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Electronic Cooling Solutions Inc.

• Thermal management consulting company

• Located in the heart of Silicon Valley

• Provide solutions for thermal design problems

• Use of experience, modeling & experimental methods in the design process

• Clients include over 60 companies

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Outline

• Introduction

• Need for Innovative Cooling Solutions

• Objective

• Scope of this Presentation

• Cooling Solutions – Air-based Cooling Systems

– Water-based Cooling Systems

– Refrigerant-based Cooling Systems

• Comparative Analysis

• Conclusion

• Vendor Contacts

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Introduction - Power Density and Heat Load Trends• Electrical Power = Waste Heat

• Increase in power densities from the CPU-level to the System-level

Component level

Board-level System-level Rack-level Room-level

• Current power density at the rack level = 1 to 3 kilowatts (up to 30 kilowatts per rack in two to four years - Hannemann and Chu ‘07)

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Need for Innovative Cooling Solutions at Rack-Level• Datacenter TCO is characterized on a per rack basis

• Addition of newer and higher powered equipment in existing datacenters

• Hotspots in datacenter resulting from high-density servers

• Hotspots resulting from unavailability of cooling air from CRAC units

• Design shortcomings within the rack result in inefficient cooling

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Objective

• Cooling of equipment in rack using airflow and impact of minor design changes for better cooling

• Cooling of high density equipment using water-based cooling techniques

• Cooling of high density equipment using refrigeration-based cooling techniques

• Provide vendor data for the above mentioned products

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Scope of this Presentation

• Limited to discussion of cooling solutions only at the rack level

• Closed racks and commercially available products

• Discussion on Component-level, Board-level and Room-level cooling can be personally consulted

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Airflow-based Cooling Techniques

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Cooling of Racks with Conditioned Air

• Most easy to implement and maintain

• Limitation based on cooling capacity, acoustics and power consumption

• Detailed analysis could improve efficiency of air cooling

Application of Computational Fluid Dynamics (CFD)• Pressure drops and airflow patterns

• Determine by-pass air

• Determine areas of re-circulation

• Determine failure modes of cabinet fans

• Requires testing to develop confidence in models

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Cooling of Racks with Conditioned Air

Airflow Enhancement in Racks

• Based on CFD Analysis

• Sample case study 1

• Sample case study 2

• Cabinet powered fans – airflow layouts

• Best practices

• Airflow enhancing products

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Sample Case Study 1

• Study done by Electronic Cooling Solutions Inc.,

• 42U Cabinet fitted with twenty one 2U units

• 15.75 kilowatts per rack

• Inlet temperature of 40 deg C

• Airflow – 1932 CFM

• 10,000 ft Altitude Conditions

• Simplified cabinet shown here

• Objective was to optimize the cabinet for better cooling/use of higher powered equipment

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Sample Case Study 1 (Contd …)

Inlet Temperature

Higher temperatures at the inlet sides

Re-circulation of Flow

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Sample Case Study 1 (Contd …)• Added vertical blockages

Vertical blockages between the rack rails and cabinet sides

Open space between the rack rails and cabinet sides

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Sample Case Study 1 (Contd …)

• Added blockage above the topmost unit of the rack

Area above the topmost 2U rack is

blocked

Top of 2U server

Top of rack cover meant for passing

cables from front to rear

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Sample Case Study 1 (Contd …)

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Sample Case Study 1 (Contd …)

Comparison of Inlet

Temperatures

No blockages Blocked passages

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Sample Case Study 1 (Contd …)

Fixed Exhaust Temperature (deg C) 55 60

 No

BlockagesWith

BlockagesNo

BlockagesWith

Blockages

Mean Inlet Temperature (deg C) 43.9 41.2 43.9 41.2

Fixed Airflow 92 CFM

Power (W) per unit 397 493 575 675

Total power of Rack (kW) 8.3 10.3 12.1 14.1• Current study shows 17 to 25 % increase in power dissipation based on exhaust temperature.

• By blocking re-circulating flow, it is possible to use higher powered equipment in the rack.

• Blocking can be done by employing Brush Strips.

