Detailed CFD Modelling of EMC Screens for Radio Base Stations: A Parametric Study

The objective of this paper is to make a parametric study of the hydraulic resistance and flow pattern of the flow after an electromagnetic compatibility screen and between two printed circuit boards (PCBs) in a model of a 90deg subrack cooling architecture. The parametric study is carried out using a detailed 3-D model of a PCB slot. The detailed model was experimentally validated in a previous paper by the authors. Seven parameters were investigated: velocity, inlet height, screen porosity, PCB thickness, distance between two PCBs, inlet-screen gap and screen thickness. A correlation for the static and dynamic pressure drop, the percentage of dimensionless wetted area, A_w*, and the RMS* factor (a function of the flow uniformity along the PCB) after the screen is reported as a function of six geometrical dimensionless parameters and the Reynolds number. The correlations, that are based on 174 three dimensional simulations, yield good results for the total pressure drop, in which the values are predicted within the interval of plusmn 15%. For the, A_w*, all the predicted values are within the interval of plusmn22% of the observed values. Finally, for the RMS* factor, the majority of the values also have a disagreement of less than 20% of the observed values. These last two parameters are believed to provide a correct insight about the flow pattern after the screen.