Electronics Protection - July/August 2013 - (Page 12)
Feature
Reducing Room-Level Bypass Airflow Creates Opportunities
To Improve Cooling Capacity and Operating Costs
Lars Strong, P.E.
Upsite Technologies, Inc.
Misunderstandings About Bypass Airflow
The importance of managing openings in the raised floor is obvious, as conditioned air then only leaves the raised floor through
intentional openings such as perforated tiles or grates. However,
there are several misconceptions about the benefits of managing
the raised floor open area.
There is a common misconception in the industry: if a cable
opening is sealed and perforated tiles are properly managed, the
amount of bypass airflow is reduced. This may indeed happen,
but in most computer rooms where there is an excess of running
cooling capacity, and therefore an excess volume of conditioned
airflow, sealing cable openings and properly managing perforated
tiles shifts the location of bypass airflow to the cold aisle.
The arrows and numbers in the following figures represent
volumes and direction of air movement in computer rooms. The
number of cabinets and cooling units are simplified for clarity but
the ratios can be applied to rooms with many cooling units and
rows of equipment.
Figure 1 illustrates aReducing Room-Level Bypass Airflowthat has not
typical computer room Creates Opportunities to Improve Cool
completed raised floor open area management. The cooling unit
is supplying 10 units
of cooling airflow
volume. Unsealed
10
cable openings are
releasing a total of
6 units of volume,
and perforated tiles
2
2
The Evolution of Bypass Airflow
in cold aisles are
The Uptime Institute published the first paper on bypass airflow releasing 4 volumes
3
3
nearly 10 years ago. That research, conducted by engineers from
of conditioned air4
both the Uptime Institute and Upsite Technologies, quantified
flow. The IT equip10
the ratio of bypass openings to intentional openings, such as
ment consumes a
Figure 1. Typical 1: Typical Volumes
Figure Airflow Airflow Volumes
perforated tiles, in raised floors. The concept of bypass airflow
total of 4 units of
was developed with a focus on unmanaged openings in the raised
volume. In this case
floor. While unmanaged openings releaseReducing Room-Level Bypassnot Creates volume of to Improve Figure 1 illustrates a typical computer the volume
bypass air, they are Airflow the Opportunities air supplied by perforated tiles Costs
Cooling Capacity and Operating equals room that has
units
the cause of bypass airflow.
of air consumed by IT not completed raisedonly bypass airflow in the
equipment. The floor open area management.
is a f
therm
The definition of bypass airflow is any conditioned air supplied
room is air escaping The cooling unit is supplying 10 units of cooling airflow
point
volume. Unsealed cable openings are releasing a
by a cooling unit that does not pass through IT equipment before
from the unsealed
temp
total of 6 units of volume, and perforated tiles in
returning to a cooling unit. In addition, air that passes through IT
cable openings.
10
10
effici
cold aisles are releasing 4 volumes of conditioned
equipment multiple times is defined as IT equipment exhaust air cirFigure 2 illusthe f
airflow. The IT equipment consumes a total of 4 units
6
culation. The ideal for airflow in a computer room is for every moltrates the situation
of volume. In this case the volume of air supplied by
Many
ecule of conditioned air supplied by cooling units to pass through IT after the raised
perforated tiles equals the volume of air consumed by
seen
equipment just once before returning to a cooling unit. Any volume floor open area has IT equipment. The only bypass airflow in the room is
air escaping from the unsealed cable openings.
2
2
2
of air delivered by cooling units that is greater than the volume 2
of
been completely
air consumed by IT equipment becomes bypass airflow.
managed. Now the
Figure 2 illustrates the situation after the raised floor
3
The original Uptime Institute research revealed that on aver- 3
6 units of condiopen area has been completely managed. Now the 6
age 60 percent of computer room cooling capacity was escaping
tioned air volume
units of conditioned air volume that were escaping
4
10
10
10
through unsealed cable openings is also coming out of
through unsealed cable openings and misplaced perforated tiles.
that were escaping
the perforated tiles properly placed in the cold
Figure 2. Airflow After Sealing Raised Flooraisle.
Recent research by Upsite Technologies of 45 computer 1: Typical Airflow through unsealed
Figure rooms
Volumes
Figure 2: Airflow After Sealing Raised Floor
So now a total of 10 units of cooling capacity from
reveals that on average 48 percent of conditioned air is escaping
cable openings is
the cooling unit reaches the cold aisle, but since only
from unsealed openings and misplaced perforated tiles. These
also coming out of the4perforated tiles properly placed 6 units of
units are needed by the efficiency and in the cold
units, and therefore their IT equipment, capacity,
Figure 1 illustrates
statistics indicate surprisingly poor improvements in AFM a typical computer room that has total ofconditionedof coolingleave the cold aislethebypass
over the
aisle. So now a
10 units air volume capacity from as coolis a function of airflow volume, heat load, and the
not completed raised floor open area management.
Howe
airflow. This simplified example shows that changing
last decade. It is also clear that there is a The cooling a broader un- 10 units ofunit reaches the cold aisle, but since only return airare needed set
need for unit is supplying
ing cooling airflow
4 units temperature
thermostatically controlled
unit r
derstanding of AFM fundamentals. For example, Unsealed cable openings are releasingequipment, 6 the volumeconditioned air supplied by cooling air
by the IT a
units of of conditioned air cooling unit return
points of the units. Raising the volume leave the
volume. many of the sites
speed
units This
way to change the volume of bypass
in Upsite’s research had installed either hot or cold aislevolume, and perforated tiles as bypass airflow. is the only points isexampleway to increase the
cold aisle in
temperaturesimplified the only shows that
set
total of 6 units of containhave
airflow in a room.
ment without completing management of the raised floor bypass
efficiency and capacity of cooling units and realize
cold aisles are releasing 4 volumes changing the volume of conditioned air supplied by cooling units
of conditioned
theis the volume of bypass
airflow. The IT equipment consumes athe only way to changefull benefits of AFM efforts.airflow inopenings
open area.
is total of 4 units
It also misunderstood that sealing cable a room.
