Electronics Protection - July/August 2013 - (Page 12)

Feature Reducing Room-Level Bypass Airflow Creates Opportunities To Improve Cooling Capacity and Operating Costs Lars Strong, P.E. Upsite Technologies, Inc. Misunderstandings About Bypass Airflow The importance of managing openings in the raised floor is obvious, as conditioned air then only leaves the raised floor through intentional openings such as perforated tiles or grates. However, there are several misconceptions about the benefits of managing the raised floor open area. There is a common misconception in the industry: if a cable opening is sealed and perforated tiles are properly managed, the amount of bypass airflow is reduced. This may indeed happen, but in most computer rooms where there is an excess of running cooling capacity, and therefore an excess volume of conditioned airflow, sealing cable openings and properly managing perforated tiles shifts the location of bypass airflow to the cold aisle. The arrows and numbers in the following figures represent volumes and direction of air movement in computer rooms. The number of cabinets and cooling units are simplified for clarity but the ratios can be applied to rooms with many cooling units and rows of equipment. Figure 1 illustrates aReducing Room-Level Bypass Airflowthat has not typical computer room Creates Opportunities to Improve Cool completed raised floor open area management. The cooling unit is supplying 10 units of cooling airflow volume. Unsealed 10 cable openings are releasing a total of 6 units of volume, and perforated tiles 2 2 The Evolution of Bypass Airflow in cold aisles are The Uptime Institute published the first paper on bypass airflow releasing 4 volumes 3 3 nearly 10 years ago. That research, conducted by engineers from of conditioned air4 both the Uptime Institute and Upsite Technologies, quantified flow. The IT equip10 the ratio of bypass openings to intentional openings, such as ment consumes a Figure 1. Typical 1: Typical Volumes Figure Airflow Airflow Volumes perforated tiles, in raised floors. The concept of bypass airflow total of 4 units of was developed with a focus on unmanaged openings in the raised volume. In this case floor. While unmanaged openings releaseReducing Room-Level Bypassnot Creates volume of to Improve Figure 1 illustrates a typical computer the volume bypass air, they are Airflow the Opportunities air supplied by perforated tiles Costs Cooling Capacity and Operating equals room that has units the cause of bypass airflow. of air consumed by IT not completed raisedonly bypass airflow in the equipment. The floor open area management. is a f therm The definition of bypass airflow is any conditioned air supplied room is air escaping The cooling unit is supplying 10 units of cooling airflow point volume. Unsealed cable openings are releasing a by a cooling unit that does not pass through IT equipment before from the unsealed temp total of 6 units of volume, and perforated tiles in returning to a cooling unit. In addition, air that passes through IT cable openings. 10 10 effici cold aisles are releasing 4 volumes of conditioned equipment multiple times is defined as IT equipment exhaust air cirFigure 2 illusthe f airflow. The IT equipment consumes a total of 4 units 6 culation. The ideal for airflow in a computer room is for every moltrates the situation of volume. In this case the volume of air supplied by Many ecule of conditioned air supplied by cooling units to pass through IT after the raised perforated tiles equals the volume of air consumed by seen equipment just once before returning to a cooling unit. Any volume floor open area has IT equipment. The only bypass airflow in the room is air escaping from the unsealed cable openings. 2 2 2 of air delivered by cooling units that is greater than the volume 2 of been completely air consumed by IT equipment becomes bypass airflow. managed. Now the Figure 2 illustrates the situation after the raised floor 3 The original Uptime Institute research revealed that on aver- 3 6 units of condiopen area has been completely managed. Now the 6 age 60 percent of computer room cooling capacity was escaping tioned air volume units of conditioned air volume that were escaping 4 10 10 10 through unsealed cable openings is also coming out of through unsealed cable openings and misplaced perforated tiles. that were escaping the perforated tiles properly placed in the cold Figure 2. Airflow After Sealing Raised Flooraisle. Recent research by Upsite Technologies of 45 computer 1: Typical Airflow through unsealed Figure rooms Volumes Figure 2: Airflow After Sealing Raised Floor So now a total of 10 units of cooling capacity from reveals that on average 48 percent of conditioned air is escaping cable openings is the cooling unit reaches the cold aisle, but since only from unsealed openings and misplaced perforated tiles. These also coming out of the4perforated tiles properly placed 6 units of units are needed by the efficiency and in the cold units, and therefore their IT