DATA CENTRE COOLING
Increasingly, we are fi nding that data centre operators with multiple sites are moving towards integrated off -site- manufactured plantrooms, which can replicate the same cooling systems at each site. This speeds the introduction and expansion of new facilities in this highly competitive industry sector, and assists with day-to-day operation. Scalability: With proper forecasting, plant capacity will help
Armstrong build these repeatable designs in a scalable fashion as the Data Centre expands. A global footprint also helps as it ensures similar systems and exposes potentially extra capacity. Demand-based control: As data centre cooling systems need to be reliable and effi cient over wider ranges of operating conditions as the site expands, it is crucial that system components and control technologies are designed for variable demand and ultra-effi cient performance at part-load. This requires variable-speed components, such as chillers, pumps and fans, across the system, and a control strategy specifi c to the particular operating characteristics of variable- speed devices. There are no exceptions to this, because constant-speed devices cannot solve the challenges of a varying application, such as data centre cooling. When a variable frequency drive (VFD) is added to a
compressor, pump or fan to improve part-load effi ciency, the energy saving potential is huge due to the pump fan laws, which state that power is proportional to rotary speed cubed (PαN3). This would equate to a potential 400% increase in operating effi ciencies. This is only possible, however, if the pump fan law relationship between pressure and rotary speed, along the Natural Curve, is maintained at the decreased speed. Traditional control practices often fail to optimise this potential. Pumps, for example, are often set to maintain a fi xed or minimum diff erential pressure across the pump supply and return headers (see Figure 1). This means the pump will not have the freedom to operate along its Natural Curve and will consume more energy. Best practice is to utilise advanced integrated control across the system. In the case of variable speed chillers, integrated control ensures operation along the chiller’s Natural Curve for all operating scenarios, ensuring optimum effi ciency at all loads. Another important design principle is the employment of capacity-based (rather than demand-based) sequencing. With capacity-based sequencing, each pump would be taken up to 90% loading, for example, before the next pump was introduced. Demand-based sequencing, however, balances the load across the system as a whole, unlocking additional energy effi ciencies which might otherwise remain under- exploited.
Active performance management Advanced connectivity and visibility of system performance are also important throughout the lifetime of ultra-effi cient critical cooling systems for data centres. Without information on fl uid fl ow, across the system, it’s diffi cult to diagnose and optimise effi ciency. With accurate fl ow information, the picture changes entirely. The Active Performance Management developed by Armstrong Fluid Technology, for example, helps to optimise HVAC systems at any stage of a data centre’s life-
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Energy Performance Implications of Parallel Pump Staging Strategy
1P Eff. 2P Eff. ♦ ♦ 3P Eff. ♦ 4P Eff.
PSPC CONTROL CURVE
4 PUMPS 3 PUMPS 1 PUMP 2 PUMPS
♦ - Efficiency-based staging points - Efficiency Curve (RHS)
- PSPC Building and Control Curve Figure 2 Armstrong Fluid Technology Summit 2016 FLOW
cycle, responding to changing cooling requirements. Online trending and analysis across multiple parameters on single pumps, or on an aggregated basis for multiple pumps, assists in identifying performance degradation and facilitates a predictive and proactive approach. It can, for example, report issues such as excessive vibration, pump in hand, risk of cavitation or a dead head should they start to occur. To conclude, whilst data centres may utilise the same
HVAC technologies developed for sites such as offi ce blocks, hospitals and sports arenas, the specifi c commercial pressures of this sector necessitate diff erent approaches. By aligning incremental expansion of the cooling system with the industry’s business models, those supplying critical cooling systems can deliver signifi cant fi nancial and environmental benefi ts.
"The
traditional approach is to create a cooling system capable of supplying 100% of
demand from the outset."
www.acr-news.com • November 2025 21
HEAD
EFFICIENCY
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