Systems and apparatus for mixing, cooling, and distributing multiphase fluid mixtures within a reactor, wherein reactor internal apparatus of the present invention provides not only improved fluid mixing and distribution to each underlying catalyst bed surface, but also offers other advantages including: decreased mixing tray height; easier maintenance, assembly and disassembly; and decreased amounts of fabrication material. In an embodiment, fluid may be evenly distributed to a catalyst bed from a fluid distribution unit comprising a nozzle tray including a plurality of nozzles, wherein the nozzles include at least one liquid inlet disposed tangentially to an inner surface of the nozzle.