equipment, capacity, Figure 1 illustrates statistics indicate surprisingly poor improvements in AFM a typical computer room that has total ofconditionedof coolingleave the cold aislethebypass over the aisle. So now a 10 units air volume capacity from as coolis a function of airflow volume, heat load, and the not completed raised floor open area management. Howe airflow. This simplified example shows that changing last decade. It is also clear that there is a The cooling a broader un- 10 units ofunit reaches the cold aisle, but since only return airare needed set need for unit is supplying ing cooling airflow 4 units temperature thermostatically controlled unit r derstanding of AFM fundamentals. For example, Unsealed cable openings are releasingequipment, 6 the volumeconditioned air supplied by cooling air by the IT a units of of conditioned air cooling unit return points of the units. Raising the volume leave the volume. many of the sites speed units This way to change the volume of bypass in Upsite’s research had installed either hot or cold aislevolume, and perforated tiles as bypass airflow. is the only points isexampleway to increase the cold aisle in temperaturesimplified the only shows that set total of 6 units of containhave airflow in a room. ment without completing management of the raised floor bypass efficiency and capacity of cooling units and realize cold aisles are releasing 4 volumes changing the volume of conditioned air supplied by cooling units of conditioned theis the volume of bypass airflow. The IT equipment consumes athe only way to changefull benefits of AFM efforts.airflow inopenings open area. is total of 4 units It also misunderstood that sealing cable a room. Based on field data on the amount of excess cooling capacity running in data centers, there is vast unrealized opportunity to reduce operating expenses and increase cooling capacity. At the root of the considerations is room-level bypass airflow. The data center industry is seeing a lot of emphasis on airflow management (AFM) solutions as a way to improve reliability, reduce operating costs, and increase cooling capacity. It is well known that installing grommets to seal cable openings in the raised floor and blanking panels in cabinets are best practices for eliminating hot spots and prerequisites for the efficient operation of any computer room cooling configuration. However, this fundamental step is often overlooked or unfinished before sites begin installing AFM solutions such as hot or cold aisle containment. Despite the multitude of AFM and containment solutions available today, data centers, on average, still have nearly four times the capacity they need. Therefore, the full potential benefits of these best practices remain largely unrecognized. The misconception is that managing the openings of a raised floor, or even installing full containment solutions, will eliminate bypass airflow. The truth is that while these solutions solve intake air temperature problems, and may reduce operating costs of IT cooling fans, the volume of bypass airflow in the room remains unchanged. Detecting and correcting this room-level issue lies in a broader understanding of bypass airflow. 12 of volume. In this case the volume of air supplied by perforated tiles equals the volume of air consumed by July/August 2013 IT equipment. The only bypass airflow in the room is www.ElectronicsProtectionMagazine.com air escaping from the unsealed cable openings. and other obvious sources of bypass airflow increases Many sites temperatures to cooling best practices and have implemented AFM units and cooling return air seen some or all of the following benefits: unit efficiency. Improved IT intake air temperatures As shown in the figures above, sealing the openings in Four http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - July/August 2013

Electronics Protection - July/August 2013
Newer Technology Releases Next-Generation Power2U AC/USB In Wall Charging Solution
Subzero Engineering Introduces PolarXpress DCiM SaaS Monitoring Solution
Specifiers of Enclosures for Components in Outdoor Applications: Be Aware of Material Selection Issues
Formable Phase Change Materials as Latent Heat Sinks for Portable Electronic Devices
How to Protect Electronic Circuits from Power Surges
Diamond Heat-Spreaders: Growth Methods and Applications
Standards-Based Design & Electronic Packaging Solutions
Reducing Room-Level Bypass Airflow Creates Opportunities to Improve Cooling Capacity and Operating Costs
Harnessing Laboratory Wind Tunnels
New DVR Enclosure with Prepackaged Thermoelectric Cooler
New Silver Conductive Aqueous Based Sodium Silicate System for EMI/RFI Shielding
Citizen and MechaTronix LED Cooling Cooperate On New Generation CitiLED COB’s
Eaton Expands 5P UPS Product Line to Provide Efficient Protection for Any IT Environment
Flex-Block System Puts Free-Standing Enclosures on New Footing
Gore Introduces Acoustic Vent for Protecting Electronic Devices
Industry News
Calendar of Events

Electronics Protection - July/August 2013