Effect of plenum chamber obstructions on data center performance

Cool air supplied from a raised floor plenum is the most common cooling technique employed in any electronic data center. Many factors lead to the presence of obstructions in the under-floor plenum chamber. However, detailed investigations on the effect of these obstructions on cooling system performance need to be carried out. We have performed CFD studies to quantify the effect of obstruction and perforated tiles on total CRAC (Computer Room Air Conditioning) flow rates as well as the distribution of flow through CRAC. We investigate various factors affecting the air flow distribution and the corresponding cooling with seven models. This paper describes these models and presents key results, compared with experimental data available from the relevant literature. The flow rates through perforated tiles obtained through simulations show good agreement with the measured values for three CFD models. It was observed that obstructions in the plenum chamber lead to decreased air flow rates by as much as 80%, thereby leading to an increase in the occurrence of hot spots. Further, we demonstrate that pipe placement in the plenum chamber is one of the important factors affecting data center performance and hence there is a need to further develop industry standards.