An additively manufactured heat exchanger and a method of manufacturing the same are provided. The heat exchanger includes a plurality of walls spaced apart to define a plurality of fluid passageways and a plurality of flow turbulators extending between two adjacent walls through the fluid passageways. The walls and flow turbulators define one or more internal fluid passageways in thermal communication with the plurality of fluid passageways which receive a flow of auxiliary heat exchange fluid for enhancing the heat transfer efficiency of the heat exchanger.