Tube In Magnetic Field Research Articles

Magnetic Field Impact on Heat Transfer and Nano-Ferrofluid Flow in a Pipe

The research examines velocity, Nusselt number, Y plus, magnetism effectiveness, and flow of Fe3O4-distilled water in a magnetic field tube in order to investigate heat transfer and flow. Magnetic fields modify flow patterns by generating vortexes and changing thermal boundary layers. The surface of a model with a 210 mm tube length and a 25.4 mm inner diameter exhibits equal magnet shed spots. The entry of the nanomaterial at a temperature of 300 K is shown by the three different entrance velocities of 0.05, 0.1, and 0.5 m/s that were recorded at the entry region. These limitations were used. Three instances of the first magnets were taken when the middle magnet was switched on, followed by the first and third, and finally all three of them. In the exit region, an exit pressure of 0 pa was given to the surfaces of heat at a constant temperature of 350 K. Three magnetic flux forces one, two, and three Tesla were measured. The temperature value at the three magnets is 349 K, which is the biggest temperature value compared to the other examples, demonstrating that the temperature value rises with the number of magnetization stages.

Anisotropic electron heating in an electron cyclotron resonance thruster with magnetic nozzle

In a grid-less electron cyclotron resonance plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends on the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror force and the electrostatic potential of the thruster. An electromagnetic particle-in-cell code is used to simulate the plasma in a magnetic field tube. The code's Maxwell solver is based on a semi-Lagrangian scheme known as the constrained interpolation profile which enables larger time steps. The results show that anisotropic plasma heating takes place exclusively inside the coaxial chamber, along a Doppler-broadened zone. It is also shown that a trapped population of electrons with a larger perpendicular energy exists in the plume.

Coronal Field Geometry and Solar Wind Speed

The Wang–Sheeley–Arge (WSA) solar wind (SW) model is based on the idea that weakly expanding coronal magnetic field tubes are associated with sources of fast SWs and vice versa. A parameter called the “flux tube expansion” (FTE) is used to determine the degree of expansion of magnetic tubes. The FTE is calculated based on the coronal magnetic field model, usually in the potential approximation. The second input parameter for the WSA model is the great circle distance from the base of the open magnetic field line in the photosphere to the boundary of the corresponding coronal hole (DCHB). These two coronal magnetic field parameters are related by an empirical relationship with the solar wind velocity near the Sun. The WSA model has shortcomings and does not fully explain the solar wind formation mechanisms. In the present work, we model various coronal magnetic field parameters in the potential-field source-surface (PFSS) approximation from a long series of magnetographic observations: the Solar Telescope-magnetograph for Operative Prognoses (STOP) (Kislovodsk Mountain Astronomical Station), the Helioseismic and magnetic imager (SDO/HMI), and data from the Wilcox Solar Observatory (WSO). Our main goal is to identify correlations between the coronal magnetic field parameters and the observed SW velocity in order to use them for modeling SW. We found that the SW velocity correlates relatively well with some geometric properties of the magnetic tubes, including the force line length, the latitude of the force line footpoints, and the DCHB. We propose a formula for calculating the SW velocity based on these parameters. The presented relationship does not use FTE and showed a better correlation with observations compared to the WSA model.

The Response of a Plasma Magnetospheric Maser to Atmospheric Perturbations

The effect of weak external influences associated with infrasonic waves in the ionosphere on the operation of a plasma magnetospheric maser (PMM) is considered. It is shown that if the frequency of infrasonic waves is close to the eigen frequency oscillations of the PMM, then quasi-periodic (QP) electromagnetic VLF emissions with repetition periods of spectral forms of 10–300 s can be excited in radiation belts. It has been found that one of the possible reasons for this phenomenon may be the Q-switching of the magnetospheric resonator due to a change in the coefficient of reflection of whistler waves from the ionosphere from above by atmospheric infrasonic waves. For natural atmospheric sources of infrasonic disturbances with horizontal scales of approximately 100 km, model calculations of the depth of modulation of the energy density of electromagnetic waves in a magnetic field tube were carried out. It has been found that in the morning and daytime subauroral magnetosphere, even weak external influences lead to the appearance of signals with a sufficiently large modulation depth (tens of percent).

