Melting of a sphere in hot fluid

Abstract

Solid bodies immersed in hot fluids may melt. The molten material produced can then mix with, and be assimilated into, the fluid influencing its compositional and thermal states. Compositional convection of melt and thermal convection of cooled fluid around the solid determine the heat flux from the fluid to the solid's surface. This, together with the thermal properties of the solid, controls the rate of melting. Experiments on melting wax spheres into water are described; these have shown how variations in the nature of melt flow round the sphere cause differing melting rates and hence the development of a distinctive melting morphology. Melting rates are calculated by a simple theoretical analysis which estimates melt layer thickness and the heat flux from the fluid. Melting rate predictions agree well with the experimental data. A geological application occurs when magma incorporates blocks of its surrounding wall rock. Relatively rapid melting rates are estimated, typically in the order of a half metre per day. Such fast rates indicate that this method of contamination may be an important influence on magmatic evolution in continental environments.