Feature
EFFICIENT, COST-EFFECTIVE
AND HEALTHY FLOWS WITH
EVAPORATIVE COOLING
Compiled by Benjamin Brits
With patents recorded as far back as the early 1900s, the concept of this
cooling mechanism was in fact developed in ancient times and used in Egypt
and Persia by collecting and passing air over a subterranean water source.
Naturally, a lot has changed since then. There has been great
development in all forms of technology and ducting related to
the evaporative cooling process, and the result of this cooling-type
today, is an enhanced way of delivering on nature.
“Evaporative cooling essentially works on the natural way of cooling
air by taking outside air and passing it through cooling pads into a space
while at the same time adding humidification and pushing out relief air.
This creates a constant inflow of freshly-cooled air and you can keep
windows, doors and louvres open to allow this relief air to get out.
“Generally speaking, with evaporative cooling you would change
the air in the particular space around 30 times per hour – so essentially
bringing in new air and removing the stale air. The air change rate can
also vary depending on the varying circumstances. This concept of
cooling is therefore different to conventional air-conditioning which
relies on air recirculation to get to the temperature required,” says
Stuart Karovsky, general manager at Air-Dale Engineering (Cool Breeze
Airconditioning SA).
In the past, evaporative coolers were made locally by various
companies and utilised in some retail stores in South Africa. These
steel-casing units were generally installed on the back wall with a
centrifugal fan blowing air directly into the space through a hole in the
wall, and a single deflection grille.
“This design type was not ideal as the noise and air velocities
associated with this type of installation were generally not acceptable,
resulting in tenants or users limiting the use of their units as a result
of the noise and discomfort associated with the high air velocities.
But then, about 30 years ago, a new concept of unitary single stage
evaporative cooling products arrived from Australia with an improved
through-roof design and installation,” says Rodney Marillier, owner of
Raptor Engineering (Aolan Evaporative Cooling Systems).
Rather than installing the units on the back wall and blowing air
directly into the space at unacceptable velocities, the new design
unit came in a down-discharge configuration utilising a dropper duct
to penetrate the roof, and introducing air into the space via flexible
ducting and ceiling-mounted multi-directional outlets that are
commonly still be seen today.
This type of installation was a marked improvement over the
previous method in that the noise levels were greatly reduced and
Raptor Engineering (Aolan)
3
Quality installations of evaporative coolers remains essential so as to not
affect a roof’s performance or structural integrity.
air distribution was improved with acceptable air velocities. While this
type of unit design is used predominantly for residential applications
in Australia, the same types of units are used for various applications
in Southern Africa.
“It is unfortunate that in the past, poor installations by some
contractors resulted in owners, landlords and designers not being keen
on evaporative coolers, or allowing their roofs to be penetrated and
damaged as a result of poor workmanship– that in turn affected how
designers and engineers perceived the product,” says Marillier.
APPLICATION AND SELECTION
Evaporative cooling can be applied as a solution in almost all settings
including agriculture, residential, commercial, industrial, retail, sports
facilities and stadiums.
The effectiveness of evaporative cooling depends on the correct
selection which is based on a number of factors such as the average
dry & wet bulb (Db and Wb) temperatures for the particular region,
or location.
“This particular factor dictates what the achievable supply air
temperature is, which, in turn, will dictate how many units or what air
volume will be required for a given space – the lower the achievable
Continued on page 21
www.hvacronline.co.za RACA Journal I October 2020 19