MIL-HDBK-1011/1
Cooling Towers. Select cooling towers on the basis of a 7 degree F
14.8.5
approach temperature. Ensure that condenser water flow is as low as possible
based on life cycle costs of fan energy versus compressor energy and
consistent with the chiller manufacturer's recommendation. Towers with long
hours of operation are of the draw-through type to reduce fan horsepower
requirements.
Provide cooling towers with an automatic blow down system and an
automatic biocide/corrosion inhibitor feed system to ensure proper water
treatment. Where adequate water treatment cannot be assured, consider using a
closed loop condenser water system (e.g., an evaporative cooler, or an air-
cooled condenser) in lieu of a cooling tower.
Mechanical Equipment
14.9
Location. Locate equipment indoors whenever possible. Roof-
14.9.1
mounted equipment is not recommended in areas prone to hurricanes and
typhoons. Additionally, roof-mounted equipment creates roof construction and
maintenance problems. Where roof-mounting is unavoidable, evaluate the cost
effectiveness of providing roof-top equipment rooms.
14.9.2
Material Selection. Use non-corrosive materials for outdoor
mechanical equipment when feasible. For example, use stainless steel,
fiberglass, or ceramic in lieu of galvanized steel for cooling towers, and
aluminum in lieu of steel for exhaust fans.
Use copper tube/aluminum fin, copper tube/copper fin, or aluminum
tube/aluminum fin evaporator and condenser coils.
Provide outdoor equipment casings and condenser coils with
additional coating protection in accordance with NFGS-15780.
14.10
Condensation Control
14.10.1
Insulation.
Prevent condensation and subsequent problems of
moisture absorption, mildew and mold formation, and corrosion, by ensuring
that all materials and equipment operating at temperatures below the maximum
ambient dewpoint temperature are properly insulated and sealed with a vapor
barrier.
14.10.2
Heat Transfer Analysis. Conduct a heat transfer analysis of the
temperature profiles through the typical wall and roof sections. Refer to
Section 7 for considerations regarding insulation selection.
14.10.3
Pine Insulation. Use cellular glass in lieu of fiberglass
insulation. Insulation thicknesses for piping specified in NFGS-15250 are
based on 85 degree F dry bulb and 85 percent relative humidity ambient air.
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