Experimental investigation on thermo hydraulic performance of ferronanofluid flow in a dimpled tube under magnetic field effect

ABSTRACT Active and passive techniques have been utilized together to enhance heat transfer in this study. The ferronanofluid, magnetic field, and dimpled tube have not been utilized together in the literature so far. Regarding this issue, this investigation is the first experimental study to specify the effect of use of these three effects simultaneously. The concept of this study is to determine the thermo-hydraulic performance of Fe3O4/H2O flow inside a dimpled tube under magnetic field effect. Constant and uniform heat flux of 4500 W/m2 has been applied on the surface of the tube. The work aims to gain data in the range of laminar flow (1131≤ Re≤2102) in the dimpled tube. Dimple geometry with pitch ratio of P/d = 3.75, magnetic field (B = 0.03 ≤ T ≤ 0.16), and nanoparticle volume fraction of 1.0% are the base variables. The results showed that Nusselt number increases with increasing Reynolds number and magnetic field intensity. The highest increase in Nusselt number is obtained as 115.31% compared with the distilled water flow in the smooth tube for the case of magnetic field intensity of 0.3 T. The highest Performance Evaluation Criteria value is also determined as 1.44 for the case of ferronanofluid flow in dimpled tube at Re = 1131 in absence of magnetic field.

Improving the performance of air conditioning unit by using a hybrid technique

An Air Conditioning Unit with magnetic field and different tubes was designed, fabricated and evaluated in this study. The Effect of magnetic field and different types of tubes on the performance of Air Conditioning was studied experimentally. A testing system of Air Conditioning Unit was developed as the test rig. The modified tubes as a straight tube before the condenser and after the evaporator were replaced by a finned bended tube with five bends and a coil finned tube with five turns. The experimental results for the temperature of refrigerant and the coefficient of performance for an air conditioning unit were presented. Changing the tubes and introducing electric charging has a significant effect on the performance of the unit. The electric charging has a positive effect of the performance of the system. The electric charging enhanced the performance by 76% in case of bent tube and by 177% in case of coil tube. The bent pipe increases the refrigerant temperature between 50% and 200%, while the coil pipe increases the temperature between 18 % and 190 %.• This method increases the refrigerant temperature for Air Conditioning system.• This method provides simple technical testing of Air Conditioning Unit with magnetic field and different tubes• This method can be useful to enhance the performance of Air Conditioning Unit.

Controlling the type and intensity of low-frequency waves generated by laser plasma clots in a force tube of magnetized plasma

In this work, we study the influence of the parameters of a magnetized background plasma on the intensity of whistler waves generated by periodic laser plasma bunches in a magnetic field tube. It is shown that at 0.3 < Lpi > 0.4 Alfvén waves and whistlers are generated. In the region Lpi> 0.5, intense whistlers with an amplitude of δBmax / B0 ∼ 0.24 are generated.

Self-driven liquid metal cooling connector for direct current high power charging to electric vehicle

