Reymsa HFC Series - Air Pollution; Corrosion; Make-Up Water Requirements; Table C-4: Cycle of Concentration

REYMSA COOLING TOWERS, INC.
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C.3.4. CORROSION
Corrosion is a process of metal dissolution usually by oxidation; this process provokes degradation on the
metal surface, creating pits or even holes on it. Corrosion of system components shortens its life, reducing
operational reliability. However, since REYMSA Closed Circuit Fluid Coolers are constructed of FRP, corrosion
is not an issue for the tower, but it is for the system and the copper coils.
C.3.5. AIR POLLUTION
A Closed Circuit Fluid Cooler draws air as a part of its operation, it can attract a variety of particles on it,
interfering with its performance. Do not locate the unit close to smoke stacks, discharge ducts, vents or gas
ue exhausts.
C.4 MAKE-UP WATER REQUIREMENTS
Make-up water is added to compensate for the volume of water lost throughout evaporation, drift and
blowdown. Evaporation accounts for the largest loss of water from a water cooling system and is independent
of system’s ow for typical operating temperatures. To achieve one ton of cooling, a Tower will evaporate
about 1% of process water each minute, per every 10°F range.
As this water evaporates, it leaves behind any dissolved solids it may have been carrying. If allowed to
go unchecked, these solids will eventually precipitate out or scale the heat transfer surfaces. To aid in
controlling dissolved solids a portion of the process water must be discharged from the system and replaced
by fresh make up water thus diluting the remaining process water. Blow-down or bleed are common names
given to this discharge.
Determining the amount of blow-down required is heavily inuenced by the quality of water used for make
up. As the dissolved solids content of the make up water increases the need for higher blow-down rates
will also increase. Cycles of concentration are used in establishing the blow-down rate. The value of the
cycles of concentration is the ratio between the process water concentration of dissolved solids and the
make up water concentration of dissolved solids. A chemical analysis by a water treatment professional is
the recommended method for determining the optimum cycles of concentration for the cooling Tower water.
Water is also lost from the cooling Tower itself in the form of liquid droplets, which become entrained in the
cooling Tower air stream and discharged with it. Known as drift, the amount of water blown out of the Tower
is dependent on the Tower’s eliminators and the ow through the Tower. Generally 0.001% of the Tower
ow rate may be used as an estimate for drift in a counter-ow Tower.
In Table C-4, there is an example which may be used for estimating water usage in a typical fully loaded
system, with a 10°F temperature drop through the Tower. Flows are represented as a percentage of the
total ow through the Closed Circuit Fluid Cooler.
CYCLES OF
CONCENTRATION (CC)
EVAPORATION DRIFT PURGE MAKE-UP
2 1.0% 0.001% 0.999% 2.0%
3 1.0% 0.001% 0.499% 1.5%
Table: C-4 Cycles of concentration
% PURGE =
% EVAPORATION - % DRIFT
CYCLES OF CONCENTRATION - 1
Operation