ASHRAE Journal - August 2008 - (Page 58)

Originally developed for cold pasteurization in the food industry, this system encapsulates water hardness minerals and particulates into a nonadherent powder that is harmlessly deposited in the bottom of the sump. The device controls scaling of the wetted media pad and biological growth in the sump water. Under proper operation, the pulse-power component will maintain clean sump water with low bacteria counts free of bioﬁlm and will eliminate the breeding ground for the ampliﬁcation of Legionella and other waterborne pathogens.9 Conclusions For years, computer room air-conditioning (CRAC) units have been the design standard for data center cooling. Increasing heat densities produced by the modern electronics inside these facilities has now forced designers to reevaluate central station air-handling units as a design solution. In addition to their ability to incorporate the WBE, large air-handling units offer the following advantages over CRAC system: Recapture of valuable data center ﬂoor space for computer hardware; Increased computer-center security through the elimination of in-room maintenance of CRAC units; Simpliﬁed room dew-point control for the data center with less risk of humidiﬁers and dehumidiﬁcation cooling coils ﬁghting one another; Filtration redundancy; and Refrigeration redundancy. With an installed cost in the range of $0.75 to $0.90 per cfm ($1.60 to $1.90 per L/s), the payback for an adiabatic cooler/ humidiﬁer component in a central station air-handling unit should be less than one year for the 24/7 duty cycle of a data center. With credit given for the elimination of cooling towers, water-to-water heat exchangers, unit mounted coils, pumps, and piping associated with water side economizers, the owner ﬁrst cost of a WBE may be more than offset. Since we are addressing the data center cooling load directly with the ambient wet bulb, we eliminate the heat transfer losses of a water-side economizer at the tower, the water-to-water heat exchanger, and the unit mounted cooling coil. Sensible cooling Energy Efﬁciency Ratios (EER) for the WBE are a function of the air side static pressure loss and the recirculation water pump penalty. EERs for direct evaporative cooling systems often exceed 100 Btus converted per watt expended (105.51 kJ/W) compared to refrigeration systems EERs, which range between six and 10 Btu/W (6.33 and 10.55 kJ/W).10 Data center cooling and the slang phrase “swamp cooler” have never before been coupled in an article on “green” computer center design. Perhaps at long last, it is time to take another look at a technology that has been around since the time of the pharaohs. Wet-bulb economizers provide a sustainable solution to a growing computer cooling problem. References 1. EPA. 2007. “Report to Congress on Server and Data Center Energy Efﬁciency.” Washington, D.C.: U.S. Environmental Protection Agency. 2. Associated Press. 2007. “Tech Companies Tout Greener Data Centers.” B. Bergstein. The Press Democrat, August 9, p. E-5. 3. Fok, S. 2008. “Improving Industrial Competitiveness by using the Environment for Free Cooling in Data Centers: Eliminating the Fear Factor.” Seminar 45, ASHRAE Winter Meeting. 4. Tschudi, W. 2007. “Data Center Economizer Contamination and Humidity Study.” LBNL/Paciﬁc Gas & Electric. http://tinyurl. com/3y4es7 (or http://hightech.lbl.gov/documents/DATA_CENTERS/ EconomizerDemoReportMarch13.pdf). 5. Sorell, V 2007. “OA economizers for data centers.” ASHRAE . Journal 49(12):32 – 37. 6. Munters Evaporative Cooling Division. 1992. “Engineering Bulletin.” EB-006-PR. 7. Sohr, R.T. 1997. “The most precise and clean mode for humidiﬁcation of space.” ASHRAE Transactions 103(2):886–893. 8. ASHRAE. 2006. ASHRAE GreenGuideThe Design, Construction, and Operation of Sustainable Buildings, 2nd ed. ASHRAE Green Tip 14, p. 191. 9. Puckorius, P.R., et al. 1995. “Why evaporative coolers have not caused Legionnaires= disease.” ASHRAE Journal 37(1):29 – 33. 10. Watt, J.R., W.K. Brown. Evaporative Air Conditioning Handbook, 3rd ed. Lilburn, Ga.: Fairmont Press pp.182 and 289. www.info.hotims.com/16017-22 58 ASHRAE Journal ashrae.org August 2008 http://tinyurl.com/3y4es7 http://tinyurl.com/3y4es7 http://hightech.lbl.gov/documents/DATA_CENTERS/EconomizerDemoReportMarch13.pdf http://hightech.lbl.gov/documents/DATA_CENTERS/EconomizerDemoReportMarch13.pdf http://www.goodway.com http://www.goodway.com http://www.info.hotims.com/16017-22

Table of Contents Feed for the Digital Edition of ASHRAE Journal - August 2008

ASHRAE Journal - August 2008 Contents Commentary Industry News Letters Meetings and Shows Maintain to Sustain—Delivering ASHRAE’s Sustainability Promise Ultraviolet Germicidal Irradiation: Current Best Practices Improving Humidity Control With Energy Recovery Ventilation Single- or Two-Stage Compression Data Center Cooling: Using Wet-Bulb Economizers Building Sciences InfoCenter Practical Pointers Products Emerging Technologies Washington Report People Special Products Classified Advertising Advertising Index

ASHRAE Journal - August 2008

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