Direct current-based high power charging (DC-HPC) technology is expected to shorten the charging time of electric vehicles (EV) significantly and lessen the range anxiety. However, a high charging current would cause a remarkable temperature rise of the charging connector due to the Joule heat, which must be adequately removed to keep its durability and safety. This paper reported a novel concept of the self-driven liquid metal (LM) cooling connector (LMCC) used for DC-HPC. The room-temperature LM of Galinstan filled in the flexible tube is applied as the current-carrying conductor and circulated-cooling fluid simultaneously. The circulation-flow LM is driven by the designed electromagnetic force through coupling the charging current and magnetic field from a pair of permanent magnets, which does not need additional pumping devices. A principle experiment is conducted to demonstrate the driving and cooling performances of LMCC, which shows excellent circulation flow rate (with the flow rate of 0.75 L/min and the driven pressure head of 44.7 kPa) of the LM in the flexible tube (diameter of 6 mm and length of 2.65 m) and only achieves a temperature rise of about 13 °[email protected] Both 3D multi-physics simulation and theoretical models are also established and demonstrated by experiment results to accurately evaluate the impacts of the charging current, magnetic field, and flexible tube size on the performance of self-driven LMCC. The results indicate that increasing the diameter of the flexible tube could significantly reduce its temperature rise induced by a high charging current and does not affect its flexibility. A super-low temperature rise of 10.6 °[email protected] for the charging cable (the diameter of 10 mm and length of 3 m) is designed. This work provides a new strategy for the heat dissipation technology of DC-HPC charging connectors.

Hybridization of rotary absorber tube and magnetic field inducer with nanofluid for performance enhancement of parabolic trough solar collector

A considerable amount of energy is lost in the parabolic trough solar collectors due to the poor capability of working fluid in full absorption of the concentrated solar irradiation across the receiver tube. A new hybrid method is recommended here to cover up such deficiency by simultaneously using a rotary absorber tube and magnetic field inducer with nanofluid. Results showed that the combination effects of the receiver rotation and the magnetic field improve the convection mechanism in the absorber and increase both energetic and exergetic performance of the collector. The study reveals that there is an optimal rotational speed in the each magnetic field intensity for different hydrothermal and thermodynamic parameters. That is, in comparison with the case with no magnetic field and rotational tube employment, the total heat loss in the collector can be saved by 37.4% when a magnetic field of 1000 G and a rotary tube with speed of 0.4 rad/s are employed simultaneously. In this comparison, a maximum improvement of 101% and 24% in the performance evaluation criteria (PEC) and exergy efficiency of the system is achieved by employing the proposed hybrid method, respectively. Results also revealed that there is an optimal rotational speed in the each magnetic field intensity, in which employing a magnetic field at this rotational speed does not increase pressure drop for the sake of improving energetic and exergetic efficiencies of the solar collector.

Characteristics of fast timing MCP-PMTs in magnetic fields

The motivation of this paper is to explore the parameters that affect the performance of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) in magnetic fields with the goal to guide their design to achieve a high magnetic field tolerance. MCP-PMTs based on two different designs were tested.The magnetic field tolerance of MCP-PMT based on a design providing independently biased voltages showed a significant improvement (up to 0.7 T) compared to the one utilizing an internal resistor chain design (up to 0.1 T), indicating the importance of individually adjustable voltages. The effects of the rotation angle of the MCP-PMT relative to the magnetic field direction and of the bias voltage between the photocathode and the top MCP were extensively investigated using the MCP-PMT based on the independently biased voltage design. It was found that the signal amplitude of the MCP-PMT exhibits an enhanced performance at a tilt angle of $\pm$8$^{\circ}$, due to the 8$^{\circ}$ bias angle of the MCP pores. The maximum signal amplitude was observed at different bias voltages depending on the magnetic field strength.

Generation of torsional Alfvén and slow magnetosonic waves by periodic bunches of laser plasma in a magnetised background**This and subsequent papers were presented at the VIII International Symposium on Modern Problems of Laser Physics (Novosibirsk, 25 August to 1 September 2018).

Using numerical simulation, the influence of parameters of a magnetised background plasma on the intensity of quasi-stationary Alfvén and slow magnetosonic waves produced by periodic bunches of a laser plasma in a magnetic field tube is investigated. It is shown that in a weak magnetic field, the waves propagate together, carrying a flow of rotating plasma, and in a strong field, the bunches form simultaneously two types of waves propagating with different velocities.

