Adequate data center rack cooling with the highest possible energy efficiency is one of the most critical aspects of DCIM. It is crucial to ensure sufficient mixing in the cold aisle, which is mainly depending on the supply flow rate and temperature. This presentation was used in a free webinar hosted by SimScale, a cloud-based simulation platform. Watch the recording below to learn how computational fluid dynamics simulations can help you reduce the cooling cost of an existing data center by optimizing the supply air temperature and the supply air flow rate, based on the CFD results and cost functions. - Webinar recording: https://www.simscale.com/webinars-workshops/reduce-cooling-cost-data-centers/ - Blog article: https://www.simscale.com/blog/2018/05/data-center-power-consumption/ - Simulation project template: https://www.simscale.com/projects/vaibhav_s/data_center_cooling_rci_1/

1. Energy Efficiency and Cooling Cost
Reduction in Data Centers With CFD
Dr. Pawel Sosnowski

2. Pawel Sosnowski, PhD
Customer Success Engineer
Pawel holds a Ph.D. in Environmental and
Industrial Fluid Mechanics and a M.Sc. in
Technical Physics. His expertise includes CFD,
numerical analysis, customer relations
management, 3D printing, and software
development.

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10. ELECTRONICSA E C ENERGY AUTOMOTIVE AEROSPACE
HEALTHCARE MACHINERY MARINE CONSUMER
GOODS
VALVES &
PUMPS

11. Watch the workshop recording

12. Energy Efficiency and Cooling Cost Reduction in Data Centers with CFD
How to REDUCE THE COOLING
COST of DATA CENTERS with CFD

13. Energy Consumption
● 2000 - 2005: 90% increase
● 2005 - 2010: 40 % increase
● Current Trends:
○ Limit to 1.5 % increase
○ Save 620 Billion kWh
The Importance of Energy Consumption is Rising
[1] Source: U.S. Department of Energy, Lawrence Berkeley National Laboratory
http://www.expansionsolutionsmagazine.com/industry_articles/view/12081/the_data_center_revolution____who_are_gordon_moore_and_robert_dennard__and_what_do_they_mean_to_me__

14. Energy Distribution in a Data Center
Image Source [1]: http://ieeexplore.ieee.org/document/7279063/
Image Source [2]: http://dptgroup.com/event/thermal-power-il/

15. High Power Density Data Center
Server Racks (4 KW Each)
CRACs Return Outlet
CRACs Supply Inlet
Cold Aisle
Containments
Raised Floor
Plenum
Raised Floor Cold-Aisle Containment Layout

16. High Power Density Data Center
COLD
AISLE
COLD
AISLE
HOT AISLE
C
R
A
C
C
R
A
C
C
R
A
C
HOT AISLE
HOT AISLE
C
R
A
C
Perforated Tiles (modeled using porous media)
Raised Floor Cold-Aisle Containment Layout

17. High Power Density Data Center
Cross-section view of layout showing flow physics
Raised Floor Cold-Aisle Containment Layout
Front GrillServers Heat
Source
Fan Momentum
Source
Rear Grill Perforated
Tiles

18. Design Constraints & Parameters
CONSTRAINTS
● 208 KW Total Space Load
● 140 m2 Data Center
● Server Intake Temperature
PARAMETERS
● Supply Temperature
● Supply Flow Rate
● Rack Cooling Effectiveness
(RCI)
● Cooling Cost Function

19. Rack Cooling Index (RCI) – Measure of Cooling Effectiveness
ASHRAE Standards – “The recommended equipment intake temperature range is 20-25°C and the allowable range is 15-
32°C.”
(Reference: Herrlin, M. and Khankari, K. Methods for Optimizing Equipment Cooling Effectiveness and HVAC Cooling Costs in
Telecom and Data Centers. ASHRAE Transactions, Volume 114, Part 1)
“RCIHI is a measure of the equipment health at the high end of the temperature
range. Over-temperature conditions exist when one or more equipment intake
temperatures exceed the max recommended temperature.”
“The RCILO is a complement to RCIHI especially when the supply condition is
below the minimum recommended temperature.”

20. Flow Parameter Variation for Cooling Index
A total of 16 cases analyzed

21. Watch the workshop recording

23. Servers Intake Temperatures
Row 1
Row 2
Row 3
Row 4

24. Average Servers Intake Temperatures

25. Servers Temperatures at Rack Midplane (Row 1 & Row 2)

26. Servers Temperatures at Rack Midplane (Row 3 & Row 4)

27. Velocity at 1m Height

28. Temperature at 1m Height

29. Velocity Contours at Grill Section

30. Temperature Contours at Grill Section

31. Pressure Drop at Perforated Plates & Grills

32. Cost Function – A Trade-off between Supply Temperature & Supply Flow Rate
Cost Function Definition: Energy costs for conditioning are associated with chiller and fan energy
consumption.
1. Increase in supply air temperature is linearly proportional to higher chiller Coefficient of Performance
(COP).
2. Increase in supply airflow rate demands more fan energy to circulate air between the air-handler and
data center.

33. Cost & Energy Savings
RCI criteria: With both RCIHI and RCILO ≥ 95 and energy savings of 11% (at 21°C, 120 % supply
configuration) is a true win-win situation in accordance with ASHRAE Standards.

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1 2 3

35. Read this blog article to learn more