d a t a center applica t i o n guide Reduce data center PUE using Munters innovative cooling solutions
Reduce data center energy costs by up to 75% Traditional refrigeration cooling systems are an inefficient means of rejecting heat from modern data centers. With Munters Oasis Indirect Air-Side Economizer (IASE) and Wet-Bulb Economizer (WBE) products, the energy required to remove heat is significantly reduced. Munters systems use cooling/heat rejection strategies that achieve a balance of reliability and energy efficiency for data centers, some using as little as 20% of the cooling energy required by conventional cooling systems. In the last few years, several trends have emerged that have impacted the way that digital data are manipulated, stored and transmitted. There are three distinct trends: Tremendous increase in data transmitted, led by social networking, video, music, and voice transmission and cloud computing Ability of electronics to operate at higher temperatures Increase in IT equipment utilization by use of virtual computing which leads to greater power density per unit area of a data center These trends place a greater demand on data center cooling systems. However, the cooling process now occurs at higher inlet and outlet temperatures, resulting in the emergence of a new breed of cooling systems. Engineers have identified several new energy-efficient solutions to manage the thermal loads in data centers. Each strategy has pros and cons, but the biggest dilemma faced by engineers and clients is deciding which one to use. Munters simplifies this process by presenting the indirect air-side economizer, which has the potential to outperform current cooling strategies while offering some key system advantages. With over 35 years of experience with airto-air heat exchangers and evaporative cooling, Munters advanced cooling systems will provide the desired cooling results using significantly less energy than standard air conditioning. Munters offers custom system designs integrating DX, chilled water, indirect and direct evaporative and economizer cycles to meet the specific requirements of any facility. The indirect air-side economizer The indirect air-side economizer (IASE) 3 is a relatively new approach to data center heat rejection. It uses outdoor air to reject heat, with Current energy-efficient data center cooling options Air-side economizers (ASEs), where outdoor air is used for "free cooling" during favorable ambient conditions. ASE s complemented with direct evaporative cooling (DEC) for humidity control and operation over an extended envelope of ambient conditions, referred to as Wet-Bulb Economizers (WBEs) 1 Water-side economizers (WSEs), where cooling towers or fluid coolers are used in a variety of design configurations to reject some, or all of the heat from the data center in combination with, or without, chilled water or DX cooling 2 Combination air and water-side economizers (CAWEs) CAWEs complemented with DEC, referred to here as CAWE+D Liquid-cooled enclosures (LCEs), sometimes referred to as In-Row or In-Rack Cooling, where cool water produced from a combination of chillers and cooling towers, or refrigerant, is pumped to heat exchangers installed directly within the server racks the outdoor air never entering the process or white space. The Oasis IASE uses an air-to-air heat exchanger (HX) to transfer data center heat to a separate outdoor airstream ("scavenger air"). Figure 1 (page 3) shows details of one type of Munters Oasis IASE system that uses horizontal polymer-tube heat exchangers. With this design, outdoor scavenger air is drawn across the exterior of elliptical tubes, which are wetted by a recirculation water pump. The elliptical shape of the heat exchanger tubes maximizes the allowable surface area for heat rejection and is sufficiently elastic such that its subtle expansion and contractions, resulting from normal operation, aid in the shedding of residual solids that are a by-product of evaporation. With scavenger air flowing over the wet exterior tube surfaces, evaporative heat transfer efficiently cools the data center hot aisle air flowing through the