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The saddle shaped secondary helical coil electromagnetic launcher, which has the advantage of long-distance propulsion is improved on the basis of helical coil electromagnetic launcher (HEML). However, the current fluctuation of the system is the same as that of the traditional helical coil electromagnetic launcher, and current fluctuation can cause thrust fluctuation and commutation arc problems. Therefore, it is particularly important to analyse the commutation current fluctuation of the saddle shaped secondary HEML. In this paper, the commutation process of HEML is analysed in detail by analogy with the commutation process of DC series excited rotating motor. Then the system model is built in ANSYS/Maxwell, and the excitation circuit is built with Simplorer to jointly simulate the system. The reason of commutation current fluctuation is analysed by using the principle of flux continuity, and the correctness of the principle of flux continuity is verified by analysing and calculating the simulation datas. It has a good guiding significance for the subsequent improvement of thrust fluctuation and commutation arc.

Helical coil heat exchanger is used in the food industries, air cooling industries etc.., due to its advantage of structural compact and high heat transfer coefficient. Many existing researches have been carried to improve the heat transfer efficiency and pressure drop. Mathematical model of the heat exchanger has been used to validate the performance of the heat exchanger. This paper involves in review the researches related to the optimization of helical coil tube heat exchanger. Some of the optimization methods such as Taguchi method, Genetic Algorithm (GA) and Multi-Objective Genetic Algorithm (MOGA) is used. From the analysis, Artificial Neural Network (ANN) and GA method has efficient performance in modelling and optimization of heat exchanger. Although, some methods involved in economic optimization of heat exchanger and these method has lower performance.

Heat exchangers has been widely used in power plants and industries for heating or cooling applications. Heat is transferred from one medium to another medium by using heat exchangers. Helical coil heat exchangers with two different shell configurations are designed. First shell configuration with a central core and second without a central core. Both the configurations has a copper helical coil. Designing of heat exchangers is done with counter flow arrangement by using CATIA V5 R2015. The performance of both the configurations are analysed and compared by using Fluid flow (Fluent) in ANSYS WORKBENCH 18.1 for CFD simulations. Further the helical tube materials Copper and Aluminium which are widely used in heat exchangers are also analysed in shell with core configuration and heat transfer rates are also compared using CFD (Fluent) analysis.

Heat transfer characteristics of a tube in tube helical heat exchanger in the laminar flow regime is analysed numerically. Numerical scheme is validated with the experimental results reported in literature. The effect of helix angle on the overall heat transfer coefficient is analysed. The overall heat transfer coefficient increases with Dean number and its rate of increase at higher Dean number is low. The rate of heat transfer is maximum at a helix angle of 27°. Simulation studies show that the secondary flows that originate in a coiled tube due to curvature and torsion produce an additional transport of the fluid over the cross section of the pipe. The overall heat transfer coefficient increases with increase in inner diameter.

Estimation of local heat flux is challenging in a helical coil tube heat exchanger due to the complex flow field developed by tube curvature. The heat flux has uneven distribution in the angular direction of the tube cross-section. The current research aims to estimate the local heat flux at the fluid-solid interface for the turbulent flow of water in a helical coil tube by solving the inverse heat conduction problem (IHCP). Conjugate gradient method (CGM) with an adjoint problem is used as an inverse algorithm. First, the commercial CFD software ANSYS FLUENT is used for solving the governing equations of continuity, momentum, and energy for turbulent flow to obtain the heat flux at the fluid-solid interface. This heat flux is used to determine the temperature distribution at the outer surface of the tube. The heat flux is then considered unknown and it is estimated by CGM algorithm with the developed in-house code in MATLAB. The result shows that the estimation of heat flux by CGM is very accurate.

Different from the classical coaxial coils, a new type of asynchronous linear motor with helical 3-phase helical coil been brought forward in this paper. It has simple structures and produces peculiar travelling magnetic waves along the axis, which lead to the metal projectile is subjected invariable axial driving forces and rotary torques at the same time. It has a very useful property of this kind of winding, which is applied as a linear asynchronous launcher’s primary section. The high speed rotating projectile has stable flying attitude in moving direction because of the gyroscopic effect. The basic electromagnetic problems of the motor were discussed in this paper. An experimental model was build and tested to verify the principle results mentioned above at last.

The formulae for calculating the magnetic field produced by the finite size helical coil with rectangular cross section [J. Todoroki: Kakuyugo Kenkyu 57 (1987) 318] are extended to the case with an arbitrary polygonal cross section. The formulae for the calculation of the vector potential are also presented.

