These systems allow to determine the effective average conductivity in a bed of solid particles. Unlike traditional systems for the determination of thermal conductivity in pure materials, this system allows to obtain the effective conductivity in a no-homogeneous medium, such as a packed bed of particles. The system allows determining the effective conductivity with different fluids circulating in the bed and in different directions (axial or radial) as well as quantifying the influence of natural convection in the system. The system has been developed and designed by the research group.