A two-dimensional, axi-symmetric model is developed to calculate flow and heat transfer in a two-fluid system. The model uses one set of the governing equations combined with a volume tracking method on a fixed structured mesh to model the simultaneous movement of mass, momentum and energy across cell boundaries. Both first and second-order methods are used to approximate temperature fields with sharp gradients that exist near a fluid-fluid interface.; The model is first used to simulate the effect of surrounding air during a droplet impact. Bubble entrapment is observed in both numerical simulation and experimental photographs. The impact of water, n-heptane and molten nickel droplets on a solid surface is simulated. When a droplet approaches another surface, air in the gap between them was forced out. Increased air pressure below the droplet creates a depression in its surface, in which air is trapped. Different behaviors observed for water and n-heptane simulations are attributed to differences in wetting behavior.; Next, to demonstrate the capabilities of the model, the interfacial heat transfer from molten tin droplets falling in an oil bath is modelled. The development of vortices behind droplets is simulated and the effect of fluid recirculation and oil thermal conductivity on heat dissipation is studied.; The thesis concludes with application of the model to a study of interfacial heat transfer during jet break up. It is demonstrated that the change of fluid properties associated with interfacial heat transfer affects the jet break up and the resulting droplet size. It is also shown that obtaining a desirable droplet size during jet break up not only depends on hydrodynamic conditions such as nozzle diameter, jet initial velocity, and pressure, but also on thermal conditions such as the initial jet temperature and the surrounding fluid thermal properties.
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