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CFD Study of Machine Room Cooling Efficiency at UB CCR

by Jay Patel
by

Jay Patel

on 21 November 2012

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Transcript of CFD Study of Machine Room Cooling Efficiency at UB CCR

CFD Study of Machine Room
Cooling Efficiency at UB CCR Supervisor Student Jay Patel Dr. Matt Jones


Thank you…. Effect of omitting zone 5 + zone 1 Distribution of space into Zones One option is to install variable drive motor on each CRAH (approx. cost is $10k/CRAH). What options do we have to improve Cooling efficiency? Region of Influence for each CRAHs Sub-optimal arrangement of ventilated tiles. Cons of Present condition OPENFoam was used as Numerical Solver for present case. CFD Results of Present Condition






Source: 42U.com Data Center at UB CCR The answer to both is YES, there are various firms who have specialized at doing this in recent years. Is doing this easy and safe? The average pressure in sub floor region is still around 101348 Pa, still above the pressure we have in current condition. CFD Results… The average pressure in sub floor region is decreased to 101350 Pa, but still good enough to cause a flow in above floor. What if we turn OFF one more CRAH? The average pressure in sub floor region is around 101357 Pa, which is higher then current Pressure in sub floor What CFD says? Effect of omitting zone 5 Number of Ventilated tiles = 52 (we can close 13 tiles = 20% reduction in number of tiles). Modified location of Ventilated tiles Number of Ventilated tiles = 65 Present location of Ventilated tiles The main cause of air flow is the pressure difference between sub floor(high pressure) and above floor region. How Cooling is done at UB CCR? Why is cooling necessary at Data Centers? Problem Description In data center at CCR, the optimal way to use existing CRAHs is by isolating the non productive region in sub floor and diverting air where it is most required. Conclusion Source: PlenaForm.com Now the average Pressure in Sub floor is same as what we have in present condition. Lets turn OFF one more CRAH The average pressure in sub floor region was increased by 20 Pa. CFD Results for Modified location Each Rack roughly requires 800-1200 CFM (cubic foot per minute) of cool air. Sources of Heat Generation The pressures obtained by CFD study and the real time values are nearly same, but due to the assumption made in designing the ventilated tiles the pressure by CFD study is 5-7 Pa less then the real value. Pressure and Velocity Distribution CFD (Computational Fluid Dynamics) study was done only for flow in sub floor region at initial phase. CFD Analysis of Present Condition Source: PlenaForm.com Some Examples August 8, 2012 Source: ASHRAE The normal mesh files have 2053066 Nodes points and 1666030 Elements (555MB). The mesh was generated using ANSYS Fluent on a computer having intel i5 processor and 8 GB RAM. It took roughly 5-6 hours to generate a mesh. Majority of Mesh was of Hexahedral elements. Visualization kit used was Paraview. Both are Open source. The case was solved on 48 cores (12 x 4) at U2 using intelMPI. It took 3 hrs for convergence and 5 hrs for rejoining the results from each core(processor) to a single file. Not enough Blanking panels. More air is supplied in the sub floor then needed for cooling in above Racks. Above floor is underutilized (approx. 50% is empty or open space). 6 out of 7 CRAH are ON and cost of running each CRAH is approx. $10,000/y plus maintenance cost. Other option is we can isolate some useless region of sub floor from the main system and switch OFF some more CRAH w/o effecting the cooling (approx. cost is under $10k). By working on later option we can turn OFF around 3-4 CRAH out of 7 and can save $10/CRAH per Year. By doing this we can direct the source of the cold air from the CRAH units to where the air is needed. This will help to maintain the static pressure further away from a CRAH unit due to which there will be a good flow at far ends and we can avoid thermal hot spots. If we try to switch off too many of the 7 CRAHs w/o doing this the pressure in the sub floor region will decrease and it may have an adverse effect on cooling. Also the new arrangement of ventilated tiles will help to achieve higher pressure in sub floor region.
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