The biphasic flow through the reactor internals has been studied experimentally and numerically. Experiments have been carried out with a configuration operating under ambient pressure for two configurations. The first configuration consists of a mixing box orifice inlet through which liquid flows as a film cut by a gas flow. The height of the liquid at the orifice inlet is documented in a wide range of liquid and gas flows. The second configuration consists of the two-phase flow through a down tube of a distribution tray. Dynamic simulations of two- and three-dimensional computational fluids (CFD) have been used using the fluid approximation volume to calculate both flows for flow conditions similar to those used in the experiments. It is shown that the agreement between experiments and calculations is very good. Based on this good agreement, it is finally discussed how CFDs can be used to achieve better design rules for liquid gas reactor internals through simulations performed for the conditions of the industrial process.