Showing papers on "Liquid metal published in 1999"

Apparatus and method for protecting devices, especially fibre optic devices, in hostile environments

Abstract: The present invention relates to protecting optical devices, such as an optical fibre sensor connected in series with a cable, from a hostile environment, such as encountered when making measurements in oil and gas wells. A liquid can protect the optical device. Packaging an optical fibre sensor inside a capillary containing the liquid can provide this protection. The liquid can be liquid metal, gel, inks, grease or oil. The liquid metal can be gallium or indium, or an alloy that includes indium and/or gallium. The grease can contain lithium, molybdenum, or synthetics, or be synthetic grease. The liquid can contain other components such as a scavenger or getter for molecules and/or ions.

Time-dependent rheological properties of semi-solid metal alloys

Abstract: Semi-solid metal alloys, as used in thixoforming, have a special microstructure of globular grains suspended in a liquid metal matrix. The complex rheological properties are strongly influenced by the local solid fraction, particle shape, particle size and state of agglomeration. There is a high demand for models and software tools allowing the simulation of semi-solid casting processes. The material under investigation is a tin-lead alloy (Sn-15%Pb) which exhibits a similar microstructure to aluminium alloys. The experiments were performed with a concentric cylinder rheometer of the Searle type. Initially, the liquid alloy is cooled down to the semi-solid range under constant shearing and then kept under isothermal conditions for further experimentation. Based on the experimental data, a single-phase model has been derived where the semi-solid alloy is regarded as a homogeneous material with thixotropic properties and the microstructure is characterised by a structural parameter. The model consists of two parts: the equation of state, including a finite yield stress, and a rate equation for the structural parameter. The model equations are employed in numerical software and used for the simulation of characteristic filling cases and the comparison with the conventional filling.

Thermal conductivity of liquid metals and metallic alloys

Abstract: The aim of this work is to show that the electrical resistivity and the thermoelectric power can be used to determine the thermal conductivity of liquid metals and alloys. We have made this determination for liquid aluminum, tin, lead, copper and metallic alloys Cu–Al, Ag–Ga, Ag–Ge, Cu–Pb, In–Mn, Ga–Ge and Sn–Bi. For these calculations, we used the relations between the transport coefficients that can be simplified to the Wiedemann–Franz law. For the pure metals studied, our calculated thermal conductivities are near experimental determinations from different authors, showing that the Wiedemann–Franz law is valid. We predict that the Al–Cu liquid alloy has a minimum in the thermal conductivity, and in its temperature coefficient versus concentration at 20 at.% of aluminum. This result is in agreement with the magnetic susceptibility data, and with the superficial tension that have unusual magnitudes near this concentration. It is also consistent with the existence of an eutectic near the same concentration. Nevertheless, it is in contradiction with other data also deduced from resistivity measurements. We do not have any explanation of that disagreement. We show that a minimum in the thermal conductivity isotherm is also obtained for other noble-polyvalent liquid metal alloys studied, i.e. Ag–Ga and Ag–Ge. The only exception is the Cu–Pb alloy for which the calculated thermal conductivity varies monotonically with concentration.

Structural materials for atomic reactors with liquid metal heat-transfer agents in the form of lead or lead—Bismuth alloy

Abstract: Natural safety nuclear reactors operate at a working temperature of the liquid-metal lead heat-transfer agent equal to 550°C, which intensifies the metal corrosion and is fraught with the danger of thermal embrittlement. It is shown that long-term operation of the equipment requires inhibition of the heat-transfer agent by oxygen and the use of silicon steels. However, alloying with silicon increases the susceptibility of the steel to thermal and radiative embrittlement. This makes it necessary to create new steels with a stable structure. The suggested composition of austenitic steel 04Kh15N11S3MT is designed for shell and internal structures, and steel 10Kh9NSMF is designed for the pipe system of the steam generator.

