www . refrigerationandaircon . co . za RACA Journal I September 2024 19
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• Convenient services placement : One primary benefit is the ability to place services , such as cabling and electrical wiring , underneath the raised floor . This arrangement helps in organising and managing infrastructure components effectively .
• Airflow management : Raised floors facilitate airflow management by allowing adjustments with floor tiles . This capability is crucial for directing airflow to specific areas where cooling is needed most , thereby optimising cooling efficiency within the data centre .
• Flexibility in configuration : Data centres with raised floors can adapt their layout more flexibly over time . Changes in equipment placement or operational requirements can be accommodated by moving or reconfiguring floor tiles .
However , raised floors also come with their own set of challenges and limitations :
• Air volume considerations : A significant drawback is the potential for air to accumulate underneath the raised floor , especially if not managed properly . This can lead to warmer air circulating within the data centre room , affecting overall cooling efficiency .
• Blockages and restrictions : Installing equipment or making modifications under the raised floor can inadvertently block airflow paths to IT racks . This obstruction can create uneven airflow distribution , resulting in higher pressure zones and potentially compromising cooling effectiveness .
• Scaling challenges : As data centres scale up in size and power density ( reaching capacities of several megawatts ), the limitations of raised floors become more pronounced . There is a practical limit to how much air can be effectively circulated through the narrow spaces beneath the floor , which can restrict the overall cooling capacity and efficiency .
Given these considerations , the industry has seen a shift away from raised floors in larger , more modern data centres . Alternative cooling arrangements , such as overhead cooling systems or in-row cooling units , are becoming more prevalent . These systems offer more direct and efficient airflow management without the spatial constraints and airflow challenges associated with raised floors .
Q & A : INSIGHTS ON HIGH-DENSITY RACKS , PUE IMPROVEMENT , AND LIQUID VS DX COOLING There followed a Q & A session , in which the following opinions were offered :
The conversation delved deeper into the implications of high-density racks , their impact on PUE ( Power Usage Effectiveness ), and considerations between liquid cooling and DX ( Direct Expansion ) cooling technologies in data centres . Transitioning from lower to higher heat densities per rack affects PUE in nuanced ways . While higher densities typically
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1 . Michael Young , application engineer ( thermal ): Vertiv . 2 . Last Shadaya , senior mechanical engineer : Systemair .
require more energy to cool due to increased fan power and potentially higher operational temperatures , efficient airflow management and advanced cooling technologies can mitigate these challenges . Efficient cooling hinges on effectively moving heat with minimal energy input . This efficiency is influenced by location-specific factors like ambient temperatures , which affect the viability of free cooling systems . Therefore , the effectiveness of PUE improvements with high-density racks depends on the technology used and the operational conditions of the data centre .
Comparison between liquid and DX cooling : Liquid cooling offers significant efficiency advantages over traditional air cooling . Water ' s higher heat capacity and thermal conductivity make it more effective at dissipating heat compared to air . This efficiency is particularly beneficial in high-density environments where precise heat management is crucial . Despite its advantages , liquid cooling poses challenges such as power requirements for pumps and potential risks like leakages . The decision between liquid and DX cooling hinges on factors like site capacity , maintenance feasibility , and initial investment costs .
The move towards liquid cooling from air cooling generally promises greater efficiency due to water ' s superior thermal properties . However , the decision must consider various factors including site capacity , operational costs , and environmental conditions . High-density racks challenge data centre operators to optimise airflow and cooling strategies effectively to enhance PUE and overall operational efficiency . RACA
“ With projections of data centres growth indicate a potential doubling of this consumption to 4 % in the near future , the urgency to innovate and optimise cooling solutions becomes increasingly clear .”
www . refrigerationandaircon . co . za RACA Journal I September 2024 19