Engineered Systems - June 2008 - (Page 57)

State Of The Arts FIGURE 1. Artist’s rendering of the west façade of the Valley Performing Arts Center main lobby. tainable concepts. Part of the sustainable design strategy for the heating water plant included the installation of two hydrogen fuel cells that provide clean electricity to the campus grid. A byproduct of operating fuel cells is a substantial amount of heat that can either be wasted, or, as is the case at this campus, recovered and put to good use. The full heating and domestic hot water load of the new performing arts center is provided by heat recovery from the fuel cells. Any remaining heat is used in other buildings attached to the central hot water plant. This allows the campus to keep buildings warm without having to engage their large gas-fired boilers for a majority of the year. Another university requirement for the performing arts center was that the use of both the chilled and hot water in the building had to be billed separately for campus and touring theater uses. To accomplish this, a network of six thermal energy meters was installed in each system. The campus facilities staff will know exactly which portions of the building are using how much energy, and when it’s being used. While this level of monitoring required a $50,000 to $60,000 capital outlay, it is expected to have a simple payback period of less than five years, since it gives facilities staff the ability to trend performance and optimize the operation of the building systems. DESIGNING FOR SUCCESS Attaching to the central plant was only the beginning of the design process for the performing arts facility. Extensive analysis was performed in the design of the 1,600-seat concert hall and lobby. FIGURE 2. CFD result of the tunnel air distribution system under the auditorium. In the early stages of the conceptual design, it was decided that the concert hall would be designed using a displacement ventilation system with supply air coming out of floor-mounted registers under the occupants’ seats. To deliver supply air to the floor outlets, there are two primary options for a slab-on-grade theater: either buried ductwork or concrete tunnels. With the substantial rake of the seating in the hall, and the required depth of the foundation system for the orchestra pit, the design was steered toward using concrete tunnels, primarily as a method of controlling costs. Unlike traditional overhead ventilation schemes, which have established rules of thumb and published design guidelines, displacement ventilation systems had not often been used in concert halls in the United States at the time of the design of this facility. In order to be confident in the design, the mechanical engineering team utilized computational fluid dynamics (CFD) modeling to simulate varying auditorium occupancies and operating scenarios. CFD software allows a user to create a 3-D model of a space that will yield a highly accurate representation of its performance before it is built. Simply put, you can use the software to not only help design complicated HVAC systems but to troubleshoot them before construction begins. The distribution network is built in concrete, using the building foundations as part of the duct system. The tunnel network followed the stepping of the foundation walls around the orchestra pit, resulting in an arrangement that was too complex to use normal design assumptions. Instead, the tunnel network was modeled in 3-D and input into the CFD software to determine its performance. Velocity, temperature, and pressure profiles for the entire supply network were developed under varying load and occupancy conditions. Figure 2 shows a plan view of CFD velocity results for the main auditorium floor supply tunnels and under floor plenum. The final design is a pair of nearly symmetrical tunnels that flanks the sides of the auditorium. The two tunnels discharge into large plenums underneath the main cross aisle in the center of the auditorium. From there, air is routed through smaller air channels and into sub-compartments underneath the seating sections. The entire network of compartments under the seats was designed using CFD in order to maintain even pressure, temperature, and velocity distributions to each of the seating areas so that the auditorium would be uniformly comfortable throughout. Openings in the walls between compartments were sized using CFD modeling to ensure that no compartment had a velocity in excess of w w w. esmag a zin e. c o m 57 http://www.esmagazine.com

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Engineered Systems - June 2008 Contents Editor’s Note Letters To The Editor Back2Basics HVAC Challenge Case In Point Commissioning Efficiency Incentives HydroTech Building Automation Energy Wiz HVACR Designer Tips Notre Dame Tackles the Heat State Of The Arts Time For A Transplant? Project Delivery: What Can IPD Do For You? Issues & Events Computers & Software Products Application Checklist Glossary Classifieds Advertiser Index Tomorrow’s Engineer

Engineered Systems - June 2008

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