Numerical modelling of metal droplet cooling and solidification

Zeoli, Nicola, Gu, Sai and Kamnis, Spyros (2008) Numerical modelling of metal droplet cooling and solidification. International Journal of Heat and Mass Transfer, 51 (15-16), 4121-4131. (doi:10.1016/j.ijheatmasstransfer.2007.11.044).

Abstract

In an atomisation process for power production, metal droplets go through undercooling, recalescence, peritectic and segregated solidification before fully solidified. The cooling process is further complicated by droplet break-up during the atomisation. This paper describes a numerical model which combines both cooling and break-up in a single computation. The dynamic history of droplets is solved as discrete phase in an Eulerian gas flow. The coupling between droplet and gas flows are two-way, in which the heat and momentum exchanges affecting the gas flow are treated as source/sink terms in the fluid equations. The droplet model is employed to a gas atomisation process for metal powder production and good agreement is achieved with the results in open literature. The model results further confirm that thermal history of particles is strongly dependent on initial droplet size. Large droplets will not go through undercooling while small droplets have identifiable stages of undercooling, unclearation and recalescence. The predictions demonstrate that droplets have very similar profiles during gas atomization and the major factor influencing the atomization and solidification process of droplets are in-flight distance.

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