Nonequilibrium Thermal Response of Porous Media in Unsteady Heat Conduction With Sinusoidally Changing Boundary Temperature

The thermal response of porous foam filled with a solid material was theoretically investigated under unsteady heat conduction with a sinusoidally changing boundary temperature. The local thermal nonequilibrium (LTNE) effect between the porous foam and the infill was obvious, and the two-equation model is employed for the unsteady heat conduction in porous-solid system. The temperature difference, which was defined as the time average of the absolute value of the difference between the temperatures of the porous solid and the infill, was proposed for quantitatively describing the LTNE effect in porous media. The LTNE phenomenon for unsteady heat conduction in porous media is influenced by the fluctuation period of the thermal boundary, foam morphology, and the thermal diffusivities of the porous solid and the infill. The LTNE effect of unsteady porous-media heat conduction was evident in the region near the thermal disturbance boundary. The maximum temperature difference was found on the curve of temperature difference versus fluctuation period, which means that the thermal response characteristics of porous composites resonate with periodically changing thermal disturbance. The fluctuation period corresponding to the maximum temperature difference has positive correlations with thermal diffusion resistance for unsteady porous-media heat conduction.