a device that dissipates industrial heat without
dumping it directly into rivers or lakes
||At left is a
"wet," natural-draft, counterflow
tower. Hot water from the plant is exposed to air
moving up through the chimney-like tower. Heat is
removed by evaporation and the cooled water is
emptied into a waterway or recirculated through
the plant. In cold areas water vapor discharged
into the atmosphere can create a heavy fog.
At right is a Tennessee Valley Authority
power plant on the Green River in Kentucky that
was, in 1969, the world's largest coal-fueled
electric plant. Its three wet, natural-draft
cooling towers, each 437 feet in height and 320
feet in diameter at ground level, had a capacity
of 282,000 gallons a minute, which they could
cool through a range of 27.5 degrees.
||A "dry" cooling
tower (left) avoids evaporation. The hot water is
channeled through tubing that is exposed to an
air flow, and gives up its heat to the air
without evaporating. In this mechanical-draft
version air is moved through the tower by a fan.
Dry towers are costly to operate.
five-cell cooling towers seen at right were built
by the Marley Company for a chemical plant. They
are wet, mechanical-draft towers of the
cross-flow type: a fan in each stack draws air in
through the louvers, across films of falling
water and then up. The towers cool 120,000
gallons a minute through a 20-degree range.
John R. Clark, "Thermal Pollution and Aquatic
Life" Scientific American
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