Showing papers on "Liquid metal published in 1982"

Inward Melting in a Vertical Tube Which Allows Free Expansion of the Phase-Change Medium

Abstract: Experiments on the melting of a phase-change medium in a vertical tube yielded quantitative results both for the heat transfer and the timewise evolution of the melting front. The upper surface of the phase-change medium was bounded by an insulated air space, which accommodated the volume changes which accompany the melting process. Numerical solutions based on a pure conduction model were also performed for comparison purposes. It was found that the rate of melting and the heat transfer are significantly affected by fluid motions in the liquid melt induced by the volume change and by natural convection, with the former being significant only at early times. For melting initiated with the solid at the phase-change temperatures, the experimentally determined values of the energy transfer associated with the melting process were about 50 percent higher than those predicted by the conduction model. Furthermore, the measured values of the energy stored in the liquid metal were about twice the conduction prediction. A compact dimensionless correlation of the experimental results was achieved using the Fourier, Stefan, and Grashof numbers. Initial subcooling of the solid substantially decreased the rate of melting, with corresponding decreases in the energy transfers for melting and sensible heat storage.

Multidimensional numerical modeling of heat exchangers

Abstract: A comprehensive, multidimensional, thermal-hydraulic model is developed for the analysis of shell-and-tube heat exchanges for liquid metal services. For the shellside fluid, the conservation equations of mass, momentum and energy for continuum fluids are modified using the concept of porosity, surface premeability and distributed resistance to account for the blockage effects due to the presence of heat transfer tubes, flow baffles/shrouds, the support plates, etc. On the tubeside, heat transfer tubes are connected in parallel between the inlet and outlet plenums, and tubeside flow distribution is calculated based on the plenum-to-plenum pressure difference being equal for all tubes. It is assumed that the fluid remains single-phased on the shell side and may undergo phase-change in the tube side, thereby simulating the conditions of Liquid Metal Fast Breeder Reaction (LMFBR) intermediate heat exchanges (IHX) and steam generators (SG). The analytical model predictions are compared with three sets of test data (one for IHX and two for SG) and favorable results are obtained, thus providing a limited validation of the model.

Method and means for converting graphite to diamond

Abstract: A host liquid, such as a liquid metal, which is "seeded" with small bubbles of an inert gas, is maintained in a sealed chamber at an ambient temperature of about 100° K. above the melting point of the host liquid, and at a static pressure ranging from 1 to 100 bars. A substance (for example carbon) which is capable of being allotropically transformed from a first form thereof (for example graphite) to a second form (for example diamond), is placed in the host liquid, which is then subjected to a time-varying acoustical pressure applied, for example, by a plurality of solid acoustical horns, which cause at least certain of the bubbles of inert gas to expand and then suddenly to collapse in a cavitation zone located substantially centrally of the chamber. By maintaining the host liquid at a pressure and temperature sufficient to cause the Hugonoit curve of the liquid to intersect a predetermined area of the phase diagram of the substance, the shock waves produced by the collapsing bubbles can be caused to envelop particles of graphite and to instantaneously transform them into diamond particles. The host liquid can be selected from a group consisting of aluminum, tin, gallium, thallium and indium, and alloys thereof; and the substance to be transformed may be selected from the group consisting of carbon, boron nitride and zinc sulphide.

Multidimensional numerical modeling of heat exchangers

Abstract: A comprehensive, multidimensional, thermal-hydraulic model is developed for the analysis of shell-and-tube heat exchanges for liquid metal services. For the shellside fluid, the conservation equations of mass, momentum and energy for continuum fluids are modified using the concept of porosity, surface premeability and distributed resistance to account for the blockage effects due to the presence of heat transfer tubes, flow baffles/shrouds, the support plates, etc. On the tubeside, heat transfer tubes are connected in parallel between the inlet and outlet plenums, and tubeside flow distribution is calculated based on the plenum-to-plenum pressure difference being equal for all tubes. It is assumed that the fluid remains single-phased on the shell side and may undergo phase-change in the tube side, thereby simulating the conditions of Liquid Metal Fast Breeder Reaction (LMFBR) intermediate heat exchanges (IHX) and steam generators (SG). The analytical model predictions are compared with three sets of test data (one for IHX and two for SG) and favorable results are obtained, thus providing a limited validation of the model.

