scholarly journals Attempts to Measure the Inductive Element Associated with the Natural Convection of Heat

1960 ◽  
Vol 13 (1) ◽  
pp. 84
Author(s):  
RCL Bosworth
Keyword(s):  
Natural Convection ◽  
Kinetic Energy ◽  
Electric Current ◽  
Heating Rate ◽  
Heat Input ◽  
Inductive Element ◽  
Heated Wire ◽  
The Wire ◽  
Inductive Elements

A study has been made of the variation in time of the temperature of a wire immersed in a fluid and heated by a constant electric current. For a given fluid the curve obtained by plotting the ratio of the temperature of the wire to the heat input versus the time is initially the same shape for all rates �of heat input. Divergences from the lowest heating rate set in only when the system of convection currents sets in. This occurs at earlier times after the commencement of heating the higher the heating rate. Expressions already developed are used to evaluate the resistive, capacitive, and inductive elements required to fit the observed transient curves. The values of the former two types of element are consistent with an assumed stagnant film of a thickness the order of 1 mm around the heated wire, but the value of the deduced inductive element is some 10--106 greater than that associated with the kinetic energy belonging to the system of convection currents.

Natural convection from a thin heated wire situated on the surface of a liquid

1973 ◽  
Vol 5 (6) ◽  
pp. 1035-1038
Author(s):  
O. A. Evdokimova ◽  
V. D. Zimin
Keyword(s):  
Natural Convection ◽  
Heated Wire

scholarly journals A RANS K-? SIMULATION OF 2D TURBULENT NATURAL CONVECTION IN AN ENCLOSURE WITH HEATING SOURCES

2019 ◽  
Vol 20 (1) ◽  
pp. 229-244
Author(s):  
Mehdi Ahmadi ◽  
Seyed Ali Agha Mirjalily ◽  
Seyed Amir Abbas Oloomi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Kinetic Energy ◽  
Aspect Ratio ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Turbulent Natural Convection ◽  
Cold Source ◽  
Thermal Sources

ABSTRACT: This study is conducted to investigate turbulent natural convection flow in an enclosure with thermal sources using the low-Reynolds number (LRN) k-? model. This enclosure has a cold source with temperature Tc and a hot source with temperature Th as thermal sources, other walls of the enclosure are adiabatic. The aim of this study is to predict the effect of change in Rayleigh number, repositioning of cold and hot sources, and thermal sources aspect ratio on the flow field, temperature, and rate of heat transfer. To achieve this aim, the equations of continuity, momentum, energy, turbulent kinetic energy, and kinetic energy dissipation are employed in the case of 2D turbulence with constant thermo-physical properties except the density in the buoyancy term (Boussinesq approximation). To numerically solve these equations, the finite volume method and SIMPLE algorithm are used. According to the modeling results, the most optimal temperature distribution in the enclosure is seen when the hot source is below the cold source. With decreasing distance between hot and cold sources, heat transfer rate increases. The maximal heat transfer rate is derived via study of the heating sources aspect ratio. In constant positions of cold and hot sources on a wall, the heat transfer rate increases with increasing Rayleigh number (Ra=109-1011). ABSTAK: Kajian ini dijalankan bagi mengkaji perubahan semula jadi aliran perolakan dalam tempat tertutup dengan sumber haba menggunakan model k-? nombor Reynolds-rendah (LRN). Bekas tertutup ini mempunyai dua sumber haba iaitu sumber sejuk dengan suhu Tc dan sumber panas dengan suhu Th, manakala dinding lain bekas ini adalah adiabatik. Tujuan kajian ini adalah bagi mengesan perubahan nombor Rayleigh, mengubah sumber sejuk dan panas dan nisbah sumber haba kepada kawasan aliran, suhu dan halaju perubahan haba. Bagi mencapai tujuan tersebut, persamaan sambungan, momentum, tenaga, tenaga kinetik perolakan, dan pengurangan tenaga kinetik telah dilaksanakan dalam kes perolakan 2D dengan sifat fizikal-haba berterusan (malar) kecuali isipadu terma keapungan (anggaran Boussinesq). Bagi menyelesaikan persamaan ini secara berangka, kaedah isipadu terhad dan algorithma MUDAH telah digunakan. Berdasarkan keputusan model, suhu distribusi optimal dalam bekas tertutup dilihat apabila sumber panas adalah kurang daripada sumber sejuk. Dengan pengurangan jarak antara sumber panas dan sejuk, kadar pertukaran haba meningkat. Kadar pertukaran haba maksima telah diperoleh melalui kajian nisbah  aspek sumber pemanasan. Kadar pertukaran haba bertambah dengan bertambahnya nombor Rayleigh  (Ra=109-1011), pada posisi tetap sumber sejuk dan panas pada dinding bekas.

