Engineered Systems - October 2008 - (Page 44)

Chilled Beams In Chicago Threaded support rod Support bracket Primary air duct collar Return air nozzles 2 Entrainment chamber Primary air plenum Primary air duct collar 1 Water coil 4 Retun air grille T Room sensor 6 Contol valve Mixed primary air/induced air tempered at coil 5 Supply water Return water Induced room air 3 Posko Associates Inc. June 2008 FIGURE 1. A cutaway diagram of the active chilled-beam system. FIGURE 2. An active chilled beam system allows 250 South Wacker Drive in Chicago to use 40% of the air volume of a standard system. Two central AHUs supply primary air (conditioned and dehumidified outside air) to the offices through the ceiling chilled-beam units. The primary air induces room air to be re-circulated through the coil of the chilled beam. Room air temperature is controlled by the water flow rate through the coil. Active chilled-beam systems may be an ideal green solution for many buildings. They easily meet the energy-efficiency requirements of the Federal Energy Policy Act of 2005. The design supports sustainability since the central air-handling system circulates only the amount of air needed for ventilation and latent loads. The active chilled beams provide the additional air movement and sensible heating/cooling required through the induced room air- and unitmounted secondary water coil. Thus, as compared to all air systems, primary air volumes are dramatically reduced. Indeed, the building system in 250 South Wacker uses 40% of the air volume of a standard system. The chilled-beam system transfers the majority of heating and cooling loads from the air distribution system to the water distribution system. This is because the use of the water distribution system for the majority of heating and cooling loads is more efficient than the use of the air distribution system. The result is that the chilled-beam system uses less energy with lower operating costs. Remember, the chilled water return and hot water return flows become the supply flows to the chilled-beam secondary coil. So, maximum use of the energy generated by central plant is transferred to the building. 44 En gi neer ed S y stem s October 2008

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Engineered Systems - October 2008 Contents Editor’s Note Letters Back2Basics HVAC Challenge Case in Point Commissioning Building Automation HydroTech HVACR Designer Tips Special Insert: Engineer's Technical Library Fall 2008 Living Wild! Chilled Beams in Chicago Phoenix Convention Center: On The Rise Cold-Climate HVAC Challenges Humidification Strategies For Data Centers & Network Rooms Special Advertising Supplement: Tabb Talk Computers & Software Issues & Events Products Literature & Catalogs Glossary Classifieds Advertiser Index Tomorrow’s Environment

Engineered Systems - October 2008

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