inside of the tubes. Although only 45% to 51% effective when operating dry, when the outside of the polymertube HX is wetted it operates with 70% to 80% wet-bulb depression effectiveness (WBDE) as an indirect evaporative cooler. WBDE is a measure of the approach of the hot-aisle drybulb temperature to the outdoor air wet-bulb temperature. Using a 75% WBDE HX design, 100% of data center heat may be rejected solely using indirect evaporative cooling (IEC) if the following parameters exist: Ambient wet-bulb temperature is 66.2 F (19 C) or lower Hot aisle temperature (including recirculation fan heat) is 101.5 F (38.6 C) The target cold aisle temperature is 75 F (23.9 C) 2 Data Center Application Guide
Figure 1: Oasis Indirect Evaporative Cooling System utilizing a polymer tube heat exchanger Scavenger Air Leaves System Exhaust/Scavenger Air Optional Condenser Coil Optional Compressor Vestibule Cooled Air is Ducted Back to Data Center for Heat Extraction Hot Aisle Return Air Scavenger Outside Air Optional Cooling Coil (DX or CHW) Cold Aisle Supply Air Hot Data Center Air Enters EPX Polymer Tube for Sensible Dry Cooling by the Evaporating Water Film on Tube Exterior Scavenger Air Flows Up and Around Outside of Tubes Having Extracted Heat from Air Flowing Inside Tubes Supply air temperature control Supply temperature is controlled on Oasis IASE systems by varying the scavenger airflow in combination with staging or modulating supplemental refrigeration as required. Scavenger fan motors are equipped with variable speed drives. When the ambient wet bulb is high, the scavenger fans run at 100% of design, to achieve maximum heat rejection. At cooler ambient conditions, the scavenger fans throttle back significantly, rejecting heat using a fraction of the power required at peak ambient wet bulb conditions. Supply fan speed control Supply fan motors on Oasis IASE units are equipped with Variable Speed Control such that the supply airflow from the units can closely match the airflow of the IT equipment fans. Too much air delivered into a contained rack system is wasteful, and too little air starves the IT fans, which can lead to hot spots. There are a variety of control algorithms currently being employed. Munters engineers work closely with the consulting engineers and customers to achieve the desired result. Side stream filtration A SSF system with MERV 13 filtration provides the necessary particulate removal in a more energy-efficient way compared to conventional air-handling designs. Figure 2 (page 6) For many data centers, the outdoor air (introduced by a separate makeup air system) is independently filtered with MERV 8 + MERV 13 filters. The removal of air filters within the Oasis IASE units relieves a burden of what is typically estimated at 1-inch wc (248.8 pa) of pressure drop from these heat rejection work horses. This results in a significant reduction in power consumption amounting to at least 1.65 kw/10,000 CFM (assumes fan static efficiency of 75% and motor efficiency of 95%). Since conventional air-side economizer units must utilize filtration (ASHRAE recommends MERV 8 + MERV 11 or 13 filters), the recirculating Munters Oasis IASE units installed at NV Energy in Las Vegas, Nevada air Oasis IASE heat rejection units consume less supply fan power than air-side economizer units because the air pressure drop through the polymer-tube HXs is typically less than 1-inch wc (248.8 pa). Data Center Application Guide 3
Worldwide effectiveness Other cities Percentage of annual hours in a typical year (TMY2) where IASE satisfies 100% of Data Cooling needs Percentage of Total Tonnage picked up by IEC during ASHRAE 0.4% WB Design Condition Seattle 99.1% 96.7% Los Angeles 92.8% 87.5% Boulder 99.3% 100.0% Mexico City 100.0% 100.0% Chicago 84.0% 70.1% Atlanta 65.7% 70.1% Toronto 90.2% 77.7% London 98.9% 94.6% Stockholm 99.7% 99.3% Rome 70.5% 65.0% Moscow 96.4% 90.0% Abu Dhabi 28.7% 43.5% Mumbai 11.2% 57.2% Shanghai 62.5% 54.5% Tokyo 73.6% 65.0% Salt Lake City 98.8% 96.4% Fort Worth 58.8% 67.5% Boston 86.5% 75.1% Brasilia 47.8% 85.0% Paris 95.8% 85.1% Berlin 97.2% 92.2% Barcelona 73.9% 70.2% Madrid 93.4% 84.8% Vienna 94.1% 89.8% Bejing 73.8% 65.0% Guangzhou 38.7% 57.2% Note TMY2: 100 F hot aisle, 75 F cold aisle Singapore 0.0% 59.8% Santiago 95.5% 92.0% São Paulo 57.3% 80.2% Johannesburg 98.0% 98.7% Sydney 76.8% 80.2% Auckland 92.8% 87.5% 4 Data Center Application Guide Data Center Application Guide 5