X.—The Variation of Young's Modulus under an Electric Current

1912 ◽  
Vol 31 ◽  
pp. 186-250
Author(s):  
Henry Walker
Keyword(s):  
Electric Current ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Iron Copper ◽  
Small Load ◽  
The Subject ◽  
The Wire

The results of the investigations on four metals, viz. steel, iron, copper, and platinum, form the subject of my two first papers. In Parts I. and II. the effects on the modulus when the wire was stretched with a small load, and also with a much greater load, were examined. In this, my third paper, the investigation of these metals has been extended in several directions. The scope of the whole work has also been widened by subjecting nickel and cobalt to examination.As the question of temperature still seemed doubtful, and as the justification given near the beginning of the second paper might not be altogether convincing, I thought it better to put the matter beyond all question. I therefore adopted the following method. Using the doublewalled tube already described, the wires were passed through it and over the wheel in the same way as in the main experiments.

scholarly journals Irreversible thermodynamics of transport across interfaces

2011 ◽  
Vol 89 (10) ◽  
pp. 1041-1050 ◽  
Author(s):  
Matthew R. Sears ◽  
Wayne M. Saslow
Keyword(s):  
Entropy Production ◽  
Electric Current ◽  
Heating Rate ◽  
Chemical Potential ◽  
Magnetic Semiconductors ◽  
Spin Current ◽  
Irreversible Thermodynamics ◽  
Heat Current ◽  
Bulk Heating ◽  
Current Production

With spintronics applications in mind, we use irreversible thermodynamics to derive the rates of entropy production and heating near an interface when heat current, electric current, and spin current cross it. Associated with these currents are apparent discontinuities in temperature (ΔT), electrochemical potential (Δ[Formula: see text]), and spin-dependent “magnetoelectrochemical potential” (Δ[Formula: see text]). This work applies to magnetic semiconductors and insulators as well as metals, because of the inclusion of the chemical potential, μ, which is usually neglected in works on interfacial thermodynamic transport. We also discuss the (nonobvious) distinction between entropy production and heat production. Heat current and electric current are conserved, but spin current is not, so it necessitates a somewhat different treatment. At low temperatures or for large differences in material properties, the surface heating rate dominates the bulk heating rate near the surface. We also consider the case where bulk spin currents occur in equilibrium. Although a surface spin current (in A/m2) should yield about the same rate of heating as an equal surface electric current, production of such a spin current requires a relatively large “magnetization potential” difference across the interface.

Wire-Electric Gyroscope

2013 ◽  
Author(s):  
Vadym Avrutov
Keyword(s):  
Electric Current ◽  
Low Cost ◽  
Angular Rate ◽  
Good Choice ◽  
Angular Rate Sensor ◽  
Cross Section Area ◽  
Section Area ◽  
New Type ◽  
The Wire ◽  
Rate Sensor

The wire-electric gyroscope (WEG) is a new type of the angular rate sensor. The basic principle of the WEG is based on the hypothesis of invariance of the electric current speed for the same wire (coil). It is similar to the Sagnac effect for the speed of light. The method of angular rate determination is described. The voltage difference between two wire coils with different line coupling can be expressed in applied rotation (angular) rate and velocity of electric current. The scale factor depends on the magnitude of the current, number of the coil turns, the coil’s radius, the cross-section area of the wire and specific (unit) resistance of the wire. WEG can be produced cost-effectively and can be a good choice for low-cost applications.

Numerical Calculation of Three-Dimensional Turbulent Natural Convection in a Cubical Enclosure Using a Two-Equation Model for Turbulence

1986 ◽  
Vol 108 (4) ◽  
pp. 806-813 ◽  
Author(s):  
H. Ozoe ◽  
A. Mouri ◽  
M. Hiramitsu ◽  
S. W. Churchill ◽  
N. Lior
Keyword(s):  
Natural Convection ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Spiral Flow ◽  
Vertical Side ◽  
Turbulent Natural Convection ◽  
Cubical Enclosure ◽  
Side Walls

This paper presents a model and numerical results for turbulent natural convection in a cubical enclosure heated from below, cooled on a portion of one vertical side wall and insulated on all other surfaces. Three-dimensional balances were derived for material, energy, and the three components of momentum, as well as for the turbulent kinetic energy k and the rate of dissipation of turbulent kinetic energy ε. The constants used in the model were the same as those used by Fraikin et al. for two-dimensional convection in a channel. Illustrative transient calculations were carried out for Ra = 106 and 107 and Pr = 0.7. Both the dominant component of the vector potential and the Nusselt number were found to converge to a steady state. Isothermal lines and velocity vectors for vertical cross sections normal to the cooled wall indicated three-dimensional effects near the side walls. A top view of the velocity vectors revealed a downward spiral flow near the side walls along the cooled vertical wall. A weak spiral flow was also found along the side walls near the wall opposing the partially cooled one. The highest values of the eddy diffusivity were 2.6 and 5.8 times the molecular kinematic viscosity for Ra = 106 and 107, respectively. A coaxial double spiral movement, similar to that previously reported for laminar natural convection, was found for the time-averaged flow field. This computing scheme is expected to be applicable to other thermal boundary conditions.

