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Air-Dale Engineering Seeley International
heat quickly enough to bring the indoor temperature down to the
desired temperature. As the cooled air is delivered into the building,
it immediately begins to heat up again until it reaches the exhaust
point where it should not have heated above the set temperature.
Therefore, depending on the heat-load and the set temperature, a
calculation must be made for the number of air changes required,”
says Toomey.
If the correct and full heat-load calculation has been made, the total
volume of air required will be established, and from that the correct
number of coolers required to satisfy the heat-load (kW). Of the total
volume of air required, at least 90% must also be exhausted from the
building. This will help in removing the heat load sufficiently and at the
same time keep a positive pressure in the building.
GENERAL ADVANTAGES
While evaporative cooling may have some disadvantages, there are
many advantages associated with this method, including:
• Lower initial capital cost for both supply and installation –
depending on the application and selection, this saving could be as
much as 40%.
• Lower power consumption. Evaporative cooling is said to be the
most cost-effective method of cooling.
• Lower maintenance and spares costs – the expertise level required
to service/repair these evaporative coolers is not as high as airconditioning
as the evaporative coolers referenced in the article
have very few moving parts – a water pump and a fan motor.
By establishing the heat load of a space correctly you are able to
determine the number of coolers required per application.
An installation in a vehicle holding warehouse.
• Where many refrigerated systems have a coefficient of
performance (COP) of 3-4, some evaporative systems can have
COP of around 12 or more, this can only be achieved when using
evaporative cooling systems that have been efficiently designed
and tested at approved test facilities.
• Longer lifespan – The polymer plastic casings and structure on
some of the units on the market have a lifespan in excess of 10
years, when maintained properly.
• Unlike air-conditioning that recycles the same air, albeit with some
fresh air, evaporative cooling will provide 100% fresh air with a
constant air temperature supply. This also plays a major role in the
management of heat load in a space as already mentioned.
• Healthy natural way of cooling air which adds to the green building
concept as well as reducing the carbon footprint on the world due
to lower power consumptions.
AIR QUALITY AND ‘BUILDING HEALTH’
Air quality is a whole new area of testing that hasn’t typically required
any verifications or certifications previously, so the testing that is
performed with evaporative cooling currently is more about fan
curves, performances and efficiency – there hasn’t been specific
testing around this element as yet, but having said that, scientists
all over the world are all currently looking into air quality and the
association with airborne pathogens.
I would assume little dispute in natural ventilation so the fact that a
physical changeover of the air inside a building happens about 35 times
in an hour speaks for itself – you don’t have to do anything to prove that
other than the evidence that the product is in fact delivering this amount
of air changes.
There has been wide recognition that Covid-19 is transmitted via
aerosol form which is essentially scientifically different to droplet form
and therefore the management thereof must follow an adjusted strategy.
“To add to this, more and more evidence has been revealed that
spreading of the virus is taking place indoors and in areas of poor
ventilation. Conventional air conditioning with the recirculation of air
with aerosol contamination is said to be causing what is now referred
to as ‘super-spreader environments’. But indoor air quality and what is
known as building health is not only linked to Covid-19,” says Karovsky.
At the time of publishing, South Africa is heading into the summer
months and as you would expect – everyone will be reaching for the
remotes to ensure comfort conditions, closing windows and doors,
which is in fact creating the environment that you don’t want when
dealing with the current pandemic.
In President Cyril Ramaphosa’s address to the nation in July 2020,
he stated: “We must immediately improve the indoor environment of
public places where the risk of infection is greatest. We must increase
natural ventilation, avoid the recirculation of air and minimise the
number of people sharing the same space. We must do this in all health
care facilities, nursing homes, shops, offices, workplaces, schools,
restaurants, and public transport.”
Evaporative cooling not only provides fresh cool air, it also provides
a humidification effect, and various worldwide organisations, including
ASHRAE, state that one of the controlling factors in Covid-19 and other
similar viruses and pathogens can be managed though the combination
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RACA Journal I October 2020
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