  The paper presents a theoretical study using the Karman-Pohlhausen method for
describing the transient heat exchange between the boundary-layer free
convection and a vertical flat plate embedded in a porous medium. The unsteady
behavior is developed after the generation of an impulsive heat flux step at
the right-hand side of the plate. Two cases are considered according to whether
the plate has a finite thickness or no thickness. The time and space evolution
of the interface temperature is evidenced.
