The Advantages of HotCold Aisle Isolation

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The Advantages of Hot/Cold Aisle Isolation

• Energy Savings
• Increased Cooling capacity

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The Evolution of Airflow Management

• The next level of improvement was the advent of
  the Hot/Cold aisle design.
• This created the first separation of hot and cold
  air.
• Other tools included
• Proper perf tile placement and percentage
• Proper CRAC placement
• Elimination of cable cut out holes
• Blanking panels

3
Optimum Hot/Cold Aisle Floor Design
Even with direct hot air pathways back to the
CRAC units the cold air floods across the floor
and mixes with the hot exhaust air.
4
Isolation Technology Eliminates the Mixture of
Hot/Cold Air
Physical barriers create complete separation of
hot and cold air. Thus eliminating mixture. This
then allows the natural principles of hot and
cold air to work. Hot air rises away from
computer racks. Cold air pools in an enclosed
aisle.
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Case Study Flood Cooling vs Isolation Technology
The case study was preformed in a data center
that was laid out with hot and cold aisles using
a chilled water CRAC with a total capacity of 407
tons. The chilled water temperature was set to 41
degrees. The hot and cold air mixture created a
return temperature that lowered cooling capacity
and required operators to set the temperature set
points to be lower then required.
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Isolation Technology Case Study
Next the data center was fitted with a Isolation
system that completely separated the hot and
cold air. This greatly increased the temperature
of return air to the CRAC units.
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Increase of Cooling Capacity due to Higher Return
Temperatures
As the return air temperature increased so did
the cooling capacity.
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Cold Aisle Isolation
Increased cooling capacity was only the
beginning. CRAC temperature set points were also
increased. This allowed the CRAC unit not to work
as hard. Likewise the chilled water temperature
was increased 3 degrees. Also humidity set points
were lowered.
10
Case Study Conclusion

• This isolation design literally doubles the
  cooling capacity of the installed CRACs and
  allows the chilled water temperature to be
  increased to 44F, which would substantially
  increase the efficiency of the entire 4,250 ton
  district chilled water system.
• The data center increased cooling capacity while
  saving upwards of 25 in energy.

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Hot/Cold Aisle Isolation and Humidity

• Humidification is very energy intensive.
  Dehumidification incurs even higher energy costs
  since the air is usually cooled to below 45
  degrees to condense out water and then is
  reheated by an electric heater to ensure the
  supply air in not too cold.
• Modern servers do not require extremely tight
  humidity control.
• Computers do not emit humidity, nor do they
  require fresh outdoor ventilation air, so a
  well designed and controlled data center should
  have minimal humidity loads.

12
Isolating Cold Intake Air Ensures a Tighter
Humidity Set Point

• Use widest range as possible 30 to 70
• Low range during very cold and dry
• High range during hot humid weather

13
Industry Studies on Isolation Technology

• HP
• Berkeley Labs
• Department of Energy (Verizon and Lucas Films)
• Mckinstry

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Berkeley Labs Test
16
Berkeley Labs Test
17
Isolation Technology allows an increase in
chiller temperatures
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Berkeley Labs Test
19
McKinstry Study
20
SubZero Engineering CFD
Hot air return to CRAC unit creates hot/cold air
mixture
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SubZero Engineering CFD
Cold Aisle Isolation fully separates hot/cold
airflow
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Conclusion

• Isolation Technology allows for
• Increases to temperature set points
• Increase in cooling capacity
• Broader range of Humidity set points

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Resources

• Pacific Gas and Light A Design guide source
  book for high performance data centers.
• Thermal Guidelines for Data Processing
  Environments, TC9.9 Mission Critical
  Facilities,ASHRAE, 2004.
• Data Processing and Electronic Areas, Chapter 17,
  ASHRAE HVAC Applications, 2003.
• Design Recommendations for High Performance Data
  Centers, Rocky Mountain Institute, 2003.