Vertical Coil Research Articles

Short-Period Superconducting Undulator Coils With Neutral Poles: Test Results

The success in creating new bright magnetic structures of synchrotron radiation (SR) sources allows generation of subnanometric-emittance electron beams. This has motivated many SR centers to upgrade the old structures to increase the brightness of the SR sources. Smaller emittance imposes higher requirements on the generators of undulator radiation. With the advent of new materials, the production of undulators on permanent magnets has progressed greatly. Superconducting undulators are less common, but as sources of undulator radiation they are much more promising than undulators with permanent magnets. This paper presents test results of a prototype superconducting undulator magnet using active and neutral poles with a period of 15.6 mm and an operational field of ~1.2 T. A pole gap of 8 mm provides a vertical aperture of 6 mm for an electron beam. In contrast to the traditional type of undulator with vertical racetrack coils, in this type of undulator the coils are of the horizontal racetrack type. The magnet design consists of the aluminum-alloy frame, into which individual poles are inserted. The design can significantly improve the manufacturing accuracy and, ultimately, reduce the phase errors. The coils are made of NbTi/Cu superconducting wires, which will be indirectly cooled by cryocoolers in own cryostat to the temperature of liquid helium.

Heat transfer phenomena on waste heat recovery of combustion stack gas with deionized water in helical coiled heat exchanger

Theoretical and experimental studies on waste heat recovery of combustion stack gas and heat transfer phenomena of a fully developed laminar flow of deionized water in vertical helical coils were carried out with coil dimensions: tube diameter to coil diameter ,di/D=0.04−0.06 and pitch to coil diameter, p/D=0.1−0.25. The calculation of heat transfer data was based on countercurrent flow LMTD method. The result showed that deionized water (DI-water) possessed better heat transfer than that of normal water. The effect of coil pitch, coil diameter, and coiled tube diameter on heat transfer phenomena of helical coils had been discussed and a new set of correlation of heat transfer data was created and it could be found that the results from the correlation agreed well with the experimental data. In addition, the overall heat transfer coefficient between the hot exhaust gas and the heat transfer fluid in the helical coil was also considered. Smaller tube diameter gave better overall heat transfer coefficient at low water-side Reynolds number and when the Reynolds number was over 3500 the bigger tube diameter showed the advantage. Smaller coil diameter seemed to get better overall heat transfer coefficient at low water-side Reynolds number.

On the control system preparation for ELM pacing with vertical kicks experiments at TCV

High confinement plasma regimes (H-mode) are the scenarios with the highest fusion rates and the operating regime foreseen for the ITER scenario with QDT = 10. The steep gradients of density and temperature drive magnetohydrodynamic (MHD) edge localized modes (ELMs). Although ELMs are beneficial for controlling particle exhaust and plasma impurities, the excessive energy they deposit on the plasma facing components may lead to erosion or melting, reducing the components life cycle. By controlling the ELM frequency in an ELMy H-mode plasma it may be possible to reduce the energy expelled per ELM, mitigating damage to the tokamak parts.One technique for mitigating these risks was first implemented successfully in TCV Ohmic H-mode plasmas, using the so called ELM pacing with vertical kicks [1]. TCV vertical stabilization coils located inside the vessel proved to be well suited to apply the necessary perturbations to induce vertical displacements of the plasma. This method was then reproduced on AUG [2,3] and later on JET [4] with significant improvements.During 2016 a set of experiments were planned to further study the physics of ELM pacing taking advantage of the new neutral beam heating (NBH) system installed on TCV [5]. This submission reports on the related preparation of the TCV digital vertical stabilization control system [6] actuating the in-vessel coils. A number of tools were deployed to drive a fast radial-field variation and preliminary experimental validation was carried out. The tools and simulations, as well as preliminary experiments aiming at evaluating the controller's accuracy are reported.

Dihydroxyacetone levels in electronic cigarettes: Wick temperature and toxin formation.