The hydrodynamics of liquid metal ion sources

Abstract: Factors affecting the current‐voltage characteristics of liquid metal ion sources are reviewed. The results demonstrate that ion emission is not controlled by space‐charge effects but rather is determined by liquid flow limitations along the needle emitter. A hydrodynamic model is presented which predicts the experimental I‐V characteristics. The model suggests that a reduction in the energy spread (Boersch Effect) of the emitted ions may be achieved by increasing the needle flow impedance.

Measurement of the thermal conductivity of KNO3-NaNO3 mixtures using a transient hot-wire method with a liquid metal in a capillary probe

Abstract: The thermal conductivity of KNO3-NaNO3 mixtures was measured by a modified transient hot-wire method using liquid metal in a capillary as a heat source. The method was developed for measurements on electrically conducting liquids at high temperatures. Measurements were performed on pure NaNO3 and its three mixtures with KNO3 in the temperature range from 498 to 593 K.

Molecular Dynamics Study of the Structure of a Rapidly Quenched Metal

Abstract: The molecular dynamics method is used to simulate the rapid-quenching process of a simple liquid metal. The model consists of 864 particles with the density-dependent effective pair potential, which can describe the structure of liquid rubidium above the melting point. The rapid-quenching process from just above the melting point of rubidium down to around 4.2 K is simulated by subtracting the kinetic energy of particles intermittently with the quenching rate of 4.5×10 12 Ks -1 . In the final quenched state at 4.5 K both the pair distribution function and the structure factor show a feature of amorphous states, that is, the split second peak. The relative positions and the ratio of the heights of these split subpeaks are very close to those of the quenched argon (the molecular dynamics simulation) and also of amorphous iron (the evaporated film), and the final quenched state can be considered as a typical model of amorphous pure metals.

Liquid metal solar power system

Abstract: A solar power system for cogenerating heat and electricity is disclosed. An improved solar collector includes a transparent reflector envelope through which a reflective liquid metal such as mercury is circulated. The liquid metal is preheated as it focuses solar radiation onto the receiver of the collector module. A baffle tube within the receiver is perforated to permit the circulation of working fluid out of the absorption chamber of the receiver into the narrow annulus between the baffle tube and the receiver wall, thereby promoting the rapid generation of vapor. The liquid metal vapor is discharged through the channel of a magnetohydrodynamic generator for producing electrical power in a first power generating stage. The liquid metal vapor is condensed and accumulated in a primary storage reservoir for driving a turbine generator in a second generating stage, thereby providing electrical power during periods of insufficient solar radiation. Liquid metal discharged from the turbine is accumulated in a secondary storage reservoir for supplying the solar collector module during periods of adquate solar radiation.

Continuous metal casting method, apparatus and product

Abstract: The products of this invention are produced in an elongated casting vessel disposed in upright position to receive liquid metal for solidification within an electromagnetic field generating means disposed around the vessel along a portion of its length. The electromagnetic field generating means produces an upward lifting effect on liquid metal in the vessel together with a containment effect wherein the liquid metal is continuously urged upwardly into contact with the lower end of the solidifying product and maintained in a pressureless contact condition with respect to the walls of the casting vessel. In this way, voids and flaws are avoided and fully dense homogeneous products of uniform, small grain cross section result without wear on the casting vessel. The novel products of the invention are long metal bodies which are fully dense and of substantially uniform, fine grain cross section and constant composition throughout in each instance. In their as-cast condition, these bars, rods and other products have smooth, slightly wavy surfaces attributable to the fact that before, during and just after solidification, the metal of which they are formed is electromagnetically maintained out of contact with lateral support structure (such as the surface of a mold) and also due to the fact that the liquid metal at the solidification front is constantly stirred by induced eddy currents. The product may suitably be of multi-element composition which tends strongly to phase separation, however, because of the continuous stirring by induced eddy currents, the resulting products have a high degree of homogeneity.

