Experimental investigation of heat conduction in wet sand

There has been a lasting discussion in the literature on the validity of Fourier's heat conduction law. The main concern is the inherent infinite propagation velocity of temperature changes. Some authors hold that due to this problem the law should fail for certain materials or on extreme time scales. Then, to reconcile experiment with theory Fourier's equation would need an extension to a hyperbolic form. To contribute to this matter we report on unsteady heat conduction experiments in wet sand for which hyperbolic behaviour (Kaminski 1990) was documented. Our results clearly salvage Fourier's law without giving any explanation on why a theory with a serious inconsistency can work so well.