The objective of this paper is to perform an experimental as well as CFD investigations of the conjugate heat transfer problem in a sub-rack slot model. A steady-state three-dimensional detailed model, which serves as the most accurate representation of the model, was used in order to evaluate the details of the airflow paths and temperature field. A general model that covers a considerable range of velocities, screen porosities and heat fluxes was validated experimentally by wind tunnel measurements. The result shows that the RNG k-ε model used with correct y+ and mesh strategy accurately predicts the temperature field. The average temperature deviation at several locations is less than 4% compared to experimental data. The influence of the velocity, screen porosity, heat flux and presence of the EMC screen on the PCB temperature field is commented. © 2007 R.T. Edwards, Inc.