Showing papers on "Liquid metal published in 1985"

Metal-Mold interfacial heat transfer

Abstract: During the solidification of metal castings, an interfacial heat transfer resistance exists at the boundary between the metal and the mold. This heat transfer resistance usually varies with time even if the cast metal remains in contact with the mold, due to the time dependence of plasticity of the freezing metal and oxide growth on the surface. The present work has studied interfacial heat transfer on two related types of castings. In the first type, a copper chill was placed on the top of a cylindrical, bottom gated casting. Using the techniques of transducer displacements and electrical continuity, a clearance gap was detected between the solidified metal and the chill. The second type of casting had a similar design except that the chill was placed at the bottom. Owing to the effect of gravity, solid to solid contact was maintained at the metal-chill interface, but the high degree of interface nonconformity resulted in a relatively low thermal conductance as indicated by solution of the inverse heat conduction problem. Finally, the influence of interfacial heat transfer on solidification time with three mold ma-terials is compared by a numerical example, and criteria for utilizing Chvorinov's rule are discussed.

Liquid-Metal Corrosion

Abstract: A review of corrosion and environmental effects on the mechanical properties of candidate structural alloys for use with liquid metals in fusion reactors is presented. The corrosion/mass transfer behavior of austenitic and ferritic steels and vanadium-base alloys is evaluated to determine the preliminary operating temperature limits for circulating and static liquid-lithium and Pb-17Li systems. The influence of liquid-metal environment on the mechanical properties of structural materials is discussed. Corrosion effects of nitrate and fluoride salts are presented. Requirements for additional data are identified.

Fluid flow phenomena in a single phase coreless induction furnace

Abstract: New measurement techniques for local velocity, magnetic field, and current density have been applied to the study of electromagnetic and hydrodynamic phenomena in a coreless induction furnace containing an aluminum alloy. The action of electromagnetic shields on the intensity and the structure of the liquid metal flow is reported. It is shown that the direction of the fluid flow and the number and sizes of the recirculating cells may be significantly modified; the electromagnetic stirring may also be practically canceled. The influence of the dimensions of the screens on the structure of the liquid metal flow is examined. Finally, the modification of the fluid flow phenomena is explained by the evolution of the electromagnetic force patterns.

Heat pipe stabilized specimen container

Abstract: A heat pipe stablized specimen container for irradiation of specimens at substantially constant temperature within a liquid metal cooled fast reactor comprises a heat pipe containing a vaporizable substance such as sodium The container is of double-walled construction with the gap filled with argon and at top of the container a volume of argon is trapped within a cavity of the liquid metal level within the container in such a way that retention of argon in this zone is not dependent on sealing welds in the structure of the container, the argon blanket in this zone affording thermal insulation at the top of the container and also around part of the heat pipe, viz an adiabatic section of the latter The heat pipe includes three layer wick structure 84 comprising an outer relatively fine mesh layer, a coarse intermediate layer and a fine inner layer for promoting unimpeded return of condensate to the evaporation section of the heat pipe while enhancing heat transfer with the heat pipe wall and reducing entrainment of the condensate by the upwardly rising vapor

Recent results on thermophysical data of liquid niobium and tantalum

Abstract: Mesures de fusion, de chaleur specifique et de variations mutuelles entre la resistivite electrique, l'enthalpie, la dilatation en volume et la temperature jusqu'au point normal d'ebullition

Heat transfer device for the transport of large conduction flux without net mass transfer.

Abstract: A device for the transport of large conduction heat flux between two locations of differing temperature includes a pair of fluid reservoirs for positioning at the respective locations connected by at least one duct, and preferably a plurality of ducts, having walls of a material which conducts heat. A heat transfer fluid, preferably a liquid, and preferably a liquid metal such as mercury, lithium or sodium, fills both reservoirs and the connecting ducts. An oscillatory axial movement or flow of working fluid is established within the ducts, with the extent of fluid movement being less than the duct length. Preferably the oscillatory movement is sinusoidal. Heat is transferred radially between the fluid and the duct walls and thence axially along the ducts. The rate of heat transfer is greatly enhanced by a physical mechanism which may be described as a high time-dependent radial temperature gradient produced by fluid oscillations. During most of each sinusoidal cycle, fluid in the wall-near region has a temperature different from the core of the fluid column, with most of the temperature difference concentrated across a relatively thin boundary layer.

