Liquid Metal Pool Research Articles

The burning rates of sodium pool fires

The burning rates of sodium pool fires have been measured at pool diameters of 50, 100, and 220 mm. The pool burning was found to exhibit a flat flame zone residing close to the surface of the liquid metal pool. Well-insulated pools attained an equilibrium temperature of ≅1000 K. Brief results from other aspects of sodium combustion are reported. These are the variation of burning rate with pool temperature, the smoke release fraction from small pools, and spectroscopic observations from sodium vapour/air laminar diffusion flames. From these observations and the results of other workers, a model of sodium pool burning is produced dealing in particular with the variation of burning rate with pool size. This analysis forms the basis of prediction of heat release and smoke release rates as may occur from large pool fires following accidents in sodium-cooled fast breeder nuclear reactors.

Flow behaviour of liquid metals on solid substrates

Abstract The influence of both fluid flow and heat transfer on the shape of a liquid metal pool has been studied by pouring liquid 50%Pb-50%Sn alloy onto a colder stainless steel substrate in air. The liquid alloy does not wet the solid substrate and the shape of the pool is governed principally by the balance of forces due to gravity and surface tension. The momentum of the entering liquid provides an additional force which favours spreading. Inertial forces are significant only in the beginning, when the width of the pool is <10 mm. Viscous forces become important in retarding flow whenever the alloy cools to between the liquidus and solidus temperatures (into the ‘mushy’ zone) because of heat transfer to the cold plate. The flow of liquid alloy over the substrate occurs predominantly by a ‘penetrating’ mechanism, in which fresh liquid is incorporated into the pool at the centre to the full depth and simply displaces the existing mass outwards. Temperature-response measurements tend to confirm that this...

Growth of a bubble at a heated surface in a pool of liquid metal

A theoretical investigation of the initial vapor bubble growth from a heated surface wall in a pool of liquid sodium is reported. The analysis assumes the bubble to have the shape of a spherical sector, at the base of which a thin liquid microlayer is retained on the heating surface. The effects of time-and-space dependent heat conduction in the solid, microlayer vaporization, and non-equilibrium condensation on the bubble upper surface are considered. A two-term expression for the bubble growth rate is obtained by a collocation procedure. Calculated results predict the growth of the bubble on a heated surface as a function of the heat flux, the external pressure and the thermophysical properties of the liquid and solid. An expression due to Ruckenstein, modified to take into account the effective contact angle, is used to determine the departure bubble diameter. This turns out to be sensitive to the contact angle, and less strongly influenced by the bubble drag coefficient. The growth is initially inertiacontrolled, but heat-transfer effects become significant before departure. In this pressure range (0·1–1 atm) the presence of inert gas, by reducing the effective accommodation coefficient for condensation, increases bubble growth rate moderately.

The grape cluster, metal particle 63344,1

Metal particle 63344,1 consists of hundreds of metallic globules welded together to form a structure somewhat like a bunch of grapes. It is the largest lunar metal sample found to date, over 5 mm in its longest dimension. Silicate material is attached to the outside of the sample and consists mainly of glass and fragments of An-rich plagioclase derived from a regolith composed of fragments of highland-type rocks. The globules are all of the same composition (6.25 wt.% Ni, 0.35 wt.% Co, 0.8 wt.% P and Fe) and were produced at the same time and from the same source. No primary solidification structure was observed in the globules. A Widmansta¨tten pattern of kamacite in taenite and a precipitation pattern of phosphides, which were equilibrated to a temperature of ⪯600°C, also developed in the metal. The metallographic evidence indicates that the particle was slow cooled from the solidification temperature (∼1300°C) taking days to possibly months to reach 600°C. Two possible mechanisms are proposed for the formation of the globules of 63344,1. One mechanism involves the primary impact of an iron meteorite which produces a metallic liquid and vapor phase. The second mechanism involves the formation of a liquid pool of metal after impact of an iron meteorite projectile followed by a secondary impact in the liquid metal pool. Both mechanisms call for special conditions and sequences of events in order to form a chemically coherent cluster of metal globules uncontaminated by silicates. These globules may adhere after partial solidification and the particle may be slow cooled by burial 0.5–5 m deep in the original ejecta blanket.

Drop transfer in short-circuit welding

This paper considers the physical processes which may occur when a liquid weld metal drop comes in contact with a liquid metal pool. Experiments with drops of aqueous KCl solutions and mercury, combined with a theoretical analysis of the effects of surface tension and Lorentz forces, lead to the following conclusions. Drops larger than a critical size, which is a function of the capillary constant and wire diameter, will transfer to the pool and smaller drops will lead to stable menisci. Surface tension alone will complete the interaction in approximately k(M/4πT)1/2 s, where M and T are the drop mass and surface tension in CGS units and k similar 3·7. An electric current I can result in a repulsive force on drops of radius less than approximately μ0I2/16π2T (MKS units). The magnetic pinch instability can dominate surface tension effects under extreme conditions, and magnetically induced streaming can make otherwise stable menisci unstable. Applied to short-circuiting MIG welding systems, these results show how proper attention to the current and weld metal surface tension can lead to reduced spatter and better process control.

Mixing in Liquid Metal Pool during Electroslag Remelting

Mixing in Liquid Metal Pool during Electroslag Remelting

Distribution of inclusions in rare earth treated steel ingots

study has been made of inclusion segregation in ingots of rare earth treated O·1%C–1·35%Mn–o·025%S steel. It has been shown that the distribution and aggregation of inclusions is a sensitive function of the solidification mode. On a macroscopic scale, the occurrence of bottom-cone segregation in high-sulphur rare earth treated ingots has been confirmed, and a mechanism has been advanced to account for the phenomenon. This mechanism involves the scavenging of inclusions in the bulk melt by sedimenting dendrites during their descent to the bottom of the liquid metal pool, and emphasizes the interrelation between bottomconeformation and the existence of an ingot equiaxed zone.