Parametric analysis for thermal characterization of leakage flow in data centers

A model for a basic hot aisle/cold aisle data center configuration was built and analyzed using the commercial computational fluid dynamics (CFD) software FloTHERM. The CFD study was motivated by experimental data that sho wed air recirculatio n from the hot aisle to the cold aisle through the gap between the floor and the bottom of the server cabinet. This flow can be attributed to lower values of the local pressure at the front of the cabinet due to the air stream from the raised-floor perforated tiles. Here this “leakage” flow is modeled to gain better understanding of the characteristics of the undesirable hot fluid recirculation. The parameters and conditions varied in the numerical investigation include: tile perforation area, CRAC provisioning, pressure gradient of the leakage air stream and the effect of cold aisle containment. The impact of the leakage flow on the cooling air supplied to the servers is discussed. The results indicate that the cooling effectiveness in data centers can be reduced due to even a small amount of under-cabinet leakage, although better cooling performance is obtained using a contained cold aisle. The leakage effect is found to be sensitive to under-provisioned conditions. The results of the numerical study can be used to better optimize the cooling performance for contained or uncontained cold aisles when there is under cabinet leakage flow that influences the server inlet air temperature.