Top Coil Research Articles

The ultrasound effects on the formation of the solidification structure of A356 ingots processed via a 2-zone induction melting furnace

To study the formation of the solidification structure including the columnar-to-equiaxed transition (CET) under the influence of ultrasound, a 2-zone furnace system and an ultrasound equipment were utilized. The 2-zone furnace system consists of an induction furnace with a top coil and a bottom coil, a graphite crucible, and. a water-cooled chill block located at the bottom of the crucible. By controlling both the top and bottom coil output power independently, the furnace can create various temperature gradients and cooling rates in different regions of the graphite crucible. The ultrasound probe was inserted at the top of the crucible. The top of the crucible was also thermally insulated. Temperature measurements were performed at different locations in the crucible. Optical microscopy was used to characterize the microstructure of the A356 cylindrical ingots. The effects of ultrasound on the microstructure formation during solidification of A356 alloy was studied. A numerical model was developed to compute the temperature gradients and mushy zone evolution in the crucible and to assist in developing of solidification maps.

A novel approach for modelling thermal energy storage with phase change materials and immersed coil heat exchangers

A novel modelling approach is presented for a thermal energy storage system with immersed coil heat exchangers. The energy store consists of a water tank in which rectangular phase change material (PCM) modules are submerged. The immersed coil heat exchangers are placed at the bottom and top sections of the tank for charging and discharging, respectively. This design promotes thermal mixing inside the tank when charged from the bottom coil and discharged from the top coil. In addition, the location of the coil heat exchangers favorably limits the heat transfer when charged through the top coil or discharged through the bottom coil giving rise to the thermal diode effect. PCMs can offer large storage capacity since they store large amounts of thermal energy in the form of latent heat of phase change (solid-liquid). This paper proposes a simplified physics-based numerical model of the heat transfer and phase change in the thermal storage tank. The model discretizes the storage tank one-dimensionally into three fully-mixed control volumes; two control volumes surrounding the immersed coil heat exchangers and one control volume in the middle of the tank including the PCM modules. All the heat transfer dynamics between the control volumes, the heat exchangers and the PCM modules are considered. Experimental validations, using a full-scale test facility, are carried out for systems with and without PCMs under various operation scenarios and the results are found to agree well within the experimental uncertainties. Such model potentially provides high computational efficiency that is desirable in simulating the performance of storage systems under long-term operations.

Contactless ultrasonic treatment of melts using EM induction

Ultrasound Treatment (UT) is commonly used in light alloys during solidification to refine microstructure, or disperse immersed particles. A sonotrode probe introduced into the melt generates sound waves that are strong enough to produce cavitation of dissolved gases. The same method cannot be used in high temperature melts, or for highly reactive alloys, due to probe erosion and melt contamination. An alternative, contactless method of generating sound waves is proposed and investigated theoretically in this paper, using electromagnetic (EM) induction. In addition to strong vibration, the EM induction currents generate strong stirring in the melt that aids distribution of the UT effect to large volumes of material. In a typical application, the same induction coil surrounding the crucible used to melt the alloy may be adopted for UT with suitable frequency tuning. Alternatively - or in addition - a top coil may be used. For industrial use, instead of multiple sonotrodes as has been the practice in scaling up, modelling shows that one simply has to alter the coil geometry and current to suit. To reach sinusoidal pressure fluctuations suitable for cavitation it may be necessary to tune the induction coil frequency for resonance, given the crucible dimensions.

Contactless Ultrasound Generation in a Crucible

Ultrasound treatment is used in light alloys during solidification to refine microstructure, remove gas, or disperse immersed particles. A mechanical sonotrode immersed in the melt is most effective when probe tip vibrations lead to cavitation. Liquid contact with the probe can be problematic for high temperature or reactive melts leading to contamination. An alternative contactless method of generating ultrasonic waves is proposed, using electromagnetic (EM) induction. As a bonus, the EM force induces vigorous stirring distributing the effect to treat larger volumes of material. In a typical application, the induction coil surrounding the crucible—also used to melt the alloy—may be adopted for this purpose with suitable tuning. Alternatively, a top coil, immersed in the melt (but still contactless due to EM force repulsion) may be used. Numerical simulations of sound, flow, and EM fields suggest that large pressure amplitudes leading to cavitation may be achievable with this method.

