Clive Collins of Envis-Eco says that intelligent strategies are needed to cool air in the data centre

Growing awareness and concern over rising I.T. energy usage is leading governments, vendors and users to look increasingly at strategies to tackle the issue.

I.T. energy consumption is expected to increase by nearly 15% between now and 2020, but the greatest concern lies within the data centre, where energy usage is predicted to more than double in the same time period.

To this end it is clear that optimising energy efficiencies in respect of cooling capacity and performance will be a major component of any ‘green’ strategy within the data centre.

Data Centre Cooling
It is generally agreed that a significant amount (in excess of 60%) of available conditioned air in a typical UK data centre is wasted i.e. it does not hit the heat load. Understanding airflow and managing it correctly is a vital requirement in addressing this situation and thereby realizing significant energy and performance efficiencies.

Efficient airflow management is the process of distributing 100% of the available conditioned air directly to the heat load without using any additional energy or power – and can result in energy cost savings of 18 to 27% when doing so in existing environments.

The lack of proper air flow management leads to reduced cooling capacity and efficiency and can have damaging effects such as higher than necessary energy costs, hotspots and server downtime/failure.

One of the largest problems within today’s data centres is the ability to deliver as much cold air as possible to the heat load, in an attempt to cool front to back or cold aisle/hot aisle cooling. 

There are many companies that have studied this problem and have attempted to bring something to market to help solve this issue.

An initial approach identified that cable openings were leaking excess cool air and by blocking the openings it would add additional pressure to the sub-floor, which in turn would force more cool air to flow through the vented tiles, allowing for greater cooling capacity. The consequent brush type solution was a great step forward towards better air distribution to the heat load.

Despite these advances there were still many problems with cooling and the ability to effectively distribute all of the cool air that was being generated by the CRAC units to the heat load.

A major problem, in simple terms, is that the air under the sub-floor can travel at many different velocities, causing many different pressures to occur at different locations. The by-product of these varying pressures is low flowing vented tiles in some areas, negative flowing tiles in other areas and the general overall inability to balance and optimise the air flow cooling power within a data centre.

The general solution for many years has been to add more CRAC units and plug the unmanaged openings. Through testing and CFD modeling tools it was discovered that, in many cases, when additional CRAC units were added, it actually caused the vented tile cool air flow rate to reduce, due to the increased air speed that was now being added to the sub-floor.

A new approach
Through studies we discovered that, by slowing down the sub-floor air speed, we can dramatically increase the static pressure, which in turn improves the cool air flow rate through the vented tiles, providing greater cooling capacity to the room. From this new discovery we developed a unique sub-floor system enabling us to design and build in the ability to slow down the sub-floor air within any data center, by using our strategically placed air pressurisers.

Now that we have slowed down the sub-floor air we found that the static floor pressure increased dramatically, so much so that the initial testing of the brush style floor grommets showed increased leakage, regardless of the cabling size. As a matter of fact the larger the cable bundle the greater the leakage. This new discovery forced us to engineer a new airlok that could withstand the increased sub-floor pressure whilst providing a better seal, regardless of the cable bundle size.

Additionally, it was found that by providing this increase in static pressure and coupling it with the correct placement of perforated tiles (as well as the correct percentage opening tile) it is possible to deliver most of the available conditioned air to the heat load.

Finally the inclusion of blanking panels to eliminate the by-pass airflow, caused by partially populated server cabinets, has seen us achieve up to additional reductions in cooling costs by eliminating the return of cooler air to the CRAC units.

By implementing these changes we create a better segregation of hot and cold air delivering reduced energy consumption and an increase in cooling capacity.

In summary what we provide is the following:

An initial CFD analysis to determine air flow patterns throughout the data centre and determine the requirements necessary to achieve greater cooling efficiencies.

• The design and implementation of the solution - that includes the provision and (most importantly) placement of air pressurisers, airloks and blanking panels)
• Ongoing CFD analysis as the data centre population changes.

The operational benefits include

• Reduction in cold aisle temperatures
• 95% +/- of the available conditioned air moved directly to the heat load
• The elimination of all hotspots
• Optimum balancing of the sub-floor pressure
• Increased ability to scale and support more equipment
• More efficient cooling of electronic equipment resulting in lower maintenance costs

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