There have been various studies into the importance of sealing cable openings within the raised floor to reduce bypass airflow, along with studies into sealing gaps in IT racks to prevent hot air recirculation.

But what about sealing gaps under IT racks?

Now Upsite Technologies has produced a technical report into an area that is often overlooked, the small gap between the base of the rack and the raised floor or slab. The technical report entitled “Sealing Gaps Under IT Racks: CFD Analysis Reveals Significant Savings Potential” by Lars Strong & Bruce Long uses CFD analysis to see the impact this gap has on inlet temperatures.

Due to many IT racks being on levelling feet or castors there is often a gap under the IT rack that can range from 12mm to 50mm or more. This gap however allows the hot exhaust air from the rear of the IT equipment to flow underneath the rack and back into the equipment air inlets at the front. This recirculation of hot exhaust air increases the inlet air temperatures, contributes to hot spots and can ultimately lead to increased failure rates of the IT equipment. The technical report examined the impact sealing these small gaps under the IT racks would have.

Background of the test
Using CFD analysis two models were compared: A model with 1.5” (38mm) gaps under the racks, and a model where the racks were fitted with AisleLok Under Rack Panels to seal the gaps. Each model was based on an aisle with 48 racks, where cable openings were sealed with KoldLok floor grommets, and unused rack space and gaps between the top, bottom and side rails were sealed with HotLok blanking panels and HotLok Rack Airflow Management (RAM) kit respectively. Each row of racks were also fitted with AisleLok Modular Containment Rack Top Baffles and AisleLok Modular Containment Bi-Directional Doors. The cooling units delivered the conditioned air at 62°F (16.7°C) with each rack averaging 4.5Kw loads and a total IT load of 217kW.

Result Comparison
The test used CFD modelling and infrared imaging to examine the impact of sealing the gaps under the IT racks would have. The images below show the results.

Before sealing the gap
Before the gap was sealed the image below shows the variation in inlet air temperature for the installed equipment. The dark grey areas are where unused rack space has been blanked off with HotLok blanking panels. The maximum equipment inlet temperature was 86.4°F (30.2°C)

Before sealing under rack gaps

After sealing the gap
The image below shows the dramatic improvement in air inlet temperatures across the same row after the installation of the AisleLok Under Rack Panels. With the Under Rack Panels installed the maximum inlet air temperature was 75°F (23.9°C) a reduction of 11.4°F (6.3°C).

After sealing under rack gaps

Conclusion
The technical report concluded that sealing the gaps under IT racks can dramatically reduce the inlet air temperature to the installed IT equipment. The installation of an AisleLok Under Rack Panel to each rack not only improves the IT intake air temperatures, but also creates the opportunity to reduce cooling costs and release stranded capacity.

To read the Technical Report in full please request the report via our contact page.