| The current research consists of three parts. First, an analytical and experimental investigation was conducted to study the transient response of a stagnant air-saturated porous medium to rapid thermal perturbation. In this work, two separate experiments were performed. One is a steady-state experiment to estimate the equivalent thermal conductivity and the other is the transient experiment. Results show that for rapid heating significant discrepancy exists between experimentally acquired temperature data and the temperature predicted based on the classical Fourier heat conduction equation especially in the near-field region. Experimental evidence have shown that a significant discrepancy between the values and physical meaning of the parameters: lag time τt, in temperature due to interstitial heat transfer coefficient h, and lag time in the transient response of the temperature gradient τx in heat flux equation.; In the second part of this research, an approximate theoretical enthalpy model developed to study the phase change process in porous media. During the melting or the freezing process, the interface within a pore remains at the phase change temperature until the process is completed. An approximate two-temperature model is studied analytically. The results provide the parametric information concerning the phase-change front. Also, the conditions that would assure the existence of local thermal equilibrium are presented.; The last part of this research is an experimental investigation of phase change phenomena in porous medium. The phase change material (PCM) used in this study is n-tetracosane. This study consists of two parts: the steady state and the transient experiment. The steady state experiment is used for the estimation of the equivalent thermal conductivity of the PCM saturated porous medium, and the transient experiment provides information needed for the estimation of the interstitial heat transfer coefficient h.; Results indicate that a finite time is needed for the solid matrix and the pore material to attain local thermal equilibrium condition. According to experimental data, the effect of τt and τ q is negligible as the physical time t goes to infinity. This suggests the discrepancy between results predicted based on local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) diminishes as the physical time approaches infinity.; Based on experimental data, the location of the phase change front was determined. A comparison between the theoretically and experimentally predicted phase front indicates an excellent concordance. (Abstract shortened by UMI.)... |
