Civil Engineering Reference
In-Depth Information
Fig. 8.4
Self-contained water-cooled system
atmosphere through cooling tower. Cooling tower receives this water through the
condenser water pipes and pumps. There is no need for a separate chiller, and nei-
ther there is a need for chilled water pumps in this arrangement. Supply fan delivers
a variable air volume to the terminal units and return/exhaust fan modulate simulta-
neously with the supply air to provide the desired air balance in the building.
The main energy consumers in the system are supply fan power input, return fan
(if it is provided) power input, compressor power input, cooling tower fan, con-
denser water pumps and terminal units fan power input. Heat transfer through the
ducts and duct air leakage also contribute to energy consumption (waste) in this
system. There is always electrical power consumption for heat tracing the water
piping outside the heated mechanical rooms, and protecting the cooling tower basins
from freezing.
The small energy consumed by low-voltage power provided for control valves is
another source of energy consumption.
8.9
Packaged Terminal Air Conditioner
A separate Packaged Terminal Air Conditioner (PTAC) including a fan, fi lter, direct
expansion cooling coil, and hot water/electric heating coil/strip if it is needed is
located in each room. The unit supplies a constant volume of conditioned air to the
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