Engineered Systems - January 2009 - (Page 50) Chilled Beams heat from a space. Mounted in an enclosure at the ceiling, a passive beam is essentially a chilled water coil that is able to generate air movement and cooling through convective currents created by warmer air rising in a space and colder air falling. Active beams are similar but have supply air ducted directly to them to increase the airflow through the device, thereby increasing its cooling capacity. In essence, these devices transfer heat to and from the laboratory spaces by using a combination of water and air as transfer mediums. Given the greater physical capacity of water to move heat per unit volume relative to air, significantly smaller conduits are required than in a typical all-air system. AND APPLIED TO THE RESEARCH LAB The use of chilled beams in the laboratory environment provides opportunities to address many of the construction and operation challenges associated with these facilities, most prominently the need for large air-handling systems and ductwork and the substantial energy costs associated with laboratory facilities. Typical laboratories can have peak airflow rates in excess of 15 ach. Delivering this amount of air with a conventional air-handling system can drive the floor-to-floor height for these buildings to 15 to 16 ft (compared to 12 to 13 ft for a typical office building). The use of active chilled beams can reduce peak airflows to 6 ach or below, thus significantly reducing the size of equipment and ductwork, allowing the building to realize capital cost savings associated with a lower floor-to-floor height and significantly smaller mechanical rooms. Significant energy savings can also accrue through the application of this technology. Due to the use of chemicals in the lab and the potential for cross contamination between laboratory spaces impacting critical research, laboratories do not recirculate air, as is common in most other environments. The reduction in air change rates noted above can significantly reduce the energy profile of a laboratory building. This can be particularly significant in areas that have prolonged periods of high heat and humidity. While other benefits such as lower noise, ease of control, and reduced filter maintenance all contribute to making this technology viable for use in the laboratory environment, it is not appropriate for every lab. Labs in which the size of the air-handling system is determined by the need to replace exhaust air from exhaust devices such as fume hoods are not appropriate for the use of this technology. However, equipment-intensive labs in which the air-handling system is sized based on the need to dissipate generated heat are prime candidates for chilled-beam technology. CRITICAL TESTING OF CHILLED BEAM TECHNOLOGY Prior to the announcement of the UW Medicine Phase 2 project, Affiliated Engineers, Inc. (AEI) had teamed with the National Institutes of Health through their Sustainable Design Initiative to identify ways to decrease energy use in the laboratory environment. With chilled beams identified as a promising technology, AEI developed a relationship with a major European chilled beam manufacturer to test several configurations of chilled beams in laboratories. Through a full-sized mockup process and extensive computational fluid dynamics (CFD) analyses, one variation of chilled-beam design was determined to optimize performance relative to benchtop loads while also accommodating maintenance access and the modular layout inherent in laboratory design today. FIGURE 2: Active chilled beam installation. Note smaller-sized conduits. (Photo courtesy of John Edwards.) FIGURE 3: Active chilled beam with the airflow increased by direct ducting of supply air. (AEI Illustration.) FIGURE 4. Active chilled beam airflow pattern. (AEI Illustration.) 50 En gi neer ed S y stem s January 2009
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