 7 cm, thanks to the link and fp optimization as well as an intermediate coil in the receiver side with 18 mm diameter.

A low frequency hybrid harvester with ring magnets

Although many hybrid EH devices had been investigated by researchers, their performances at different operating resonance frequencies were not reported. Radial magnetic field was reported as the most efficient architecture to use in electromagnetic energy conversion, this was utilized in the design of a low frequency and efficient hybrid harvester comprising piezoelectric (PZT) and electromagnetic generators. FE simulation was used to obtain the magnetic field, design the coil and locate its position relative to the magnets. The electromagnetic generator consists of ring magnets which act as proof mass, with a hanging coil inside. The harvester was tested at frequency range of (34–40) Hz, produced maximum power of (710)μW. The maximum normalized power density and maximum efficiency of the harvester are (2.272) mW/cm3/g2 and (30.1%) respectively, at frequency of 36Hz and induced acceleration of (0.25)g. The new hybrid harvester has a higher normalized power density compared with others.

Analysis of the flow imbalance in the KSTAR PF cryo-circuit

The KSTAR PF cryo-circuit is a quasi-closed circulation system in which more than 370g/s of supercritical helium (SHe) is circulated using a SHe circulator. The heated helium from superconducting magnet is cooled through sub cooler (4.3K). The circulator is operated at 4.5K and 6.5bar, and the pressure drop of the circuit is kept at 2bar in order to maintain the supercritical state and circulator stability. The circuit is connected with helium refrigerator system, distribution system, and supercritical magnet system. It has a hundred branches to supply supercritical helium to the poloidal field superconducting magnet. The branch was designed to optimize the operation conditions and they are grouped for one cryogenic valve has the same length within the cardinal principle of the optimization. Five cryogenic valves are installed to control the mass flow rate, and seven orifice mass flow meters, differential pressure gauges and temperature sensors were installed in front of the magnet in the distribution because upper magnet and lower magnet is symmetric theoretically. The cryogenic pipe line was manufactured with elevation about 10m between upper magnet and lower magnet. The inlet and outlet helium feed-through were installed at the coil inside in case of KSTAR PF1–PF5 upper magnet and lower magnet. The flow imbalance is caused by void fraction and it could be changed due to manufacturing process even if it has the same length of cooling channel. This creates an imbalance among cooling channels and temperatures are slightly different. The flow was reduced and detoured due to the pressure rise rapidly at inlet and outlet during magnet operation. Therefore, the orifice mass flow meters are installed in front of the PF1–PF5 upper magnet and lower magnet in order to investigate flow trend and the thermos-hydraulic behavior is analyzed during PF magnet operation.

Self-Retaining Ureteral Stents: Analysis of Factors Responsible For Patients' Discomfort

To determine factors affecting patients' discomfort during the period self-retaining ureteral stents are in place. Between April 2001 and May 2003, 58 male and 42 female patients underwent temporary double-pigtail stenting. The indications were endopyelotomy in 39 patients, ureteroscopy in 32, laparoscopic pyeloplasty in 18, and endoureterotomy in 11. The stents were silicone in 56 patients and Percuflex in 44. The median stenting period was 8 weeks (range 4-16 weeks). Patient discomfort was evaluated by a questionnaire conducted by the physician before stent removal. Tested variables were patients' sex, side of the stent, urine culture, stent material, stent length and diameter, and stenting duration. The site of the upper coil (renal pelvis or calix), the site of the lower coil (in the same side or crossing the midline), and the shape of the lower coil (complete circle or not) were also tested. Univariate and multivariate analysis were carried out to determine significant independent variables, with P < 0.05 being significant. Of the total, 59 patients experienced discomfort consisting of dysuria, urgency, urge incontinence, loin pain, suprapubic pain, frequency, nocturia, or gross hematuria or some combination. Significant factors associated with discomfort were a positive urine culture, crossing of the lower end of the stent to the opposite side, caliceal position of the upper coil, and longer stenting duration. Proper positioning of the coils of the stent, eradication of infection, and shorter stenting duration are advised to decrease patient discomfort during the period of ureteral stenting.

Magnetic circuit switching element with superconducting coil

In an existing power system, high-current circuit breakers are widely used. Meanwhile, we propose a new switching device using a switching of magnetic paths. It is a magnetic circuit switch activated by on/off of superconducting coils wound on iron core-legs. We have carried out an experiment using a small experimental device with two superconducting coils (control coils). When the control coil is shorted, the voltage of the output coil in the shorted side becomes 0 V because the magnetic flux is blocked completely by the induced shielding current of the superconducting coil. It was confirmed that the current of the superconducting coil is decided by the turn-ratio of the coils both experimentally and theoretically. Therefore, it was assured that any tremendous overcurrent does not flow in the shorted superconducting control coils. After this, we applied this device into a model of two-circuit transmission system and confirmed the fundamental behavior in case of a line fault. The experimental result shows that the fault current is suppressed almost perfectly and the transmission system can continue the power transmission without any intermission.

