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As easy as CFD


As data centre cost-efficiency and environmental performance come under intense scrutiny, Computational Fluid Dynamics (CFD) plays a major role in ensuring facility optimisation, says Gordon Johnson, senior CFD manager at Subzero Engineering.

Since 2015, we’ve kept track of the various savings we have achieved for our customers through the careful, considered optimisation of their data centre environments.

The numbers are impressive: our customers have saved just under 3.5 billion kilowatt hours, reduced water consumption by one and a half billion gallons and have a total carbon reduction of over 3.2 million tonnes – the equivalent of planting 17 million trees.

Along the way, we’ve also been able to help customers achieve up to a 29% energy cost reduction, and been able to reduce PUE (Power Usage Effectiveness) by an average of 0.4 and WUE (Water Usage Effectiveness) by an average of 0.3.

Much of this success has been due to the strategic importance we place on carrying out an Environmental Impact Evaluation during the initial customer engagement process which consists of a complementary CFD. 

This evaluation is designed to provide recommendations for improving efficiency and includes solution cost analysis (annual £ energy savings and ROI with containment).

We believe that the CFD is essentially an MRI of the data centre.

When it comes to informed decision-making, the mantra ‘if you can’t measure it, you can’t manage it’ still holds strong. However, in the case of CFD, ‘if you can’t measure it, you can’t improve it’ may be more appropriate.

Turning customer pain into gain

The current and growing industry focus on sustainability has highlighted the need to work towards energy efficient data centre designs, which, in turn, should provide the perfect combination of sustainable operating conditions. The end result being truly optimised data centre performance.

CFD plays a vital role when it comes to data centre construction, retrofit, and helping improve the efficiency and performance of legacy data centres. It allows the owner or operator to simulate endless combinations of racks, cabinets, cabling, and mechanical and engineering (M&E) equipment for greater optimisation.

The owners and operators of these facilities may not be aware that they are literally blowing a lot of (unnecessary) cold air into the aisles in order to keep the servers, switches, routers, and the storage units cool.

What they will know, however, is that this wasted air is wasted money. Worse still, emissions will be increased, hot spots will remain an issue, and they will eventually experience equipment failures.

Many data centre managers know that something has to change to overcome this unsustainable situation, but they may not have a plan or strategy. This is where CFD is critical.

What is a CFD?

CFD software creates a 3D model of the physical attributes within a data centre, as well as the location and performance characteristics of the cooling units, IT equipment, power systems, and other significant components of the data centre.

This ‘data centre MRI’ provides a complete, detailed thermal understanding of the data centre, providing insight relating to the physical layout of the space and equipment; the power equipment thermal dissipation and rack power density; environmental conditions; cooling capacity and air distribution effectiveness. This is the baseline model or the ‘as is’ snapshot of how the data centre is currently operating.

From the information obtained, additional CFD modelling will recommend how to optimise the operating environment while reducing energy and maximising efficiency. 

Many key benefits of CFD analysis include assessment of the data centre layout and its performance; validation of proposed design changes, considerations for efficiency and reliability; accurate prediction/simulation of the cooling design process; the ability to assess temperature and airflow modelling; and reconditions for a cost-effective and energy efficient design.

CFD provides clarity

A data centre CFD analysis provides the visibility that is essential when it comes to understanding both your existing operating environment and any potential design changes.

CFDs can also be used to test out ‘what if’ scenarios when it comes to new data centre construction or modernisation projects.

In essence, a CFD provides detailed, data-driven analysis of the cold supply air and the hot exhaust air throughout the data centre, and the identifies of potential overheating of IT equipment ‘hot spots.’

Such analysis highlights the way in which energy costs can be reduced by optimising and maximising data centre cooling.

CFDs are a tool to virtually test legacy (and new) data centre environments for active temperature, pressure and airflow, and to optimise the mechanical system directly to server heat loads (kW).

Armed with data from the CFD analysis, Subzero Engineering can advise customers on impactful data centre design changes, upgrades, or tweaks to improve operating improvements – all of which will help optimise and reduce energy usage.

For example, CFD modelling can demonstrate what impact a cold aisle containment (CAC) system will have versus a hot aisle containment (HAC) system. It will advise which method will save more energy, full or partial containment.

After containment is installed, it will show if computer room air conditioning (CRAC) units can be turned off and how low fan speeds can be reduced on computer room air handlers (CRAHs).

Finally, it will also inform the user on how high the operating temperature can be increased, while following the recommended thermal guidelines from AHSRAE.

The end result is that CFD based design improvements will provide customers with significant PUE, WUE, KW, kWh, carbon, and water reductions.

A logical conclusion

One of the major benefits of using CFD modelling and analysis is that it can quickly demonstrate how a containment solution will immediately reduce a data centre’s energy cost and lower its environmental footprint.

Regardless of which type of containment is used, large energy savings can be achieved by optimising the airflow and raising the supply temperature, while simultaneously eliminating hotspots.

Additionally, containment improves the benefits and economic feasibility of other efficiency measures, such as digital scroll compressors, electronic commutation (EC) and variable speed drives, data centre infrastructure management (DCIM) software, and building controls.

Further, by separating the cold supply air from the hot exhaust air, containment saves energy, thus reducing operating costs.

Yes, there is the initial investment cost of installing the containment solution, but the potential return on investment (ROI) of 10-14 months means that, very quickly, end-users will achieve payback.

What’s more, from that point onwards, they’ll be saving energy, reducing operating expenditure (OpEX) money, and reducing carbon emissions to become more sustainable.

Subzero believes that a data-driven approach to digital infrastructure is essential and thanks to the use of CFD, we can simultaneously help our customers increase data centre density, operating efficiency, and environmental sustainability by implementing optimised containment solutions.

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