ASHRAE Journal - September 2013 - 26

Technical FeaTure

floor, considered as separate conFigure 4 Recovery with glycol.
trol areas for chemical storage
Glycol Coil
and usage, travels up a dedicated
Exhaust Stack
Bleed Air
shaft to the roof of the building.
Additionally, a bleed damper on
ERU
Roof
the hazardous exhaust system, or
alternately a variable geometry
Cooling/De-Humid Coil
Pre-Conditioning Glycol Coil
Wraparound
discharge damper (VGDD), works
Glycol Coil
in combination with a variable air
(Neutral Air
H System Only)
P
C
volume system in order to maintain
From
C
stack velocity.
C
C
Outside Air
• Figure 2a (Page 22) represents the
Louver
AHU
components of the air-handling sysSupply
Manifolded Exhaust
tem with the first energy recovery
Dedicated Shafts for Each Floor Area
method (wheels) in combination
Supply
with the first air-handling system
Manifolded Exhaust
type (traditional approach) under
peak summer operation.
Shaft Bottom (typ)
Fire/Smoke Dampers (typ)
• Figure 2b (Page 22) represents the
same combination under peak winter operation.
• Figure 3a (Page 24) represents the components of type (neutral air supply, using dual recovery, with supplethe air-handling system with the first energy recov- mental cooling devices) under peak summer operation.
ery method (wheels) in combination with the second
• Figure 6b represents the same combination under
air-handling system type (neutral air supply, using peak winter operation.
dual recovery, with supplemental cooling units in the
Test Model
spaces), under peak summer operation.
The test model consists of 40,000 ft2 (3700 m2) of
• Figure 3b (Page 24) represents the same combination
usable space in a Northeast climate with a summer outunder peak winter operation.
side air design temperature of 92°F (33°C) DB and 76°F
The second energy recovery method using glycol
(24°C) WB, and a winter outdoor design temperature of
(hydronic) is illustrated in Figure 4. As seen in this figure,
0°F (–17°C). This space breaks down as follows:
general exhaust and hazardous exhaust are combined
• 20,000 ft2 (1800 m2) of laboratory space;
in the same ducts and pass through the glycol recovery
• 6,500 ft2 (600 m2) of office, conference, and adminsystem. The energy recovery unit (ERU) is located on the
istrative areas;
roof in order to achieve code compliance for hazardous
• 8,500 ft2 (790 m2) of lobby and circulation areas;
exhaust. Once again, a bleed damper or VGDD is used on
• 2,500 ft2 (232 m2) of toilet rooms; and
the exhaust side in combination with a variable air vol• 2,500 ft2 (232 m2) of support and mechanical/electriume system.
• Figure 5a represents the components of the air-han- cal space not including the penthouse.
The laboratory areas are a mix of hood-intensive chemdling system with the second energy recovery method
(glycol) in combination with the first air-handling sys- istry-type labs and less intensive biology-type labs. The
tem type (traditional approach) under peak summer op- total required airflow for a traditional air-handling system was calculated at approximately 85,000 cfm (40 100
eration.
• Figure 5b represents the same combination under L/s), and about 75,000 cfm (35 400 L/s) for a neutral airhandling system with dual recovery. The airflow quantity
peak winter operation.
• Figure 6a represents the components of the air-han- is reduced in the latter case due to the use of supplemendling system with the second energy recovery method (gly- tal cooling devices, reducing airflow to the load driven
col) in combination with the second air-handling system areas.2
26

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ASHRAE Journal - September 2013

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