Modeling Electronic Cooling Axial Fan Flows

To address the requirement for prediction and understanding of airflow in forced convection cooled electronic systems, a detailed experimental investigation of the outlet flow of typical axial cooling fans has been performed. The flow is shown to be complex over much of the fans operational range, with significant radial and tangential velocities and regions with little or no flow. The effect of partially blocking a fan and running it at elevated temperatures are both shown to be significant. The effect of attaching a fan to an electronic system is then investigated. Flow drawn through a system is shown to be simple and well predicted by a standard CFD package. Flow blown into a system is far more complex, with large areas of recirculating flow, and less accuracy in the prediction. The paper gives valuable and novel design insight into forced cooling flows in electronic systems and shows that the industry is still some way from a reliable design method.