A three dimensional simulation of the flowfields within an intercooler has been performed, which included both the charge and cooling air flow. The simulation intended to demonstrate the application of numerical and computational techniques to heat exchangers with secondary heat transfer surfaces. The intercooler model selected for this work was typical of commercial designs and some experimental data was available.A multiblock grid was developed from CAD data using PROSTAR™ meshing software. The flowfield was then calculated using STAR-CD™ finite volume Computational Fluid Dynamics (CFD) software using one processor of an HP K400 computeserver. In the simulation the intercooler secondary heat transfer surfaces (fins) were replaced by conducting distributed resistance (porous media). The resistance had been calibrated by 2D CFD studies of the fin designs. Comparison of the predicted heat transfer with that measured by experiment revealed that the intercooler thermal performance was predicted to 10% accuracy.