Engineered Systems - January 2009 - (Page 52) Chilled Beams UW Medicine Phase 2: Chilled beam operation Chilled beams at the UW Medicine Phase 2 project were configured to respond to the organization of the laboratory space with two 7-ft sections of beams located directly above the lab benches and a smaller 4-ft section mounted parallel to the outside wall. The beams mounted over the bench were positioned to effectively capture the heat plume from the bench-mounted equipment. A “one-way” throw beam was utilized to throw air toward the center of the aisle (a two-way throw configuration would have directed air into the storage boxes usually located on the top shelf of the lab benches). A one-way throw beam was also utilized at the exterior wall to provide adequate heat for the laboratory technicians with desk space at the exterior wall. Considerable CFD modeling and mock-up support was directed at this area during the design phases to ensure that comfort conditions were maintained without the need for baseboard convectors. Primary air for the beams is provided through the central air-handling system serving the remainder of the building. This system delivers 55°F “primary” air to the beams through constant volume pressure independent supply air valves. The primary air is zoned to serve up to three laboratory modules. In some areas of the building, chilled beams were not deployed for a variety of reasons: • In many office areas the first cost of the beams relative to the potential energy benefit was minimal. • One portion of a lab floor is slated for future chemistry research with associated high fume hood density that is not compatible with chilled beam installations. • Other areas contained programs such as glass wash where high humidity levels increased the risk of condensation. In these areas, standard VAV and constant volume control approaches were used. Heat for the labs is provided by reheat coils associated with the supply valve. A tempered water system provides cooling capacity to the coils in the chilled beam. The water is controlled to a temperature of 58° to optimize the capacity of the coil and prevent condensation from occurring on the coil surface. Redundant safety controls are incorporated into the tempered water system to ensure that colder water is not delivered to the beams, potentially causing condensation. FIGURE 5: UW Medicine Phase 2 finished lab with chilled beam placement directly above the lab benches. (Photo courtesy of Ben Benschneider.) CRITICAL TESTING APPLIED TO UW MEDICINE PHASE 2 As the building function became better defined early in the design process, it became clear that for much of the UW Medicine Phase 2 facility, building heat gain, rather than fume ventilation, would be the primary determinant of peak airflow rates, thus making the project a prime candidate for the application of active chilled-beam technology. Through an extensive series of discussions, presentations, and analyses, the design team — which included the University of Washington, Vulcan Inc., and architects Perkins+Will — adopted the use of the technology. As the design progressed, AEI and the team performed additional CFD analyses and full-scale mock-ups in the beam manufacturer’s thermal test facility to customize and fine-tune the proposed design, ultimately establishing further efficiencies in the technology, resulting in a reduction of capital costs. OUTCOMES AND BENCHMARKING Completed in August 2008, the UW Medicine Phase 2 is among the largest laboratory applications of chilled beam technology in the world. While the potential for energy savings would be more pronounced in a climate less temperate than Seattle’s, the qualitative impact and overall sustainable design benefits to the facility are significant. The reduction in system support space requirements increases the net square footage of useable space, resulting in a greater degree of daylighting, and more pleasingly spacious labs. Lab spaces also benefit from lower ambient sound levels and greater uniformity of temperature and air movement. UW Medicine Phase 2 is adjacent to the first phase of the School of Medicine’s South Lake Union Campus, the adaptive reuse of Seattle’s locally known “Blue Flame” Building. The lab spaces and functions in the two buildings are closely comparable, though where UW Medicine Phase 2 employs chilled-beam technology, Phase 1 uses a more conventional VAV HVAC system. This offers ideal circumstances for ongoing benchmarking of chilled beam technology, of great interest to the A/E/C field as well as the beam’s manufacturers. ES McMahon is the managing principal of Affiliated Engineers, Inc.’s Seattle office. 52 En gi neer ed S y stem s January 2009
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.