Using Computational Fluid Dynamics
(CFD) for improving cooling system
efficiency for Data centers
Data Centre Best Practises Workshop
17th March 2009
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Data Centre Case Study – Geometrical Details
Introduction to CFD
CFD while designing of HVAC system CFD during installation of Data Centre
• Computational (having to do with mathematics & computation) Fluid Dynamics (the dynamics of things that flow)
• CFD is built upon fundamental physics equations: equations of motion and conservation. CFD applications range from numerical weather
prediction to vehicular aerodynamics design.
• CFD applications are linked with advances in computing software and hardware. CFD software is characterized by the physical models in the software.
• Fine-scale CFD applications closely match the true geometry of the physical objects and processes being modeled.
reactor vessel - prediction of flow separation and residence time effects.
Chemical Processing HVAC Hydraulics
Aerospace
Automotive
Biomedical Power Generation Sports MarineTemperature and natural convection currents in the eye following laser heating.
Aerospace
Automotive
Biomedicine
Flow around cooling towers
Marine
Sports Power Generation
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Data Centre Case Study – Geometrical Details
Introduction to CFD
CFD while designing of HVAC system CFD while installation of Data Centre
Introduction to the Case Study
• Case Study is taken from one of the project that we did for a Data Centre in India
• The case study includes what we did for the client also extends it for what could have been done for the same project using CFD
• There were two software applications used for the project : OpenSource CFD platform of OpenFoam and commercial CFD package of Fluent • Both packages produced about the same results, in this presentation the
Case Description
• The analyzed Data Centre is rectangular with of area 516m2 and height 3.35mt
• Cooling is to be provided using raised flooring layout and demarcation is done for Cold Aisle and Hot Aisle
• The sources of heat gain inside the data centre are listed below:
– Heat gain through exterior walls accounting for thermal resistance of the wall
– Heat gain from Server Racks, 154 Server racks each providing about 8 KW combine to about 1.26 MW
HVAC System Specification
• 10 CRAC units, 1 Standby Specification: – Each CRAC unit of 30,585 CMH
– Cooling capacity of Each Rack is 150 KW – Temperature of supply air is 9.4 o
C
– Return Air opening area (On top surface): 2.23 m2 •Supply Air Diffuser (Cold Aisle) Specifications:
–Dimension of 600mm X 600mm –70% open area
–1 supply diffuser per rack (Total 154)
–Supply air velocity can be controlled using under floor fan
•Return Air Diffuser (Hot Aisle) Specification: –Dimension of 600mm X 600mm
–50% open area
Objective of the Study
•
To maintain recommended temperature by ASHRAE for
Class 1data centre
•
The recommended atmosphere is defined as:
– Temperature of 20oC - 25oC
– Relative humidity of 40% - 55 %
Design Parameters
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Data Centre Case Study – Geometrical Details Introduction to CFD
CFD while designing of HVAC system
CFD while installation of Data Centre
Base Case Design
Isometric View of the Designed Data Centre
Case Study Cont…
COLD AISLE Diffusers HOT AISLE Diffusers
Server Racks CRAC Units
(11 Nos.)
CFD Simulation of Base Case
Temperature Contour
CFD Simulation of Base Case
Temperature Contour
Temperature Contour in Middle Plane
CFD Simulation of Base Case
Temperature Contour
Temperature Contour in Middle Plane
Velocity Vectors in Middle Plane
Conclusion from the base case CFD
1.
The Average temperature on the rack surface at the cold
Aisle side is 15
2.
The temperature at Cold Aisle is varying from 12 to 17
3.
The Average temperature on the rack surface at the Hot
Aisle side is 27
4.
The temperature at Hot Aisle is varying from 18 to 32
5.
The simulation shows that a good number of servers are
experiencing temperature well above and below the
ASHRAE recommended temperature levels
Optimizing number of CRAC units & Supply Air Velocity
1. Maximum heat load : 154 X 8 = 1264 KW (1.26 MW) 2. Heat capacity of each CRAC : 150 KW
3. Minimum number of CRAC required: [8.4] = 9
4. The system was designed with 9 CRAC units and velocity of supply air was adjusted to avoid short circuiting and temperature stratification 5. In this case the velocity of 2.2 m/s is coming out to be higher
6. The simulation was conducted with velocity of 1.6, 1.7, 1.8, 1.9, 2.0 & 2.1 m/s
Temperature Distribution with 9 CRACs & 1.8 m/s
Velocity Vectors with 9 CRACs & 1.8 m/s
Results of improved design CFD
1.
The Average temperature on the rack surface at the cold
Aisle side is 16
2.
The temperature at Cold Aisle is varying from 13 to 17
3.
The Average temperature on the rack surface at the Hot
Aisle side is 23
4.
The temperature at Hot Aisle is varying from 19 to 29
5.
Short circuiting of cold air is reduced to a substantial level,
however still prevalent
6.
The simulation shows that a most of the servers are
Conclusion
•
Using Computational Fluid Dynamics the system was
designed to reduce to 90% of original design, thus bringing
about first cost saving of 10% in the capital cost.
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Data Centre Case Study – Geometrical Details Introduction to CFD
CFD while designing of HVAC system
CFD during installation of Data Centre
Case Description
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The capacity of this data centre of of 42 X 154 = 6,468
Server Blades
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4,000 server blades are to be installed
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1,000 servers are by Dell, 2,000 by IBM & 1000 by Sun
•
The design variables are:
– Number of CRAC units
– Which CRAC unit should be operational
CFD Simulation Setup
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The power requirement of 3000 Server is minimum 713 KW
– 5 CRAC (750KW) are minimum number of units which
can provide the required tonnage
•
The CFD simulation were conducted with various locations
of Servers, CRAC’s and Supply air velocity
•
The best result was found with following parameters:
– Top Racks are empty
CFD Simulation Results
CFD Simulation Results
Temperature Distribution with 5 CRACs & 1.2 m/s
Velocity Vectors in Middle Plane
Calibration during Installation
Temperature Sensors
•
The Result from CFD shall be compared with average
reading shown by temperature and velocity sensors
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Data Centre Case Study – Geometrical Details Introduction to CFD
CFD while designing of HVAC system CFD during installation of Data Centre
