A decomposition reactor for an exhaust system includes an exterior component defining an internal volume and having an inlet and an outlet with the inlet and outlet are formed on a same side of the exterior component. A flow divider is positioned within the internal volume and defines a thermal management chamber and a main flow chamber. A first flow path of exhaust flows from the inlet into the main flow chamber to mix with dosed, and a second flow path of exhaust flows from the inlet into the thermal management chamber to control a temperature of a portion of the flow divider. In some implementations, one or more swirling diverters can be coupled to the flow divider and positioned proximate the outlet of the exterior component to impart a vortical motion to a combined reductant and exhaust gas flow exiting out the outlet.