Experimentelle Untersuchungen an Drahtexplosionsentladungen im Hochvakuum / Experimental Investigation of Exploding Wire Discharges in High Vacuum

1969 ◽  
Vol 24 (11) ◽  
pp. 1707-1715 ◽  
Author(s):  
Lutz Niemeyer
Keyword(s):  
Axial Magnetic Field ◽  
High Vacuum ◽  
Thermionic Emission ◽  
Plasma Temperature ◽  
Radial Electric Field ◽  
Discharge Column ◽  
Contraction Phase ◽  
Heated Wire ◽  
The Mean ◽  
The Wire

Explosions of 0.03 -0.25 mm diameter wires of Cd, AI, Cu, and W in high vacuum (p < 10-5 Torr) are investigated. The time development of the discharge column is shown to be determined by two main processes: a) In the time preceding the explosion, particles are emitted from the surface of the heated wire and initiate a peripheral discharge. The mechanism of particle emission is found to be evaporation of neutral atoms and/or thermionic emission of charged particles. The latter process is influenced by the strong radial electric field which is caused by the coaxial discharge geometry at the wire surface, b) The wire material vaporizes explosively forming an expanding cloud of nonconducting vapor which is subsequently converted to a plasma by the peripheral discharge penetrating into it from outside. The discharge column exhibits instabilities which are shown to be of MHD origin. They are significantly reduced by applying an axial magnetic field to the discharge column. A quantitative spectroscopic investigation is performed during the magnetic contraction phase of stabilized 0.05 mm Al wire explosions. The plasma temperature is found to be about 50 000 °K in the axis of the column and higher than 80 000 °K at its periphery. The mean electron density is estimated to be of the order of some 1019 cm-3 .

Formation of Al2O3 grains with different sizes and morphologies during the pulse electric current sintering process

2001 ◽  
Vol 16 (12) ◽  
pp. 3514-3517 ◽  
Author(s):  
S. W. Wang ◽  
L. D. Chen ◽  
T. Hirai ◽  
Jingkun Guo
Keyword(s):  
Electric Current ◽  
Heating Rate ◽  
Cross Sections ◽  
Mechanical Pressure ◽  
Pulse Electric Current ◽  
Side Edge ◽  
Microstructure Observation ◽  
Different Temperatures ◽  
Powder Compacts ◽  
Pulse Electric

Commercial micrometer Al2O3 powder was sintered at 1550 °C under a mechanical pressure of 30 MPa by pulse electric current sintering (PECS). Microstructure observation was performed on polished, thermal-etched cross sections parallel to the direction of mechanical pressure. Platelike Al2O3 grains formed when the powder was heated at a heating rate of 5 °C/min, while a heating rate of 200 °C/min resulted in equiaxed grains. These results indicated that PECS is an effective approach to hinder grain growth by application of a higher heating rate. However, Al2O3 grains at the upper edge were larger than those at the side edge of the samples in both cases. It implied that there were different temperatures at the upper edge and the side edge of the Al2O3 powder compacts during the PECS process.

scholarly journals Electromotive Force Generated in All Materials under Temperature Difference

2021 ◽  
Author(s):  
Dong-il Song
Keyword(s):  
Magnetic Field ◽  
Kinetic Energy ◽  
Electric Current ◽  
Temperature Difference ◽  
Electromotive Force ◽  
Thermoelectric Effect ◽  
Radio Waves ◽  
Temperature Differential ◽  
Electric Resistance ◽  
Thermoelectric Effects

Abstract In this research, we investigate the thermoelectric effects of general materials. The results of this showed that an electromotive force was generated under a temperature difference between two points in materials. As no material has infinite electric resistance, an electromotive force is expected to be generated under a temperature difference in all materials. In conclusion, the thermoelectric effect generates an electromotive force. This electromotive force causes an electric current to flow, thereby generating a magnetic field.This magnetic field generates the Earth's magnetic field, triboelectricity, sunspots, and kinetic energy of celestial bodies.This temperature differential electromotive force also generates lightning and creates an ionosphere that reflects radio waves.

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