Uniformity of magnetic fields are of great importance especially in magnetic resonance studies, namely in magnetic resonance spectroscopy applications (NMR, FMR, ESR, EPR etc.) and magnetic resonance imaging applications (MRI, FMRI). Field uniformity is also required in some other applications such as eddy current probes, magnetometers, magnetic traps, particle counters etc. Here we proposed a coil winding regime, which follows the surface of a spheroid (an ellipsoid of rotation); in light of previous theoretical studies suggesting perfect uniformity for a constant ampere per turn in the axial direction thereof. We demonstrated our theoretical results from finite element calculations suggesting 0.15% of field uniformity for the proposed structure, which we called a Spheroidal Helical Coil.

The large helical device (LHD) type fusion power reactor has many advantages in operations such as steady state and no active plasma current. The magnet system of the LHD-type fusion device consists of superconducting helical coils and superconducting poloidal coils. Since the helical coil is a complicated three-dimensional structure, designs of the coil and the supporting structure have to be performed carefully. Clarifying the mechanical behavior during coil excitation is very important for a design of the coil system. The mechanical behavior for components in the helical coil can be estimated using a simplified two dimensional axisymmetric model which has a mean radius of curvature of the actual helical coil. To evaluate the accuracy of this simplified model, stress distribution was calculated with three-dimensional finite element model and the result was compared with that of the simplified model. The stress distribution of a candidate design of LHD-type helical reactor was estimated by using the simplified model and the result showed that the stress / strain level were within the reasonable range for composed materials.

This paper deals with a determination of the effective resistance and inductance of a helical coil of great length, composed of thin wire, wound on a cylinder whose radius is large in comparison with that of the wire. The pitch of the winding is not small, so that the problem cannot be treated by the method of Cohen. The method employed depends upon the use of a type of "helical coordinates" defining the position of any point, and of the general theorem relating to orthogonal systems of coordinates. A solution is obtained for the internal and external forces, corresponding to a given impressed electro-motive force, in the form of a Fourier series of which only the initial terms require calculation. The value of the effective current across any section is obtained, and thence the inductance and resistance. The results are of simple character, and are expressed in general in terms of the ber and bei functions of Lord Kelvin, whose results for a straight wire appear as a limiting case. Certain particular cases are worked out in detail and formulae obtained in terms of elementary functions which are suitable for a very high or a low frequency. Their necessary limitations are also examined numerically. For a high frequency, it is found that the change of self-inductance due to twisting of the wire tends to vanish, and that the change of resistance tends towards a value independent of the frequency.

The present paper deals with the assessment of the original and a modified version of RELAP5/MOD3.3 against the OSU Multi Application Small Light Water Reactor (OSU-MASLWR). The new implemented features regard suitable correlations for the heat transfer coefficient evaluation in helical geometry. Furthermore, two different modelling of the Helical Coil Steam Generator (HCSG) are assessed. In the first approach, HCSG’s primary and secondary sides are collapsed in a single pipe component. In the second model, three equivalent pipes are conceived for the simulation of the three ranks composing the HCSG. Two different power manoeuvring experiments are reproduced. The simulations highlight a satisfactory agreement in both the transients. Nevertheless, the modified code shows enhanced capabilities in the prediction of the HCSG operation. This is due to the improvements adopted in the modified version of RELAP5/MOD3.3 that allows a better modelling of the dryout phenomena occurring within helical tubes, as well as a better estimation of the primary side heat transfer coefficient. The better agreement of the heat exchange is propagated to the primary system, resulting in a more accurate prediction of the inlet and outlet core temperatures, and primary flow rate.

By directing the laser-driven electromagnetic pulses along a helical path, one can achieve a travelling-field accelerator arrangement for simultaneous beam shaping and re-acceleration of laser-accelerated protons. The dynamics of guided acceleration of the transiting protons was studied by varying the length of the helical coil. Experimental data shows that the protons co-moving with the field region exhibit stronger focussing while increasing the coil length, with an increase of kinetic energy due to simultaneous post-acceleration. The net energy gain for a coil of constant pitch however saturates eventually when the post-accelerated protons overtakes the accelerating field region in due course. 3D particle tracing simulation underpins the dynamics of beam transport inside the coil, which highlights the requirement for a variable pitch coil geometry in order to sustain the post-acceleration over an extended coil.