Recently, we reported the presence of dihydroxyacetone (DHA), the active ingredient in sunless tanners, in the aerosol of an electronic cigarette. DHA has been shown to react with DNA in vitro. The FDA restricts the use of DHA to external application only. It states that it should not be inhaled, ingested, or come into contact with any areas containing mucous membranes, due to unknown risk. Herein, the quantification of DHA in the aerosols of three brands of e-cigarettes has been carried out. These included two devices with horizontal heating coil configurations as well as one with a sub-ohm resistance vertical heating coil. In order to understand and begin to address the origin of DHA and related aerosol products, the wicking properties of the three e-cigarettes were compared. DHA levels were analyzed by a combination of GS/MS and 1H NMR. DHA was found in all three e-cigarettes, with substantially less in the sub-ohm, vertical coil device as compared to the horizontal coil devices (e.g., 0.088 μg/puff vs. 2.29 μg/puff, respectively). Correspondingly, the temperature of the wet layer of the wick for the vertical coil was relatively stable, compared to the wicks for the horizontal coils, upon increasing battery power output. This result is in agreement with prior studies of e-cigarette wicking efficiency and aerosol toxin formation. The temperature measurements reported are a simple means for comparing devices with different design properties during operation.

Experimental Study of Condensation Heat Transfer in Helical Coil Heat Exchanger

Helical coils are used as one of the heat transfer enhancement techniques in many engineering applications such as in nuclear industry, chemical and petrochemical industries, HVAC systems, and many other engineering applications. In nuclear industry, helical coils are used as a method for exchanging heat in large sodium-cooled fast breeder reactor. In comparison with straight-tube heat exchangers, rate of heat transfer for helical coil heat exchanger is significantly high. This is due to secondary flow pattern in planes normal to the main flow direction of fluid in the helical coiled tube. The present work is an experimental investigation on heat transfer characteristics during steam condensing inside a small diameter vertical helical coil tube with the cooling water flowing in the shell in counter flow direction. The effect of mass flow rate and saturation temperature of steam on the heat transfer coefficient is investigated and plotted. The results confirm the significant improvement in the heat transfer coefficient for condensation of steam.

New void fraction equations for two-phase flow in helical heat exchangers using artificial neural networks

In this research, two new empirical equations based on Artificial Neural Network (ANN) were developed to determine the new void fraction in two-phase flow inside helical vertical coils with water as work fluid. The first model included vapor fraction (xg), density ratio ρgρl, viscosity ratio μlμg, and curvature ratio dD, as input variables, and 2 neurons in the hidden layer to predict satisfactorily the void fraction. In order to simplify the model, a second model of ANN was proposed without curvature ratio. The best architecture to the second model, with 3 input variables, was also with 2 neurons in the hidden layer. The coefficients of determination were R2 > 0.9 to both models. The ANN models of void fraction satisfied the interval condition of 0–1. Therefore, both models have been considered to be satisfactory for predicting the behavior of void fraction of a two-phase flow. To validate these new void fraction equations, three different helical heat exchangers described in previous works reported, were applied in two ways: first, experimental and simulated heat fluxes were compared using steady state test data from two helical double-pipe vertical evaporators integrated into two absorption heat transformers; second, experimental and simulated heat fluxes were also compared in an innovative design prototype full-scale helically coil steam generator in which, numerical results for pressure along the tube reveal a better way to represent the two-phase flow. The second evaluation also provided evidence on the successful extrapolation of simple ANN equations of void fraction in function of dimensionless numbers. The analyses of the contribution of input variables in the ANN model showed that the curvature ratio could not impact the simulative accuracy of void fraction under the experimental conditions worked.

Orientation effect in helical coils with smooth and rib-roughened wall: Toward improved gas heaters for supercritical carbon dioxide Rankine cycles

