Additive manufactured ducted heat exchanger system

A method of manufacturing a heat exchanger for location within a duct in a nacelle for a gas turbine engine, an inlet to the nacelle and an exit from the nacelle for communication of an airflow through the duct comprising:

• additively manufacturing an external geometry of a core of the heat exchanger to fit within the duct;
• additively manufacturing an internal geometry of the additive manufactured heat exchanger core such that at least one of a multiple of flow passages is varied with respect to a distance along the length of the at least one of the multiple of flow passages;
• additively manufacturing a front face of the core transverse to the duct and contoured with respect to a non-uniform flow distribution of the airflow that enters the core perpendicular to the front face over the entirety of the front face;
• and
• additively manufacturing a rear face of the core transverse to the duct and contoured with respect to the non-uniform flow distribution of the airflow that exits the core perpendicular to said rear face over the entirety of said rear face, the rear face of said core downstream of the front face within the duct along an entire central longitudinal axis and wherein a width of the core measured along the central longitudinal axis from the front face to the rear face is varied along a radial direction.