A chemical theory for the thermodynamics of highly-solvated liquid metal mixtures

Abstract: Chemical solution theory has been shown to be particularly well-suited for certain classes of liquid metal mixtures. A generalized formulation of this approach is presented and it eliminates the need for mechanistic information. The results are in good agreement with many data, and could lead to a variety of industrial applications of liquid metal solvents.

Space-charge effects in liquid metal ion sources

Abstract: The space-charge problem is investigated for liquid metal ion sources, using analytic methods and idealised geometries. For a given current, the space-charge reduction in the electric field at the ion-emitting apex of the liquid anode depends on the apex radius, r0, assumed. The smaller r0, the greater is the extent of this field reduction-although, even at the lowest observable currents of approximately 1 mu A, r0 does not have to be particularly small for substantial reduction in the apex field to occur. However, the effects of space-charges are expected to diminish for ion sources of high flow impedance.

Effect of wave motion on chill cast surfaces

Abstract: The formation of exterior surface ripples, and their dependence on filling rate and superheat, was studied in bottom-poured ingots of low melting Sn-Pb alloys. It was found that surface waves in the liquid metal during mold filling are the basis for an important mechanism leading to formation of the primary exterior ripples. Imposition of a steady D. C. magnetic field strongly dampens the surface waves in the liquid metal, essentially eliminating the primary ripple marks throughout the bottom two-thirds of the ingots. The magnetic field also enhances columnar grain growth.

Electromagnetic flowmeter for liquid metal

Abstract: PURPOSE:To obtain an electromagnetic flowmeter of a reduced size for liquid metal by measuring the load exerted upon a device which applies a magnetic load upon the flow of the liquid metal thereby making the area formed with the magnetic field small without using any fixed electrode. CONSTITUTION:A torus-shaped bobbin 7 having a coil 8 is fitted onto a piping 6 in which liquid metal 4 flows; further the bobbin 7 is mounted to a supporting structure 14 by means of four load cells 13 located in positions deviated by 90 deg.. When the liquid metal 4 flows through the magnetic field formed by the coil supplied with DC, an eddy current flows in the inlet and outlet of the magnetic field in the liquid metal, and this eddy current forces the force in a down stream direction to act upon the coil 8, and since this force is proportional to the velocity of flow, the flow rate is determined by measuring this force as the added sum 15 of the outputs of the four load cells.

Device for the treatment of a stream of aluminum or magnesium-based liquid metal or alloy during its passage

Abstract: The invention relates to a device for the treatment of a stream of aluminum or magnesium-based liquid metal or alloy during its passage, comprising a ladle formed by an external metal casing, a refractory lining, a channel for the admission of the crude liquid metal at the rear, a nozzle for the casting of the treated liquid metal at the front, at least one internal partition leaving, with the bottom of the ladle, a space for the circulation of the liquid metal and defining a first rear compartment and at least one second front compartment opening into the casting nozzle. The ladle is fixed on a supporting cradle connected to an articulated frame relative to which the said cradle can rock forwards about a first horizontal axis passing through the casting nozzle, the articulated frame itself being connected to a fixed frame relative to which it can rock about the second horizontal axis. The first horizontal axis is approximately perpendicular to the stream of liquid metal. The second horizontal axis can be parallel or perpendicular to the first one and which includes a raisable cover, an immersion heater, an injector for agent for the treatment of the metal and a means 36 for alternately introducing and retracting the immersion heater and the injector.