Helical coils have gained increasingly interest in the field of supercritical carbon dioxide (SCCO2) Rankine cycles during the last decade due to the compact structure and high heat transfer rate. Past studies mainly focused on effects of operating conditions and the gravitational buoyancy, and are not sufficient to fully understand the behavior of SCCO2 helically coiled gas heaters. Influence of some other key factors, such as the coil orientations and internal wall roughness, on overall performance has been seldom reported and is still unclear to date. In this work we filled this gap with a solid-to-fluid conjugate heat transfer model where supercritical flow turbulence is solved by the Shear-Stress Transport k-ω equations. The orientation effect on performance of helical coils was revealed with the coil axis arranged in horizontal, vertically upward and downward directions, respectively. Results demonstrate that the criterion of Bo < 10−5 for negligible buoyancy effect was applicable to coils with dimensionless curvature δ = 0.01–0.1. The Orientation effect only emerged when the buoyancy effect became significant with Bo > 10−5. Deterioration and enhancement of heat transfer occurred alternatively in horizontal coils. The overall performance of horizontal coils was much worse than vertical coils, among which the downward orientation was slightly better than the upward one. The increase of δ barely improved the performance of horizontal coils. Instead, at larger δ the intensive fluctuation in heat transfer coefficients was more frequent due to the more drastic change of the flow direction. The location and extent of local impairment also varied with the inlet arrangement. Finally, the passive compound enhancement technique of helical coils in conjunction with internal helical-rib roughness was found to be very effective in mixed convection of SCCO2, especially in the horizontal coils.

Analysis of Radiation Transport due to Activated Coolant in the ITER Neutral Beam Injection Cell

Detailed spatial distributions of the biological dose rate due to a variety of sources are required for the design of the ITER tokamak facility to ensure that all radiological zoning limits are met. During operation, water in the Integrated loop of Blanket, Edge-localized mode and vertical stabilization coils, and Divertor (IBED) cooling system will be activated by plasma neutrons and will flow out of the bioshield through a complex system of pipes and heat exchangers. This paper discusses the methods used to characterize the biological dose rate outside the tokamak complex due to 16N gamma radiation emitted by the activated coolant in the Neutral Beam Injection (NBI) cell of the tokamak building.Activated coolant will enter the NBI cell through the IBED Primary Heat Transfer System (PHTS), and the NBI PHTS will also become activated due to radiation streaming through the NBI system. To properly characterize these gamma sources, the production of 16N, the decay of 16N, and the flow of activated water through the coolant loops were modeled. The impact of conservative approximations on the solution was also examined. Once the source due to activated coolant was calculated, the resulting biological dose rate outside the north wall of the NBI cell was determined through the use of sophisticated variance reduction techniques. The AutomateD VAriaNce reducTion Generator (ADVANTG) software implements methods developed specifically to provide highly effective variance reduction for complex radiation transport simulations such as those encountered with ITER. Using ADVANTG with the Monte Carlo N-particle (MCNP) radiation transport code, radiation responses were calculated on a fine spatial mesh with a high degree of statistical accuracy. Advanced visualization tools were also developed and used to determine pipe cell connectivity, to facilitate model checking, and to post-process the transport simulation results.

Comparison of 12 Quadrature Birdcage Coils with Different Leg Shapes at 9.4 T

The purpose of this study was to analyse the relationship between the radio frequency (RF) coil performance and conductor surface shape for ultra-high field (UHF) magnetic resonance imaging. Twelve different leg-shaped quadrature birdcage coils were modeled and built, e.g., 4 mm-width-leg conventional birdcage coil, 7 mm-width-leg conventional birdcage, 10 mm-width-leg conventional birdcage coil, 13 mm-width-leg conventional birdcage coil, inside arc-shape-leg birdcage coil, outward arc-shape-leg birdcage coil, inside right angle-shape-leg birdcage coil, outward right angle-shape-leg birdcage coil, vertical 4 mm-width-leg vertical birdcage, 6 mm-width-leg vertical birdcage, 8 mm-width-leg vertical birdcage and 10 mm-width-leg vertical birdcage. Studies were carried out in both electromagnetic simulations with finite element method as well as in vitro saline phantom experiments at 9.4 T. Both the results of simulation and experiment showed that conventional birdcage coil produces the highest signal-to-noise ratio (SNR) while the vertical birdcage coil produces the most homogeneous RF magnetic (B 1) field at UHF. For conventional birdcage coils, as well as the vertical birdcage coils, only the proper width of legs results in the best performance (e.g., B 1 homogeneous and SNR). For vertical birdcage coils, the wider the leg size, the higher RF magnetic (B 1) field intensity distribution.

