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By Daniel Nall, PE, AIA and Michael Eskra, Flack and Kurtz Inc., New York, NY
The William Jefferson Clinton
Presidential Center is located on
the south bank of the Arkansas
River just east of downtown Little Rock,
Arkansas. The main feature of the center
is the Bridge Building. This building
houses the Presidential Museum,
which is a public exhibition gallery
and museum space. Nearby is the
Archive Building, which contains the
National Archive and Records
Administration Facilities including
storage vaults and office space for
researchers.
The museum space that is housed in the Bridge Building occupies a dramatic,
double-height space that contains exhibits chronicling the tenure of the
former President. The lower level consists of a series of permanent interactive
exhibits. The upper level is open to the lower level in the middle with
more exhibits around the perimeter of the space. The west wall of the
space is a full-height glass wall, while the east wall is opaque.
The geometry of the interior of the exhibit space
Temperature contours on a slice through both levels
Since many of the exhibits have
large cooling loads due to specialty
lighting and interactive display
equipment, the design objective for
the space was to create a stratified
layer of air with conditions in the
human thermal comfort range in the
lower level. The heat would then
rise through the middle of the upper
level to a return at the ceiling. To
accomplish this, several different methods
of conditioning the space were
utilized. On the lower level, displacement
air distribution was provided
using linear slot diffusers
along the west perimeter and in front
of the exhibits on the east and west
sides. This air was supplied in the occupied
areas at design conditions while
unoccupied areas along the perimeter
were supplied at 55°F. On the
upper level it was not possible to use
underfloor distribution due to the structure
of the second floor, so overhead
air supplies were used. This air was
supplied at 55°F from jet diffusers located
over the open area. On both levels,
a radiant floor was used to create
a warm thermal mass in the winter
and to help to absorb the space solar
load in the summer.
Since so many different systems
were being used to condition the
space, simulations in Airpak were performed
by Flack and Kurtz to study
the interaction of the various systems.
Flack and Kurtz has successfully engineered
and implemented many
advanced green construction technologies
in a variety of applications,
using capabilities that include computational
fluid dynamics, advanced
energy modeling, and lighting
analysis.
The simulation results showed that
during the summer months, the space
could be maintained at the desired
thermal conditions. The displacement
distribution created a layer of cooler
air that fills the occupied area and
forces the warmer air to rise up the
middle. The upper-level overhead supply
flow pushes across the catwalks
and picks up heat given off by the
exhibits before rising along the exhibit
walls and circulating back to the
return vents. Throughout the entire
space, the air flow is assisted by the
contributions of the radiant floor system.
The CFD analysis was used to
determine the optimum operating
conditions for the air flow systems
during regular occupancy, and to verify
the ventilation effectiveness in support
of a LEED™ (Leadership in Energy
& Environmental Design) credit.
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