Projects
manifold, before the clean air stream is sound attenuated and
exhausted to atmosphere.
The concrete laboratories include five climate rooms where
samples are cured in heated water baths. These rooms are air
conditioned via dedicated chilled water fan coil units located
outside the rooms to avoid continuous exposure of systems and
controls to high room moisture levels. The coils are therefore also
selected with high latent cooling abilities in order to dehumidify
the air sufficiently when needed. The fan coil units are located
above the concrete slab over the rooms, within an access
floor void level which serves as a mezzanine floor to a series of
offices above the laboratories. The units remain accessible for
maintenance and are also visible via selected access floor tiles
being transparent to keep with the exposed services theme. The
offices are in turn served by further fan coil units above, creating
yet another level of services.
Two special humidity and creep test rooms in the concrete
laboratories present interesting psychrometric design and
control challenges. The rooms are used to test concrete samples
at specific and continuously controlled relative humidity and
temperature levels of up to 95% relative humidity and 25°C
dry-bulb temperature simultaneously. Each room was specified
to be fully internally insulated with cold room panels, sealable
and provided with floor drainage. A dedicated air handling unit
located externally serves each room, with supply and return air
recirculated via externally insulated ducting and special internally
insulated air terminal plenums to avoid condensate issues inside
ducting as far as possible.
Each room is provided with two in-room steam humidifiers.
Air flow, cooling coil, heating capacity and steam supply volumes
were psychrometrically designed to supply a high air change
rate at high supply air temperature to improve controllability
and minimise diffuser face condensation. With multiple and
interdependent parameters of dry-bulb temperature, wet-bulb
temperature and vapour pressure and the design condition
requiring a room that is essentially always on the limit of full
moisture saturation, the control requirements and variables
had to be carefully planned to avoid oversaturation or over- and
under-cooling. Similarly, control loop commissioning had to be
fine-tuned to ensure sufficient dampening and stability.
The facility foyer space is a large multi-volume area served by
two air handling units equipped with coils sufficient for full fresh
air tempering but designed with return air and economy cycle
functionality in order to minimise energy usage when ambient
conditions are favourable. Exposed spiral duct networks were
coordinated to suit the building’s curved shape and exposed
34
RACA Journal I August 2020
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