Establishment of KRISS watt balance system to have high uniformity performance

Watt balance system is the promising equipment to determine Planck constant without accurate measurement of magnetic flux and coil length. To obtain high measurement uncertainty, uniform magnetic flux density and constant velocity control are required during the coil movement. For that KRISS watt balance system incorporates a closed-type cylindrical permanent magnet, vertical linear motor and piston guide. In this paper, the vertical actuating motor including piston guide is controlled to have constant speed and magnet assembly was fabricated to have high uniform magnetic flux density during the vertical coil movement. The velocity of moving coil was controlled within 4 × 10-3 (1σ) at the velocity of 2 mm s-1 using a linear motor and linear encoder feedback. Using 3-vertical homodyne laser interferometer the velocity ripple of coil located inside magnet is measured within the level of 7.35 × 10-3 (1σ) at the same speed. A magnet assembly, which consists of two permanent magnet rings and closed yokes, was fabricated. A flux shunt was designed for the magnet for minimizing the temperature effect. The yokes were divided into three parts: top, center, and bottom yokes. By re-machining of center outer yoke, magnetic flux density uniformity was improved. The uniformity of the magnetic field was within 3.9 × 10-4 over a vertical distance of 20 mm.

Numerical studies of a helical coil once-through steam generator

A Thermal Hydraulic analysis code for Helical Coil once-through Steam Generator (TH-HCSG) is developed in the present study in order to predict the heat transfer process and thermal hydraulic characteristics in vertical helical coil steam generators. The numerical model is programmed using a one-dimensional four-equation drift-flux model and evaluated according to the data on HCSG published by the International Reactor Innovative and Secure (IRIS). The results achieved under full load conditions are, then, compared with the RELAP5 codes, with the results of this comparison showing that this model is both correct and reliable and can be used to investigate the instantaneous characteristics of helical coil steam generators. This model is also used to evaluate the influence of the main representative HCSG boundary parameters on HCSG operation characteristics. It was subsequently found that, when there was a ±10% step change in the boundary parameters, the length of the single-phase water region in the secondary side of the HCSG changed considerably, so that the steam flow oscillated obviously, lagging the feedwater flow at an early stage and rapidly reaching a steady state as the water capacity of the secondary side of the HCSG was changed.

Experimental and theoretical investigations of special type coil heat exchanger with the nanofluid buffer layer

The paper presents the results of experimental and theoretical investigations of special type of coil heat exchanger. The tested device is equipped with three vertical coils and the temperature stratification system. Water is a heating medium in two coils. The refrigerant transferring the waste heat from air conditioning system is the heating medium in the third coil. The finned pipe of this coil has a double wall in which the annular buffer layer with nanofluid is mounted. Thermophysical properties of the applied water based Cu nanofluid cause the enhancement of heat transfer through the buffer layer. The paper presents thermal characteristics of the exchanger received on the basis of measurements performed on the industrial test stand. Measurements were conducted during the operation of the coil with refrigerant. Heat loss to the surroundings, distributions of water temperature in the storage tank, changes of water temperature in time and thermal power of the coil heat exchanger were obtained. The measurement results were compared with those received on the basis of theoretical analysis of the exchanger.

A Novel Compact Model for On-Chip Vertically-Coiled Spiral Inductors

A novel compact model for on-chip vertically coiled spiral inductors is presented. The vertical metal coils are modeled by a ladder network consisting of ideal inductors and resistors. The skin and proximity effects are taken into consideration. The capacitive parasitics between relevant metal layers are modeled. A method to analytically extract the model parameters is proposed. The model prediction shows excellent agreement between the data from both simulation and measurement over the frequency range of 0.1---66.1 GHz, for a vertically coiled spiral inductor manufactured in TSMC 90 nm RF CMOS technology.