• Avoid using larger racks with rails set to lower rack width settings (Using 23” rack with rails set to hold 19” equipment)

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Sample Case Study 2

• Study done by Electronic Cooling Solutions Inc.,

• Racks placed in containers

• Create airflow model of blowers

• Evaluate alternate designs for blower module

Symmetry Walls

Container wall

Heat Exchanger

2U Servers

2U Servers

Blower Module

Rack Model

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Sample Case Study 2

• Apprx 20% increase in airflow with the re-designed baffles and perforated casing

Module 1 – 860 CFM

Testing

Testing to collect data for modeling

Module 2 – 1024 CFM

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Cooling of Racks with Conditioned Air

Airflow Enhancement in Racks

• Based on CFD Analysis

• Sample case study 1

• Sample case study 2

• Cabinet powered fans – airflow layouts

• Best practices

• Airflow enhancing products

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Airflow Enhancers – Cabinet Powered Fans

Supply Air

Raised Floor

Front In – Rear Out

Supply Air

Ceiling

Raised Floor

Front In – Top Out

Front or Footprint Inlet

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Airflow Enhancers (Cabinet Best Practices)

Supply Air

Raised Floor

Supply Air

Raised Floor

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Airflow Enhancers (Cabinet Best Practices (Contd…))

Supply Air

Raised Floor

Dropped Ceiling

Supply Air

Raised Floor

Dropped Ceiling

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Airflow Enhancing Products•APC 2U Rack Air Distribution

•Delivers air directly from the raised floor into the rack inlet

•Minimizes top-bottom inlet temperature distribution

•Allows rack loads up to 3.5 kilowatts per rack

Side Rack Air Distribution Unit

Application View

Bottom-Top Rack Air Distribution Unit

Roof Air Removal Unit

Images: APC (www.apc.com)

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Airflow Enhancing Products (Contd…)

•Higher density rear door rack air removal unit

•Allows rack loads up to 16.5 kilowatts /14 kilowatts per rack

•Challenges in obtaining flow through tiles in the datacenter

Rittal Enclosure BlowerRittal Side Breathing Air

Baffle System

APC Liebert XDA

Images: Rittal (www.rittal-corp.com)

Images: www.apc.com and www.liebert.com

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Water-based Cooling Techniques

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Water-based Cooling

• Basis: QLOAD = mCp DT = rVCp DT

(Water has 3000 times higher heat carrying capacity than air)

• Chilled water from building supply

• Cooling high density servers up to 70 kilowatts per rack

• Lower energy cost as some of the CRAC units can be removed

• Avoid hotspots due to high power-density equipment

• Possible to have redundant systems (Chillers, pumps, piping, and power supply) to avoid downtime

• Importance of CDU

• Electrically conductive, corrosiveness and high flow rates

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Water-based Cooling

Raised Floor Raised Floor

Combination of Air and Water Cooling

Pure Water-based CoolingH

eat

Exch

anger

Heat Exchanger

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Water-based Cooling• Cooling system design by Naissus Thermal Management Solutions

• Heat removal of 20+ kilowatts

• Closed liquid loop with bottom mounted fin and tube heat exchanger

•Thermal test done with 5 blade serversPerformance Table - North American units SI units

Inputs Heat Load 24.0 kW 24.0 kW

Water Temp 12.8 degC 12.8 degC

Water Flow 0.76 l/sec 0.76 l/sec

Results Cold Air Supply 22.8 degC 22.8 degC

Hot Air Disch 49.8 degC 49.8 degC

Air DT 27.0 degC 27.0 degC

Water Rise 7.1 degC 7.1 degC

Water Disch 19.9 degC 19.9 degC

Water P.D. 48.3 kPa 48.3 kPa

Background Server Fans 1680 CFM Varies by manufacturer

Fan Power 700 watts

Performance Table - North American units SI units

Inputs Heat Load 24.0 kW 24.0 kW

Water Temp 12.8 degC 12.8 degC

Water Flow 0.76 l/sec 0.76 l/sec

Results Cold Air Supply 22.8 degC 22.8 degC

Hot Air Disch 49.8 degC 49.8 degC

Air DT 27.0 degC 27.0 degC

Water Rise 7.1 degC 7.1 degC

Water Disch 19.9 degC 19.9 degC

Water P.D. 48.3 kPa 48.3 kPa

Background Server Fans 1680 CFM Varies by manufacturer

Fan Power 700 watts

Heated Air

Thermal Core

Water from ChillerWater sent to Chiller

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Water-based Cooling

Temperature Distribution inside the Rack

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Water-based Cooling•Cooling system design by Vette Corp.

