Steady Reynolds-Averaged Navier-Stokes (RANS) simulations utilizing the k-ω SST turbulence model are conducted to investigate the aerodynamic performance of a wing-integrated ram-air duct housing a heat exchanger for propeller-driven aircraft, including its impact on wing-body junction flow. The research is conducted in two stages: first, a 2D aerodynamic analysis employing a Design of Experiment (DoE) methodology to assess the sensitivity of key geometrical parameters–including stagger angle, leading-edge droop, duct gap, and heat exchanger characteristics–on lift, drag, and duct mass flow rate; and second, a 3D investigation of the junction flow behavior in the nacelle/ducted-wing configuration. The heat exchanger pressure drop is modeled as a porous media zone using the Darcy-Forchheimer quadratic drag law. Heat transfer is incorporated through a variable energy source term applied via a userdefined function (UDF) based on the ε-NTU correlation. Findings from the 2D aerodynamic analysis indicate that heat exchanger characteristics, particularly porosity and thickness, have a more pronounced impact on aerodynamic performance than external duct geometry. However, intake stagger angle and leading-edge droop play critical roles in mitigating flow separation and optimizing the wing pressure distribution. In addition, the redistribution of pressure due to flow restriction alters the stagnation point location, inlet-velocity ratio, and static pressure distributions, all of which influence the aerodynamic loading of the ducted wing. The optimal ducted airfoil configuration, featuring a lower-surface outlet aft of the maximum thickness and a thin heat exchanger, minimizes aerodynamic penalties while maximizing duct mass flow rate. However, thermal feasibility assessments reveal that meeting the cooling demands of fuelcell systems necessitates a thicker heat exchanger to accommodate sufficient heat transfer area within the constrained wing volume. This increase in thickness impairs aerodynamic performance through increased pressure drop and resultant drag. Although higher porosity mitigates flow resistance, the required thickness offsets this advantage, reinforcing the inherent trade-off between aero-thermal performance. In 3D, the presence of the heat exchanger inside the duct fundamentally alters the local aerodynamics by modifying boundary layer interactions at the wing-body junction. The flow resistance imposed by the heat exchanger directly affects the strength and topology of secondary flow structures, particularly the horseshoe vortex (HSV), which governs junction flow behavior and whose strength scales with the Reynolds number based on the momentum thickness of the incoming boundary layer. At low porosity levels, the stronger HSV , with an increased vertical extent above the wing, entrains high-momentum freestream flow into the chordwise and spanwise boundary layers, mitigating corner flow separation. Conversely, at high porosity levels, lower flow resistance alters HSV topology, reducing its vertical extent and allowing part of the vortex to enter the duct, inducing a secondary vortex at the lower lip. This weakens the HSV’s ability to stabilize the boundary layer, leading to earlier separation, increased pressure losses, and higher drag. A moderate porosity level provides an optimal balance between HSV strength, vertical positioning, and junction flow stability, reducing corner flow separation and associated pressure losses. Collectively, these findings yield critical insights into integrating ram-air cooling ducts within the wings of propeller-driven aircraft, offering a compelling approach to achieving efficient thermal management systems with minimal aerodynamic penalty. This investigation provides unprecedented detail in visualizing and understanding the intricate coupling between ducted wing aerodynamics and heat exchanger-induced flow interactions, while emphasizing the need for further research to validate and expand upon these findings