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Research Papers

From Chip to Cooling Tower Data Center Modeling: Influence of Air-Stream Containment on Operating Efficiency1

[+] Author and Article Information
Thomas J. Breen

e-mail: thomas.breen@ul.ie

Jeff Punch

Stokes Institute, University of Limerick, Limerick, Ireland

Niru Kumari

Hewlett-Packard Laboratories, Palo Alto, CA 94304

1Reprinted from the proceedings of the ASME/JSME 2011 8th Thermal Engineering Joint Conference (AJTEC2011-44091).

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the Journal of Electronic Packaging. Manuscript received December 20, 2010; final manuscript received June 5, 2012; published online October 30, 2012. Assoc. Editor: Saurabh Shrivastava.

J. Electron. Packag 134(4), 041006 (Oct 30, 2012) (9 pages) doi:10.1115/1.4007110 History: Received December 20, 2010; Revised June 05, 2012

In the drive to enhance data center energy efficiency, much attention has been placed on the prospect of airflow containment in hot-aisle cold-aisle raised floor arrangements. Such containment prevents airflow recirculation, eliminating the mixing effects of the hot and cold air streams that can cause an undesirable temperature rise at the inlet of the equipment racks. The intuitive assessment of the industry has been that the elimination of such mixing effects increases the energy efficiency of the data center cooling system by enabling delivery of air at higher inlet temperatures, thus reducing the amount of infrastructure cooling required. This paper employs an end-to-end modeling approach to analyze the effect of air stream containment in the computer room and its impact on the holistic system efficiency. Dimensionless heat index parameters are employed to characterize the effects of containment, recirculation, and mixing within the computer room environment. The extent of recirculation is shown to primarily influence the operation of the rack and computer room air conditioning (CRAC) level cooling systems, with the chiller systems also impacted. The overall effect on the complete cooling system performance and data center efficiency requires balancing of these effects. Through this model analysis, it is shown that containment may negatively impact overall energy efficiency in some circumstances, and that recirculation may actually be beneficial to overall energy efficiency under certain system dependent operating thresholds.

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Figures

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Fig. 1

Hot-aisle cold-aisle arrangement of typical air cooled data center

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Fig. 2

Regions of room level air streams in a raised floor, uncontained data center

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Fig. 3

Containment, recirculation, and CRAC provisioning scenarios

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Fig. 4

Rack inlet temperature for linearly variable heat sink temperature control

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Fig. 5

Model results for heat sink temperature control varying linearly with inlet temperature (THSREF 50 °C) for contained and uncontained environments with recirculation

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Fig. 6

Rack inlet temperature for fixed heat sink temperature control

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Fig. 7

Model results for fixed and constant heat sink temperature control (THSREF 50 °C) for contained and uncontained environments with recirculation

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Fig. 8

Effect of increasing THSREF for variable temperature heat sink control

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Fig. 9

Model results for fixed and constant heat sink temperature control for contained and uncontained environments with recirculation and variable THSREF.

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Fig. 10

Effect of CRAC supply air temperature and SHI on COPGRAND with HS inlet air temperature for a variable temperature chip thermal control (THSREF 50 °C)

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