Visualization and measurement of gas–liquid metal two-phase flow with large density difference using thermal neutrons as microscopic probes

Abstract: In a core melt accident of a fast breeder reactor, there is a possibility of boiling of the fuel–steel mixture in the containment pool. In relation to safety evaluation on severe accident, it is indispensable to evaluate the possibility of re-criticality of melted core. Gas–liquid two-phase flow with a large liquid-to-gas density ratio is formed due to the boiling of fuel–steel mixture. Although it is anticipated that the large density ratio may affect the basic characteristics of two-phase flow, little work has been performed so far on two-phase flow with a large liquid-to-gas density ratio. In this study, visualization and void fraction measurement of gas–liquid metal two-phase flow were performed by using neutron radiography and image processing techniques. Then, the effect of large density difference between gas and liquid phases on the basic flow characteristics of two-phase flow was clarified.

X-ray Studies of Liquid Metal Surfaces

Abstract: X-ray reflectivity and diffuse scattering measurements of the surface of liquid Hg, Ga and In are reviewed. For each metal surface induced layering is found. The surface structure of these metals is compared and differences are discussed in relation to bulk structural features such as the degree of covalency. Studies of modified liquid metal surfaces are also presented. The surface oxidation of liquid Ga, In and Hg is compared. Experimental results on surface segregation in Ga–In and Ga–Bi alloys and details of the surface wetting transition in Ga–Bi are also discussed.

Electrical conductivity measurements in liquid metals by rotational technique

Abstract: The rotational contactless inductive measurement technique has been developed to measure the electrical conductivity of liquid metals. This method is based on the phenomena when a conductor material rotates in a magnetic field, circulating eddy currents are induced and generate a damping torque proportional to the electrical resistivity of the material. The technique was tested to measure the conductivity of five conductors and one low melting composite (LMA-158).

Installation for making cold rolled stainless steel bands

Abstract: The invention concerns a method for making thin stainless steel bands which consists in successively and continuously carrying out the following steps on a single processing line: continuously casting directly from liquid metal a stainless steel band; de-scaling said band; cold rolling said band; annealing and de-scaling or bright annealing of said band; finish forming of said band, such as final cold rolling and/or passing in a tempering rolling mill; coiling said band. The invention also concerns an installation for implementing said method.

Liquid metal turbulent flow dynamics in a cylindrical container with free surface: experiment and numerical analysis

Abstract: The liquid metal flow in induction crucible models is known to be unstable, turbulent and difficult to predict in the regime of medium frequencies when the electromagnetic skin-layer is of considerable extent. We present long term turbulent flow measurements by a permanent magnet incorporated potential difference velocity probe in a cylindrical container filled with eutectic melt In-Ga-Sn. The parallel numerical simulation of the long time scale development of the turbulent average flow is presented. The numerical flow model uses an implicit pseudo-spectral code and k-w turbulence model, which was recently developed for the transitional flow modelling. The results compare reasonably to the experiment and demonstrate the time development of the turbulent flow field and the turbulence energy.

Exact solution for the steady-state surface profile of a liquid metal in an external electric field

Abstract: An analysis is made of the equilibrium profile of the free surface of a liquid metal in an external electric field neglecting gravitational forces. It is shown that a conformal mapping method can be used to find a wide range of exact solutions corresponding to the case of planar symmetry.

Liquid metal cooled anode for an X-ray tube

Abstract: A system and method are proposed for cooling the anode of an X-ray tube. A bearing shaft associated with the anode has an associated single rotating seal there around, and contains a liquid metal. A primary liquid metal flow path is used to transfer heat from the anode, and a secondary liquid metal flow path is provided to seal the single rotating seal. Accordingly, the present invention provides an effective means for containing liquid metal in the bearing shaft of an anode assembly, and using the liquid metal to cool the anode of the X-ray tube.

Effects of variables on size and characteristics of gas atomised aluminium powders

Abstract: A gas atomisation unit was designed and constructed using free fall liquid metal delivery and a Mannesmann type nozzle. Nozzle geometry, liquid metal flowrate, gas type, and pressure were varied and the effects of these variables on powder mean size, powder morphology, and cooling rate were investigated. Powders with mean size d50 as low as 20 μm were obtained. Powders with mean size d50 greater than 20 μm had irregular shapes and cellular–dendritic structures; smaller powders had spherical shapes and smooth surfaces.

