Design and verification of a partial recirculation cooling scheme for a telecoms shelf

Flow Network Models were used to design an innovative cooling system for a telecoms shelf which uses the partial recirculation of air to increase air velocities over the circuit cards. The paper is divided into two parts. The first part of the paper outlines the design of the recirculation cooling system, an outline of the design objectives, and a description of the Flow Network Model used. The second part of the paper outlines the measurements of the flow within the shelf. Flow measurements were performed with an Airflow Test Chamber (obstruction type flow meter) to measure bulk flow from which average slot velocities were calculated. These results are compared with the original Flow Network Model simulation results. Comparison of the measured and modeled data shows that there is a very close agreement in bulk flow prediction except for the recirculation bulk flow rate, and that difference was due to a much higher than anticipated density of power cables routed across the recirculation duct.