MIL-HDBK-1003/3
associated maintenance costs. Condenser heat can also be
recovered for space heating including reheat and domestic water
b) Evaporative Condenser. An evaporative condenser
yields high efficiency because of its low condensing temperature,
and is smaller than an air-cooled condenser or cooling tower.
Although the evaporative condenser is often mounted on the roof,
it may be mounted inside the building and ducted to the outside.
It requires less maintenance than a cooling tower because the
water treatment is easier. Provide capacity control by cycling
the fan, using a two speed fan and modulating dampers. Use a dry
sump piped to an inside reservoir in freezing climates.
c)
Cooling Tower. A cooling tower also yields high
efficiency with its low condensing temperature. It can be
designed to give "free" cooling (e.g., cooling when the
refrigeration compressor motor is not running) with special
piping or using a special refrigeration compressor. Continuous
bleed off is required to prevent excessive concentration of
solids. Chemical treatment is used to inhibit microorganisms,
control corrosion and scale, and to keep silt in suspension.
Locate cooling towers to prevent short circuit of moist air; and
so that drift from the tower will not water spot parked cars,
large windowed areas, or sensitive architectural surfaces.
Locate the condenser water pump below or alongside the tower
basin to ensure an adequate NPSH. Heat the basin or use a dry
sump and remote reservoir in freezing climates. Provide capacity
control by cycling the fan.
d) Air Cooled Condenser. Because an air cooled
condenser is governed by the outdoor air dry bulb temperature, it
has higher condensing temperature and a lower energy efficiency
than an evaporative condenser or cooling tower installation.
Maintenance costs and labor requirements are much lower with air
cooled condensers than with cooling towers or evaporative
condensers.
e) Ground-Loop (Geothermal) Heat Rejection. Use where
justified by life cycle cost evaluation and ecological
considerations and where space permits. Improved methods of
welding plastic pipe provide long-lasting systems (25 years) with
minimum maintenance requirements.
2.2.4
Ventilation Equipment
9
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