Cooled x-ray tube and method of operation

Abstract: The present invention is directed to a cooling system and apparatus for use in x-ray tubes. In operation x-ray tubes generate large amounts of heat. The disclosed device includes a liquid metal cooling system applied to the anode of the x-ray tube and a contactless magnetic bearing. The magnetic bearing suspends the anode. The anode is connected thermally through the liquid metal cooling system.

Numerical analysis of nonstationary thermal response characteristics for a fluid-structure interaction system

Abstract: Nonstationary thermal response analysis for a fundamental sodium experiment simulating thermal striping phenomena was carried out using a quasi-direct numerical thermohydraulics simulation code with a third-order upwind scheme for convection terms and a boundary element method code for thermal response evaluation of structures due to random sodium temperature fluctuations developed at Power Reactor and Nuclear Fuel Development Corporation (PNC) Discussions centered on an applicability of the numerical method for the damping effects of the temperature fluctuations in the course of heat transfer to the inside of structures from the fully turbulent region of sodium flows through the comparisons with the experiment From these comparisons, it was confirmed that the numerical method has a sufficiently high potential in accuracy to predict the damping effects of the temperature fluctuations related to the thermal striping phenomena Consequently, it is concluded that the numerical prediction by the method developed in this study can replace conventional experimental approaches using 1:1 or other scale model aiming at the simulation of the thermal striping phenomena in actual liquid metal fast breeder reactor (LMFBR) plants Furthermore, economical improvements in the FBR plants can be carried out based on the discussions of optimization and rationalization of the structural design using the numerical methods

Exact solution of the problem of the equilibrium configuration of the charged surface of a liquid metal

Abstract: A broad class of exact solutions is obtained for the problem of the equilibrium configuration of the charged surface of a conducting liquid allowing for capillary forces. An analysis of the solutions showed that when the amplitudes of the perturbations reached certain critical values, the region occupied by the liquid ceases to be singly connected, which corresponds to the formation of liquid metal droplets. It is shown that a steady-state liquid metal profile may exist for which appreciable local amplification of the electric field can be achieved.

Method for metal coating of fibres by liquid process

Abstract: The invention concerns a method for metal coating of fibres (15) by liquid process, said method being particularly but not exclusively designed for coating in thick and even layers (22) with metals and metal alloys having high melting point and reactivity. Said method is characterised in that it consists in moving along the stretched fibre (15) in the liquid metal maintained in levitation in a well (1), said fibre (15) passing through orifices (6, 7) provided in the well (1) wall (3), said orifices (6, 7) being arranged on either side of the liquid metal at places where the liquid metal (10) is not in contact with said wall (3).

Resonant oscillation of a liquid metal column driven by electromagnetic Lorentz force sources

Abstract: In this paper, a theoretical study is conducted in order to establish the feasibility of a liquid metal acoustic resonator (liquid gallium or liquid aluminum) for high-amplitude acoustic oscillations. The fundamental resonant frequency typically lies between 5 and 40 kHz. The oscillations are induced by an alternating Lorentz force density applied directly to the liquid metal volume. Depending on the boundary conditions, two different resonator types (open–closed and open–open) are theoretically investigated. The analysis incorporates the effects of impedance termination, volume absorption, wall friction, acoustic radiation from the open end, and nonlinear inflow–outflow losses. The actual elasticity of the container, either a ceramic or quartz tube, and the coupled solid–liquid interactions are taken into consideration. Based on this investigation, theoretical predictions are conducted for the quality factor and the pressure level for the liquid metal resonator under various geometric and boundary condit...

Melting boundary of Fe-17%Si up to 5.5 GPa and the timing of core formation

Abstract: Melting of Fe-17wt%Si has been investigated at temperatures up to 1600°C and pressures up to 5.5 GPa in a cubic anvil press. The melting temperature, TM, was identified with the discontinuity in temperature and pressure dependence of electrical resistance. Two types of electrode materials, Pt and Fe, were used and gave consistent melting results. TM increases with pressure from 1200°C at 1 atm to 1430°C at 5.5 GPa. dTM/dP decreases with pressure and reaches a value of zero at P∼5 GPa. Combined with the thermal profiles of the proto-Earth, the pressure independence of the melting boundary of Fe-17%Si at the highest pressures of this study suggests core formation began early in Earth accretion with a substantial liquid metal phase fraction between 30 Ma and 42 Ma.