Makeup air and humidity control Humidity control within data centers is one of many concerns for design professionals. A dedicated outdoor air system (DOAS), that provides humidification and dehumidification as required, should be used in conjunction with Oasis IASE units, as indicated in Figure 2. Currently 0.25 air-changes-per-hour of ventilation air is recommended for data centers to prevent excessive build-up of VOCs and other pollutants that may be generated within the space. During cold, winter conditions, hotaisle air from the data center may be mixed with outdoor air, allowing for energy efficient adiabatic humidification. Using this method, no supplemental heat is required, since the heat for vaporization comes directly from the data center air. The preferred method of adiabatic humidification uses glass fiber wetted media and requires no special water treatment. Wetted media type humidifiers may be controlled by split-media staging or modulating face and bypass dampers around the evaporative media, as required to maintain room dew point at the lowest recommended level currently about 40 F (4.4 C). In humid climates, where ambient dewpoint frequently exceeds 65 F (18.3 C), it is recommended that the DOAS system include dehumidification capability. Dehumidification may be accomplished by inclusion of a DX or chilled water coil, or to achieve higher moisture removal efficiency, a waste heat reactivated desiccant or pre-cool air reheat system may be used. Dehumidification systems should be designed to deliver air at 45 F (7.2 C) dewpoint, or lower as required, such that room dewpoint may be controlled to 60 F (15.5 C) maximum using the minimum outdoor air delivered as the sole means for dehumidifying. Figure 2: Typical application of data center cooling and makeup air equipment. O/A MAKEUP AIR DEHUMIDIFICATION/ HUMIDIFICATION UNIT 0.25 ACH MIN OSA SCAVENGER OSA IN 100% RECIRCULATION AIR COOLING UNITS SFAN HX Q C C WINTER R/A SIDE-STREAM FILTRATION UNIT 6-10 ACH COLD AISLE SUPPLY HOT AISLE RETURN SERVER RACK 6 Data Center Application Guide
Benefits of Oasis indirect air-side economizer Filters may be eliminated from some or all of the heat rejection air-handing units (AHUs) because the data hall air is recirculated and cooled with the Oasis IASE systems without introducing outdoor air into the data center. Particulate removal may be accomplished by using a side-stream filtration unit, or filters may be included in a portion of the Oasis IASE units, such that the room air is filtered at a rate of perhaps 6 to 10 ACH, leading to reduced filter, maintenance, and fan power costs compared to installing filters on all of the heat rejection units, which often have air turnover rates in excess of 100 ACH. Reduced risk of outdoor air pollutants adversely affecting the IT equipment because no outdoor air is introduced into the space by the heat rejection units. Space humidity and pressure are not impacted, resulting in the potential to lower humidification costs and maintain more stable moisture levels in the data hall. Makeup air units, with MERV 8 and MERV 13 filters, equipped with dehumidification and humidification capability as required by the local climate, provide the recommended ventilation (0.25 ach has been recommended as the minimum) and humidity control. Humidification may be accomplished using direct evaporative media with heat from recirculated hot-aisle air. Decoupling the MUA function allows the Oasis IASE units to be optimized for one task: heat rejection. Unlike water-side and wet-bulb economizer systems, Oasis IASE systems may operate dry during cooler ambient conditions, resulting in lower annual water consumption and eliminating freeze concerns. During dry operation, Oasis IASE systems are able to achieve 100% heat rejection when outdoor air temperature is below 48.5 F (9.2 C) using HXs