Energetics of the Kelvin-Helmholtz instability induced by transverse waves in twisted coronal loops

Aims: We quantify the effects of twisted magnetic fields on the development of the magnetic Kelvin-Helmholtz instability (KHI) in transversely oscillating coronal loops. Methods: We modelled a fundamental standing kink mode in a straight, density-enhanced magnetic flux tube using the magnetohydrodynamics code, Lare3d. In order to evaluate the impact of an azimuthal component of the magnetic field, various degrees of twist were included within the flux tube's magnetic field. Results: The process of resonant absorption is only weakly affected by the presence of a twisted magnetic field. However, the subsequent evolution of the KHI is sensitive to the strength of the azimuthal component of the field. Increased twist values inhibit the deformation of the loop's density profile, which is associated with the growth of the instability. Despite this, much smaller scales in the magnetic field are generated when there is a non-zero azimuthal component present. Hence, the instability is more energetic in cases with (even weakly) twisted fields. Field aligned flows at the loop apex are established in a twisted regime once the instability has formed. Conclusions: The KHI may have implications for wave heating in the solar atmosphere due to the creation of small length scales and the generation of a turbulent regime. Whilst magnetic twist does suppress the development of the vortices associated with the instability, the formation of the KHI in a twisted regime will be accompanied by greater Ohmic dissipation due to the larger currents that are produced, even if only weak twist is present. The presence of magnetic twist will likely make the instability more difficult to detect in the corona, but will enhance its contribution to heating the solar atmosphere.

Merging of the waves produced by optical breakdowns in rarefied plasma with a magnetic field. Laboratory modelling

In laboratory experiments using laser plasma, the criteria are confirmed in which periodic plasma bunches form simultaneously two types of quasi-stationary waves: torsional Alfven and slow magnetosonic waves propagating along the magnetic field tube.

Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips

Abstract Large-amplitude longitudinal oscillations of solar filaments have been observed and explored for more than ten years. Previous studies are mainly based on the one-dimensional rigid flux tube model with a single magnetic dip. However, it has been noted that there might be two magnetic dips, and hence two threads, along one magnetic field line. Following previous work, we intend to investigate the kinematics of the filament longitudinal oscillations when two threads are magnetically connected, which is done by solving one-dimensional radiative hydrodynamic equations with the numerical code MPI-AMRVAC. Two different types of perturbations are considered, and the difference from previous works resulting from the interaction of the two filament threads is investigated. We find that even with the inclusion of the thread–thread interaction, the oscillation period is modified weakly, by at most 20% compared to the traditional pendulum model with one thread. However, the damping timescale is significantly affected by the thread–thread interaction. Hence, we should take it into account when applying the consistent seismology to the filaments where two threads are magnetically connected.

Optoelectronic properties of silicon hexagonal nanotubes under an axial magnetic field

In this work, we derive a clear and easy-to-use analytic expression for optical transition matrix elements for the zigzag silicon hexagonal nanotubes (Si h-NTs) in the presence of axial magnetic field. The optical dipole matrix elements and optical absorption are analytically derived in terms of one-dimensional wave vector, kz and subband index l for a light polarization parallel to the tube axis. The model is based on a single-orbital π-electron tight-binding Hamiltonian extended up to the first nearest-neighbors. By comparing the band structure of tubes in different magnetic fields, one can see that the band gap is modified and the degenerated bands are split and create new allowed transition corresponding to the band modifications. Moreover, it is found that the system is metallic in the absence of magnetic field, but with increasing the magnetic flux the system tends towards the semiconducting behavior and the metal–semiconductor phase transition is observed.

Studies of relative gain and timing response of fine-mesh photomultiplier tubes in high magnetic fields

We investigated the use of Hamamatsu fine-mesh photomultiplier tube assemblies H6152-70 and H6614-70 with regard to their gain and timing resolution in magnetic fields up to 1.9T. Our results show that the H6614-70 assembly can operate reliably in magnetic fields exceeding 1.5T, while preserving a reasonable timing resolution even with a gain reduction of a factor of ≈100. The reduction of the relative gain of the H6152-70 is similar to the H6614-70's near 1.5T, but its timing resolution worsens considerably at this high field.