•Heat removal of up to 30 kilowatts

•Rear door closed loop liquid heat exchanger designed by IBM

•Currently available only for IBM Enterprise Rack

•Available from Rittal for retro-fit designs

IBM Rear Door Heat Exchanger

Pressure drop across the heat exchanger for a typical 1U fan setup

Images: www.vette-corp.com

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Water-based Cooling

•Cooling system design by APC.

•Heat removal of up to 70 kilowatts

•Controlled in-row cooling

•Row air containment

•Modularity

•Similar designs from HP (35 kilowatts)

•Similar concepts available from Rittal (30 kilowatts)

•Similar concepts available from Liebert (8 kilowatts and 17 kilowatts)

Heat Exchanger and Fan Assembly

Front View Rear View

Images: www.apc.com

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Refrigerant-based Cooling Techniques

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Refrigerant-based Cooling

•Phase change (latent heat transfer)

•Electronics-safe

•Low flow rates and non-corrosive

•Some systems are stand-alone and hence flexible

•CRAC units are the most common ones

•Chilled water from building supply may be used for supplemental cooling

•Expensive ( comparable to water+ additives)

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Refrigerant-based Cooling•Cooling system design by Liebert

•XDF- Cooling capacity of 14 kilowatts

•Stand-alone unit

Liebert XDF Self Contained Unit Images: www.liebert.com

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Refrigerant-based Cooling

•Cooling system design by APC.

•Heat removal of up to 43 kilowatts

•Modularity

•Rack air containment

APC In-Row Cooling

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Refrigerant-based Cooling•Cooling system design by Liebert

•XDV- Rack mount air conditioners (10 kilowatts) - Almost no floor space required

•XDH-Rack Cooling capacity up to 30 kilowatts

•Also available from Rittal

Liebert Roof Mount Cooling Liebert In-Row Cooling Rittal Rear Door Hx

Images: www.liebert.com

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Liquid Based Touch Cooling

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Water/Refrigerant-based Touch Cooling

•Direct contact cooling combined with chip cooling

•Remove heat at the source

Available from:

Clustered Systems

Rittal (Power electronics)

SprayCool (20 to 30KW)

Cold plate with Liquid Cooling

Liquid Cooling of Boards

Spray CoolingImages: www.spraycool.com

Images: www.rittal-corp.com Images: www.ibm.com

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•Cooling system design by Thermal Form and Function

•Pumped liquid multiphase cooling

•Heat removal of up to 10 kilowatts

per evaporator (Modular)

•Designed for retro-fit applications

•Air/Water cooled condenser unit can be used

Thermal Form and Function Refrigeration Unit

Two Phase Flow

Images: http://www.thermalformandfunction.com/

Refrigerant-based Touch Cooling

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Comparison of Cooling Techniques

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Comparative Analysis

• Study by Hannemann and Chu – Interpack ’07

• Comparative study of cooling technologies with a model datacenter

Area required for Cooling Equipment Power Consumption of Cooling Equipment

Capital Expenditure of Cooling Equipment

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Conclusion

• Reviewed innovative and commercially available technologies for cooling racks

• Discussed design approaches with use of CFD to maximize performance of air cooling

• Reviewed products and techniques for enhancing airflow within a rack

• Reviewed cooling of high density equipment using chilled water and refrigerant

• Selection of cooling strategy will depend on the specific requirements of the client

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Vendor Contacts

• APC – Morrison, Harold Wells Associates (925-355-9900)

• Rittal – Sales (800-477-4000)

• Liebert – Frank Stone (925-734-8660)

• Spray Cool – Sales (866-993-2665)

• Clustered Systems – Phil Hughes (415-613-9264)

• Trox AITCS - Thomas Hudgens (347-325-4347)

• Thermal Form and Function – Joe Marsala (978-526-9672)

• Vette Corp - Skye Emerson (508-203-4694)

• Naissus Thermal Management Solutions - Mirko Stevanovic (416-892-4071)

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References

• Product websites and communication with vendors

• Hannemann, R and Chu, H., (2007), “Analysis of Alternative Data Center Cooling Approaches”, ASME Interpack 1176, Vancouver, BC.

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Acknowledgement

• Speck Design

• Our colleagues at Electronic Cooling Solutions:

Khyati Varma

Ceferino Sanchez

Adriana Romero

Sridevi Iyengar

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