Experimental investigations on the influence of ice floating in an internal melt ice-on-coil tank

In this paper, the discharge of an experimental ice-storage tank is analyzed. The storage tank is an internal melt-ice-on-coil system. The discharge process has been studied for different mass flow rates and supply temperatures in the range from 10°C to 15°C. The results indicate that once the ice breaks and floats toward the top of the tank, convection in the ice/water mixture is enhanced and the heat transfer fluid in the top coils becomes colder than in the bottom coils. Thus, an increase of the cooling power is generally observed around the ice-breaking point. Two correlations have been developed to reproduce the effect of the mass flow rate and supply temperature on the discharge duration and the mean cooling power.

Design, simulation, fabrication and characterization of a micro electromagnetic vibration energy harvester with sandwiched structure and air channel

This paper presents the design, simulation, fabrication and characterization of a novel electromagnetic vibration energy harvester with sandwiched structure and air channel. It mainly consists of a top coil, a bottom coil, an NdFeB permanent magnet and a nickel planar spring integrated with silicon frame. The prototype is fabricated mainly using silicon micromachining and microelectroplating techniques. The tested natural frequency of the magnet–spring system is 228.2Hz. The comparison between the simulation and the tested results of the natural frequency shows that the Young's modulus of microelectroplated Ni film is about 163GPa rather than 210GPa of bulk Ni material. Experimental results indicate that the sandwiched structure and the air channel in the silicon frame of the prototype can make the induced voltage increase to 42%. The resonant frequency of the prototype at 8m/s2 acceleration is 280.1Hz, which results from the nonlinear behavior of the magnet–spring system. The load voltage generated by the prototype is 162.5mV when the prototype is at resonance and the input vibration acceleration is 8m/s2 and the maximal load power obtained is about 21.2μW when the load resistance is 81Ω.

Design and application of a flexible and implantable sensor for detecting uterine musculature contraction

It is very important to obtain the parameters of deformation size and contraction frequency of women's uterine musculature in medical research. This paper proposes a type of sensor for measuring these parameters and analyzes its force situation. The flexibility of the sensor makes it easy for doctors to let the sensor pass through woman's narrow cervix and get to her uterine cavity. The experiment shows that the sensitivity of three coils in the sample sensor achieves 22.38 nH/mm 2 both for left and right coils, 22.84 nH/mm 2 for top coil, which can meet the requirements of sensitivity for testing the contraction situation of uterine musculature. Furthermore, an interface designed in the back end system can display the parameters of deformation size and vivid contraction situation of women's uterine musculature in real-time. The sensor has been applied in some medical fields.

Design of the new magnetic sensors for Joint European Torus

A new magnetic diagnostics system has been designed for the 2005 Joint European Torus (JET) experimental campaigns onward. The new system, which adds to the existing sensors, aims to improve the JET safety, reliability, and performance, with respect to: (i) equilibrium reconstruction; (ii) plasma shape control; (iii) coil failures; (iv) VDEs; (v) iron modeling; and (vi) magnetohydrodynamics poloidal mode analysis. The system consists of in-vessel and ex-vessel sensors. The former are a set of 38 coil pairs (normal and tangential), located as near as possible to the plasma. Coils are generally grouped in rails, in order to ease remote handling in-vessel installation. The system includes: (i) two outer poloidal limiter arrays (2×7 coil pairs); (ii) two divertor region arrays (2×7 coil pairs); and (iii) two top coil arrays (2×5 coil pairs). Ex-vessel sensors, including discrete coils, Hall probes, and flux loops (26 in total) will be installed on the iron limbs, in order to provide experimental data for the treatment of iron in equilibrium codes. The design is accompanied by a software analysis, aiming to predict the expected improvement.

The toroidal coll planet centrifuge without rotating seals applied to countercurrent chromatography

A new high-performance, compact table top coil planet centrifuge is introduced. The apparatus holds a long fine coiled column wound on a large diameter drum-shaped holder. Synchronous planetary motion of the holder not only allows continuous elution without the use of rotating seals, but also provides an ideal acceleration field which enables retention of the stationary phase and efficient mixing of the two solvent phases in the coiled column. Potential capabilities of the apparatus was demonstrated on separation of a set of dinitrophenyl amino acids using a two-phase solvent system composed of CHCl 3/CH 3COOH/0.1 n HCl at a 2/2/1 volume ratio. With a column consisting of 8500 helical turns partition efficiencies ranging between 6000 and 2000 theoretical plates were attained. The capability of the present scheme may be extended to partition of cells and macromolecules with polymer phase systems and to cell elutriation with physiological solutions.