Transcatheter Closure of Patent Ductus Arteriosus Using Occluding Spring Coils

The purpose of this study is to report our initial experience with the use of spring coils to close the patent ductus arteriosus in the dog. There are few large‐patient series reported in the veterinary literature. Coil closure was attempted in 15 dogs (median weight, 6.5 kg; range, 1.2 to 38.7 kg) presenting with a patent ductus arteriosus between May 1997 and May 1999. Arterial catheterization followed by angiography was used to decide if coil placement was adequate. A 5‐ or 8‐mm embolization coil, depending on the angiographic diameter of the ductus, was delivered, with 1 loop in the pulmonary arterial side and the remainder of the coil in the aortic side of the duct. Additional coils were used if a residual shunt was present, and closure was confirmed by aortography. Patients were discharged the day after the procedure. Successful coil closure, without residual shunt on angiography, was achieved in 11 of 13 dogs in which coils were released. In 6 dogs, a coil embolized to the pulmonary artery. Four of these dogs had successful closure with multiple coils, and 2 others had surgery. None of these dogs experienced adverse effects. In 2 dogs with conical patent ductus arteriosus &gt;5 mm in minimal diameter, coil closure was not done. We conclude that the patent ductus arteriosus size and anatomical shape are crucial in deciding whether coil closure is the method of choice. In selected cases, coil closure represents an elegant alternative to surgical ligation. Although pulmonary embolism occurred commonly, it did not cause any obvious clinical problem.

A dynamic mathematical model of a direct expansion (DX) water-cooled air-conditioning plant

A dynamic mathematical model for a direct expansion water-cooled air-conditioning plant typical to many actual installations in buildings has been developed. The system components modelled are a compressor, a thermostatic expansion valve, a water cooled condenser and a direct expansion evaporator which is also the cooling and dehumidifying coil in the air side. The evaporator (cooling coil) model consists of a novel set of equations which can distinguish between two-phase superheated and refrigerant region in the refrigerant side, and between dry and wet cooling of an air handling process in the air side. The model has been validated using the experimental data collected from the plant, and was separately reported.

Transcatheter closure of patent ductus arteriosus using occluding spring coils.

The purpose of this study is to report our initial experience with the use of spring coils to close the patent ductus arteriosus in the dog. There are few large-patient series reported in the veterinary literature. Coil closure was attempted in 15 dogs (median weight, 6.5 kg; range, 1.2 to 38.7 kg) presenting with a patent ductus arteriosus between May 1997 and May 1999. Arterial catheterization followed by angiography was used to decide if coil placement was adequate. A 5- or 8-mm embolization coil, depending on the angiographic diameter of the ductus, was delivered, with 1 loop in the pulmonary arterial side and the remainder of the coil in the aortic side of the duct. Additional coils were used if a residual shunt was present, and closure was confirmed by aortography. Patients were discharged the day after the procedure. Successful coil closure, without residual shunt on angiography, was achieved in 11 of 13 dogs in which coils were released. In 6 dogs, a coil embolized to the pulmonary artery. Four of these dogs had successful closure with multiple coils, and 2 others had surgery. None of these dogs experienced adverse effects. In 2 dogs with conical patent ductus arteriosus >5 mm in minimal diameter, coil closure was not done. We conclude that the patent ductus arteriosus size and anatomical shape are crucial in deciding whether coil closure is the method of choice. In selected cases, coil closure represents an elegant alternative to surgical ligation. Although pulmonary embolism occurred commonly, it did not cause any obvious clinical problem.

An evaluation of the inlet flow reduction for a cable in conduit conductor by rapid heating

The flow reduction of forced flow superconducting coil with a cable in conduit (CIC) conductor has been studied for AC losses due to pulsed operation. In this paper, the flow reduction by rapid heating is described for forced flow superconducting coil with a CIC conductor. The phenomenon of flow reduction of the forced flow coil has been applied for coil quench detection and has been developed by Japan Atomic Energy Research Institute (JAERI). It is named the “fluid method” and essential technology for quench detection of large-scale forced flow superconducting coil as fusion magnets and superconducting magnetic energy storage (SMES) coil. In the fluid method, the inlet flow reduction is caused by Joule heating on the normal zone of superconducting coil. The fluid method has no electric noise in its detection. This is an advantage for pulsed operation in comparison with other electrical quench detection systems. On the other hand, there are no quantitative considerations between the inlet flow reduction and Joule heating of the coil inside in previous studies. The flow reduction for the quench detection has been determined by the operation experience of forced flow superconducting coil. The purpose of this paper is an estimation of the relation between the inlet flow reduction and Joule heating at coil quench. First, the inlet flow reduction was obtained by experiment in which the sample has an inductive heater for the quench emulation. Second, the evaluation model was proposed and its model showed good agreement between the inlet flow reduction and heat generation of the coil inside by rapid heating as coil quench.