Experimental facility for studying MHD effects in liquid metal cooled blankets

Abstract: The capabilities of a facility, brought into service to collect data on magnetohydrodynamic (MHD) effects pertinent to liquid-metal-cooled fusion reactor blankets, are presented. The facility, designed to extend significantly the existing data base on liquid metal MHD, employs eutectic NaK as the working fluid in a room-temperature closed loop. The instrumentation system is capable of collecting detailed data on pressure, voltage, and velocity distributions at any axial position within the bore of a 2 Tesla conventional electromagnet. The axial distribution of the magnetic field can be uniform or varying with either rapid or slow spatial variations. The magnet gap dimensions, for the uniform field of 2T, are 15.3 cm high × 0.76 m wide × 1.83 m long. NaK was circulated in December 1984 and the magnet was energized in March 1985. Shakedown tests in a round pipe test section are currently underway.

Apparatus and method for forming fine liquid metal droplets

Abstract: An apparatus for generating fine liquid metal droplets from a liquid or molten metal comprises a rotatable member situated in a pressurized or evacuated chamber. Means are provided for generating an electric field at the edge of the member having sufficient strength to overcome the surface tension of the metal. A liquid metal delivery means directs liquid metal onto a surface of the member over which the metal flows toward the edge as the member is spun. As the liquid metal leaves the surface at the edge, the force of the electric field causes fine liquid metal droplets which are more uniform and smaller than those produced without an electric field to form. A method for forming fine liquid metal droplets is also disclosed.

Gallium-Based Liquid-Metal Full-Film Lubricated Journal Bearings

Abstract: Experiments have been carried out on full-film journal bearings lubricated with a low-vapor pressure liquid metal (gallium-based alloy) in argon and high vacuum. Plain and spiral-groove bearings of relatively small size and without additional liquid sealing were selected. The effect of reactive gases on the liquid-metal confinement and the influence of liquid-metal properties on the loci of the shaft centers were studied. For plain bearings, it is found that the shaft center locus followed a straight line with a load angle of π/2. Subambient pressures of 25 atmospheres magnitude were achieved in the metal lubricant film. Liquid-metal leakage did not occur up to a certain speed. It is shown that Ga-based alloys can effectively be applied as a reliable lubricant in spiral-groove bearings under nonoxidizing conditions. Surface tension and cohesion strength of the metal liquid played a significant role in lubricant behavior.

Double tube steam generator

Abstract: A double tube modular coil steam generator is provided in which a multiplicity of inner tubes conducting water are individually surrounded by outer tubes containing liquid metal as a heat transfer agent. The double tubes form into coils, providing a large surface area while conserving space. Immersion of the double tube coil in hot liquid metal, e.g., from the core of a nuclear reactor, causes efficient transfer of heat across the liquid metal in the outer tube to the water in the inner tube, creating superheated steam, which can be cycled to a turbine and converted to electrical power. The efficiency, reliability and safety of the multiple double tube design of the steam generator obviates the necessity of many secondary heat removal and emergency components in addition to conserving space and material. The modular design allows ease of operation, fabrication and repair.

Fast neutron nuclear reactor with a steam generator integrated into the vessel

Abstract: Fast neutron nuclear reactor of the type comprising a primary circuit integrated into a liquid metal-filled vessel and containing the reactor core, as well as means for circulating the said liquid metal and means for transferring the heat carried by the liquid metal to the water circulating in a water/steam circuit, wherein the heat transfer means comprise at least one steam generator located in the reactor vessel and having at least one group of inner tubes in which circulates the water of the water/steam circuit, at least one group of outer tubes immersed in the primary liquid metal, the outer tube surrounding each of the inner tubes in order to define therewith an annular space under a neutral gas pressure, connected to secondary circuit with a low thermal power having means for circulating this pressurized neutral gas, such as helium in said annular space and ensure the heat exchange.

Secondary metallization by glass displacement in ceramic substrate

Abstract: A process for increasing electrical conductance of a metallization on a ceramic substrate wherein the metallization is an intermixture of continuous phases of refractory metal and glass which comprises contacting the refractory metal with an electrically conductive intrusion metal and heating the resulting structure to a temperature at which the glassy phase is fluid, the refractory metal is solid, and the intrusion metal is liquid whereby the liquid metal preferentially wets the refractory metal, migrates into the metallization displacing glass and, upon subsequent solidification, partially or wholly occupies the volume space originally containing the continuous glass phase.

