This article describes numerically the time evolution of an expanding mixture of hot spherical particles, steam, and water. It is assumed that at time t = 0 the mixture components are distributed uniformly through Ike mixture volume. The mixture expands against a body of water in which it is immersed. The expansion is due to steam generation; it is assumed that the hot particles remain equidistant as the mixture expands. The numerical procedure is based on the moving finite element method. The fluid particles are distributed throughout the domain and are moved in time in a Lagrangian manner to simulate the change of the domain configuration. Mathematically, the problem is formulated as a nonlinear initial boundary value problem with unknown quantities of an objective Junction (velocity potential) and the profile of the domain. The governing equation is discretized spacewise using the Galerkin finite element method. During expansion, the number of mesh elements remains unchanged, while the location of the nodes changes. The movement of the mesh nodes is attacked to the movement of the flow. The focus is on the energy conversion efficiency of the process, i.e., on the extent to which the heat released by the hot material is converted into kinetic energy. The results document the effects of changing the hot-particle size and water pool size. It is shown that the efficiency decreases almost inversely with time and that for times in the 1-ms range it has values of the order of 1%.
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