A new analytical solution for horizontal geothermal heat exchangers with vertical spiral coils

Horizontal geothermal heat exchangers (HGHEs) with vertical spiral coils have been increasingly used in ground source heat pump (GSHP) systems. Research studies have been conducted using field tests and simulations trying to reveal the heat transfer mechanism of HGHEs with vertical spiral coils and to provide a good heat transfer performance. However, there is no analytical solution has been established for HGHEs with vertical spiral coils. Of particular interest is the temperature variation at the soil surface. The study presented in this paper proposes the development of a mathematical vertical ring-coil model used to describe the heat transfer process of HGHEs with vertical spiral coils. In this new model, the spiral heat exchanger is simplified as a series of ring coils that inject/extract heat in/from a semi-infinite medium. A single ring model in an infinite medium is first introduced. Using images and superposition, a multiple ring-coils analytical solution is then given. The significant influence on the heat transfer performance of HGHEs temperature variation of the ground surface is then considered. A periodically changed boundary condition is being taken into consideration in the modeling process. The validity of the model was examined by a field test and a 3-D simulation model. The analytical solutions may provide a desirable and better tool for the simulation/design HGHEs with vertical spiral coils.

A novel design of feedback control system for plasma horizontal position in IR-T1 tokamak

Determination of accurate plasma horizontal position during plasma discharge is essential to transport it to a control system based on feedback. By using the plasma-circuits linearized model, Proportional Integral Derivative (PID) based controllers and a first order transfer function representing the power supply (PS) dynamics of vertical coil system for IR-T1 tokamak, we analyzed step feedback response of the overall system of IR-T1 tokamak and corresponding Bode diagrams for two cases with and without the plasma resistance and the eddy currents distribution. Also we did experiments for determination of plasma horizontal displacement in this tokamak. This work is done by four magnetic probes that are installed on the circular contour of the tokamak. This data used as input to the feedback controller to validate the performance of it. Results of feedback response analysis show that the controller has good performance. Due to approximations in the controller design, construction, installation and implementation of the controller is necessary and this is the purpose of our future works.

Mass and heat transfer at the outer surface of helical coils under single and two phase flow

The mass transfer behavior of the outer surface of vertical helical coil was studied by the electrochemical technique under single phase flow, gas sparging and two phase flow. Variables studied were helical tube diameter, physical properties of the solution, solution velocity and superficial gas velocity. The mass transfer data were correlated by dimensionless equations. Mass transfer enhancement ratio in case of two phase flow ranged from 1.1 to 4.9 compared to single phase flow. Implication of the results for the design and operation of helical coil reactors used to conduct L–S exothermic diffusion controlled reactions which need rapid temperature control were outlined. In this case the inner coil surface will act as a cooler while the outer surface will act a reaction surface. Immobilized enzyme catalyzed biochemical reactions where heat sensitive materials may be involved represent an example for the reactions which can employ the helical coil reactor. Also the importance of the results in the design of and operation of diffusion controlled membrane processes which employ helical coil membrane was noted.In view of the analogy between heat and mass transfer the possibility of using the results in the design and operation of helical coil heat exchangers was highlighted.

Experimental investigations on destroying surface tension of melted frost for defrosting performance improvement of a multi-circuit outdoor coil

When frost forms and accumulates over the outdoor coil’s surface in an air source heat pump (ASHP) unit, system operating performance will be adversely affected. Currently, reverse cycle defrosting is the most widely used standard defrosting method. A previous related study suggested that, for an ASHP unit with a multi-circuit outdoor coil, water collecting trays installed between circuits could eliminate the negative effects of downwards flowing melted frost due to gravity. However, for a vertical multi-circuit outdoor coil with separations, there is also a lot of melted frost remained on the downside surface of each circuit due to surface tension. The remained water would consume energy, and thus deteriorate system defrosting performance. To quantitatively study the negative effects of surface tension, in this paper, an experimental study changing the vertical multi-circuit outdoor coil into horizontally installed in an ASHP unit was conducted. Compared with the surface tension kept, defrosting duration could be shorted from 186s to 167s, or 20s less, and defrosting efficiency improved from 49.4% to 61.4%, or 12.0% more, when the remained water cleaned as the surface tension destroyed.