Mass density of liquid tellurium under high pressure

Abstract: The mass density of liquid tellurium has been measured up to 1100°C and 3 kbar (3 × 108 Pa). The maximum observed in previous works in the curve of mass density versus temperature at normal pressure is preserved for all the isobaric curves in the pressure range explored here. The isothermal compressibility is found to be larger than is usual for a liquid metal and may be related to the structural evolution of the liquid. A liquid metal-like model for the equation of state is used and compared with experimental data. The method takes into account a hard-sphere pressure term due to the ions and a cohesive pressure term due to the electrons; it leads to a mean valency value of about 2·75, which is in fair agreement with values determined by other methods.

Preparation of liquid metal source structures for use in ion beam evaporation of boron-containing alloys

Abstract: A process for preparing a liquid metal ion source structure, preferably made from graphite, so that it may be wetted with boron-containing alloys. The process first involves the coating the source structure with elemental boron. The boron is preferably furnished as boron powder in a liquid carrier which may then be coated onto the surface of the source structure substrate. The coated structure is heated for a short time to a temperature whereat the source structure substrate and boron form a liquid layer at the surface of the substrate to "boronize" the substrate. The final wetted source structure is achieved by mixing a small amount of free boron powder with the alloy to be ion evaporated (also in powdered form), coating the previously boronized source structure with this mixture and heating the contacted boron-augmented source alloy and source structure to a temperature of at least the solidus temperature of the source alloy, at which point the source structure is wetted. Once wetted, a flow of source alloy toward the emitter tip of the source structure can be established during operation of the ion source. Prior boronizing may be omitted for some boron carbide source structures.

Electroplating device by molten salt bath

Abstract: PURPOSE: To prevent the carrying of moisture into a system and carrying of a molten salt out of the system by providing vessels for a liquid metal which does not stick to a material before and behind a molten salt bath cell, executing plating of the material via such liquid metal and maintaining airtightly the bath cell. CONSTITUTION: A steel strip 1 is passed by a deflecting roll 10 into the liquid metal which does not stick to the strip 1 in the inlet side vessel 9 and is introduced by conductor rolls 4 and sink rolls 3 into the molten salt bath cell 2. The strip 1 is passed between anodes 5 and is thus electroplated. The plated strip is then passed by a direction changing roll 13 into the liquid metal which does not stick to the strip 1 in the outlet side vessel 11. The liquid metal having the specific gravity heavier than the specific gravity of the molten salt is used for the liquid metal in the vessels 9, 11 and Pb, Pb alloy are more preferable. The terminal of a cover 6 of the cell 2 is immersed into the liquid metal in the vessels 9, 13 to provide liquid sealing, by which the inside of the system is airtightly maintained. COPYRIGHT: (C)1986,JPO&Japio

Electrical and Magnetic Properties of the Liquid Tl‐BiTlTe3 System

Abstract: The electrical conductivity, the magnetic susceptibility and the thermoelectric power of the liquid Tl-BiTlTe3 system are measured as a function of temperature and composition from near the liquidus temperature up to 900 °C. The electrical conductivity of these alloys increases with increasing temperature, which however does not follow a simple Arrhenius type activation process because of a large metallic contribution. The diamagnetic susceptibility of the alloys decreases with increasing temperature, which seems to be mainly due to an increase in paramagnetic

Freezing controlled penetration of molten metals flowing through stainless steel tubes

Abstract: The freezing controlled penetration potential of molten metals flowing within stainless steel structure is important to the safety assessment of hypothetical severe accidents in liquid metal reactors. A series of scoping experiments has been performed in which molten stainless steel and nickel at various initial temperatures and driving pressures were injected downward and upward into 6.4 and 3.3 mm ID stainless steel tubes filled with argon gas and initially at room temperature. In all tests, there was no evidence that the solid tube wall was wetted by the molten metals. The penetration phenomena are markedly different for downward versus upward injections. The dependency upon tube orientation is explained in terms of the absence of wetting. Complete plugs were formed in all experiments halting the continued injection of melt. Calculations with a fluid dynamics/heat transfer computer code show that the injected masses limited by plugging are consistent with freezing through the growth of a stable solidified layer (crust) of metal upon the solid tube wall. 23 refs., 5 figs., 2 tabs.