In CFD analyses carried out for data centers, just as cabinet layout is considered during the pre-design phase, the level of underfloor congestion in rooms operating with raised floor systems must also be taken into account.
Because one of the main factors that negatively affects the effectiveness of the air reaching the cold aisle is the level of underfloor occupancy.
▬ In white spaces supplied through a raised floor plenum, we often realize during commissioning that the equipment located under the floor (UPS modules, cable trays, piping, patch panels, etc.) significantly alters the flow characteristics.
▬ As seen in our analysis, the density of the underfloor completely affects the airflow distribution both in the cold aisle and within the plenum.💵
▬ The underfloor space cannot, of course, be left empty, but its distribution can be optimized to prevent potential issues in the future.
The underfloor void ideally acts as a homogeneous pressure plenum. However:
As the obstacle density within the plenum increases, the effective flow area decreases
Local turbulence and vortex regions form
Static pressure distribution becomes heterogeneous
Air supplied by CRAC/CRAH units cannot reach distant points with sufficient airflow rate
As a result:
↓ High velocity at the beginning of the cold aisle, reduced velocity at the end – 20–40% effective area loss
↓ Failure to achieve the expected airflow beneath perforated tiles and dampers – additional pressure loss
↓ Increase in rack inlet temperatures
With CFD analyses:
↑ Impact of underfloor equipment layout on pressure distribution
↑ Optimization of grille–damper configurations
↑ CRAC/CRAH positioning scenarios
↑ Rack inlet temperature maps
In data center projects, CFD should not be considered merely as a validation tool,
but as an optimization platform that guides mechanical design decisions.
In this way, “trial and error” is not left to the field…
