This MSc thesis reports on an experimental study performed to test the effects of packed beds of relatively large spheres on natural convection inside a cubical enclosure which is heated from the left side and cooled from the right side. With ’relatively large’, a ratio of L/D=5 is meant where L is the length between the hot and cold plate and D is the diameter of each sphere where the packed bed consists of. To gain a better understanding and enhanced knowledge of the effects of coarse-grained porous media on side-heated natural convection, heat transfer experiments were performed as well as flow and temperature distribution measurements using the optical measurement techniques Particle Imaging Velocimetry (PIV) and Liquid Crystal Thermography (LCT). In the optical measurement experiments, hydrogel balls were used which have the same refractive index as that of water.