Based on field data on the amount of excess cooling capacity
running in data centers, there is vast unrealized opportunity to
reduce operating expenses and increase cooling capacity. At the
root of the considerations is room-level bypass airflow.
The data center industry is seeing a lot of emphasis on airflow
management (AFM) solutions as a way to improve reliability,
reduce operating costs, and increase cooling capacity. It is well
known that installing grommets to seal cable openings in the
raised floor and blanking panels in cabinets are best practices for
eliminating hot spots and prerequisites for the efficient operation
of any computer room cooling configuration. However, this fundamental step is often overlooked or unfinished before sites begin
installing AFM solutions such as hot or cold aisle containment.
Despite the multitude of AFM and containment solutions available today, data centers, on average, still have nearly four times
the capacity they need. Therefore, the full potential benefits of
these best practices remain largely unrecognized.
The misconception is that managing the openings of a raised
floor, or even installing full containment solutions, will eliminate
bypass airflow. The truth is that while these solutions solve intake
air temperature problems, and may reduce operating costs of IT
cooling fans, the volume of bypass airflow in the room remains
unchanged. Detecting and correcting this room-level issue lies in a
broader understanding of bypass airflow.
12
of volume. In this case the volume of air supplied by
perforated tiles equals the volume of air consumed by
July/August 2013
IT equipment. The only bypass airflow in the room is
www.ElectronicsProtectionMagazine.com
air escaping from the unsealed cable openings.
and other obvious sources of bypass airflow increases
Many sites temperatures to cooling best practices and
have implemented AFM units and cooling
return air
seen some or all of the following benefits:
unit efficiency.
Improved IT intake air temperatures
As shown in the figures above, sealing the openings in
Four
http://www.ElectronicsProtectionMagazine.com
Table of Contents for the Digital Edition of Electronics Protection - July/August 2013
Electronics Protection - July/August 2013
Newer Technology Releases Next-Generation Power2U AC/USB In Wall Charging Solution
Subzero Engineering Introduces PolarXpress DCiM SaaS Monitoring Solution
Specifiers of Enclosures for Components in Outdoor Applications: Be Aware of Material Selection Issues
Formable Phase Change Materials as Latent Heat Sinks for Portable Electronic Devices
How to Protect Electronic Circuits from Power Surges
Diamond Heat-Spreaders: Growth Methods and Applications
Standards-Based Design & Electronic Packaging Solutions
Reducing Room-Level Bypass Airflow Creates Opportunities to Improve Cooling Capacity and Operating Costs
Harnessing Laboratory Wind Tunnels
New DVR Enclosure with Prepackaged Thermoelectric Cooler
New Silver Conductive Aqueous Based Sodium Silicate System for EMI/RFI Shielding
Citizen and MechaTronix LED Cooling Cooperate On New Generation CitiLED COB’s
Eaton Expands 5P UPS Product Line to Provide Efficient Protection for Any IT Environment
Flex-Block System Puts Free-Standing Enclosures on New Footing
Gore Introduces Acoustic Vent for Protecting Electronic Devices
Industry News
Calendar of Events
Electronics Protection - July/August 2013
https://www.nxtbook.com/nxtbooks/webcom/ep_2017summer
https://www.nxtbook.com/nxtbooks/webcom/ep_2017spring
https://www.nxtbook.com/nxtbooks/webcom/ep_2017winter
https://www.nxtbook.com/nxtbooks/webcom/ep_2016fall
https://www.nxtbook.com/nxtbooks/webcom/ep_2016summer
https://www.nxtbook.com/nxtbooks/webcom/ep_2016spring
https://www.nxtbook.com/nxtbooks/webcom/ep_2015winter
https://www.nxtbook.com/nxtbooks/webcom/ep_2015fall
https://www.nxtbook.com/nxtbooks/webcom/ep_2015summer
https://www.nxtbook.com/nxtbooks/webcom/ep_2015spring
https://www.nxtbook.com/nxtbooks/webcom/ep_2014winter
https://www.nxtbook.com/nxtbooks/webcom/ep_2014fall
https://www.nxtbook.com/nxtbooks/webcom/ep_2014summer
https://www.nxtbook.com/nxtbooks/webcom/ep_2014spring
https://www.nxtbook.com/nxtbooks/webcom/ep_20140102
https://www.nxtbook.com/nxtbooks/webcom/ep_20131112
https://www.nxtbook.com/nxtbooks/webcom/ep_20130910
https://www.nxtbook.com/nxtbooks/webcom/ep_20130708
https://www.nxtbook.com/nxtbooks/webcom/ep_20130506
https://www.nxtbook.com/nxtbooks/webcom/ep_20130304
https://www.nxtbook.com/nxtbooks/webcom/ep_20130102
https://www.nxtbook.com/nxtbooks/webcom/ep_20121112
https://www.nxtbook.com/nxtbooks/webcom/ep_20120910
https://www.nxtbook.com/nxtbooks/webcom/ep_20120607
https://www.nxtbook.com/nxtbooks/webcom/ep_20120304
https://www.nxtbook.com/nxtbooks/webcom/ep_20120102
https://www.nxtbook.com/nxtbooks/webcom/ep_20111112
https://www.nxtbook.com/nxtbooks/webcom/ep_20110910
https://www.nxtbook.com/nxtbooks/webcom/ep_20110607
https://www.nxtbookmedia.com