ASHRAE Journal - October 2022 - 17

COLUMN DATA CENTERS
Additional points:
* By far, it is the most debated technology due to
risks associated in taking fresh air into the white space
(a space where IT equipment and infrastructure are
placed) and high chances of control failures.
* Very critical to have the right amount and quality
of ambient air intake via automatic controls/dampers/
fi lter.
* High service cost to maintain fresh air fi lters.
* White space environment can be impacted by fresh
air quality if fi lter/controls are not operated and maintained
properly.
* As each unit has separate compressors, service cost
compared to the chiller system is high.
* " There was initial opposition to the inclusion of data
centers within ASHRAE Standard 90.1 and most recently
even more controversy as the result of many deployment
problems across the industry. " 1
Free Cooling With Dual Coil Direct-Expansion Water Cooled
Free cooling with dual coil (both DX and water-cooled)
can be in a CRAC or AHU/fan wall unit footprint. It consists
of dual coil, i.e., refrigerant coil and also the free
cooling water coil. Condenser water can be cooled either
by a dry cooler or cooling tower.
Additional elements as may be required by the client:
* Supply and installation of separate, independent
DX-water piping networks equal to the number of cooling
units or common piping network for multiple units.
* Supply and installation of water circulation
pumps-one for each water piping circuit or a common
pumping system for the full water network.
* If a cooling tower is used, then water treatment is
required.
Building side requirement:
* Supply and return cooling water pipes riser/wall
openings.
* Cooling tower or dry cooler space requirement,
either on the roof or ground.
* Potential weight issue of cooling tower or dry cooler
on the roof.
Additional points:
* As each unit has separate compressors, the service
cost compared to a chiller system is high.
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17
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* Water in white space (can be avoided by installing
CRAC/AHU in corridors).
* Multiple dry coolers can be avoided by using a common
cooling tower to multiple CRAC units.
* Ease of installation compared to air economizer/
chiller system.
* Better scalability.
Free Cooling With Direct-Expansion Pumped Refrigerant
Free cooling with DX pumped refrigerant can be in the
CRAC/package unit footprint. It consists of a refrigerant
pumping module with a separate air-cooled condenser
or as a package unit. The system can operate in various
modes depending upon the ambient temperature and
data center load, i.e., 100% free cooling (all compressors
off, only refrigerant pump operating), mixed mode
(some compressors off and some operating) and 100%
DX (all compressors operating).
Additional elements as may be required by the client:
http://www.spartiumcooler.com https://www.ashrae.org/
ASHRAE Journal - October 2022

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