The electrodynamic and hydrodynamic phenomena in magnetically-levitated molten droplets—II. Transient behavior and heat transfer considerations

Zong, Jin; Li, Benqiang; Szekely, J.

doi:10.1016/0094-5765(93)90143-k

Cited by 29 publications

(25 citation statements)

References 4 publications

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“…and the existence and nature of the stagnation line reveal In the current work, the distribution of the electromagnetic the nature of the flow in the droplet. force is calculated by the method of mutual inducModeling the electromagnetic forces and flows requires tances [1,5,7,10] and depends on the current, frequency, and accurate values for thermophysical properties. In this study, geometry of the levitation coils and the size and electrical the density data reported by Damaschke and Samwer, [23,24] conductivity of the sample.…”

Section: Calculating Electromagnetic Force and Fluid Flowmentioning

confidence: 99%

“…It can lence. Other researchers [7][8][9][10][11][12][13][14][15][16][17] used combinations of numeribe used to produce ultrapure materials, study nucleation cal and analytical models and various turbulence models to and growth kinetics, and produce materials with metastable examine the flow phenomena in EML droplets. microstructures and novel properties.…”

Section: Introductionmentioning

confidence: 99%

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Laminar-turbulent transition in an electromagnetically levitated droplet

Hyers

Trápaga

Abedian

2003

Metall Mater Trans B

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During experiments on the MSL-1 (first microgravity science laboratory) mission of the space shuttle (STS-83 and STS-94, April and July 1997), a droplet of palladium-silicon alloy was electromagnetically levitated for viscosity measurements. For the nondeforming droplet, the resultant magnetohydrodynamic (MHD) flow inside the drop can be inferred from motion of impurity particulates on the surface. In the experiments, subsequent to melting, Joule heating produces a continuous reduction of viscosity of the fluid resulting in an acceleration of the flow with time. These observations indicate formation of a pair of co-rotating toroidal flow structures inside the spheroidal drop that undergo flow instabilities. As the fluid temperature rises, the amplitude of the secondary flow increases, and beyond a point, the tracers exhibit noncoherent chaotic motion signifying emergence of turbulence inside the drop. Assuming that the observed laminar-turbulent transition is shear-layer type, the internal structure of the toroidal loops is used to develop a semiempirical correlation for the onset of turbulence. Our calculations indicate that the suggested correlation is in modest agreement with the experimental data, with the transition occurring at a Reynolds number of 600.

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Section: Calculating Electromagnetic Force and Fluid Flowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laminar-turbulent transition in an electromagnetically levitated droplet

Hyers

Trápaga

Abedian

2003

Metall Mater Trans B

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confidence: 99%

“…Induction heating of the levitated specimen can be discussed by analytical 11,12 and numerical methods including the induced force and fluid-flow fields. 13 The rate of Joule heat generated by the heater field is given aswith R(T), (T), and I H corresponding to radius, resistivity, and heater oscillating circuit current, respectively. The geometry factor L describes the relative position of heating coils and specimen.…”

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confidence: 99%

Noncontact modulation calorimetry of metallic liquids in low Earth orbit

et al. 1997

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Noncontact modulation calorimetry using electromagnetic heating and radiative heat loss under ultrahighvacuum conditions has been applied to levitated solid, liquid, and metastable liquid samples. This experiment requires a reduced gravity environment over an extended period of time and allows the measurement of several thermophysical properties, such as the enthalpy of fusion and crystallization, specific heat, total hemispherical emissivity, and effective thermal conductivity with high precision as a function of temperature. From the results on eutectic glass forming Zr-based alloys thermodynamic functions are obtained which describe the glass-forming ability of these alloys. ͓S0163-1829͑97͒02302-3͔Precision measurements of the specific heat of stable and undercooled melts are of fundamental interest regarding the ultimate thermodynamic stability of undercooled melts and nonequilibrium crystals against vitrification and amorphization, 1 formation of associate structures in the melt, 2 the thermodynamic contribution to nucleation kinetics, 3 and thus the glass-forming ability of a material. In particular, Zr-based alloys have attracted considerable attention due to their glass-forming ability on rapid cooling, 4 solid-state amorphization reactions, 5 and, as base alloys of the recently discovered bulk glass formers. 6,7 However, investigations of the thermophysical properties of the chemically reactive liquid metallic specimen at elevated temperatures are usually hampered using conventional techniques due to exothermic reactions with the container walls. Therefore, a containerless method has been developed which allows one to alleviate these problems. 8,9 Due to insufficient temperature and positioning control of the samples of interest in an earth laboratory under UHV conditions the experiments have been performed in the space shuttle Columbia during the recent International Microgravity Laboratory 2 ͑IML-2͒ mission using the containerless electromagnetic processing ͑TEMPUS͒ device.10 The absence of excessive heating and fluid flow associated with levitation under 1 g conditions assures quiescent sample conditions in an ultraclean environment ͑Ͻ10 Ϫ8 Torr base pressure͒ and precise modeling of the thermal balance.Here, a metallic 8 mm diameter specimen ͑as an example Zr 64 Ni 36 ͒ is heated by a 400 kHz radio frequency dipole field and positioned in the center of the heating coil by a 200 kHz quadrupole field. Temperature is measured by a high precision, Ͻ0.1 K, well calibrated two-color InAs pyrometer.The different frequency and geometry of the heating and positioning fields allows separation of the total power input into additive components from heater and positioner, P tot ϭ P H ϩ P P Pos . The specimen equilibrium temperature T 0 , is given by P tot ϭAT 0 4 with total hemispherical emissivity,A surface area and Stefan-Bolzmann constant. Induction heating of the levitated specimen can be discussed by analytical 11,12 and numerical methods including the induced force and fluid-flow fields. 13 The rate of Jou...

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“…In the present ties using the EML technique, many extensive theoretical work, the effect of the electric current ratio of the heating studies have also been carried out to provide a physical coils to the levitation coils on the equilibrium drop shape was insight into the behavior of the EML system as well as the numerically investigated using our previous mathematical practical design and operational guidelines of the model, [16] and the calculated results were compared with the apparatus. [10][11][12][13] experimental ones obtained in the microgravity environment. In Japan, the EML device in Figure 1 was recently developed and the thermophysical properties, i.e., surface tension and density of molten copper and silicon, have been mea-II.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium shape of a molten silicon drop in an electromagnetic levitator in microgravity environment

Asakuma

Sakai

Hahn

et al. 2000

Metall Mater Trans B

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For the electromagnetic levitation of a molten silicon drop in a microgravity environment, the effect of the electric current ratio of the heating coils to the levitation coils on the equilibrium drop shape was numerically investigated, using the mathematical model based on the hybrid finite element and boundary element methods. As a result, it was found that the drop shape becomes more prolate as the current ratio increases, and the calculated results were in good agreement with the experimental ones obtained in a microgravity environment using a drop tower.

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The electrodynamic and hydrodynamic phenomena in magnetically-levitated molten droplets—II. Transient behavior and heat transfer considerations

Cited by 29 publications

References 4 publications

Laminar-turbulent transition in an electromagnetically levitated droplet

Laminar-turbulent transition in an electromagnetically levitated droplet

Noncontact modulation calorimetry of metallic liquids in low Earth orbit

Equilibrium shape of a molten silicon drop in an electromagnetic levitator in microgravity environment

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