Ground State Phase Diagram of Twisted Three-Leg Spin Tube in Magnetic Field

We study the ground state phase diagram of the twisted three-leg spin tube in magnetic fields by the density matrix renormalization group (DMRG) method. The twisted spin tube is composed of triangular unit cells and possesses strong quantum fluctuations under geometrical frustration. We apply the sine square deformation method to remove the strong boundary effects and obtain smooth magnetization curves without steps of finite systems. With the analysis of the magnetization curves and correlation functions we determine the ground state phase diagram consisting of (a) a Tomonaga-Luttinger (TL) liquid characterized by spin-$\frac{3}{2}$ Heisenberg model, (b) 3-sublattice state named UUD with 1/3 magnetization and (c) TL-liquid of massless chirality with 1/3 magnetization plateau, (d) TL-liquid of massless spin mode with or without chirality quasi long-range order.

Anharmonic oscillatory flow braking in the Earth's magnetotail

AbstractPlasma sheet bursty bulk flows often oscillate around their equilibrium position at about 10 RE downtail. The radial magnetic field, pressure, and flux tube volume profiles usually behave differently earthward and tailward of this position. Using data from five Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes, we reconstruct these profiles with the help of an empirical model and apply thin filament theory to show that the oscillatory flow braking can occur in an asymmetric potential. Thus, the thin filament oscillations appear to be anharmonic, with a power spectrum exhibiting peaks at both the fundamental frequency and the first harmonic. Such anharmonic oscillatory braking can explain the presence of the first harmonic in Pi2 pulsations (frequency doubling), which are simultaneously observed by magnetometers on the ground near the conjugate THEMIS footprints.

Magnetization plateaux and jumps in frustrated four-leg spin tubes in magnetic fields

We study the ground state phase diagram of a frustrated spin-1/2 four-leg tube in an external magnetic field. We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: density matrix renormalization group (DMRG), a low-energy effective Hamiltonian (LEH) and a Hartree variational approach (HVA). We find that in the limit of weakly interacting plaquettes, singlet and triplet states play an important role in the formation of magnetization plateaux. We study the transition regions numerically and analytically, and find that they are described, at first order in a strong- coupling expansion, by an XXZ spin-1/2 chain in a magnetic field. These results are consistent with the DMRG and HVA calculations.

In situ properties of small and large flux ropes in the solar wind

AbstractTwo populations of twisted magnetic field tubes, or flux ropes (hereafter, FRs), are detected by in situ measurements in the solar wind. While small FRs are crossed by the observing spacecraft within few hours, with a radius typically less than 0.1 AU, larger FRs, or magnetic clouds (hereafter, MCs), have durations of about half a day. The main aim of this study is to compare the properties of both populations of FRs observed by the Wind spacecraft at 1 AU. To do so, we use standard correlation techniques for the FR parameters, as well as histograms and more refined statistical methods. Although several properties seem at first different for small FRs and MCs, we show that they are actually governed by the same propagation physics. For example, we observe no in situ signatures of expansion for small FRs, contrary to MCs. We demonstrate that this result is in fact expected: small FRs expand similar to MCs, as a consequence of a total pressure balance with the surrounding medium, but the expansion signature is well hidden by velocity fluctuations. Next, we find that the FR radius, velocity, and magnetic field strength are all positively correlated, with correlation factors than can reach a value &gt;0.5. This result indicates a remnant trace of the FR ejection process from the corona. We also find a larger FR radius at the apex than at the legs (up to 3 times larger at the apex), for FR observed at 1 AU. Finally, assuming that the detected FRs have a large‐scale configuration in the heliosphere, we derived the mean axis shape from the probability distribution of the axis orientation. We therefore interpret the small FR and MC properties in a common framework of FRs interacting with the solar wind, and we disentangle the physics present behind their common and different features.