EME Newsletter MEssage #01/2023

NEWSLETTER
TECHNICAL ARTICLE
Rafael Van Eijcken
Institute (CTI), has developed a
certification program specifically for
the thermal performance of factoryassembled
open, and closed-circuit
cooling towers. These program
models consist of individual units
with published thermal rating
capacities and associated input fan
power levels.
Looking at the numbers
Let us consider a typical example
in the Middle East of an HVAC
application that operates year-round
with a load variation from 100%
in summer to 75% in winter. The
summer condition to cool 100 LPS
from 40°C to 35°C at an ambient wet
bulb temperature (WBT) of 32°C. In
this case, the cooling capacity to be
rejected would be 2093 KW.
For this scenario, the selected
cooling tower, which we can refer
to as Cooling Tower A (CT-A), will
have a length of 2585 mm, 5500
mm wide and 3653 mm high with
29 KW absorbed fan power and a 30
KW installed fan motor. The overall
sound power level of CT-A would be
104 dB(A).
Now, let us consider an undersized
model Cooling Tower B (CT-B),
which would only deliver 85% but
with a lower initial cost than CT-A.
Typically, this unit would be 15%
smaller in physical size or have
the same size as CT-A but with an
absorbed fan power of only 20.1 KW
Emmanuel Timothy
with a 22 KW installed fan motor.
The overall sound power level of
the CT-B would be 102 dB(A).
For 2093 KW, which has to be
dissipated at WBT 32°C, CT-B will
supply a 1.35°C warmer outlet
than designed. Or it will deliver
the design temperatures up to a
WBT of 30.79°C only.
For projects where undersized
cooling towers are installed, which
are also typically non-certified
cooling towers, when customers
face a shortage in capacity
and contact that cooling tower
manufacturer about the problems
faced on site, the response will
typically be that the supplied
cooling tower is “correctly
sized” and that the issue is most
probably related to poor operation
and maintenance. This risk is
taken by some manufacturers in
the belief that the customers will
not make an effort to request and/
or verify third-party certification
documents, as their main priority
is choosing a system with the
lowest initial cost. Initially, the
problems caused by an undersized
cooling tower unit might be
minimal until the project requires
its full cooling load which may
take several years. In time,
however, the problem of capacity
shortage will be aggravated and
create serious problems onsite.
Although the customer may be
misled by small power savings
on the fan motor KW for CT-B
compared to CT-A, they may not
be aware that such an undersized
cooling tower will trigger extra
work on the chiller by increased
compressor lift linked to the 1.35°C
warmer water supplied to the chiller
by CT-B. This increased compressor
work increases the chiller power
consumption significantly during a
year-round operation by more than
6%. With the chiller compressor
motor being a multiple of the CT
fan motor, this situation causes
significantly higher operational
costs for the customer.
Let us also look at the annual
economic impact the customer
will face with CT-A and CT-B if
both cooling towers use variable
frequency drives and run with a
water concentration factor of 5
cycles.
The fan kWh requirement-based
year-round operation for CT-A will
be 55,540 kWh, and for CT-B, it
will be only 50,800 kWh. However,
looking at the electrical energy
needed for the chiller, for CT-A, we
need 1,114360 kWh, but for CT-B,
the chiller requirement goes up to
1,178,700 kWh, which is 6% more.
Therefore, by adding the chiller and
fan kWh the CT-B system still needs
5% more electrical energy annually.
A typical AED 0.38 fils/kWh cost will
represent an annual operating cost
of AED 22,648.00.
In addition, CT-B will have more
water consumption, as the chiller
will need to work harder, and
therefore more waste energy is
dissipated, resulting in more water
evaporating. Ultimately, the CT-B
water consumption will be 300 m3
[65,991.00 Imperial Gals] water
more than CT-A. Considering the
water rate at AED 4.6 fils/IG (plus
the sewerage charges) this will add
approximately another AED 4,500.00
per year.
Below is a chart illustrating the
additional cost vs energy and water
costs with a 3% year-on-inflation
rate price increase.
The total operating cost difference
for water and electricity for
the system with CT-B will be
AED 27,148.00. This number is
typically near to half of the first
cost difference with CT-A. From
this, it is clear that a small price
advantage for CT-B melts away when
considering energy and water costs
Keep in mind
Thus, it is essential to remember
that value for money does not just
come by looking at the first cost and
mindlessly accepting manufacturer
documents with self-declared
thermal performance. A customer
must be able to challenge such
manufacturer declarations by
questioning whether the thermal
performance is Eurovent/CTI
certified or insist on a performance
field test (acceptance test)
according to the Eurovent/CTI
standards to confirm or verify the
declared thermal performance.
Only by insisting on a field
performance test carried out by
certified testing agencies, even
with the additional cost, will the
customer determine whether the
cooling tower can provide the listed
performance. However, suppose
the results lead to a failed test. In
that case, the customer’s misery
will just begin, as this often leads to
many unpleasant discussions with
the manufacturer, often with no final
resolution. Selecting a cooling tower
which has Eurovent / CTI Certified
Performance via either the third
party or internal lab testing ensures
the buyer before the purchase that
they will not have higher operating
costs due to underperformance.
Certified thermal performance
testing removes risk towards
system economics and removes
the guesswork. It also removes the
problems of litigation, penalties and
compensation should an already
purchased product be found to
underperform because it’s too late
by then.
Remember to look for the Eurovent
/ CTI Certified Performance mark
to ensure optimal cooling tower
selection. Eurovent includes yearly
factory certification conformity
audits of the Cooling Tower
manufacturer. At the end of the
day, purchasing a Eurovent / CTI-
Certified model ensures that the
cooling tower will perform as
specified. In all instances of thermal
certification, the purchased model,
or a model within the same line, will
have been thoroughly inspected and
tested by a Eurovent / CTI-licensed
testing agency, and customers can
rest assured that their system will
operate as intended.
www.eurovent.me SEPTEMBER JUNE 2023 2022 VOL. 01 09