Prediction of Bubble Size Distribution in Aluminium Foam as a Function of %Titanium Hydride Addition

Abstract

Foaming of liquid aluminium by addition of foaming agent (TiH2 particles) is numerically simulated using population balance equations. Phenomena such as hydrogen release by the TiH2 particles, heterogeneous nucleation of bubbles in oxide surface cavities, and diffusion based bubble growth are modelled. A simple mass transfer coefficient, which varies inversely with the bubble size is used to estimate the bubble growth rate. Simulation is performed to study the effect of TiH2 content on the final bubble size distribution, total number of bubbles and average bubble size. In general, the average properties of the predicted distributions are close to the experimental values, whereas the spread in the bubble size is observed to be considerably narrower for the predicted values. The deviation in the spread of the distributions is attributed to the inverse bubble size dependent growth rate and non-inclusion of bubble coalescence in the model.