The water-cooled lead lithium (WCLL) blanket is one of the European concepts for a Demonstration nuclear fusion reactor (DEMO). The spatial distribution of the water-cooling pipes inside the liquid metal blanket breeder zone is a critical issue since efficient heat removal from the liquid metal has to be ensured, avoiding local hot spots in the fluid or in blanket walls. Convective motion, driven by density gradients due to volumetric heat sources in the liquid breeder and heat removal by cooling pipes, is affected by magnetohydrodynamic interactions of the electrically conducting lead lithium with the external magnetic field. For the recent complex design of the DEMO WCLL blanket, prediction of the liquid metal flow is quite difficult. Preliminary numerical and experimental studies are necessary to determine the flow distribution resulting from the combined interaction of electromagnetic forces, buoyancy, and pressure. A test section based on a simplified model geometry supported by preliminary numerical simulations has been designed for experiments in the MEKKA laboratory at the Karlsruhe Institute of Technology and is presented in this paper.