12
1. Do not allow the tower’s leaving water temperature to drop
below a minimum allowable level (2.5° to 5°C) established as
follows:
During the coldest days of the first season of operation, observe whether
any ice is forming on the louver face, particularly near the bottom of the
louver face. If hard ice is present on the louvers, an appropriate eleva-
tion in the allowable cold water temperature is mandatory. If the coldest
possible water is beneficial to your process, ice of a mushy consistency
can be tolerated—but routine periodic observation is advisable.
If the minimum allowable cold water temperature is established at or
near maximum heat load, it should be safe for all operating conditions.
However, if established at reduced load, increased heat loads may
reintroduce the potential for icing.
Having established the minimum allowable cold water temperature,
maintaining that temperature can be accomplished by fan manipulation,
as outlined in Item 4 under Tower Operation on page 10.
However,
in towers of more than one cell, the limiting temperature established
applies to the water temperature of the cell or cells operating at the
highest fan speed—not necessarily the net cold water temperature
produced by the entire tower.
2. As cold air enters the louvers, it causes the falling water to be drawn
inward toward the center of the tower. Thus, under fan operation,
the louvers and lower periphery of the tower structure remain partly
dry, seeing only random splashing from within the tower—plus normal
atmospheric moisture from the entering air. Such lightly wetted areas
are most subject to freezing.
Although ice is unlikely to cause structural damage to the fill, it may
build up sufficiently to restrict the free flow of air through the louvers.
This will have the effect of reducing the tower’s thermal performance
efficiency. When excessive ice forms on the louvers, stop the fan for
a few minutes. With the fan off, the increase in the water temperature
and the action of the cascading water will reduce the ice buildup on
the louvers.
operation
