Numerical investigations have been performed to study transient heat conduction in composite materials. Macroscopic unsteady equations in porous media consisting of solids and fluids of different thermal properties were derived under the assumption of non-thermal equilibrium. The derivation leads a two-equation system which requires the closure modeling of tortuosity term and interfacial heat transfer term. The closure model proposed recently by Hsu (1997) has been extensively reviewed since it is the main base of this study. The closure coefficients were determined to demonstrate the dependencies on the media geometry and thermal property. A numerical scheme is developed to solve the two-equation model in one dimension. Parametric study has been presented with three sets of initial and...[ Read more ]

Numerical investigations have been performed to study transient heat conduction in composite materials. Macroscopic unsteady equations in porous media consisting of solids and fluids of different thermal properties were derived under the assumption of non-thermal equilibrium. The derivation leads a two-equation system which requires the closure modeling of tortuosity term and interfacial heat transfer term. The closure model proposed recently by Hsu (1997) has been extensively reviewed since it is the main base of this study. The closure coefficients were determined to demonstrate the dependencies on the media geometry and thermal property. A numerical scheme is developed to solve the two-equation model in one dimension. Parametric study has been presented with three sets of initial and boundary conditions to discuss the departure from local thermal equilibrium and the applicability of the two-equation model.

A three time domain numerical scheme has been adopted to study transient phase-change problem for pure substance. A numerical method has been constructed to obtain the solution of temperature distribution as well as the growth of the mushy zone, in which the solid and liquid phases co-exist at a definite phase change temperature. It can be seen that excellent agreement is observed between present numerical results and those of early works for pure substance.

The three time domain method has been extended for two equation model to investigate the problem of transient heat conduction with solid-liquid phase-change effect in composite materials containing of solid and fluid, where only fluid is identified as phase change material. Parametric simulations via a finite difference method have been directed towards the response of the phase-change process in a slab to an imposed surface temperature, having a uniform temperature with or without a time dependent sinusoidally varying perturbation. The effects of relevant parameters on the phase-change behavior are investigated.