Numerical Investigation of Novel Underfloor Air-Directors Effect on Data Center Performance

Most of the thermal management technologies concentrate on managing airflow to achieve the desired server inlet temperature (supply air operating set point) and not to manage/improve the amount of cool air (CFM) that each computer rack (i.e. IT servers) should receive in order to remove the produced heat. However, airflow is equally important for quantifying adequate cooling to IT equipment, but it is more challenging to obtain a uniform airflow distribution at the inlet of computer racks. Therefore, as a potential option for improving airflow distribution is to eliminate the sources of non-uniformities such as maldistribution of under-floor plenum pressure field caused by vortices. Numerous researchers focus on the adverse effects of under-floor blockages. This study focused to numerically investigate the positive impact of selectively placed obstructions (on-purpose air-directors); referred as partitions; Quantitative and qualitative analysis of underfloor plenum pressure field, perforated tiles airflow rate and racks inlet temperature with and without partitions using two Computational Fluid Dynamics (CFD) models, which were built using Future Facilities 6SigmaRoom CFD tool. First, a simple data center model was used to quantify the partitions benefits for two different systems; Hot Aisle Containment (HAC) compared to an open configuration. Second, the investigation was expanded using a physics-based experimentally validated CFD model of medium size data center (more complicated data center geometry) to compare different types of proposed partitions. Both models results showed that partition type I (partitions height of $\frac{2}{3}$ of plenum depth measured from the subfloor) eliminates the presence of vortices in the under-floor plenum and hence, more uniform pressure differential across the perforated tiles that drives more uniform airflow rates. In addition, the influence of proposed partitions on the rack inlet temperature was reported through a comparison between open versus hot aisle containment. The results showed that the partitions have a minor effect on the rack inlet temperature for the hot aisle containment system. However, the partitions significantly improve the tiles flowrate. On the other hand, for the open system, the presence of partitions has improved the tiles airflow rate, rack inlet temperature and hence eliminate the hot spots formation at computer rack inlet.