Coil Heat Exchanger with the Nanofluid Filled Buffer Layer

The paper presents the preliminary design of the special heat exchanger. The device under consideration is the kind of immersed coil heat exchangers. It consists of three vertical coils: two coils are standard, water is used as a heating medium; one coil is filled by the refrigerant R134a which transfers the waste heat from refrigeration and air conditioning system during the boiling processes. In order to prevent the possible refrigerant leakage, the special buffer layer filled with the nanofluid is mounted in the Freon coil. Thermophysical properties of the nanofluid cause the intensification of the heat transfer through the buffer layer and the same increase of the heat transfer rate. Calculations of thermal power were made. Correlations of heat transfer coefficients in curved tubes, pressure drop correlations for flow through helical coil tubes and correlations describing the heat transfer in the buffer layer, were applied. Results of the calculations indicate of the influence of of Freon coil on the exchanger heat transfer rate. Heat power of Freon coil is about 7 – 25% of water coil thermal power. Thus, the waste heat applied significantly increases the exchanger heat transfer rate.

Depreissia decipiens, an enigmatic canopy spider from Borneo revisited (Araneae, Salticidae), with remarks on the distribution and diversity of canopy spiders in Sabah, Borneo.

Depreissia is a little known genus comprising two hymenopteran-mimicking species, one found in Central Africa and one in the north of Borneo. The male of Depreissia decipiens is redescribed, the female is described for the first time. The carapace is elongated, dorsally flattened and rhombus-shaped, the rear of the thorax laterally depressed and transformed, with a pair of deep pits; the pedicel is almost as long as the abdomen. The male palp is unusual, characterized by the transverse deeply split membranous tegulum separating a ventral part which bears a sclerotized tegular apophysis and a large dagger-like retrodirected median apophysis. The female epigyne consists of one pair of large adjacent spermathecae and very long copulatory ducts arising posteriorly and rising laterally alongside the spermathecae continuing in several vertical and horizontal coils over the anterior surface. Relationships within the Salticidae are discussed and an affinity with the Cocalodinae is suggested. Arguments are provided for a hypothesis that Depreissia decipiens is not ant-mimicking as was previously believed, but is a mimic of polistinine wasps. The species was found in the canopy in the Kinabalu area only, in primary and old secondary rainforest at 200–700 m.a.s.l. Overlap of canopy-dwelling spider species with those in the understorey are discussed and examples of species richness and endemism in the canopy are highlighted. Canopy fogging is a very efficient method of collecting for most arthropods. The canopy fauna adds an extra dimension to the known biodiversity of the tropical rainforest. In southeast Asia, canopy research has been neglected, inhibiting evaluation of comparative results of this canopy project with that from other regions. More use of fogging as a collecting method would greatly improve insight into the actual species richness and species distribution in general.

Power consumption, gas holdup, and mass‐transfer coefficient of triple‐impeller configurations in a stirred vessel with vertical tubular coils

AbstractThree kinds of impeller combinations (3 × 4WHd, HB + 2 × 4WHd, 2 × HB + 4WHd) were used to investigate the effects of coil baffles on system power consumption, gas holdup, and mass transfer coefficient. The experiments were performed in a dish‐bottomed vessel with a diameter of 0.29 m. Results of the power consumption experiments show that at the same rotation speed and an increasing rate of gas flow, the power consumptions of 3 × 4WHd and 2 × HB + 4WHd with coil baffles are almost the same as that of a system with four planar baffles, but there is a clear power draw for the HB + 2 × 4WHd combination. At rotational speeds of 250–350 rpm, the largest power draws for the 2 × HB + 4WHd, HB + 2 × 4WHd, and 3 × 4WHd impeller combinations equipped with coil baffles are 27, 25, and 15 %, respectively. The gas holdup experiment shows that with installation of coil baffles in the vessel, axial and radial impeller combinations can achieve gas dispersion identical to that attained with planar baffles. At the same power input and superficial gas rate over a wide range of gas velocities, the kLa values of the coil baffles for the 3 × 4WHd and 2 × HB + 4WHd combinations are almost identical to those of a conventional system with four baffles. However, in the HB + 2 × 4WHd system, kLa values of the coil baffles are 15 % higher than for planar baffles at low gas velocities and 30 % higher at high superficial gas rates. Finally, all data from the experiments on gas holdup and kLa values may be correlated through the equations and .