With the reality of the "System-on-Chip" technology quickly approaching,
the demand for precise cooling of microprocessors is rising as fast as the temperatures
in today's office and data center environments. In short, computing applications
are experiencing dramatic increases in power/heat density loads.
"Hot spots," caused by densely packed servers and workstations, are
a prime culprit of extreme temperature swings. These circumstances create the
most pressing issue currently facing engineering and facility management professionals:
How to meet the ever-changing thermal requirement of computer hardware and still
maintain a comfortable working environment?
It has long been recognized that significantly higher heat fluxes can be accommodated
through the use of liquid cooling. Application of liquid cooling for microelectronics
may be categorized as either indirect or direct.
Indirect liquid cooling is one in which the liquid does not contact the microelectronic
chip, nor the substrate on which the chips are mounted. A thermal conduction
path is provided from the microelectronic heat sources to a liquid-cooled cold
plate attached to the module surface. Direct liquid cooling, on the other hand,
is a technique where there are no physical walls separating the microelectronic
chips and the surface of the substrate from the liquid coolant. This form of
cooling offers the opportunity to remove heat directly from the chip with no
intervening thermal conduction resistance other than that between the device
heat sources and the chip surfaces in contact with the liquid.
Consequently, a tremendous amount of effort is being devoted to evaluating
and developing a portfolio of products designed to deliver the best solution
based on a particular application. These products are based on cooling techniques
that include the Foundation Concept, where underfloor air is drawn directly
into the enclosure, which protects servers, workstations, and uninterruptible
power supplies (UPSs) and passes by liquid-filled coils. This technique, categorized
as indirect liquid cooling, can help maximize the cooling potential of the supply
Considering the range of cooling technologies available today, the mandate
for selecting larger-capacity air cooling units that occupy less floor space
will constitute a major factor in the drive to satisfy the increasingly substantial
loads still cooled by air. Reducing a cooling system's impact on floor space
will continue to be a critical challenge for plant engineers in the foreseeable
The bottom line involves the issue of increasing the criticality of cooling
systems to the site operation. Considering the fact that cooling equipment will
need to be as uninterruptible as the power system itself, the continuing trend
in heat/power density has numerous implications from the perspective of standby,
redundancy, and operational factors where N+1 will no longer be sufficient.
This, in turn, mandates the reinvigoration of current technologies in order
to accommodate anticipated increases in power/heat densities.
After spending thousands, if not millions, of dollars to purchase and install
sensitive electronic equipment, it should be an easy decision to properly protect
it. Creating and properly installing a correct precision air-conditioning control
system is more than just cutting into existing ductwork and adding vents. Thorough
site analysis and proper installation will result in a custom-designed precision
air-conditioning system that will provide optimum performance in cooling and
protecting sensitive electronic equipment.
Dave Kelley is manager of Air Products at Liebert Corp. (www.liebert.com),
Columbus, OH, a leading manufacturer of precision air-conditioning and power