Application of the Zisman critical surface tension technique to ceramic surfaces at high temperature

Abstract: The critical surface tension technique is one of many possible approaches that can be used to determine the energy of ceramic surfaces at high temperature Although it has been shown to agree with other techniques used at low temperature, previous attempts at high temperatures have failed This study is the first to use this technique successfully at high temperatures It was accomplished by (1) carefully avoiding bulk oxidation and liquid-solid reactions and (2) using high purity, homologous, high-temperature liquids High-purity Group IIIA metals form the homologous series of liquids used for characterizing single crystals of α-Al2O3 Experimental conditions were controlled to produce sessile drops that had submonolayer oxide films on the liquid metal The results for oxygen-saturated, liquid-solid interfaces yield an average value of 1590 mJ/m2 for the surface energy of {0001} and {1120} surfaces of sapphire at 1073K These results are in excellent agreement with prior measurements of the surface energ

Heat transfer during boiling of a liquid metal during emergency cooldown of a fast-neutron reactor

Abstract: The physics of the processes, the characteristics, and the stability of different regimes, of boiling (nucleate, projectile, disperse-ring), which are observed in experiments investigating the boiling of liquid-metal coolant in a model of a fuel assembly for a fast-neutron reactor in the emergency cooldown regime with low circulation velocity, are analyzed. The experimental setup, the, methods for performing measurements, and the experimental data on the boiling of a liquid metal are described. A mathematical model of the process of boiling of a liquid-metal, coolant in a natural-circulation loop is described, and the results of test calculations for regimes with an increase in heating and with sharp pressure drop are prresented. 7 figures, 12 references.

Electromagnetic Confinement Including the Dynamic Effect Due to Melt Flow

Abstract: A 2 dimensional model has been developed to predict the free surface shape of liquid metal in an electromagnetic field, in which the field calculations have been coupled with the free surface shape change and the dynamic effect of the liquid metal flow. This has allowed the interactive phenomena in a coreless induction furnace to be simulated comprehensively and resulted in satisfactory agreement between the predicted and the measured meniscus shapes. Studies of the recirculating flow in molten aluminium have shown interactions of the meniscus shape with the flow field and therefore demonstrated the importanceof having detailed knowledge of the free surface shape in the electromagnetic processing of materials. In addition, the influence of the electrical conductivity and the skin effect in the induction coil on the electromagnetic confinement and the melt flow have been analysed.

Physical and thermal processes during electron beam welding

Abstract: Complicated processes of the seam formation during electron beam welding are described. The physical processes in the weld pool and in the vapor-plasma mixture emitted in the cavity into the liquid metal created by intensive high energy beam are discussed. The dynamics of the liquid metal in the weld pool are interconnected with the energy distribution of the electron beam in the cavity which influences the weld depth and width and controls the defect formation in the weld such as pores (blow holes), non-uniformity of the weld root (spiking) and rippled weld surface. The moving heating source, working in the weld pool of metal samples is steady only as a first approximation due to the molten pool dynamics. A more exact heat model of the electron beam welding must take into account the unstable nature of beam transport within vapors and gas plasma in the cavity as well as the variations of energy dissipation on the crater walls and of heat transfer through molten metal of the weld pool.

A Capacitance Probe for Measurement of Bubbles in Molten Metals

Abstract: A probe has been developed for measuring bubble size, velocity and frequency in molten metals. The probe has been tested on a low melting point alloy (Belmont alloy) and on aluminum. Bubble signals are discernible in either metal. The probe measures the change in capacitance between a wire and the metal as a bubble passes. Because there is no electrical contact necessary between the wire and the metal, the wire may be sheathed with a material (e.g. alumina) that is inert to the metal. The ruggedness of this design was demonstrated by its use for three hours in aluminum. A bridge circuit which can measure the small capacitance change was devised and a deconvolution procedure has been developed whereby bubble size distributions can be obtained. Measurements have been made of the bubble size and velocity above J-shaped nozzles through which argon was injected. Similar measurements have been made of the bubble size distribution above a porous alumina plug and the bubbles were larger than those observed in water at a comparable flowrate.