Process for the precise and continuous injection of a halogenated derivative in the gaseous state into a liquid metal

Abstract: The invention relates to a process and an apparatus for the precise and continuous injection of a halogenated derivative, which is liquid at ambient temperature, into a liquid metal such as aluminum and aluminum-based alloys. The process involves withdrawing the halogenated substance from a tank, introducing it by means of a metering pump into a vaporizer which has been brought to a temperature at least equal to the vaporization temperature of the substance under the injection pressure, and entraining it in the vapor state by an inert gas stream towards an injection means opening into the center of the liquid metal.

Fast neutron nuclear reactor with internal capillary structure piping

Abstract: The invention relates to a fast neutron nuclear reactor equipped with residual power removal devices. Each device comprises an evaporator incorporating a bundle of tubes in glove finger-like form immersed in the liquid metal contained in the reactor vessel, an adiabatic collector constituted by a pipe traversing the slab sealing the reactor vessel and a condenser in which the heat transfer fluid, such as mercury, contained in said device is condensed by heat exchange with the atmospheric air sucked in through the chimney or flue. Application to fast neutron nuclear reactors.

Fast breeder reactor with a residual heat dissipation system

Abstract: Each device includes an evaporator (42) having a glove finger tube bundle immersed in the liquid metal (12) contained in the reactor vessel, an adiabatic collector (46) consisting of a duct (58) passing through the plate (16 ) closing the reactor vessel and a condenser (44) wherein the heat transfer fluid such as mercury contained in the device is condensed by heat exchange with the atmospheric air drawn into a chimney (82). Application to nuclear fast reactor.

Manufacture of fine ceramic particle

Abstract: PURPOSE: To obtain fine ceramic particles of narrow distribution in particle size, by atmoizing a liquid metal compound into a plasma flame, and melting and solidifying it. CONSTITUTION: The liquid body of a metal compound which remains requefied at an oridnary temp. or becomes requefied by simple heating, e.g. TiCl 4 or Fe(CO) 3 , is atomized into fine particles having diameters below 10μ by centrifugal atomization, ejection through an orifice, etc. Since a plasma flame such as a gas or water plasma flame is suited to drying the formed liquid drops, said liquid body is atomized into said plasma flame. COPYRIGHT: (C)1983,JPO&Japio

Liquid metal cooled internal combustion engine valves with getter

Abstract: A getter selected from the group consisting of zirconium, hafnium, yttrium, and mixtures thereof is used as an additive for metal coolants, e.g., sodium, potassium and sodium-potassium alloys, in metal cooled internal combustion engine valves.

Space-charge effects in liquid metal ion sources of different geometries

Abstract: The current work considers the effect of geometry, other than the ideal Taylor cone, on space charge and axial fields of liquid metal ion sources. Solutions of the spacecharge equation for the concentric sphere and hyperboloidal-planar models of a liquid emitter demonstrate a rather dramatic dependence of the space charge and axial fields on the geometry of the emitting surface.

Process for the manufacturing of a casting tube

Abstract: The tube (4) consists of a mixture of refractory particles and fibers embedded in a binder which is not resistant to the temperature at which the tube is heated during the passage of the liquid metal in its interior. The refractory particles are sinterable in an area of ​​the tube directly exposed to the heat of the liquid metal. The tube (4) further contains, at least in a region (4a) which is not directly exposed to heat from the liquid metal, this heat resistant refractory binder. Use in particular for transferring the liquid metal from a ladle to a tundish.

Method of treating and refining liquid metal alloys by direct current electric arc heating

Abstract: Method of and apparatus for treating and refining liquid metal alloys by direct current arc heating. On at least a part of the melt surface there is performed an electrolysis whereby the melt across a layer of liquid slag-electrolyte is connected as an anode or a cathode, and the connection with the other pole--cathode or anode--is effected by means of one or more direct current arcs. Depending upon the desired direction of the electrolysis process, it is possible to change the polarity of the metal melt or the slag-electrolyte. The apparatus for performing the method comprises a vessel equipped with a mechanism for pouring, a movable cover and movable electrodes. The centers of the electrodes are disposed symmetrically one to the other in a vertical plane. As a source of direct current there are used two or more rectifiers operating independently.