that are 50% effective, or 66.2 F (19 C), using HXs that are 75% effective (based on a hot aisle temperature of 101.5 F (38.6 C), cooling to 75 F (23.9 C). Modulating mixed air dampers and relief fans/dampers are not required as part of the heat rejection cycle. Oasis IASE s require about one-third of the water flow rate of conventional water-side economizer systems, and operate with less pump head, resulting in significant annual pump power savings. When integrated with indirect evaporative cooling, refrigeration capacity may be significantly reduced on Oasis IASE systems in virtually all climates. Oasis IASE units have a rapid restart after power outage with little delay reaching full heat rejection potential. The Oasis IASE strategy is appli cable to data centers across the globe and is not limited for use in areas perceived to be cold or dry climates. The Oasis IASE strategy may be used even when cooler cold-aisle conditions are desired. The 100 F (37.8 C) hot-aisle and 75 F (23.9 C) cold-aisle conditions are solely a point of reference, since modern data centers are designed to similar or more aggressive conditions. Clearly, the maximum benefit of the Oasis IASE strategy is derived when implemented with hot- or cold-aisle containment, with warmer hot-aisle and warmer cold-aisle temperatures. 1 Scofield, M. and T. Weaver. Using Wet-Bulb Economizers, Data Center Cooling. ASHRAE Journal, August 2008: 52-58 2 Yury, Y.L. Waterside and Airside Economizers, Design Considerations for Data Center Facilities. ASHRAE Transactions, Volume 116, Part 1, 2010 3 Dunnavant, K. Data Center Heat Rejection. ASHRAE Journal, March 2011: 44-54 Data Center Application Guide 7
Munters locations Munters is a global leader in energy efficient air treatment solutions Using innovative technologies, our expert engineers create the perfect climate for customers in a wide range of industries, with the largest being food, pharmaceutical and data center sectors. Munters has been defining the future of air treatment since 1955. Today, manufacturing and sales are carried out in 30 countries by around 3,000 employees. Munters reports annual net sales in the region of SEK 4 billion and is owned by Nordic Capital Fund VII. For more information see www.munters.com Australia Munters Pty Limited, Phone +61 2 6025 6422, Fax +61 2 6025 8266, Austria via sales organization in Germany, Brazil Munters Brasil Industria e Comercio Ltda, Phone +55 41 3317 5050, Fax +55 41 3317 5070, China Munters Air Treatment Equipment (Beijing) Co., Ltd., Phone +86 10 80 481 121, Fax +86 10 80 483 493, Denmark via sales organization in Sweden, Finland Munters Oy, Phone +358 9 83 86 030, Fax +358 9 83 86 0336, France Munters France S.A., Phone +33 1 34 11 57 50, Fax +33 1 34 11 57 51, Germany Munters Euroform GmbH, Phone +49 241 89 00 0, Fax +49 241 89 00 5199, Indonesia Munters, Phone +62 21 9105446-7, Fax +62 21 5310509, Italy Munters Italy S.p.A., Phone +39 0183-52 11, Fax +39 0183-521 333, Japan Munters K.K., Phone +81 3 5970 0021, Fax +81 3 5970 3197, Kingdom of Saudi Arabia and Middle East Hawa Munters, c/o Hawa United Cooling Syst. Co. Ltd., Phone +966 1 477 15 14, Fax +966 1 476 09 36, Korea Munters Korea Co,. Ltd, Phone +82 2 761 8701, Fax +82 2 761 8777, Mexico Munters Mexico Phone +52 722 270 40 30, Fax +52 722 270 41 95, Norway via sales organization in Sweden, South Africa and Sub-Sahara Countries Munters (Pty) Ltd, Phone +27 11 997 2000, Fax +27 11 608 3501, Spain Munters Spain S.A., Phone +34 91-640 09 02, Fax +34 91-640 11 32, Sweden Munters Europe AB, Phone +46 8 626 63 00, Fax +46 8 754 56 66, Switzerland via sales organization in Germany, Thailand Munters (Thailand) Co. Ltd., Phone +66 2 645 2708-12, Fax +66 2 645 2710, United Kingdom Munters Ltd, Phone +44 845 644 3980, Fax +44 845 644 3981, USA Munters Corporation Fort Myers, Phone +1 239 936 1555, Fax +1 239 936 8858, Munters Corporation Mason, Phone +1 888 335 0100, Fax +1 517 676 7078, Export & other countries Munters, Phone +46 8 626 63 00, Fax +46 8 754 56 66. Your closest distributor Munters Corporation Tel: (800) 843-5360 E-mail: dhinfo@munters.com www.munters.us AG0026-02 01/14