| Application ConsiderationsFigure
A-17 — Stacked Energy Recovery Unit with Total Energy Recovery Wheel
Energy Recovery Module
This custom module houses an energy-recovery device
that, depending on ambient conditions, uses the exhaust air stream to precondition (warm or cool/dehumidify) entering outdoor
air. Following are three energy- recovery methods for
use in Modular Climate Changer applications.
Total-Energy Wheel.
(Figure A-17) This energy-recovery
device consists of a rotating wheel coated with a
desiccant medium suited for total energy transfer.
Adjacent outdoor and exhaust air streams pass through the wheel in a counterflow
arrangement, exchanging sensible energy through thermal
conduction and latent energy through moisture adsorption and desorption. Along with
its ability to recover both sensible and latent energy,
the total- energy wheel’s advantages include its
compact size and reliable, mature technology. Application considerations:
- Recovery effectiveness typically ranges from 68 to 86 percent.
- The total-energy wheel may contribute an additional 0.7 to 0.9 in. wg to system static pressure.
- This method of energy recovery is particularly well-suited to dehumidification
cooling applications with low sensible heat ratios.
Run-Around Loop.
(Figure A-18) A run- around
loop consists of two finned-tube coils (air-to-water
heat exchangers) piped together; one coil resides in the outdoor air stream and the other in the exhaust air stream. An expansion
tank, pump, three-way temperature control valve and
working fluid (usually an inhibited solution of ethylene glycol and water) complete the recovery system.
Figure
A-18 — Typical Run-around Energy Recovery Loop
Since the outdoor and exhaust air streams need not be adjacent, the run- around
loop provides design flexibility well-suited to
building renovations — at a lower first cost than
other methods of energy recovery. Complete separation of the air streams also eliminates the risk of cross- contamination.
Application considerations:
- Recovery is limited to sensible energy with an effectiveness that typically ranges from 60 to 65 percent.
- Together, the two finned-tube coils may contribute approximately 0.3 to 0.6 in. wg to system static pressure.
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