POWER March 2017 - 30

WATER & WASTEWATER
2. Square-spray nozzle. Curtis Technologies has developed a nozzle with a square spray
pattern, improving the water distribution in the fill media. Courtesy: Curtis Technologies
old design sheets, and once we get our picture
in place, compare the measured efficiency
versus what the design was to let them know
where they're at and we compare everything
on the spec sheets. "
Taking the original design specifications
left dry.
To fix that problem, tower designers move
the nozzles closer, overlapping the spray.
However, that action plan still results in an
uneven water distribution, flooding the fill
media in the areas of overlap. When a part
of the fill becomes flooded, air cannot travel
through, which reduces the efficiency of the
plant.
" The quality of the air over water mixture
determines the efficiency of that heat
transfer. Of course, I think the industry has
known that forever, " Howard Curtis, inventor
of Curtis Technologies' variable flow nozzle
(VFN, Figure 2), said.
Curtis's VFN allows for an even distribution
of water and in turn, better cooling efficiency.
" We developed a nozzle that produces
a square water pattern, and it's hydraulically
balanced, so we get better water balance over
the fill media, which means you're going to
get better air to water contact, " Curtis said.
" The most economical thing you can do is to
change out your nozzles to bring sometimes
10 percent or more thermal efficiency. "
Another piece of equipment that often gets
overlooked in the search for low-hanging
fruit is the cooling tower fan, Dwyer said.
" The important part of the heat transfer is the
air movement through the fill media, " he said.
" If you can increase your airflow through the
media it really very directly impacts the heat
transfer. So, the more air, the more cooling,
the more cooling, the more efficient. If you
can take an old fan that isn't very efficient
and put a more modern design in there, you
should be able to increase your airflow and
with your increased airflow have better cooling
and better efficiency. "
Identifying the Problem
As with most things in life, the first step to
addressing a cooling tower efficiency problem
is to identify where the problem is. When
a power generator is feeling the effects of an
inefficient cooling tower, pinpointing the
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POWER | March 2017
source of the problem quickly and accurately
is vital to developing an effective game plan.
That's where companies like Quantum
Technical Services come in. The company
offers a cooling tower efficiency study performed
during peak operation to determine
the thermal operating condition of the cooling
tower. Such an audit studies the air and
water flow of the unit, an evaluation of the
heat transfer area, and infrared thermal scans
of the tower to identify any potential problems.
When
possible the company also tries to
take into account the original design of the
tower in determining if it is operating as it
was intended. " I believe this is the best thing
to do, " Paul Chila, an engineering consultant
with Quantum Technical Services, said.
" When [the tower] was built it was designed
to run under certain percent efficiency. What
we do is, wherever I can, try to dig up those
of a tower into account allows the company
to first determine if the plant is operating as
it should be, before determining how well it
could be operating. " We had one fairly recently
where ... they were so far off spec on
the flow rate being supplied to the tower that
we told them, you need to fix this problem
first, and then we can come back and reevaluate
the tower, " Chila said. " It can be a process
where you need to say, you need to address
this, this is a big factor. "
For counterflow towers, the company's
GamaScan technology can offer a helpful
picture of what is happening inside the fill
material. " GamaScan takes a look literally
through the fill, and it gives us a density profile, "
Chila said. " From that, we can tell if
the film fill is being fouled and if it is fouling
fairly uniform across the cell. That alone,
just by the amount of fouling that we have
the ability to measure, that's obviously going
to affect the efficiency of how that tower is
performing. "
Regularly assessing cooling tower performance,
no matter how old or new equipment
may be, allows the operator to determine if
their treatment programs are working. " I've
got quite a few that are the newer style-with
the film fill-that were built within the last
two to three years, and they just brought us
out and said, 'Come and get the baseline,' "
Chila
said.
Establishing such a
baseline
3. Some assembly required. SPX Cooling Technologies' NC Everest factory assembled
cooling tower can be shipped to a power generator in just a few pieces, requiring minimal
field assembly. Courtesy: SPX Cooling Technologies

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POWER March 2017

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