ASHRAE Journal - September 2024 - 36

TECHNICAL FEATURE
FIGURE 3 Isometric view of the auditorium showing the location of the supply and return air outlets and
a " zoom view " of the supply air diffusers showing below the seat.
all while working to achieve comfortable
conditions in compliance with ASHRAE
Standard 55-2023.
2x Supply Diffuser Bar
Total Area = 8.07 ft2
Total Flow = 2,652 cfm
Projector
Room
2x Supply Diffuser Bar
Total Area = 8.07 ft2
Total Flow = 530 cfm
2x Retrun Box
Total Area = 32 ft2
Total Flow =13,080 cfm
Isometric View
296x Supply
Duct Opening
Total Flow =
11,840 cfm
Zoom View of Supply Through Plenum
(1054 kW) air-cooled water chillers, providing a total
of 1,200 tons (4220 kW), of cooling. The chilled water
plant delivers chilled water to the AHUs, fan coil
units and blower coil units that serve the building at
a temperature of 42.5°F [6°C], through four primary
constant flow and four secondary chilled water pumps
with variable frequency drives.
A centralized building automation system (BAS) is
incorporated to control the building HVAC, lighting and
other systems through a building management system
(BMS). The objectives of the BAS are improved occupant
comfort, efficient operation of the building systems,
reduction in energy consumption and operating costs
and improved life-cycle costs of utilities.
Construction Challenge
The construction of the auditorium posed a great
challenge to the design and construction team, as no
structure of this magnitude and shape had previously
been constructed in Beirut, Lebanon; moreover, no
other facility of this scale had previously implemented
displacement ventilation as a main ventilation principle.
This was far from traditional auditorium ventilation,
which uses supply ducts and grilles located on the upper
part of the auditorium and uses dilution principles.
Other challenges emerged during the construction
phase, which were due to the ongoing modifications
imposed by the architect in light of the seemingly
endless improvement needed for this iconic structure,
36
ASHRAE JOURNAL ashrae.org S E PTEM B ER 2024
Location of Returns
Returns are usually located as high as possible in
the space to remove as much of the stratified zone as
possible, typically at ceiling height. If the return is
located lower than 7 ft (2 m), some polluted/hot air
may remain within the occupied zone. Despite the fact
that in our case the return air grilles are lower than 7 ft
(2 m), the introduction of a substantial quantity of fresh
air helped avoid the contamination of the occupied
space with polluted/hot air. The return air grilles are
evenly and symmetrically distributed at the entrance
in the back side of the auditorium at a level 3.3 ft (1 m)
above the entrance floor level and 10 ft (3 m) above
Computer simulation with the aid of CFD
and full-scale test model allowed optimizing
the location of the air outlets, specifically
maintaining one diffusion grille beneath
every seat, all while maintaining acceptable
terminal velocities and noise levels. Close
coordination with architects and structural
engineers was required to create openings
in the precast concrete slab for air supply
beneath each seat, making it entirely
integrated and invisible. Another challenge
that emerged as a consequence of low air
speeds and higher supply temperatures
associated with displacement ventilation
was how to efficiently cool the main stage
area without affecting the displacement ventilation
design. The design team proposed installing two supply
diffuser bars above the main stage area (Figure 3).
72 ft
Top View
Supply Air Connections
Displacement ventilation diffusers are usually
supplied by ductwork, and they can be supplied from
either above or below. In our case, supply displacement
ventilation diffusers are connected to a pressurized
concrete plenum under seats (airtight concrete
chamber) where the pressures and airflow rate are
equal. This was made possible by installing constant
flow balancing dampers in each sub-branch serving the
plenum. The selection of step diffuser was based on a
supply air velocity of 39 fpm (0.2 m/s).
Screen
Entrance
Zoom View
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ASHRAE Journal - September 2024

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