Diesel exhaust fluid cooled reductant delivery unit for selective catalytic reduction systems

A reductant delivery unit (RDU) for a selective catalytic reduction system, including a housing; a fluid inlet disposed at an upper portion of the housing; a fluid return outlet; a fluid nozzle outlet disposed at a lower portion of the housing; an injector disposed within the housing and configured to receive fluid from the fluid inlet and selectively discharge the fluid from the fluid nozzle outlet; and at least one fluid passageway disposed within or around the housing. The fluid passageway provides fluid communication along a first fluid path between the fluid inlet and the fluid nozzle outlet and along a second fluid path between the fluid inlet and the fluid return outlet so that the same fluid discharged by the injector is also used as a coolant for the RDU.