and internal piping.
House all components in a common casing.
2.2.1.1
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NOTE: Shell-and-tube design generally achieves 55
to 60 percent efficiency; and the flat-plate, cross
flow air-to-air design generally achieves 65 to 85
percent efficiency. Cooling tower coil design may
be the most efficient method of all three choices,
generally used in industrial areas where the outdoor
wet bulb temperature is 7 degrees C 45 degrees F or
below. This third design can maintain space
conditions similar to those achieved with mechanical
refrigeration.
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a.
Shell-And-Tube Design: Fabricate tubes and tube sheets from
[galvanized steel] [stainless steel] [aluminum] [polystyrene] [or]
[copper]. Tube interiors shall be bonded with an epoxy coated
crystalline surface or equivalent. Protect tube sheets with a
bituminous coating applied after fabrication. Provide the
interior of heat exchanger enclosure with 25 mm one inch thick
neoprene-coated fiberglass or equivalent insulation.
b.
Flat Plate, Cross-Flow Air-To-Air, Design: Fabricate the heat
exchanger of [aluminum] [stainless steel] [galvanized steel] [or]
[copper] with a water absorbent coating applied to the secondary
or wet air surface.
c.
Cooling Tower Coil Design: Transport chilled water from the
direct evaporative cooler, and circulate this chilled water
through a cooling coil fabricated of copper tubing expanded into
aluminum fins.
2.2.1.2
Evaporative Media
Self-cleaning evaporative media capable of withstanding a maximum air face
velocity of 3.56 m/s 700 fpm without moisture carryover. Construct media
of refined cellulose fibers impregnated with insoluble anti-rot salts and
rigidifying saturants.
2.2.1.3
Recirculating Pump
Submersible pump with epoxy-coated cast-iron housing, corrosive resistant
base and cover, non-clog impeller, screened intake, and permanently
lubricated motor with thermal overload protection.
2.2.1.4
Secondary Air Exhaust Fan
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NOTE: Propeller fan wheels usually have two or more
single thickness blades in a single ring enclosure.
Forward curved centrifugal fan wheels have small and
curved forward blades in the direction of the
wheel's rotation. The wheel type of such
centrifugal fans is often called "squirrel cage
wheel." Both fans run at a relatively low speed to
move a given amount of air. Use propeller fans
SECTION 15721N
Page 9
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